AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1255 PM EST TUE DEC 20 2005 .AVIATION/UPDATE... UPDATE ISSUED AS WEDGE OF SLIGHTLY WARMER LOW LEVEL TEMPS ADVECTING IN ACROSS SOUTHERN GREAT LAKES. UPSTREM TEMPS ALREADY IN THE MID 20S OVER SNOWPACK IN NORTHERN IL. WILL NOT GO THAT WARM BUT TREND OUT OF TEENS GIVEN FAIRLY RAPID WARMING PAST COUPLE OF HOURS. ALSO INCREASED CLOUD GRADIENT WITH SYNOPTIC AND LAKE ENHANCED 925MB MOISTURE ACROSS MI BEGINNING A SLOW SOUTHWARD PUSH. LOW END MVFR CIGS AT KSBN AND AT LEAST A 50 PERCENT CHANCE BRIEFLY LATER THIS AFTERNOON/EVENING AT KFWA WITH LOW LEVEL WINDS A BIT MORE VEERED PER WLCI3 LOWEST GATE AND NAM12 TIMEHIEGHT THROUGH 03Z. THEN WINDS BACK AND DRIER AIR ACROSS IA MOVES IN AND SHOULD KEEP TAFS VFR THROUGH REMAINDER OF FCST PD. && .SHORT TERM... TODAY AND TONIGHT... DIFFICULT FORECAST WITH RESPECT TO CLOUD COVER FOR TODAY AND TONIGHT AND THE IMPACTS ON TEMPERATURES. SATELLITE SHOWS ELONGATED BAND OF LOW CLOUDS ACROSS NORTHERN MICHIGAN AND WISCONSIN MOVING STEADILY SOUTH. ANOTHER AREA OF CLOUDS EXISTS ACROSS WESTERN MO AND SOUTHERN IA MOVING STEADILY EAST. A THIRD AREA WHICH IS LAKE EFFECT CLOUDS HAS DEVELOPED EAST OF LAKE MICHIGAN. 850MB RH ON THE 06Z RUN OF THE NAM40 SEEMS TO HAVE THE NORTHERN AND WESTERN CLOUD AREAS HANDLED WELL WHILE 925MB RH IS TRYING TO HANDLE THE LAKE EFFECT CLOUDS. RUC20 DOING A LITTLE BETTER JOB WITH THE LAKE CLOUDS BUT IT APPEARS OVERDONE WITH THE EXTENT AND DEVELOPMENT NEXT FEW HOURS. GENERALLY FOLLOWING THE LATEST NAM40 RH FOR CLOUD COVER FORECAST BUT MUCH UNCERTAINTY DUE TO DRIER AIR BEING SQUEEZED BETWEEN THE SYNOPTIC SYSTEMS AND MARGINAL DELTA T VALUES AND MOISTURE FOR THE LAKE EFFECT CLOUDS. WILL HAVE NORTHERN AREAS BEGINNING PARTLY TO MOSTLY CLOUDY WITH LAKE CLOUDS THEN INCREASING SKY COVER FROM NORTH TO SOUTH THIS AFTERNOON DUE TO COMBINATION OF NORTHERN SYSTEM SINKING SOUTH AND WESTERN SYSTEM APPROACHING. NAM40 SHOWING THESE AREAS TO ONLY GLANCE OUR AREA AND SHOWS DRYING LATER TONIGHT. WILL KEEP NORTHERN AREAS MOSTLY CLOUDY AND CONTINUE TO TREND SOUTHERN AREAS PARTLY CLOUDY TONIGHT. MOS GUIDANCE SHOWING HIGHS IN MID 20S TODAY DESPITE ONLY A COUPLE DEGREES OF WARMING AT 925MB AND 850MB FROM MONDAY VALUES. MOS WAS 10 TO 15 DEGREES TOO WARM ON MONDAY WITH FULL SUNSHINE. 00Z MOS WAS VERIFYING ABOUT 5 DEGREES TOO WARM AT 06Z. STRUGGLING TO SEE A 15 TO 20 DEGREE WARM UP TODAY WITH SIMILAR CONDITIONS TO MONDAY AND POTENTIAL FOR AFTERNOON CLOUDS. HAVE DROPPED MAX TEMPS SEVERAL DEGREES TODAY. CONCERN FOR ANOTHER BIG DROP IN TEMPS TONIGHT AS HIGH PRESSURE MOVES BY TO THE SOUTH AND WINDS IN SOUTHERN FORECAST AREA LOOK TO DECOUPLE MORE THAN THIS MORNING. DESPITE WARMER TEMPS ALOFT...INVERSION AND RADIATIONAL COOLING MAY ALLOW FOR ANOTHER NIGHT OF VERY COLD TEMPERATURES IF SKIES ARE CLEAR. HAVE DROPPED TEMPS A FEW MORE DEGREES TONIGHT...ESPECIALLY IN THE SOUTH...BUT HAVE BEEN A BIT CONSERVATIVE GIVEN POSSIBILITY OF LINGERING CLOUDS. && .LONG TERM... WEDNESDAY THROUGH MONDAY THE FIRST HALF OF THE MEDIUM RANGE PERIOD THE MAIN STORY WILL BE A BONAFIDE WARM UP WITH A SEVERAL DAY STRETCH OF ABOVE FREEZING HIGH TEMPERATURES LIKELY FOR THE SECOND HALF OF THE WEEK INTO AT LEAST THE FIRST HALF OF THE WEEKEND. THIS WILL BEGIN TO MELT OUR EXISTING SNOWPACK AS WE APPROACH CHRISTMAS DAY. SEVERAL NORTHERN STREAM SHORTWAVES WILL DROP SOUTHEAST INTO NEW ENGLAND THROUGH MIDWEEK AND RE-ENFORCE THE MEAN TROUGH POSITION NOW CENTERED OVER SOUTHEAST CANADA. ONE SIGNIFICANT SHORTWAVE WEDNESDAY WILL SWEEP AN ATTENDANT COLD FRONT ACROSS THE NORTHERN AND EASTERN GREAT LAKES. ALL NUMERICAL GUIDANCE KEEPS ANY SIGNIFICANT MASS CONVERGENCE AND CAA WELL NORTH AND EAST OF OUR REGION WITH THIS SYSTEM. WILL CONTINUE WITH A DRY FORECAST. THURSDAY AND FRIDAY THE SIGNIFICANT WARMING TREND GETS UNDERWAY IN EARNEST AS A POWERFUL PACIFIC JET CONTINUES TO BEAT DOWN THE WEST COAST RIDGE. THE PATTERN ACROSS THE CONUS WILL QUICKLY TREND TO ZONAL AND ALLOW PACIFIC AIR...FURTHER MODIFIED BY A CHINOOK...TO FLOOD EAST ACROSS THE NATION. WILL KEEP THIS PERIOD DRY AS WELL WITH ANY ORGANIZED ISENTROPIC LIFT AND DEEPER MOISTURE REMAINING WELL NORTH OF THE CWA. HAVE ADJUSTED TEMPERATURES SIGNIFICANTLY UPWARD FOR THURSDAY AND FRIDAY WITH ALL AVAILABLE GUIDANCE NOW ON BOARD WITH THE STRONG WARM SIGNAL. THE DEEP SNOWPACK ACROSS THE REGION WILL TEMPER THE WARMUP SOMEWHAT...BUT STILL EXPECT TEMPS WELL INTO THE UPPER 30S BY FRIDAY WITH A DISTINCT POSSIBILITY OF 40+F READINGS. WILL PLAY CONSERVATIVE FOR NOW WITH MID TO UPPER 30S AND WATCH FUTURE MODEL TRENDS. THE PERIOD OF ZONAL FLOW WILL BE SHORT LIVED HOWEVER. AN INTENSE NEGATIVE HEIGHT ANOMALY WHICH HAS PERSISTED OVER THE WESTERN GULF OF ALASKA AND THE ALEUTIANS WILL QUICKLY RELOAD BY NEXT WEEKEND AND TRIGGER SIGNIFICANT DOWNSTREAM AMPLIFICATION. A RIDGE WILL AGAIN BEGIN TO DEVELOP ALONG THE WEST COAST OF NOAM BY SATURDAY WITH PACIFIC SHORTWAVES QUICKLY CARVING OUT A DEVELOPING TROUGH OVER THE CENTRAL PLAINS. GFS/ECMWF/GEM ALL IN REASONABLE AGREEMENT ON THE BASIC IDEA OF A DEEPENING TROUGH TRANSLATING SLOWLY ACROSS THE MIDWEST OVER THE WEEKEND AND REACHING THE EASTERN SEABOARD BY SUN OR MON. ALL THREE MEDIUM RANGE MODELS ALSO SUGGEST SECONDARY SHORTWAVE ENERGY DIVING DOWN THE WESTERN PERIPHERY OF THE DEVELOPING TROUGH AND SPAWNING ADDITIONAL SURFACE DEVELOPMENT. AS EXPECTED...WHILE MODEL GUIDANCE IS IN GOOD OVERALL AGREEMENT ON THE MEAN H5 PATTERN...SIGNIFICANT RUN TO RUN DISCONTINUITY AND MODEL TO MODEL DISAGREEMENT EXISTS WITH RESPECT TO TIMING AND DEVELOPMENT OF SURFACE FEATURES. FOR NOW THE BEST PLAN OF ACTION IS TO RETAIN CONTINUITY WITH CHANCE POPS FOR RA/SN SAT THEN CHANCE FOR SNOW SAT NGT AND SUN AS TROUGH DEEPENS AND COLDER AIR RETURNS. STILL MUCH TO EARLY TO SPECULATE ON DETAILS OF THIS SYSTEM. BEYOND THE WEEKEND SYSTEM MEDIUM RANGE GUIDANCE DIVERGES SIGNIFICANTLY WITH RESPECT TO THE MEAN LARGE SCALE PATTERN ACROSS NOAM. THE 12Z/19 ECMWF ALONG WITH PREVIOUS RUNS OF THE GFS INCLUDING THE 12Z/19 ITERATION SHOWED THE +PNA PATTERN QUICKLY RE-DEVELOPING NEXT WEEK WITH SIGNIFICANT WESTERN NOAM RIDGE AND EASTERN NOAM TROUGH LOCKING IN. FURTHERMORE...SOME OF THE RECENT GFS RUNS HAVE ALSO DEVELOPED A STRONG -NAO TYPE PATTERN IN THE 6 TO 10 DAY RANGE WITH STRONG POSITIVE HEIGHT ANOMALIES OVER THE NORTH ATLANTIC. THE 00Z/20 GFS HAS BACKED OFF FROM THIS SOLUTION AND SHOWS ONLY TRANSIENT SHORTWAVES DROPPING THROUGH THE GREAT LAKES. A LOOK AT THE DAVA MODEL RUN AT CPC...A COURSE BAROTROPIC MODEL WHICH IS DESIGNED TO FORECAST THE LONGWAVE PATTERN AS OPPOSED TO SYNOPTIC SCALE WEATHER SYSTEMS...DOES LEND SUPPORT TO A MEAN EASTERN NOAM TROUGH BECOMING RE-ESTABLISHED WITH A NEGATIVE H5 HEIGHT ANOMALY CENTERED OVER THE SOUTHEAST CONUS. GIVEN THE PROPENSITY OF THIS PATTERN TO QUICKLY RE-ESTABLISH THE PAST MONTH...AND THE EXPECTED CONTINUATION OF THE INTENSE NEGATIVE HEIGHT ANOMALY OVER THE ALEUTIANS...AM LEANING TOWARD THE MORE AMPLIFIED SOLUTIONS AT THIS TIME. THIS WILL MEAN GOING DECIDEDLY BELOW MEX GUIDANCE SUN AND MON WITH TEMPS INITIALLY RETURNING TO AT OR SLIGHTLY BELOW NORMAL. CHANCES FOR A RETURN TO MUCH BELOW NORMAL TEMPERATURES WILL INCREASE BEYOND DAY 7. WILL KEEP SUN NGT AND MON DRY FOR NOW GIVEN MODEL UNCERTAINTY. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR LMZ043- LMZ046. && $$ SHORT TERM...MURPHY LONG TERM....HITCHCOCK AVIATION...MURPHY in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 632 AM EST TUE DEC 20 2005 .AVIATION... LAKE EFFECT CLOUDS STREAMING SOUTHEAST OFF OF LAKE MICHIGAN BUT MISSING TAF SITES JUST TO THE NORTH. AS SHORT WAVE DROPS SOUTH TODAY...EXPECT SOUTHERN EDGE OF CLOUDS TO SLOWLY SINK SOUTH AND MOVE INTO KSBN LATER THIS MORNING AND FINALLY INTO KFWA LATER THIS AFTERNOON. DRIER AIR WORKS IN OVERNIGHT TO HELP SCOUR CLOUDS OUT. && .SHORT TERM... TODAY AND TONIGHT... DIFFICULT FORECAST WITH RESPECT TO CLOUD COVER FOR TODAY AND TONIGHT AND THE IMPACTS ON TEMPERATURES. SATELLITE SHOWS ELONGATED BAND OF LOW CLOUDS ACROSS NORTHERN MICHIGAN AND WISCONSIN MOVING STEADILY SOUTH. ANOTHER AREA OF CLOUDS EXISTS ACROSS WESTERN MO AND SOUTHERN IA MOVING STEADILY EAST. A THIRD AREA WHICH IS LAKE EFFECT CLOUDS HAS DEVELOPED EAST OF LAKE MICHIGAN. 850MB RH ON THE 06Z RUN OF THE NAM40 SEEMS TO HAVE THE NORTHERN AND WESTERN CLOUD AREAS HANDLED WELL WHILE 925MB RH IS TRYING TO HANDLE THE LAKE EFFECT CLOUDS. RUC20 DOING A LITTLE BETTER JOB WITH THE LAKE CLOUDS BUT IT APPEARS OVERDONE WITH THE EXTENT AND DEVELOPMENT NEXT FEW HOURS. GENERALLY FOLLOWING THE LATEST NAM40 RH FOR CLOUD COVER FORECAST BUT MUCH UNCERTAINTY DUE TO DRIER AIR BEING SQUEEZED BETWEEN THE SYNOPTIC SYSTEMS AND MARGINAL DELTA T VALUES AND MOISTURE FOR THE LAKE EFFECT CLOUDS. WILL HAVE NORTHERN AREAS BEGINNING PARTLY TO MOSTLY CLOUDY WITH LAKE CLOUDS THEN INCREASING SKY COVER FROM NORTH TO SOUTH THIS AFTERNOON DUE TO COMBINATION OF NORTHERN SYSTEM SINKING SOUTH AND WESTERN SYSTEM APPROACHING. NAM40 SHOWING THESE AREAS TO ONLY GLANCE OUR AREA AND SHOWS DRYING LATER TONIGHT. WILL KEEP NORTHERN AREAS MOSTLY CLOUDY AND CONTINUE TO TREND SOUTHERN AREAS PARTLY CLOUDY TONIGHT. MOS GUIDANCE SHOWING HIGHS IN MID 20S TODAY DESPITE ONLY A COUPLE DEGREES OF WARMING AT 925MB AND 850MB FROM MONDAY VALUES. MOS WAS 10 TO 15 DEGREES TOO WARM ON MONDAY WITH FULL SUNSHINE. 00Z MOS WAS VERIFYING ABOUT 5 DEGREES TOO WARM AT 06Z. STRUGGLING TO SEE A 15 TO 20 DEGREE WARM UP TODAY WITH SIMILAR CONDITIONS TO MONDAY AND POTENTIAL FOR AFTERNOON CLOUDS. HAVE DROPPED MAX TEMPS SEVERAL DEGREES TODAY. CONCERN FOR ANOTHER BIG DROP IN TEMPS TONIGHT AS HIGH PRESSURE MOVES BY TO THE SOUTH AND WINDS IN SOUTHERN FORECAST AREA LOOK TO DECOUPLE MORE THAN THIS MORNING. DESPITE WARMER TEMPS ALOFT...INVERSION AND RADIATIONAL COOLING MAY ALLOW FOR ANOTHER NIGHT OF VERY COLD TEMPERATURES IF SKIES ARE CLEAR. HAVE DROPPED TEMPS A FEW MORE DEGREES TONIGHT...ESPECIALLY IN THE SOUTH...BUT HAVE BEEN A BIT CONSERVATIVE GIVEN POSSIBILITY OF LINGERING CLOUDS. && .LONG TERM... WEDNESDAY THROUGH MONDAY THE FIRST HALF OF THE MEDIUM RANGE PERIOD THE MAIN STORY WILL BE A BONAFIDE WARM UP WITH A SEVERAL DAY STRETCH OF ABOVE FREEZING HIGH TEMPERATURES LIKELY FOR THE SECOND HALF OF THE WEEK INTO AT LEAST THE FIRST HALF OF THE WEEKEND. THIS WILL BEGIN TO MELT OUR EXISTING SNOWPACK AS WE APPROACH CHRISTMAS DAY. SEVERAL NORTHERN STREAM SHORTWAVES WILL DROP SOUTHEAST INTO NEW ENGLAND THROUGH MIDWEEK AND RE-ENFORCE THE MEAN TROUGH POSITION NOW CENTERED OVER SOUTHEAST CANADA. ONE SIGNIFICANT SHORTWAVE WEDNESDAY WILL SWEEP AN ATTENDANT COLD FRONT ACROSS THE NORTHERN AND EASTERN GREAT LAKES. ALL NUMERICAL GUIDANCE KEEPS ANY SIGNIFICANT MASS CONVERGENCE AND CAA WELL NORTH AND EAST OF OUR REGION WITH THIS SYSTEM. WILL CONTINUE WITH A DRY FORECAST. THURSDAY AND FRIDAY THE SIGNIFICANT WARMING TREND GETS UNDERWAY IN EARNEST AS A POWERFUL PACIFIC JET CONTINUES TO BEAT DOWN THE WEST COAST RIDGE. THE PATTERN ACROSS THE CONUS WILL QUICKLY TREND TO ZONAL AND ALLOW PACIFIC AIR...FURTHER MODIFIED BY A CHINOOK...TO FLOOD EAST ACROSS THE NATION. WILL KEEP THIS PERIOD DRY AS WELL WITH ANY ORGANIZED ISENTROPIC LIFT AND DEEPER MOISTURE REMAINING WELL NORTH OF THE CWA. HAVE ADJUSTED TEMPERATURES SIGNIFICANTLY UPWARD FOR THURSDAY AND FRIDAY WITH ALL AVAILABLE GUIDANCE NOW ON BOARD WITH THE STRONG WARM SIGNAL. THE DEEP SNOWPACK ACROSS THE REGION WILL TEMPER THE WARMUP SOMEWHAT...BUT STILL EXPECT TEMPS WELL INTO THE UPPER 30S BY FRIDAY WITH A DISTINCT POSSIBILITY OF 40+F READINGS. WILL PLAY CONSERVATIVE FOR NOW WITH MID TO UPPER 30S AND WATCH FUTURE MODEL TRENDS. THE PERIOD OF ZONAL FLOW WILL BE SHORT LIVED HOWEVER. AN INTENSE NEGATIVE HEIGHT ANOMALY WHICH HAS PERSISTED OVER THE WESTERN GULF OF ALASKA AND THE ALEUTIANS WILL QUICKLY RELOAD BY NEXT WEEKEND AND TRIGGER SIGNIFICANT DOWNSTREAM AMPLIFICATION. A RIDGE WILL AGAIN BEGIN TO DEVELOP ALONG THE WEST COAST OF NOAM BY SATURDAY WITH PACIFIC SHORTWAVES QUICKLY CARVING OUT A DEVELOPING TROUGH OVER THE CENTRAL PLAINS. GFS/ECMWF/GEM ALL IN REASONABLE AGREEMENT ON THE BASIC IDEA OF A DEEPENING TROUGH TRANSLATING SLOWLY ACROSS THE MIDWEST OVER THE WEEKEND AND REACHING THE EASTERN SEABOARD BY SUN OR MON. ALL THREE MEDIUM RANGE MODELS ALSO SUGGEST SECONDARY SHORTWAVE ENERGY DIVING DOWN THE WESTERN PERIPHERY OF THE DEVELOPING TROUGH AND SPAWNING ADDITIONAL SURFACE DEVELOPMENT. AS EXPECTED...WHILE MODEL GUIDANCE IS IN GOOD OVERALL AGREEMENT ON THE MEAN H5 PATTERN...SIGNIFICANT RUN TO RUN DISCONTINUITY AND MODEL TO MODEL DISAGREEMENT EXISTS WITH RESPECT TO TIMING AND DEVELOPMENT OF SURFACE FEATURES. FOR NOW THE BEST PLAN OF ACTION IS TO RETAIN CONTINUITY WITH CHANCE POPS FOR RA/SN SAT THEN CHANCE FOR SNOW SAT NGT AND SUN AS TROUGH DEEPENS AND COLDER AIR RETURNS. STILL MUCH TO EARLY TO SPECULATE ON DETAILS OF THIS SYSTEM. BEYOND THE WEEKEND SYSTEM MEDIUM RANGE GUIDANCE DIVERGES SIGNIFICANTLY WITH RESPECT TO THE MEAN LARGE SCALE PATTERN ACROSS NOAM. THE 12Z/19 ECMWF ALONG WITH PREVIOUS RUNS OF THE GFS INCLUDING THE 12Z/19 ITERATION SHOWED THE +PNA PATTERN QUICKLY RE-DEVELOPING NEXT WEEK WITH SIGNIFICANT WESTERN NOAM RIDGE AND EASTERN NOAM TROUGH LOCKING IN. FURTHERMORE...SOME OF THE RECENT GFS RUNS HAVE ALSO DEVELOPED A STRONG -NAO TYPE PATTERN IN THE 6 TO 10 DAY RANGE WITH STRONG POSITIVE HEIGHT ANOMALIES OVER THE NORTH ATLANTIC. THE 00Z/20 GFS HAS BACKED OFF FROM THIS SOLUTION AND SHOWS ONLY TRANSIENT SHORTWAVES DROPPING THROUGH THE GREAT LAKES. A LOOK AT THE DAVA MODEL RUN AT CPC...A COURSE BAROTROPIC MODEL WHICH IS DESIGNED TO FORECAST THE LONGWAVE PATTERN AS OPPOSED TO SYNOPTIC SCALE WEATHER SYSTEMS...DOES LEND SUPPORT TO A MEAN EASTERN NOAM TROUGH BECOMING RE-ESTABLISHED WITH A NEGATIVE H5 HEIGHT ANOMALY CENTERED OVER THE SOUTHEAST CONUS. GIVEN THE PROPENSITY OF THIS PATTERN TO QUICKLY RE-ESTABLISH THE PAST MONTH...AND THE EXPECTED CONTINUATION OF THE INTENSE NEGATIVE HEIGHT ANOMALY OVER THE ALEUTIANS...AM LEANING TOWARD THE MORE AMPLIFIED SOLUTIONS AT THIS TIME. THIS WILL MEAN GOING DECIDEDLY BELOW MEX GUIDANCE SUN AND MON WITH TEMPS INITIALLY RETURNING TO AT OR SLIGHTLY BELOW NORMAL. CHANCES FOR A RETURN TO MUCH BELOW NORMAL TEMPERATURES WILL INCREASE BEYOND DAY 7. WILL KEEP SUN NGT AND MON DRY FOR NOW GIVEN MODEL UNCERTAINTY. && .AVIATION... LAKE EFFECT CLOUDS HAVE REDEVELOPED WITH WESTERLY FLOW AND MARGINAL DELTA T VALUES. TRAJECTORIES SUGGEST THESE CLOUDS MAY SKIRT KSBN OVERNIGHT AND THROUGH TOMORROW. SATELLITE SHOWS THE CLOUDS JUST TO THE NORTH OF AIRPORT AND WILL LIKELY SEE A BROKEN DECK FROM TIME TO TIME. NAM AND GFS BOTH INCREASE LOW LEVEL MOISTURE DURING THE DAY AT KSBN. WITH LOW LEVEL FLOW REMAINING OFF OF LAKE MICHIGAN...LAKE EFFECT CLOUDS ARE POSSIBLE DESPITE WARMING 850MB TEMPS. HAVE OPTED FOR A BROKEN VFR DECK AS A COMPROMISE AT KSBN. STRATUS ASSOCIATED WITH NEXT SHORT WAVE NEAR LAKE SUPERIOR AND MOVING SOUTH. THESE CLOUDS SHOULD JUST SKIRT THE TAF SITES TONIGHT SO HAVE BROUGHT MVFR CLOUDS INTO KSBN AND VFR TO KFWA AFTER 00Z. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR LMZ043- LMZ046. && $$ SHORT TERM...LASHLEY LONG TERM....HITCHCOCK AVIATION...LASHLEY in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WICHITA KS 824 PM CST TUE DEC 20 2005 .UPDATE... MAIN CONCERN FOR AVIATION USERS TONIGHT WILL BE THE POTENTIAL FOR DENSE FREEZING FOG TONIGHT. WE MADE SEVERAL CALLS TO COUNTIES BEHIND THE STRATUS DECK AND THEY ARE ALREADY REPORTING DENSE FOG. LATEST FOG IMAGERY SHOWING THE LOW CLOUD PROGRESSION COMING TO A HALT OVER THE AREA. AFTER EXAMINING THE RUC 275K THETA SURFACE THERE IS VERY LITTLE IN THE WAY OF DOWNGLIDE TAKING PLACE ACROSS CENTRAL AND SOUTH CENTRAL KANSAS. THE RUC/ETA ARE BOTH SHOWING THIS TREND CONTINUING OVERNIGHT. WITH THAT IN MIND... WE WENT AHEAD AND ISSUED A DENSE FOG FREEZING FOG ADVISORY FOR ALL OF CENTRAL AND SOUTH CENTRAL KANSAS. I WOULD EXPECT THE FOG TO BUILD EAST AS THE NIGHT PROGRESSES AS CEILINGS CONTINUE TO LOWER ACROSS SOUTH CENTRAL KANSAS...DUE TO THE STRATUS BUILD DOWN EFFECT. COX && .PREV DISCUSSION... /ISSUED 604 PM CST TUE DEC 20 2005/ AVIATION... MAIN CONCERN FOR AVIATION USERS TONIGHT WILL BE THE POTENTIAL FOR LOW INSTRUMENT FLIGHT RATING CONDITIONS TONIGHT. LATEST FOG IMAGERY SHOWING THE LOW CLOUDS SLOWLY PUSHING EAST. AFTER EXAMINING THE RUC 275K THETA SURFACE THERE IS VERY LITTLE IN THE WAY OF DOWNGLIDE TAKING PLACE ACROSS SOUTH CENTRAL KANSAS. THE RUC/ETA ARE BOTH SHOWING THIS TREND CONTINUING THROUGH THE EVENING. WITH THAT IN MIND... WE ARE GETTING CONCERNED ABOUT THE LOW CLOUD DECK SLOWING DOWN ITS PROGRESSION WHICH WOULD BRING FORTH THE RISK OF DENSE FOG DEVELOPMENT WITHIN THE REGION THAT HAS CEILINGS BELOW 1KFT. ANOTHER CONCERN IS THE AREA JUST BEHIND THIS LOW CLOUD DECK WHERE THE BOUNDARY LAYER IS STILL RATHER SATURATED. THIS AREA IS MAINLY CONFINED TO JUST ALONG AND EAST OF A HUTCHINSON TO SALINA LINE TO AREAS ALONG AND WEST OF A WINFIELD TO EMPORIA LINE. THE AREAS WHERE THE CEILINGS ARE BELOW 1KFT HAVE A PRETTY GOOD SHOT OF SEEING STRATUS BUILD DOWN DUE TO SNOW COVER AND POTENTIAL FOR FOG TOP COOLING FROM CLEAR SKIES ABOVE THE STRATUS DECK. MEANWHILE... AREAS JUST BEHIND THE CLEARING LINE MAY HAVE THE POTENTIAL FOR MORE SHALLOW PATCHY DENSE FOG... DUE TO MORE DEPOSITION AND SUBSIDENCE. WE WILL CONTINUE TO MONITOR THE PROGRESSION OF THE LOW CLOUDS FOR NOW AND POSSIBLY ISSUE A HEADLINE DURING THE NEXT COUPLE OF HOURS. TIMING OF THE DENSE FOG COULD BE LATE THIS EVENING OR JUST AFTER MIDNIGHT. && COX && PREV DISCUSSION... /ISSUED 319 PM CST TUE DEC 20 2005/ DISCUSSION... FORECAST CONCERN/CHALLENGE IS LOW CLOUDS AND FOG POTENTIAL TONIGHT. THEREAFTER, EXTENT AND MAGNITUDE OF POTENTIALLY SIGNIFICANT WARMING TREND WILL BE THE MAIN FOCUS. TONIGHT: LOW STRATUS HAS BEEN MUCH SLOWER TO CLEAR OUT THAN EXPECTED, AND THIS TREND SHOULD CONTINUE TONIGHT. WEAK LOW-LEVEL TROUGH WILL PROGRESS SOUTHEAST ACROSS THE CWA TONIGHT, HELPING TO CLEAR THE CLOUDS FROM NORTHWEST TO SOUTHEAST THROUGH THE OVERNIGHT HOURS. THINKING FOG POTENTIAL WILL BE GREATEST JUST BEHIND THE CLEARING LINE OVER SNOW COVER, WHERE DEWPOINTS SHOULD BE HIGHER AND RADIATIONAL COOLING GREATEST. LATEST LAPS SOUNDINGS INDICATE FAIRLY DEEP LOW-LEVEL MOISTURE ACROSS THE EASTERN 2/3 OF THE CWA, SO ENOUGH MOISTURE SHOULD BE PRESENT FOR FOG EVEN AFTER FULL RADIATIONAL COOLING/DRYING. ONLY POTENTIAL MITIGATING FACTOR WILL BE LIGHT WESTERLY DOWNSLOPE FLOW, SO DID NOT MENTION DENSE FOG FOR NOW. HOWEVER, EVENING SHIFT WILL NEED TO KEEP A CLOSE EYE ON THE SITUATION. WEDNESDAY-FRIDAY: SIGNIFICANT WARMING TREND EXPECTED THIS PERIOD, AS WESTERN RIDGE FLATTENS IN RESPONSE TO SHORTWAVE ENERGY PROGRESSING THROUGH THE EASTERN PACIFIC. CONSEQUENTLY, ZONAL FLOW ALOFT WILL SET UP, SPREADING A RELATIVELY MILD PACIFIC AIRMASS ACROSS ESSENTIALLY THE ENTIRE CONUS. AS PREVIOUS FORECASTER ALLUDED TO, SUN'S ENERGY WILL GO TOWARD MELTING THE 2-5 INCH SNOWPACK ACROSS THE AREA, BUT THINKING SNOW WILL BE COMPLETELY MELTED BY FRIDAY, WITH QUITE A BIT OF IT LIKELY ALREADY MELTED BY THURSDAY. SATURDAY-MONDAY: MODELS ARE INDICATING A COOL DOWN FOR SATURDAY AND SUNDAY, AS A RATHER POTENT SHORTWAVE DROPS SOUTHEAST ACROSS THE MIDWEST. THE 20/12Z GFS SOLUTION IS BY FAR THE OUTLIER, AMPLIFYING THE TROUGH MUCH DEEPER AND FARTHER WEST THAN THE ETA, ECMWF, CANADIAN, UKMET AND NCEP ENSEMBLE MEAN. CONSEQUENTLY, DID NOT COOL TEMPERATURES TO THE EXTENT THAT THE GFS SUGGESTED. INSERTED SLIGHT CHANCE OF LIGHT RAIN ON SATURDAY TO ACCOUNT FOR PASSING SHORTWAVE. BY MONDAY ALL MODELS ARE INDICATING ANOTHER SIGNIFICANT WARMING TREND ACROSS THE AREA, AS WESTERN RIDGE BUILDS AND EASTERN TROUGH MOVES EAST. 00Z NCEP GFS ENSEMBLES (SPAGHETTI PLOTS) HAVE AMAZING AND ALMOST UNPRECEDENTED AGREEMENT WITH THIS WARMING TREND EVEN AT 168 HOURS OUT. ECMWF IS ALSO CLOSE TO THESE SOLUTIONS. WENT RATHER CONSERVATIVE IN THE FORECAST FOR NOW, AND ONLY WENT WITH 50S-LOW 60S. HOWEVER, GIVEN WARM 850 MB TEMPERATURES AND TAKING INTO ACCOUNT ONLY MARGINAL MIXING MAY YIELD HIGH TEMPERATURES WELL INTO THE 60S. COULD BE FLIRTING WITH RECORD HIGHS, WHICH GENERALLY RANGE FROM 65-70 DEGREES. KLEINSASSER && PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 17 43 26 56 / 0 0 0 0 HUTCHINSON 15 41 24 53 / 0 0 0 0 NEWTON 15 41 24 53 / 0 0 0 0 ELDORADO 18 42 25 55 / 0 0 0 0 WINFIELD-KWLD 19 47 27 59 / 0 0 0 0 RUSSELL 13 40 22 51 / 0 0 0 0 GREAT BEND 14 41 23 52 / 0 0 0 0 SALINA 10 39 21 51 / 0 0 0 0 MCPHERSON 13 40 23 51 / 0 0 0 0 COFFEYVILLE 21 47 27 59 / 0 0 0 0 CHANUTE 21 44 26 56 / 0 0 0 0 IOLA 20 42 26 55 / 0 0 0 0 && .ICT WATCHES/WARNINGS/ADVISORIES... FREEZING FOG ADVISORY UNTIL 10 AM WEDNESDAY FOR KSZ032-033- 047>053-067>069-082-083-091>093. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WICHITA KS 604 PM CST TUE DEC 20 2005 .AVIATION... MAIN CONCERN FOR AVIATION USERS TONIGHT WILL BE THE POTENTIAL FOR LOW INSTRUMENT FLIGHT RATING CONDITIONS TONIGHT. LATEST FOG IMAGERY SHOWING THE LOW CLOUDS SLOWLY PUSHING EAST. AFTER EXAMINING THE RUC 275K THETA SURFACE THERE IS VERY LITTLE IN THE WAY OF DOWNGLIDE TAKING PLACE ACROSS SOUTH CENTRAL KANSAS. THE RUC/ETA ARE BOTH SHOWING THIS TREND CONTINUING THROUGH THE EVENING. WITH THAT IN MIND... WE ARE GETTING CONCERNED ABOUT THE LOW CLOUD DECK SLOWING DOWN ITS PROGRESSION WHICH WOULD BRING FORTH THE RISK OF DENSE FOG DEVELOPMENT WITHIN THE REGION THAT HAS CEILINGS BELOW 1KFT. ANOTHER CONCERN IS THE AREA JUST BEHIND THIS LOW CLOUD DECK WHERE THE BOUNDARY LAYER IS STILL RATHER SATURATED. THIS AREA IS MAINLY CONFINED TO JUST ALONG AND EAST OF A HUTCHINSON TO SALINA LINE TO AREAS ALONG AND WEST OF A WINFIELD TO EMPORIA LINE. THE AREAS WHERE THE CEILINGS ARE BELOW 1KFT HAVE A PRETTY GOOD SHOT OF SEEING STRATUS BUILD DOWN DUE TO SNOW COVER AND POTENTIAL FOR FOG TOP COOLING FROM CLEAR SKIES ABOVE THE STRATUS DECK. MEANWHILE... AREAS JUST BEHIND THE CLEARING LINE MAY HAVE THE POTENTIAL FOR MORE SHALLOW PATCHY DENSE FOG... DUE TO MORE DEPOSITION AND SUBSIDENCE. WE WILL CONTINUE TO MONITOR THE PROGRESSION OF THE LOW CLOUDS FOR NOW AND POSSIBLY ISSUE A HEADLINE DURING THE NEXT COUPLE OF HOURS. TIMING OF THE DENSE FOG COULD BE LATE THIS EVENING OR JUST AFTER MIDNIGHT. && COX && .PREV DISCUSSION... /ISSUED 319 PM CST TUE DEC 20 2005/ DISCUSSION... FORECAST CONCERN/CHALLENGE IS LOW CLOUDS AND FOG POTENTIAL TONIGHT. THEREAFTER, EXTENT AND MAGNITUDE OF POTENTIALLY SIGNIFICANT WARMING TREND WILL BE THE MAIN FOCUS. TONIGHT: LOW STRATUS HAS BEEN MUCH SLOWER TO CLEAR OUT THAN EXPECTED, AND THIS TREND SHOULD CONTINUE TONIGHT. WEAK LOW-LEVEL TROUGH WILL PROGRESS SOUTHEAST ACROSS THE CWA TONIGHT, HELPING TO CLEAR THE CLOUDS FROM NORTHWEST TO SOUTHEAST THROUGH THE OVERNIGHT HOURS. THINKING FOG POTENTIAL WILL BE GREATEST JUST BEHIND THE CLEARING LINE OVER SNOW COVER, WHERE DEWPOINTS SHOULD BE HIGHER AND RADIATIONAL COOLING GREATEST. LATEST LAPS SOUNDINGS INDICATE FAIRLY DEEP LOW-LEVEL MOISTURE ACROSS THE EASTERN 2/3 OF THE CWA, SO ENOUGH MOISTURE SHOULD BE PRESENT FOR FOG EVEN AFTER FULL RADIATIONAL COOLING/DRYING. ONLY POTENTIAL MITIGATING FACTOR WILL BE LIGHT WESTERLY DOWNSLOPE FLOW, SO DID NOT MENTION DENSE FOG FOR NOW. HOWEVER, EVENING SHIFT WILL NEED TO KEEP A CLOSE EYE ON THE SITUATION. WEDNESDAY-FRIDAY: SIGNIFICANT WARMING TREND EXPECTED THIS PERIOD, AS WESTERN RIDGE FLATTENS IN RESPONSE TO SHORTWAVE ENERGY PROGRESSING THROUGH THE EASTERN PACIFIC. CONSEQUENTLY, ZONAL FLOW ALOFT WILL SET UP, SPREADING A RELATIVELY MILD PACIFIC AIRMASS ACROSS ESSENTIALLY THE ENTIRE CONUS. AS PREVIOUS FORECASTER ALLUDED TO, SUN'S ENERGY WILL GO TOWARD MELTING THE 2-5 INCH SNOWPACK ACROSS THE AREA, BUT THINKING SNOW WILL BE COMPLETELY MELTED BY FRIDAY, WITH QUITE A BIT OF IT LIKELY ALREADY MELTED BY THURSDAY. SATURDAY-MONDAY: MODELS ARE INDICATING A COOL DOWN FOR SATURDAY AND SUNDAY, AS A RATHER POTENT SHORTWAVE DROPS SOUTHEAST ACROSS THE MIDWEST. THE 20/12Z GFS SOLUTION IS BY FAR THE OUTLIER, AMPLIFYING THE TROUGH MUCH DEEPER AND FARTHER WEST THAN THE ETA, ECMWF, CANADIAN, UKMET AND NCEP ENSEMBLE MEAN. CONSEQUENTLY, DID NOT COOL TEMPERATURES TO THE EXTENT THAT THE GFS SUGGESTED. INSERTED SLIGHT CHANCE OF LIGHT RAIN ON SATURDAY TO ACCOUNT FOR PASSING SHORTWAVE. BY MONDAY ALL MODELS ARE INDICATING ANOTHER SIGNIFICANT WARMING TREND ACROSS THE AREA, AS WESTERN RIDGE BUILDS AND EASTERN TROUGH MOVES EAST. 00Z NCEP GFS ENSEMBLES (SPAGHETTI PLOTS) HAVE AMAZING AND ALMOST UNPRECEDENTED AGREEMENT WITH THIS WARMING TREND EVEN AT 168 HOURS OUT. ECMWF IS ALSO CLOSE TO THESE SOLUTIONS. WENT RATHER CONSERVATIVE IN THE FORECAST FOR NOW, AND ONLY WENT WITH 50S-LOW 60S. HOWEVER, GIVEN WARM 850 MB TEMPERATURES AND TAKING INTO ACCOUNT ONLY MARGINAL MIXING MAY YIELD HIGH TEMPERATURES WELL INTO THE 60S. COULD BE FLIRTING WITH RECORD HIGHS, WHICH GENERALLY RANGE FROM 65-70 DEGREES. KLEINSASSER && PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 17 43 26 56 / 0 0 0 0 HUTCHINSON 15 41 24 53 / 0 0 0 0 NEWTON 15 41 24 53 / 0 0 0 0 ELDORADO 18 42 25 55 / 0 0 0 0 WINFIELD-KWLD 19 47 27 59 / 0 0 0 0 RUSSELL 13 40 22 51 / 0 0 0 0 GREAT BEND 14 41 23 52 / 0 0 0 0 SALINA 10 39 21 51 / 0 0 0 0 MCPHERSON 13 40 23 51 / 0 0 0 0 COFFEYVILLE 21 47 27 59 / 0 0 0 0 CHANUTE 21 44 26 56 / 0 0 0 0 IOLA 20 42 26 55 / 0 0 0 0 && .ICT WATCHES/WARNINGS/ADVISORIES... NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PADUCAH KY 218 PM CST TUE DEC 20 2005 .DISCUSSION... IN THE NEAR TERM /TONIGHT AND TOMORROW/...CURRENT GOES WV LOOP SHOWS SHORTWAVE OVER OZARKS CONTINUING TO DIG SOUTH AND EAST. ASSOCIATED H85 LOW AND RETURN UPGLIDE MOISTURE HAS LED TO EXPANSIVE BANK OF OVERCAST STRATOCU FROM SOUTHERN IL TO THE TX COAST. SGF 12Z RAOB INDICATED SATURATED LAYER A COUPLE THOUSAND FEET THICK AND PIREPS REPORTS INDICATE THIS IS ADVECTING EAST ACROSS SOUTHERN MO. THESE CLOUDS KEPT TEMPS WELL BELOW NORMAL FOR ONE MORE DAY ACROSS THE CWA THIS AFTERNOON...AND WILL KEEP MINS TONIGHT ABOUT TEN DEGREES ABOVE VALUES FROM THIS MORNING. HAVE GUIDED CLOSELY TO RUC AND NAM SOLUTIONS FOR SKY COVER TONIGHT. MOS VALUES IN GOOD AGREEMENT YET HANDLING SKY COVER POORLY SO WENT A COUPLE DEGREES WARMER OVER SEMO AND WESTERN KY. IN THE LONGER TERM /WEDNESDAY THROUGH NEXT TUESDAY/...THE 12KM NAM AND 40KM GFS GUIDANCE SHARE SIMILAR MODEL SOLUTIONS THROUGH WEDNESDAY...BUT BEGIN TO SLOWLY DIFFER WITH THE HANDLING OF A SHORTWAVE ENTERING THE NW PACIFIC COASTLINE. THIS FEATURE BECOMES PROBLEMATIC WITH RESPECT TO THE CHRISTMAS DAY FORECAST IN THE GFS. IN THE 06/12Z GFS RUNS...THE SHORTWAVE IS PROGGED TO DEEPEN INTO A SIGNIFICANT LOW OVER THE PAH FORECAST AREA. THIS IS INCONSISTENT WITH PREVIOUS RUNS AND CONTINUITY WITH OTHER LONGER RANGE MODELS. THE GFS ENSEMBLE MEAN IS ACTUALLY LESS AMPLIFIED AND MORE ZONAL WITH THE HEIGHT FIELDS THAN THE OPERATIONAL 40KM GFS AVAILABLE TO THE FIELD. IN COORDINATION WITH HPC AND VARIOUS SURROUNDING FIELD OFFICES...THE GFS GUIDANCE IN THE SUNDAY-MONDAY TIME FRAME REMAINS SUSPECT. FOR NOW...HAVE LEANED TOWARD SLIGHTLY WARMER AND MUCH DRIER SOLUTION FOR CHRISTMAS DAY...CLOSER TO THE EUROPEAN/UKMET/GFS ENSEMBLE MEAN. A LITTLE EARLIER...IN THE FRIDAY-SATURDAY TIME FRAME...I HAVE CHOSEN A LESS AMPLIFIED...WARMER AND FURTHER NORTH SOLUTION THAN THE 40KM GFS...BUT MAINTAIN CONTINUITY WITH PREVIOUS FORECAST PACKAGES ON POPS AND WX. FOR NOW...THIS IS THE ONLY TIME PERIOD FOR WHICH PRECIPITATION IS POSTED FOR THE NEXT 7 DAYS. EVEN THOUGH WINTER OFFICIAL BEGINS TOMORROW...TEMPERATURES ARE PROGGED TO BE AT OR ABOVE NORMAL FOR MAX AND MIN TEMPERATURES...WITH ONLY A BRIEF EARLY NEXT MONDAY. && .PAH WATCHES/WARNINGS/ADVISORIES... KY...NONE. MO...NONE. IL...NONE. IN...NONE. && $$ MTF/SMITH ky AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PADUCAH KY 1144 AM CST TUE DEC 20 2005 .UPDATE... FORECAST TWEAKED TO REFLECT FASTER ADVANCE OF STRATUS/STRATOCU AND IMPACT ON TEMPS AS WELL AS TO INTRODUCE CHANCE OF FLURRIES IN FAR WESTERN AREAS. LATEST VISIBLE SHOWS CLOUD LINE BISECTING FROM NORTH TO SOUTH ACROSS CWA. 15Z SFC ANALYSIS PLACED THE CENTER OF THE CANADIAN HIGH OVER THE MISSOURI BOOTHEEL. WEAK LOW LEVEL WARM AIR ADVECTION ON BACK SIDE OF HIGH ASSOCIATED WITH SHORTWAVE OVER SOUTH CENTRAL PLAINS. RUC 280K ISENTROPIC SFC SHOWS WEAK MOIST UPGLIDE INTO THIS CLOUD LAYER. WITH HIGHER TDS THAN PREVIOUSLY HINTED AT CHANCE FOR FLURRIES HAS BEEN INTRODUCED FROM POPLAR BLUFF WESTWARD. DESPITE NO SUN IN SEMO AND PURCHASE AREA OF KY DO BELIEVE TEMPS WILL CLIMB A FEW DEGREES MORE DUE TO LIGHT SOUTHWEST FLOW. && .PREV DISCUSSION... (ISSUED 353 AM CST TUE DEC 20 2005) DISCUSSION... MAIN CHALLENGE IN THE SHORT TERM WILL BE SKY COVER TODAY THROUGH WEDNESDAY. THEN OUR ATTENTION TURNS TO THE NEXT CHANCE OF PRECIPITATION OVER THE UPCOMING HOLIDAY WEEKEND. LATEST SATELLITE IMAGERY DEPICTS AN EXPANSIVE LOW CLOUD DECK JUST TO THE WEST OF OUR FORECAST AREA...COVERING MUCH OF ARKANSAS AND THE WESTERN HALF OF MISSOURI. WHILE 00Z MOS GUIDANCE DOES NOT HAVE A GOOD HANDLE ON THIS...THE MODEL MOISTURE FIELDS FROM THE BOTH THE NAM AND GFS DO. USING THIS INFORMATION...WE BELIEVE THE CLOUD COVER TO OUR WEST WILL GRADUALLY OVERSPREAD THE AREA TODAY AND TONIGHT...WITH MUCH OF THE AREA BROKEN TO OVERCAST BY THIS TIME WEDNESDAY MORNING. THIS WILL HAVE A SIGNIFICANT IMPACT ON TEMPERATURES...AS OUR MISSOURI COUNTIES WILL LIKELY BE AT LEAST A FEW DEGREES COOLER THAN THE REST OF THE AREA TODAY...THEN MUCH WARMER THAN OUR EASTERN COUNTIES TONIGHT. THE CLOUDINESS SHOULD ERODE ON WEDNESDAY...WITH MAINLY CLEAR CONDITIONS HEADING INTO FRIDAY. THAT/S WHEN CLOUD COVER FROM THE NEXT WEATHER SYSTEM WILL BE APPROACHING OUR AREA. THE GFS CONTINUES TO NUDGE THIS SYSTEM INTO THE AREA A LITTLE BIT SOONER WITH EACH MODEL RUN. AS A RESULT...WE INTRODUCED A SLIGHT CHANCE POP FOR FRIDAY NIGHT. WE ALSO BUMPED UP POPS TO CHANCE CATEGORY ON SATURDAY. SOUNDINGS INDICATE CONDITIONS WARM ENOUGH FOR ALL LIQUID BOTH PERIODS. ALSO ADDED A CHANCE POP SATURDAY NIGHT FOR THE EASTERN HALF OF THE AREA. THIS COULD BE TRICKY AS THE REGION WILL BE CAUGHT IN THE DEFORMATION ZONE OF LOW PRESSURE OVER THE SOUTHERN STATES. IF ENOUGH COLD AIR CAN INFILTRATE THE AREA BEFORE WE LOSE THE MOISTURE FOR ICE CRYSTAL NUCLEATION...THE RAIN MIGHT CHANCE TO SNOW BRIEFLY BEFORE ENDING. WITH REGARD TO TEMPERATURES...SHAVED OFF A COUPLE DEGREES FROM MOS OVER MAINLY SOUTHEAST MISSOURI TO ACCOUNT INCREASING SKY COVER TODAY. WENT ABOVE MOS TONIGHT AND BELOW MOS WEDNESDAY TO ACCOUNT FOR CLOUDINESS. WILL LEAVE REMAINDER OF FORECAST AS IS FOR NOW. PAH WATCHES/WARNINGS/ADVISORIES... KY...NONE. MO...NONE. IL...NONE. IN...NONE. $$ RJP/MTF ky AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE CARIBOU ME 729 PM EST TUE DEC 20 2005 .SYNOPSIS...AN ARCTIC FRONT WILL MOVE OFF THE COAST THIS EVENING AS COLD HIGH PRESSURE BUILD OVER THE REGION TONIGHT. HIGH PRESSURE WILL MOVE EAST OF THE AREA WEDNESDAY AFTERNOON AS WEAK LOW PRESSURE APPROACHES FROM THE WEST. THIS LOW WILL QUICKLY MOVE THROUGH THE STATE WEDNESDAY NIGHT WITH SCATTERED FLURRIES. HIGH PRESSURE BUILDS OVER THE REGION ON THURSDAY. && .SHORT TERM (REST OF TONIGHT)... UPDATED THE GRIDS & ZFP MAINLY FOR CONTINUATION OF =SN/SHSN OVER NERN & ERN SECTION W/DISTURBANCE MOVING THROUGH THE AREA. LIKED THE NAM12 SKY GRIDS FOR THE GENERAL TREND ESP DOWNEAST & GTHE COAST. USED THE RUC FOR OVERLAY ACROSS THE N & W. KEPT POPS IN 30-40% RANGE INTO 06Z FOR NERN & EXTREME ERN AREAS & THEN WIND THEM DOWN AFT 06Z. I BACKED UP THE CLEARING TREND BY 3 HRS AS 11.0-3.9 MICRON IR SATL IMAGERY SHOWING SOME CLOUDS REDEVELOPING ACROSS FAR N & NWRN ME DUE TO COLD AIR COMING OFF OPEN ST. LAWRENCE RIVER. DO THINK SOME CLOUDS WILL LINGER ACROSS THE FAR N & W OVERNIGHT. FURTHER S...CLEARING WILL TAKE HOLD & WINDS LETTING UP WILL ALLOW FOR A COLD NIGHT. NO OTHER CHGS MADE. && .MARINE...SCA STILL IN PLACE W/SEAS UP AT 5 FT. WINDS IN THE 15-20 KT RANGE. NO CHGS ATTM. && .PREVIOUS DISCUSSION... (ISSUED 314 PM EST TUE DEC 20 2005) SHORT TERM (TODAY THROUGH THURSDAY)... ARCTIC FRONT WILL MOVE OFF THE COAST THIS EVENING WITH SCATTERED FLURRIES MOST AREAS WITH FRONTAL PASSAGE. BAND OF SNOW SHOWERS OVER EXTREME EASTERN SECTIONS WILL PRODUCE AN INCH OR LESS OF SNOW ACCUMULATION THIS AFTERNOON. COLD HIGH PRESSURE BUILDS OVER THE REGION TONIGHT WITH LOWS IN SINGLE DIGITS MOST LOCATIONS. A SUNNY START TO WEDNESDAY BUT CLOUDS ON THE INCREASE BY AFTERNOON AS UPPER TROUGH APPROACHES FROM THE WEST. MAIN ENERGY OF TROUGH WILL MOVE SOUTHWEST OF THE REGION AND WITH COLD ARCTIC AIR OVER THE STATE ONLY EXPECTING FLURRIES WEDNESDAY NIGHT AS ASSOCIATED LOW PRESSURE QUICKLY MOVES THROUGH THE STATE. HIGH PRESSURE BUILDS OVER THE STATE ON THURSDAY. LONG TERM (THURSDAY NIGHT THROUGH MONDAY)... HIGH PRESSURE MOVES EAST OF THE STATE THURSDAY NIGHT AS NEXT TROUGH APPROACHES FROM THE WEST. MAIN ENERGY WITH THIS TROUGH WILL MOVE NORTH OF THE STATE WITH POSSIBLE WARM AIR ADVECTION LIGHT SNOW OVER NORTHERN SECTIONS ON FRIDAY. COLD FRONT WILL MOVE THROUGH THE STATE FRIDAY NIGHT AND BECOME STATIONARY OVER CENTRAL MAINE. A WEAK LOW PRESSURE WILL MOVE ALONG THE FRONT FOR POSSIBLE LIGHT SNOW ON SATURDAY. MANY DIFFERENT SOLUTIONS FOR EARLY NEXT WEEK SO LOW CONFIDENCE IN THE FORECAST AFTER CHRISTMAS DAY. AVIATION... VFR CONDITIONS EXCEPT FOR MVFR CONDITIONS AT TIMES THIS AFTERNOON OVER NORTHERN SITES WITH SNOW SHOWERS ASSOCIATED WITH ARCTIC FRONT. AS ARCTIC FRONT MOVES OFF THE COAST THIS EVENING...CLEARING SKIES ALL SITES LATER TONIGHT. MARINE... SEAS STILL ABOVE 5 FT THIS AFTERNOON BUT ARE SLOWLY COMING DOWN. WINDS HAVE DROPPED BELOW SCA LEVELS BUT HAVE DECIDED TO LEAVE SCA OUT FOR THIS EVENING. AS ARCTIC FRONT MOVES THROUGH THE WATERS THIS EVENING MAY GET A BRIEF PERIOD OF STRONG WINDS WITH INITIAL COLD AIR ADVECTION. SEAS AND WINDS SHOULD DROP BELOW SCA LEVELS BEFORE MIDNIGHT. CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...SMALL CRAFT ADVISORY FOR ANZ050 UNTIL MIDNIGHT WEDNESDAY. $$ UPDATE...HEWITT SHORT TERM/MARINE...FOSTER LONG TERM/MARINE...FOSTER AVIATION...FOSTER/NORTON me AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1020 PM EST TUE DEC 20 2005 UPDATE...MOST SIGNIFICANT CHANGE THIS EVENING...LOWERED TEMPERATURES 10-15F ACROSS INTERIOR SECTIONS OF THE EASTERN UP AND ACROSS EASTERN COUNTIES OF NORTHERN LOWER MICHIGAN...WHERE SCATTERED CLOUDS...SNOW COVER AND LIGHT WINDS HAVE PUSHED TEMPERATURES INTO THE SINGLE DIGITS...AS COLD AS 1F AT RACO AND ATLANTA...AND 5F AT ALPENA. ALSO...AS TEMPERATURES HAVE FALLEN THROUGH DEWPOINTS...CONDITIONS ARE FAVORABLE FOR PATCHY FOG WHERE BEST RADIATIONAL COOLING HAS OCCURRED...THUS ADDED A MENTION ACROSS E/SE COUNTIES OF NORTHERN LOWER MICHIGAN OVERNIGHT. THEN...PER SATELLITE TRENDS...UPSTREAM LOW TO MID LEVEL CLOUDS...AHEAD OF A SHORTWAVE DIVING SE THROUGH MANITOBA...WILL SPREAD INTO THE REGION OVERNIGHT...WHILE THE SURFACE PRESSURE GRADIENT SHOULD TIGHT SOMEWHAT...SO TEMPERATURES SHOULD RECOVER TO SOME DEGREE...PERHAPS 10-15F IN A SHORT PERIOD OF TIME AT SOME LOCATIONS...AND ANY SHALLOW FOG WILL BE HARD PRESSED TO PERSIST TO SUNRISE. ALSO...LATEST WIND GUIDANCE SUGGESTS INCREASING SURFACE TO 950 MB WINDS AND LOCAL ENHANCEMENT WILL PRODUCE SMALL CRAFT ADVISORY CONDITIONS ACROSS ALL NEARSHORE AREAS WEDNESDAY. IN FACT...GUSTS COULD APPROACH GALE FORCE FROM THE STRAITS TO PRESQUE ISLE LIGHT. MEANWHILE...DESPITE VERY DRY AIR...850-700 MB MEAN RH LESS THAN 30%...THE KAPX SOUNDING REVEALED AN INVERSION EXTENDING TO AROUND 850 MB...WHERE TEMPERATURES AVERAGED -12C TO -14C ACROSS THE REGION. AS A RESULT...LIGHT SNOW SHOWERS CONTINUED TO PUSH ONSHORE FROM LAKE MICHIGAN...TAPERING TO FLURRIES AS THEY ADVANCED INLAND AND EAST OF I-75. ALSO...MEAN 1000-850 MB WINDS WERE BACKING TOWARD THE WSW AHEAD OF THE APPROACHING WAVE...SO SNOW SHOWERS SHOULD FOCUS N/NW OF GAYLORD (LIKELY POPS THERE) OVERNIGHT...AS LATEST AVAILABLE NAM SOUNDINGS DEPICT INVERSIONS CONTINUING TO TAP INTO THE -10C TO -12C LAYER UNTIL AROUND 12Z. ALSO...GIVEN 700-500 QG FORCING AND DEEPER MOISTURE (850-700 MB MEAN RH GREATER THAN 70%...IN LINE WITH COLDER CLOUD TOPS/LIGHT SNOW UPSTREAM) SLATED TO ARRIVE AHEAD OF THE SHORTWAVE LATER TONIGHT...ATTENTION TURNS TO THE POTENTIAL FOR LAKE MICHIGAN ENHANCEMENT. 850 MB TEMPERATURES WILL WARM OVERNIGHT...INTO THE -7C TO -10C RANGE BY 12Z...SO BY THE TIME DEEPER MOISTURE ARRIVES LATER TONIGHT...OVER LAKE INSTABILITY WILL HAVE DECREASED...AND ENHANCEMENT POTENTIAL WILL HAVE DIMINISHED. THUS...ODDS DO NOT FAVOR ANY HEADLINE CRITERIA SNOW ACCUMULATION WITH THIS EVENT...BUT GIVEN THE CHANCE FOR A PERIOD OF HEAVIER SNOW LATE TONIGHT/EARLY WEDNESDAY MORNING RAISED 6Z-18Z SNOW AMOUNTS INTO THE 2-4" RANGE ACROSS FAVORED W TO WSW FLOW AREAS DOWNWIND OF LAKE MICHIGAN...AND EXPANDED HIGHER POPS/SLIGHTLY HIGHER SNOW ACCUMULATIONS INLAND...TO ACCOUNT FOR 1000-850 MB FLOW VEERING BACK TO THE WEST AND INCREASING TO 25-30 KNOTS...WEDNESDAY MORNING. ROWLEY && .PREV DISCUSSION...ISSUED 339 PM EST TUE DEC 20 DISCUSSION...SHORT TERM ISSUES (TONIGHT)...LIGHT LES CONTINUING IN N/NW FLOW AREAS OF NORTHERN LOWER DESPITE PRONOUNCED DRYING OF H8-H7 LAYER /RH VALUES LESS THAN 25%/. FOR THIS EVENING...H10-H8 FLOW WILL WEAKEN AND BACK TOWARD THE WEST IN ADVANCE OF NEXT SHORTWAVE TROF MOVING OUT OF SOUTHERN CANADA. ALTHOUGH MOISTURE IS QUITE LOW...RUC DOES SHOW TONGUE OF 30% RH FIELDS IN THE H8-H7 LAYER ALONG AND WEST OF US-131 IN NORTHERN LOWER. THIS...ALONG WITH AT LEAST A WEAK LAKE SUPERIOR CONNECTION AND FAVORABLE THERMAL REGIME...WILL LIKELY KEEP A FEW LIGHT SNOW SHOWERS AND FLURRIES GOING EARLY ON. AS THE LOW LEVEL WIND FIELDS DIMINISH DURING THE EVENING...LIGHT SNOW SHOWER ACTIVITY WILL DECREASE IN COVERAGE AND BECOME ORIENTED CLOSER TO THE LAKE MICHIGAN SHORELINE WITH ONLY FLURRIES POSSIBLE INLAND. 925MB WINDS DECREASE TOWARD 5 KTS DURING THE EVENING AND WE MAY SEE LAND BREEZES DEVELOP FOR A TIME ALONG LAKE MICHIGAN... PUSHING ANY REMAINING SNOW SHOWER ACTIVITY OFFSHORE. LOW LEVEL FLOW BACKS TO THE WEST-SOUTHWEST OVERNIGHT AS A SHORTWAVE TROF APPROACHES FROM THE NORTHWEST. IN ASSOCIATION WITH THIS...H9-H7 MOISTURE INCREASES RAPIDLY AFTER 09Z OVER NORTHERN AND WESTERN PARTS OF THE CWA. DESPITE THE INCREASING MOISTURE AND THE PRESENCE OF WEAK SYNOPTIC FORCING...LAKE ENHANCEMENT POTENTIAL LOOKS MINIMAL GIVEN WARMING H8 TEMPERATURES THROUGH THE PERIOD /H8 TEMPS OF -6 TO -8 DEGC BY 12Z WED/ AND RATHER DRY ANTECEDENT CONDITIONS. I WILL PUT LOW CHANCE SNOW SHOWERS IN SOUTHWEST FLOW AREAS AFTER 09Z...WITH LITTLE IF ANY ACCUMULATION. JK LONG TERM ISSUES (WEDNESDAY/THURSDAY)...AMPLIFIED NORTH AMERICAN FLOW PATTERN EXPECTED TO BECOME MORE ZONAL AS THE WEEK PROGRESSES AS WESTERN RIDGE GETS FLATTENED...BUT IS EXPECTED TO BUCKLE AGAIN THIS WEEKEND AS A SHORT WAVE TROUGH DEEPENS ACROSS THE OHIO VALLEY... EVENTUALLY CARVING OUT A NEW TROUGH ACROSS THE EASTERN STATES. WEAK MID LEVEL SHORT WAVE TROUGH SLIDES ACROSS NORTHERN MI WEDNESDAY MORNING...FOLLOWED BY MILDER PACIFIC AIR FLOODING INTO THE WESTERN GREAT LAKES REGION BY THURSDAY. FORECAST CONCERNS IN THE NEAR TERM WILL CENTER ON SHORT WAVE PASSAGE WEDNESDAY AND ASSOCIATED PRECIPITATION/LAKE ENHANCEMENT POTENTIAL...AND PRECIP CHANCES IN DEVELOPING WAA PATTERN LATER THURSDAY/THURSDAY NIGHT. WEDNESDAY...SHORT WAVE TROUGH SLIPS ACROSS THE AREA FROM THE NORTHWEST DURING THE MORNING...NOT EXPECTING MUCH MORE THAN LIGHT SNOW/FLURRIES WITH IT THOUGH MAY ALLOW FOR A BRIEF FLARE UP OF SNOW SHOWERS OUT OVER NORTHERN LAKE MICHIGAN FOR A COUPLE OF HOURS. LOWER LAYERS DRY OUT AGAIN DURING THE AFTERNOON (A SIMILAR CYCLE TO WHAT WE'VE SEEN THE PAST TWO DAYS). BEST CHANCE FOR SOME LINGERING AFTERNOON LES WILL BE IN WEST-NORTHWEST FLOW AREAS OFF LAKES SUPERIOR AND MICHIGAN (FORMER AREA AIDED BY PERSISTENT CONVERGENCE AXIS FORECAST ALONG NORTH SHORE OF THE U.P.). CONTINUED WARMING AND DRYING AS WINDS BACK AROUND TO SOUTHWEST WITH PASSAGE OF LOW LEVEL RIDGE AXIS SHOULD ALLOW ANY LINGERING SNOW SHOWER TO TAPER OFF OVERNIGHT. THURSDAY...FORECAST A BIT TRICKIER HERE WITH ANOTHER WEAK SHORT WAVE TRANSLATING SOUTHEAST ACROSS THE STATE. UPPER AND LOWER LEVEL MOISTURE NOT IN SYNC...MID/UPPER LEVEL MOISTURE MOVES IN DURING THE MORNING WITH LOW LEVELS PRETTY DRY (DEW POINT DEPRESSIONS AOA 20C BELOW 750MB)...THEN AS THE LOW LEVELS MOISTEN UPPER LEVEL MOISTURE THINS OUT (INCLUDING MOISTURE ABOVE -10C). SO MAY BE LOOKING AT A SITUATION OF LOW CHANCE POPS FOR SNOW EARLY...PERHAPS TRANSITIONING TO SOME LIGHT RAIN/DRIZZLE OR FREEZING RAIN IF SURFACE TEMPERATURES ARE STUBBORN TO CLIMB ABOVE FREEZING. PLAN TO CARRY ALL THREE PRECIP TYPES THURSDAY AFTERNOON EVERYWHERE EXCEPT SOUTH OF M-55. THURSDAY NIGHT SHALLOW MOIST LAYER REMAINS IN PLACE ALONG WITH PERSISTENT WAA...SO THE THREAT FOR DRIZZLE/FREEZING DRIZZLE WILL PERSIST...PERHAPS MIXING WITH SOME SNOW OVERNIGHT IF GFS IS CORRECT IN SPREADING SOME DEEPER MOISTURE BACK INTO THE AREA AHEAD OF ANOTHER SHORT WAVE TROUGH. MARINE...MAY NEED A SMALL CRAFT ADVISORY RIGHT OFF THE BAT WEDNESDAY MORNING...ESPECIALLY IN THE LAKE MICHIGAN NEARSHORE ZONES AND ALONG LAKE HURON NORTH OF PRESQUE ISLE LIGHT. WINDS SHOULD SUBSIDE LATER WEDNESDAY AFTERNOON...THEN PICK UP AGAIN FROM THE SOUTH/SOUTHWEST THURSDAY. EXTENDED PERIODS (FRIDAY THROUGH TUESDAY)...GENERAL MEAN PATTERN OF TROUGH EAST/RIDGE WEST WILL PERSIST INTO THE EXTENDED FORECAST PERIOD...THOUGH DOESN'T APPEAR TO BE AN EXCEPTIONALLY COLD PATTERN. LOOKS LIKE A CONTINUATION OF WAA TYPE PRECIP ON FRIDAY...THOUGH OVERALL EVOLUTION OF NEXT TROUGH IS STILL UNCERTAIN WITH GUIDANCE HAVING TRENDED SLOWER AND STRONGER WITH THIS SYSTEM. LOOKS LIKE THERE WILL CONTINUE TO BE PRECIP TYPE ISSUES WITH THIS...PERHAPS SOME FREEZING RAIN THREAT CONTINUING AS WELL SO WILL RUN THE GAMUT OF PRECIP TYPES FOR FRIDAY. CHANCE OF SNOW CONTINUES FOR SATURDAY THOUGH THIS FAR OUT DOESN'T APPEAR TO BE TOO SIGNIFICANT UNLESS SYSTEM TRACK CHANGES. SUNDAY SNOW CHANCES ARE A BIT MORE SUSPECT... THOUGH WILL HANG ONTO THEM GIVEN UNCERTAINTY AS TO EXTENT OF EAST COAST SYSTEM. BEYOND THIS WEEKEND...PRECIP CHANCES WILL BE TIED TO HARD TO TIME SHORT WAVE TROUGHS COMING OVER TOP OF THE UPPER RIDGE. WILL MAINTAIN CONTINUITY FOR MONDAY...BUT WILL START TUESDAY OUT DRY. PLAN TO KEEP TEMPERATURES SEASONABLE OR SLIGHTLY ABOVE THROUGH TUESDAY. JPB && .APX...WATCHES/WARNINGS/ADVISORIES...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 359 PM EST TUE DEC 20 2005 .DISCUSSION... THE MAIN CONCERN WITH THIS FORECAST PACKAGE IS THE POTENTIAL FOR SNOW TONIGHT AND WEDNESDAY. WATER VAPOR IMAGERY AND RUC/NAM SHOWING A LONGWAVE TROUGH OVER MUCH OF EASTERN NORTH AMERICA AND ANOTHER LONGWAVE TROUGH IN THE GULF OF ALASKA. THESE TROUGHS ARE SEPARATED BY A RIDGE OVER THE ROCKY MOUNTAINS. SURFACE ANALYSIS INDICATE A WEAK COLD FRONT ACROSS LOWER MICHIGAN EXTENDING THROUGH THE LOWER GREAT LAKES AND A LARGE HIGH OVER THE MIDDLE MISSISSIPPI RIVER VALLEY. THIS DOME OF HIGH PRESSURE BLANKETS MOST OF THE CENTRAL CONUS. COLD AIR ADVECTING INTO THE AREA WILL KEEP LAKE-850MB DELTA-T'S AROUND 13C OVER WESTERN LAKE SUPERIOR AND 15C OVER THE EAST. ANOTHER SHORTWAVE WILL ROTATE THROUGH THE BASE OF THIS LONGWAVE AND PASS THROUGH THE FORECAST AREA TONIGHT. THE HIGH WILL MOVE LITTLE. WARM AIR ADVECTION WILL REDUCE THE DELTA-T'S BY 2C OVERNIGHT. GFS/NAM SHOWING LOW LEVEL CONVERGENCE OVER LAKE SUPERIOR INCREASING. LAKE EFFECT SNOW THAT HAVE BEEN OVER THE FORECAST AREA TODAY WILL CONTINUE THIS EVENING. NAM SHOWING THE WINDS BACKING SOUTHWEST THIS EVENING WHICH SHOULD END THE CHANCE OF SNOW OVER THE EAST LATE. THE SHORTWAVE PASSING OVER THE FORECAST AREA WILL PUSH INTO THE LOWER GREAT LAKES ON WEDNESDAY WHILE ANOTHER APPROACHES FROM THE NORTHWEST. ANOTHER WEAK 850MB THERMAL TROUGH WILL SLIDE ACROSS EASTERN LAKE SUPERIOR. THE WINDS ARE EXPECTED TO SHIFT TO THE NORTHWEST OVER THE EASTERN LAKE SUPERIOR. Q-VECTOR CONVERGENCE COUPLED WITH THE COLD TEMPERATURES WILL KEEP LAKE EFFECT SNOWS GOING OVER THE EASTERN U.P. AND THE KEWEENAW PENINSULA. ANOTHER SHORTWAVE WILL SWEEP THROUGH THE U.P. WEDNESDAY NIGHT. THE SURFACE WINDS WILL BACK TO THE SOUTHWEST. GRADUALLY THE LAKE EFFECT SNOW WILL DIMINISH THROUGH OUT THE AREA EXCEPT FOR THE KEWEENAW PENINSULA...WHERE LES WILL LIKELY CONTINUE. A WEAK SHORTWAVE WILL SHIFT ACROSS THE FORECAST AREA ON THURSDAY. WARM AIR ADVECTION AT AROUND 800MB WILL PUSH TEMPERATURES TO WELL ABOVE FREEZING AT THAT LEVEL. BELOW 850MB THE AIR MASS WILL BE DRY AND BELOW FREEZING. THE FORECAST SOUNDINGS INDICATE SURFACE TEMPERATURE WELL BELOW FREEZING. THUS ANY WEATHER THAT MAY OCCUR WITH THIS SYSTEM COULD BE IN THE FORM OF FREEZING RAIN OR ICE PELLETS. ANOTHER WEAK SHORTWAVE WILL SAIL ACROSS THE U.P. THURSDAY NIGHT...WHILE A SURFACE LOW PRESSURE CENTRAL BEGINS TO DEVELOP OVER NORTHERN ALBERTA. ECMWF APPEARS TO BE MOST RELIABLE AS PER HPC DISCUSSION. ANOTHER SHORTWAVE WILL SWEEP THROUGH WISCONSIN AND INTO NORTHERN LOWER MICHIGAN ON FRIDAY. SURFACE ANALYSIS SHOW A LOW DEVELOPING OVER SOUTHERN MANITOBA WILL DROP INTO THE UPPER MICHIGAN ON FRIDAY DRAGGING A COLD FRONT THROUGH THE NORTHERN PLAINS...AND PULLING ANOTHER COLD FRONT OUT OF CENTRAL ONTARIO INTO LAKE SUPERIOR. THE MID LEVEL TROUGH OVER THE CENTRAL CONUS WILL MOVE INTO THE UPPER GREAT LAKES WHILE THE RIDGE CONTINUES OF BUILD OVER THE PACIFIC NORTHWEST FRIDAY NIGHT. THE SURFACE LOW WILL PUSH INTO THE LAKE SUPERIOR. Q-VECTOR CONVERGENCE AND ISENTROPIC ASCENT ASSOCIATED WITH THE COLD FRONT AND TROUGH WILL SQUEEZE MORE SNOW AND RAIN OVER THE AREA. THE WILL CONTINUE TO DEEPEN OVER THE UPPER GREAT LAKES ON SATURDAY WHILE THE SURFACE LOW MOVES INTO THE LOWER GREAT LAKES. IN ITS WAKE WILL BE A STRONG NORTH TO NORTHWEST FLOW OVER LAKE SUPERIOR... DRAWING IN COLD TEMPERATURES. AN 850MB THERMAL TROUGH WILL SET UP OVER THE UPPER GREAT LAKES ON SATURDAY. HOWEVER...THESE WILL ONLY CAUSE A LAKE-850MB DELTA-T OF AROUND 10C-12C WHICH WOULD NOT BE ENOUGH TO CAUSE MUCH PURE LAKE EFFECT SNOWS. IT MAY SUPPORT SOME LES ENHANCEMENT. A CHANCE OF SNOW LOOKS REASONABLE FOR SATURDAY AND SATURDAY NIGHT. THE MID LEVEL TROUGH WILL SHIFT INTO THE LOWER GREAT LAKES ON SUNDAY...WHILE THE PACIFIC COAST RIDGE MOVES INTO THE NORTHERN HIGH PLAINS. GFS BEGINS TO SLOW THE SYTEM DOWN MUCH MORE THAN THE ECMWF AND THE GLOBAL GEM. && MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 339 PM EST TUE DEC 20 2005 .DISCUSSION...SHORT TERM ISSUES (TONIGHT)...LIGHT LES CONTINUING IN N/NW FLOW AREAS OF NORTHERN LOWER DESPITE PRONOUNCED DRYING OF H8-H7 LAYER /RH VALUES LESS THAN 25%/. FOR THIS EVENING...H10-H8 FLOW WILL WEAKEN AND BACK TOWARD THE WEST IN ADVANCE OF NEXT SHORTWAVE TROF MOVING OUT OF SOUTHERN CANADA. ALTHOUGH MOISTURE IS QUITE LOW...RUC DOES SHOW TONGUE OF 30% RH FIELDS IN THE H8-H7 LAYER ALONG AND WEST OF US-131 IN NORTHERN LOWER. THIS...ALONG WITH AT LEAST A WEAK LAKE SUPERIOR CONNECTION AND FAVORABLE THERMAL REGIME...WILL LIKELY KEEP A FEW LIGHT SNOW SHOWERS AND FLURRIES GOING EARLY ON. AS THE LOW LEVEL WIND FIELDS DIMINISH DURING THE EVENING...LIGHT SNOW SHOWER ACTIVITY WILL DECREASE IN COVERAGE AND BECOME ORIENTED CLOSER TO THE LAKE MICHIGAN SHORELINE WITH ONLY FLURRIES POSSIBLE INLAND. 925MB WINDS DECREASE TOWARD 5 KTS DURING THE EVENING AND WE MAY SEE LAND BREEZES DEVELOP FOR A TIME ALONG LAKE MICHIGAN... PUSHING ANY REMAINING SNOW SHOWER ACTIVITY OFFSHORE. LOW LEVEL FLOW BACKS TO THE WEST-SOUTHWEST OVERNIGHT AS A SHORTWAVE TROF APPROACHES FROM THE NORTHWEST. IN ASSOCIATION WITH THIS...H9-H7 MOISTURE INCREASES RAPIDLY AFTER 09Z OVER NORTHERN AND WESTERN PARTS OF THE CWA. DESPITE THE INCREASING MOISTURE AND THE PRESENCE OF WEAK SYNOPTIC FORCING...LAKE ENHANCEMENT POTENTIAL LOOKS MINIMAL GIVEN WARMING H8 TEMPERATURES THROUGH THE PERIOD /H8 TEMPS OF -6 TO -8 DEGC BY 12Z WED/ AND RATHER DRY ANTECEDENT CONDITIONS. I WILL PUT LOW CHANCE SNOW SHOWERS IN SOUTHWEST FLOW AREAS AFTER 09Z...WITH LITTLE IF ANY ACCUMULATION. JK LONG TERM ISSUES (WEDNESDAY/THURSDAY)...AMPLIFIED NORTH AMERICAN FLOW PATTERN EXPECTED TO BECOME MORE ZONAL AS THE WEEK PROGRESSES AS WESTERN RIDGE GETS FLATTENED...BUT IS EXPECTED TO BUCKLE AGAIN THIS WEEKEND AS A SHORT WAVE TROUGH DEEPENS ACROSS THE OHIO VALLEY... EVENTUALLY CARVING OUT A NEW TROUGH ACROSS THE EASTERN STATES. WEAK MID LEVEL SHORT WAVE TROUGH SLIDES ACROSS NORTHERN MI WEDNESDAY MORNING...FOLLOWED BY MILDER PACIFIC AIR FLOODING INTO THE WESTERN GREAT LAKES REGION BY THURSDAY. FORECAST CONCERNS IN THE NEAR TERM WILL CENTER ON SHORT WAVE PASSAGE WEDNESDAY AND ASSOCIATED PRECIPITATION/LAKE ENHANCEMENT POTENTIAL...AND PRECIP CHANCES IN DEVELOPING WAA PATTERN LATER THURSDAY/THURSDAY NIGHT. WEDNESDAY...SHORT WAVE TROUGH SLIPS ACROSS THE AREA FROM THE NORTHWEST DURING THE MORNING...NOT EXPECTING MUCH MORE THAN LIGHT SNOW/FLURRIES WITH IT THOUGH MAY ALLOW FOR A BRIEF FLARE UP OF SNOW SHOWERS OUT OVER NORTHERN LAKE MICHIGAN FOR A COUPLE OF HOURS. LOWER LAYERS DRY OUT AGAIN DURING THE AFTERNOON (A SIMILAR CYCLE TO WHAT WE'VE SEEN THE PAST TWO DAYS). BEST CHANCE FOR SOME LINGERING AFTERNOON LES WILL BE IN WEST-NORTHWEST FLOW AREAS OFF LAKES SUPERIOR AND MICHIGAN (FORMER AREA AIDED BY PERSISTENT CONVERGENCE AXIS FORECAST ALONG NORTH SHORE OF THE U.P.). CONTINUED WARMING AND DRYING AS WINDS BACK AROUND TO SOUTHWEST WITH PASSAGE OF LOW LEVEL RIDGE AXIS SHOULD ALLOW ANY LINGERING SNOW SHOWER TO TAPER OFF OVERNIGHT. THURSDAY...FORECAST A BIT TRICKIER HERE WITH ANOTHER WEAK SHORT WAVE TRANSLATING SOUTHEAST ACROSS THE STATE. UPPER AND LOWER LEVEL MOISTURE NOT IN SYNC...MID/UPPER LEVEL MOISTURE MOVES IN DURING THE MORNING WITH LOW LEVELS PRETTY DRY (DEW POINT DEPRESSIONS AOA 20C BELOW 750MB)...THEN AS THE LOW LEVELS MOISTEN UPPER LEVEL MOISTURE THINS OUT (INCLUDING MOISTURE ABOVE -10C). SO MAY BE LOOKING AT A SITUATION OF LOW CHANCE POPS FOR SNOW EARLY...PERHAPS TRANSITIONING TO SOME LIGHT RAIN/DRIZZLE OR FREEZING RAIN IF SURFACE TEMPERATURES ARE STUBBORN TO CLIMB ABOVE FREEZING. PLAN TO CARRY ALL THREE PRECIP TYPES THURSDAY AFTERNOON EVERYWHERE EXCEPT SOUTH OF M-55. THURSDAY NIGHT SHALLOW MOIST LAYER REMAINS IN PLACE ALONG WITH PERSISTENT WAA...SO THE THREAT FOR DRIZZLE/FREEZING DRIZZLE WILL PERSIST...PERHAPS MIXING WITH SOME SNOW OVERNIGHT IF GFS IS CORRECT IN SPREADING SOME DEEPER MOISTURE BACK INTO THE AREA AHEAD OF ANOTHER SHORT WAVE TROUGH. MARINE...MAY NEED A SMALL CRAFT ADVISORY RIGHT OFF THE BAT WEDNESDAY MORNING...ESPECIALLY IN THE LAKE MICHIGAN NEARSHORE ZONES AND ALONG LAKE HURON NORTH OF PRESQUE ISLE LIGHT. WINDS SHOULD SUBSIDE LATER WEDNESDAY AFTERNOON...THEN PICK UP AGAIN FROM THE SOUTH/SOUTHWEST THURSDAY. EXTENDED PERIODS (FRIDAY THROUGH TUESDAY)...GENERAL MEAN PATTERN OF TROUGH EAST/RIDGE WEST WILL PERSIST INTO THE EXTENDED FORECAST PERIOD...THOUGH DOESN'T APPEAR TO BE AN EXCEPTIONALLY COLD PATTERN. LOOKS LIKE A CONTINUATION OF WAA TYPE PRECIP ON FRIDAY...THOUGH OVERALL EVOLUTION OF NEXT TROUGH IS STILL UNCERTAIN WITH GUIDANCE HAVING TRENDED SLOWER AND STRONGER WITH THIS SYSTEM. LOOKS LIKE THERE WILL CONTINUE TO BE PRECIP TYPE ISSUES WITH THIS...PERHAPS SOME FREEZING RAIN THREAT CONTINUING AS WELL SO WILL RUN THE GAMUT OF PRECIP TYPES FOR FRIDAY. CHANCE OF SNOW CONTINUES FOR SATURDAY THOUGH THIS FAR OUT DOESN'T APPEAR TO BE TOO SIGNIFICANT UNLESS SYSTEM TRACK CHANGES. SUNDAY SNOW CHANCES ARE A BIT MORE SUSPECT... THOUGH WILL HANG ONTO THEM GIVEN UNCERTAINTY AS TO EXTENT OF EAST COAST SYSTEM. BEYOND THIS WEEKEND...PRECIP CHANCES WILL BE TIED TO HARD TO TIME SHORT WAVE TROUGHS COMING OVER TOP OF THE UPPER RIDGE. WILL MAINTAIN CONTINUITY FOR MONDAY...BUT WILL START TUESDAY OUT DRY. PLAN TO KEEP TEMPERATURES SEASONABLE OR SLIGHTLY ABOVE THROUGH TUESDAY. JPB && .APX...WATCHES/WARNINGS/ADVISORIES...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 200 PM CST TUE DEC 20 2005 .DISCUSSION... QUIET WEATHER CONTINUES ACROSS THE REGION AS SFC HIGH PRESSURE SITS OVR THE CENTRAL PLAINS. LATEST WATER VAPOR IMAGERY AND RUC 500MB ANALYSIS SHOWS UPPER RIDGE BUILDING OVER THE WESTERN CONUS WITH NWRLY FLOW PREVAILING ACROSS THE CENTRAL PLAINS. ALSO OF NOTE ON WATER VAPOR IMAGERY IS LARGE CIRCULATION OVER THE EASTERN PACIFIC. PIECES OF THIS SYSTEM ARE FORECAST TO MOVE INTO THE CENTRAL PLAINS BY LATE IN THE WEEK. TEMPERATURES WL CONTINUE TO WARM THROUGHOUT THE WEEK AS THE RIDGE SLIDES EWD. FLOW BECOMES MORE ZONAL ALLOWING WARMER PACIFIC AIR TO FILTER INTO THE REGION. TEMPERATURES ON WED SHOULD BE IN THE LOWER 40S WITH READINGS ON THURSDAY INTO THE LOWER 50S. ENERGY FROM THE SYSTEM CURRENTLY OFF THE NORTHWEST PACIFIC COAST WL MAKE IT'S WAY INTO THE CENTRAL PLAINS ON FRIDAY NIGHT. THE ECMWF HAS TRENDED MORE TOWARD THE GFS AND THEREFORE WL CONTINUE THE SLIGHT CHANCE POPS CURRENTLY IN THE FORECAST. THE 12Z GFS HAS SHIFTED THE SHORTWAVE ENERGY MORE TO THE SOUTHWEST THAN PREVIOUS RUNS. PCPN TYPE STILL LOOKS QUESTIONABLE AS COLDER 850MB TEMPS DROP SOUTH INTO THE CNTRL PLAINS. WL LEAVE AS A RA/SN MENTION HOWEVER COULD BE SOME PERIODS OF FREEZING RAIN LATE FRI NIGHT/SATURDAY MORNING AS FORECAST LOWS ARE IN THE LOW TO MID 20S WITH 850MB TEMPS HOVERING AROUND 0C. HIGH AMPLITUDE RIDGE BEGINS TO BUILD TO OVER THE WRN CONUS THRU THE HOLIDAY WEEKEND AND SHIFTS EWD THRU THE EARLY PART OF NEXT WEEK. TEMPERATURES SHOULD RANGE IN THE 40S FOR HIGHS WITH NO ADDITIONAL PCPN EXPECTED. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ GRIFFIS ne AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE RALEIGH NC 1040 AM EST TUE DEC 20 2005 .SHORT TERM (REST OF TODAY THROUGH TONIGHT)... IN GENERAL...HIGH PRESSURE WAS DOMINATING THE WEATHER OF CENTRAL NORTH CAROLINA WITH A WEAK SURFACE GRADIENT IN PLACE. 12Z UPPER-AIR ANALYSIS SHOWED AN 850MB TROUGH OVER THE FAR SOUTHEAST CONUS WITH A POSSIBLE WEAK 850MB LOW OVER GEORGIA AND WEAK CONVERGENCE ALONG AND NORTHEAST OF THERE. THESE FEATURES...COUPLED WITH RUC AND NAM40 ANALYZED POOL OF 850MB MOISTURE...LIKELY CONTRIBUTORS TO CLOUD COVER THAT EXTENDED FROM NEAR LEXINGTON AND ALBEMARLE SOUTHWEST TOWARD ATLANTA. DURING THE AFTERNOON...BOTH THE RUC AND THE NAM40 SHOW THIS MOISTURE GRADUALLY MOVING EAST-SOUTHEAST...EXITING CENTRAL NORTH CAROLINA BY 21Z. MOST OF THE FORECAST AREA SHOULD BE MOSTLY SUNNY THIS AFTERNOON. HOWEVER...MODIFIED SOUTHWEST AND SOUTH-CENTRAL ZONES TO PARTLY CLOUDY EARLY AND TWEAKED SKY COVER GRIDDED FORECAST VALUES UPWARD SOME TO ACCOUNT FOR CLOUDS. PRONOUNCED TROUGH DIGGING OVER THE SOUTHERN PLAINS THIS EVENING IS FORECAST TO MOVE ACROSS THE SOUTHEAST STATES LATE TONIGHT AND EARLY WEDNESDAY. ALTHOUGH THE TROUGH IS FORECAST TO WEAKEN AS IT MOVES EAST...BOTH THE 06Z GFS AND THE 12Z NAM SUPPORT AN INCREASE IN MID AND UPPER-LEVEL MOISTURE AS THE TROUGH APPROACHES LATE THIS EVENING. PARTICULARLY ALONG AND EAST OF APPROXIMATELY U.S. 1... 500MB MOISTURE EQUALS OR EXCEEDS 80 PERCENT BY 09Z. THIS MOISTURE IS FORECAST TO MOVE QUICKLY EAST LATE TONIGHT AND VERY EARLY WEDNESDAY...BUT THERE WILL LIKELY BE ENOUGH CLOUDS ASSOCIATED WITH THE TROUGH TO PROVIDE FOR A PERIOD OF AT LEAST PARTLY CLOUDY CONDITIONS OVER AT LEAST THE SOUTHEAST HALF OF THE FORECAST AREA. DO NOT ANTICIPATE ANY MORE THAN MID-LEVEL CLOUDS AS MODEL SOUNDINGS SHOW A VERY DRY AIR MASS BELOW 700MB AND K INDICES ARE ANYWHERE FROM -30 TO -50. HAVE ADJUSTED SKY COVER GRIDDED AND WORDED FORECASTS TO TREND TOWARD MORE CLOUD COVER IN PARTS OF CENTRAL NORTH CAROLINA LATE TONIGHT. && .PREVIOUS DISCUSSION... (ISSUED 225 AM EST TUE DEC 20 2005) SHORT TERM (TODAY THROUGH SATURDAY)... WITH LITTLE MORE THAN CIRRUS CLOUDS DURING THIS PERIOD...FORECAST BOILS DOWN TO TEMPERATURES. MODEL THICKNESS AND SOUNDINGS SUGGEST ALPHANUMERIC GUIDANCE IS WARM FOR THIS AFTERNOON. HOWEVER HAVE GENERALLY FOUND IN THESE CASES IT IS THE ALPHANUMERIC GUIDANCE THAT VERIFIES BEST. HAVE MINIMALLY UNDERCUT GUIDANCE. A DEGREE OR SO WARMER WEDNESDAY THEN NEARLY EVERYONE TO 50 OR BETTER THURSDAY...WITH POSSIBLE EXCEPTION OF THE NORTHEAST. FRIDAY AND SATURDAY HIGHS ABOVE NORMAL. NOT YET READY TO ACCEPT THE GFS SOLUTION OF CUTTING OFF A SURFACE LOW OVER THE GULF STATES SATURDAY AFTERNOON. PRESSURE GRADIENT MAY BE WEAKER AND HAVE LESS OF A DIRECT SOUTHERLY COMPONENT AND WARM ADVECTION MORE MUTED. NOT ENOUGH CONFIDENCE TO SWING TEMPERATURES ONE WAY OR THE OTHER AT THIS TIME AND FORECAST UNCHANGED. FORECAST LOWS LITTLE CHANGED. A WARMING TREND AFTER TONIGHT. LONG TERM (SATURDAY NIGHT THROUGH MONDAY)... LITTLE CHANGE TO CURRENT FORECAST. AS STATED ABOVE GFS SOLUTION NOT NECESSARILY CORRECT. SHOULD THE SURFACE LOW NOT PAN OUT...GFS PRECIPITATION SIGNIFICANTLY OVERDONE. OTHER MEDIUM RANGE MODELS SUGGEST AN UPPER LEVEL TROUGH THAT IS NOT QUITE AS DEEP AND A BIT MORE PROGRESSIVE. CURRENT PRECIPITATION FORECAST ENDING RAIN AT SUNSET SUNDAY FITS THE SCENARIO OF A MORE PROGRESSIVE UPPER TROUGH AND WILL LET STAND AS IS FOR NOW. TEMPERATURES SLIP BACK A BIT BEHIND EXITING TROUGH FOR MONDAY. AVIATION... HIGH PRESSURE WILL SETTLE OVER THE AREA FROM THE WEST AND NORTHWEST TODAY. WE CAN EXPECT VFR CONDITIONS THROUGH THE TAF PERIOD. CLEAR SKIES SHOULD PREVAIL EXCEPT FOR SOME CIRRUS OVER THE SOUTHEAST AND EASTERN TAFS DURING THE AFTERNOON AND EVENING. WINDS WILL BE OUT OF THE NORTHWEST AND NORTH AT LESS THAN 10 KNOTS...BECOMING CALM AFTER SUNSET. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...DJF nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ABERDEEN SD 925 AM CST TUE DEC 20 2005 PRETTY DENSE FOG BENEATH DECK OF LOW CLOUDS ASSOCIATED WITH THE COLD FRONT DROPPING SOUTHWEST INTO THE NORTHEASTERN CWA. THEREFORE UPDATED TO ISSUE A DENSE FOG ADVISORY ACROSS THE EASTERN HALF OF THE CWA. AS WAA KICK IN FROM THE WEST...AND AREA OF LOW CLOUDS BEGINS TO PUSH EAST AS A WARM FRONT SHOULD BEGIN TO SEE THE FOG AND SCATTERED FLURRIES DISSIPATE FROM WEST TO EAST. THEREFORE ONLY WENT WITH BROWN...MARSHALL...DAY...AND CLARK COUNTIES THROUGH 19Z...AND THE COUNTIES TO THE EAST SLIGHTLY LONGER UNTIL 22Z. ALSO LOWERED HIGHS SOMEWHAT ACROSS THE EAST WITH THE LOW CLOUDS AND FOG KEEPING TEMPERATURES FROM CLIMBING TO MUCH. OTHERWISE FORECAST LOOKS ON TRACK...SO MADE NO OTHER CHANGES. ...PREVIOUS DISCUSSION... .SHORT TERM...TODAY THROUGH 12Z FRIDAY. BIGGEST CHALLENGE IS CLOUD COVER WITHIN THE FIRST 12 HOURS OF THE FCST AND TEMPS FOR THE REMAINDER OF THE NEAR TERM. WIDESPREAD CLOUD SHIELD CONTS TO SLOWLY ADVANCE TOWARD CWA OUT OF ND. LEADING EDGE OF SHIELD LINES UP WELL WITH 925MB 85% RH LINE. QUESTION IS HOW FAR SOUTH AND WEST WILL CLOUDS PUSH BEFORE WAA PUSHES THEM BACK TO THE EAST? 06Z RUC/06Z HI RES NAM BOTH AGREE ON CLOUD DECK INTRUDING INTO NERN SD THROUGH 18Z BEFORE RETREATING BACK TO EAST. THIS WILL ALSO HAVE DRASTIC EFFECT ON TEMPS. IF SHIELD HANGS ON LONGER...NERN COUNTIES WILL NOT WARM TO FCST VALUES. IF SHIELD SCATTERS SOONER THAN ANTICIPATED...FCST TEMPS MAY BE UNDERDONE. SKY GRIDS GENERALLY FOLLOW HI RES NAM 85% RH 925MB RH LINE FOR BKN/OVC DECK. FLURRIES/LGT SNOW OCCURRING AT KGFK THIS MORNING AS WELL AS IN PARTS OF NRN MN...SO HAVE CONT MENTION OF FLURRIES FOR NERN CWA THROUGH THE MORNING HOURS. UPPER RIDGE CONTS TO BUILD BACK INTO THE UPPER MIDWEST BY 12Z WEDNESDAY. MODELS POINT TOWARD SEVERAL MINOR WAVES TOPPING RIDGE AND MOVING QUICKLY THROUGH REGION...BUT LITTLE IF ANY FORCING NOTED WITH ANY OF THEM. STRONGER WAVE TOPS RIDGE 12Z THURSDAY HELPING TO FLATTEN UPPER RIDGE AND PUTTING CWA INTO A MORE ZONAL FLOW REGIME. NEXT STRONGER WAVE PUSHES THROUGH CWA BEGINNING 06Z FRIDAY. THIS WAVE PUSHES A SFC TROF THROUGH THE AREA OVERNIGHT THURSDAY WITH GFS HINTING AT LIGHT QPF. NAM IS DRY. WILL CONT DRY FCST AS LOW LEVELS DON'T MOISTEN UP ALL THAT WELL. SFC WINDS BEHIND PASSING SFC TROFS MAINTAIN A WESTERLY DIRECTION HELPING TO KEEP WAA GOING ACROSS CWA. 85H TEMPS DON'T FALL BACK BELOW ZERO CELSIUS BY 12Z FRIDAY. OVERALL SHOULD BE DECENT WEATHER CONDITIONS HEADING INTO THE HOLIDAY WEEKEND. .LONG TERM...FRIDAY THROUGH MONDAY FORECAST CHALLENGE IN THE EXTENDED IS PRECIP POTENTIAL AND TYPE FRIDAY AFTERNOON/OVERNIGHT ALONG WITH TEMPS. WEST CONUS RIDGE GETS BEAT DOWN A HALF A DOZEN TIMES BETWEEN TODAY AND TUESDAY. BY FRIDAY...WAVE NUMBER 3 IS TRUDGING THROUGH WEAK MID-LEVEL RIDGE AND MAKING A CASE FOR SOME LIGHT MEASURABLE PRECIP...POTENTIALLY EITHER FREEZING RAIN OR SNOW...ACROSS CENTRAL AND NORTHEAST SODAK...NOTING 500HPA LIFT AND 700HPA FORCING AND MOISTURE IN ZONAL FLOW BETWEEN 21Z FRIDAY AND 09Z SATURDAY. ABBREVIATED PERIOD OF PRECIP POTENTIAL SEEMS REASONABLE GIVEN FAST NATURE OF MID/UPPER LEVEL FLOW. REMAINDER OF CWA SHOULD REFLECT RELATIVELY DRY BOUNDARY LAYER ENVIRONMENT...SO PERSISTED WITH DRY FORECAST BEYOND FRIDAY NIGHT. CAA SETS UP ACROSS CWFA ON FRIDAY AND PERSISTS THROUGH SATURDAY AS PER 925HPA THERMAL PROGS IN THE GFS AND EC. BY SUNDAY...WAA PATTERN SETS UP AS MID/UPPER LEVEL RIDGING RE-ESTABLISHES ITSELF ACROSS WESTERN HALF OF CONUS. AS A RESULT...CONTINUED WITH WARMING TREND ALREADY IN GRIDS FOR MONDAY. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...DENSE FOG ADVISORY FOR BROWN...DAY...MARSHALL...AND CLARK COUNTIES UNTIL 19Z TODAY. DENSE FOG ADVISORY FOR THE I-29 CORRIDOR COUNTIES UNTIL 22Z TODAY. MN...DENSE FOG ADVISORY FOR BIG STONE AND ROBERTS COUNTIES UNTIL 22Z TODAY. && $$ ALBRECHT/HINTZ/DORN sd AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 835 AM CST TUE DEC 20 2005 .DISCUSSION... HARD NOT TO IGNORE THAT THERE IS A LOT MORE NLY COMPONENT TO WNDS ON MORNING ABR RAOB AND WDL PROFILER THAN NAM/RUC WOULD SUGGEST AT LOW LVLS. COMBINE THIS WITH SATELLITE TRENDS...AND IT APPEARS THAT LOW CLOUDS WILL MAKE A PUSH FARTHER WWRD THAN GOING FCST. WITH STRENGTH OF INVERSION...SHOULD ALSO BE QUITE PERSISTENT WHERE THEY END UP...ESPLY ACRS ERN CWA. TMPS IN CLOUD BEARING LVR SUPPORT A FEW FLURRIES AS WELL...BUT FOR NOW WL LEAVE FOCUSED ALONG BUFFALO RIDGE. THEREFORE...WL BE LOWERING HIGH TMPS ACRS NERN CWA BY SEVERAL DEGREES...CLOSER TO WHAT RERADIATIVE VALUES WOULD SUGGEST GIVEN CURRENT SNOWCOVER. UPDATED GRIDS SENT...AND WL BE TWEEKING ZFP TEXT WITHIN THE HOUR. && .PREV DISCUSSION... BIG FCST FACTOR IS MASSV LOW CLD CVR CONTG TO APPCH FROM THE N. MODELS GRDLY WEAK MOIST LYR AS IT SPRDS IN FROM THE N THEN OUT TO THE E TDA...BUT EXPCT CLD CVR TO BE PRETTY SOLID FOR A WHILE NCNTRL NERN AND ECNTRL PARTS OF FCST AREA AS A RELTVLY SHLW LYR WILL STAY PRETTY MOIST. ASIDE FROM UNDERFCSTG SOLIDITY OF CLD CVR AND WEAKNG MOIST LYER TOO FAST...CLDS SPRDG IN THEN DCRG TO THE E SEEMS PRBLY WELL HANDLD. IN OTHER WORDS CLDS SHUD COME INTO MUCH OF THE N AND E THIS MRNG AND EXIT STEADILY THIS AFTN AND ERY EVE...BCMG PRETTY CLR AGN TNGT. REST OF FCST IS SIMPLER WITH NOT MUCH CHANGE AS WAA CONTS TO ASSERT ITSELF WITH MOCLR VERY GRDLY REPLACED BY SOME INCRS IN MID/HI CLDS. WARMNG LOOKS GOOD AFFECTED OF COURSE NY LINGRNG SNW CVR. WILL CONT TO CARRY CHC PCPN FRI NGT INTO SAT IN DEFRNCE TO STGR GFS ON SYS COMNG OVER RDG. A LTL COOLNG PSBL OVER THE WEEKEND BUT STILL VERY MILD COMPARED TO RECENT TIMES. WILL KEEP IT DRY AND MILD INTO ERY NEXT WEEK. TEMPTED TO WARM IT MORE THAN WE HAVE AS MODELS SHOW SOME WARMNG FROM ALREADY MILD TEMPS AND THERE SHUD BE A NOTICABLE DCRS IN SNW CVR BY THEN. WILL KEEP IT TAME IN VIEW OF ABV AND WEAK LATE DEC SUN AND LET DAY FCST EVALUATE WITH MORE INFO. WILLIAMS && .AVIATION... IFR CIGS ARE LKLY TO INUNDATE KRWF-KFSD PORTION OF TWB243 BETWEEN 15Z AND 17Z...WITH LAST TO FILL IN ARND KFSD AFT 18Z. EXPECT THAT WITH STRENGTH OF LOW LVL INVERSION...WL BE UP TO ADVECTION TO MOVE ARND CLDS...WHICH FAVOR MOVING WRN BNDRY TO NEAR KHON AND KFSD ARND 18Z. PERISHIBLE EDGE TO CLOUD SHIELD AND TURNING OF LOW LVL WNDS SHUD ALLOW DISSIPATION/CLEARING OF CLDS BTWN 20Z AND 22Z FROM KHON TO KFSD. .FSD WATCHES/WARNINGS/ADVISORIES... IA...NONE. MN...NONE. NE...NONE. SD...NONE. && $$ CHAPMAN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 900 PM CST TUE DEC 20 2005 .UPDATE...CLOUDS BLANKETED MUCH OF THE FORECAST AREA THIS EVENING...WITH FLURRIES STILL OCCURRING BENEATH THE CLOUDS. BASED ON LATEST RUC RELATIVE HUMIDITY PROFILES...AS WELL AS 11-3.9 MICRON SATELLITE IMAGERY...CLOUDS SHOULD REMAIN OVER THE AREA INTO THE OVERNIGHT HOURS BEFORE CLEARING. IN FACT...WE MAY BE TOO QUICK WITH CLEARING IN MUCH OF THE WI ZONES. THUS...UPDATED DATA BASE TO REFLECT LATEST TRENDS AND WILL UPDATE ZONES 0300-0330Z THIS EVENING. && THOMPSON .PREV DISCUSSION... .SHORT TERM...THROUGH THURSDAY NIGHT THE MAIN CONCERN IS WITH THE TEMPERATURES AND THEN PRECIPITATION CHANCES TOWARD THE END OF THE PERIOD. SURFACE ANALYSIS THIS AFTERNOON INDICATES A VERY WEAK COLD FRONT EXTENDED FROM THE LOWER PENINSULA OF MICHIGAN INTO CENTRAL WISCONSIN. HIGH PRESSURE WAS CENTERED OVER KANSAS WITH THE RIDGE AXIS NORTH INTO THE DAKOTAS. 12Z MODELS ARE PRESENTING VERY SIMILAR SOLUTIONS FOR THIS CYCLE FOR MUCH OF THE PERIOD. TOWARD THE END OF THE PERIOD THE GFS LOOKS A LITTLE BETTER WITH THE POSITION OF THE APPROACHING COLD FRONT THAN THE NAM. BAND OF THIN LOW CLOUDS ALONG THE COLD FRONT HAS BEEN SLOW TO PROGRESS SOUTH THIS AFTERNOON...BUT AT THE SAME TIME HAS BEEN HANGING TOUGH RIGHT ALONG THE FRONT ACROSS CENTRAL WISCONSIN INTO EASTERN MINNESOTA. WEAK SHORT WAVE TROUGH ASSOCIATED WITH THE FRONT WILL MOVE EAST OF THE REGION OVERNIGHT. THIS WILL ALLOW THE FLOW TO TURN MORE WESTERLY AND ALLOW SOME WARM AIR ADVECTION TO SET UP. THIS SHOULD ALSO ADVECT IN SOME DRIER AIR FROM THE WEST WHICH SHOULD ALLOW THE CLOUD COVER TO BREAK UP OVERNIGHT. HAVE ADJUSTED GRIDS TO GO WITH MORE CLOUDS THIS EVENING THAN PREVIOUS FORECAST AND THEN SHOW THE DECREASING TREND. TEMPERATURES TONIGHT EXPECTED TO BE HELD UP SOME INITIALLY BY THE CLOUDS AND THEN THE WARM AIR ADVECTION AND BUMPED THE FORECAST UP A COUPLE OF DEGREES. THE SURFACE RIDGE WILL REMAIN CENTERED SOUTH OF THE AREA TOMORROW BUT THE RIDGE AXIS IS EXPECTED TO SLIDE ACROSS THE FORECAST AREA. SHOULD SEE PLENTY OF SUNSHINE WITH THE GENERAL LOW MOISTURE LEVELS. WARM AIR ADVECTION PATTERN SHOULD CONTINUE AND WITH THE SLIGHTLY WARMER START AGAIN BUMPED TEMPERATURES UP A LITTLE. THE NEXT SHORT WAVE TROUGH WILL APPROACH WEDNESDAY NIGHT. MOISTURE LEVELS AND CLOUD COVER WILL INCREASE WITH THIS WAVE ALONG WITH THE WARM AIR ADVECTION. THERE IS SOME WEAK QG CONVERGENCE WITH THIS WAVE BETWEEN 1000 AND 700 MB ALONG WITH 2 MICROBARS/S OF UPGLIDE ON THE 285K SURFACE. HOWEVER...CONDENSATION PRESSURE DEFICITS ARE BETWEEN 50 AND 100 MB AND TIME/HEIGHT PLOTS SHOW THE ATMOSPHERE BELOW 600 MB DOES NOT SATURATE... SO NOT EXPECTING ANY PRECIPITATION TO OCCUR WITH THIS WAVE. THE NEXT WAVE WILL COME IN THURSDAY NIGHT AND LOOKS TO BE VERY SIMILAR TO THE WEDNESDAY NIGHT WAVE. THE LOWER LEVELS OF THE ATMOSPHERE LOOK TO HAVE A HARD TIME SATURATING WITH THE GFS SHOWING AROUND 1 MICROBARS/S OF UPGLIDE ON THE 285K ISENTROPIC SURFACE AND CONDENSATION PRESSURE DEFICITS OF 30 MB OR HIGHER. AGAIN ONLY WEAK QG CONVERGENCE IS SHOWN ACROSS THE EASTERN SECTIONS OF THE FORECAST AREA. IF PRECIPITATION DOES DEVELOP WITH THIS SYSTEM...THE TYPE WILL BE A CONCERN. THE PROLONGED WARM AIR ADVECTION AHEAD OF THIS WAVE WILL HAVE ALLOWED 850 MB TEMPERATURES TO PUSH WELL ABOVE ZERO WITH THE GFS SHOWING VALUES OF +3-5C BY 12Z FRIDAY. FOR NOW WILL MAINTAIN THE DRY FORECAST THINKING THE FORCING WILL NOT BE STRONG ENOUGH TO ALLOW SATURATION TO OCCUR. LATER SHIFTS WILL HAVE TO MONITOR THESE TRENDS AND BE READY TO INCLUDE SOME FREEZING RAIN/DRIZZLE IF IT BECOMES NECESSARY. .LONG TERM...FRIDAY THROUGH TUESDAY MEDIUM RANGE MODELS TODAY STARTING TO SHOW SOME VARIABILITY IN THEIR SOLUTIONS. THE 00Z OPERATIONAL RUN OF THE GFS IS SIMILAR TO THE ECMWF BUT BY THE END OF THE WEEKEND AND EARLY NEXT WEEK IS SHOWING SOME DIFFERENCES WITH THE STRENGTH AND POSITION OF THE EASTERN CONUS LONG WAVE TROUGH. GFS ENSEMBLE MEMBERS DO NOT EXHIBIT A LOT OF SPREAD WITH THIS SOLUTION AND FOR THIS CYCLE HAVE LEANED TOWARD THE GFS SOLUTION. SHORT WAVE TROUGH THAT HELPS TO FLATTEN THE MEAN RIDGE OVER THE WESTERN CONUS WILL COME ACROSS THE UPPER MIDWEST FRIDAY INTO EARLY SATURDAY. ANOTHER WEAK SYSTEM IS EXPECTED TO RIDE ACROSS THE AREA SUNDAY NIGHT INTO MONDAY. PREVIOUS FORECAST SEEMED TO CAPTURE THE TIMING OF THESE EVENTS SO ONLY MINOR ADJUSTMENTS MADE TO THE PREVIOUS FORECAST. SOME CONCERN ABOUT PRECIPITATION TYPE FOR FRIDAY AS SURFACE TEMPERATURES WILL BE NEAR FREEZING. RIGHT NOW THE GFS BUFKIT SOUNDINGS INDICATE THAT WITH THE WARM AIR ALOFT...THERE IS THE POTENTIAL FOR A LITTLE FREEZING PRECIPITATION BUT IT LOOKS TO BE SHORT LIVED AND WITH A LACK OF CONFIDENCE IN THIS SOLUTION AT THIS TIME...WILL NOT INCLUDE IN THE FORECAST. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ 04 wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 355 AM EST WED DEC 21 2005 .SHORT TERM... TODAY AND TONIGHT... ONCE AGAIN SKY COVER AND TEMPERATURES ARE THE FORECAST CHALLENGES FOR THE SHORT TERM PERIOD. SATELLITE SHOWS LOW STRATUS ERODING FROM WEST TO EAST ACROSS FORECAST AREA AT ISSUANCE TIME. CHALLENGE IS WHEN AND WHERE EROSION WILL END AND HOW TO PLAY SKY COVER FOR TODAY. DESPITE MISSING INGEST OF UPPER AIR DATA...00Z NAM40 IS DOING QUITE WELL MODELING CLOUD COVER IN THE VICINITY OF 925MB LEVEL WITH ITS RH FIELD. IT BRINGS DRIER AIR INTO CENTRAL AND SOUTHERN FORECAST AREA FOR A FEW HOURS THIS MORNING BEFORE BRINGING MOISTURE BACK AHEAD OF FAST MOVING SHORT WAVE SEEN IN WATER VAPOR DROPPING SOUTH THROUGH MICHIGAN. RUC40 THROUGH THE MORNING HOURS IS LESS PESSIMISTIC WITH ITS 925MB RH FIELD. THERE DOES APPEAR TO AT LEAST BE SOME MID OR HIGH LEVEL CLOUDS ACROSS WISCONSIN ASSOCIATED WITH THIS SHORT WAVE. THEREFORE PLAN TO HAVE PARTIAL CLEARING EARLY THIS MORNING WESTERN AREAS THEN INCREASE CLOUDS AGAIN BY MID MORNING NORTHWEST. WILL KEEP SOUTHWEST PARTLY CLOUDY. HAVE KEPT EASTERN AREAS MOSTLY CLOUDY WITH SOME DECREASE LATE THIS AFTERNOON BEHIND SHORT WAVE. STRONG SUBSIDENCE AND CONTINUED DRYING TONIGHT WILL SCOUR OUT MOST CLOUDS. HAVE TRENDED GRIDS TO BETWEEN 30 AND 40 PERCENT FOR NOW TO ACCOUNT FOR POSSIBLE SLOWER MOVEMENT OF CLOUDS. HAVE ALSO ADDED SOME PATCHY FREEZING FOG TO THIS MORNING AS UPSTREAM OBSERVATIONS HAVE SHOWN SOME PATCHY BR IN THE 3 TO 5 MILE RANGE FORM WHERE SKIES HAVE CLEARED AND WINDS RELAXED. AS FOR TEMPERATURES...DID DROP MAX TEMPS A DEGREE OR TWO TODAY WITH MORE CLOUDS AND COOLER MOS GUIDANCE. DESPITE WARM AIR ADVECTION ALOFT TONIGHT...ONE MORE NIGHT OF COLD TEMPERATURES STILL POSSIBLE WITH CLEARING SKIES AND WINDS UNDER 10KTS. && .LONG TERM... THURSDAY THROUGH TUESDAY...FINALLY APPEARS TO BE A BREAK OUT OF THE DEEP FREEZE AS THE FLOW BECOMES HIGH ZONAL. THE UPPER LEVEL RIDGE OVER WESTERN NORTH AMERICA WILL BREAK DOWN PER NCEP...ECMWF AND CANADIAN MODEL CONSENSUS. OVER THE MIDWEST...THE RETURN FLOW INCREASES THURSDAY WITH A TIGHT PRESSURE GRADIENT DEVELOPING BETWEEN THE 1025 MB SFC HIGH OVER THE SE CONUS AND THE DEEP LOW NORTH OF THE GREAT LAKES. THE NAM AND NGM APPEAR TOO ROBUST WITH THE WARM UP THURSDAY...THE NGM FWC MOS HIGH OF 44 IS 9 DEGREES WARMER THAN THE MAV HIGH OF 35 AT FWA. GIVEN SNOW COVER OVER THE FORECAST AREA OF GENERALLY 4-8 INCHES...WENT WITH THE MORE CONSERVATIVE MAV. WILL BE HARD TO MIX MUCH OF THE WARM AIR DOWN TO THE SURFACE. A WEAK SHORT WAVE SHOULD MOVE ACROSS THE AREA EARLY FRIDAY...SO HAVE KEPT A CHANCE FOR RAIN SHOWERS IN THE GRIDS/ZFP OVER NORTH AREA INCLUDING FAR SOUTHERN LOWER MICHIGAN. ISENTROPIC ANALYSIS STILL FAVORS LOWER MICHIGAN FOR THE BEST CHANCE FOR PRECIPITATION PER UPGLIDE AND SATURATION ON THE 300K SFC. THE NEXT SYSTEM POISED TO EFFECT THE WEATHER THIS WEEKEND APPEARS MUCH STRONGER THAN THE FRIDAY SYSTEM. THE ECMWF SHOWED SOME CONSISTENCY FROM THE 20/00Z RUN WITH THIS UPPER LOW DROPPING INTO THE GREAT LAKES REGION. THE GFS HAS TRENDED THIS SYSTEM STRONGER DURING THE SAME PERIOD. THE CAVEAT IS THE PAST MODEL HANDLING OF DIGGING THIS TYPE OF SYSTEM TOWARD THE SOUTHERN STREAM. EXPECT A SLOWER SOLUTION THAT WHAT IS EVEN NOW ADVERTISED BY THE GFS AND THE ECMWF. FOR THIS PACKAGE...KEPT CHANCE POPS SATURDAY THROUGH SUNDAY WITH THE ARRIVAL OF THIS SYSTEM. POTENTIAL STILL FOR ACCUMULATING SNOW...ESPECIALLY SATURDAY NIGHT. AN EVEN SLOWER AND STRONGER SOLUTION WOULD SUPPORT ACCUMULATING SNOW INTO SUNDAY. HAVE RAISED POPS TO 50 PERCENT SATURDAY NIGHT...BUT HESITANT TO MAKE CHANGES PAST SATURDAY NIGHT GIVEN WIDE VARIETY OF POSSIBLE SOLUTIONS AND THE POTENTIAL FOR A STRONGER AND SLOWER SYSTEM. FOR MONDAY AND TUESDAY...THE CANADIAN ENSEMBLES SUPPORT A CONTINUANCE OF THE HIGH ZONAL FLOW WITH MILD TEMPERATURES...ALTHOUGH MULTIPLE SHORTWAVES WILL BE MIGRATING ACROSS THE CONUS. KEPT THE FORECAST DRY MONDAY AND TUESDAY. && .AVIATION... SATELLITE DERIVED FOG PRODUCT SHOWING LOW STRATUS DECK NICELY. TRENDS LAST FEW HOURS HAVE SHOWN EROSION ACROSS WESTERN EDGE AND INTO NORTHWEST INDIANA AS DRIER AIR AROUND 925MB ADVECTS IN. GENERALLY FOLLOWED 00Z NAM40 925MB RH PATTERN FOR CLOUD TRENDS WITH THIS PACKAGE SINCE IT HAS THE AREA HANDLED WELL AT 03Z. THIS MEANS KSBN SHOULD SEE THE CLOUDS TEMPORARILY SCOUR OUT SHORTLY. UPSTREAM OBSERVATIONS SUGGEST MVFR BR TO FORM SHORTLY AFTER SKIES CLEAR. HAVE ADDED THIS TO KSBN OVERNIGHT AND WILL MONITOR. IF CLEARING DOES WORK THROUGH KSBN AND PERSISTS...LOWER VIS RESTRICTION MAY BE NEEDED. AT KFWA...CLEARING A LITTLE MORE IN QUESTION. 925MB LOWER RH DOES MAKE IT TO KFWA BY 12Z BUT APPROACH OF FAST MOVING SHORT WAVE FROM THE NORTH BRINGS THE HIGHER RH RIGHT BACK IN DURING THE MORNING AS WINDS TURN BACK MORE NORTHWEST. HAVE BEEN A BIT MORE PESSIMISTIC HERE AND KEPT MVFR CIGS...THOUGH A FEW HOURS OF SCT CLOUDS IS POSSIBLE TOWARD DAYBREAK. PREVIOUSLY MENTIONED SHORT WAVE WILL BRING LOWER CLOUDS BACK TO BOTH SITES DURING THE DAY...FOLLOWED BY CLEARING AGAIN LATE AFTERNOON OR EARLY EVENING. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM/AVIATION...LASHLEY LONG TERM....SKIPPER in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WICHITA KS 1031 PM CST TUE DEC 20 2005 .UPDATE... MAKING A FEW MINOR CHANGES TO THE CURRENT ZONE PACKAGE. JUST MADE SOME PHONE CALLS TO AREAS ALONG AND WEST OF HIGHWAY 14 IN THE WESTERN PORTIONS OF CENTRAL KANSAS. THEY ARE NOW REPORTING IMPROVED VISIBILITY. THIS IS DUE TO GOOD SUBSIDENCE AND FROST DEPOSITION BUILDING BEHIND THIS LOW STRATUS DECK. AS A RESULT, WE ARE UPDATING TO REMOVE THE FREEZING FOG ADVISORY FOR PORTIONS OF CENTRAL KANSAS. IF THIS CLEARING TREND CONTINUES EAST, WE MAY END UP CANCELING THE FREEZING FOG ADVISORY ACROSS THE REMAINDER OF CENTRAL AND SOUTH CENTRAL KANSAS BY DAYBREAK, AND THEN POSSIBLY STRETCH IT INTO SOUTHEAST KANSAS. FOR NOW, WE WILL LET LATER SHIFTS EVALUATE. COX && .PREV DISCUSSION... /ISSUED 824 PM CST TUE DEC 20 2005/ UPDATE... MAIN CONCERN FOR AVIATION USERS TONIGHT WILL BE THE POTENTIAL FOR DENSE FREEZING FOG TONIGHT. WE MADE SEVERAL CALLS TO COUNTIES BEHIND THE STRATUS DECK AND THEY ARE ALREADY REPORTING DENSE FOG. LATEST FOG IMAGERY SHOWING THE LOW CLOUD PROGRESSION COMING TO A HALT OVER THE AREA. AFTER EXAMINING THE RUC 275K THETA SURFACE THERE IS VERY LITTLE IN THE WAY OF DOWNGLIDE TAKING PLACE ACROSS CENTRAL AND SOUTH CENTRAL KANSAS. THE RUC/ETA ARE BOTH SHOWING THIS TREND CONTINUING OVERNIGHT. WITH THAT IN MIND... WE WENT AHEAD AND ISSUED A DENSE FOG FREEZING FOG ADVISORY FOR ALL OF CENTRAL AND SOUTH CENTRAL KANSAS. I WOULD EXPECT THE FOG TO BUILD EAST AS THE NIGHT PROGRESSES AS CEILINGS CONTINUE TO LOWER ACROSS SOUTH CENTRAL KANSAS...DUE TO THE STRATUS BUILD DOWN EFFECT. COX && PREV DISCUSSION... /ISSUED 604 PM CST TUE DEC 20 2005/ AVIATION... MAIN CONCERN FOR AVIATION USERS TONIGHT WILL BE THE POTENTIAL FOR LOW INSTRUMENT FLIGHT RATING CONDITIONS TONIGHT. LATEST FOG IMAGERY SHOWING THE LOW CLOUDS SLOWLY PUSHING EAST. AFTER EXAMINING THE RUC 275K THETA SURFACE THERE IS VERY LITTLE IN THE WAY OF DOWNGLIDE TAKING PLACE ACROSS SOUTH CENTRAL KANSAS. THE RUC/ETA ARE BOTH SHOWING THIS TREND CONTINUING THROUGH THE EVENING. WITH THAT IN MIND... WE ARE GETTING CONCERNED ABOUT THE LOW CLOUD DECK SLOWING DOWN ITS PROGRESSION WHICH WOULD BRING FORTH THE RISK OF DENSE FOG DEVELOPMENT WITHIN THE REGION THAT HAS CEILINGS BELOW 1KFT. ANOTHER CONCERN IS THE AREA JUST BEHIND THIS LOW CLOUD DECK WHERE THE BOUNDARY LAYER IS STILL RATHER SATURATED. THIS AREA IS MAINLY CONFINED TO JUST ALONG AND EAST OF A HUTCHINSON TO SALINA LINE TO AREAS ALONG AND WEST OF A WINFIELD TO EMPORIA LINE. THE AREAS WHERE THE CEILINGS ARE BELOW 1KFT HAVE A PRETTY GOOD SHOT OF SEEING STRATUS BUILD DOWN DUE TO SNOW COVER AND POTENTIAL FOR FOG TOP COOLING FROM CLEAR SKIES ABOVE THE STRATUS DECK. MEANWHILE... AREAS JUST BEHIND THE CLEARING LINE MAY HAVE THE POTENTIAL FOR MORE SHALLOW PATCHY DENSE FOG... DUE TO MORE DEPOSITION AND SUBSIDENCE. WE WILL CONTINUE TO MONITOR THE PROGRESSION OF THE LOW CLOUDS FOR NOW AND POSSIBLY ISSUE A HEADLINE DURING THE NEXT COUPLE OF HOURS. TIMING OF THE DENSE FOG COULD BE LATE THIS EVENING OR JUST AFTER MIDNIGHT. && COX && PREV DISCUSSION... /ISSUED 319 PM CST TUE DEC 20 2005/ DISCUSSION... FORECAST CONCERN/CHALLENGE IS LOW CLOUDS AND FOG POTENTIAL TONIGHT. THEREAFTER, EXTENT AND MAGNITUDE OF POTENTIALLY SIGNIFICANT WARMING TREND WILL BE THE MAIN FOCUS. TONIGHT: LOW STRATUS HAS BEEN MUCH SLOWER TO CLEAR OUT THAN EXPECTED, AND THIS TREND SHOULD CONTINUE TONIGHT. WEAK LOW-LEVEL TROUGH WILL PROGRESS SOUTHEAST ACROSS THE CWA TONIGHT, HELPING TO CLEAR THE CLOUDS FROM NORTHWEST TO SOUTHEAST THROUGH THE OVERNIGHT HOURS. THINKING FOG POTENTIAL WILL BE GREATEST JUST BEHIND THE CLEARING LINE OVER SNOW COVER, WHERE DEWPOINTS SHOULD BE HIGHER AND RADIATIONAL COOLING GREATEST. LATEST LAPS SOUNDINGS INDICATE FAIRLY DEEP LOW-LEVEL MOISTURE ACROSS THE EASTERN 2/3 OF THE CWA, SO ENOUGH MOISTURE SHOULD BE PRESENT FOR FOG EVEN AFTER FULL RADIATIONAL COOLING/DRYING. ONLY POTENTIAL MITIGATING FACTOR WILL BE LIGHT WESTERLY DOWNSLOPE FLOW, SO DID NOT MENTION DENSE FOG FOR NOW. HOWEVER, EVENING SHIFT WILL NEED TO KEEP A CLOSE EYE ON THE SITUATION. WEDNESDAY-FRIDAY: SIGNIFICANT WARMING TREND EXPECTED THIS PERIOD, AS WESTERN RIDGE FLATTENS IN RESPONSE TO SHORTWAVE ENERGY PROGRESSING THROUGH THE EASTERN PACIFIC. CONSEQUENTLY, ZONAL FLOW ALOFT WILL SET UP, SPREADING A RELATIVELY MILD PACIFIC AIRMASS ACROSS ESSENTIALLY THE ENTIRE CONUS. AS PREVIOUS FORECASTER ALLUDED TO, SUN'S ENERGY WILL GO TOWARD MELTING THE 2-5 INCH SNOWPACK ACROSS THE AREA, BUT THINKING SNOW WILL BE COMPLETELY MELTED BY FRIDAY, WITH QUITE A BIT OF IT LIKELY ALREADY MELTED BY THURSDAY. SATURDAY-MONDAY: MODELS ARE INDICATING A COOL DOWN FOR SATURDAY AND SUNDAY, AS A RATHER POTENT SHORTWAVE DROPS SOUTHEAST ACROSS THE MIDWEST. THE 20/12Z GFS SOLUTION IS BY FAR THE OUTLIER, AMPLIFYING THE TROUGH MUCH DEEPER AND FARTHER WEST THAN THE ETA, ECMWF, CANADIAN, UKMET AND NCEP ENSEMBLE MEAN. CONSEQUENTLY, DID NOT COOL TEMPERATURES TO THE EXTENT THAT THE GFS SUGGESTED. INSERTED SLIGHT CHANCE OF LIGHT RAIN ON SATURDAY TO ACCOUNT FOR PASSING SHORTWAVE. BY MONDAY ALL MODELS ARE INDICATING ANOTHER SIGNIFICANT WARMING TREND ACROSS THE AREA, AS WESTERN RIDGE BUILDS AND EASTERN TROUGH MOVES EAST. 00Z NCEP GFS ENSEMBLES (SPAGHETTI PLOTS) HAVE AMAZING AND ALMOST UNPRECEDENTED AGREEMENT WITH THIS WARMING TREND EVEN AT 168 HOURS OUT. ECMWF IS ALSO CLOSE TO THESE SOLUTIONS. WENT RATHER CONSERVATIVE IN THE FORECAST FOR NOW, AND ONLY WENT WITH 50S-LOW 60S. HOWEVER, GIVEN WARM 850 MB TEMPERATURES AND TAKING INTO ACCOUNT ONLY MARGINAL MIXING MAY YIELD HIGH TEMPERATURES WELL INTO THE 60S. COULD BE FLIRTING WITH RECORD HIGHS, WHICH GENERALLY RANGE FROM 65-70 DEGREES. KLEINSASSER && PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 17 43 26 56 / 0 0 0 0 HUTCHINSON 15 41 24 53 / 0 0 0 0 NEWTON 15 41 24 53 / 0 0 0 0 ELDORADO 18 42 25 55 / 0 0 0 0 WINFIELD-KWLD 19 47 27 59 / 0 0 0 0 RUSSELL 13 40 22 51 / 0 0 0 0 GREAT BEND 14 41 23 52 / 0 0 0 0 SALINA 10 39 21 51 / 0 0 0 0 MCPHERSON 13 40 23 51 / 0 0 0 0 COFFEYVILLE 21 47 27 59 / 0 0 0 0 CHANUTE 21 44 26 56 / 0 0 0 0 IOLA 20 42 26 55 / 0 0 0 0 && .ICT WATCHES/WARNINGS/ADVISORIES... FREEZING FOG ADVISORY UNTIL 10 AM WEDNESDAY FOR KSZ049-051>053- 067>069-082-083-091>093. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOUISVILLE KY 1216 AM EST WED DEC 21 2005 .SHORT TERM (THIS MORNING)... WELL...CHALLENGING 1ST PERIOD OF THE FORECAST WITH LOW CLOUDS OVER THE BUCKEYE STATE AND ALSO OVER FAR WESTERN KY (WEST OF PAH) EXTENDING S INTO THE WRN 1/3 OF THE VOLUNTEER STATE. LOOKING AT THE 11-3.9 MICRON SATELLITE LOOP...SOME LOW CLOUDS ARE TRYING TO FORM IN THE MIDDLE OF THE 2 CLOUD FIELDS...BUT NOTHING WIDESPREAD YET. THE ETA AND AVN DO NOT HAVE A HANDLE ON THE LOW CLOUDS ALONG THE OHIO RIVER NEAR CIN AND EXTENDING BACK INTO THE WEST CENTRAL PORTION OF THE HOOSIER STATE. . HOWEVER THE RUC SEEMS TO HAVE THE BEST HANDLE WITH THE I280K LAYER SHOWING SOME WEAK UPGLIDE OVER THE CWA. WILL TWEAK THE GRIDS A LITTLE BIT...AND BUT NO ZFP/PFM UPDATE YET... AND WILL KEEP M/CLEAR GOING FOR THE MOMENT. && LMK WATCHES/WARNINGS/ADVISORIES... .IN...NONE. .KY...NONE. && $$ JDG ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 335 AM EST WED DEC 21 2005 .SHORT TERM (TODAY THROUGH FRIDAY)... LOW CLOUDS WERE ENTRENCHED ACROSS MUCH OF THE AREA THIS MORNING...WITH CLEARING SKIES IN SW OHIO...KY AND INDIANA. AS THE MORNING PROGRESSES...CLOUDINESS WILL DECREASE FROM THE WEST AND SW. LOOKING AT TEMPS YESTERDAY TO THE WEST...AND CONSIDERING THE WARM START FROM THE OVERNIGHT CLOUDS...TEMPS WILL RANGE FROM THE UPPER 20S TO MID 30S NORTH TO SOUTH. OVERNIGHT LOWS WILL FALL BACK INTO THE TEENS TO LOWER 20S. CONDITIONS WILL REMAIN DRY THROUGH THURSDAY...WITH A STEADY WARMING TREND AS THE HIGH PRESSURE MOVES EAST. AN UPPER DISTURBANCE/SFC TROF WILL PASS ACROSS THE AREA FRIDAY...AND SLIGHT TO CHANCE POPS LOOK REASONABLE AT THIS JUNCTURE. && PREVIOUS DISCUSSION... (ISSUED 1242 AM EST WED DEC 21 2005) AVIATION... SATELLITE IMAGERY SHOWS LOW CLOUDS ACROSS MUCH OF THE AREA. ALTHOUGH AFTER REACHING KCVG THEY HAVE STARTED RETREATING TOWARDS THE NORTHEAST. ALSO CLEARING HAS STARTED WORKING ACROSS CENTRAL INDIANA FROM WEST TO EAST. EXTRAPOLATION OF CLEARING TRENDS FOLLOWS CLOSELY WITH LATEST RUC FORECAST. SO HAVE USED THIS AS A GUIDE. DO NOT EXPECT MUCH CHANGE IN THE AREAL EXTENT OF THE MVFR CEILINGS UNTIL CLOUDS DIMINISH. THIS SHOULD OCCUR TOWARDS DAYBREAK AT KDAY AND KILN WHILE IT WILL BE LATER IN THE MORNING IN THE COLUMBUS AREA. AFTER LOWER CLOUDS CLEAR DO NOT EXPECT ANY FURTHER AVIATION CONCERNS THROUGH THE END OF THE FORECAST PERIOD. PREVIOUS DISCUSSION... (ISSUED 315 PM EST TUE DEC 20 2005) LONG TERM (FRIDAY NIGHT THROUGH TUESDAY)... LONG TERM (FRIDAY THROUGH TUESDAY)... SOME GOOD AGREEMENT BEING SHOWN ON THE MODELS WITH THE UPCOMING FORECAST PERIOD. L/W TROF OVER ERN U.S. WILL BRING A PERIOD OF UNSETTLED WX TO THE OHVLY BEGINNING SAT AND LASTING THROUGH THE EARLY PART OF NEXT WEEK. OCCLUDED LOW IS BEING FORECAST OVER THE GTLKS REGION AND A SERIES OF H5 S/W'S AND CLIPPERS STREAMING INTO THE GTLKS FROM THE NW. SFC HIGH SE OF FCST AREA ON FRI WILL CONTINUE TO SLOWLY MOVE THIS DIRECTION AND RETURN FLOW SETS UP OVER OHVLY THROUGH THE DAY AND INTO THE OVERNIGHT HOURS. WARM SECTOR SHOWERS ARE A POSSIBILITY IN THE N LATE IN THE DAY AS A WEAK H5 S/W TRANSITIONS ACROSS THE SRN GTLKS. NO SIGNIFICANT FORCING NOTED HERE SO I'VE KEPT POPS AROUND THE 20% RANGE. THIS WAVE QUICKLY MOVES THROUGH AND SFC FEATURES ARE SHOWING THAT THE WARM SECTOR CONTINUES THROUGH EARLY SAT. CDFNT W OF FCST AREA SAT WILL BRING AN INCREASED CHANCE FOR PRECIP DURING THE DAY AND AGAIN OVERNIGHT AS THE FRONT PASSES OVER OHIO. EXPECT A CHANGEOVER ON THE BACK SIDE OF THE H5 AND SFC FRONT BUT CANNOT RULE OUT THAT A SLIGHTLY WARMER SOLUTION IS POSSIBLE. HAVE GENERALLY RAIN AND SNOW AS A POSSIBILITY FOR SAT NIGHT...MAINLY RAIN IN THE SOUTHEAST. KEPT SUN FORECAST AS SNOW WITH TEMPS IN THE MID 30S...SOME UPPER 30S IN THE SOUTH. BELIEVE THAT PRECIP WILL TURN OFF FROM W-E EARLY WITH COLD POOL SHSN AND FLURRIES. NEW 12Z GFS BOMBS OUT THE SFC LOW AND H5 LOW...BRINGING AN ENTIRELY DIFFERENT SOLUTION TO MUDDY UP THE WATERS. HAVE CHOSEN TO THROW THIS OUT AS SPURIOUS BUT ALSO INCREASED POPS SLIGHTLY TO ACCOUNT FOR THE POSSIBILITY. BELIEVE THAT THE H5 L/W TROF WILL SLIDE SLOWLY EAST OVER THE WEEKEND AND NOT STALL JUST W OF FCST AREA. FRANKS && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SHORT TERM... LONG TERM... AVIATION... oh AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 1242 AM EST WED DEC 21 2005 .AVIATION (06Z-06Z)... SATELLITE IMAGERY SHOWS LOW CLOUDS ACROSS MUCH OF THE AREA. ALTHOUGH AFTER REACHING KCVG THEY HAVE STARTED RETREATING TOWARDS THE NORTHEAST. ALSO CLEARING HAS STARTED WORKING ACROSS CENTRAL INDIANA FROM WEST TO EAST. EXTRAPOLATION OF CLEARING TRENDS FOLLOWS CLOSELY WITH LATEST RUC FORECAST. SO HAVE USED THIS AS A GUIDE. DO NOT EXPECT MUCH CHANGE IN THE AREAL EXTENT OF THE MVFR CEILINGS UNTIL CLOUDS DIMINISH. THIS SHOULD OCCUR TOWARDS DAYBREAK AT KDAY AND KILN WHILE IT WILL BE LATER IN THE MORNING IN THE COLUMBUS AREA. AFTER LOWER CLOUDS CLEAR DO NOT EXPECT ANY FURTHER AVIATION CONCERNS THROUGH THE END OF THE FORECAST PERIOD. && .PREVIOUS DISCUSSION... (ISSUED 1006 PM EST TUE DEC 20 2005) SHORT TERM (TONIGHT)... NWRLY UPPER LEVEL FLOW TO CONTINUE ACRS OH VALLEY WITH MEAN TROF OVER THE EASTERN US. MAIN S/W PASSING THRU THE EASTERN GREAT LAKES REMAINS WELL E OF THE FA WITH VORT TAIL DROPPING THRU OHIO. SATL IMGRY SHOWS LOW LEVEL CLOUDS ENCROACHING FA AND EXPANDING. THESE CLOUDS ARE TRAPPED BELOW A LOW LEVEL INVERSION WHICH IS STRENGTHENING AS WAA INCREASES AT 8H. HAVE BUMPED UP SKY COVER INTO MOSTLY CLOUDY CATEGORY TO ACCOUNT FOR THESE CLOUDS AND BUMPED UP OVERNIGHT LOWS A COUPLE OF DEGREES. PREVIOUS DISCUSSION... (ISSUED 315 PM EST TUE DEC 20 2005) SHORT TERM (TONIGHT THROUGH THURSDAY NIGHT)... UPPER TROUGH OVER THE EASTERN CONUS REMAINS THE DOMINANT WEATHER FEATURE AS IT HAS BEEN SINCE NOVEMBER 30TH. AFTER TROUGH AXIS PASSES THROUGH ILN TONIGHT...AREA WILL EXPERIENCE HEIGHT RISES THROUGH THE REST OF THE SHORT TERM AS THE UPPER TROUGH FLATTENS. HIGH PRESSURE AT THE SURFACE WILL KEEP THE AREA PRECIPITATION FREE. MODEL SOUNDINGS INDICATE THAT THE BOUNDARY LAYER WILL MOISTEN UP TONIGHT WITH MOISTURE TRAPPED BELOW A LOW LEVEL INVERSION. SATELLITE AND OBSERVATIONS ARE SHOWING SOME EVIDENCE THAT THIS MAY VERIFY WITH CLOUDS APPROACHING FROM ILLINOIS. THEREFORE HAVE INCREASED CLOUD COVER TONIGHT THROUGH WEDNESDAY AFTERNOON AND AGAIN ON WEDNESDAY NIGHT TO THURSDAY AFTERNOON. WITH HIGH PRESSURE MOVING EAST AND A SOUTHERLY FLOW DEVELOPING... TEMPERATURES WILL APPROACH CLIMATOLOGICAL NORMALS ON THURSDAY. DAYTON AND THE NORTHERN MIAMI VALLEY WILL BE SLOWEST TO MODERATE SINCE THERE IS SIGNIFICANT SNOW PACK THERE. IN ANY CASE...THE NEXT ABOVE NORMAL READING AT CINCINNATI...DAYTON OR COLUMBUS WILL BE THE FIRST THIS MONTH. CONIGLIO (ISSUED 315 PM EST TUE DEC 20 2005) LONG TERM (FRIDAY THROUGH TUESDAY)... SOME GOOD AGREEMENT BEING SHOWN ON THE MODELS WITH THE UPCOMING FORECAST PERIOD. L/W TROF OVER ERN U.S. WILL BRING A PERIOD OF UNSETTLED WX TO THE OHVLY BEGINNING SAT AND LASTING THROUGH THE EARLY PART OF NEXT WEEK. OCCLUDED LOW IS BEING FORECAST OVER THE GTLKS REGION AND A SERIES OF H5 S/W'S AND CLIPPERS STREAMING INTO THE GTLKS FROM THE NW. SFC HIGH SE OF FCST AREA ON FRI WILL CONTINUE TO SLOWLY MOVE THIS DIRECTION AND RETURN FLOW SETS UP OVER OHVLY THROUGH THE DAY AND INTO THE OVERNIGHT HOURS. WARM SECTOR SHOWERS ARE A POSSIBILITY IN THE N LATE IN THE DAY AS A WEAK H5 S/W TRANSITIONS ACROSS THE SRN GTLKS. NO SIGNIFICANT FORCING NOTED HERE SO I'VE KEPT POPS AROUND THE 20% RANGE. THIS WAVE QUICKLY MOVES THROUGH AND SFC FEATURES ARE SHOWING THAT THE WARM SECTOR CONTINUES THROUGH EARLY SAT. CDFNT W OF FCST AREA SAT WILL BRING AN INCREASED CHANCE FOR PRECIP DURING THE DAY AND AGAIN OVERNIGHT AS THE FRONT PASSES OVER OHIO. EXPECT A CHANGEOVER ON THE BACK SIDE OF THE H5 AND SFC FRONT BUT CANNOT RULE OUT THAT A SLIGHTLY WARMER SOLUTION IS POSSIBLE. HAVE GENERALLY RAIN AND SNOW AS A POSSIBILITY FOR SAT NIGHT...MAINLY RAIN IN THE SOUTHEAST. KEPT SUN FORECAST AS SNOW WITH TEMPS IN THE MID 30S...SOME UPPER 30S IN THE SOUTH. BELIEVE THAT PRECIP WILL TURN OFF FROM W-E EARLY WITH COLD POOL SHSN AND FLURRIES. NEW 12Z GFS BOMBS OUT THE SFC LOW AND H5 LOW...BRINGING AN ENTIRELY DIFFERENT SOLUTION TO MUDDY UP THE WATERS. HAVE CHOSEN TO THROW THIS OUT AS SPURIOUS BUT ALSO INCREASED POPS SLIGHTLY TO ACCOUNT FOR THE POSSIBILITY. BELIEVE THAT THE H5 L/W TROF WILL SLIDE SLOWLY EAST OVER THE WEEKEND AND NOT STALL JUST W OF FCST AREA. FRANKS && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ oh AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI 225 AM CST WED DEC 21 2005 .DISCUSSION...FORECAST FOCUS ON CLOUD DECK AND FOG TODAY...WARMER TEMPERATURE TREND...PRECIPITATION CHANCES AND TYPE FRIDAY AND SATURDAY. STUBBORN LOW CLOUD DECK HANGING AROUND IN MAINLY THE NORTHERN HALF OF THE FORECAST AREA. THE DECK IS STUCK UNDER A STRONG TEMPERATURE INVERSION PER RUC FORECAST SOUNDINGS. AREAS OF FOG ALSO SEEN UNDER STRONG INVERSION ACROSS THE FORECAST AREA. RUC AND NAM FORECAST SOUNDINGS ACROSS THE FORECAST AREA INDICATE THAT THE INVERSION SHOULD HOLD DURING THE MORNING HOURS...BEFORE FINALLY MIXING OUT IN THE AFTERNOON. SO...WILL GO MOSTLY CLOUDY IN MAINLY THE NORTHERN HALF OF THE FORECAST AREA THIS MORNING...THEN CLEARING IN THE AFTERNOON. WILL ALSO TREND OUT THE FOG THIS MORNING. THESE CLOUDS ALSO KEEPING TEMPERATURES ABOUT 10 DEGREES F WARMER THAN CLEAR AREAS OVERNIGHT. THESE TEMPERATURES SHOULD REMAIN IN THE 15 TO 20 DEGREE F RANGE UNTIL THE CLOUD DECK MIXES OUT THIS AFTERNOON. SURFACE AIR PARCEL TRAJECTORY FORECAST BRINGS IN AIRMASS FROM SOUTH CENTRAL MINNESOTA...WHERE HIGHS ON TUESDAY WERE IN THE UPPER TEENS. WARM AIR ADVECTION BRINGS 850MB TEMPERATURES ABOVE FREEZING ACROSS MOST OF SOUTHERN WISCONSIN BY 00Z THURSDAY...WITH 1000/500MB THICKNESSES REACHING THE 540 DKM LEVEL. SO...WILL GO WITH HIGHS IN THE MID 20S F PER NAM FORECAST SOUNDINGS AND GFS MOS 3 HOURLY TEMPERATURES. WARM AIR ADVECTION CONTINUES IN EARNEST FOR TONIGHT INTO FRIDAY...AS UPPER LEVEL FLOW BECOMES MORE ZONAL. 850MB TEMPERATURES RISE ABOVE FREEZING...AND THE 1000/500MB THICKNESSES RISE INTO THE MIDDLE 540 DKM RANGE. THE NAM IS MORE AGGRESSIVE WITH THE WARMING THAN THE GFS...ESPECIALLY AT 850MB. THE SOLID SNOW COVER ACROSS SOUTHERN WISCONSIN WILL CONTINUE THE TREND OF GOING WITH HIGH TEMPERATURES IN THE MID 30S F FOR THURSDAY INTO THE WEEKEND. NEXT CHANCE OF PRECIPITATION COMES WITH SHORTWAVE TROUGHS FOR FRIDAY AND SATURDAY. INITIAL SHORTWAVE TROUGH AND VORTICITY MAXIMUM PROPAGATES THROUGH THE FORECAST AREA ON FRIDAY. AREA GFS FORECAST SOUNDINGS SHOWING SOME POTENTIAL FOR FREEZING RAIN. TOP DOWN METHOD SHOWS SUPERCOOLED WATER DROPLETS BEING INTRODUCED INTO THE WARM LAYER. HOWEVER...DEEP WARM LAYER OF ABOUT 6000 TO 7000 FEET ALSO DEPICTED. FOR NOW...WILL ADD FREEZING RAIN OR RAIN CHANCE TO THE SOUTHEAST COUNTIES...AND LEAVE THE FREEZING RAIN OR LIGHT SNOW CHANCE ELSEWHERE. WILL KEEP SOUTHEAST COUNTIES IN CHANCE OF FREEZING RAIN OR RAIN FRIDAY NIGHT...WITH CHANCE OF RAIN OR LIGHT SNOW FOR SATURDAY. THE REST OF THE FORECAST AREA SHOULD SEE A GRADUAL TRANSITION TO LIGHT SNOW BY SATURDAY...AS COOLER 850MB TEMPERATURES ADVECT INTO SOUTHERN WISCONSIN. SHORTWAVE TROUGH AND VORTICITY MAXIMA FOR SATURDAY STRONGER THAN INITIAL WAVE FROM FRIDAY...WHICH MAY BEAR WATCHING FOR SOME LIGHT SNOW ACCUMULATIONS. && .MKX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ WOOD wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 645 AM EST WED DEC 21 2005 .AVIATION... SKIES CLEARED OUT AT KSBN AND MIST AND STRATUS QUICKLY FILLED BACK IN. KFWA APPEARS ON EDGE OF BREAKING OUT BASED ON LATEST DERIVED FOG PRODUCT. SOME HIGH CLOUDS ARE OBSCURING THE VIEW AT KFWA SO SOME UNCERTAINTY. HOWEVER...BASED ON TRENDS AND SURROUNDING OBSERVATIONS...IT APPEARS CLEARING IS WORKING SOUTHEAST. HAVE STARTED KFWA OUT SCT WITH A TEMPO BROKEN AND MVFR VIS. THE HIGH CLOUDS ARE ASSOCIATED WITH A SHORT WAVE PASSING BY. STRATUS DECK ACROSS WI AND MI BEGINNING TO MOVE SOUTH BEHIND THIS WAVE. EXPECT THESE LOW CLOUDS TO ROLL BACK INTO KSBN AND KFWA THIS MORNING. KSBN MAY TEMPORARILY LOOSE THE CURRENT CIG FROM BR AND STRATUS BUT DID NOT TRY AND TIME THAT AS APPROACH OF UPSTREAM CLOUDS SHOULD BE RATHER QUICK. MOISTURE HANGS AROUND MOST OF DAY BEFORE DRYING WORKS BACK IN LATE AFTERNOON AND EARLY EVENING. WITH LIGHT WINDS THIS EVENING...MIST AND STRATUS POSSIBLE AGAIN THIS EVENING BEFORE WINDS INCREASE OVERNIGHT. HAVE BROUGHT IN SOME MVFR BR FOR NOW. && .SHORT TERM... TODAY AND TONIGHT... ONCE AGAIN SKY COVER AND TEMPERATURES ARE THE FORECAST CHALLENGES FOR THE SHORT TERM PERIOD. SATELLITE SHOWS LOW STRATUS ERODING FROM WEST TO EAST ACROSS FORECAST AREA AT ISSUANCE TIME. CHALLENGE IS WHEN AND WHERE EROSION WILL END AND HOW TO PLAY SKY COVER FOR TODAY. DESPITE MISSING INGEST OF UPPER AIR DATA...00Z NAM40 IS DOING QUITE WELL MODELING CLOUD COVER IN THE VICINITY OF 925MB LEVEL WITH ITS RH FIELD. IT BRINGS DRIER AIR INTO CENTRAL AND SOUTHERN FORECAST AREA FOR A FEW HOURS THIS MORNING BEFORE BRINGING MOISTURE BACK AHEAD OF FAST MOVING SHORT WAVE SEEN IN WATER VAPOR DROPPING SOUTH THROUGH MICHIGAN. RUC40 THROUGH THE MORNING HOURS IS LESS PESSIMISTIC WITH ITS 925MB RH FIELD. THERE DOES APPEAR TO AT LEAST BE SOME MID OR HIGH LEVEL CLOUDS ACROSS WISCONSIN ASSOCIATED WITH THIS SHORT WAVE. THEREFORE PLAN TO HAVE PARTIAL CLEARING EARLY THIS MORNING WESTERN AREAS THEN INCREASE CLOUDS AGAIN BY MID MORNING NORTHWEST. WILL KEEP SOUTHWEST PARTLY CLOUDY. HAVE KEPT EASTERN AREAS MOSTLY CLOUDY WITH SOME DECREASE LATE THIS AFTERNOON BEHIND SHORT WAVE. STRONG SUBSIDENCE AND CONTINUED DRYING TONIGHT WILL SCOUR OUT MOST CLOUDS. HAVE TRENDED GRIDS TO BETWEEN 30 AND 40 PERCENT FOR NOW TO ACCOUNT FOR POSSIBLE SLOWER MOVEMENT OF CLOUDS. HAVE ALSO ADDED SOME PATCHY FREEZING FOG TO THIS MORNING AS UPSTREAM OBSERVATIONS HAVE SHOWN SOME PATCHY BR IN THE 3 TO 5 MILE RANGE FORM WHERE SKIES HAVE CLEARED AND WINDS RELAXED. AS FOR TEMPERATURES...DID DROP MAX TEMPS A DEGREE OR TWO TODAY WITH MORE CLOUDS AND COOLER MOS GUIDANCE. DESPITE WARM AIR ADVECTION ALOFT TONIGHT...ONE MORE NIGHT OF COLD TEMPERATURES STILL POSSIBLE WITH CLEARING SKIES AND WINDS UNDER 10KTS. && .LONG TERM... THURSDAY THROUGH TUESDAY...FINALLY APPEARS TO BE A BREAK OUT OF THE DEEP FREEZE AS THE FLOW BECOMES HIGH ZONAL. THE UPPER LEVEL RIDGE OVER WESTERN NORTH AMERICA WILL BREAK DOWN PER NCEP...ECMWF AND CANADIAN MODEL CONSENSUS. OVER THE MIDWEST...THE RETURN FLOW INCREASES THURSDAY WITH A TIGHT PRESSURE GRADIENT DEVELOPING BETWEEN THE 1025 MB SFC HIGH OVER THE SE CONUS AND THE DEEP LOW NORTH OF THE GREAT LAKES. THE NAM AND NGM APPEAR TOO ROBUST WITH THE WARM UP THURSDAY...THE NGM FWC MOS HIGH OF 44 IS 9 DEGREES WARMER THAN THE MAV HIGH OF 35 AT FWA. GIVEN SNOW COVER OVER THE FORECAST AREA OF GENERALLY 4-8 INCHES...WENT WITH THE MORE CONSERVATIVE MAV. WILL BE HARD TO MIX MUCH OF THE WARM AIR DOWN TO THE SURFACE. A WEAK SHORT WAVE SHOULD MOVE ACROSS THE AREA EARLY FRIDAY...SO HAVE KEPT A CHANCE FOR RAIN SHOWERS IN THE GRIDS/ZFP OVER NORTH AREA INCLUDING FAR SOUTHERN LOWER MICHIGAN. ISENTROPIC ANALYSIS STILL FAVORS LOWER MICHIGAN FOR THE BEST CHANCE FOR PRECIPITATION PER UPGLIDE AND SATURATION ON THE 300K SFC. THE NEXT SYSTEM POISED TO EFFECT THE WEATHER THIS WEEKEND APPEARS MUCH STRONGER THAN THE FRIDAY SYSTEM. THE ECMWF SHOWED SOME CONSISTENCY FROM THE 20/00Z RUN WITH THIS UPPER LOW DROPPING INTO THE GREAT LAKES REGION. THE GFS HAS TRENDED THIS SYSTEM STRONGER DURING THE SAME PERIOD. THE CAVEAT IS THE PAST MODEL HANDLING OF DIGGING THIS TYPE OF SYSTEM TOWARD THE SOUTHERN STREAM. EXPECT A SLOWER SOLUTION THAT WHAT IS EVEN NOW ADVERTISED BY THE GFS AND THE ECMWF. FOR THIS PACKAGE...KEPT CHANCE POPS SATURDAY THROUGH SUNDAY WITH THE ARRIVAL OF THIS SYSTEM. POTENTIAL STILL FOR ACCUMULATING SNOW...ESPECIALLY SATURDAY NIGHT. AN EVEN SLOWER AND STRONGER SOLUTION WOULD SUPPORT ACCUMULATING SNOW INTO SUNDAY. HAVE RAISED POPS TO 50 PERCENT SATURDAY NIGHT...BUT HESITANT TO MAKE CHANGES PAST SATURDAY NIGHT GIVEN WIDE VARIETY OF POSSIBLE SOLUTIONS AND THE POTENTIAL FOR A STRONGER AND SLOWER SYSTEM. FOR MONDAY AND TUESDAY...THE CANADIAN ENSEMBLES SUPPORT A CONTINUANCE OF THE HIGH ZONAL FLOW WITH MILD TEMPERATURES...ALTHOUGH MULTIPLE SHORTWAVES WILL BE MIGRATING ACROSS THE CONUS. KEPT THE FORECAST DRY MONDAY AND TUESDAY. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM/AVIATION...LASHLEY LONG TERM....SKIPPER in AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 940 AM EST WED DEC 21 2005 .UPDATE... LIGHT SNOW CONTINUES TO INCREASE IN COVERAGE AS WEAK SURFACE TROF APPROACHES FROM THE WEST. H2O VAPOR LOOP SHOWS STILL A WELL DEFINED SHORT WAVE DIVING SOUTHEAST WITH ENOUGH LAKE INSTABILITY TO PROVIDE THE AREA OF LIGHT SNOW (SEEN WELL ON THE GRB SOUNDING THIS MORNING WITH -11C AT 850MB). 12Z RUC PROFILES CONTINUE TO SUGGEST DRYING ALOFT WITH THE PASSAGE OF THIS SHORT WAVE BUT STILL PLENTY OF LOW CLOUDS UPSTREAM. WE SHALL SEE THE NEXT COUPLE OF HOURS TO UPDATE CLOUD COVER REACTS WITH SUBSIDENCE. UPDATED FORECAST HAS BEEN ISSUED. && .PREV DISCUSSION...ISSUED 540 AM EST WED DEC 21 2005 AVIATION... UPPER WAVE AND ASSOCIATED SURFACE TROF DROPPING SOUTHEAST TOWARD THE REGION THIS MORNING. MOISTURE IS LIMITED WITH THIS SYSTEM WITH DEEPER MOISTURE REMAINING NORTH OF SOUTHEAST LOWER MICHIGAN. AS A RESULT BEST CHANCE FOR SNOW WILL BE FROM FNT NORTHWARD BETWEEN 12-18Z. ANTICIPATE VSBYS TO BRIEFLY DROP TO 3-5 MILES IN SCATTERED SNOW SHOWER ACTIVITY...OTHERWISE ANTICIPATE MVFR CIGS TO PERSIST THROUGH THE DAY BETWEEN 015-020...GRADUALLY LIFTING TO 025 AFTER 18Z. WARM AIR ADVECTION TONIGHT AHEAD OF ANOTHER LOW PRESSURE SYSTEM WILL GRADUALLY INCREASE LOW LEVEL WIND FIELD TO 15 TO 20 KTS...AND SOME CLOUD COVER WILL LINGER THROUGH THE NIGHT AS WARM AIR ADVECTION ALOFT STRENGTHENS LOW LEVEL INVERSION. MAY SEE SOME SIGNIFICANT BREAKS IN MVFR CLOUD COVER AFTER 06Z THURSDAY. SHORT TERM...WEDNESDAY AND WEDNESDAY NIGHT SHARPENING UPPER TROF AXIS AND ASSOCIATED VORTICITY LOBE OVER OVER NORTHERN WISCONSIN DIVING SOUTHEAST TOWARD THE CWA EARLY THIS MORNING. GFS APPEARS TO HAVE A BETTER DEFINITION ON THIS WAVE AND GFS 850 MB TEMPERATURE ANALYSIS MUCH BETTER THAN THE NAM OVER THE UPPER MISSISSIPPI VALLEY...NAM APPEARS TO HAVE A 1-2 DEGREE WARM BIAS. MOISTURE ON THE LEAN SIDE WITH WAVE MOVING INTO THE CWA THIS MORNING...HOWEVER MODELS SHOWING SOME MODEST MID LEVEL OMEGA/QVECTOR CONVERGENCE OVER MAINLY THE NORTHERN CWA THOUGH 18Z IN BETTER WARM AIR ADVECTION FIELD AHEAD OF ASSOCIATED SURFACE TROF...THEN SUBSIDENCE QUICKLY MOVING BACK INTO THE REGION THIS AFTERNOON. ALSO A LITTLE CONCERNED WITH PRECIPITATION TYPE AS MOISTURE INITIALLY SHALLOW. HOWEVER WATER VAPOR LOOP SHOWING GOOD INCREASE IN MID LEVEL MOISTURE AND IR ICE CLOUD SCHEME INDICATING MOSTLY SNOW AS WELL. SO AT THIS TIME WILL INCLUDE CHANCE POPS FOR ALL SNOW NORTH HALF OF CWA THROUGH 18Z...AND SLIGHT CHANCE SOUTH WHERE ASSOCIATED SURFACE TROF IS LESS DEFINED. WEAK RIDGE TO BUILD INTO THE REGION LATE THIS AFTERNOON AND EVENING...THEN QUICKLY TRACKING EAST AS NEXT TROF AXIS MOVES INTO THE NORTHERN GREAT LAKES. AS A RESULT WARM AIR ADVECTION WILL CONTINUE OVERNIGHT...WITH 850 TEMPS WARMING TO AROUND -2C AS NOTED ON GFS SOLUTION. HOWEVER BOTH MODELS VERY DRY IN THIS WARM AIR ADVECTION FIELD AND EVEN SCOUR OUT 925 MB MOISTURE. SO WILL CONTINUE WITH A DRY FORECAST FOR WEDNESDAY NIGHT. WILL DECREASE CLOUD COVER TO PARTLY CLOUDY AFTER MIDNIGHT...BUT NOT CONFIDENT THAT MOISTURE WILL BE SCOURED OUT UNDERNEATH INVERSION. WILL LEAN TOWARD COLDER MAV TEMPS FOR TODAY AND TONIGHT AS NAM THERMAL FIELD APPEARS TO BE RUNNING A LITTLE ON THE WARM SIDE. LONG TERM... OVERALL LONGWAVE PATTERN STILL LOOKS ON TRACK...WITH BRIEF ZONAL FLOW GIVING WAY TO REAMPLIFICATION BY THE WEEKEND. GFS HAS COME MORE IN LINE WITH THE ECMWF/WRF-XX WITH RESPECT TO THE DIGGING TROUGH ACROSS THE EASTERN CONUS SATURDAY/SUNDAY. DIFFERENCES STILL EXIST... WITH DEGREE OF DIGGING...AMOUNT OF SURFACE DEVELOPMENT...AND TRACK OF THE SURFACE LOW. INITIALLY NAM/GFS HAVE BOTH TRENDED FASTER AND FARTHER SOUTH WITH THE NORTHERN WAVE TRACKING ACROSS CANADA TOWARD JAMES BAY. THIS LEADS TO A FARTHER SOUTH PLACEMENT OF THE BAROCLINIC ZONE THAT DROPS INTO THE NORTHERN GREAT LAKES THURSDAY NIGHT. STRONG WARM ADVECTION IS UNDERWAY THURSDAY/THURSDAY NIGHT...WITH GOOD WARMING/BUILDING HEIGHTS BUT LIMITED MOISTURE. FORECAST SOUNDINGS/TIME SECTIONS SHOW A FAIR AMOUNT OF MID/HIGH LEVEL MOISTURE SPREADING ACROSS THE REGION...BUT WITH LOW LEVELS REMAINING DRY. THIS SEEMS REASONABLE GIVEN THE PACIFIC ORIGINS OF THE AIRMASS...WITH HIGH PRESSURE ACROSS THE SOUTHEAST CONUS CUTTING OFF LOW-LEVEL INFLOW FROM THE GULF. WILL KEEP THURSDAY DRY...WITH THURSDAY NIGHT CONTINUING TO LOOK QUESTIONABLE. INITIAL SHORTWAVE EMBEDDED IN THE FAST UPPER FLOW SWINGS THROUGH THURSDAY AFTERNOON... WITH A STRONGER SHORTWAVE FOR FRIDAY. IN BETWEEN... NAM/GFS/WRF-XX ALL SHOW SOME DEGREE OF MID-LEVEL DRYING. HOWEVER LOW-LEVELS DO SATURATE...WITH HELP FROM THE NORTHERN BOUNDARY THAT HAS TRENDED FARTHER SOUTH TOWARD THE GREAT LAKES. CONTINUED 900MB OMEGA/WITH LOW CONDENSATION PRESSURE DEFICITS ALONG THE 280K ISENTROPIC SURFACE. NOT MUCH IN THE WAY OF SPEED OR DIRECTIONAL SHEAR...BUT WITH LIFT AND A MODEST AMOUNT OF LOW-LEVEL MOISTURE WILL OPT FOR AREAS OF DRIZZLE RATHER THAN CHANCE RAIN/SNOW. AS FOR PRECIP TYPE... TEMPERATURES ARE THE OTHER CONCERN FOR THURSDAY NIGHT. KEPT HIGHS ON THURSDAY ON THE COOL SIDE NEAR FREEZING WITH THE EXPECTATION THAT THE COLD LOW-LEVEL AIRMASS WILL BE DIFFICULT TO SCOUR OUT... ESPECIALLY WITH A LARGE RANGING SNOW PACK ACROSS THE AREA AND UPSTREAM. MODELS HAVE ALSO BACKED OFF ON THE WINDS A BIT...NOT BRINGING IN THE BETTER GRADIENT UNTIL DURING THE DAY ON THURSDAY. GOOD WARM ADVECTION WILL FOLLOW THROUGH THE NIGHT. AFTER A BRIEF INITIAL DROP...EXPECT TEMPS TO SLOWLY CLIMB THROUGH THE NIGHT. WITH BETTER MOISTURE/BETTER CHANCE FOR PRECIP...WOULD EXPECT WARMER AIR TO BE ABLE TO MIX DOWN TO THE SURFACE EASIER THROUGH PRECIP LOADING. HOWEVER...NOT EXPECTING MUCH IN THE WAY OF QPF. TEMPERATURES WILL BE HOVERING AROUND FREEZING...CLIMBING FROM THE COLD SIDE. ESPECIALLY WITH LINGERING SNOWPACK...WOULD NOT BE SURPRISED IF SOME LOCATIONS REMAINED BELOW FREEZING EVEN WITH PRECIP. THEREFORE WILL KEEP A MENTION OF FREEZING PRECIP...AREAS OF DRIZZLE OR FREEZING DRIZZLE. STRONGER SHORTWAVE SWINGS THROUGH ON FRIDAY...WITH WRF-XX SHOWING A MODEST SURFACE TROUGH ASSOCIATED WITH IT AS WELL. WITH ANOTHER SURGE OF DEEPER MOISTURE AND MORE FOCUSED LIFT...WITH LOW LEVELS ALREADY PRETTY SATURATED...WE HAVE A DECENT CHANCE FOR SEEING PRECIP. INCREASED POPS A BIT TO HIGH CHANCE...MAINLY ACROSS THE NORTHERN CWA CLOSER TO THE SHORTWAVE TRACK AND EXISTING BOUNDARY. PRECIP TYPE CONTINUES TO BE A CONCERN...ALTHOUGH WITH TEMPERATURES WARMING ABOVE FREEZING IT WILL BE A QUESTION MORE OF RAIN OR SNOW. NAM SOUNDINGS ARE BY FAR THE WARMEST WITH THE WARM WEDGE...UP TO 4C GENERALLY 900MB-850MB. HOWEVER IT IS ALSO THE DRIEST THROUGH THIS LAYER. PROGRESSION OF GFS SOUNDINGS SEEM TO INDICATE SOME COOLING THROUGH EVAPORATION...WHICH SEEMS MORE REASONABLE THAN THE NAM SOUNDINGS. SIMILAR IS TRUE WITH THE WRF-XX...ALTHOUGH IT CONTINUES TO HAVE A MUCH WARMER BOUNDARY LAYER THAN THE GFS. FOR NOW WILL CONTINUE TO EDGE TOWARD THE COLDER SOLUTION...KEEPING A MIX OF MODERATE RAIN OR SNOW THROUGH THE DAY WITH TEMPS GETTING INTO THE UPPER 30S. WITH THE SHARPER SHORTWAVE AND FRIDAY AND MORE AMPLIFIED TROUGH ON SATURDAY...WE SEE SOME WEAK SHORTWAVE RIDGING ACROSS THE AREA ON FRIDAY NIGHT. FORECAST SOUNDINGS/TIME SECTIONS SHOW DEEP MOISTURE STRIPPING AWAY ONCE AGAIN...WITH LOW LEVELS WITH DEEPER LOW LEVEL MOISTURE WITH HIGHER RELATIVE HUMIDITIES. WRF-XX/GFS CONDENSATION PRESSURE DEFICITS ARE NEAR ZERO ALONG THE 280K/UP TO 285K ISENTROPIC SURFACES. WEAK LIFT STILL PRESENT...SO IT IS HARD TO RULE OUT PRECIP CHANCES. HOWEVER WITH LACK OF DEEPER MOISTURE IT LOOKS LIKE WE WILL HAVE ANOTHER DRIZZLE POTENTIAL. WITH TEMPERATURES FALLING BACK TO JUST BELOW FREEZING...FREEZING DRIZZLE WILL BE A POSSIBILITY. COULD SEE A TEMPERATURE BUST EITHER SIDE...COLD SIDE BY NOT GETTING VERY WARM ON THURSDAY AND DROPPING BELOW FREEZING EARLY THURSDAY NIGHT OR ON THE WARM SIDE BY GETTING INTO THE UPPER 30S ON THURSDAY AND NOT FALLING VERY MUCH AT ALL OVERNIGHT WITH CONTINUED SOUTHWESTERLY FLOW AND PERSISTENT CLOUD COVER. THEREFORE WILL MENTION DRIZZLE OR FREEZING DRIZZLE THROUGH THE NIGHT. AS MENTIONED ABOVE...EXTENDED MODELS ARE COMING INTO BETTER AGREEMENT WITH THE OVERALL SYNOPTIC PATTERN...MORE TOWARD THE ECMWF/WRF-XX SOLUTIONS. DIFFERENCES CONTINUE WITH DEGREE OF TROUGHING AND HOW THE TROUGH EVOLVES...WITH THE WRF-XX DEEPER...GFS MORE POSITIVELY TILTED...AND ECMWF TAKING ON MORE OF A NEGATIVE TILT. LOW PRESSURE EXPECTED TO TRACK THROUGH THE REGION SATURDAY/SATURDAY NIGHT TIMEFRAME...WITH THE WRF-XX SOUTH OF US...ECMWF NORTH OF US...AND GFS OVER US. EXACT DETAILS REMAIN TO BE SKETCHED OUT...BUT ENOUGH CONSISTENCY IN THE LONGWAVE PATTERN TO BUMP POPS UP A BIT FOR SATURDAY/SATURDAY NIGHT. PRECIP TYPE STILL LOOKS GOOD WITH A MIX OF RAIN/SNOW INITIALLY ON SATURDAY...BUT ENOUGH COOLING THROUGH THE COLUMN FOR ALL SNOW FOR SATURDAY NIGHT. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...SMALL CRAFT ADVISORY FOR WINDS...SAGINAW BAY UNTIL 1 PM WEDNESDAY. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && $$ SHORT TERM...BGM LONG TERM....JB YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE). mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE RALEIGH NC 1002 AM EST WED DEC 21 2005 .SHORT TERM (REST OF TODAY THROUGH TONIGHT)... FEW CHANGES TO ONGOING FORECAST THIS AFTERNOON. ONE UPPER TROUGH MOVING EAST ACROSS THE CAROLINAS WITH CLOUDS HAVING DEVELOPED... AIDED IN PART BY JET MAX SHOWN ON LONG-LOOP WATER VAPOR IMAGE MOVING OUT OF THE GULF OF MEXICO AND INTO THE ATLANTIC DURING THE OVERNIGHT HOURS. STRONG NVA IS FORECAST BY BOTH THE RUC AND THE NAM THIS AFTERNOON...AND AS THE JET CONTINUES TO SLIDE OFF TO THE EAST AND SOUTHEAST DURING THE REST OF THE DAY...CLOUDS WILL MOVE OFF ALONG WITH IT. VERY DRY 700MB LEVEL AIR TO THE WEST AND NORTHWEST ANALYZED ON 12Z RAOB ANALYSIS. PRIMARY CHANGES WILL BE TO SANDHILLS AND COASTAL PLAIN ZONES WHERE PARTLY CLOUDY SKIES WILL BECOME SUNNY BY EARLY AFTERNOON. FULLY MIXED GSO SOUNDING YIELDS HIGHS IN THE UPPER 40S...ALTHOUGH COOL THICKNESSES THIS MORNING AND CONTINUED ESSENTIALLY NEUTRAL TEMPERATURE ADVECTION WOULD PROVIDE FOR ONLY MID 40S ON LOCAL TEMPERATURE SCHEME USING 1000-850MB THICKNESSES. THINK ONGOING TEMPERATURE FORECAST IN THE MID TO UPPER 40S WITH AMPLE SUN AND DRY AIR SHOULD CONTINUE TO WORK JUST FINE. FOR GRIDDED FORECAST...WILL TEND TO FOLLOW DRIER NAM ON DEW POINTS AS THE RUC IS SIMPLY TOO MOIST THIS MORNING. ANOTHER MID-LEVEL SHORTWAVE MOVES THROUGH CENTRAL NORTH CAROLINA OVERNIGHT...BUT THIS SHORTWAVE HAS NO JET SUPPORT NEARBY AND MOISTURE IS VERY LOW. QUICK LOOK AT THE LATEST NAM MODEL SOUNDINGS SHOWS AN AIR MASS ABOUT AS DRY AS IT GETS OVER CENTRAL NORTH CAROLINA. 12Z 850MB ANALYSIS INDICATED MOISTURE WORKING ITS WAY NORTH OUT OF THE WESTERN GULF INTO THE TENNESSEE VALLEY...BUT GUIDANCE SUGGESTS ANY LOW-LEVEL MOISTURE WILL REMAIN WELL TO OUR WEST AND NORTHWEST...POSSIBLY GETTING AS CLOSE AS THE SOUTHERN WEST VIRGINIA/VIRGINIA BORDER BY 12Z THURSDAY. ONGOING CLEAR FORECAST IS ON TARGET FOR TONIGHT. && .CLIMATE... A REVIEW OF THE FIRST TWO-THIRDS OF DAILY AVERAGE TEMPERATURES AT RDU AND GSO SHOW THAT ON ONLY ONE DAY IN DECEMBER...THE 4TH...HAS THE AVERAGE BEEN ABOVE NORMAL. ALL OTHER DAYS HAVE BEEN BELOW NORMAL...WITH ONE DATE AT GSO EXACTLY NORMAL. EVEN WITH THE COOL TEMPERATURES...BOTH RDU AND GSO ARE AT LEAST TWO FULL DEGREES SHY OF GETTING CLOSE TO THE TOP FIVE COOLEST DECEMBERS AS OF THIS POINT. THE COOL TREND WILL CONTINUE FOR THIS FIRST DAY OF WINTER...ALTHOUGH RISING MAXES FOR LATER THIS WEEK SHOULD END THE STREAK OF BELOW NORMAL DAYS SOON. && .PREVIOUS DISCUSSION... (ISSUED 230 AM EST WED DEC 21 2005) SHORT TERM (TODAY THROUGH SATURDAY)... FORECAST IS SIMPLY A TEMPERATURE FORECAST THROUGH THE PERIOD. MAY BE ABLE TO PUT A DEGREE ON TUESDAY HIGHS FOR TODAY...PERHAPS A COUPLE IN THE NORTHEAST. FIFTY TO FIFTY-FIVE THURSDAY AFTERNOON WITH LIGHT SOUTHWEST BREEZE AND SUNSHINE. FRIDAY HIGHS 55 TO 60 WITH WEAK WARM ADVECTION AND ONLY A TOUCH WARMER SATURDAY. LOWS ON A STEADY WARMING TREND TO ABOVE FREEZING BY SATURDAY MORNING ALL LOCATIONS. LONG TERM (SATURDAY NIGHT THROUGH TUESDAY)... CURRENT FORECAST LITTLE CHANGED. RAIN CHANCES INCREASE FROM WEST TO EAST AFTER MIDNIGHT SATURDAY NIGHT. RAIN CHANCES ENDING FROM WEST TO EAST SUNDAY AFTERNOON AND EVENING...BUT WILL NOT GET FANCY WITH TIMING WITH EVENT STILL SO FAR OUT IN TIME. RAINFALL AMOUNTS GENERALLY ONE QUARTER INCH OR LESS. REMAINDER OF THE FORECAST DRY. NO SIGNIFICANT MODIFICATION TO TEMPERATURES. AVIATION... VFR CONDITIONS THROUGH THE TAF PERIOD. UPPER LEVEL TROUGH MOVING OVER THE AREA THIS MORNING WILL RESULT IN BROKEN CIRRUS CLOUDS THROUGH ABOUT 14Z...OTHERWISE CLEAR SKIES. AT THE SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE REGION FROM THE SOUTHWEST. LIGHT NORTHERLY WINDS WILL SHIFT TO THE NORTHWEST BETWEEN 12Z AND 15Z AND REMAIN UNDER 10 KNOTS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...DJF CLIMATE...DJF nc AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 941 AM CST WED DEC 21 2005 .DISCUSSION... IN JUST A COUPLE OF HOURS...THE SUN ANGLE WILL BE AS LOW AS IT GETS THIS YEAR. AHHH...WINTER SOLSTICE. TEMPERATURES AGAIN WL PROVIDE THE LARGEST CHALLENGE TDA. A COLD START ONCE AGAIN WITH A SHALLOW BUT IMPRESSIVE INVERSION...WITH TMPS DEFINING ELEVATION DIFFERENCES. FIRST APPROXIMATION TOWARD AN ISOTHERMAL TEMPERATURE BASED ON MORNING RAOBS WOULD SUGGEST AT LEAST SEVERAL DEGREES COOLER. LTST RUC/NAM MORE ON SIDE OF WKR LOW LVL GRADIENT...NOT GOOD NEWS FOR WARMING. FAIRLY DECENT GRADIENT ALFT ON WIND PROFILERS...SO STABILIZING WAA WL GO ON MERRILY AWAY...AGAIN NOT DOING ANY FAVORS FOR WARMING LOWER ELEVATIONS. THEREFORE...SEEMS PRUDENT TO LOWER TMPS BY SEVERAL DEGREES. && .PREV DISCUSSION... A CLR START WILL GIVE WAY TO SLWLY INCRG HI AND EVENTUALLY A FEW MID CLDS FROM THE W. STILL ROOM FOR PLENTY OF SUNSHINE EVEN AS HI CLDS SLWLY INCRS. THAT LEADS TO MAIN FCST QSTN BEING HOW MUCH WILL IT WARM AT SFC...AND THIS PATTRN WILL CONT THRU THU EVEN WITH A FEW MORE HI AND MID CLDS THAN TDA. TEMPS OF COURSE AFFECTED BY RMNG SNW CVR...IN ANY EVENT QUITE A BIT WRMR TDA AND MORE SO TH. 50 PLUS NOT UNREASNBL THU FAR SRN PART OF FCST AREA...NAMELY SUX AREA...AS SNW CVR WILL BE GETTING CLOSE TO BARE GROUND. A LTL COOLNG STARTS FRI BUT STILL QUITE MILD...AHD OF SYS APPCHG FROM PAC AND OVER WRN RDG. WILL KEEP ASSORTED LGT PCPN ON 20 AND 30 POPS FOR FRI NGT INTO SAT WITH SOME ZR/S N AND R/S S. NOT TO MUCH CHANGE FROM WHAT WE HAVE BEEN GOING. CURNT MODELS INCLUDG GFS SUGGEST TROF WITH PAC CDFNT AS MAIN SUPPORT SLIDES S OF AREA...STILL CONSISTNT WITH MENTN OF PCPN BUT FAIRLY LOW POPS. THIS IS GOOD BECAUSE STDY COURSE SEEMS BEST WITH A SYS WHICH IS NOW WAY OUT IN THE WRN PAC. IN ANY EVENT SOME COOLNG LIKELY. DRY AND TEMPS WARMNG BACK UP A LTL STILL SEEMS LIKE BEST BET FOR SUN INTO MIDDLE OF NEXT WEEK. WILLIAMS && .FSD WATCHES/WARNINGS/ADVISORIES... IA...NONE. MN...NONE. NE...NONE. SD...NONE. && $$ CHAPMAN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 201 PM EST WED DEC 21 2005 ...SUB-FREEZING TEMPERATURES EXPECTED NEXT TWO NIGHTS... .SHORT TERM...HIGH PRESSURE AT THE SURFACE HAS SETTLED ACROSS THE LOWER MISSISSIPPI VALLEY WITH GENERALLY LIGHT NORTHWEST FLOW ACROSS THE FORECAST AREA. RUC40 INDICATES SHORTWAVE TROUGH IS CURRENTLY DRAPED ACROSS THE STATE LINE AND WILL CONTINUE TO PUSH SOUTH THROUGH THIS EVENING. EXPECT RIDGE AXIS IN RESPONSE TO SHIFT EVER SO SLIGHTLY EASTWARD THROUGH 06Z WHICH WILL BE A MAJOR FACTOR IN EXPECTED OVERNIGHT LOW TEMPERATURES. INHERITED WARNING INCLUDES ALL OF GEORGIA AND ALL BUT THE EXTREME SOUTHEASTERN PORTIONS OF THE CWA AND INCOMING GUIDANCE PROVIDES LITTLE ARGUMENT AGAINST IT. IT DOES HOWEVER SHOW A RANGE OF 29 TO 32 FOR OCALA AND EXPECT THE NORTHWEST SECTIONS OF MARION TO ENCOUNTER FREEZE CONDITIONS SHOULD WINDS STAY BELOW 3 MPH AS EXPECTED. WILL THEREFORE UPGRADE CURRENT WATCH TO A WARNING FOR MARION AND PUTNAM COUNTIES. MAV DOES SHOW SOME LIGHT WINDS CONTINUING FOR THESE SECTIONS WHERE RIDGE AXIS SHOWS LESS INFLUENCE...BUT BASED ON CURRENT 8 TO 10 MPH SPEEDS...WE SHOULD DE- COUPLE ENOUGH TO WARRANT A WARNING. FORECAST CONTINUES TO CENTER AROUND TEMPERATURES FOR SATURDAY AND IT APPEARS TO BE ANOTHER WIDESPREAD FREEZE IN STORE FRIDAY MORNING. COULD NOT ASK FOR A BETTER RADIATIONAL SETUP WITH PARENT HIGH OVER THE SOUTHEAST GEORGIA. THIS WILL ALLOW FOR A SIMILAR GEOGRAPHICAL COVERAGE FOR FREEZING CONDITIONS BUT DURATIONS WILL BE MUCH LONGER. WILL KEEP CURRENT WATCH AS IS BUT WILL NEED TO BE UPGRADED WITH LATER PACKAGES. .LONG TERM...A MUCH BETTER FEELING REGARDING THE EXTENDED NOW THAT THE GFS SHOWS MUCH IMPROVED RUN TO RUN CONSISTENCY. DGEX AND OTHER LONG TERM MODELS ALSO IN BETTER AGREEMENT AS IS THE NAM THROUGH 84 HRS WHICH INCLUDES CHRISTMAS EVE. MOST OF THESE MODEL SUITES HAVE TRENDED TOWARD A PRE-FRONTAL BAND OF PRECIP FORMING IN SOUTHWEST FLOW OFF THE GULF AHEAD OF MAIN SYSTEM. SINCE THIS IS THE FIRST RUN SHOWING THIS AND MOST OF IT REMAINS NORTH AND WEST OF THE AREA... WILL CONTINUE A DRY CHRISTMAS EVE FOR THIS RUN. MAIN FRONTAL RAIN BAND MOVES THROUGH DURING THE DAY ON CHRISTMAS WITH SCATTERED POPS ADVERTISED FOR NOW FOR ALL AREAS. MODELS ARE SHOWING A PRETTY GOOD MOISTURE RETURN OFF THE NORTHEASTERN GULF WITH DEWPOINTS POSSIBLY REACHING THE 60 DEGREE MARK OVER THE SUWANNEE VALLEY. THIS HAS BEEN THE CUTOFF FOR THUNDER ACTIVITY WITH THE LAST TWO SYSTEMS BUT WILL ALLOW FOR AN ADDITIONAL RUN BEFORE INDICATING ISOLATED THUNDER. CONDITIONS CLEAR QUICKLY AND A DRY START TO NEXT WEEK IS EXPECTED. && .MARINE...SMALL CRAFT EXERCISE CAUTION CONDITIONS WILL CONTINUE TONIGHT FOR 15 TO 20 KT WINDS AND 4 TO 6 FT SEAS OFFSHORE. GENERALLY NORTH WINDS WILL CONTINUE UNTIL THE WEEKEND THEN SHIFT TO SW IN ADVANCE OF THE NEXT COLD FRONT. && .FIRE WEATHER...LAPS SHOWS RH VALUES AOB 35 PCNT ALONG WRN PORTION OF FORECAST AREA NORTH OF SUWANNEE COUNTY. THINK CRITICAL DURATION WILL NOT BE MET THIS AFTERNOON. HOWEVER THURSDAY AFTN THE MIN RH EXPECTED IN THIS AREA IS 25 PCNT AND EVEN WITH SHORT DAYS 4 OR 5 HOURS BELOW CRITICAL RH IS POSSIBLE FOR A FEW COUNTIES IN NE FL. WILL CONTINUE THE WATCH FOR NOW. && .PRELIMINARY POINT TEMPS/POPS... AMG 54 28 57 28 / 0 0 0 0 SSI 54 35 56 36 / 0 0 0 0 JAX 57 30 58 30 / 0 0 0 0 SGJ 59 39 58 41 / 0 0 0 0 GNV 59 29 59 30 / 0 0 0 0 OCF 61 31 60 30 / 0 0 0 0 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...FREEZE WARNING FROM 1 AM THURSDAY TO 9 AM THURSDAY FOR THE FOLLOWING ZONES: ALACHUA...BAKER...BRADFORD...CLAY... COLUMBIA...DUVAL...GILCHRIST...HAMILTON...MARION...NASSAU... PUTNAM...SUWANNEE...AND UNION. FIRE WEATHER WATCH FROM NOON THURSDAY TO 5 PM THURSDAY FOR THE FOLLOWING ZONES: COLUMBIA...GILCHRIST...HAMILTON...AND SUWANNEE. FREEZE WATCH FROM 1 AM FRIDAY TO 9 AM FRIDAY FOR THE FOLLOWING ZONES: ALACHUA...BAKER...BRADFORD...CLAY...COLUMBIA... DUVAL...GILCHRIST...HAMILTON...MARION...NASSAU...PUTNAM... ST JOHNS...SUWANNEE...AND UNION. GA...FREEZE WARNING FROM 1 AM THURSDAY TO 9 AM THURSDAY FOR THE FOLLOWING ZONES: APPLING...ATKINSON...BACON...BRANTLEY... CHARLTON...CLINCH...COASTAL CAMDEN...COASTAL GLYNN... COFFEE...ECHOLS...INLAND CAMDEN...INLAND GLYNN...JEFF DAVIS...PIERCE...WARE...AND WAYNE. FREEZE WATCH FROM 1 AM FRIDAY TO 9 AM FRIDAY FOR THE FOLLOWING ZONES: APPLING...ATKINSON...BACON...BRANTLEY...CHARLTON... CLINCH...COASTAL CAMDEN...COASTAL GLYNN...COFFEE...ECHOLS... INLAND CAMDEN...INLAND GLYNN...JEFF DAVIS...PIERCE...WARE... AND WAYNE. MARINE...NONE. && $$ PUBLIC...DEESE MARINE/FIRE WX...TRABERT fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1235 PM EST WED DEC 21 2005 .AVIATION... CLOUDS ASSOCIATED WITH SHORT WAVE CURRENTLY OVER SOUTHERN MICHIGAN IS HAVING A HARD TIME PUSHING A LOW CLOUD DECK SOUTH INTO NORTHERN INDIANA. ANOTHER CLOUD DECK HAS FORMED OVER A 30 MILE WIDE AREA EXTENDING FROM VALPARAISO TO JUST WEST OF FORT WAYNE. EXPECT SCATTERED CLOUDS TO A BROKEN MVFR CEILING THIS AFTERNOON AT BOTH FORT WAYNE AND SOUTH BEND. CLOUDS WILL DECREASE OVERNIGHT AS DRY AIR OVERSPREADS THE WESTERN LOWER GREAT LAKE. WITH CLEAR SKIES EXPECTED OVERNIGHT THERE IS CHANCE OF MVFR FOG DEVELOPMENT WHICH WAS INCLUDED IN THE TERMINAL FORECASTS FOR BOTH SOUTH BEND AND FORT WAYNE. && .UPDATE... CLOUDS ARE NOT AS WIDESPREAD AT ORIGINALLY THOUGHT. DRY AIR OVER ILLINOIS IS SPREADING EAST. CLOUDS ASSOCIATED WITH SHORT WAVE OVER THE LOWER GREAT LAKES SLOWLY MOVING SOUTH AND ARE NOW ALONG THE INDIANA/MICHIGAN BORDER. UPDATED TO PARTLY CLOUDY AND MADE SOME MINOR ADJUSTMENTS TO TEMPERATURE FORECAST...LOWERED A COUPLE DEGREES NORTHEAST WHERE MORE CLOUDINESS IS EXPECTED AND LEFT THE REST OF THE AREA UNCHANGED. .PREV DISCUSSION... SHORT TERM... TODAY AND TONIGHT... ONCE AGAIN SKY COVER AND TEMPERATURES ARE THE FORECAST CHALLENGES FOR THE SHORT TERM PERIOD. SATELLITE SHOWS LOW STRATUS ERODING FROM WEST TO EAST ACROSS FORECAST AREA AT ISSUANCE TIME. CHALLENGE IS WHEN AND WHERE EROSION WILL END AND HOW TO PLAY SKY COVER FOR TODAY. DESPITE MISSING INGEST OF UPPER AIR DATA...00Z NAM40 IS DOING QUITE WELL MODELING CLOUD COVER IN THE VICINITY OF 925MB LEVEL WITH ITS RH FIELD. IT BRINGS DRIER AIR INTO CENTRAL AND SOUTHERN FORECAST AREA FOR A FEW HOURS THIS MORNING BEFORE BRINGING MOISTURE BACK AHEAD OF FAST MOVING SHORT WAVE SEEN IN WATER VAPOR DROPPING SOUTH THROUGH MICHIGAN. RUC40 THROUGH THE MORNING HOURS IS LESS PESSIMISTIC WITH ITS 925MB RH FIELD. THERE DOES APPEAR TO AT LEAST BE SOME MID OR HIGH LEVEL CLOUDS ACROSS WISCONSIN ASSOCIATED WITH THIS SHORT WAVE. THEREFORE PLAN TO HAVE PARTIAL CLEARING EARLY THIS MORNING WESTERN AREAS THEN INCREASE CLOUDS AGAIN BY MID MORNING NORTHWEST. WILL KEEP SOUTHWEST PARTLY CLOUDY. HAVE KEPT EASTERN AREAS MOSTLY CLOUDY WITH SOME DECREASE LATE THIS AFTERNOON BEHIND SHORT WAVE. STRONG SUBSIDENCE AND CONTINUED DRYING TONIGHT WILL SCOUR OUT MOST CLOUDS. HAVE TRENDED GRIDS TO BETWEEN 30 AND 40 PERCENT FOR NOW TO ACCOUNT FOR POSSIBLE SLOWER MOVEMENT OF CLOUDS. HAVE ALSO ADDED SOME PATCHY FREEZING FOG TO THIS MORNING AS UPSTREAM OBSERVATIONS HAVE SHOWN SOME PATCHY BR IN THE 3 TO 5 MILE RANGE FORM WHERE SKIES HAVE CLEARED AND WINDS RELAXED. AS FOR TEMPERATURES...DID DROP MAX TEMPS A DEGREE OR TWO TODAY WITH MORE CLOUDS AND COOLER MOS GUIDANCE. DESPITE WARM AIR ADVECTION ALOFT TONIGHT...ONE MORE NIGHT OF COLD TEMPERATURES STILL POSSIBLE WITH CLEARING SKIES AND WINDS UNDER 10KTS. LONG TERM... THURSDAY THROUGH TUESDAY...FINALLY APPEARS TO BE A BREAK OUT OF THE DEEP FREEZE AS THE FLOW BECOMES HIGH ZONAL. THE UPPER LEVEL RIDGE OVER WESTERN NORTH AMERICA WILL BREAK DOWN PER NCEP...ECMWF AND CANADIAN MODEL CONSENSUS. OVER THE MIDWEST...THE RETURN FLOW INCREASES THURSDAY WITH A TIGHT PRESSURE GRADIENT DEVELOPING BETWEEN THE 1025 MB SFC HIGH OVER THE SE CONUS AND THE DEEP LOW NORTH OF THE GREAT LAKES. THE NAM AND NGM APPEAR TOO ROBUST WITH THE WARM UP THURSDAY...THE NGM FWC MOS HIGH OF 44 IS 9 DEGREES WARMER THAN THE MAV HIGH OF 35 AT FWA. GIVEN SNOW COVER OVER THE FORECAST AREA OF GENERALLY 4-8 INCHES...WENT WITH THE MORE CONSERVATIVE MAV. WILL BE HARD TO MIX MUCH OF THE WARM AIR DOWN TO THE SURFACE. A WEAK SHORT WAVE SHOULD MOVE ACROSS THE AREA EARLY FRIDAY...SO HAVE KEPT A CHANCE FOR RAIN SHOWERS IN THE GRIDS/ZFP OVER NORTH AREA INCLUDING FAR SOUTHERN LOWER MICHIGAN. ISENTROPIC ANALYSIS STILL FAVORS LOWER MICHIGAN FOR THE BEST CHANCE FOR PRECIPITATION PER UPGLIDE AND SATURATION ON THE 300K SFC. THE NEXT SYSTEM POISED TO EFFECT THE WEATHER THIS WEEKEND APPEARS MUCH STRONGER THAN THE FRIDAY SYSTEM. THE ECMWF SHOWED SOME CONSISTENCY FROM THE 20/00Z RUN WITH THIS UPPER LOW DROPPING INTO THE GREAT LAKES REGION. THE GFS HAS TRENDED THIS SYSTEM STRONGER DURING THE SAME PERIOD. THE CAVEAT IS THE PAST MODEL HANDLING OF DIGGING THIS TYPE OF SYSTEM TOWARD THE SOUTHERN STREAM. EXPECT A SLOWER SOLUTION THAT WHAT IS EVEN NOW ADVERTISED BY THE GFS AND THE ECMWF. FOR THIS PACKAGE...KEPT CHANCE POPS SATURDAY THROUGH SUNDAY WITH THE ARRIVAL OF THIS SYSTEM. POTENTIAL STILL FOR ACCUMULATING SNOW...ESPECIALLY SATURDAY NIGHT. AN EVEN SLOWER AND STRONGER SOLUTION WOULD SUPPORT ACCUMULATING SNOW INTO SUNDAY. HAVE RAISED POPS TO 50 PERCENT SATURDAY NIGHT...BUT HESITANT TO MAKE CHANGES PAST SATURDAY NIGHT GIVEN WIDE VARIETY OF POSSIBLE SOLUTIONS AND THE POTENTIAL FOR A STRONGER AND SLOWER SYSTEM. FOR MONDAY AND TUESDAY...THE CANADIAN ENSEMBLES SUPPORT A CONTINUANCE OF THE HIGH ZONAL FLOW WITH MILD TEMPERATURES...ALTHOUGH MULTIPLE SHORTWAVES WILL BE MIGRATING ACROSS THE CONUS. KEPT THE FORECAST DRY MONDAY AND TUESDAY. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM...LASHLEY UPDATE/AVIATION...GLL LONG TERM....SKIPPER in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1130 AM EST WED DEC 21 2005 .UPDATE... CLOUDS ARE NOT AS WIDESPREAD AT ORIGINALLY THOUGHT. DRY AIR OVER ILLINOIS IS SPREADING EAST. CLOUDS ASSOCIATED WITH SHORT WAVE OVER THE LOWER GREAT LAKES SLOWLY MOVING SOUTH AND ARE NOW ALONG THE INDIANA/MICHIGAN BORDER. UPDATED TO PARTLY CLOUDY AND MADE SOME MINOR ADJUSTMENTS TO TEMPERATURE FORECAST...LOWERED A COUPLE DEGREES NORTHEAST WHERE MORE CLOUDINESS IS EXPECTED AND LEFT THE REST OF THE AREA UNCHANGED. .PREV DISCUSSION... SHORT TERM... TODAY AND TONIGHT... ONCE AGAIN SKY COVER AND TEMPERATURES ARE THE FORECAST CHALLENGES FOR THE SHORT TERM PERIOD. SATELLITE SHOWS LOW STRATUS ERODING FROM WEST TO EAST ACROSS FORECAST AREA AT ISSUANCE TIME. CHALLENGE IS WHEN AND WHERE EROSION WILL END AND HOW TO PLAY SKY COVER FOR TODAY. DESPITE MISSING INGEST OF UPPER AIR DATA...00Z NAM40 IS DOING QUITE WELL MODELING CLOUD COVER IN THE VICINITY OF 925MB LEVEL WITH ITS RH FIELD. IT BRINGS DRIER AIR INTO CENTRAL AND SOUTHERN FORECAST AREA FOR A FEW HOURS THIS MORNING BEFORE BRINGING MOISTURE BACK AHEAD OF FAST MOVING SHORT WAVE SEEN IN WATER VAPOR DROPPING SOUTH THROUGH MICHIGAN. RUC40 THROUGH THE MORNING HOURS IS LESS PESSIMISTIC WITH ITS 925MB RH FIELD. THERE DOES APPEAR TO AT LEAST BE SOME MID OR HIGH LEVEL CLOUDS ACROSS WISCONSIN ASSOCIATED WITH THIS SHORT WAVE. THEREFORE PLAN TO HAVE PARTIAL CLEARING EARLY THIS MORNING WESTERN AREAS THEN INCREASE CLOUDS AGAIN BY MID MORNING NORTHWEST. WILL KEEP SOUTHWEST PARTLY CLOUDY. HAVE KEPT EASTERN AREAS MOSTLY CLOUDY WITH SOME DECREASE LATE THIS AFTERNOON BEHIND SHORT WAVE. STRONG SUBSIDENCE AND CONTINUED DRYING TONIGHT WILL SCOUR OUT MOST CLOUDS. HAVE TRENDED GRIDS TO BETWEEN 30 AND 40 PERCENT FOR NOW TO ACCOUNT FOR POSSIBLE SLOWER MOVEMENT OF CLOUDS. HAVE ALSO ADDED SOME PATCHY FREEZING FOG TO THIS MORNING AS UPSTREAM OBSERVATIONS HAVE SHOWN SOME PATCHY BR IN THE 3 TO 5 MILE RANGE FORM WHERE SKIES HAVE CLEARED AND WINDS RELAXED. AS FOR TEMPERATURES...DID DROP MAX TEMPS A DEGREE OR TWO TODAY WITH MORE CLOUDS AND COOLER MOS GUIDANCE. DESPITE WARM AIR ADVECTION ALOFT TONIGHT...ONE MORE NIGHT OF COLD TEMPERATURES STILL POSSIBLE WITH CLEARING SKIES AND WINDS UNDER 10KTS. LONG TERM... THURSDAY THROUGH TUESDAY...FINALLY APPEARS TO BE A BREAK OUT OF THE DEEP FREEZE AS THE FLOW BECOMES HIGH ZONAL. THE UPPER LEVEL RIDGE OVER WESTERN NORTH AMERICA WILL BREAK DOWN PER NCEP...ECMWF AND CANADIAN MODEL CONSENSUS. OVER THE MIDWEST...THE RETURN FLOW INCREASES THURSDAY WITH A TIGHT PRESSURE GRADIENT DEVELOPING BETWEEN THE 1025 MB SFC HIGH OVER THE SE CONUS AND THE DEEP LOW NORTH OF THE GREAT LAKES. THE NAM AND NGM APPEAR TOO ROBUST WITH THE WARM UP THURSDAY...THE NGM FWC MOS HIGH OF 44 IS 9 DEGREES WARMER THAN THE MAV HIGH OF 35 AT FWA. GIVEN SNOW COVER OVER THE FORECAST AREA OF GENERALLY 4-8 INCHES...WENT WITH THE MORE CONSERVATIVE MAV. WILL BE HARD TO MIX MUCH OF THE WARM AIR DOWN TO THE SURFACE. A WEAK SHORT WAVE SHOULD MOVE ACROSS THE AREA EARLY FRIDAY...SO HAVE KEPT A CHANCE FOR RAIN SHOWERS IN THE GRIDS/ZFP OVER NORTH AREA INCLUDING FAR SOUTHERN LOWER MICHIGAN. ISENTROPIC ANALYSIS STILL FAVORS LOWER MICHIGAN FOR THE BEST CHANCE FOR PRECIPITATION PER UPGLIDE AND SATURATION ON THE 300K SFC. THE NEXT SYSTEM POISED TO EFFECT THE WEATHER THIS WEEKEND APPEARS MUCH STRONGER THAN THE FRIDAY SYSTEM. THE ECMWF SHOWED SOME CONSISTENCY FROM THE 20/00Z RUN WITH THIS UPPER LOW DROPPING INTO THE GREAT LAKES REGION. THE GFS HAS TRENDED THIS SYSTEM STRONGER DURING THE SAME PERIOD. THE CAVEAT IS THE PAST MODEL HANDLING OF DIGGING THIS TYPE OF SYSTEM TOWARD THE SOUTHERN STREAM. EXPECT A SLOWER SOLUTION THAT WHAT IS EVEN NOW ADVERTISED BY THE GFS AND THE ECMWF. FOR THIS PACKAGE...KEPT CHANCE POPS SATURDAY THROUGH SUNDAY WITH THE ARRIVAL OF THIS SYSTEM. POTENTIAL STILL FOR ACCUMULATING SNOW...ESPECIALLY SATURDAY NIGHT. AN EVEN SLOWER AND STRONGER SOLUTION WOULD SUPPORT ACCUMULATING SNOW INTO SUNDAY. HAVE RAISED POPS TO 50 PERCENT SATURDAY NIGHT...BUT HESITANT TO MAKE CHANGES PAST SATURDAY NIGHT GIVEN WIDE VARIETY OF POSSIBLE SOLUTIONS AND THE POTENTIAL FOR A STRONGER AND SLOWER SYSTEM. FOR MONDAY AND TUESDAY...THE CANADIAN ENSEMBLES SUPPORT A CONTINUANCE OF THE HIGH ZONAL FLOW WITH MILD TEMPERATURES...ALTHOUGH MULTIPLE SHORTWAVES WILL BE MIGRATING ACROSS THE CONUS. KEPT THE FORECAST DRY MONDAY AND TUESDAY. && .AVIATION... SKIES CLEARED OUT AT KSBN AND MIST AND STRATUS QUICKLY FILLED BACK IN. KFWA APPEARS ON EDGE OF BREAKING OUT BASED ON LATEST DERIVED FOG PRODUCT. SOME HIGH CLOUDS ARE OBSCURING THE VIEW AT KFWA SO SOME UNCERTAINTY. HOWEVER...BASED ON TRENDS AND SURROUNDING OBSERVATIONS...IT APPEARS CLEARING IS WORKING SOUTHEAST. HAVE STARTED KFWA OUT SCT WITH A TEMPO BROKEN AND MVFR VIS. THE HIGH CLOUDS ARE ASSOCIATED WITH A SHORT WAVE PASSING BY. STRATUS DECK ACROSS WI AND MI BEGINNING TO MOVE SOUTH BEHIND THIS WAVE. EXPECT THESE LOW CLOUDS TO ROLL BACK INTO KSBN AND KFWA THIS MORNING. KSBN MAY TEMPORARILY LOOSE THE CURRENT CIG FROM BR AND STRATUS BUT DID NOT TRY AND TIME THAT AS APPROACH OF UPSTREAM CLOUDS SHOULD BE RATHER QUICK. MOISTURE HANGS AROUND MOST OF DAY BEFORE DRYING WORKS BACK IN LATE AFTERNOON AND EARLY EVENING. WITH LIGHT WINDS THIS EVENING...MIST AND STRATUS POSSIBLE AGAIN THIS EVENING BEFORE WINDS INCREASE OVERNIGHT. HAVE BROUGHT IN SOME MVFR BR FOR NOW. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM/AVIATION...LASHLEY LONG TERM....SKIPPER in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 217 PM CST WED DEC 21 2005 .DISCUSSION... THERE ARE TWO CONCERNS IN THE SHORT TERM FORECAST THIS AFTERNOON. FIRST IS WHETHER OR NOT LOW LEVEL STRATUS WILL REDEVELOP THIS EVENING. THE SECOND IS HOW MUCH SNOW WILL BE ON THE GROUND TOMORROW AND ITS AFFECTS ON TEMPS. 19Z WATER VAPOR IMAGERY SHOWS A MID LEVEL RIDGE OVER THE INTER-MOUNTAIN WEST WITH A SHORTWAVE TROUGH JUST OFF THE PACIFIC NORTHWEST COAST. THIS UPPER RIDGE IS EXPECTED TO PROPAGATE EAST BRINGING HEIGHT RISES TO THE FORECAST AREA. THIS WILL KEEP THE FORECAST DRY ACROSS THE AREA THROUGH THURSDAY. SO FOCUS TURNS MORE TO THE MESO SCALE FEATURES. FORECAST SOUNDINGS FROM THE NAM...RUC AND GFS SHOW A STRONG INVERSION SETTING UP AGAIN THIS EVENING WITH THE LOWEST 1000 MB BECOMING SATURATED. WITH MOISTURE FROM THE MELTING SNOW AND DEWPOINTS IN THE UPPER 30S AND LOW 40S OVER NORTHWEST OK POISED TO ADVECT NORTH...THINK THAT MOISTURE WILL AGAIN BECOME TRAPPED WITHIN THE INVERSION AND ALLOW LOW STRATUS TO REDEVELOP TONIGHT. MODELS PROG WINDS JUST ABOVE THE BOUNDARY LAYER TO BE STRONGER TONIGHT THAN LAST NIGHT...THEREFORE THINK THE POSSIBILITY FOR FOG WILL BE REDUCED WITH CEILINGS FORMING AROUND 1200 FEET OR LOWER. THERE COULD STILL BE SOME PATCHY FOG BUT DO NOT ANTICIPATE ANY MAJOR RESTRICTIONS TO VISIBILITIES. TEMPERATURE FORECAST BECOMES TRICKY DEPENDING ON CLOUD COVER FOR LOWS AND SNOW COVER FOR HIGHS. EXPECTING STRATUS ACROSS THE EASTERN TWO THIRDS OF THE FORECAST AREA...HAVE KEPT LOWS IN THE LOWER 20S WITH SOME COOLER READINGS ACROSS NORTH CENTRAL KS WHERE THERE SHOULD BE LESS CLOUD COVER. AS FOR THE SNOW COVER...VISIBLE SATELLITE SHOWS THE SNOW COVER RECEDING ALONG THE EDGES. MODELS SHOW STRONG WAA OCCURRING AT 850 ACCOUNTING FOR THE VERY WARM GUIDANCE NUMBERS. DO NOT EXPECTED TO MIX DOWN FROM 850 TOMORROW...BUT SHOULD SEE WARMER TEMPS ACROSS THE BOARD IF WE CAN MIX 925 DOWN TO THE SFC. THINK STRATUS WILL DISSIPATE BY MID TO LATE MORNING WITH DECENT MIXING IN THE BOUNDARY LAYER. EXPECT SOME SNOW TO REMAIN ON THE GROUND FOR A PORTION OF THE DAY THURSDAY WHERE THE AXIS OF HEAVIEST SNOW FELL...MAINLY FROM MHK TO ABILENE. HERE I HAVE HELD HIGHS IN THE MID AND UPPER 40S. ACROSS THE EXTREME NORTH NEAR THE STATE LINE AND OVER PORTIONS OF EAST CENTRAL KS WERE THE SNOW IS RECEDING... THINK HIGHS WILL REACH THE LOWER 50S WITH SOME MID 50S POSSIBLE AROUND GARNETT AND BURLINGTON. FRI/SAT...WEAK WAVE PASSES OVER THE STATE IN THE EARLY MORNING HOURS FRIDAY...AND COOLS MID LEVELS ABOUT 2C. SHOULD ALSO KEEP LOWS UP NEAR FREEZING. NEXT MORE AMPLIFIED WAVE APPEARS TO HOLD OFF LONG ENOUGH TO ALLOW FOR A NICE WARMUP FRIDAY. GUIDANCE COMING IN AT MID TO UPPER 50S...AND GIVEN PREVIOUS DAY WITH ABOVE FREEZING TEMPS WOULD EXPECT SNOW COVER TO BE ALL BUT GONE SO THEN RADIATION CAN LEND ITSELF TO A WARMUP INSTEAD OF SNOWMELT. FROPA FRIDAY EVENING BRINGS IN COOLER TEMPS AND NORTHWEST WINDS. WELL MIXED AIRMASS SHOULD AGAIN KEEP OVERNIGHT LOWS CLOSE TO THE FREEZING MARK. ETA TAKES UPPER TROF INTO THE UPPER MIDWEST FOR SATURDAY...WITH SOME WRAP AROUND PRECIPITATION STILL NOT RULED OUT OVER OUR AREA. HAVE KEPT POPS/WX FROM PREV FORECAST. ECMWF AND GFS HAVE TRENDED SLIGHTLY DEEPER AND STRONGER WITH THIS SYSTEM. SUN/MON...NORTHWEST FLOW ALOFT RETURNS FOR SUNDAY AND MONDAY AS COLDER AIR MOVES EAST AND TROF BUILDS WEST. MAY SEE SOME CLOUDS AND HIGHS IN UPPER 40S TO NEAR 50. TUE/WED...DIFFERENCES RETURN THESE PERIODS AS MODELS VARY ON SOLUTIONS OF WHAT TO DO WITH SHORTWAVE MOVING INTO THE AREA. 12Z RUN BRINGS SYSTEM INTO KANSAS ON TUESDAY...PREVIOUS RUN HAD WAVE APPROACHING WITH WAA OVER THE STATE. WITH MUCH UNCERTAINTY HAVE USED MAINLY HPC GUIDANCE AND MEAN TEMPERATURES. && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ WOLTERS/CRAVEN ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 400 PM EST WED DEC 21 2005 .DISCUSSION... THE MAIN CONCERN WITH THIS FORECAST PACKAGE IS POTENTIAL FOR SNOW TONIGHT AND THURSDAY. WATER VAPOR IMAGERY AND RUC/NAM SHOWING A LONGWAVE TROUGH OVER WESTERN QUEBEC...A BROAD TROUGH OVER WESTERN CONUS...AND A WEAK SHORTWAVE OVER WESTERN LAKE SUPERIOR. ANOTHER SHORTWAVE IS OVER SOUTHWEST MANITOBA. SURFACE ANALYSIS INDICATES A LOW OVER NORTHWEST MANITOBA AND A WARM FRONT EXTENDING FROM THIS LOW SOUTH INTO NORTHEAST NORTH DAKOTAS. ISENTROPIC ASCENT AHEAD OF THE WARM FRONT IS GENERATING A FEW SNOW SHOWERS OVER MANITOBA. LOW LEVEL CONVERGENCE OVER LAKE SUPERIOR...WATER-850MB DELTA-T'S OF 15C CAUSING STEEP LAPSE RATES...INSTABILITY ASSOCIATED WITH THE SHORTWAVE...AND LOW LEVEL MOISTURE COMBINE TO PRODUCE LAKE EFFECT SNOWS OVER THE NORTHERN PART OF THE U.P. THE SHORTWAVES OVER LAKE SUPERIOR WILL SHIFT INTO LAKE HURON TONIGHT AS THE SHORTWAVE OVER MANITOBA FOLLOWS INTO WESTERN LAKE SUPERIOR. ANOTHER SHORTWAVE LINES UP OVER SOUTHERN MANITOBA AND EASTERN NORTH DAKOTA. THE WARM FRONT WILL MOVE ACROSS THE FORECAST AREA INTO EASTERN ONTARIO. FOLLOWING THE FRONTAL SYSTEM THE WINDS WILL SHIFT TO THE SOUTHWEST DRAWING IN WARMER AIR. THE DELTA-T'S WILL INCREASE TO 2C OVER NIGHT. THIS ESSENTIALLY WILL CAUSE THE LAKE EFFECT SNOW TO SHIFT INTO CANADA. A LITTLE STRONGER SHORTWAVE WILL SWEEP ACROSS UPPER MICHIGAN ON THURSDAY. THE COLD FRONT MOVING ACROSS CENTRAL CANADA WILL SETTLE TO JUST NORTH OF LAKE SUPERIOR. ISENTROPIC ASCENT AHEAD OF THIS FRONT WILL GENERATE WEAK LEFT. MOISTURE WILL BE LIMITED. NAM/GFS SHOWING LOW LEVEL MOISTURE. NAM INDICATES A SURFACE BASED INVERSION WHICH WOULD TEND TO DIMINISH ANY PRECIPITATION DEVELOPING. GFS ON THE OTHER HAND HAS A 925MB INVERSION. THE SHORTWAVE ENERGY AND LOW LEVEL MOISTURE WILL TEND TO PRODUCE SOME PRECIPITATION...WHILE THE LOW LEVEL INVERSION WOULD HAVE A NEGATIVE EFFECT. GFS ALSO IS A LITTLE WARMER THAN NAM. WHAT PRECIPITATION OCCURS WILL BE MOSTLY SNOW...BUT THERE COULD BE SLIGHT CHANCE OF -FZRA/IP IN IT AS WELL. WILL STAY WITH THE SNOW FORECAST FOR NOW...BUT LOWER POPS. ANOTHER SHORTWAVE WILL SWEEP THROUGH THE FORECAST AREA THURSDAY NIGHT. ANOTHER ALBERTA CLIPPER WILL DIVE INTO MANITOBA AND THE COLD FRONT REACHING LAKE SUPERIOR. STILL KEEPING CLOUDY CONDITIONS BUT THE AIR MASS WILL BE FAIRLY DRY. ANOTHER SHORTWAVE WILL SWEEP THROUGH THE FORECAST AREA ON FRIDAY. THE COLD FRONT WILL AND ASSOCIATED COLD FRONT WILL SETTING OVER UPPER MICHIGAN. SOUNDING DATA SHOW NEARLY SATURATED CONDITIONS FROM SURFACE TO 700MB. THE FROPA AND SHORTWAVE ENERGY WILL TEND TO SQUEEZE MORE OF THE MOISTURE OUT OF THE AIR MASS. TEMPERATURE AT 850MB WILL BE AROUND 2C. THUS LOOKING FOR A CHANCE OF SNOW POSSIBLY MIXED WITH SLEET. A WEAK SHORTWAVE WILL SWEEP ACROSS THE AREA ON FRIDAY NIGHT. GEM AND ECMWF INDICATE THE MORE INTEST SHORTWAVE WILL SWING TO THE SOUTH OF THE FORECAST AREA. THE SURACE LOW WILL ALSO SWING MORE TO THE SOUTH OF THE FORECAST AREA. THE SOUTHERLY FLOW THAT WOULD THEN TRANSPIRE WOULD BRING WARMER AIR TO THE AREA. THUS THERE IS A CHANCE OF -RA OR -SN OCCURRING OVER THE AREA. THE MID LEVEL LOW WILL MOVE OVER LOWER MICHIGAN ON SATURDAY. THE Q-VECTOR CONVERGENCE ASSOCIATED WITH THIS LOW WILL SWEEP THROUGHT THE AREA. MODELS SHOW NEARLY SATURATED CONDITIONS EXISTS. THE SURFACE LOW WILL MOVE INTO THE LOWER GREAT LAKES. ANOTHER WEAK FRONTAL SYSTEM ASSOCIATED WITH THIS LOW WILL SWING THROUGH THE FORECAST AREA. LOW LEVEL MOISTURE WILL REMAIN HIGH ENOUGH TO KEEP A CHANCE OF SNOW GOING. BY 12Z SUN...THE GFS/DGEX/GFS ENSEMBLE BEGINS TO RUN ABOUT 12 HOURS BEHIND THE ECMWF/GEM. THE GFS HAS A MUCH DEEPER TROUGH NAVIGATING THROUGH THE EASTERN CONUS. BY 00Z TUE...THE CONDITIONS REVERSE... WITH THE ECMWF/GEM DEVELOPING A SECONDARY TROUGH OVER ONTARIO BUT DEEPER AND SLOWER THAN THE GFS/GFS ENSEMBLE/DGEX. AGREE WITH THE HPC DISCUSS FAVORING THE ECMWF/GEM SO WILL FAVOR THAT SOLUTION ALSO. THE DEEP MID LEVEL TROUGH OVER THE UPPER GREAT LAKES ON SUN EVENING WILL MOVE OFF SHORE BY MONDAY MORNING...WHILE ANOTHER SHORTWAVE DEVELOP OVER CENTRAL MANITOBA ON SUNDAY AND MOVES INTO CENTRAL ONTARIO ON MONDAY. THIS SECONDARY TROUGH WILL DEVELOP INTO A LONGWAVE TROUGH BY EARLY WEEK REACHING THE EAST COAST BY WEDNESDAY. MEANWHILE...THE SURFACE LOW OVER UPPER GREAT LAKES WILL MOVE INTO SOUTHWEST QUEBEC SATURDAY NIGHT DRAGGING THE COLD FRONT INTO THE EAST COAST. A SURFACE RIDGE WILL PUSH INTO THE UPPER MISSISSIPPI RIVER VALLEY ON CHRISTMAS DAY. ANOTHER SURFACE LOW IS DEVELOP OVER NORTHERN SASKATCHEWAN AND WILL SLIDE INTO LAKE SUPERIOR MONDAY MORNING DRAGGING A COLD FRONT INTO LAKE MICHIGAN. ANOTHER COLD FRONT ROTATING AROUND THIS LOW WILL SWEEP INTO SOUTHERN MANITOBA. THE LAKE SUPERIOR LOW WILL PUSH INTO EAST CENTRAL ONTARIO LATE MONDAY AS THE MANITOBA COLD FRONT MOVES THROUGH THE FORECAST AREA. A HIGH PRESSURE RIDGE WILL BE FROM MANITOBA INTO THE NORTHERN PLAINS. THE SURFACE RIDGE WILL PUSH THROUGH THE FORECAST AREA ON WEDNESDAY. AN 850MB THERMAL TROUGH WILL MIGRATE ACROSS THE FORECAST AREA PRODUCING AHEAD OF THE SURFACE RIDGE AND ALONG WITH A NORTHERLY FLOW MAY PRODUCE LAKE EFFECT SNOWS. THE AMOUNT AND EXTENT OF THE LES WILL DEPEND ON THE AVAILABLE MOISTURE AND LOW LEVEL CONVERGENCE. AS THE RIDGE MOVES ACROSS THE AREA ON WEDNESDAY...THE WINDS WILL WEAKEN AND SWITCH OUT OF THE SOUTH AND END ANY LES. && MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1208 PM EST WED DEC 21 2005 .AVIATION... MVFR CEILINGS AND AT TIME VISIBILITIES WITHIN THE SNOW WILL PERSIST FOR FNT AND MBS EARLY IN THE TAF PERIOD. AS THIS WAVE EXITS TO OUR SOUTHEAST...SOME SUBSIDENCE WILL STOP THE SNOWFALL BUT LIKELY KEEP THE CEILINGS IN MVFR CATEGORY FOR SOME TIME INTO THIS EVENING. QUESTION IS JUST HOW MUCH OF A BREAK WILL WE OBSERVE WITH DRY AIR ADVECTION UPSTREAM BEFORE THE WARM ADVECTION IN THE MID LEVELS TRAPS REMAINING MOISTURE FOR ADDITIONAL STRATUS OVERNIGHT. AS PRESSURE GRADIENT TIGHTENS FROM NORTH TO SOUTH OVERNIGHT INTO THURSDAY...THINK WE WILL SEE ENOUGH BREAKS IN THE LOW CLOUD COVER AND WE WILL GO WITH A SCT DECK. THIS WILL BE REPLACED BY INCREASING HIGH AND MID LEVEL MOISTURE WITH THE WARM ADVECTION PATTERN AND SFC WIND SPEEDS WILL INCREASE ACCORDINGLY THROUGH THURSDAY. && .UPDATE... ISSUED AT 940 AM EST LIGHT SNOW CONTINUES TO INCREASE IN COVERAGE AS WEAK SURFACE TROF APPROACHES FROM THE WEST. H2O VAPOR LOOP SHOWS STILL A WELL DEFINED SHORT WAVE DIVING SOUTHEAST WITH ENOUGH LAKE INSTABILITY TO PROVIDE THE AREA OF LIGHT SNOW (SEEN WELL ON THE GRB SOUNDING THIS MORNING WITH -11C AT 850MB). 12Z RUC PROFILES CONTINUE TO SUGGEST DRYING ALOFT WITH THE PASSAGE OF THIS SHORT WAVE BUT STILL PLENTY OF LOW CLOUDS UPSTREAM. WE SHALL SEE THE NEXT COUPLE OF HOURS TO UPDATE CLOUD COVER REACTS WITH SUBSIDENCE. UPDATED FORECAST HAS BEEN ISSUED. && .PREV DISCUSSION...ISSUED 540 AM EST WED DEC 21 2005 AVIATION... UPPER WAVE AND ASSOCIATED SURFACE TROF DROPPING SOUTHEAST TOWARD THE REGION THIS MORNING. MOISTURE IS LIMITED WITH THIS SYSTEM WITH DEEPER MOISTURE REMAINING NORTH OF SOUTHEAST LOWER MICHIGAN. AS A RESULT BEST CHANCE FOR SNOW WILL BE FROM FNT NORTHWARD BETWEEN 12-18Z. ANTICIPATE VSBYS TO BRIEFLY DROP TO 3-5 MILES IN SCATTERED SNOW SHOWER ACTIVITY...OTHERWISE ANTICIPATE MVFR CIGS TO PERSIST THROUGH THE DAY BETWEEN 015-020...GRADUALLY LIFTING TO 025 AFTER 18Z. WARM AIR ADVECTION TONIGHT AHEAD OF ANOTHER LOW PRESSURE SYSTEM WILL GRADUALLY INCREASE LOW LEVEL WIND FIELD TO 15 TO 20 KTS...AND SOME CLOUD COVER WILL LINGER THROUGH THE NIGHT AS WARM AIR ADVECTION ALOFT STRENGTHENS LOW LEVEL INVERSION. MAY SEE SOME SIGNIFICANT BREAKS IN MVFR CLOUD COVER AFTER 06Z THURSDAY. SHORT TERM...WEDNESDAY AND WEDNESDAY NIGHT SHARPENING UPPER TROF AXIS AND ASSOCIATED VORTICITY LOBE OVER OVER NORTHERN WISCONSIN DIVING SOUTHEAST TOWARD THE CWA EARLY THIS MORNING. GFS APPEARS TO HAVE A BETTER DEFINITION ON THIS WAVE AND GFS 850 MB TEMPERATURE ANALYSIS MUCH BETTER THAN THE NAM OVER THE UPPER MISSISSIPPI VALLEY...NAM APPEARS TO HAVE A 1-2 DEGREE WARM BIAS. MOISTURE ON THE LEAN SIDE WITH WAVE MOVING INTO THE CWA THIS MORNING...HOWEVER MODELS SHOWING SOME MODEST MID LEVEL OMEGA/QVECTOR CONVERGENCE OVER MAINLY THE NORTHERN CWA THOUGH 18Z IN BETTER WARM AIR ADVECTION FIELD AHEAD OF ASSOCIATED SURFACE TROF...THEN SUBSIDENCE QUICKLY MOVING BACK INTO THE REGION THIS AFTERNOON. ALSO A LITTLE CONCERNED WITH PRECIPITATION TYPE AS MOISTURE INITIALLY SHALLOW. HOWEVER WATER VAPOR LOOP SHOWING GOOD INCREASE IN MID LEVEL MOISTURE AND IR ICE CLOUD SCHEME INDICATING MOSTLY SNOW AS WELL. SO AT THIS TIME WILL INCLUDE CHANCE POPS FOR ALL SNOW NORTH HALF OF CWA THROUGH 18Z...AND SLIGHT CHANCE SOUTH WHERE ASSOCIATED SURFACE TROF IS LESS DEFINED. WEAK RIDGE TO BUILD INTO THE REGION LATE THIS AFTERNOON AND EVENING...THEN QUICKLY TRACKING EAST AS NEXT TROF AXIS MOVES INTO THE NORTHERN GREAT LAKES. AS A RESULT WARM AIR ADVECTION WILL CONTINUE OVERNIGHT...WITH 850 TEMPS WARMING TO AROUND -2C AS NOTED ON GFS SOLUTION. HOWEVER BOTH MODELS VERY DRY IN THIS WARM AIR ADVECTION FIELD AND EVEN SCOUR OUT 925 MB MOISTURE. SO WILL CONTINUE WITH A DRY FORECAST FOR WEDNESDAY NIGHT. WILL DECREASE CLOUD COVER TO PARTLY CLOUDY AFTER MIDNIGHT...BUT NOT CONFIDENT THAT MOISTURE WILL BE SCOURED OUT UNDERNEATH INVERSION. WILL LEAN TOWARD COLDER MAV TEMPS FOR TODAY AND TONIGHT AS NAM THERMAL FIELD APPEARS TO BE RUNNING A LITTLE ON THE WARM SIDE. LONG TERM... OVERALL LONGWAVE PATTERN STILL LOOKS ON TRACK...WITH BRIEF ZONAL FLOW GIVING WAY TO REAMPLIFICATION BY THE WEEKEND. GFS HAS COME MORE IN LINE WITH THE ECMWF/WRF-XX WITH RESPECT TO THE DIGGING TROUGH ACROSS THE EASTERN CONUS SATURDAY/SUNDAY. DIFFERENCES STILL EXIST... WITH DEGREE OF DIGGING...AMOUNT OF SURFACE DEVELOPMENT...AND TRACK OF THE SURFACE LOW. INITIALLY NAM/GFS HAVE BOTH TRENDED FASTER AND FARTHER SOUTH WITH THE NORTHERN WAVE TRACKING ACROSS CANADA TOWARD JAMES BAY. THIS LEADS TO A FARTHER SOUTH PLACEMENT OF THE BAROCLINIC ZONE THAT DROPS INTO THE NORTHERN GREAT LAKES THURSDAY NIGHT. STRONG WARM ADVECTION IS UNDERWAY THURSDAY/THURSDAY NIGHT...WITH GOOD WARMING/BUILDING HEIGHTS BUT LIMITED MOISTURE. FORECAST SOUNDINGS/TIME SECTIONS SHOW A FAIR AMOUNT OF MID/HIGH LEVEL MOISTURE SPREADING ACROSS THE REGION...BUT WITH LOW LEVELS REMAINING DRY. THIS SEEMS REASONABLE GIVEN THE PACIFIC ORIGINS OF THE AIRMASS...WITH HIGH PRESSURE ACROSS THE SOUTHEAST CONUS CUTTING OFF LOW-LEVEL INFLOW FROM THE GULF. WILL KEEP THURSDAY DRY...WITH THURSDAY NIGHT CONTINUING TO LOOK QUESTIONABLE. INITIAL SHORTWAVE EMBEDDED IN THE FAST UPPER FLOW SWINGS THROUGH THURSDAY AFTERNOON... WITH A STRONGER SHORTWAVE FOR FRIDAY. IN BETWEEN... NAM/GFS/WRF-XX ALL SHOW SOME DEGREE OF MID-LEVEL DRYING. HOWEVER LOW-LEVELS DO SATURATE...WITH HELP FROM THE NORTHERN BOUNDARY THAT HAS TRENDED FARTHER SOUTH TOWARD THE GREAT LAKES. CONTINUED 900MB OMEGA/WITH LOW CONDENSATION PRESSURE DEFICITS ALONG THE 280K ISENTROPIC SURFACE. NOT MUCH IN THE WAY OF SPEED OR DIRECTIONAL SHEAR...BUT WITH LIFT AND A MODEST AMOUNT OF LOW-LEVEL MOISTURE WILL OPT FOR AREAS OF DRIZZLE RATHER THAN CHANCE RAIN/SNOW. AS FOR PRECIP TYPE... TEMPERATURES ARE THE OTHER CONCERN FOR THURSDAY NIGHT. KEPT HIGHS ON THURSDAY ON THE COOL SIDE NEAR FREEZING WITH THE EXPECTATION THAT THE COLD LOW-LEVEL AIRMASS WILL BE DIFFICULT TO SCOUR OUT... ESPECIALLY WITH A LARGE RANGING SNOW PACK ACROSS THE AREA AND UPSTREAM. MODELS HAVE ALSO BACKED OFF ON THE WINDS A BIT...NOT BRINGING IN THE BETTER GRADIENT UNTIL DURING THE DAY ON THURSDAY. GOOD WARM ADVECTION WILL FOLLOW THROUGH THE NIGHT. AFTER A BRIEF INITIAL DROP...EXPECT TEMPS TO SLOWLY CLIMB THROUGH THE NIGHT. WITH BETTER MOISTURE/BETTER CHANCE FOR PRECIP...WOULD EXPECT WARMER AIR TO BE ABLE TO MIX DOWN TO THE SURFACE EASIER THROUGH PRECIP LOADING. HOWEVER...NOT EXPECTING MUCH IN THE WAY OF QPF. TEMPERATURES WILL BE HOVERING AROUND FREEZING...CLIMBING FROM THE COLD SIDE. ESPECIALLY WITH LINGERING SNOWPACK...WOULD NOT BE SURPRISED IF SOME LOCATIONS REMAINED BELOW FREEZING EVEN WITH PRECIP. THEREFORE WILL KEEP A MENTION OF FREEZING PRECIP...AREAS OF DRIZZLE OR FREEZING DRIZZLE. STRONGER SHORTWAVE SWINGS THROUGH ON FRIDAY...WITH WRF-XX SHOWING A MODEST SURFACE TROUGH ASSOCIATED WITH IT AS WELL. WITH ANOTHER SURGE OF DEEPER MOISTURE AND MORE FOCUSED LIFT...WITH LOW LEVELS ALREADY PRETTY SATURATED...WE HAVE A DECENT CHANCE FOR SEEING PRECIP. INCREASED POPS A BIT TO HIGH CHANCE...MAINLY ACROSS THE NORTHERN CWA CLOSER TO THE SHORTWAVE TRACK AND EXISTING BOUNDARY. PRECIP TYPE CONTINUES TO BE A CONCERN...ALTHOUGH WITH TEMPERATURES WARMING ABOVE FREEZING IT WILL BE A QUESTION MORE OF RAIN OR SNOW. NAM SOUNDINGS ARE BY FAR THE WARMEST WITH THE WARM WEDGE...UP TO 4C GENERALLY 900MB-850MB. HOWEVER IT IS ALSO THE DRIEST THROUGH THIS LAYER. PROGRESSION OF GFS SOUNDINGS SEEM TO INDICATE SOME COOLING THROUGH EVAPORATION...WHICH SEEMS MORE REASONABLE THAN THE NAM SOUNDINGS. SIMILAR IS TRUE WITH THE WRF-XX...ALTHOUGH IT CONTINUES TO HAVE A MUCH WARMER BOUNDARY LAYER THAN THE GFS. FOR NOW WILL CONTINUE TO EDGE TOWARD THE COLDER SOLUTION...KEEPING A MIX OF MODERATE RAIN OR SNOW THROUGH THE DAY WITH TEMPS GETTING INTO THE UPPER 30S. WITH THE SHARPER SHORTWAVE AND FRIDAY AND MORE AMPLIFIED TROUGH ON SATURDAY...WE SEE SOME WEAK SHORTWAVE RIDGING ACROSS THE AREA ON FRIDAY NIGHT. FORECAST SOUNDINGS/TIME SECTIONS SHOW DEEP MOISTURE STRIPPING AWAY ONCE AGAIN...WITH LOW LEVELS WITH DEEPER LOW LEVEL MOISTURE WITH HIGHER RELATIVE HUMIDITIES. WRF-XX/GFS CONDENSATION PRESSURE DEFICITS ARE NEAR ZERO ALONG THE 280K/UP TO 285K ISENTROPIC SURFACES. WEAK LIFT STILL PRESENT...SO IT IS HARD TO RULE OUT PRECIP CHANCES. HOWEVER WITH LACK OF DEEPER MOISTURE IT LOOKS LIKE WE WILL HAVE ANOTHER DRIZZLE POTENTIAL. WITH TEMPERATURES FALLING BACK TO JUST BELOW FREEZING...FREEZING DRIZZLE WILL BE A POSSIBILITY. COULD SEE A TEMPERATURE BUST EITHER SIDE...COLD SIDE BY NOT GETTING VERY WARM ON THURSDAY AND DROPPING BELOW FREEZING EARLY THURSDAY NIGHT OR ON THE WARM SIDE BY GETTING INTO THE UPPER 30S ON THURSDAY AND NOT FALLING VERY MUCH AT ALL OVERNIGHT WITH CONTINUED SOUTHWESTERLY FLOW AND PERSISTENT CLOUD COVER. THEREFORE WILL MENTION DRIZZLE OR FREEZING DRIZZLE THROUGH THE NIGHT. AS MENTIONED ABOVE...EXTENDED MODELS ARE COMING INTO BETTER AGREEMENT WITH THE OVERALL SYNOPTIC PATTERN...MORE TOWARD THE ECMWF/WRF-XX SOLUTIONS. DIFFERENCES CONTINUE WITH DEGREE OF TROUGHING AND HOW THE TROUGH EVOLVES...WITH THE WRF-XX DEEPER...GFS MORE POSITIVELY TILTED...AND ECMWF TAKING ON MORE OF A NEGATIVE TILT. LOW PRESSURE EXPECTED TO TRACK THROUGH THE REGION SATURDAY/SATURDAY NIGHT TIMEFRAME...WITH THE WRF-XX SOUTH OF US...ECMWF NORTH OF US...AND GFS OVER US. EXACT DETAILS REMAIN TO BE SKETCHED OUT...BUT ENOUGH CONSISTENCY IN THE LONGWAVE PATTERN TO BUMP POPS UP A BIT FOR SATURDAY/SATURDAY NIGHT. PRECIP TYPE STILL LOOKS GOOD WITH A MIX OF RAIN/SNOW INITIALLY ON SATURDAY...BUT ENOUGH COOLING THROUGH THE COLUMN FOR ALL SNOW FOR SATURDAY NIGHT. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...SMALL CRAFT ADVISORY FOR WINDS...SAGINAW BAY UNTIL 1 PM WEDNESDAY. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && $$ SHORT TERM...BGM LONG TERM....JB AVIATION.....BGM YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE). mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ABERDEEN SD 335 PM CST WED DEC 21 2005 .SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT WARM FRONT CURRENTLY LOCATED ACROSS CENTRAL SD WITH WESTERN CWA WARMING INTO THE UPPER 30S TO LOW 40S WHILE EASTERN CWA STILL STUCK AROUND 20. WARM FRONT WILL MAKE ITS WAY EAST TONIGHT...WITH LOW TEMPS ACROSS THE EAST OCCURRING THIS EVENING. RUC SHOWING IMPRESSIVE THERMAL RIDGE AND WAA INTO THE EVENING HRS. EXPECT TEMPS TO CLIMB THIS EVENING ONCE WINDS TURN MORE WSW. WILL BE A MILD NIGHT ALL ACROSS CWA AS THERMAL RIDGE WILL BE IN PLACE. TWO WAVES AFFECT AREA DURING THE PERIOD WITH THE FIRST MOVING THROUGH LATE THURS AFTERNOON AND EXITS BY FRI MORNING. NOT TOO IMPRESSED WITH THIS FEATURE AS MOISTURE AND DYNAMICS APPEAR TO BE LACKING. KEPT SLIGHT CHANCE POPS GOING...WITH THE POSSIBILITY FOR FREEZING PRECIP LATE THURS NIGHT. LOOKS WARM ENOUGH FOR ALL RAIN SHOWERS/SPRINKLES IF ANYTHING WERE TO GET GOING OUT WEST TOMORROW AFTERNOON. BETTER LOOKING SYSTEM MOVES THROUGH THIS WEEKEND. MORE IMPRESSIVE MOISTURE AND LIFT NOTED...AS WELL AS UPPER DIVERGENCE. INCREASED POPS FOR THIS EVENT AND FEEL BEST CHANCE FOR PRECIP WILL BE FRI AFTERNOON AND FRI NIGHT FROM WEST TO EAST ACROSS THE CWA. STILL LOOKS TO BE RATHER MILD WITH THIS SYSTEM SO KEPT EVERYTHING RAIN DURING THE DAY FRIDAY AND CHANGING OVER TO SNOW OVERNIGHT. MAY ALSO SEE WRAP AROUND LIGHT SNOW OR SNOW SHOWERS ON SAT AS SYSTEM DEPARTS. TEMPERATURES WERE CHANGED LITTLE WITH MOST DIFFICULT PERIOD BEING TONIGHTS LOWS WITH STRONG WAA PATTERN AND TIMING PASSAGE OF WARM FRONT. .LONG TERM...SUNDAY THROUGH WEDNESDAY WESTERN US UPPER LEVEL RIDGE WITH EASTERN TROUGH PATTERN TO CONTINUE THROUGH THE EXTENDED RANGE. GFS/ECMWF SHOWING SOME DISAGREEMENT WITH THE HANDLING OF AN UPPER LOW UNDERCUTTING THE RIDGE EXPECTED TO IMPACT THE CENTRAL US TUESDAY. GFS IS MUCH FASTER WITH THE SYSTEM BRINGING IT INTO THE PLAINS BY TUESDAY...WHILE THE EC ADVERTISES A SLOWER SOLUTION KEEPING THE SYSTEM FURTHER WEST OVER THE ROCKIES AND BRINGING IT MORE ACROSS THE SOUTHERN PLAINS. LATEST MODEL PREFERENCES SEEM TO LEAN TOWARD THE SLOWER EC SOLUTION. THEREFORE LEFT THE FORECAST DRY FOR TUESDAY INTO TUESDAY NIGHT. OTHERWISE WITH THE LARGE RIDGE PATTERN ACROSS THE WEST...CWA STAYS ON THE SOUTHERN EDGE OF THE COLD AIR AND COULD END UP SEEING FAIRLY MILD CONDITIONS INTO THE BEGINNING OF NEXT WEEK. GFS SOLUTION IS THE COOLEST OF ALL THE LONG RANGE MODELS...SO STUCK WITH HIGHS...OUT WEST ESPECIALLY...SLIGHTLY HIGHER THAN MEX GUIDANCE. PREVIOUS FORECAST LOOKED ON TRACK...SO ULTIMATELY MADE LITTLE CHANGES. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ TT/SK/MA sd