AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PADUCAH KY 200 PM CST SAT JAN 20 2001 MAIN FORECAST CHALLENGES NEXT COUPLE OF DAYS INVOLVE BOTH CLOUDS AND TEMPERATURES. EARLY THIS AFTERNOON...VISIBLE SATELLITE LOOP SHOWS MOST OF THE STRATO-CU WAS EAST OF A LINE FROM KVIH IN EAST CENTRAL MO TO KPOF IN THE WESTERN REACHES OF OUR CWFA. DIURNAL TENDENCY HAS RESULTED IN A FILLING WHERE SUNSHINE HAS OCCURRED. HOWEVER...SATELLITE DOES SUGGEST AN OVERALL EASTWARD MOVEMENT...AND BOTH THE RUC AND ETA SHOW A RAPID DECREASE IN MOISTURE AT AND BELOW 900MB THROUGH THE EARLY EVENING. THUS WILL HAVE CLEARING/CLEAR WORDING THIS EVENING. CANNOT RULE OUT A FEW FLURRIES LATE TODAY...BUT DO NOT PLAN ON MENTIONING IN ZFP...AS THIS THREAT SHOULD BE OVER RELATIVELY SOON. FOR THE OVERNIGHT HOURS...THE AVN HAS DEPICTED VERY WELL THE HIGH LEVEL MOISTURE OVER THE PLAINS (SEEN VIA AVN 400MB RH/IR CONTOUR OVERLAY). AVN TRANSLATES MOST OF THIS HIGH LEVEL MOISTURE OVER THE SW 1/2 OF OUR FA TONIGHT...ALTHOUGH IT WILL LIKELY AFFECT ALL AREAS. THUS WILL GO AHEAD AND MENTION IN THE ZFP FOR THE OVERNIGHT HOURS. WILL KEEP CURRENT ZFP LOWS GOING. THEY JIVE WELL WITH LATEST MOS. A SURFACE RIDGE SEEN JUST TO OUR WEST ON THE 18Z MAP WILL SHIFT OVERHEAD TONIGHT. AND...THERE IS JUST A BIT OF SNOW (NOT MUCH) ON THE GROUND. TRUE RADIATION MAY NOT BE REALIZED AS SOME CLOUDS EXPECTED...BUT NOT ENOUGH EVIDENCE TO CHANGE GOING NUMBERS. CURRENT WATER VAPOR LOOP SHOWS STRONG UPPER LOW CIRCULATION OVER COLORADO. IT IS FORECAST BY THE ETA/AVN TO DIG SE ACROSS NORTH TEXAS AND THEN TURN EAST ACROSS THE GULF COAST STATES TONIGHT THROUGH MONDAY. EXPECT HIGH LEVEL MOISTURE WILL CONTINUE TO AFFECT THE FORECAST AREA THROUGH MONDAY AT TIMES. BOTH THE ETA AND AVN SUGGEST SOME LOW-LEVEL MOISTURE WILL MOVE THROUGH SUNDAY NIGHT INTO EARLY MONDAY AS A WEAK 850MB FRONT APPROACHES FROM THE NORTHWEST. FORCING VERY LIMITED AND IT WEAKENS TO NIL WITH TIME. THIS AND THE FACT THAT THE NGM AND MOS GUIDANCE NOT SHOWING MUCH IN THE LOW-LEVELS...WILL PLAY IT MORE OPTIMISTIC...EXCEPT SUNDAY NIGHT WHEN UPPER LEVEL MOISTURE MAY BE MORE SIGNIFICANT SOUTHERN SECTIONS (CLOSEST TO THE UPPER LOW). PARTLY CLOUDY AVERAGE SHOULD WORK. PLAN ON WORDING MOSTLY CLOUDY SOUTHERN SECTIONS SUNDAY NIGHT. WILL TREND UP A CATEGORY ON TEMPERATURES FOR BOTH SUNDAY AND MONDAY AS WESTERLY COMPONENT WILL BE IN THE WORKS...SFC THROUGH 850MB. IN THE EXTENDED...AVN SUGGESTS NEXT PRECIPITATION CHANCE IS WEDNESDAY AND COULD BE EITHER RAIN OR SNOW. TO CLOSE TO CALL...AND TOO FAR OUT...THUS CURRENT RAIN/SNOW WORDING LOOKS GOOD. NCEP AND MOS GUIDANCE KEEPS US BELOW CLIMO...BUT THIS DOES NOT SUPPORT LATEST MODEL GUIDANCE OR CONTINUITY...SO WILL MAINTAIN. OTHERWISE EXTENDED PROGNOSIS IS FOR A STRONG SYSTEM TO EJECT INTO THE PLAINS BY FRIDAY...RESULTING IN OUR NEXT CHANCE FOR WHAT SHOULD BE ALL RAIN. THIS CHANCE COULD LAST INTO SATURDAY. OTHERWISE...THE OTHER DAYS THIS WEEK...INCLUDING TUESDAY AND THURSDAY APPEAR TO BE QUIET. .PAH...NONE. NOLES ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE/WASHINGTON 900 PM EST SAT JAN 20 2001 ...FORECAST ON TRACK GIVEN CURRENT TRENDS AND LATEST MODEL DATA... UPR LVL LOW OVR FAR SW VA/NE TN AT 00Z WILL MOVE JUST N OF DUE E WITH THE CENTER PASSING JUST S OF THE AREA BETWEEN 06Z AND 10Z. THIS WILL PUT MUCH OF THE CWA (ESP THE NORTHERN 1/2) IN A FAVORABLE REGION FOR SN. MODELS SHOW A LARGE AREA OF DEEP MOISTURE CROSSING THE AREA BETWEEN 03Z AND 10Z WITH GOOD UVVS. IN ADDTN...MODEL SOUNDINGS SHOW STEEP MID LVL LAPSE RATES IN EXCESS OF 8C/KM WHICH COULD RESULT IN ELEVATED INSTABILITY WHICH COULD MEAN SOME CONVECTION/ENHANCED BANDS WHICH OF COURSE WOULD INCREASE SNOWFALL AMOUNTS. IR SATELLITE IMAGERY SHOWS SOME ENHANCEMENT OF THE CLOUDS ASSOCD WITH THE UPR LVL LOW THIS EVE AND EXPECT THIS ENHANCED AREA TO CONTINUE TO TRANSLATE EWD AS THE UPR LVL LOW MVS EWD. IN ADDTN...RADAR SHOWS A LARGE AREA OF SN TO THE N OF THE UPR LVL LOW. BOTH RADAR AND SATELLITE TRENDS SUGGESTS THAT A BAND OF UVVS IS DEVELOPING IN ASSOCN WITH THE UPR LVL SYSTEM AND THIS BAND OF UVVS SHUD CROSS MUCH OF THE CWA OVERNIGHT WITH THE HIGHEST UVVS CROSSING THE NRN 1/2 OF THE CWA. 18Z ETA AND 00Z RUC CONTINUE THE TREND OF THE 12Z MODELS. THE 18Z ETA GIVES DCA ABOUT 1/4 INCH OF LIQUID WITH THE 00Z RUC BEING SIMILIAR. QPFS INCREASE AS YOU HEAD NE TOWARD THE PA BORDER. THE 00Z RUC SNOW ACCUMULATION FCST STILL GIVES MOST LOCATIONS IN THE WARNING AREA 3 TO 4 INCHES WITH THE MAX BEING OVR 5 INCHES ACROSS FAR NE MD. THE RUC HAS A SNOWFALL MINIMUM OF LESS THAN 1 INCHES FROM CHO SOUTHWARD. GIVEN LATEST MODEL QPFS...THE 00Z RUC SNOW ACCUM FCST AND CURRENT RADAR/SATELLITE TRENDS I THINK THE FCST IS PRETTY MUCH IN LINE AND NO MAJOR CHGS WILL BE MADE TO THE 1ST PD. PLACEMENT OF HIGHEST UVVS AND TRACK OF UPR LVL LOW CENTER DEFINATELY SUGGEST NRN 1/3 OF THE CWA WILL SEE THE HIGHEST SNOWFALL AMTS. IN THE WARNING AREA...THINK MOST AREAS WILL SEE 2 TO 4 INCHES OF SNOW BUT IN AREAS THAT SEE CONVECTIVE SNOWFALL AND IN THE NORTHERN COUNTIES...AMTS TO 6 INCHES ARE POSSIBLE SO PLAN ON LEAVING THE RANGE AT 3 TO 6 INCHES IN THE WARNING AREA. TOWARD THE SRN END OF THE WARNING AREA...AMTS SHUD BE CLOSER TO 3 INCHES WITH AMTS GRADUALLY INCREASING AS YOU HEAD NWD. IN THE ADVISORY AREA...2 TO 4 INCHES LOOKS GOOD ALTHOUGH A GOOD PORTION OF THE ADVY AREA MAY END UP ON THE LOW SIDE OF 2 TO 4 SINCE THE FURTHER S YOU GO...THE LESS THE SNOWFALL SHOULD BE. ONLY CHGS TO THE 1ST PD FCST WILL BE TO CLEAN UP THE WORDING. RA/SN LINE AT 02Z EXTENDED FROM BWI TO DCA BUT WAS MOVING EWD SO BY THE TIME ZNS ARE OUT THINK ALL THE PCPN WILL BE IN THE FORM OF SN. UPR LVL LOW PULLS AWAY FROM THE AREA ON SUN AND SFC HIGH PRES BEGINS TO BUILD INTO THE REGION. MODEL SOUNDINGS ARE INDICATING NO MOISTURE AND STRONG DOWNSLOPING NW FLOW SHUD PREVENT FORMATION OF ANY SIGNIFICANT STRATOCU OR CU E OF THE FAR WRN RDGS. PLAN ON CHANGING 2ND PD FCST TO READ M/S E OF THE FAR WRN RDGS. WILL CONTINUE TO MENTION P/C SKIES WITH A FEW FLURRIES FAR WRN RDGS. NO CHGS 3RD OR 4TH PDS. NEXT SYSTEM THRU HERE LATE WED/THU. LOOKS LIKE ONLY A LOW CHC OF PCPN WITH THIS NEXT FEATURE AND ANY PCPN SHUD BE LIGHT. FCSTID = 15 / DMW DCA 27 34 22 38 / 100 10 0 0 BWI 25 33 18 38 / 100 10 0 0 MRB 22 33 17 37 / 100 10 0 0 IAD 21 33 16 36 / 100 10 0 0 CHO 26 37 18 38 / 90 10 0 0 HGR 21 32 15 35 / 100 10 0 0 NHK 28 36 21 38 / 90 10 0 0 .LWX...WINTER STORM WARNING TONIGHT FOR DCZ001-MDZ002>007-009>011- 013-014-VAZ021-026>031-038>042-051>054-WVZ048>055- WINTER WEATHER ADVISORY TONIGHT FOR MDZ016>018-VAZ025-036- 037-050-055>057- SCA MD PORTION OF THE CHES BAY AND TIDAL POTOMAC md AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 820 PM EST SAT JAN 20 2001 ... MOSTLY CLEAR TONIGHT ??? .... THE BIG QUESTION FOR THE FORECAST FOR THE REST OF THE NIGHT IS WILL THE AREA OF BROKEN TO OVERCAST SC (BETWEEN MKG...GRR...NILES AND SBN) CLEAR OFF OVERNIGHT? SOUNDING FROM AROUND THE GREAT LAKES SHOW THE INVERSION HEIGHT IS NEAR 930 MB. GOES SOUNDER DATA SUGGESTS THE INVERSION HEIGHT IS LOCALLY HIGHER NEAR THAT CLOUD PATCH (NEAR 900 MB). THE RUC 1000/850 RH... OR THE RUC 925 RH SHOW THIS CLOUD PATCH VERY NICELY THIS EVENING... THE HIGHEST RH ON THE RUC WAS OVER SOUTHWEST MICHIGAN... WERE THE CLOUDS ACTUALLY ARE. THIS IS AN AREA OF WAA AND THE RIDGE FROM THE SURFACE THROUGH 850 MB IS CURRENTLY OVER THE WEST SHORE OF LAKE MICHIGAN (00Z). THAT PUTS THIS AREA IN ANTICYCLONIC WIND FLOW. THIS IS ALSO WERE THE RUC SHOWS THE LOWEST MEAN RH FROM 1000 TO 850 MB. GIVEN THE CONTINUED WAA AT LOW LEVELS AND THE ASSOCIATED SUBSIDENCE BETWEEN THE SHORTWAVE OVER LK SUPERIOR AND LARGE SYSTEM TO OUR EAST AND SOUTHEAST... I STILL BELIEVE AS THE DAY SHIFT FORECASTER SUGGESTED... THAT THOSE CLOUDS WILL DISSIPATE THIS EVENING. IR LOOPS SUGGEST THE GENESIS AREA FOR THE CLOUDS HAS MOVED ONSHORE. THAT SUPPORTS THE CLEARING IDEA VERY NICELY. WHILE I STILL HAVE SOME QUESTION IF THE CLOUDS WILL REALLY TOTALLY CLEAR (SINCE THE INVERSION HEIGHT REMAINS BETWEEN 2000 AND 3000 FT THROUGH THE NIGHT AND THE WAA IS WEAK) THE TREAD IS THERE AND IT IS CLEAR ELSEWHERE OVER SOUTHWEST MICHIGAN. SO... FOR THE SOUTHWEST CORNER OF THE GRR CWA... I WILL FCST BECOMING MOSTLY CLEAR. I WILL LEAVE THE REST AS IS. THERE IS AN AREA OF BROKEN TO OVERCAST SC/AC ASSOCIATE WITH THE NEXT SHORTWAVE (OVER LAKE SUPERIOR) AND COLD FRONT. HOWEVER... THE MOISTURE FROM THAT SYSTEM DOES NOT ENTER THE GRR CWA UNTIL AFTER 09Z. SO...I WILL... AS MENTIONED ABOVE... LEAVE THE REST OF THE FORECAST AS IS. .GRR...NONE. WDM mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1030 PM EST SAT JAN 20 2001 WATER VAPOR AND RUC SHOW LAST VORT LOBE ROTATING AROUND UPPER LOW HAS CROSSED WESTERN CAROLINAS. SNOW ON THE DECREASE ALONG TN LINE AND SURVEY OF COUNTIES INDICATED LESS THAN 3 INCHES GENERALLY... AND TAPERING OFF. 4 TO 5 INCHES FELL IN MADISON AND YANCEY COUNTIES AND THEY COULD SEE A BIT MORE FOR NEXT FEW HOURS. WILL LET WARNING AND ADVISORY EXPIRE BUT WILL MENTION ISOLATED ADDITIONAL ACCUMULATIONS RIGHT ALONG TN LINE...WHERE HIGHEST SNOW TOTALS HAVE BEEN REPORTED. STRONGEST SURFACE PRESSURE RISES IN EASTERN FA AND SHOULD SEE GRADIENT BEGIN TO RELAX LATER TONIGHT. WIND CHILL WILL ONLY DROP TO ZERO TO 5 BELOW BEFORE WIND DIES DOWN. BIGGEST CHANGE THIS UPDATE WILL BE TO MOUNTAINS. DELGADO .GSP... GA...NONE. NC...NONE. SC...NONE. sc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NASHVILLE TN 300 PM CST SAT JAN 20 2001 FORECAST QUANDARIES...CLOUD COVER AND TEMPS... CURRENT ASOS/AWOS OBSERVATIONS AND REGIONAL SATELLITE DEPICTIONS SHOWING LOW LEVEL MOISTURE CONTINUANCE...WITH CEILINGS IN 15KFT- 20KFT RANGE. MSAS/SFC HAND ANALYSES SHOWING TEMPS MAINLY IN THE MID TO UPPER 20S...DEWPOINT DEPRESSIONS RANGING 5 DEGREES EAST TO NEAR 10 DEGREES WEST...UNDER NWLY FLOW. HIGH PRESSURE BUILD INTO W TN FROM COASTAL TX...PROVIDING A CLR LINE NEAR THE MS RIVER. RUC UPPER AIR CHART DEPICTIONS SHOWING 500MB...536 DAM UPPER LEVEL LOW APPROACHING BWG...WITH SWLY TRAILING TROUGH AXIS THROUGH CWA. UPPER LEVEL FLOW BECOMING PROGRESSIVELY NWLY WITH HEIGHT. REGIONAL RUC SOUNDING PROFILES SHOWING LOW LEVEL MOISTURE ONLY PREVALENT THROUGH THE BOUNDARY LAYER AND PRECIP WATER VALUES AROUND 0.25 INCH. RADAR MOSIAC IMAGERY SHOWING SOME REDEVELOPMENT OF SNOWFALL OCCURRING ACROSS NW COUNTIES. 12Z SAT REGIONAL MODEL RUNS EVOLUTION THROUGH 12Z MON IN GENERAL AGREEMENT...ESPECIALLY IN THE LOWER LEVELS. ETA/AVN DUE DIFFER AFTER 12Z MON ON PLACEMENT OF UPPER LEVEL LOW PRESSURE SYSTEM ACROSS SE COASTAL STATES...WITH THE AVN HAVING A MORE N SOLUTION. LATEST MODEL DIAGNOSTIC DISCUSSION PREFERS LOW PLACEMENT A LITTLE FARTHER SE INTO CNTRL GA...BUT NOT AS FAR S AS THE ETA. HOWEVER... FASTER AVN SOLUTION PREFERRED OVERALL FOR THE UPCOMING FORECAST PERIOD. AVN SOLUTION ALSO INITIALIZED BEST WITH UPPER LEVEL LOW STRENGTH THIS AFTERNOON. THUS...WILL LEAN TOWARD AVN. WITH LIGHT SNOW TAPERING OFF TO FLURRIES ACROSS THE NORTHERN CUMBERLAND PLATEAU PRESENTLY...PLAN BY PRESS TIME TO CANCEL SNOW ADVISORY FOR THIS AREA. WILL MENTION SCATTERED LIGHT SNOW SHOWERS THIS EVENING NORTHERN PORTIONS AND NORTHERN PORTIONS OF THE CUMBERLAND PLATEAU DUE TO RECENT RADAR TRENDS. UPPER LEVEL LOW EXPECTED TO MOVE E OF REGION BY 00Z SUN...WITH UPPER LEVEL FLOW BECOMING ZONAL. AVN BUILDING SFC HIGH PRESSURE INTO THE AREA AND DEVELOPING AN UPPER LOW OUT OF THE TX PANHANDLE...MOVING IT TO SW MS BY 00Z MON. SFC PATTERN WILL CONTINUE TO STRENGTHEN WITH UPPER LEVEL LOW MOVING EASTWARD INTO CNTRL GA BY 12Z MON. LOOK FOR THIS UPPER LEVEL SYSTEM TO BRING ONLY ADDITIONAL CLOUDINESS AND NO RAINFALL TO THE MID STATE. THUS...MAIN FORECAST QUANDARY CENTERS AROUND CLOUD COVERAGE. WILL MENTION EARLY EVENING CLOUDINESS WEST AND THROUGH MIDNIGHT PLATEAU...WITH DECREASING CLOUDINESS AFTERWARDS. SKIES WILL REMAIN PARTLY SUNNY REGION WIDE THROUGH SUN MORNING...WITH INCREASING CLOUDINESS FROM THE W...ESPECIALLY IN THE UPPER LEVELS...BY 00Z MON...AS AN UPPER LOW MOVES INTO SW MS. MID LEVEL CLOUDINESS WILL INCREASE THROUGH 12Z MON AND HELP "ASSIST" UPPER LEVEL CLOUDINESS IN PROVIDING MOSTLY CLOUDY SKIES THROUGH 12Z MON. WITH UPPER LEVEL LOW MOVING INTO THE CAROLINA/S BY 00Z TUE... UPPER LEVEL RIDGING WILL BUILD INTO THE REGION...AND ALONG WITH A CONTINUANCE IN SFC RIDGING...SHOULD SUPPORT PC SKIES. EXTENDED...RIDGING WILL CONTINUE TO BE THE DOMINATE WEATHER SCENARIO THROUGH AT LEAST 06Z WED...UNTIL INCREASING CLOUDINESS ASSOCIATED WITH AN UPPER LEVEL LOW DEVELOPING OUT OF THE TX PANHANDLE...MOVES ACROSS THE MID STATE BY 00Z THU...PROVIDING THE NEXT CHANCE OF RAINFALL. STRONG RIDGING OUT OF THE MIDWEST WILL BUILD INTO THE REGION LATER IN THE DAY ON THU...PROVIDING FOR PARTLY CLOUDY SKIES THROUGH 00Z SAT. TEMPS...MODELS TRADITIONALLY DUE NOT HANDLE LOW TEMPERATURE FORECAST WELL WITH SNOW COVER. MOS VALES MAY BE TOO HIGH FOR BNA...AND WILL LEAN TOWARD MORE REALISTIC AVN FAN GUIDANCE TEMPS EXPECTED TO RISE NEAR 40 SUN BNA...SO EFFECTS OF SNOW COVERAGE MIGHT BE DIMINISHED DUE TO MELTING...ESPECIALLY WEST. WILL GO WITH A "MESH" OF MOS VALUES FOR THE REMAINDER OF THE FORECAST PERIOD. PRELIMINARY NUMBERS FOR COORDINATION PURPOSES ONLY... BNA 017/039/028/046 4000 CSV 017/036/023/041 4000 .BNA...NONE. 14 JBW tn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NASHVILLE TN 948 AM CST SAT JAN 20 2001 CURRENT ASOS/AWOS OBSERVATIONS AND REGIONAL SATELLITE DEPICTIONS SHOWING PERSISTENT LOW LEVEL CLOUDINESS. RADAR MOSIAC IMAGERY CONTINUING TO SHOW BANDS OF HIGHER REFLECTIVITY...RESULTING IN LIGHT SNOWFALL...MAINLY WEST OF INTERSTATE 65. SEVERAL REPORTS OF SNOWFALL RANGING FORM FLURRIES TO LIGHT SNOWFALL...WITH ACCUMULATIONS GENERALLY ONE QUARTER OF AN INCH OR LESS. UPPER LOW OVER THE SOUTHERN OHIO VALLEY IN EXTREME W KY PRESENTLY...AND IS STILL EXPECTED TO MOVE ACROSS S KY DURING THE DAY...WITH AN 18Z POSITION NEAR BOWLING GREEN KY. 12 KOHX SOUNDING SHOWING MOISTURE DEPTH THROUGH 700MB...PRECIP WATER VALUES 0.25-0.30...AND TOTAL TOTALS AROUND 25. SOUNDING FORECASTED HIGH IN THE MID 30S HIGHLY UNLIKELY. CURRENT TEMPERATURES ARE REMAINING IN THE MID TO UPPER 20S REGION WIDE...AND RUC RH PROGS SHOWING CONTINUANCE IN LOW LEVEL MOISTURE THROUGHOUT THE DAY. SEE NO NEED TO MODIFY THE HIGH TEMPERATURE VALUES AT THIS TIME. BANDS OF SNOWFALL COULD PRODUCE BRIEF LOCALIZED MODERATE SNOWFALL DURING THE REMAINING MORNING HOURS...BUT DO NOT BELIEVE THAT ANY MAJOR ADDITIONAL ACCUMULATIONS WILL RESULT..."BUSTING" THE ADVISORY CRITERIA. SO WILL CONTINUE TO KEEP THE ADVISORIES GOING AT LEAST THROUGH NOON...AND WILL REVALUATE THE SITUATION AT THAT TIME. ...ESPECIALLY ACROSS CWA/S WESTERN PORTIONS. THUS...NO UPDATES PLANNED AT THIS TIME. .BNA...SNOW ADVISORY FOR NORTHERN PORTIONS OF CWA CONTINUING THROUGH 2200Z(400 PM CST)... 14 JBW tn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 355 AM EST SUN JAN 21 2001 SHORT TERM DISCUSSION... CONCERNS IN THE SHORT TERM...WHICH IS SUNDAY MORNING THROUGH TUESDAY MORNING...CONTINUE TO REVOLVE AROUND THE CLOUD FORECAST AS IS OFTEN THE CASE THIS TIME OF YEAR. ALOFT...SHORTWAVE WILL SWING THROUGH THE GREAT LAKES TODAY...WITH NORTHWEST FLOW TONIGHT...MORE OF A ZONAL FLOW ON MONDAY...BEFORE THE NEXT SHORTWAVE DROPS INTO WI BY TUESDAY MORNING. PRECIPITATION CONCERNS REALLY DO NOT BECOME A QUESTION UNTIL LATE MONDAY NIGHT IN ADVANCE OF THE AFOREMENTIONED SHORTWAVE. DOWN AT THE SURFACE...A LOW LEVEL REFLECTION OF THE SHORTWAVE MOVING THROUGH TODAY IS SEEN ACROSS THE U.P. THIS BOUNDARY MOVES SOUTH TODAY...BEFORE WASHING OUT OVER THE AREA TONIGHT. SOUTHWEST FLOW AND WAA DEVELOP ON MONDAY AHEAD OF THE NEXT WAVE/S SURFACE COLD FRONT WHICH MOVES TO THE WI SHORE OF LK MI BY TUESDAY MORNING. TODAY...SHORTWAVE DROPPING SOUTHWARD WILL BRING COLDER AIR IN ITS WAKE. 850MB TEMPS DROP TO AROUND -10 ACROSS CENTRAL LK MI BY MIDDAY AND -8 C ACROSS THE SOUTH. THIS SHOULD BE ENOUGH FOR LAKE CLOUD GENERATION. IN ADDITION...AREA OF COLD AIR STRATOCU ALONG AND BEHIND THE SURFACE BOUNDARY IS PROGD TO SINK SOUTH ACROSS THE FORECAST AREA. RUC AND ETA 925MB RH PROGS SHOW THIS RATHER WELL. SO...WILL USE A BECOMING MOSTLY CLOUDY WORDING NORTH...AND PARTLY CLOUDY IN THE MORNING...INCREASING CLOUDS IN THE AFTERNOON SOUTH. PRECIPITATION DOES NOT APPEAR TO BE A PROBLEM AS MOISTURE IS VERY SHALLOW WITH THIS WAVE. TONIGHT...MODEL SOUNDINGS INDICATE A SUBSIDENCE INVERSION IN PLACE WITH PLENTY OF MOISTURE TRAPPED BENEATH IT. ETA HAS DONE A VERY GOOD JOB WITH LOW CLOUDS THE LAST FEW DAYS AND WILL USE IT FOR GUIDANCE TONIGHT. WILL THEREFORE RUN WITH A MOSTLY CLOUDY WORDING ALL ZONES. ON MONDAY...WAA SHOULD AID IN BUSTING OUT THE CLOUDS SOME...SO WILL GO WITH A BECOMING PARTLY CLOUDY WORDING AGAIN. MONDAY NIGHT...WAA MID AND HIGH CLOUDS ADVECT ACROSS THE AREA...SO BECOMING MOSTLY CLOUDY SHOULD WORK. SOME LIGHT SNOW IN THE ZONE OF WAA IS POSSIBLE IN THE FAR NORTHWEST UP TOWARD LUDINGTON LATE...BUT WILL HOLD OFF ON INTRODUCING THIS YET. MODEL SOUNDINGS INDICATE QUITE A BIT OF DRY AIR BETWEEN 4 AND 10K FT AT MKG AT 700AM TUES MORN. WILL SIDE WITH THE COOLER AVN MOS HIGHS TODAY...BUT MAY HAVE TO BUMP UP THE MINS TONIGHT A BIT WITH THE CLOUDS. WON/T STRAY FAR FROM GUIDANCE TEMPS NGM/AVN ON MON/MON NIGHT. DUKESHERER EXTENDED FORECAST DISCUSSION... WILL ONLY MAKE A FEW SMALL CHANGES TO THE GOING EXTENDED FORECAST IN ORDER TO BETTER LINE UP WITH THE LATEST GUIDANCE FROM THE CANADIAN... AVN... AND ECMWF. THE CANADIAN IS THE MOST PROGRESSIVE OF THE THREE MODELS DURING THE PERIOD... AND BRINGS TUESDAY/S SHORTWAVE THROUGH EARLIER THAN THE AVN AND ECMWF. IT ALSO BRINGS THE NEXT SYSTEM INTO THE AREA ON FRIDAY... A GOOD 24 HOURS AHEAD OF THE AVN... AND ABOUT 12 HOURS AHEAD OF THE ECMWF. THE AVN HAS TRENDED TOWARD A FASTER PROGRESSION OF FEATURES IN COMPARISON TO LAST NIGHT/S MRF... SO WILL TREND THE FORECAST A BIT IN THAT DIRECTION AS WELL. WITH THAT SAID... MOST OF THE FORECAST CAN REMAIN THE SAME. THE SHORTWAVE AND COLD FRONT ON TUESDAY WILL BRING A CHANCE FOR A FEW SNOW SHOWERS... WITH ARCTIC AIR SURGING IN BEHIND THE FRONT TO HELP KEEP A CHANCE OF LAKE EFFECT SNOW SHOWERS IN THE FORECAST THROUGH WEDNESDAY. RIDGING BUILDS IN FOR THURSDAY... SO THE CURRENT PARTLY CLOUDY FORECAST LOOKS GOOD. WILL BRING A CHANCE OF SNOW OR RAIN INTO THE FORECAST BY LATE FRIDAY... TO TREND THINGS TOWARD A FASTER SOLUTION... AND WILL JUST MENTION A CHANCE OF SNOW ON SATURDAY WITH THE THOUGHT THAT CAA WILL BE OCCURRING AT THAT POINT. .GRR...NONE. mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DULUTH MN 230 AM CST SUN JAN 21 2001 S/WV OVR WRN GRT LKS LEAVING THE PICTURE EARLY THIS MORNING WITH SKIES CLEARING OVR MOST OF CWA. ANOTHER WK S/WV APPROACHING FROM DAKOTAS RESULTING IN MORE CLDS BUT APPARENTLY NOT MUCH PRECIP. CURRENT TRENDS INDICATING THIS BATCH OF CLOUDS HAVING A HARD TIME PENETRATING DRY AIR OVR CWA ATTM. RUC SEEMS TO DESCRIBE MSTR DISTRIBUTION BTR THAN MESOETA AND DOES NOT SHOW MUCH EWD PROGRESS OF THESE CLDS. THIS MAKES CLD FCST FOR 1ST PD DIFFICULT. WILL PRBLY STICK WITH PARTIAL CLRG WORDING FOR NW WI AND SOME FORM OF MOSUN OR PCLDY FOR NE MN DEPENDING ON TRENDS BTWN NOW AND PRESS TIME. BEYOND THAT...MODELS IN GOOD AGMT ON TIMING AND STRENGTH OF UPR RDG WHICH WILL DOMINATE OUR WEA THIS AFTN THRU MON MRNG...AND THE NXT S/WV APPROACHING MON EVE. TIME/XSCTNS ARE INDICATING THAT THIS SYSTEM WILL HAVE A LTL DEEPER MSTR THAN PREVIOUS ONES...AND WITH A MOD AMT OF LIFT COULD PRODUCE AN INCH OR TWO OF SNOW MON NIGHT. FWC MOS HINTING THAT SOME OF THIS PRECIP MIGHT BE FRZG...AND 850-700MB CRIT THKNS BECOMES BORDERLINE IN OUR SRN ZONES FOR A TIME MON EVE...ESPCLY ON THE NGM...BUT FOR NOW WILL STICK WITH SNOW. THKNS ADVCTN FIELDS INDICATE WAA SHOULD CONT UNTIL COLD FROPA MON NIGHT...SO WARMING TREND INDICATED BY MOS GUIDANCE ACCEPTED. .DLH...NONE. ERF mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1107 AM EST SUN JAN 21 2001 FCST FOCUSES ON -SHSN AND LES THIS AFTN. WV/IR IMAGERY AND RAOB SHOWING A RATHER FLATTEN RIDGE OVR NRN ROCKIES THIS AM. A NUMBER OF WEAK SHRTWV WERE SLIDING DN THE E SLOPE OF THIS RIDGE...RIGHT THRU FA. THE 1ST IS MOV THRU ERN UP ATTM. THE 2ND IS POISED OVR NW MN. AT THE SFC A RIDGE XTNDS FM ERN DKTS THRU NE MN TO JAMES BAY. LES ENHANCED SYS SN WAS OVR FA. AM RAOBS SHOWING SHALLOW SFC BASED MSTR LYR XTNDG TO H90. RUC PICKED UP ON THIS QUITE WELL. AM RUC/MESOETA SHOWING MEAN SFC-H90 RH AT 80-90 PCT ACRS CWA. WAA MAKING IT QUITE DRY ABV H90 LVL. BY 21Z THIS AFTN XPCT TO SEE WND BACKING W. ETA/RUC SHOWING LLVL CNVRGNC ALONG THE N SHORE OF LAKES SUPERIOR WHICH IS XPCT TO REMAIN THRU MOST OF THIS AFTN. LAKE-H90 DELTA-T'S STILL ADEQUATE FOR LAKE ENHANCEMENT... SO WILL KEEP SOME LES ESPECIALLY OVR THE KEWEENAW PENINSULA AND ALONG THE N SHORE OF ERN CWA. WITH MORE WAA...MLVL WILL CONT TO DRY OUT AND SKYS SHOULD CLR A BIT OVRNGT. WNDS BACKING TO THE W AND SW WILL CUTOFF LES AND ANY LINGERING FLURRIES. GRADIENT WNDS SHOULD CONT TO WEAKEN PROVIDING AN ENVIRONMENT FOR A FAIR AMNT OF RADIATIONAL COOLING. ANOTHER SHRTWV WILL SLIDE ACRS CWA ON MON. H85-H50 Q-VEC CNVRGNC XPCTD TO INCREASE IN ASSOC WITH THIS SHRTWV PASSAGE. MEAN LLVL MSTR WILL PROVIDE RESOURCES FOR INCRS CLDNS ON MON AND MORE SN MON NGT. .MQT...NONE. DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1035 AM EST SUN JAN 21 2001 14Z SURFACE ANALYSIS SHOWED SLOW MOVING TROUGH EXTENDING FROM FAR NORTHERN LAKE HURON...ACROSS THE STRAITS AREA...THEN SW TO NEAR MSN. CONVERGENCE ALONG THIS BOUNDARY...COUPLED WITH LAKE TO 850 MB DELTA T/S NOW APPROACHING 13C...AND MODEST 850/500 MB DPVA ASSOCIATED WITH A WEAK NW FLOW SHORTWAVE HAS CAUSED A BROAD AREA OF LIGHT SNOW SHOWERS TO DEVELOP ACROSS NW LOWER AND EAST UPPER MICHIGAN. RUC AND NEW 12Z ETA SHOW SURFACE BOUNDARY MAKING VERY SLOW PROGRESS SE ACROSS THE FORECAST AREA THIS AFTERNOON...LIKELY DUE TO WEAK UPPER SUPPORT AND WARMING OF BOUNDARY LAYER BY THE LAKES. WEAKENING TROUGH IS STILL FORECAST TO BE IN THE OSC/HTL AREA BY 21Z/00Z. EXPECT SNOW TO BE LIGHT THIS AFTERNOON...GIVEN WEAK (AND RAPIDLY DIMINISHING) SUPPORT FOR LARGE-SCALE ASCENT AND 850/700 MB RH FORECAST TO DROP TO BELOW 60% DURING THE AFTERNOON. LAKE CONTRIBUTIONS WILL ALSO BE LIMITED...GIVEN MARGINAL OVER-WATER INSTABILITY AND INVERSION HEIGHTS FORECAST TO BE AROUND 3000 FT. WILL UPDATE AFTERNOON FORECAST TO REFLECT GENERALLY HIGHER AREAL COVERAGE OF LIGHT SNOW...PER 88D TRENDS. HOWEVER...ADDITIONAL ACCUMULATIONS WILL STILL REMAIN LESS THAN AN INCH. CHANGES TO GOING TEMPERATURE FORECAST WILL BE MINOR. .APX...NONE. SMITH mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 710 AM EST SUN JAN 21 2001 LATEST SURFACE ANALYSIS SHOWS COLD FRONT POISED JUST N/W OF FORECAST AREA...MOVING A BIT SLOWER THAN ANTICIPATED. THIS SLOWER MOVEMENT AND ASSOCIATED DELAYED WIND SHIFT IS CONFIRMED BY LATEST RUC/MESOETA GUIDANCE. THUS...UPDATED ZONES TO ADJUST WIND FORECASTS...TO DELAY WIND SHIFT TO NW UNTIL LATE MORNING/MIDDAY ACROSS NORTHERN LOWER. PER LATEST RADAR TRENDS...LAKE EFFECT IS GETTING UNDERWAY ACROSS NW LOWER. SO FAR...RETURNS ARE VERY WEAK...BUT INTENSITY HAS PICKED UP A BIT UPSTREAM...IN LEE OF LAKE SUPERIOR...PER MQT RADAR...AND SCATTERED LAKE EFFECT SNOW SHOWERS SHOULD DEVELOP ACROSS THE EASTERN UP AND ACROSS N/NW LOWER DURING THE NEXT COUPLE OF HOURS. ALSO... LATEST GUIDANCE SUGGESTS WESTERLY COMPONENT OF 1000-850 MEAN WIND WILL BE MORE SIGNIFICANT THAN SUGGESTED BY 0Z GUIDANCE. GIVEN THIS SCENARIO...A FEW LIGHT SNOW SHOWERS WILL LIKELY PUSH INTO NE LOWER (APN GROUP)...ESPECIALLY ALONG THE COAST...SO ADDED MENTION OF SCATTERED LIGHT SNOW SHOWERS THERE. FINALLY...DROPPED MENTION OF "BECOMING" FROM SKY COVER FORECAST ACROSS THE SE...CLOUDS HAVE SPREAD INTO HTL AND WILL PUSH INTO COASTAL SE COUNTIES SHORTLY. .APX...NONE. ROWLEY mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON MS 1020 AM CST SUN JAN 21 2001 CLOSED UPPER LOW IN NERN TX MOVG ESE THIS MORNING AND LOOKS ON TRACK TO CROSS CENTRAL MS DURING THIS EVENING. A FEW REPORTS OF LIGHT FLURRIES AND OR SPRINKLES HAVE BEEN RECEIVED FROM VICKSBURG TO MADISON HOWEVER CEILINGS ON VAD WIND PROFILES HOLDING AT 7-9K FT. WILL UPDATE ZONES TO ADJUST WORDING AND TIMING OF PRECIP. TEMPS WILL ALSO BE KNOCKED BACK A LITTLE DUE TO THICK CLOUD COVER. NET ISENTROPIC LIFT OF 4-5UB/S IN THE 295-315K LAYER FORECAST TO CONTINUE UNTIL 06Z WITH CONDENSATION PRESSURE DEFICITS OF 25-35MB. 1000-500MB MEAN RELATIVE HUMIDITIES ON MESOETA/RUC CURRENTLY AROUND 20% EXPECTED TO REACH ONLY 30-40% ALONG THE TRACK OF THE MID LEVEL LOW SO WILL KEEP MENTION OF SPRINKLES/FLURRIES DUE TO HIGH BASE CLOUD LAYER AND LACK OF LOWER LEVEL MOISTURE. .PRELIM NUMBERS... JAN 41/27/50/25 0-00 MEI 42/25/52/22 0-00 .JAN... MS...NONE. LA...NONE. AR...NONE. ms AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 952 AM EST SUN JAN 21 2001 SOME CLOUDS LINGER THIS MORNING...BUT LOW LEVEL MOISTURE IS CERTAINLY SHALLOW. GENERALLY ALL AREAS ARE SEEING SOME SUNSHINE AT THIS TIME ...SO I WILL PROBABLY UPDATE TO PARTLY SUNNY ACROSS THE BOARD. THE UPPER LOW OVER OK/NE TX MAY DIG A LITTLE MORE SE...THEN START AN EASTWARD PUSH ACROSS PARTS OF THE GULF COAST STATES. LATEST RUC SUGGESTS SOME HIGH CLOUDS FROM THIS SYSTEM MAY REACH SE TN BY 21Z. AMOUNT OF HIGH CLOUDS TONIGHT WILL BE CRITICAL TO MIN TEMP FORECAST. OTHERWISE...FOR HIGHS THIS AFTERNOON...THE 850 MB THERMAL TROF IS SHOWN TO BE EXITING NE TN/SWRN VA WITH SOME WEAK WARM AIR ADVECTION RETURNING. SNOW COVER IS PROBABLY SPORADIC AND SHOULD NOT HINDER RISE OF TEMPS...AND CURRENT TEMPS WERE RUNNING QUITE CLOSE TO MOS EXCEPT FOR TRI. WILL UPDATE SHORTLY AND REMOVE ANY MORNING WORDING. .MRX... NC...NONE. TN...NONE. VA...NONE. TG tn DEEP SOUTH TEXAS FORECAST DISCUSSION NATIONAL WEATHER SERVICE BROWNSVILLE TX 945 AM CST SUN JAN 21 2001 SHORT RANGE...MESO-ETA AND RUC GUIDANCE SHOW THE 5H CLOSED LOW OVER E TX PROGRESSING EAST STEADILY THROUGHOUT THE DAY WHICH WILL ALLOW THE ASSOCIATED SURFACE TROUGH TO WEAKEN AND SHIFT OFFSHORE. THIS WILL IN TURN ALLOW A DRIER NW SURFACE FLOW TO PREVAIL OVER THE CWA TODAY. SURFACE OBS REFLECT THIS WILL ALL STATIONS AROUND THE AREA SHOWING A N-NW FLOW FROM 5 TO 10 KTS. VSBL SATL IMAGERY SHOWS A COMBINATION OF CLD FEATURES OVER THE AREA WITH THIN MID LEVEL CLDS ADVECTING IN ALOFT WITH WIDESPREAD LOW LEVEL CLD COVER PREVAILING JUST ALONG THE COASTLINE AND OFFSHORE. THE OFFSHORE CLDS WILL PERSIST OFFSHOREDUE TO THE PRESENCE OF WEAK SURFACE TROUGHING...WHILE THE DRIER AIR ADVECTING IN FROM THE NW SHOULD STEADILY ERODE THE INLAND CLD COVER. WILL AMEND THE ZFP TOWARDS MIDDAY TO ADJUST WORDING A BIT...BUT WILL NOT MAKE ANY MAJOR CHANGES ATTM. MARINE...BUOY020 REPORTS A SE FLOW FROM 5 TO 10 KTS WITH SWELLS NEAR 2 FT. THIS WILL CONTINUE THROUGH THE DAY UNTIL THE WIND SHIFT LINE WORKS ITS WAY OFFSHORE. THE NW SURFACE FLOW IN THE WAKE OF THE TROUGHLINE WILL NOT BE STRONG ENOUGH TO WARRENT A MENTION OF SCA CONDITIONS...HOWEVER...IT WILL LIKELY RESULT IN AN INCREASE OF SWELLS BY A FOOT OR TWO. ALL IN ALL...CURRENT FORECAST WORDING LOOKS OK. PUBLIC/MESO...60/HMT...MARTINEZ INTERNET ADDRESS...WWW.SRH.NOAA.GOV/BRO .BRO...NONE. tx