Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 05/09/07

AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
901 PM CDT TUE MAY 8 2007 .DISCUSSION FOR EVENING UPDATE... 901 PM CDT MINOR UPDATE TO CURRENT GRIDS/FCST TO RAISE MIN TEMPS A LITTLE AWAY FROM LAKE...LOWER PCPN AMOUNTS AND TWEAK POPS SLIGHTLY. WEAK SFC TROF AND LLVL DEWPT AXIS HAS BEEN FROM ECNTRL/SERN IL INTO NERN IND DURG AFTN/EARLY EVENING HOURS. WEAK S/WV NOTED IN PROFILER DATA MOVG ACROSS THAT AREA HELPED TO INITIATE RW/TRW IN WEAKLY UNSTABLE AND WEAKLY SHEARED ENVIRONMENT...WITH SOME ACTIVITY CLIPPING FAR SOUTHEAST PARTS OF CWA THIS EVENING. FARTHER TO THE NORTHWEST...ACARS SOUNDINGS OUT OF KORD SINCE THIS AFTN HAVE SHOWN PERSISTANT CAP IN IN PLACE WITH +10 C TEMPS 780-750 MB RANGE...WHICH ALONG WITH WEAKER CONVERGENCE AND LOWER SFC DWPTS HAVE INHIBITED CONVECTIVE DEVELOPMENT. 00Z DVN RAOB AND CURRENT KORD ACARS PROFILES INDICATE MID LEVEL TEMPS COOLING SLIGHTLY WITH APPROACH OF UPPER TROUGH OVER MN...RESULTING IN SLIGHTLY STEEPER MID LVL LAPSE RATES. WITH APPROACH OF UPPER TROUGH AND JET MAX PROPAGATING EAST ACROSS IA FCST MODELS CONTINUE TO INDICATE POTENTIAL FOR ELEVATED CONVECTION DEVELOPING OVRNGT. HOWEVER...LOW LEVEL FORCING NOT PARTICULARLY IMPRESSIVE WITH H85 FLOW ONLY 10-15 KTS AT BEST. STILL GIVEN INCREASINGLY FAVORABLE MID LVL FORCING AM HESITANT TO PULL POPS FROM GOING GRIDS/FCST. HAVE HOWEVER TEMPERED QPF AMOUNTS...AND HAVE BACKED OF TO CHC RW/ISOLATED TSRA OVRNGT. RATZER PREVIOUS DISCUSSION 315 PM CDT PRECIP CHANCES MAINLY TONIGHT AND WEDNESDAY WILL CONTINUE TO BE THE MAIN FORECAST CONCERN. WEAK SFC PRESSURE FIELD NOTED IN SUBJECTIVE SFC ANALYSES EARLY THIS AFTERNOON WITH A WEAK SURFACE TROUGH ACROSS FAR NORTHEAST ILLINOIS/NORTHWEST INDIANA. VISIBLE SATELLITE IMAGERY INDICATING ENHANCED CU AND A FEW THUNDERSTORMS DEVELOPING ALONG THIS WEAK BOUNDARY WITH SPC RUC MESOSCALE ANALYSIS GRAPHICS INDICATING 1000-1500 J/KG OF MUCAPE EXTENDING FROM SOUTHERN ILLINOIS THROUGH NORTH CENTRAL INDIANA. ACARS SOUNDINGS INDICATING ISOTHERMAL LAYER IN THE 800-750 HPA LAYER WHICH LIKELY IS PROVIDING SOME WEAK INHIBITION THIS AFTERNOON. DURING THE EARLY EVENING...EXPECTING TEMPS IN THIS LAYER TO COOL AS UPPER LOW ACROSS SOUTHEAST SOUTH DAKOTA AND FAR NORTHWEST IOWA CONTINUES TO TRACK EASTWARD DAMPENING THE MID LEVEL RIDGE IN PLACE ACROSS THE SOUTHERN GREAT LAKES REGION. OUTSIDE OF PEAK DIURNAL HEATING...NOT MUCH UPPER FORCING TO GET THINGS GOING LATE THIS AFTERNOON AND EARLY THIS EVENING...AND BEST CHANCES OF LATE AFTERNOON THUNDER WILL LIKELY REMAIN ACROSS EAST CENTRAL ILLINOIS/NORTH CENTRAL INDIANA. BEST CHANCES OF PRECIP FOR LOT CWA STILL APPEAR TO BE CONFINED TO THE OVERNIGHT PERIOD AND THROUGH THE EARLY MORNING HOURS AS AFOREMENTIONED UPPER LOW APPROACHES THE AREA. AS THIS UPPER LOW APPROACHES MODELS ARE IN GENERAL AGREEMENT IN REFOCUSING SFC LOW A LITTLE FURTHER BACK WEST INTO NORTH CENTRAL ILLINOIS. MAX UPPER FORCING SHOULD OCCUR IN THE 09Z-12Z TIME FRAME...AND NAM/GFS CONTINUE TO INDICATE WEAK LOW LEVEL MOISTURE CONVERGENCE ACROSS MAINLY SOUTHEAST HALF OF THE FORECAST AREA LATE TONIGHT WITH ELEVATED INSTABILITY ON THE ORDER OF 500-1000 J/KG. SREF ENSEMBLE POPS EVEN APPROACHING THE LIKELY CATEGORY ACROSS NORTHWEST INDIANA OVERNIGHT...BUT FOR NOW HAVE OPTED TO GO WITH HIGH CHANCE POPS GIVEN REMAINING UNCERTAINTY AS TO TIMING BEST UPPER FORCING. FOR WEDNESDAY...WILL KEEP THESE HIGH CHANCE POPS ACROSS EASTERN PORTIONS OF THE CWA DURING THE MORNING...WITH LOWER CHANCE POPS IN THE AFTERNOON AS THE UPPER WAVE BEGINS TO EXIT THE AREA. SOME CONCERN IN THE AFTERNOON FOR A FEW SHOWERS DEVELOPING ALONG THE LAKE BREEZE BOUNDARY...BUT BY MID AFTERNOON THE BULK OF THE PRECIPITATION SHOULD BE SHIFTING EAST OF THE AREA. DID NUDGE UP HIGH TEMPS A BIT FOR WED BASED ON LOW LEVEL THERMAL PROGS FROM THE 12Z MODEL RUNS...WITH HIGHS NEAR 80 MOST LOCATIONS...BUT COOLER CLOSER TO LAKE MICHIGAN ACROSS NORTHEAST ILLINOIS/NORTHWEST INDIANA AS WINDS BECOMING NORTHERLY IN THE WAKE OF WEAK SURFACE WAVE TRACKING EAST OF THE AREA. WEAK MID/UPPER RIDGING BUILDS INTO NORTHERN ILLINOIS/NORTHWEST INDIANA TOMORROW NIGHT WITH DRY CONDITIONS EXPECTED ACROSS MOST OF THE AREA. ON THURSDAY HAVE INCLUDED LOW POP MENTION FOR TSRA ACROSS FAR SOUTHERN PORTIONS OF CWA AS WEAK SHORT WAVES EJECTING EASTWARD FROM CUT-OFF SOUTHERN STREAM LOW APPROACH THE REGION. ATTENTION WILL THEN TURN TO TIMING FROPA IN ASSOCIATION WITH FAST MOVING NORTHERN STREAM SHORT WAVE MOVING ACROSS SOUTHERN CANADA. LATEST GFS HAS COME IN A BIT FASTER WITH THIS TROUGH PASSAGE ON FRIDAY. DID COOL TEMPS A BIT ON SATURDAY GIVEN 1025 HPA SFC ANTICYCLONE TRACKING THROUGH THE NORTHERN LAKES WITH NORTHEAST FLOW ACROSS THE AREA. VERY FEW CHANGES WERE NEEDED FOR THE EXTENDED PART OF THE FORECAST. FOCUS WILL CONTINUE TO BE ON MORE ACTIVE NORTHERN STREAM AND POSSIBILITY OF NEXT FRONTAL PASSAGE LATE MONDAY. MAINTAINED CHANCE OF THUNDER ON MONDAY WITH MILD TEMPS CONTINUING IN ADVANCE OF THE FRONT. MARSILI && .AVIATION DISCUSSION REGARDING 00Z TAFS... 630 PM CDT A FEW DIFFERENT CONCERNS FOR THE OVERNIGHT HOURS. THE LAKE BREEZE FORMED THIS AFTERNOON AND CAN STILL BE SEEN IN THE RADAR IMAGERY. THE LAKE BREEZE BNDRY HAS PUSHED INLAND OF ORD/MDW/GYY/DPA. WITH THE SETTING SUN...THE THERMAL DIFFERENCES DRIVING THE BNDRY WILL WEAKEN AND WINDS WILL RAPIDLY RETURN TO REFLECT THE LARGE SCALE FLOW. THE PRESSURE GRADIENT OVER THE REGION IS VERY WEAK AND WINDS OVERNIGHT WILL GO LIGHT AND VARIABLE. THIS LEADS TO THE SECOND CONCERN...VISIBILITY. WITH DEWPOINTS INCREASING INTO THE UPPER 50S...THERE IS ADEQUATE LOW LEVEL MOISTURE TO BE CONCERNED ABOUT VISIBILITY. HAVE ADJUSTED THE LATEST TAFS TO LOWER VISIBILITY LOWER THAN THE PREVIOUS FORECAST. LAST NIGHT...SOME SITES DROPPED TO IFR. NOT READY TO DROP VIS THAT LOW FOR ALL SITES TONIGHT SINCE THERE WILL BE SOME LINGERING INFLUENCE OF THE LAKE BREEZE CIRCULATION...BUT DPA AND RFD HAVE THE BEST CHANCE...SO HAVE LOWERED THEM TO 2SM AND WILL GO WITH 4SM AT ORD/MDW. THUNDER POTENTIAL STILL QUESTIONABLE. WILL KEEP THE VCTS...BUT HAVE PUSHED BACK THE VCTS AT ORD/MDW/GYY DUE TO THE STABILIZING OF THE SFC LAYER FOLLOWING THE LAKE BREEZE PASSAGE. THE UPPER LOW IS MOVING OVER NRN IOWA THIS EVENING AND WILL CONTINUE TO TRACK EWD. THIS MAY PROVIDE ENOUGH UPPER LEVEL FORCING TO INITIATE SOME CNVTV ACTIVITY...BUT FEEL THAT SINCE THE TIMING OF THE BEST UPPER FORCING WILL BE DURG THE PREDAWN HOURS WITH NO THERMAL FORCING...TS CHANCES WILL BE SMALL. MAIN CONCERN FOR THE LATTER PORTION OF THE 00Z TAFS WILL BE WIND DIRECTION. LOOKS LIKE LAKE BREEZE DEVELOPMENT WILL BE POSSIBLE AGAIN TOMORROW. SO HAVE INTRODUCED A SHARP WIND SHIFT TO THE ORD/MDW/GYY TAFS. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LK...NONE. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
630 PM CDT TUE MAY 8 2007 .DISCUSSION FOR AFTERNOON GRIDS/ZONES... 315 PM CDT PRECIP CHANCES MAINLY TONIGHT AND WEDNESDAY WILL CONTINUE TO BE THE MAIN FORECAST CONCERN. WEAK SFC PRESSURE FIELD NOTED IN SUBJECTIVE SFC ANALYSES EARLY THIS AFTERNOON WITH A WEAK SURFACE TROUGH ACROSS FAR NORTHEAST ILLINOIS/NORTHWEST INDIANA. VISIBLE SATELLITE IMAGERY INDICATING ENHANCED CU AND A FEW THUNDERSTORMS DEVELOPING ALONG THIS WEAK BOUNDARY WITH SPC RUC MESOSCALE ANALYSIS GRAPHICS INDICATING 1000-1500 J/KG OF MUCAPE EXTENDING FROM SOUTHERN ILLINOIS THROUGH NORTH CENTRAL INDIANA. ACARS SOUNDINGS INDICATING ISOTHERMAL LAYER IN THE 800-750 HPA LAYER WHICH LIKELY IS PROVIDING SOME WEAK INHIBITION THIS AFTERNOON. DURING THE EARLY EVENING...EXPECTING TEMPS IN THIS LAYER TO COOL AS UPPER LOW ACROSS SOUTHEAST SOUTH DAKOTA AND FAR NORTHWEST IOWA CONTINUES TO TRACK EASTWARD DAMPENING THE MID LEVEL RIDGE IN PLACE ACROSS THE SOUTHERN GREAT LAKES REGION. OUTSIDE OF PEAK DIURNAL HEATING...NOT MUCH UPPER FORCING TO GET THINGS GOING LATE THIS AFTERNOON AND EARLY THIS EVENING...AND BEST CHANCES OF LATE AFTERNOON THUNDER WILL LIKELY REMAIN ACROSS EAST CENTRAL ILLINOIS/NORTH CENTRAL INDIANA. BEST CHANCES OF PRECIP FOR LOT CWA STILL APPEAR TO BE CONFINED TO THE OVERNIGHT PERIOD AND THROUGH THE EARLY MORNING HOURS AS AFOREMENTIONED UPPER LOW APPROACHES THE AREA. AS THIS UPPER LOW APPROACHES MODELS ARE IN GENERAL AGREEMENT IN REFOCUSING SFC LOW A LITTLE FURTHER BACK WEST INTO NORTH CENTRAL ILLINOIS. MAX UPPER FORCING SHOULD OCCUR IN THE 09Z-12Z TIME FRAME...AND NAM/GFS CONTINUE TO INDICATE WEAK LOW LEVEL MOISTURE CONVERGENCE ACROSS MAINLY SOUTHEAST HALF OF THE FORECAST AREA LATE TONIGHT WITH ELEVATED INSTABILITY ON THE ORDER OF 500-1000 J/KG. SREF ENSEMBLE POPS EVEN APPROACHING THE LIKELY CATEGORY ACROSS NORTHWEST INDIANA OVERNIGHT...BUT FOR NOW HAVE OPTED TO GO WITH HIGH CHANCE POPS GIVEN REMAINING UNCERTAINTY AS TO TIMING BEST UPPER FORCING. FOR WEDNESDAY...WILL KEEP THESE HIGH CHANCE POPS ACROSS EASTERN PORTIONS OF THE CWA DURING THE MORNING...WITH LOWER CHANCE POPS IN THE AFTERNOON AS THE UPPER WAVE BEGINS TO EXIT THE AREA. SOME CONCERN IN THE AFTERNOON FOR A FEW SHOWERS DEVELOPING ALONG THE LAKE BREEZE BOUNDARY...BUT BY MID AFTERNOON THE BULK OF THE PRECIPITATION SHOULD BE SHIFTING EAST OF THE AREA. DID NUDGE UP HIGH TEMPS A BIT FOR WED BASED ON LOW LEVEL THERMAL PROGS FROM THE 12Z MODEL RUNS...WITH HIGHS NEAR 80 MOST LOCATIONS...BUT COOLER CLOSER TO LAKE MICHIGAN ACROSS NORTHEAST ILLINOIS/NORTHWEST INDIANA AS WINDS BECOMING NORTHERLY IN THE WAKE OF WEAK SURFACE WAVE TRACKING EAST OF THE AREA. WEAK MID/UPPER RIDGING BUILDS INTO NORTHERN ILLINOIS/NORTHWEST INDIANA TOMORROW NIGHT WITH DRY CONDITIONS EXPECTED ACROSS MOST OF THE AREA. ON THURSDAY HAVE INCLUDED LOW POP MENTION FOR TSRA ACROSS FAR SOUTHERN PORTIONS OF CWA AS WEAK SHORT WAVES EJECTING EASTWARD FROM CUT-OFF SOUTHERN STREAM LOW APPROACH THE REGION. ATTENTION WILL THEN TURN TO TIMING FROPA IN ASSOCIATION WITH FAST MOVING NORTHERN STREAM SHORT WAVE MOVING ACROSS SOUTHERN CANADA. LATEST GFS HAS COME IN A BIT FASTER WITH THIS TROUGH PASSAGE ON FRIDAY. DID COOL TEMPS A BIT ON SATURDAY GIVEN 1025 HPA SFC ANTICYCLONE TRACKING THROUGH THE NORTHERN LAKES WITH NORTHEAST FLOW ACROSS THE AREA. VERY FEW CHANGES WERE NEEDED FOR THE EXTENDED PART OF THE FORECAST. FOCUS WILL CONTINUE TO BE ON MORE ACTIVE NORTHERN STREAM AND POSSIBILITY OF NEXT FRONTAL PASSAGE LATE MONDAY. MAINTAINED CHANCE OF THUNDER ON MONDAY WITH MILD TEMPS CONTINUING IN ADVANCE OF THE FRONT. MARSILI && .AVIATION DISCUSSION REGARDING 00Z TAFS... 630 PM CDT A FEW DIFFERENT CONCERNS FOR THE OVERNIGHT HOURS. THE LAKE BREEZE FORMED THIS AFTERNOON AND CAN STILL BE SEEN IN THE RADAR IMAGERY. THE LAKE BREEZE BNDRY HAS PUSHED INLAND OF ORD/MDW/GYY/DPA. WITH THE SETTING SUN...THE THERMAL DIFFERENCES DRIVING THE BNDRY WILL WEAKEN AND WINDS WILL RAPIDLY RETURN TO REFLECT THE LARGE SCALE FLOW. THE PRESSURE GRADIENT OVER THE REGION IS VERY WEAK AND WINDS OVERNIGHT WILL GO LIGHT AND VARIABLE. THIS LEADS TO THE SECOND CONCERN...VISIBILITY. WITH DEWPOINTS INCREASING INTO THE UPPER 50S...THERE IS ADEQUATE LOW LEVEL MOISTURE TO BE CONCERNED ABOUT VISIBILITY. HAVE ADJUSTED THE LATEST TAFS TO LOWER VISIBILITY LOWER THAN THE PREVIOUS FORECAST. LAST NIGHT...SOME SITES DROPPED TO IFR. NOT READY TO DROP VIS THAT LOW FOR ALL SITES TONIGHT SINCE THERE WILL BE SOME LINGERING INFLUENCE OF THE LAKE BREEZE CIRCULATION...BUT DPA AND RFD HAVE THE BEST CHANCE...SO HAVE LOWERED THEM TO 2SM AND WILL GO WITH 4SM AT ORD/MDW. THUNDER POTENTIAL STILL QUESTIONABLE. WILL KEEP THE VCTS...BUT HAVE PUSHED BACK THE VCTS AT ORD/MDW/GYY DUE TO THE STABILIZING OF THE SFC LAYER FOLLOWING THE LAKE BREEZE PASSAGE. THE UPPER LOW IS MOVING OVER NRN IOWA THIS EVENING AND WILL CONTINUE TO TRACK EWD. THIS MAY PROVIDE ENOUGH UPPER LEVEL FORCING TO INITIATE SOME CNVTV ACTIVITY...BUT FEEL THAT SINCE THE TIMING OF THE BEST UPPER FORCING WILL BE DURG THE PREDAWN HOURS WITH NO THERMAL FORCING...TS CHANCES WILL BE SMALL. MAIN CONCERN FOR THE LATTER PORTION OF THE 00Z TAFS WILL BE WIND DIRECTION. LOOKS LIKE LAKE BREEZE DEVELOPMENT WILL BE POSSIBLE AGAIN TOMORROW. SO HAVE INTRODUCED A SHARP WIND SHIFT TO THE ORD/MDW/GYY TAFS. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LK...NONE. && $$
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
1054 AM EDT MON MAY 7 2007 .SHORT TERM... WELL...HIGH PRESSURE IS ENSCONCED OVER THE AREA. THE HIGH IS BLOCKING ALL OF THE CENTRAL PLAINS SEVERE WEATHER WITH A CLASSIC OMEGA BLOCK IN THE UPPER LEVELS THE ILN 12Z SOUNDING IS SIMPLY PARCHED...WITH A PALTRY 0.09 PRECIPITABLE WATER. ISODROSOTHERM ANALYSIS HAVE UPPER 20S ACROSS FAR WRN JKL CWA...WITH NEAR 50 ACROSS HANCOCK AND OHIO COUNTIES BORDER PAH CWA. IN THE LAST HOUR A THIN BAND OF STRATOCUMULUS HAS DEVELOPED BETWEEN FLOYD CO IN THRU JEFFERSON CO KY AND DOWN TO GREEN COUNTY. THIS SHOWS UP WELL ON THE BNA 12Z SOUNDING BUT IS FOCUSED ALONG A THIN LINE. WILL MONITOR AND TAKE A LOOK AT THE LATEST ACARS SOUNDING AND RUC TO SEE WHAT TO DO WITH THE SKY GRIDS. JDG && .PREV DISCUSSION...ISSUED 630 AM EDT MON MAY 7 2007/ SHORT TERM (TODAY THROUGH TUESDAY)... UPPER AIR PATTERN SHOWS A CLASSIC OMEGA BLOCK ACROSS THE CONUS. A STRONG AND AMPLIFIED RIDGE WILL REMAIN IN PLACE ACROSS THE WESTERN GREAT LAKES...EXTENDING THROUGH THE LOWER MISSISSIPPI VALLEY. DEEP TROUGHING WILL WEAKEN...BUT REMAIN IN PLACE ACROSS THE SOUTHERN ROCKIES. A PREVIOUS TROUGH OFF THE EAST COAST IS NOW IN THE PROCESS OF FORMING AN UNSEASONABLY FAR SOUTH AND DEEP CUTOFF LOW OFF THE NORTH CAROLINA COAST. BY EARLY TUESDAY THIS CUTOFF LOW WILL RETROGRADE SOUTH AND WEST AND LIE OFF THE NORTHEASTERN FLORIDA COAST. RIDGING BOTH AT THE SURFACE AND ALOFT WILL LIE NORTH AND WEST OF THIS CUTOFF FEATURE AND EXTEND FROM THE WESTERN GULF STATES ALONG AN ARC ACROSS THE LOWER OHIO VALLEY INTO NEW ENGLAND. HIGH PRESSURE CENTERED OVER NEW ENGLAND HAS BROUGHT EASTERLY WINDS AND EXCEPTIONALLY DRY AIR TO THE ENTIRE CWA. CURRENT DEWPOINTS ARE ONLY IN THE LOWER 30S ACROSS CENTRAL KENTUCKY. THESE LOW DEWPOINTS ARE DUE IN PART TO DOWNSLOPING ACROSS THE APPALACHIANS. WITH THIS BLOCKING IN PLACE...EXPECT A COMPLETE ABSENCE OF LOW CLOUDS...LOW AFTERNOON RELATIVE HUMIDITIES...WARM AFTERNOONS AND COOL NIGHTS THROUGH AT LEAST TUESDAY. THICK CIRRUS PRESENT LAST EVENING...DUE IN PART TO CONVECTIVE BLOWOFF FROM STORMS ACROSS THE PLAINS...HAS SHOWN A TENDENCY TO ERODE...AND SO TODAY MAY STILL TURN OUT TO BE MOSTLY SUNNY...ESPECIALLY ACROSS OUR EASTERN COUNTIES. AFTERNOON HIGH TEMPERATURES WILL RISE A FEW DEGREES EACH DAY AS A DRY AIRMASS WILL MODIFY UNDER LATE SPRING SUNSHINE. EXTENDED(WEDNESDAY THROUGH SUNDAY)... OMEGA BLOCK WILL CONTINUE THROUGH THURSDAY...ALTHOUGH BOTH THE SOUTHEASTERN CUTOFF LOW AND THE TROUGH ACROSS THE ROCKIES WILL WEAKEN DAY BY DAY. BOTH OF THESE FEATURES WILL BE LEFT BEHIND AS THE JET STREAM WILL RETREAT NORTHWARD TOWARDS A TYPICAL EARLY SUMMER PATTERN ALONG THE US-CANADIAN BORDER. THE CUTOFF LOW MAY MOVE AS FAR WEST AS THE FLORIDA PENINSULA LATE WEDNESDAY BEFORE DRIFTING BACK TOWARDS THE NORTHEAST. AS THE TROUGH ACROSS THE ROCKIES WEAKENS...A SERIES OF WEAK DISTURBANCES WILL EJECT ACROSS THE UPPER MISSISSIPPI VALLEY WEDNESDAY AND THURSDAY. FORECAST RELATIVE HUMIDITIES SHOWS DEEP LAYER MOISTURE SLOWLY ENCROACHING UPON THE LOWER OHIO VALLEY THURSDAY AND FRIDAY...AS A SHALLOW TROUGH MOVES ACROSS THE GREAT LAKES. THE GFS FORECASTS A WEAK BOUNDARY THAT WILL TRY TO MOVE SOUTH OF THE OHIO RIVER ON THURSDAY. WILL NOT MAKE MUCH CHANGES TO ONGOING FORECAST OF A CHANCE OF CONVECTION THURSDAY THROUGH SUNDAY. TEMPERATURES WILL BE WARM WEDNESDAY THROUGH SATURDAY...WITH THE MAIN JET ALONG THE CANADIAN BORDER...MORE TYPICAL OF EARLY JUNE...TEMPERATURES WILL REFLECT THIS. .AVIATION (FOR 12Z TAFS)... EXPANSIVE HIGH PRESSURE ACROSS WESTERN NEW ENGLAND WILL BRING VERY DRY CONTINENTAL AIR ACROSS ENTIRE FORECAST AREA THROUGH TUESDAY. NO CLOUDS EXPECTED THROUGH EARLY TOMORROW MORNING EXCEPT FOR THIN HIGH CIRRUS. EAST SURFACE WINDS OF 5 TO 10 MPH WILL VEER TO THE SOUTHEAST THIS AFTERNOON AND INCREASE TO 10 TO 15 MPH. AFTER 03Z...SURFACE WINDS WILL BECOME QUITE LIGHT. EXPECT VFR FLIGHT CONDITIONS FOR THE NEXT 24 HOURS WITH NEARLY UNLIMITED VISIBILITIES. JSD && .LMK WATCHES/WARNINGS/ADVISORIES... KY...NONE. IN...NONE. && $$
AREA FORECAST DISCUSSION
NWS GAYLORD MI
351 PM EDT MON MAY 7 2007 .DISCUSSION...MID AFTERNOON SATELLITE/RUC/RADAR/SURFACE/AND UPPER AIR ANALYSIS SHOWS NORTHERN MICHIGAN STILL LYING UNDER IMPRESSIVE MID AND UPPER LEVEL RIDGE AXIS THAT EXTENDS FROM THE LOWER MISSISSIPPI VALLEY UP INTO SOUTHEAST ONTARIO. LOW LEVEL DRY SOUTHERLY FLOW ALSO CONTINUES AROUND EAST COAST HIGH...WITH DEWPOINTS REMAINING IN THE 20S TO NEAR 30. THIS...COMBINED WITH TEMPERATURES WARMING INTO THE 70S...RESULTING IN RH PERCENTAGES DROPPING INTO THE TEENS OVER MUCH OF NORTHERN LOWER MICHIGAN. FARTHER WEST...WESTERN ONTARIO SHORTWAVE STEADILY ADVANCING EAST...WITH ASSOCIATED COOL FRONT EXTENDING FROM CENTRAL MINNESOTA DOWN THROUGH THE CENTRAL PLAINS. SHOWER DEVELOPMENT BACK ACROSS THE WESTERN LAKES CONTINUES TO STRUGGLE AS THEY PUSH INTO THE RIDGE AXIS AND WITH BEST MOISTURE TRANSPORT CONFINED TO ONGOING OKLAHOMA MCS. PRIMARY CONCERNS FOR THE NEXT 24 HOURS CENTER ON THIS EVENINGS ELEVATED FIRE WEATHER RISK WITH ATTENTION THEN FOCUSING ON PRECIPITATION POTENTIAL WITH APPROACH OF UPSTREAM COOL FRONT AND SHORTWAVE. TONIGHT...FIRST OF ALL...EXPECT STEADILY IMPROVING FIRE WEATHER CONDITIONS LATER THIS EVENING AS TEMPERATURES DROP BACK INTO THE 60S AND DEWPOINTS SLOWLY INCREASE AS SOME LOW LEVEL MOISTURE WORKS EAST INTO THE AREA. THEREFORE...WILL ALLOW RED FLAG WARNING TO EXPIRE AT 01Z. OTHERWISE...AFOREMENTIONED SHORTWAVE CONTINUES EAST ACROSS ONTARIO...IN THE PROCESS FLATTENING NORTHERN PORTION OF GREAT LAKES RIDGING. ASSOCIATED SURFACE COOL FRONT PUSHES EAST...EXTENDING FROM EASTERN UPPER MICHIGAN THROUGH CENTRAL LAKE MICHIGAN BY MORNING. MUCH LIKE PREVIOUS FORECASTS...NOT OVERLY IMPRESSED WITH PRECIPITATION CHANCES WITH STEADILY DECAYING SURFACE CONVERGENCE ALONG FRONTAL ZONE AND BETTER MID AND UPPER LEVEL DYNAMICS PASSING WELL NORTH. IN ADDITION...THESE WEAK DYNAMICS HAVE TO WORK OVER AN EXCEEDINGLY DRY AIRMASS THAT REMAINS IN PLACE...AS EVIDENT BY RAPID EVAPORATION OF ANY SHOWER ACTIVITY THIS AFTERNOON AS THEY APPROACHED THE WESTERN LAKES REGION AND A MID MORNING ACARS SOUNDING FROM PELLSTON SHOWING BONE DRY CONDITIONS BELOW 600MB AND A DEWPOINT DEPRESSION AT 775MB OF 50C (BASED OFF EXTRAPOLATION OF SOUNDING...EVEN LARGER DEWPOINTS EXISTED AT AROUND 800MB). HOWEVER...WITH SOME UPPER LEVEL SUPPORT IN RIGHT ENTRANCE REGION OF JET CUTTING ACROSS LAKE SUPERIOR AND EXPECTED NARROW TONGUE OF LOW AND MID LEVEL MOISTURE DIRECTLY ALONG AND JUST AHEAD OF FRONT...FELT CHANCE POPS JUSTIFIED...SPREADING FROM NORTHWEST TO SOUTHEAST DURING THE NIGHT. DID REMOVE ANY MENTION OF THUNDER WITH LOSS OF ANY SURFACED BASED INSTABILITY OVERNIGHT AND WITH MID LEVEL LAPSE RATES REMAINING AT 5.5 C/KM OR LOWER. TEMPERATURES WILL BE UNSEASONABLE MILD OVERNIGHT WITH A STEADY SOUTH FLOW PRESENT...WITH READINGS BY MORNING ONLY DROPPING TO NEAR 50 TO THE MID 50S. TUESDAY...MODELS CONTINUE TO STRUGGLE WITH TIMING OF FRONTAL PASSAGE TOMORROW...WITH GFS REMAINING SEVERAL HOURS FASTER...CLEARING NORTHERN MICHIGAN BY AFTERNOON. ON THE OTHER SIDE OF THE SPECTRUM IS THE NAM-WRF...ALLOWING THE FRONT TO BASICALLY WASH OUT IN RESPONSE TO LOW PRESSURE IT DEVELOPS OVER NORTHERN WISCONSIN AHEAD OF NORTHERN PLAINS SHORTWAVE. BOTH MODELS REMAIN RATHER CONSISTENT WITH THEIR PREVIOUS ITERATIONS. THEREFORE...FELT BEST COURSE OF ACTION WAS TO LEAVE PREEXISTING CHANCE POPS ALONE...ESPECIALLY WITH SOME UPPER LEVEL DIVERGENCE STILL PRESENT AND MID LEVEL VORT LOBE CUTTING THROUGH THE NORTHERN LAKES. HAVE THUNDER ONLY FOR FAR SOUTHERN ZONES DURING THE AFTERNOON WITH DEVELOPMENT OF SOME SURFACE BASED CAPE. WILL...HOWEVER...IGNORE OVER ZEALOUS NAM-WRF DEPICTION OF CAPES APPROACHING 1000 J/KG...A PRODUCT OF MODEL PROJECTED DEWPOINTS PUSHING NEAR 60 DEGREES. THIS SEEMS EXCESSIVELY HIGH BASED OFF VERY DRY CONDITIONS OF LATE AND WEAKNESS OF SYSTEM. ALTERING FOR A MORE REASONABLE DEWPOINT NEAR 50 PRODUCES CAPE ONLY APPROACHING AROUND 50 J/KG OR SO. IT WILL REMAIN MILD WITH READINGS BACK INTO THE LOW TO MID 70S. MSB TUESDAY NIGHT THROUGH WEDNESDAY...GLARING DIFFERENCES BETWEEN THE NAM/GFS REGARDING STRENGTH/DISPOSITION AND PLACEMENT OF SHORT WAVE NOW LIFTING INTO THE NRN PLAINS THIS AFTERNOON. NAM REMAINS MOST AGGRESSIVE RUNNING A NEARLY CLOSED OFF MID LEVEL WAVE INTO THE UPPER MIDWEST TUESDAY NIGHT...AND ACROSS NRN MICHIGAN ON WEDNESDAY. GFS40/UKMET SHEAR OUT AND WEAKEN THIS WAVE LONG BEFORE REACHING THE STATE WHILE THE ECMWF IS SOMEWHERE IN BETWEEN. BOTH THE NAM AND GFS LOOK WAY OVERDONE WITH MODEL (NOT MOS GUIDANCE) SFC DEWPOINTS... KICKING VALUES UP INTO THE 60S ACROSS NRN LOWER MICHIGAN AS EARLY AS TUESDAY AND HOLDING THEM THERE THROUGH MUCH OF THE WEEK. THERE ARE HIGHER (50S) DEWPOINTS UPSTREAM IN MN/WESTERN TODAY WHICH WILL WORK INTO THE REGION EVENTUALLY BUT A FAR CRY FROM THE 60S DEPICTED IN THE MODELS. THIS IN TURN THEN HAS BIG IMPACT ON MODEL COMPUTED INSTABILITY AND THE MODEL CONVECTIVE PRECIP SCHEMES TURNING ON. THE NAM DEPICTION OF A 2 INCH (CONVECTIVELY INDUCED) QPF BULLSEYE RUNNING UP THROUGH NRN LOWER MICHIGAN TUESDAY NIGHT INTO WEDNESDAY AS THE MID LEVEL WAVE COMES THROUGH IS NOT BELIEVABLE. GFS IDEA LOOKS MORE REASONABLE WITH CONVECTION DEVELOPING FURTHER SOUTH WHERE JUICIER AIR WILL LIKELY RESIDE. WILL KEEP A LOW CHANCE FOR SHOWERS GOING TUESDAY NIGHT THROUGH WEDNESDAY FOR ANY PRECIP THAT MIGHT DEVELOP AND WORK INTO THE REGION AS WELL AS ANYTHING THAT MIGHT DEVELOP WITHIN THE HIGHER THETA-E AIRMASS DRAPED ACROSS NRN MICHIGAN. BUT THUNDER POSSIBILITIES LOOK EVEN SLIMMER AND HAVE REMOVED THUNDER FROM THE FORECAST FOR THESE PERIODS. THURSDAY THROUGH MONDAY (EXTENDED PERIODS)...SHARP BLOCKING RIDGE PATTERN NOW DOMINANT ACROSS THE EASTERN CONUS FORECAST TO BREAK DOWN FROM MID WEEK ONWARD...IN FAVOR OF A STRONGER MORE PROGRESSIVE NORTHERN STREAM ACROSS CANADA WHILE SOUTHERN STREAM BECOMES RATHER INACTIVE. THIS TRANSLATES INTO SUBTLE OVERALL COOLING TREND (BACK TO AROUND CLIMO) FOR NORTHERN MICHIGAN AND THE WESTERN GREAT LAKES... PARTICULARLY LATE IN THE FORECAST PERIOD AS LOW AMPLITUDE LONG WAVE TROUGHING DEVELOPS OVER EASTERN CANADA/NE U.S. AS FAR AS SENSIBLE WEATHER IS CONCERNED...NOT A LOT IN THE RAIN DEPARTMENT FOR NRN MICHIGAN DURING THIS PERIOD...WITH A COUPLE WEAKISH COLD FRONTS (ASSOCIATED WITH NRN STREAM SYSTEMS) PASSING THROUGH THE REGION. FIRST NRN STREAM SYSTEM FORECAST TO PASS ACROSS ONTARIO THURSDAY WITH A TRAILING WEAK FRONT DROPPING DOWN INTO NRN MICHIGAN LATE THURSDAY INTO FRIDAY. NOT MUCH IN THE WAY OF MOISTURE RETURN INTO NRN MICHIGAN AHEAD OF THE FRONT AND AS MENTIONED ABOVE MODEL DEWPOINT FORECASTS PUSHING THE 60S BOTH THURSDAY AND FRIDAY - AND SUBSEQUENT IMPACT ON MODEL INSTABILITY AND CONVECTIVE PRECIP DEVELOPING ACROSS NRN LOWER MICHIGAN BOTH DAYS - LOOKS FAIRLY UNREALISTIC FOR THIS TIME OF YEAR. THUS...PLAN IS TO KEEP THE FORECAST DRY BOTH THURSDAY AND FRIDAY AT THIS POINT. SATURDAY THROUGH MONDAY...AFOREMENTIONED LARGE AREA OF HIGH PRESSURE FORECAST TO BUILD OVER EASTERN CANADA/NRN GREAT LAKES FOR THE WEEKEND LOOKING TO CONTINUE THE STRETCH OF RAIN FREE WEEKEND CONDITIONS. MEANWHILE...ALONG WITH THE LARGE HIGH PRESSURE SYSTEM... SLIGHTLY COOLER AIR ALSO LOOKING TO SAG INTO THE REGION LOWERING TEMPS BACK TO AROUND NORMAL READINGS (LOWER TO MIDDLE 60S FOR HIGHS AND LOWS IN THE UPPER 30S TO LOWER 40S). MAY GET ANOTHER CHANCE AT SOME RAIN EARLY NEXT WEEK AS THE HIGH MOVES OFF TO THE EAST AND ANOTHER NRN STREAM LOW AND ASSOCIATED WEAK FRONT MOVES THROUGH ONTARIO AND INTO THE GREAT LAKES ON MONDAY. SIMILAR MOISTURE CONCERNS REMAIN HOWEVER ALTHOUGH SOME MOISTURE ADVECTION INTO THE CENTRAL AND NRN PLAINS MAY LEAD TO UPSTREAM THUNDERSTORM DEVELOPMENT WITH SOME OF THIS SHOWER ACTIVITY EVENTUALLY REACHING THE STATE MONDAY. && .AVIATION...ISSUED AT 145 PM HIGH PRESSURE OVER MICHIGAN SLOWLY GIVING WAY TO APPROACHING COOL FRONT...WHICH IS EXPECTED TO SLOWLY TRAVERSE THE AREA LATER TONIGHT THROUGH TUESDAY. DESPITE BOUNDARY...LIMITED MOISTURE ACROSS NORTHERN MICHIGAN EXPECTED TO KEEP SHOWER COVERAGE LATER TONIGHT AND TUESDAY WIDELY SCATTERED. GIVEN VERY SCATTERED NATURE OF ANTICIPATED ACTIVITY...FELT BEST COURSE OF ACTION AT THIS TIME WAS TO USE VICINITY WORDING FOR SHOWERS. EXPECT THESE SHOWERS TO SLOWLY ADVANCE FROM NORTH TO SOUTH AS FRONT SETTLES THROUGH AND TRIED TO DISPLAY SUCH TIMING IN TAFS. OTHERWISE...DRY LOW LEVELS SHOULD KEEP BOTH CEILINGS AND VISIBILITIES INTO THE VFR RANGE THROUGH THE PERIOD. MSB && .APX WATCHES/WARNINGS/ADVISORIES... RED FLAG WARNING UNTIL 9 PM EDT THIS EVENING FOR MIZ016>036-041- 042. && $$
AREA FORECAST DISCUSSION
NWS HOUSTON/GALVESTON TX
955 AM CDT MON MAY 7 2007 .DISCUSSION... SHRA UNDER THE CAP SEEMED TO HAVE MIXED OUT FOR THE TIME BEING. MORNING SOUNDING AT CRP SUGGESTING AN UNBREAKABLE CAP ACROSS SW PORTION OF OUR AREA. ACARS AND LCH SOUNDING LESS CAPPED THAN YDAY BUT WOULD STILL NEED TEMPS A LITTLE ABOVE FCSTED HIGHS TO BREAK. LAYER ABOVE THE CAP IS FAIRLY DRY SO NOT OVERLY CONCERNED EVEN IF THERE ARE SOME BREAKS. WILL TWEAK CLOUD COVER TO MATCH CURRENT SAT IMAGES FOR THE UPDATE. REST OF THE PACKAGE LOOKING GOOD. 47 && .PRELIMINARY POINT TEMPS/POPS... COLLEGE STATION (CLL) 89 69 87 66 85 / 20 10 10 10 10 HOUSTON (IAH) 87 69 86 64 85 / 20 10 10 10 10 GALVESTON (GLS) 83 72 83 71 81 / 10 10 10 10 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...SMALL CRAFT SHOULD EXERCISE CAUTION BAYS AND 0-20NM GULF. SMALL CRAFT ADVISORY 20-60 NM GULF. && $$
AREA FORECAST DISCUSSION
NWS HOUSTON/GALVESTON TX
752 AM CDT MON MAY 7 2007 .UPDATE... QUICK UPDATE TO EXPAND SHOWER COVERAGE FARTHER WEST AND INCREASE POPS NORTH TODAY. AM A LITTLE CONCERNED AFTER SEEING THE 11Z ACARS SOUNDINGS THAT THE CAP COULD BE BREAKABLE THIS AFTERNOON IF TEMPERATURES REACH 88-89. WILL LET NEXT SHIFT GET A LOOK AT NEW GUIDANCE TO MAKE THAT DECISION. 45 && .PREV DISCUSSION... /ISSUED 639 AM CDT MON MAY 7 2007/ AVIATION... STILL SOME LOW STRATUS HANGING ACROSS SE TX THIS MORNING. A FEW TERMINALS HAVE SCATTERED CLOUDS ALREADY AND SHOULD SEE CEILINGS LIFT LATER IN THE MORNING. VFR CONDITIONS ARE EXPECTED FOR THE AFTERNOON AND INTO THE NIGH TIME HOURS. STRATUS MAY RETURN TO SOME AREAS IN THE MORNING BUT MAY ONLY BE SCATTERED FARTHER NORTH. SE WINDS WILL CONTINUE AS WELL BUT SHOULD NOT BE AS STRONG AS THE LAST COUPLE OF DAYS. STILL SHOULD SEE 10-15KTS ACROSS THE AREA. 39 PREV DISCUSSION... /ISSUED 415 AM CDT MON MAY 7 2007/ DISCUSSION... SHOWERS REDEVELOPING OVER THE EASTERN HALF THE AREA AGAIN THIS MORNING. WINDS HAVE RELAXED A BIT FROM LAST NIGHT THOUGH TEMPERATURES AND DEWPOINTS RELATIVELY UNCHANGED. AS CLOUDS SCATTER OUT THIS MORNING SHOULD SEE A QUICK WARMUP AND EXPECTING TO SEE TEMPERATURES TOPPING OUT IN THE UPPER 80S. UPPER TROUGH STILL IN PLACE FROM ND- CO- AZ. S/W MOVING INTO THE COASTAL BEND THIS MORNING WILL MOVE INTO THE AREA BUT WILL GET DAMPENED AS IT NEARS THE RIDGE AXIS FROM BPT- CHI. THE BIG UPPER LOW THAT MODELS HAVE BEEN FORECASTING TO DEVELOP EAST OF CAPE HATTERAS IS CRANKING UP. MODELS BRING THIS SYSTEM DOWN OVER FL (THEN DIVERGE IN SOLUTION) THIS SHOULD SHUNT DRIER CONTINENTAL AIRMASS INTO EAST TEXAS. DEWPOINTS SHOULD DROP INTO THE LOWER 60S AND PERHAPS EVEN AS LOW 59. THE WESTERN TROUGH WILL LIFT OUT TO THE NORTHEAST THEN TURN SOUTHEAST AND SLOWLY SAG DOWN THROUGH NCTX AND INTO SETX. TIMING IS A HUGE QUESTION...GFS IS QUICK WITH THIS SYSTEM AND IT MOVES IT OVER THE CWA BY 00Z SATURDAY...ECMWF IS SLOWER AND HAS OVER THE RED RIVER N OF DFW AT THE SAME TIME. GIVEN THE PROPENSITY OF THE GFS TO BE TO FAST WITH THESE FEATURES HAVE LEANED MORE TOWARD THE ECMWF. POPS THIS MORNING...HAVE CONFINED THEM (20S SHOWERS) TO AREAS MAINLY EAST OF I-45. CAP STILL STRONG AND DONT FORESEE THUNDERSTORMS. THEN THE FORECAST DRIES OUT TONIGHT THROUGH THURSDAY MORNING. HAVE BOOSTED POPS FOR FRIDAY AND SATURDAY (THANKS CRP FOR THE COORDINATION) AND THEY MAY BE NEEDED FOR SUNDAY AS WELL IF ECMWF PANS OUT WITH A BROAD UPPER TROUGH LAID OUT EAST TO WEST OVER THE AREA. MADE VERY SMALL CHANGES TO PREVIOUS TEMPERATURES. AVIATION... LOW STRATUS CONTINUES TO INVADE SE TX TONIGHT. MOST AREAS WILL BE BKN/OVC BETWEEN 1-2KFT WITH SOME PERIODS OF SCT COVERAGE. SE WINDS WILL CONTINUE AS WELL WHICH SHOULD KEEP ANY LOW VSBY FROM DEVELOPING. DO EXPECT LOW STRATUS TO SCATTER OUT MORE TODAY THAN THE PREVIOUS DAYS. WILL SHOW CEILINGS LIFTING THROUGH THE LATE MORNING HOURS WITH SCT CLOUDS DURING THE AFTERNOON. EXPECT THIS TREND TO CONTINUE INTO THE EVENING AND NIGHT. SE WINDS WILL REMAIN STRONG DURING THE DAY BUT SLACK OFF IN THE EVENING AND NIGHT. OTHERWISE...DO NOT EXPECT ANY OTHER AVIATION WEATHER ISSUES. 39 MARINE... WINDS ARE SHOWING SIGNS OF DIMINISHING THIS MORNING. WILL GO AHEAD AND HOLD ONTO SMALL CRAFT ADVISORY OUT 20-60NM UNTIL 16Z. CAUTION FLAGS WILL CONTINUE AFTER 16Z UNTIL 21Z FOR THE SAME AREAS. CLOSER TO SHORE...WILL CONTINUE CAUTION FLAGS FOR THE BAYS THROUGH 10Z WITH CAUTION FOR 0-20NM AREAS UNTIL 16Z. CURRENT TRENDS AND FORECAST DATA ARE FAIRLY CONSISTENT WITH THIS SCENARIO AND FEEL CONFIDENT OF SEAS DROPPING OFF THROUGH THE DAY TODAY. MODEL DATA ALSO CONSISTENT WITH TRENDS OF WEAK WINDS DURING THE MIDDLE OF THE WEEK WITH SEAS DROPPING OFF TO ONLY A COUPLE OF FEET. FAVORABLE MARINE CONDITIONS SHOULD PERSIST INTO THE WEEKEND. 39 && .PRELIMINARY POINT TEMPS/POPS... COLLEGE STATION (CLL) 89 69 87 66 85 / 20 10 10 10 10 HOUSTON (IAH) 87 69 86 64 85 / 20 10 10 10 10 GALVESTON (GLS) 83 72 83 71 81 / 20 10 10 10 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 11 AM CDT THIS MORNING FOR THE FOLLOWING ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL OUT 20 NM...WATERS FROM HIGH ISLAND TO FREEPORT OUT 20 NM. SMALL CRAFT ADVISORY UNTIL 11 AM CDT THIS MORNING FOR THE FOLLOWING ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL 20 NM TO 60 NM...WATERS FROM HIGH ISLAND TO FREEPORT 20 TO 60 NM. SMALL CRAFT SHOULD EXERCISE CAUTION FROM 11 AM THIS MORNING TO 4 PM CDT THIS AFTERNOON FOR THE FOLLOWING ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL 20 NM TO 60 NM... WATERS FROM HIGH ISLAND TO FREEPORT 20 TO 60 NM. && $$ DISCUSSION...45
AREA FORECAST DISCUSSION
NWS SEATTLE WA
915 AM PDT TUE MAY 8 2007 .SYNOPSIS...HIGH PRESSURE ALOFT WILL MOVE EAST...ALLOWING A WEAK LOW PRESSURE SYSTEM TO MOVE ACROSS THE AREA LATE TONIGHT AND WEDNESDAY MORNING FOR A CHANCE OF SHOWERS. HIGH PRESSURE WILL REBUILD OVER THE REGION WEDNESDAY AFTERNOON AND CONTINUE THROUGH FRIDAY. ONSHORE FLOW WILL ALSO INCREASE...RESULTING IN NIGHT AND MORNING CLOUDS ALONG WITH NEAR NORMAL DAYTIME TEMPERATURES. && .SHORT TERM...SATELLITE IMAGERY SHOWS WEAKENING COLD FRONT NOW NEAR 128W SLOWLY MOVING EASTWARD THIS MORNING. LOW LEVEL AMS IN TRANSITION THIS MORNING FROM OFFSHORE TO ONSHORE OVER WESTERN WASHINGTON. WHILE THE CROSS CASCADES ARE STILL FLAT AT 15Z KOTH-KSEA GRADIENT WHICH WAS -3.0 MB AT 09Z IS NOW PLUS 2.0 MB. ACARS SOUNDINGS SHOW STILL SHOW NORTH NORTHEASTERLY WINDS ABOVE THE SURFACE TO 850 MB BUT THE WIND SPEEDS ARE DOWN TO 5 KNOTS OR LESS. CHANGEOVER TO ONSHORE FLOW WILL CONTINUE TODAY AS THE WEAK FRONT OFFSHORE CONTINUES TO APPROACH THE COAST. FRONT STILL TIMED TO MOVE THROUGH WESTERN WASHINGTON OVERNIGHT TONIGHT WITH SOME WEAK CONVERGENCE BEHIND THE FRONT COMING TO AN END WEDNESDAY MORNING. AFTER THAT LITTLE CHANGE IN THE PATTERN THROUGH THE END OF THE WEEK WITH AN UPPER LEVEL TROUGH OFFSHORE AND DIURNAL ONSHORE SURFACE GRADIENTS. CURRENT FORECAST HAS THE TRENDS COVERED. NO UPDATE THIS MORNING. FELTON .LONG TERM...PREVIOUS DISCUSSION FOLLOWS. FOR THIS PERIOD...THE PAC NW WILL GENERALLY BE UNDER THE INFLUENCE OF AN UPPER RIDGE. HOWEVER WITH LOW LEVEL ONSHORE FLOW PREDOMINATING...ANTICIPATE TEMPS TO RUN NEAR CLIMO. A WEAK UPPER TROF MAY MOVE ACROSS THE AREA LATE FRI NIGHT OR EARLY SATURDAY. AT THIS TIME...ONLY A DEEPENING MARINE LAYER...ERGO MORE NIGHT/MORNING STRATUS...OR POSSIBLY DRIZZLE IS EXPECTED WITH THIS FEATURE. && .AVIATION...SHALLOW FOG BURNING OFF QUICKLY AND REMAINDER OF THE DAY WILL ONLY HAVE SOME HIGH CLOUDS TO DEAL WITH. APPROACHING FRONT WILL INCREASE THE HIGH CLOUDS THIS EVENING...BUT MAIN EFFECT WILL BE TO INCREASE ONSHORE FLOW SIGNIFICANTLY LATER TODAY INTO TONIGHT. WILL HAVE STRONG FLOW DEVELOP DOWN THE STRAIT AND MODERATELY STRONG FLOW THROUGH THE CHEHALIS GAP. THIS WILL BEGIN TO KICK IN MID-AFTERNOON ONWARD. KSEA...NO CIG/VIS PROBLEMS. MAIN ISSUE IS WIND. LIGHT WIND THIS MORNING WILL BECOME SW MIDDAY THEN INCREASE TO 9-12KT BY 00Z. CERNIGLIA && .SEW WATCHES/WARNINGS/ADVISORIES...GALE WARNING CENTRAL AND EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA. SMALL CRAFT ADVISORY REMAINING WATERS EXCEPT PUGET SOUND AND HOOD CANAL. $$ WEATHER.GOV/SEATTLE
AREA FORECAST DISCUSSION...UPDATED
NWS GREEN BAY WI
1015 PM CDT TUE MAY 8 2007 .UPDATE...STRUGGLED WITH WHETHER OR NOT TO ADD A CHANCE OF RAIN TO THE FCST TONIGHT...BUT DECIDED TO ADD A CHANCE FOR SEVERAL REASONS. FIRST OF ALL...UPPER LEVEL DYNAMICS ARE FAIRLY STRONG WITH THE APPROACH OF THE POTENT S/W TROF OVER S MN AND THE RRQ OF AN UPPER LEVEL JET MOVG THROUGH. SECOND...THE AIR MASS IS FAIRLY MOIST...WITH PRECIPITABLE WATER VALUES OF 1.13 INCH ON THE 00Z GRB SOUNDING. THE WEAK CAP THAT WAS SEEN AT 700 MB ON THE GRB SOUNDING IS EXPECTED TO ERODE AS THE UPPER TROF APPROACHES. WEAK ELEVATED INSTABILITY WILL BE PRESENT...ALLOWING HIGH BASED SHRA/ISOLD TSRA TO DEVELOP. EXPECT THE SHOWERS TO LINGER AT LEAST INTO MONDAY MORNING...THEN DECREASE AS THE UPPER TROF SHIFTS EAST DURING THE AFTERNOON. WILL LET THE MID SHIFT DEDCIDE WHETHER TO LINGER POPS INTO THE AFTERNOON. INCREASED THE FOG WORDING NEAR LK MICH WITH AN EARLIER EVG UPDATE...AS LIGHT SOUTH-SOUTHEAST WINDS WERE ADVECTING MARINE FOG ONSHORE. TSK REST OF DISCUSSION FROM PREVIOUS SHIFT... .SHORT TERM...TONIGHT AND WEDNESDAY. FORECAST FOCUS ON PRECIPITATION CHANCES. MODELS FAIRLY CONSISTENT PRODUCING QPF ACROSS THE EXTREME WESTERN ZONES TONIGHT AND WEDNESDAY MORNING. HOWEVER THE MODELS ALSO PRODUCED A SWATH ACROSS NORTHWEST WISCONSIN THIS AFTERNOON AND NOTHING HAPPENED. THE MAIN CULPRIT APPEARS TO BE DRY AIR AS TAMDAR SOUNDINGS SHOW A SUBSTANTIAL AMOUNT OF DRY AIR AROUND 700 MB WITH RELATIVE HUMIDITIES AROUND 10%. MOST OF THE MOISTURE IS CONFINED TO LOW LEVELS WITH THE DRY AIR ALOFT INHIBITING CUMULUS DEVELOPMENT AS SEEN BY THE SHALLOWNESS OF THE CUMULUS CURRENTLY ACROSS THE REGION. GIVEN THE SETTING SUN WILL CAUSE THE DISSIPATION OF THE CURRENT CLOUD FIELD AND THE DRY AIR IN ACROSS THE REGION DO NOT SEE MUCH OF A CHANCE FOR PRECIP TONIGHT OR WEDNESDAY AS THE MOISTURE IS TOO FAR AWAY AND NOT DEEP ENOUGH TO OVERCOME THE DRY AIR ALOFT. CURRENT CONVECTION ACROSS MINNESOTA WILL FIZZLE BY THE TIME THE FORCING REACHES WISCONSIN AS THE SUN WILL ALREADY BE DOWN. THEREFORE WILL GO WITH A DRY FORECAST ACROSS THE ENTIRE AREA TONIGHT AND WEDNESDAY. .LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY. LOOKS LIKE A DRY PERIOD WITH MAINLY ZONAL TO NORTHWEST UPPER FLOW AND ONLY WEAK SYSTEMS COMING THROUGH. THE GFS IS STRONGER THAN THE ECMWF WITH A SHORTWAVE COMING DOWN INTO THE GREAT LAKES EARLY NEXT WEEK....BUT THAT/S THE ONLY SIGNIFICANT DIFFERENCE BETWEEN THE TWO. DECIDED TO HOLD OFF ON PRECIPITATION SUNDAY AFTERNOON. SURFACE FRONT IS STILL WAY OUT WEST ACCORDING TO GFS AND DECENT UPPER SUPPORT DOES NOT ARRIVE UNTIL SUNDAY NIGHT. && .AVIATION...VFR CIGS/VIS EXPECTED ACROSS AREA TONIGHT AND WEDNESDAY. ISOLD MVFR CIGS/VIS POSSIBLE BETWEEN 07Z-13Z. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ WEATHER.GOV/GREENBAY
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
330 PM CDT TUE MAY 8 2007 .SHORT TERM...TONIGHT AND WEDNESDAY. FORECAST FOCUS ON PRECIPITATION CHANCES. MODELS FAIRLY CONSISTENT PRODUCING QPF ACROSS THE EXTREME WESTERN ZONES TONIGHT AND WEDNESDAY MORNING. HOWEVER THE MODELS ALSO PRODUCED A SWATH ACROSS NORTHWEST WISCONSIN THIS AFTERNOON AND NOTHING HAPPENED. THE MAIN CULPRIT APPEARS TO BE DRY AIR AS TAMDAR SOUNDINGS SHOW A SUBSTANTIAL AMOUNT OF DRY AIR AROUND 700 MB WITH RELATIVE HUMIDITIES AROUND 10%. MOST OF THE MOISTURE IS CONFINED TO LOW LEVELS WITH THE DRY AIR ALOFT INHIBITING CUMULUS DEVELOPMENT AS SEEN BY THE SHALLOWNESS OF THE CUMULUS CURRENTLY ACROSS THE REGION. GIVEN THE SETTING SUN WILL CAUSE THE DISSIPATION OF THE CURRENT CLOUD FIELD AND THE DRY AIR IN ACROSS THE REGION DO NOT SEE MUCH OF A CHANCE FOR PRECIP TONIGHT OR WEDNESDAY AS THE MOISTURE IS TOO FAR AWAY AND NOT DEEP ENOUGH TO OVERCOME THE DRY AIR ALOFT. CURRENT CONVECTION ACROSS MINNESOTA WILL FIZZLE BY THE TIME THE FORCING REACHES WISCONSIN AS THE SUN WILL ALREADY BE DOWN. THEREFORE WILL GO WITH A DRY FORECAST ACROSS THE ENTIRE AREA TONIGHT AND WEDNESDAY. .LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY. LOOKS LIKE A DRY PERIOD WITH MAINLY ZONAL TO NORTHWEST UPPER FLOW AND ONLY WEAK SYSTEMS COMING THROUGH. THE GFS IS STRONGER THAN THE ECMWF WITH A SHORTWAVE COMING DOWN INTO THE GREAT LAKES EARLY NEXT WEEK....BUT THAT/S THE ONLY SIGNIFICANT DIFFERENCE BETWEEN THE TWO. DECIDED TO HOLD OFF ON PRECIPITATION SUNDAY AFTERNOON. SURFACE FRONT IS STILL WAY OUT WEST ACCORDING TO GFS AND DECENT UPPER SUPPORT DOES NOT ARRIVE UNTIL SUNDAY NIGHT. && .AVIATION...VFR CIGS/VIS EXPECTED ACROSS AREA TONIGHT AND WEDNESDAY. ISOLD MVFR CIGS/VIS POSSIBLE BETWEEN 07Z-13Z. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ KURIMSKI/RDM WEATHER.GOV/GREENBAY
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
252 PM CDT TUE MAY 8 2007 .SHORT TERM...TONIGHT THROUGH FRIDAY FORECAST CONCERNS THIS PACKAGE...SMALL AFTERNOON/EVENING -SHRA/TSRA CHANCES AN TEMPERATURES THRU THE PERIOD. DATA ANALYSIS AT 18Z SHOWED BROAD LOW PRESSURE OVER CENTRAL/EASTERN CAN WITH A WEAK TROUGH SOUTH ACROSS THE LOWER MS VALLEY. VIS IMAGERY SHOWED DIURNAL CUMULUS ACROSS MUCH OF SOUTHERN MN/WI AND NEARBY AREAS...IN AN AREA OF SFC DEW POINTS IN THE LOW 50S TO NEAR 60. DRIER AIR...WITH DEW POINTS IN THE MID 30S TO MID 40S...AND GENERALLY SUNNY SKIES WERE THE RULE OVER NORTHERN MN/FAR NORTHERN WI. A LOW LEVEL CIRCULATION COULD BE SEE IN THE CLOUDS OVER FAR SOUTHWEST MN...AHEAD OF THE MID LEVEL CIRCULATION OVER EASTERN SD... SEEN IN WV IMAGERY. KFSD RADAR SHOWED A FEW SHRA TRYING TO DEVELOP NEAR THE SFC/MID LEVEL CIRCULATIONS...WHILE A LATE MORNING TAMDAR SOUNDING FROM KMSP INDICATED AN INVERSION NEAR 750MB. 08/12Z NAM/GFS LOOK TO HAVE INITIALIZED WELL AND OFFER QUITE SIMILAR SOLUTIONS FOR TONIGHT THRU FRIDAY. AT 500MB...05/12Z AND 06/12Z NAM/GFS RUNS VERIFIED QUITE WELL THIS MORNING WITH BETTER RUN-TO- RUN CONSISTENCY TO GFS. 08/12Z RUNS HAVE AGAIN TRENDED TOWARD A COMPROMISE OF THEIR EARLIER RUNS. FOR 00-36HRS MODELS CONTINUE TO TREND TOWARD A COMPROMISE OF THEIR EARLIER RUNS AS THE WEAKENING TROUGH SLIDES ACROSS THE REGION. FOR 36-84HRS MODELS MAINTAIN RATHER GOOD CONSISTENCY WITH THE UPPER LOW/TROUGH DRIFTING ACROSS THE SOUTHERN PLAINS AND WITH ANOTHER TROUGH TO SLIDE ACROSS THE REGION CENTERED ON 00Z FRI. CHECK OF OBS VS. MODEL DATA AT 18Z SHOWED BOTH NAM/GFS WITH GOOD DEPICTIONS OF THE SFC MASS FIELDS. WV IMAGERY SHOWED BOTH MODELS WITH GOOD DEPICTIONS OF SHORTWAVE DETAILS ACROSS NOAM/EASTERN PAC...WITH NAM A BIT BETTER OVER TX/OK. A BLEND OF NAM/GFS APPEARED BEST WITH 12-18Z PRECIP ACROSS THE CONUS. NO CLEAR MODEL FAVORITE AGAIN TODAY...AND WITH SOLUTIONS QUITE SIMILAR THRU THE SHORT-TERM PERIOD FAVORING ONE OVER THE OTHER LOOKS TO HAVE LITTLE IMPACT ON THE SENSIBLE WEATHER. THUS FAVORED A MODEL BLEND THIS CYCLE...WITH FORECAST CONFIDENCE AVERAGE TO GOOD. FOR THE SHORT TERM...WEAKENING SFC-MID LEVEL CIRCULATION/TROUGH SLIDES EAST ACROSS THE AREA TONIGHT/EARLY WED. MUCH OF THE INSTABILITY AHEAD OF THIS FEATURE DIURNALLY DRIVEN...AND WILL WANE DURING THE EVENING HOURS. MODEL/TAMDAR SOUNDINGS INDICATE AN INVERSION NEAR 750MB. THIS MAY BE TOUGH TO OVERCOME WITH SFC/MIXED LAYER DEW POINTS DROPPING INTO THE LOWER/MID 50S EARLY THIS AFTERNOON AND MODIFIED MODEL SOUNDINGS WITH THESE DEW POINTS INDICATE LESS THAN 100 J/KG OF CAPE. DID LEAVE SMALL -SHRA/ISOLD TSRA CHANCE FOR THIS EVENING...BUT CONFIDENCE NOT HIGH WITH THIS. WEAK SHORTWAVE RIDGING ALOFT BUILDS ACROSS THE AREA FOR WED. EQUAL AREA TECHNIQUE APPLIED TO MODEL SOUNDINGS WED AFTERNOON GIVES BOUNDARY LAYER DEW POINTS MOSTLY IN THE 50-55F RANGE WITH MINIMAL INSTABILITY. WITH WEAK SFC-MID LEVEL RIDGING OVER THE AREA AND LACK OF SUBSTANTIAL CONVERGENCE/FORCING MECHANISMS...REMOVED SMALL -SHRA/ TSRA CHANCE FOR WED AFTERNOON. NEXT TROUGH/SHORTWAVE PUSHES ACROSS SOUTHERN CAN AND NORTH OF THE REGION THU/THU NIGHT...WITH A COLD FRONT DROPPING ACROSS THE AREA LATE THU/THU NIGHT. MOISTURE REMAINS SCANT AHEAD OF THIS FRONT...WITH BOUNDARY LAYER DEW POINTS AGAIN MIXING TO THE UPPER 40S/LOW 50S. BASED ON THESE DEW POINTS...MODEL SOUNDINGS STILL INDICATE UP TO 500 J/KG OF CAPE ACROSS THE NORTH/ EAST END OF THE FORECAST AREA THU AFTERNOON. SOME WEAK 1000-850MB FN AND QN CONVERGENCE INDICATED WITH THE TROUGH/FRONT. MAY YET NEED A SMALL -SHRA/ISOLD TSRA CHANCE WITH THE FRONTAL PASSAGE A FEW HOURS EITHER SIDE OF 00Z FRI...BUT NOT ENOUGH CONFIDENCE YET TO ADD THIS SMALL POP AND NEIGHBORING FORECAST GRIDS ARE DRY AS WELL FOR NOW. COOLER...DRIER CANADIAN HIGH PRESSURE BUILDS IN FOR FRI WITH A LIGHT/MDT NORTHEAST FLOW ACROSS THE AREA. GUIDANCE LOWS QUITE SIMILAR FOR TONIGHT/WED/THU NIGHTS AND LOOK TO BE IN THE BALLPARK. FAVORED BLEND OF GUIDANCE HIGHS WED. WITH SOUTHWEST FLOW/LOW LEVEL WARM ADVECTION/MIXING AHEAD OF THE FRONT ON THU...RAISED HIGHS TOWARD BLEND OF GFS/NAM GUIDANCE VALUES. FAVORED BLEND OF GFS MEX/ENSEMBLE MOS AND HPC GUIDANCE FOR FRI WITH WHAT SHOULD BE PLENTY OF SUNSHINE IN A DRIER AIRMASS. .LONG TERM...FRIDAY NIGHT THROUGH TUESDAY 08/00Z GFS/ECMWF IN REASONABLE AGREEMENT THRU 00Z SUN...THEN DIVERGE WITH THE STRENGTH/TIMING OF SHORTWAVES ACROSS NOAM IN THE 144-168HR TIME-FRAME. GFS AT ODDS WITH ECMWF WITH SHORTWAVE TROUGH OR RIDGING OVER THE REGION MON INTO TUE. ECMWF OFFERS THE BETTER CONSISTENCY TO ITS 07/00Z RUN THRU 168HRS...WITH GFS SLOWLY TRENDING TOWARD IT. GEM LOOKS TO SIDE WITH THE ECMWF WHILE UKMET LOOKS CLOSER TO GFS SOLUTION...WHILE GFS ENSEMBLE MEAN BY MON/TUE LOOKS LIKE A GFS/ECMWF COMPROMISE. TREND OF MODELS SINCE 07/00Z RUNS IS LESS PROGRESSIVE WITH THE UPPER LOW OVER THE NORTHEAST PAC AND TOWARD MORE RIDGING ALOFT OVER WESTERN/CENTRAL NOAM IN THE SUN/MON/TUE TIME-FRAME. AS EXPECTED...MODELS STRUGGLING WITH TIMING OF SHORTWAVE FEATURES THRU THE QUASI-ZONAL FLOW ACROSS NOAM IN DAYS 4-7. FAVORED A DAY 4-7 SOLUTION SIMILAR TO HPC PMDEPD...LEANING ON MORE CONSISTENT ECMWF AND GFS ENSEMBLE MEAN. WITH CONSIDERABLE MODEL VARIABILITY AND INHERENT TIMING DIFFICULTIES IN QUASI-ZONAL FLOW...FORECAST CONFIDENCE BELOW AVERAGE FOR SAT THRU TUE. ECMWF/ENSEMBLE CONSENSUS SETTLES CANADIAN HIGH PRESSURE ACROSS THE REGION FOR FRI NIGHT INTO SAT NIGHT. FOR SUN INTO TUE MODELS DIFFER ON THE DETAILS...BUT A WEAK SHORTWAVE MOVING THRU THE NEARLY ZONAL FLOW BRINGS A SFC LOW/TROUGH AND FRONTAL BOUNDARY INTO THE REGION SUN...WITH THE BOUNDARY AND A WAVE OR TWO ALONG IT TO THEN REMAINING IN/NEAR THE AREA FOR MON INTO TUE. MOISTURE SHOULD BE INCREASING SOUTH OF/INTO THE TROUGH/FRONTAL BOUNDARY FOR SUN THRU TUE...FOR SOME SMALL -SHRA/ TSRA CHANCES. FAVORED A GFS MEX/ENSEMBLE MOS AND HPC GUIDANCE COMPROMISE FOR MINS/MAXES THRU THE PERIOD...WHICH BLENDS QUITE WELL WITH NEIGHBORING FORECAST GRIDS. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ RRS
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1237 AM CDT WED MAY 9 2007 .DISCUSSION FOR EVENING UPDATE... 901 PM CDT MINOR UPDATE TO CURRENT GRIDS/FCST TO RAISE MIN TEMPS A LITTLE AWAY FROM LAKE...LOWER PCPN AMOUNTS AND TWEAK POPS SLIGHTLY. WEAK SFC TROF AND LLVL DEWPT AXIS HAS BEEN FROM ECNTRL/SERN IL INTO NERN IND DURG AFTN/EARLY EVENING HOURS. WEAK S/WV NOTED IN PROFILER DATA MOVG ACROSS THAT AREA HELPED TO INITIATE RW/TRW IN WEAKLY UNSTABLE AND WEAKLY SHEARED ENVIRONMENT...WITH SOME ACTIVITY CLIPPING FAR SOUTHEAST PARTS OF CWA THIS EVENING. FARTHER TO THE NORTHWEST...ACARS SOUNDINGS OUT OF KORD SINCE THIS AFTN HAVE SHOWN PERSISTANT CAP IN IN PLACE WITH +10 C TEMPS 780-750 MB RANGE...WHICH ALONG WITH WEAKER CONVERGENCE AND LOWER SFC DWPTS HAVE INHIBITED CONVECTIVE DEVELOPMENT. 00Z DVN RAOB AND CURRENT KORD ACARS PROFILES INDICATE MID LEVEL TEMPS COOLING SLIGHTLY WITH APPROACH OF UPPER TROUGH OVER MN...RESULTING IN SLIGHTLY STEEPER MID LVL LAPSE RATES. WITH APPROACH OF UPPER TROUGH AND JET MAX PROPAGATING EAST ACROSS IA FCST MODELS CONTINUE TO INDICATE POTENTIAL FOR ELEVATED CONVECTION DEVELOPING OVRNGT. HOWEVER...LOW LEVEL FORCING NOT PARTICULARLY IMPRESSIVE WITH H85 FLOW ONLY 10-15 KTS AT BEST. STILL GIVEN INCREASINGLY FAVORABLE MID LVL FORCING AM HESITANT TO PULL POPS FROM GOING GRIDS/FCST. HAVE HOWEVER TEMPERED QPF AMOUNTS...AND HAVE BACKED OF TO CHC RW/ISOLATED TSRA OVRNGT. RATZER PREVIOUS DISCUSSION 315 PM CDT PRECIP CHANCES MAINLY TONIGHT AND WEDNESDAY WILL CONTINUE TO BE THE MAIN FORECAST CONCERN. WEAK SFC PRESSURE FIELD NOTED IN SUBJECTIVE SFC ANALYSES EARLY THIS AFTERNOON WITH A WEAK SURFACE TROUGH ACROSS FAR NORTHEAST ILLINOIS/NORTHWEST INDIANA. VISIBLE SATELLITE IMAGERY INDICATING ENHANCED CU AND A FEW THUNDERSTORMS DEVELOPING ALONG THIS WEAK BOUNDARY WITH SPC RUC MESOSCALE ANALYSIS GRAPHICS INDICATING 1000-1500 J/KG OF MUCAPE EXTENDING FROM SOUTHERN ILLINOIS THROUGH NORTH CENTRAL INDIANA. ACARS SOUNDINGS INDICATING ISOTHERMAL LAYER IN THE 800-750 HPA LAYER WHICH LIKELY IS PROVIDING SOME WEAK INHIBITION THIS AFTERNOON. DURING THE EARLY EVENING...EXPECTING TEMPS IN THIS LAYER TO COOL AS UPPER LOW ACROSS SOUTHEAST SOUTH DAKOTA AND FAR NORTHWEST IOWA CONTINUES TO TRACK EASTWARD DAMPENING THE MID LEVEL RIDGE IN PLACE ACROSS THE SOUTHERN GREAT LAKES REGION. OUTSIDE OF PEAK DIURNAL HEATING...NOT MUCH UPPER FORCING TO GET THINGS GOING LATE THIS AFTERNOON AND EARLY THIS EVENING...AND BEST CHANCES OF LATE AFTERNOON THUNDER WILL LIKELY REMAIN ACROSS EAST CENTRAL ILLINOIS/NORTH CENTRAL INDIANA. BEST CHANCES OF PRECIP FOR LOT CWA STILL APPEAR TO BE CONFINED TO THE OVERNIGHT PERIOD AND THROUGH THE EARLY MORNING HOURS AS AFOREMENTIONED UPPER LOW APPROACHES THE AREA. AS THIS UPPER LOW APPROACHES MODELS ARE IN GENERAL AGREEMENT IN REFOCUSING SFC LOW A LITTLE FURTHER BACK WEST INTO NORTH CENTRAL ILLINOIS. MAX UPPER FORCING SHOULD OCCUR IN THE 09Z-12Z TIME FRAME...AND NAM/GFS CONTINUE TO INDICATE WEAK LOW LEVEL MOISTURE CONVERGENCE ACROSS MAINLY SOUTHEAST HALF OF THE FORECAST AREA LATE TONIGHT WITH ELEVATED INSTABILITY ON THE ORDER OF 500-1000 J/KG. SREF ENSEMBLE POPS EVEN APPROACHING THE LIKELY CATEGORY ACROSS NORTHWEST INDIANA OVERNIGHT...BUT FOR NOW HAVE OPTED TO GO WITH HIGH CHANCE POPS GIVEN REMAINING UNCERTAINTY AS TO TIMING BEST UPPER FORCING. FOR WEDNESDAY...WILL KEEP THESE HIGH CHANCE POPS ACROSS EASTERN PORTIONS OF THE CWA DURING THE MORNING...WITH LOWER CHANCE POPS IN THE AFTERNOON AS THE UPPER WAVE BEGINS TO EXIT THE AREA. SOME CONCERN IN THE AFTERNOON FOR A FEW SHOWERS DEVELOPING ALONG THE LAKE BREEZE BOUNDARY...BUT BY MID AFTERNOON THE BULK OF THE PRECIPITATION SHOULD BE SHIFTING EAST OF THE AREA. DID NUDGE UP HIGH TEMPS A BIT FOR WED BASED ON LOW LEVEL THERMAL PROGS FROM THE 12Z MODEL RUNS...WITH HIGHS NEAR 80 MOST LOCATIONS...BUT COOLER CLOSER TO LAKE MICHIGAN ACROSS NORTHEAST ILLINOIS/NORTHWEST INDIANA AS WINDS BECOMING NORTHERLY IN THE WAKE OF WEAK SURFACE WAVE TRACKING EAST OF THE AREA. WEAK MID/UPPER RIDGING BUILDS INTO NORTHERN ILLINOIS/NORTHWEST INDIANA TOMORROW NIGHT WITH DRY CONDITIONS EXPECTED ACROSS MOST OF THE AREA. ON THURSDAY HAVE INCLUDED LOW POP MENTION FOR TSRA ACROSS FAR SOUTHERN PORTIONS OF CWA AS WEAK SHORT WAVES EJECTING EASTWARD FROM CUT-OFF SOUTHERN STREAM LOW APPROACH THE REGION. ATTENTION WILL THEN TURN TO TIMING FROPA IN ASSOCIATION WITH FAST MOVING NORTHERN STREAM SHORT WAVE MOVING ACROSS SOUTHERN CANADA. LATEST GFS HAS COME IN A BIT FASTER WITH THIS TROUGH PASSAGE ON FRIDAY. DID COOL TEMPS A BIT ON SATURDAY GIVEN 1025 HPA SFC ANTICYCLONE TRACKING THROUGH THE NORTHERN LAKES WITH NORTHEAST FLOW ACROSS THE AREA. VERY FEW CHANGES WERE NEEDED FOR THE EXTENDED PART OF THE FORECAST. FOCUS WILL CONTINUE TO BE ON MORE ACTIVE NORTHERN STREAM AND POSSIBILITY OF NEXT FRONTAL PASSAGE LATE MONDAY. MAINTAINED CHANCE OF THUNDER ON MONDAY WITH MILD TEMPS CONTINUING IN ADVANCE OF THE FRONT. MARSILI && .AVIATION... 1237 AM CDT TWO WEAK LOWS ARE OVER SOUTHERN SHORES OF LAKE MICHIGAN AND JUST NORTH OF INDIANAPOLIS. THE UPPER TROUGH SEEN ON THE 700 MB PROFILER DATA AND WATER VAPOR IMAGERY WAS OVER MINNESOTA AND IOWA. THIS TROUGH WILL MOVE EAST INTO MICHIGAN BY THIS EVENING. THIS WILL PROVIDE THE INSTABILITY AND LIFT FOR THUNDERSTORMS THIS MORNING. WILL LEAVE VCTS IN THE TAFS THIS MORNING AND WILL UPDATE IF THE THUNDERSTORMS AND SHOWERS BECOME MORE NUMEROUS. THE WEAK LOWS HAVE A SMALL PRESSURE GRADIENT SO THE WIND WILL BE LIGHT AND VARIABLE THIS MORNING. WILL FORECAST A NORTHWEST WIND UNTIL THE AFTERNOON. THAT IS WHEN A LAKE BREEZE IS EXPECTED. EXPECT THE CEILINGS TO REMAIN VFR BUT FOG MAY DEVELOP TONIGHT. THE DEWPOINTS ARE RATHER HIGH INDICATING A LOT OF MOISTURE AWAY FROM THE LAKE. && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LK...NONE. && $$
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
320 AM PDT WED MAY 9 2007 .SHORT TERM... TOUGH NEXT COUPLE OF DAYS FOR LOW CLOUD FORECAST AND BY EXTENSION TEMP FORECASTS. CURRENTLY A SHALLOW MARINE LAYER HAS FORMED OVER THE CENTRAL COAST SQUASHED BY A SERIOUSLY STRONG AND LOW INVERSION. AS EXPECTED THIS HAS RESULTED IN DENSE FOG NEAR THE BEACHES. A LITTLE TENDRIL OF LOW CLOUDS IS SNAKING ITS WAY DOWN THE SBA CHANNEL AND THE VENTURA COUNTY WEST COAST MAY SEE SOME EARLY MORNING CLOUDS. LATEST ACARS OUT OF KLAX STILL SHOWS 81 DEGREES AT 2200 FEET. GRADIENTS ARE TRENDING ONSHORE BY 3MB AND THIS SHOULD HELP THE SEABREEZE INTO THE COASTAL ZONES WHICH GIVEN THE STRENGTH OF THE INVERSION WILL BE THE ONLY AREAS TO FEEL IT SO COOLER AT THE COAST BUT STILL ROASTY TOASTY INLAND. THE RIDGE MOVES EASTWARD BY 12 THURSDAY AND THE GFS SHOWS A LITTLE WAVE EMBEDDED IN THE SW FLOW TO THE WEST OF THE RIDGE. THIS COMBINED WITH A GOOD ONSHORE TREND SHOULD MAKE FOR A DECENT MARINE LAYER... BUT WRF SHOWS NO SIGN WHAT SO EVER OF A MARINE LAYER. HARD TO MAKE THE CALL BUT WITH CLOUDS NOW MANY HUNDREDS OF MILES CLOSER TO THE COAST THINK PATCHY IS THE LEAST ON CAN GO. LOWER HGTS AND BETTER ONSHORE PUSH WILL RESULT IN COOLING EVERYWHERE WITH THE GREATEST AMOUNT OCCURRING IN THE TRANSITION ZONE FROM THE COASTAL TO THE VALLEYS ZONES. DO HAVE TO BE CAREFUL WITH CLEARING AS POWERFUL LOW INVERSIONS CAN MAKE CLEARING TRICKY. SOUTHWEST FLOW GOING UP THE BACKSIDE OF THE RIDGE CONTINUES FRIDAY. THE MARINE LAYER SHOULD GET FURTHER INLAND AND MORE COOLING SHOULD OCCUR COASTS AND VALLEYS. CAN`T SEE TOO MUCH COOLING INLAND WITH H5 HGTS NEAR 583DM. .LONG TERM... EC AND GFS STAY IN PRETTY GOOD AGREEMENT UNTIL TUESDAY MORNING AND THEN GO THEIR SEPARATE WAYS. NO MAJOR PATTERN CHANGES IN STORE FOR THE AREA. OVER THE WEEKEND THE UPPER RIDGE MOVES FAR ENOUGH EASTWARD TO ALLOW THE LARGE SCALE TROF TO MOVE OVER CA. THIS SHOULD BE ENOUGH TO CREATE A DEEP VALLEY PENETRATING STRATUS DECK. HGTS FALL TO ABOUT 578DM SO IT WILL BE MUCH COOLER EVERYWHERE. NOT MUCH CHANGE MONDAY...THE TROF IS A LITTLE WEAKER STILL LOW FOR NIGHT TO MORNING MARINE LAYER AND LITTLE ELSE. BY TUESDAY THE EC HAS A SHARPER SLOWER TROF OFF OF THE COAST WHILE THE GFS HAS A WEAK SAGGY LOW OVER CALIFORNIA. NEITHER SOLUTION WOULD MAKE A GREAT DEAL OF DIFFERENCE IN THE WEATHER. WARMED THINGS UP A COUPLE OF DEGREES BUT KEPT THE LOW CLOUD WORDING GOING. && .AVIATION... 09/1030Z MORNING CLOUDS ACROSS THE CENTRAL COAST WILL RESULT IN LIFR CONDS THROUGH MID MORNING. A TENDRIL OF CLOUDS APCHG KOXR MIGHT BRING IN SOME IFR FLYING CONDS AROUND SUNRISE. KLAX APCH MERGE SITE FROM KPOC TO KONT WILL HAVE SMOKE LAYERS. A BETTER CHC OF SOME LOW CLOUDS FOR KLAX AND KLGB TONIGHT. KLAX...HIGH CONFIDENCE IF VFR TAF THROUGH LATE THIS EVENING. NOT MUCH CONFIDENCE IN TONIGHT FORECAST WITH REGARD TO THE PM ONSET OF LOW CLOUDS IN ANY AT ALL. APCH MERGE SECTOR NR KONT WILL HAVE FU LAYERS. KBUR...HIGH CONFIDENCE IN VFR TAF. LESS WINDS TODAY AND TURBULENCE SHOULD BE INFREQUENT AND LIGHT. $$ .LOX WATCHES/WARNINGS/ADVISORIES... RED FLAG WARNING (SEE LAXRFWLOX). && $$ PUBLIC...RORKE AVIATION...THOMPSON WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION...UPDATED
NWS TALLAHASSEE FL
1100 AM EDT WED MAY 9 2007 ...EARLY-SEASON SUBTROPICAL STORM FORMS OFF N FLA COAST... ...STORM TO LIKELY HAVE LITTLE OR NO IMPACT OF LOCAL AREA... AIR FORCE PLANE THIS MORNING DETERMNIED THAT STORM LOCATED AROUND 140 SE OF SAVANNAH MOVING TO THE W AT 3 MPH WITH A GRADUAL TURN TO THE SW REST OF TODAY. WINDS INCREASING WITH HEIGHT WRN HALF OF CIRCULATION AND DECREASING WITH HEIGHT ERN HALF WITH TSTM ACTIVITY LITTLE CLOSER TO CENTER...ALBEIT FAVORING ERN SEMICIRCLE COMPARED TO YESTERDAY. SLIGHT UPPER OUTFLOW COMMENCING BUT REMAINS EMBEDDED WITHIN LARGE DEEP-LYR TROUGH. ___________________________________________________________________ .PREV DISCUSSION... .SYNOPSIS... SKIES RANGED FROM SUNNY WEST OF APALACH RIVER TO CLOUDY WITH CIGS 2-3K WELL EAST OF THE RIVER. TEMPS RUNNING 67-71...DEW POINTS FROM UPPER 50S WELL E OF RIVER TO AROUND 50 WELL WEST OF RIVER. 24 HR TEMP/DEW POINT COMPARISON SHOWS THAT LOCAL AIRMASS 5-10 DEGREES WARMER THAN SAME TIME YESTERDAY. DEW POINTS RANGED FROM 4-9 DEGREES HIGHER WELL WEST TO 20 DEGREES HIGHER WELL EAST OF RIVER. WINDS NORTH NEAR 10 MPH WEST TO NEAR 15 MPH EAST OF RIVER. .AT UPPER LEVELS... LOOKING AT THE BIG PIX...MOST CONUS ACTIVITY REMAINS IN NRN STREAM. WEAK SHORTWAVE TROUGH OVER THE PACIFIC NW WILL MOVE EWD. UPPER LEVEL RIDGE FORECAST TO DEVELOP ACROSS THE FOUR CORNERS REGION TONIGHT. SHORT WAVE WILL PUSH RIDGE AXIS ACROSS THE NRN ROCKIES ON THU AND SRN ROCKIES ON FRI. DOWNSTREAM UPPER-LEVEL TROUGH AND CLOSED-LOW OVER THE SRN PLAINS TONIGHT WITH NRN HALF MOVING SLOWLY EWD WITH LOW TO ACROSS THE GREAT LAKES REGION TONIGHT AND INTO THE NERN U.S. THURSDAY. IN SRN STREAM...TROUGH AXIS EXTENDS SWWD ACROSS SRN N MEX SHUD MOVE EWD AND REACH W TX THIS EVENING. ABOVE RIDGE FROM CENTRAL GULF THRU MIDWEST WILL WEAKEN NEXT FEW DAYS. THIS WILL ALLOW SRN BRANCH OF UPPER TROUGH TO MOVE EWD INTO THE WRN GULF OF MEXICO AND WEAKEN AS IT MOVES TOWARDS ERN GULF THRU FRIDAY. .AT LOWER LEVELS... HIGH PRESSURE REMAINS CENTERED OVER THE MID-ATLANTIC STATES BUT RIDGING DOWN THE LEE SIDE OF THE APPALACHIANS HAS WEAKENED..HENCE LOCAL GRADS HAVE WEAKENED. STACKED NON TROPICAL LOW 150 E OF JAX CONTINUES TO SPIN SLOWLY WESTWARD AROUND 5 MPH TOWARDS THE SE GA/NE FL COAST. MOST SHOWERS AND ISOLATED THUNDERSTORMS ASSOCIATED WITH THIS SYSTEM REMAIN OFFSHORE. LOW LEVEL MOISTURE CONTINUES TO INCREASE...ESPECIALLY EAST OF THE RIVER AS REFLECTED IN ABOVE DEW POINT CONTRASTS. HOWEVER DEEP SUBSIDENCE DRYING IS NOTED ON TIME HEIGHT CROSS SECTIONS AND 12Z SOUNDINGS. I.E. 12Z JAX AND TAE SOUNDINGS WITH 1.38 AND 0.96 INCH PWATS RESPECTIVELY. BOTH WITH NLY FLOW FROM SURFACE TO ABOVE 50K FEET. .SHORT TERM...(THIS AFTERNOON THROUGH FRIDAY NIGHT) MODELS CONTINUE IN FAIRLY GOOD AGREEMENT WITH THE LOW PRESSURE SYSTEM WILL APPROACHES THE COAST TONIGHT AND MOVES IT INLAND OVER NORTHEAST FLORIDA ON THURSDAY. BECAUSE LATEST SATELLITE PIX SHOW LOW ACQUIRING SOME CHARACTERISTICS OF SUB-TROPICAL CYCLONE...NHC SENDING AN AIRCRAFT AND SYSTEM MAY BE UPGRADED TO A SUB-TROPICAL STORM ANDREA LATER THIS MORNING. ANY SIGNIFICANT IMPACTS WILL LIKELY BE FOCUSED ACROSS COASTAL COUNTIES. ANY LOCAL PRECIP DEPENDS ON WHICH MODEL WINS OUT. BOTH GFS AND NAM ARE IN GOOD AGREEMENT WITH A GRADUAL WEAKENING AND WEST/SOUTHWEST RETROGRESSION OF LOW OVER THE NEXT 72 HOURS. HOWEVER...THERE ARE SUBTLE DIFFERENCES WITH HANDLING OF LOW. THE NAM LEAVES IT OVER NORTH FLORIDA AND DRIFTS IT SLOWLY WNW INTO THE FLORIDA PANHANDLE ON FRIDAY. IT HAS MORE LOW LEVEL MOISTURE TO WORK WITH AND AS A RESULT PRODUCES SLIGHTLY HIGHER POPS FOR OUR CWA. CONVERSELY...THE GFS TRACKS A BIT FURTHER SWD... GENERALLY DUE W TODAY AND THEN SW TOMORROW. THUS IT DROPS A WEAKER LOW INTO CENTRAL FLORIDA LATE THURS WHERE IT BECOMES STATIONARY AND WEAKENS THRU FRI. THIS COULD AL CHANGE AFTER NHC ISSUES ITS UPDATE. WHICHEVER MODEL PROVES CORRECT...MEAGER RAIN CHANCES FOR CWA WITH DRY SLOT PERSISTING ACROSS ALL BUT ERN MOST CWA AND EVEN THERE MAINLY INCREASING CLOUDS WITH 10-20 PCT TODAY AND 20-30 PCT TOMORROW IN LIGHT RAIN OR SPRINKLES. COMBO OF WEAKENING UPPER TROUGH AND REMNANTS OF LOW LEVEL MOISTURE FORM SURFACE LOW MAY SQUEEZE OUT WDLY SCT SHWRS ON FRI. TEMPS WILL BE AT OR ABOVE CLIMO THROUGH THE PERIOD. && .AVIATION... ALTHOUGH ABOVE WEST ATLANTIC CYCLONE WILL CONTINUE TO DRAW CLOSER TO THE SOUTHEAST U.S. COAST LATER TODAY...WE EXPECT MOST OF THE LOW LEVEL MOISTURE TO REMAIN EAST OF OUR TAF SITES. THE ONLY TERMINAL EXPECTED TO HAVE PERIODIC CEILINGS IS KVLD...BUT EVEN THEN THE CEILINGS WILL LIKELY BE VFR. SCATTERED SHOWERS WILL DEVELOP ACROSS SOUTHEAST GA AND NORTHEAST FL THIS AFTERNOON...BUT THE PROBABILITY OF THIS RAIN AFFECTING KVLD IS TOO LOW (ABOUT 20 PERCENT) TO INCLUDE MENTION IN THE TAF. N TO NW WINDS OF 10-15 KT ARE EXPECTED AT ALL THE TERMINALS BY LATE MORNING AND AFTERNOON...WITH SOME GUSTS NEAR 25 KT. THE NORTHERLY FLOW WILL LIKELY KEEP THE SMOKE (FROM THE SOUTHEAST GA AND NORTH FL FIRES) EAST OF OUR TERMINALS...BUT IT WILL AFFECT OUR TWEB ROUTES WITH AREAS OF REDUCED VISIBILITY. && .MARINE...WINDS WILL MOSTLY BE OFFSHORE THROUGH FRIDAY THEN BACK TO THE WEST OVER THE WEEKEND. WINDS AND SEAS WILL BE BELOW SCEC CRITERIA. && .FIRE WEATHER...A RED FLAG WARNING REMAINS IN EFFECT THIS AFTERNOON/EVENING FOR ALL THE EASTERN FLORIDA PANHANDLE AND MOST OF THE WESTERN BIG BEND DUE TO A COMBINATION OF LOW RH...WINDS AND HIGH DISPERSION INDICES. NO CONCERNS FOR THE REMAINDER OF THE WORK WEEK DUE TO INCREASING LOW LEVEL MOISTURE. && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...RED FLAG WARNING THIS AFTERNOON FOR THE FOLLOWING ZONES: INLAND WALTON...HOLMES...WASHINGTON...JACKSON...BAY... CALHOUN...GULF...GADSDEN...LIBERTY...FRANKLIN...LEON AND WAKULLA. && $$ AVIATION/FIRE WX...MROCZKA PUBLIC/MARINE...BLOCK
AREA FORECAST DISCUSSION
NWS TALLAHASSEE FL
915 AM EDT WED MAY 9 2007 .SYNOPSIS... SKIES RANGED FROM SUNNY WEST OF APALACH RIVER TO CLOUDY WITH CIGS 2-3K WELL EAST OF THE RIVER. TEMPS RUNNING 67-71...DEW POINTS FROM UPPER 50S WELL E OF RIVER TO AROUND 50 WELL WEST OF RIVER. 24 HR TEMP/DEW POINT COMPARISON SHOWS THAT LOCAL AIRMASS 5-10 DEGREES WARMER THAN SAME TIME YESTERDAY. DEW POINTS RANGED FROM 4-9 DEGREES HIGHER WELL WEST TO 20 DEGREES HIGHER WELL EAST OF RIVER. WINDS NORTH NEAR 10 MPH WEST TO NEAR 15 MPH EAST OF RIVER. .AT UPPER LEVELS... LOOKING AT THE BIG PIX...MOST CONUS ACTIVITY REMAINS IN NRN STREAM. WEAK SHORTWAVE TROUGH OVER THE PACIFIC NW WILL MOVE EWD. UPPER LEVEL RIDGE FORECAST TO DEVELOP ACROSS THE FOUR CORNERS REGION TONIGHT. SHORT WAVE WILL PUSH RIDGE AXIS ACROSS THE NRN ROCKIES ON THU AND SRN ROCKIES ON FRI. DOWNSTREAM UPPER-LEVEL TROUGH AND CLOSED-LOW OVER THE SRN PLAINS TONIGHT WITH NRN HALF MOVING SLOWLY EWD WITH LOW TO ACROSS THE GREAT LAKES REGION TONIGHT AND INTO THE NERN U.S. THURSDAY. IN SRN STREAM...TROUGH AXIS EXTENDS SWWD ACROSS SRN N MEX SHUD MOVE EWD AND REACH W TX THIS EVENING. ABOVE RIDGE FROM CENTRAL GULF THRU MIDWEST WILL WEAKEN NEXT FEW DAYS. THIS WILL ALLOW SRN BRANCH OF UPPER TROUGH TO MOVE EWD INTO THE WRN GULF OF MEXICO AND WEAKEN AS IT MOVES TOWARDS ERN GULF THRU FRIDAY. .AT LOWER LEVELS... HIGH PRESSURE REMAINS CENTERED OVER THE MID-ATLANTIC STATES BUT RIDGING DOWN THE LEE SIDE OF THE APPALACHIANS HAS WEAKENED..HENCE LOCAL GRADS HAVE WEAKENED. STACKED NON TROPICAL LOW 150 E OF JAX CONTINUES TO SPIN SLOWLY WESTWARD AROUND 5 MPH TOWARDS THE SE GA/NE FL COAST. MOST SHOWERS AND ISOLATED THUNDERSTORMS ASSOCIATED WITH THIS SYSTEM REMAIN OFFSHORE. LOW LEVEL MOISTURE CONTINUES TO INCREASE...ESPECIALLY EAST OF THE RIVER AS REFLECTED IN ABOVE DEW POINT CONTRASTS. HOWEVER DEEP SUBSIDENCE DRYING IS NOTED ON TIME HEIGHT CROSS SECTIONS AND 12Z SOUNDINGS. I.E. 12Z JAX AND TAE SOUNDINGS WITH 1.38 AND 0.96 INCH PWATS RESPECTIVELY. BOTH WITH NLY FLOW FROM SURFACE TO ABOVE 50K FEET. .SHORT TERM...(THIS AFTERNOON THROUGH FRIDAY NIGHT) MODELS CONTINUE IN FAIRLY GOOD AGREEMENT WITH THE LOW PRESSURE SYSTEM WILL APPROACHES THE COAST TONIGHT AND MOVES IT INLAND OVER NORTHEAST FLORIDA ON THURSDAY. BECAUSE LATEST SATELLITE PIX SHOW LOW ACQUIRING SOME CHARACTERISTICS OF SUB-TROPICAL CYCLONE...NHC SENDING AN AIRCRAFT AND SYSTEM MAY BE UPGRADED TO A SUB-TROPICAL STORM ANDREA LATER THIS MORNING. ANY SIGNIFICANT IMPACTS WILL LIKELY BE FOCUSED ACROSS COASTAL COUNTIES. ANY LOCAL PRECIP DEPENDS ON WHICH MODEL WINS OUT. BOTH GFS AND NAM ARE IN GOOD AGREEMENT WITH A GRADUAL WEAKENING AND WEST/SOUTHWEST RETROGRESSION OF LOW OVER THE NEXT 72 HOURS. HOWEVER...THERE ARE SUBTLE DIFFERENCES WITH HANDLING OF LOW. THE NAM LEAVES IT OVER NORTH FLORIDA AND DRIFTS IT SLOWLY WNW INTO THE FLORIDA PANHANDLE ON FRIDAY. IT HAS MORE LOW LEVEL MOISTURE TO WORK WITH AND AS A RESULT PRODUCES SLIGHTLY HIGHER POPS FOR OUR CWA. CONVERSELY...THE GFS TRACKS A BIT FURTHER SWD... GENERALLY DUE W TODAY AND THEN SW TOMORROW. THUS IT DROPS A WEAKER LOW INTO CENTRAL FLORIDA LATE THURS WHERE IT BECOMES STATIONARY AND WEAKENS THRU FRI. THIS COULD AL CHANGE AFTER NHC ISSUES ITS UPDATE. WHICHEVER MODEL PROVES CORRECT...MEAGER RAIN CHANCES FOR CWA WITH DRY SLOT PERSISTING ACROSS ALL BUT ERN MOST CWA AND EVEN THERE MAINLY INCREASING CLOUDS WITH 10-20 PCT TODAY AND 20-30 PCT TOMORROW IN LIGHT RAIN OR SPRINKLES. COMBO OF WEAKENING UPPER TROUGH AND REMNANTS OF LOW LEVEL MOISTURE FORM SURFACE LOW MAY SQUEEZE OUT WDLY SCT SHWRS ON FRI. TEMPS WILL BE AT OR ABOVE CLIMO THROUGH THE PERIOD. && .AVIATION... ALTHOUGH ABOVE WEST ATLANTIC CYCLONE WILL CONTINUE TO DRAW CLOSER TO THE SOUTHEAST U.S. COAST LATER TODAY...WE EXPECT MOST OF THE LOW LEVEL MOISTURE TO REMAIN EAST OF OUR TAF SITES. THE ONLY TERMINAL EXPECTED TO HAVE PERIODIC CEILINGS IS KVLD...BUT EVEN THEN THE CEILINGS WILL LIKELY BE VFR. SCATTERED SHOWERS WILL DEVELOP ACROSS SOUTHEAST GA AND NORTHEAST FL THIS AFTERNOON...BUT THE PROBABILITY OF THIS RAIN AFFECTING KVLD IS TOO LOW (ABOUT 20 PERCENT) TO INCLUDE MENTION IN THE TAF. N TO NW WINDS OF 10-15 KT ARE EXPECTED AT ALL THE TERMINALS BY LATE MORNING AND AFTERNOON...WITH SOME GUSTS NEAR 25 KT. THE NORTHERLY FLOW WILL LIKELY KEEP THE SMOKE (FROM THE SOUTHEAST GA AND NORTH FL FIRES) EAST OF OUR TERMINALS...BUT IT WILL AFFECT OUR TWEB ROUTES WITH AREAS OF REDUCED VISIBILITY. && .MARINE...WINDS WILL MOSTLY BE OFFSHORE THROUGH FRIDAY THEN BACK TO THE WEST OVER THE WEEKEND. WINDS AND SEAS WILL BE BELOW SCEC CRITERIA. && .FIRE WEATHER...A RED FLAG WARNING REMAINS IN EFFECT THIS AFTERNOON/EVENING FOR ALL THE EASTERN FLORIDA PANHANDLE AND MOST OF THE WESTERN BIG BEND DUE TO A COMBINATION OF LOW RH...WINDS AND HIGH DISPERSION INDICES. NO CONCERNS FOR THE REMAINDER OF THE WORK WEEK DUE TO INCREASING LOW LEVEL MOISTURE. && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...RED FLAG WARNING THIS AFTERNOON FOR THE FOLLOWING ZONES: INLAND WALTON...HOLMES...WASHINGTON...JACKSON...BAY... CALHOUN...GULF...GADSDEN...LIBERTY...FRANKLIN...LEON AND WAKULLA. && $$ AVIATION/FIRE WX...MROCZKA PUBLIC/MARINE...BLOCK
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
1001 AM EDT WED MAY 9 2007 .SYNOPSIS... MORNING UPDATE PRODUCTS WILL BE DELAYED PENDING A CONFERENCE CALL WITH THE NATIONAL HURRICANE CENTER REGARDING THE LOW PRESSURE AREA ROTATING OFF THE GA COAST. THE NATIONAL HURRICANE CENTER CURRENTLY HAS A HURRICANE HUNTER AIRCRAFT INVESTIGATING THIS SYSTEM... CENTERED ABOUT 150 MILES EAST OF JACKSONVILLE FL. INTENSE LOW PRES CENTERED ABOUT 160 MILES SOUTHEAST OF CHARLESTON...AND 160 MILES EAST-SOUTHEAST OF SAVANNAH...WILL DRIFT TOWARD THE COAST AND WILL PRODUCE A VARIETY OF HAZARDS ACROSS COASTAL COUNTIES AND COASTAL MARINE ZONES TODAY. THIS LOW WILL ALSO PRODUCE SHOWERS AND THUNDERSTORMS ACROSS SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA...ESPECIALLY NEAR THE COAST. THE LOW WILL GRADUALLY WEAKEN NEAR THE COAST STARTING LATER TODAY...AND WILL MOST LIKELY DRIFT SOUTH OF THE REGION TONIGHT THROUGH THURSDAY. HOWEVER...THE REMNANTS OF THE LOW WILL CONTINUE TO SUPPORT A CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH THURSDAY...AND PERHAPS EVEN THROUGH THE END OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... A STRONG COASTAL STORM CONTINUES TO CHURN OFF THE GA COAST THE MRNG. ITS SATL PRESENTATION REMAINS VERY IMPRESSIVE WITH DEEP CONVECTION ROTATING CLOSER TO THE CNTR. SUSPECT THIS SYSTEM IS BECMG LESS BAROCLINIC WITH TIME ESP GIVEN ITS ORGANIZATION THIS MRNG. NHC MAY DISPATCH A RECONNAISSANCE ACFT TO INVESTIGATE THE LOW LTR TDA TO HELP DETERMINE WHETHER THE CYCLONE IS BEGINNING TO OR HAS ALREADY BECOME SUBTROPICAL. AGAIN WE WOULD LIKE TO STRESS THAT THE IMPACTS TO THE AREA WL BE THE SAME NO MATTER WHAT FORM THE LOW TAKES. REFER TO THE SPECIAL TROPICAL DISTURBANCE STATEMENT THAT WAS ISSUED BY NHC AROUND 11 PM FOR ADDITIONAL INFORMATION. NUMEROUS TO WDSPRD SHOWERS AND ISOLD TSTMS CONTINUE TO FIRE ACROSS THE COASTAL WTRS THIS MRNG. SOME OF THIS ACTIVITY HAS BRUSHED THE LWR SC COAST WHERE .5-1.0 INCHES OF RAIN HAS ALREADY FALLEN. THIS IS GOOD NEWS TO THE DROUGHT STRICKEN AREAS OF COASTAL SC WHERE MODERATE DROUGHT CONDITIONS ARE ONGOING. UNFORTUNATELY MUCH OF THIS HAS YET TO WORK ITS WAY INTO SE GA WHERE GENEROUS RAINS ARE NEEDED THE MOST. THE COASTAL LOW WL CONTINUE TO MEANDER CLOSER TO THE GA COAST TDA HELPING TO PUMP MOISTURE LADEN AIR INTO THE RGN. PWATS OFFSHORE AND N OF THE LOW ARE APRCHG 2 INCHES WHICH IS HELPING TO SUPPORT DEEP CONVECTION OVR THE WARMER GULF STREAM WTRS. AS THE LOW DRAWS CLOSER...XPCT PCPN TO GRADUALLY EXPAND IN COVERAGE ACROSS THE COASTAL WTRS AND MOVE SLOWLY INLAND AS LOW-LVL SFC MOISTURE CONVG INCRS. THE BEST CHANCES FOR SIGNIFICANT RAINS WL REMAIN CONFINED TO THE LWR SC COAST...HWVR AS THE SFC RIDGE ACROSS THE PIEDMONT CONTINUES TO ERODE WE BELIEVE SOME MUCH NEEDED RAINFALL COULD FINALLY WORK ITS WAY INTO INTERIOR AREAS OF SE GA BY LTE THIS AFTN OR THIS EVNG. WL MAINTAIN A RATHER TIGHT POP GRADIENT ACROSS THE FCST AREA TDA... WITH CATEGORICAL POPS ALONG THE SC COAST INCLUDING COLLETON- BERKELEY-DORCHESTER COUNTIES...TAPERING OFF TO 20-30 PCNT ACROSS THE FAR INTERIOR SE GA ZONES. XPCT MAX RAINFALL TOTALS OF 1-2 INCHES ALONG THE SC COAST WITH LWR AMOUNTS FARTHER SW. LCLLY HIGHER AMOUNTS ARE POSSIBLE. DO NOT XPCT WDSPRD FLOODING ATTM HWVR WITH TIDES RUNNING WELL ABV PREDICTED ANY HVY RAINS THAT FALL AROUND HIGH TIDE COULD POSE A PROBLEM...PARTICULARLY IN DOWNTOWN CHARLESTON. THERE WL BE A POTENTIAL FOR ISOLD TORNADOES/WATERSPOUTS AND LOW- TOPPED SUPERCELLS TDA AS LOW-LVL HELICITY BECOMES MAXIMIZED ALONG THE COAST AND INSTABILITY BEGINS TO WORK INLAND. WE HAVE ALREADY OBSERVED SOME ROTATION IN THE STORMS ACROSS THE COASTAL WTRS THIS MRNG. HIGHS TDA WL BE TRICKY GIVEN THE EXTENSIVE CLOUD COVER AND XPCTD RNFL. WL GO BELOW GUIDANCE FOR MOST AREAS XCPT ACROSS INTERIOR SE GA WHERE A BIT MORE SUN ERLY MAY OCCUR. XPCT HIGHS TO RANGE FROM THE LWR 70S IN THE CHARLESTON AREA TO THE UPR 70S AT METTER. STRONGEST WINDS WERE ACTUALLY OCCURRING ACROSS GA COASTAL COUNTIES THIS MORNING...GIVEN THE EXPECTED TRACK OF THE SURFACE LOW AND THE LOW LEVEL WIND FORECAST AS DEPICTED BY THE PREFERRED 0Z NAM...WILL EXTEND THE ONGOING WIND ADVISORY FOR GA COASTAL COUNTIES UNTIL NOON...WHEN THE BAND OF STRONGEST LOW LEVEL WINDS SHOULD SHIFT NORTH OF THIS AREA. MEANWHILE...THE PREFERRED 0Z NAM FORECAST SUGGESTS THAT WINDS WILL INCREASE ACROSS SC COASTAL COUNTIES AS THE SURFACE LOW DRIFTS WNW/NW...TIGHTENING THE SURFACE PRESSURE GRADIENT AND MAINTAINING A BAND OF 40-50 KT 950-850 MB WINDS ON THE NORTHERN PERIPHERY OF THE LOW THROUGH TODAY. GIVEN THIS SCENARIO...WILL EXTEND ONGOING WIND ADVISORIES FOR SC COASTAL COUNTIES UNTIL 6 PM THIS EVENING. IN FACT...THE 0Z NAM DEPICTS PERSISTING STRONG ONSHORE LOW LEVEL WINDS INTO THIS EVENING...AND THE DAY SHIFT MAY OPT TO EXTEND THE WIND ADVISORY INTO TONIGHT. ALSO...WILL MONITOR FOR THE POTENTIAL FOR INLAND WIND ADVISORIES THIS MORNING...BUT FOR NOW EXPECT PRIMARY WIND IMPACT TO REMAIN AT THE COAST. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... SFC LOW WL BE LOCATED JUST OFF THE GA COAST BY TNGT AND SLOWLY WEAKENING BUT NOT QUITE A QUICK AS WHAT THE VARIOUS MODELS ARE DEPICTING. ASSOC LOW-LVL CONVG ON THE N SIDE OF THE CIRC WL LIKELY WEAKEN WITH TIME BUT BROAD CONVG WL STILL SUPPORT AT LEAST SCATTERED TO NUMEROUS ACTIVITY FOR MUCH OF THE NGT. THE HIGHEST POPS WL KEPT IN THE CHARLESTON AREA WITH LWR POPS TO THE SW OF THERE. PCPN CHANCES WL CONTINUE TO DIMINISH INTO THU AS THE SFC LOW MENDERS VERY NEAR TO THE GA COAST HWVR AT LEAST SCATTERED ACTIVITY IS STILL XPCTD. LOWS TNGT WL RANGE FROM AROUND 60 WELL INLAND TO THE LWR-MID 60S NEAR THE COAST. HIGHS THU WL RANGE FROM THE MID-UPR 70S IN THE CHARLESTON AREA TO THE LWR 80S ACROSS INTERIOR SE GA. && .LONG TERM /FRIDAY THROUGH TUESDAY/... ATLC HIGH PRES BEGINS TO BUILD BACK INTO THE AREA ON FRI...WITH POSSIBILITY OF A FRONT APPROACHING FROM THE N OVER THE WEEKEND. HIGH PRES WOULD THEN BUILD BEHIND THIS FRONT FOR EARLY NEXT WEEK. SEA BREEZE LOOKS TO BE DRIVING FORCE FOR ANY PRECIP CHANCES ON FRI...AND WILL GO WITH SMALL POPS INLAND ALONG WITH WARMING TEMPS THROUGH THE 80S. CHANCE POPS AHEAD OF THE FRONT FOR THE WEEKEND...WITH SLIGHT CHANCE POPS EARLY NEXT WEEK WITH UNCERTAINTY ABOUT FUTURE MOVEMENT OF THE AFOREMENTIONED FRONT. TEMPS TO REMAIN NEAR OR ABOVE NORMAL SAT INTO EARLY NEXT WEEK. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... CIGS WILL VARY FROM MVFR TO IFR AS SHOWERS IMPACT BOTH TERMINALS TODAY...AND HEAVIER SHOWERS WILL BE CAPABLE OF PRODUCING IFR VISIBILITIES. COVERAGE OF SHOWERS...WHICH WILL INCREASE AROUND BOTH TERMINALS TODAY...MAY DIMINISH SOMEWHAT TONIGHT AS THE SURFACE LOW WEAKENS JUST OFFSHORE. HOWEVER...LOW LEVEL MOISTURE WILL SUPPORT MVFR/IFR CIGS AND VISIBILITIES OVERNIGHT. MEANWHILE...PER LOW LEVEL WINDS MEASURED BY THE 12Z KCHS RAOB...EXPECT LLWS AT BOTH TERMINALS THIS MORNING...WITH GUSTY N/NE WINDS CONTINUING THROUGH THE DAY. WINDS MAY DIMINISH OVERNIGHT...MOST MARKEDLY AT KSAV. EXTENDED AVIATION OUTLOOK...OCNL IFR/MVFR CONDITIONS PSBL THU WITH SCATTERED CONVECTION. OTRW NO ISSUES. && .MARINE... AS EXPECTED...WINDS ACROSS GA COASTAL WATERS WERE DIMINISHING...MOST SIGNIFICANTLY ACROSS THE OUTER GA WATERS... WHILE WINDS WERE MAINTAINING INTENSITY ACROSS SC WATERS...AROUND GALE FORCE. GIVEN THE PREFERRED 00Z-06Z NAM FORECASTS FOR THE SURFACE LOW TRACK...AND GIVEN THE FACT THE CENTRAL PRESSURE IN THE LOW WILL WILL REMAIN A FEW MB BELOW THE MODEL FORECAST TODAY...EXPECT ONGOING GALES TO DIMINISH ACROSS GA WATERS BY LATER THIS MORNING...THEN...WINDS WILL CONTINUE DIMINISH THIS AFTERNOON ACROSS GA WATERS AS THE CENTER OF THE LOW PUSHES INTO THIS AREA...WITH A DOWNGRADE TO SCAS POSSIBLE MAINLY FOR ONGOING HIGH SEAS. FARTHER NORTH ACROSS SC WATERS NORTH OF THE SURFACE LOW...THE 00Z-06Z NAM SCENARIO...WHICH MAINTAINS A TIGHTER ONSHORE SURFACE PRESSURE GRADIENT AND A BAND OF E/NE WINDS 40-50 KT IN THE 950-850 MB LAYER THROUGH THIS AFTERNOON...JUSTIFIES AN CONTINUATION OF ONGOING GALE WARNINGS FOR SC NEARSHORE WATERS...INCLUDING CHARLESTON HARBOR...UNTIL 6 PM THIS EVENING. IF THE LOW WEAKENS MORE SLOWLY THAN EXPECTED...THE DAY SHIFT MAY NEED TO EXTEND THESE HEADLINES INTO TONIGHT. MEANWHILE...WAVE WATCH GUIDANCE IS A BIT UNDERDONE WITH SEAS ACROSS COASTAL WATERS...RECENT REPORTS INCLUDE 11 TO 12 FT AT BUOY 41004...11 TO 12 FT AT TOWER R2 AND 8 TO 9 FT AT GRAYS REEF BUOY. HOWEVER...THE GUIDANCE WAS REASONABLE AND WAS ADJUSTED UPWARD ONLY A FOOT OR TWO ACROSS ALL WATERS THIS AM AND ACROSS SC WATERS THIS AFTERNOON/TONIGHT...TO ACCOUNT FOR THE DEEPER THAN PROGGED SURFACE LOW. && .TIDES/COASTAL FLOODING... WILL CONTINUE TO ISSUE SPECIAL TIDE AND LOCAL STORM REPORTS AS NEEDED. EXPECT HIGH SURF TO CONTINUE ALONG THE SC/GA COASTS THROUGH TODAY...AND...GIVEN THE 0Z NAM FORECAST...THE DAY SHIFT MAY OPT TO EXTEND THE HIGH SURF ADVISORY FOR THE SC COAST INTO TONIGHT. MEANWHILE...RECENT OBSERVATIONS INDICATE THAT THE TIDE IN CHS HARBOR IS RUNNING ABOUT 2.25 FT ABOVE PREDICTED LEVELS... WHILE THE FORT PULASKI TIDE WAS RUNNING AROUND 3 FT ABOVE THE PREDICTED LEVEL. THE PREDICTED LEVEL OF THE NEXT HIGH TIDE EARLY THIS AFTERNOON IS LOWER THAN THE OVERNIGHT HIGH TIDE...4.6 FT AT CHS HARBOR...HOWEVER...THE ONSHORE COMPONENT WITHIN THE BAND OF STRONGEST WINDS NORTH OF THE SURFACE LOW MAY PUSH TIDES 2-3 FT ABOVE THIS LEVEL...POSSIBLY SUFFICIENT TO PRODUCE SHALLOW COASTAL FLOODING EARLY THIS AFTERNOON ALONG THE SC COAST...AND THIS POTENTIAL IS COVERED IN THE LATEST COASTAL HAZARD MESSAGE. IF THE LOW WEAKENS MORE SLOWLY THAN EXPECTED...MAINTAINING A STRONGER ONSHORE FLOW...AT LEAST SHALLOW COASTAL FLOODING COULD OCCUR ALONG THE SC COAST AROUND THE TIME OF HIGH TIDE TONIGHT...213 AM AT CHS HARBOR. WILL MENTION THIS POTENTIAL WITHIN THE COASTAL HAZARD MESSAGE...HOWEVER...UNCERTAINTY CONCERNING THE POSITION AND RATE OF DECAY OF THE SURFACE LOW PRECLUDES ANY HEADLINES FOR THE SECOND FORECAST PERIOD. && .LAKE WINDS.. WILL CONTINUE THE ONGOING LAKE WIND ADVISORY FOR LAKE MOULTRIE THROUGH TONIGHT...AS SUSTAINED WINDS AT LEAST 20 KNOTS WILL REMAIN COMMON. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...HIGH SURF ADVISORY UNTIL 6 PM EDT THIS AFTERNOON FOR GAZ117- 119-139-141. WIND ADVISORY UNTIL NOON EDT TODAY FOR GAZ117-119-139-141. SC...HIGH SURF ADVISORY UNTIL 6 PM EDT THIS AFTERNOON FOR SCZ048>051. LAKE WIND ADVISORY UNTIL 6 AM EDT THURSDAY FOR SCZ045. WIND ADVISORY UNTIL 6 PM EDT THIS AFTERNOON FOR SCZ048>051. MARINE...GALE WARNING UNTIL 6 PM EDT THIS AFTERNOON FOR AMZ330-350-352. GALE WARNING UNTIL NOON EDT TODAY FOR AMZ354-374. && $$ JPC
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1103 AM EDT WED MAY 9 2007 .UPDATE... TWO AREAS OF RAIN FALLING ATTM OVR UPR MI AS COMPACT UPPER LEVEL LOW SLIDES ACROSS NORTHERN WI. LEADING SHIELD OF SHOWERS PRODUCED BY THETA-E ADVECTION AHEAD OF UPR LOW IS GRINDING INTO DRIER AIR OVR FAR EASTERN UPR MI. STILL...WITHIN THE BAND TOTAL RAIN AMOUNTS NEARING AN INCH ARE COMMON. THE SECOND BATCH OF SHOWERS IS NEARLY STATIONARY OVR NCNTRL WI INTO IRON/GOGEBIC/HOUGHTON/BARAGA COUNTIES. THIS RAIN IS TIED TO UPPER LOW CENTER. DRY SLOT IN BTWN HAS SHUT DOWN THE EARLIER SHOWERS FM MARQUETTE INTO DELTA COUNTIES. SHOULD SEE SOME EASTWARD DRIFT TO BOTH AREAS OF SHOWERS THROUGH THE AFTN AS UPPER LOW PRESSES EAST INTO NORTHERN LOWER MI BY EVENING. HAVE NOT SEEN ANY THUNDER SINCE 12Z...ABOUT 3 HOURS NOW. HOWEVER...SOME BREAKS IN CLOUDS AHEAD OF SECOND SHOWER AREA MAY ALLOW SURFACE BASED INSTABILITY TO INCREASE. NAM12 MIXED LAYER CAPE VALUES OF A FEW HUNDRED J/KG ARE PROGGED...FOCUSED MOSTLY OVR SCNTRL UPR MI THIS AFTN. KEPT IN ISOLD THUNDER MENTION CENTRAL AND EAST. SKIES CLEARING IN FAR WEST CWA AS VERY DRY AIR SEEN ON CYQT 12Z TAMDAR SOUNDING SURGES INTO WESTERN LK SUPERIOR AND ADJACENT PORTIONS OF UPR MI. THIS DRYING TREND SHOULD TRANSLATE INTO CENTRAL UPR MI BY LATE AFTN...THEN INTO EASTERN CWA EARLY THIS EVENING. CLOUD COVER AND PCPN WILL HOLD DOWN TEMPS FM MQT AND ESC EAST...ESPECIALLY NEAR LK MI. LOWERED TEMPS A FEW DEGREES FM PREV FCST THERE. HOWEVER...MIXING HEIGHTS TO 800MB AND H85 TEMPS NEAR 10C SPREADING INTO WEST CWA SUPPORT MAX TEMPS WELL INTO THE 70S ONCE SUN APPEARS THIS AFTN. && .PREV DISCUSSION (452 AM EDT)... UPPER AIR PATTERN CONSISTS OF A CLOSED 500 MB LOW OVER SOUTHERN MN WITH AN ASSOCIATED TROUGH AND A CLOSED 500 MB LOW OVER NORTHERN NEW MEXICO AND A STRONG CLOSED 500 MB LOW OFF THE SE COAST. THERE IS ALSO RIDGING ALONG THE GULF COAST AND INTO THE APPALACHIANS AND ALSO ACROSS THE NORTHERN ROCKIES. THE 500 MB FLOW PATTERN ACROSS SOUTHERN CANADA IS MOSTLY ZONAL. NAM SHOWING THE UPPER LOW AND ATTENDANT TROUGH ACROSS SOUTHERN MN CONTINUING TO HEAD EAST TODAY WITH THE CLOSED 500 MB LOW IN NORTHERN LOWER MICHIGAN 00Z TONIGHT. AFTER THIS TROUGH HEADS EAST...MORE SHORTWAVE ENERGY PASSES BY TO THE NORTH THU NIGHT WITH ANOTHER SHORTWAVE AFFECTING THE AREA FRI NIGHT. NAM SHOWING 1000-500 MB THICKNESS PACKING SUGGESTS A STRONG COLD FRONT ON THE DOORSTEP OF THE U.P. THU NIGHT WHICH HEADS SOUTH IS ACROSS NORTHERN LOWER MICHIGAN FRI MORNING. NAM SHOWING SOME 850-500 MB Q-VECTOR CONVERGENCE HEADING EAST THIS MORNING ALONG WITH SOME DEEPER MOISTURE CROSSING THE SOUTHERN CWA...SO CHANCE POPS FOR PCPN IS WARRANTED ACROSS THE SOUTHERN CWA. MOISTURE AND DYNAMICS HEAD EAST AND OUT OF THE CWA BY THIS EVENING AND THEY BOTH CLIP THE SOUTHERN CWA. MORE MOISTURE AND DYNAMICS COME IN FOR THU AFTERNOON AND NIGHT WITH THE COLD FRONT. NAM IS NOT PRODUCING QPF THOUGH AS MOISTURE IS LIMITED WITH THE FRONT. GFS SIMILAR TO THE NAM WITH THE LOW AND TROUGH HEADING EAST TODAY AND SIMILAR FOR THE WHOLE FORECAST AND WILL USE A BLEND OF THE TWO MODELS FOR THIS FORECAST. SHIFT GOT A LOT MORE INTERESTING THIS MORNING AS THE UPPER LOW TOOK OFF AND PRODUCED SOME THUNDERSTORMS AND WIDESPREAD RAINFALL. SEEMS LIKE THE GFS WAS ADVERTISING THIS A FEW DAYS AGO...BUT WAS THE OUTLIER SOLUTION AT THE TIME. ANYWAY...HAD TO DO SOME MAJOR UPDATING TO THE SHORT-TERM GRIDS. MOISTURE SEEMS TO BE MORE ABUNDANT THAN PREVIOUSLY THOUGHT AND COVERAGE OF PCPN HAS BEEN EXPANDING WITH COOLING CLOUD TOPS ON IR. WILL GO LIKELY POPS FOR THE SOUTH AND EAST FOR TODAY AS DYNAMICS ARE STRONGEST THERE ALONG WITH BETTER MOISTURE. NORTH AND WEST WILL KEEP CHANCE POPS THERE AS MOISTURE IS LESS. THREW IN SOME ISOLATED THUNDERSTORMS BASED ON NAM AND GFS BOTH SHOWING SOME ELEVATED CAPE VALUES OF LESS THAN 1000 J/KG AND PLENTY OF LIGHTNING HAS BEEN BREAKING OUT WITH THIS LOW THIS MORNING. THE ELEVATED MOST UNSTABLE CAPE REMAINS OVER THE ERN CWA THROUGH THIS AFTERNOON BEFORE MOISTURE AND DYNAMICS DEPART. BECAUSE OF THE CONVECTION AND CLOUD COVER...LOWERED GOING HIGHS A BIT TODAY EXCEPT IN THE FAR WEST WHERE SUNSHINE WILL BREAK OUT. WENT CLOSE TO ADJMVR FOR LOWS AND HIGHS TONIGHT ONWARD. LOOKED AT 850 MB TEMPERATURES AND MIXED THEM TO THE SFC FOR HIGHS AND THIS HAS WORKED WELL LATELY. DID LOWER HIGHS FOR FRI WITH COLD FRONT ALREADY THROUGH AND SIGNIFICANTLY COLDER AIR WILL BE MOVING THROUGH THE AREA. KEPT IN SLIGHT CHANCE POPS THU EVENING AS THE STRONG COLD FRONT MOVES THROUGH THE AREA. OTHER THAN THAT...DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...JLA PREV DISCUSSION...MICHELS
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
200 PM PDT WED MAY 9 2007 .SYNOPSIS... WEAKENING HIGH PRESSURE ALOFT AND A LOW PRESSURE TROUGH PASSING BY TO THE NORTH WILL BRING A COOLING TREND THURSDAY THROUGH THE WEEKEND...AND A RETURN OF MARINE LAYER CLOUDS AND FOG TO AREAS WEST OF THE MOUNTAINS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES. TEMPERATURES BEGAN A GRADUAL DECREASE TODAY THAT WILL CONTINUE INTO THE WEEKEND. COASTAL AREAS WILL SEE THE LARGEST COOLING EFFECTS AS MARINE LAYER MOISTURE RETURNS. SATELLITE IMAGERY SHOWS AREAS OF MARINE LAYER STRATUS AND FOG OVER THE COASTAL WATERS. IT COULD MOVE ASHORE AS EARLY AS THIS AFTERNOON AND DEEPEN OVERNIGHT. THE RESULTING LOWER TEMPS AND HUMIDITY INCREASE WILL BENEFIT FIREFIGHTERS OVER THE NEXT FEW DAYS. THE DEPTH AT WHICH THE MARINE LAYER FORMS TONIGHT WILL BE CRITICAL IN DETERMINING THE EXTENT OF FOG...POSSIBLY DENSE FOG...IN THE COASTAL ZONES EARLY THURSDAY. INDICATIONS ARE THAT FOG IS MOST LIKELY TO MOVE INTO THE COASTAL AREAS TONIGHT...THEN LIFT OVERNIGHT BUT REMAIN IN THE INLAND VALLEYS AND MESAS IN SAN DIEGO COUNTY UNTIL THURSDAY MORNING. FARTHER INLAND THE AIRMASS HAS YET TO BE SIGNIFICANTLY MODIFIED BY THE MARINE LAYER AS INLAND VALLEY DEWPOINTS HAVE INCREASED ONLY A FEW DEGREES. THESE INLAND VALLEYS WILL CONTINUE TO BE VERY WARM...BUT THE AFTERNOON ONSHORE BREEZE AND SLIGHTLY LOWER 850 MB TEMPS WILL BRING A FEW DEGREES OF COOLING. SOME LOCATIONS WILL STILL REACH THE 90S THOUGH...ESPECIALLY IN THE INLAND EMPIRE. TEMPS IN THE MOUNTAINS AND DESERTS COULD ALSO BE A FEW DEGREES COOLER AS WESTERLY FLOW ALOFT DEVELOPS...BUT HUMIDITIES WILL REMAIN LOW. LONG TERM...MODELS TRENDS REMAIN CONSISTENT WITH THE COLLAPSE OF THE UPPER RIDGE OVER THE SOUTHWEST TONIGHT AND THURSDAY...GIVING WAY TO SOUTHWEST FLOW AHEAD OF RELATIVELY WEAK EASTERN PACIFIC TROUGHING. HEIGHTS SLOWLY LOWER THROUGH SUNDAY FOR GRADUAL COOLING AND A GRADUAL DEEPENING OF THE MARINE LAYER. && .AVIATION... 091900Z...ACARS SOUNDINGS INDICATE THE MARINE LAYER DEPTH REMAINS AT OR BELOW ABOUT 500 FEET MSL THIS AFTERNOON. MARINE LAYER STRATUS/FOG OVER THE COASTAL WATERS CONTINUES TO APPROACH THE COAST AND SHOULD MOVE ONTO THE COAST DURING THE AFTERNOON AND SHOULD MOVE OVER THE MESAS AND SOME INLAND VALLEY AREAS OVERNIGHT. TIMING WILL BE THE MAIN PROBLEM BUT SOME LIFR CONDITIONS COULD MOVE INTO THE VICINITY OF THE COASTAL AIRPORTS IF NOT OVER THE COASTAL AIRPORTS EARLY THIS EVENING. THE STRATUS/FOG SHOULD SLOWLY LIFT THROUGH THE EVENING AS THE MARINE LAYER DEEPENS TO AROUND 1200 FEET OVERNIGHT IN RESPONSE TO THE RETURN OF THE ONSHORE FLOW AND A COASTAL EDDY DEVELOPMENT. STRATUS/FOG SHOULD CLEAR BACK TO THE COASTLINE BETWEEN 16 AND 18Z ON THURSDAY. STRATUS/FOG IS NOT EXPECTED TO REACH THE INLAND EMPIRE AREA NEAR KONT TONIGHT BUT SOME VISIBILITY RESTRICTION FROM HAZE OR SMOKE FROM NEARBY WILDFIRES COULD IMPACT KONT BEFORE SUNRISE ON THURSDAY. ABOVE THE MARINE LAYER...CONTINUED CLEAR WITH UNRESTRICTED VISIBILITIES THROUGH THURSDAY. && .SGX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ PUBLIC...PG AVIATION...HORTON