AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 810 PM EDT SUN SEP 3 2006 .SYNOPSIS... 00Z WATER VAPOR AND RUC ANALYSIS SHOWS A PATTERN THAT HAS CHANGED LITTLE ACROSS NORTH AMERICA DURING THE PAST 24 HOURS. MAIN FEATURES CONTINUE TO BE DUAL UPPER LOW FEATURES TO OUR NORTH. ONE LIFTING NORTH INTO EASTER ONTARIO AND WESTERN QUEBEC AND A STRONGER MORE PROMINENT UPPER LOW CENTERED OVER WESTERN IOWA. FURTHER TO THE WEST THE UPPER RIDGE CONTINUES TO DOMINATE THE WEST COAST AND INTERMOUNTAIN WEST. A LITTLE CLOSER TO HOME...AN EAST WEST UPPER RIDGE IS ANALYZED FROM SOUTHERN TEXAS ACROSS THE NORTHERN AND WESTERN GULF OF MEXICO. THIS RIDGE IS BEGINNING TO BE ERODED ON ITS EASTERN SIDE AS LARGE ILL-DEFINED UPPER LOW FEATURES ROTATES SLOWLY WEST FROM THE BAHAMAS TOWARD THE FLORIDA PENINSULA. AT THE SURFACE...WEAK FRONTAL BOUNDARY OR SURFACE TROUGH CONTINUES TO BE ANALYZED JUST TO THE NORTH AND WEST OF THE FORECAST AREA ACROSS CENTRAL GA/AL. THE LOCATION OF THIS FEATURE IS FAIRLY EASY TO PICK OUT ON EVENING VISIBLE IMAGE AS SCT/NMRS SHOWERS AND THUNDERSTORMS HAVE DEVELOPED ALONG AND JUST TO THE NORTH OF THE BOUNDARY WITH RAPIDLY CLEARING SKIES AND JUST A FEW ISOLATED SHOWERS TO THE SOUTH ACROSS OUR AREA. EXCELLENT LATE SUMMER MIXING THIS AFTERNOON ONCE AGAIN WAS ABLE TO TAP INTO DRY MID-LEVEL AIR AND ALLOW DEWPOINTS TO FALL INTO THE LOWER AND MIDDLE 60S ACROSS A GOOD PORTION OF THE AREA (AWAY FROM THE COAST). THE LACK OF CONVECTION AND GOOD MIXING ALSO ALLOWED TEMPERATURES TO RISE INTO THE LOWER AND MIDDLE 90S AT MOST LOCATIONS. TALLAHASSEE AIRPORT REACHED A HIGH TEMPERATURES OF 95 DEGREES WHICH IS 5 F ABOVE AVERAGE AND ONLY 3 F SHORT OF THE RECORD HIGH FOR THE DATE. DRY MID-LEVEL AIR AND WEAK SUBSIDENCE CAPPING INVERSION AROUND 725MB WAS ENOUGH TO ONCE AGAIN KEEP CONVECTION ISOLATED IN NATURE ACROSS THE FORECAST AREA. JUST A FEW SHOWERS DEVELOPING THIS EVENING... MAINLY ALONG AND JUST BEHIND THE SEA-BREEZE BOUNDARY ACROSS THE INLAND BIG BEND COUNTIES...AND ALSO A FEW SHOWERS CLOSER TO THE MID-LEVEL MOISTURE BOUNDARY ACROSS OUR EASTERN GA COUNTIES. && .SHORT TERM (TONIGHT & MONDAY)... THE FEW LINGERING SHOWER LEFT OVER ACROSS THE INLAND BIG BEND REGION AND ACROSS SOUTH CENTRAL GEORGIA SHOULD RAPIDLY DIMINISH INTO THE LATE EVENING HOURS WITH PARTLY TO MOSTLY CLEAR SKIES PREVAILING ACROSS THE FORECAST AREA. DENSE FOG SHOULD NOT BE MUCH OF A CONCERN DURING THE OVERNIGHT HOURS...BUT A FEW LOCATIONS ARE LIKELY TO SEE SOME LOWERED VISIBILITIES...ESPECIALLY LOW LYING AREA AND THOSE LOCATIONS THAT WERE ABLE TO PICK UP A QUICK SHOWER THIS AFTERNOON OR EVENING. WEAK BOUNDARY TO OUR NORTH AND WEST IS EXPECTED TO REMAIN PRETTY MUCH IS PLACE INTO THE DAY ON MONDAY. AN INCREASE IN MID-LEVEL MOISTURE IS FORECAST TO APPROACH THE EASTERN BIG BEND SOUTH-CENTRAL GA COUNTIES BY LATER IN THE AFTERNOON. GUIDANCE IS HAVING A HARD TIME AGREEING ON JUST HOW MUCH WESTWARD PROGRESSION THIS MOISTURE WILL HAVE DURING THE DAY. THE DRY AIR LOOKS TO WIN OUT ONCE AGAIN FROM TALLAHASSEE TO ALBANY AND WESTWARD AND SEE NO REASON TO CHANCE THE SLIGHT CHANCE 20 POPS GOING ACROSS THIS REGION. SLIGHTLY BETTER CHANCES FOR RAIN WILL ONCE AGAIN BE FOUND ACROSS THE EAST WERE A LOW CHANCE 30 POP WILL CONTINUE. THE LACK OF CONVECTION WILL ONCE AGAIN ALLOW AREAS AWAY FROM THE COAST TO REACH THE LOWER TO MIDDLE 90S DURING THE AFTERNOON AND EARLY EVENING. && .MARINE... EVENING MARINE OBSERVATIONS ARE SHOWING VARIABLE LIGHT WINDS GENERALLY AROUND 5 KNOTS ACROSS THE OFFSHORE WATERS...WITH ONSHORE FLOW BETWEEN 5 AND 10 KNOTS CLOSER TO THE COAST. LOOK FOR THESE WINDS ACROSS THE COASTAL WATERS TO SWING AROUND TO THE NORTHWEST OR NORTH DURING THE OVERNIGHT HOURS. A WEAK AREA OF HIGH PRESSURE WILL BUILD AND REMAIN OVER THE COASTAL WATERS UNTIL TUESDAY WHEN A WEAK COLD FRONT WILL APPROACH THE MARINE AREA FROM THE NORTHWEST. THIS FRONT WILL MOVE THROUGH THE COASTAL WATERS ON WEDNESDAY BRINGING A CHANCE FOR SHOWERS AND THUNDERSTORMS BUT CAUSING LITTLE INCREASE IN WINDS AND SEAS. HIGH PRESSURE WILL BUILD BACK OVER THE WATERS LATE THURSDAY AND HOLD IN PLACE INTO THE WEEKEND. && .AVIATION... FEW LEFTOVER SHOWERS ACROSS THE AREA ARE SHOWING A RAPID WEAKENING TREND THIS EVENING. LOOKING FOR VFR CONDITIONS TO PREVAIL THROUGH MIDNIGHT. DID ALLOW FOR MVFR VISIBILITIES TO DEVELOP AT ALL TERMINALS WITH THE EXCEPTION OF KPFN DURING THE EARLY MORNING HOURS. THE SYNOPTIC SITUATION IS FAIRLY SIMILAR TO THE WHAT WAS OBSERVED LAST NIGHT AND WEIGHTED MORNING VIS/CEIL RESTRICTIONS HEAVILY ON PERSISTENCE. EVEN STILL WILL NOT BE SHOCKED TO SEE EITHER KABY OR KVLD GO DOWN TO IFR VIS AND PERHAPS CEILINGS FOR A SHORT TIME AROUND SUNRISE. LOCAL HIGH RESOLUTION GUIDANCE HAS BEEN HINTING AT THIS OCCURRING...BUT WILL JUST LOWER THESE LOCATIONS DOWN TO LOW MVFR CONDITIONS AT THIS TIME. && .FIRE WX... CERTAINLY SAW SOME OF THE DRIES AIR IN SEVERAL WEEKS ACROSS THE INLAND PORTIONS OF THE FORECAST AREA THIS PAST AFTERNOON. IT TOOK TO VERY LATE IN THE AFTERNOON AND EARLY EVENING...BUT RH VALUES IN THE 30S WERE OBSERVED IN QUITE A FEW LOCATIONS...AS DRIER MID-LEVEL AIR MIXING DOWN INTO THE LOWER LEVELS COMBINED WITH HIGH TEMPERATURES IN THE LOWER TO MIDDLE 90S. SOME FAIRLY LOW RH VALUES IN THE UPPER 30S TO LOWER 40S ARE ONCE AGAIN POSSIBLE FOR INLAND PORTIONS OF THE FLORIDA PANHANDLE AND SOUTHEAST ALABAMA MONDAY AFTERNOON. HOWEVER...THE EXTENT OF THE DRIER AIR DOES NOT LOOK TO BE A SIGNIFICANT AS WAS OBSERVED THIS PAST AFTERNOON. THEREFORE NOT RED FLAG CONDITIONS ARE ANTICIPATED...BUT WILL HAVE TO KEEP AN EYE ON THE SITUATION AND WILL LET THE OVERNIGHT SHIFT RE-EVALUATE. && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...NONE. && $$ MROCZKA fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 1034 AM CDT SUN SEP 3 2006 .DISCUSSION... 15Z SURFACE ANALYSIS SHOWS A WEAKENING FRONTAL BOUNDARY ACCOMPANIED BY A BAND OF CLOUDS AND SHOWERS JUST WEST OF THE MISSISSIPPI RIVER. CUT-OFF UPPER LOW CONTINUES TO SPIN OVER THE DAKOTAS...PROVIDING VERY LITTLE EASTWARD PUSH FOR THE FRONT. RADAR LOOPS INDICATE PRECIP IS GENERALLY MOVING IN A N/NE DIRECTION...AND IS MAKING ONLY SLOW PROGRESS EASTWARD TOWARD ILLINOIS. 12Z KILX SOUNDING SHOWS A GOOD DEAL OF DRY AIR ALOFT...SO PRECIP SHOULD HAVE A HARD TIME MAKING IT TOO FAR EAST INTO CENTRAL ILLINOIS LATER TODAY. BOTH 12Z RUC AND NAM-WRF INDICATE LIGHT QPF MAKING IT AS FAR EAST AS THE ILLINOIS RIVER BEFORE 00Z MON. BASED ON CURRENT TRENDS...AND MOISTENING ENVIRONMENT AS INDICATED BY 12Z KDVN SOUNDING...THIS SCENARIO SEEMS REASONABLE. WILL UPDATE POP GRIDS TO INCREASE POPS TO 50 ACROSS THE FAR W/NW CWA...QUICKLY TAPERING TO JUST 20 ALONG THE I-55 CORRIDOR...WITH NO CHANCE OF RAIN FURTHER EAST AND SOUTH. CURRENT TEMPS HAVE RISEN INTO THE UPPER 60S AND LOWER 70S...AND WILL HAVE NO TROUBLE REACHING PROJECTED AFTERNOON HIGHS...SO NO FURTHER UPDATES ARE NEEDED AT THIS TIME. && .PREV DISCUSSION... MAIN FORECAST CONCERN THIS PACKAGE IS WITH TIMING AND COVERAGE OF PRECIP BEGINNING THIS EVENING AND INTO TUESDAY. SHORT TERM...TODAY THROUGH TUESDAY... UPPER LOW OVER EASTERN SOUTH DAKOTA AND ATTENDANT COLD FRONT CONTINUE TO MAKE THEIR SLOW PROGRESSION EASTWARD THIS MORNING. A NARROW PREFRONTAL BAND OF PRECIP IS JUST NOW MAKING IT INTO THE EASTERN THIRD OF IOWA. COLD FRONT SHOULD JUST BARELY MAKE IT TO THE MISSISSIPPI RIVER BY LATE THIS AFTERNOON. EXPECT SOME CONVECTION MAY FIRE UP JUST OUT AHEAD OF IT... STILL IN A FAIRLY NARROW BAND AS SEEN YESTERDAY ACROSS IOWA. FRONT IS WEAK AND SLOW MOVING... SO LOW LEVEL CONVERGENCE IS LACKING. BEST REGION FOR LARGE SCALE LIFT WILL BE IN LFQ OF 100 KT UPPER JET NOSING INTO ILLINOIS... AND MID LEVEL DEFORMATION/DIVERGENCE AXIS BETWEEN OUR UPPER LOW AND THE UPPER LOW OVER EASTERN ONTARIO. THIS PREFERRED REGION FOR LIFT LOOKS TO SET UP ACROSS SOUTHERN WISC/NORTHEAST IA/FAR NORTHERN IL BY THIS AFTERNOON. WILL GO AHEAD WITH A CHANCE POP IN THE FAR NE CORNER OF THE CWA FOR THIS AFTERNOON CONSIDERING PROXIMITY TO PREFERRED LIFT REGION. FRONT WILL SLOWLY MOVE ACROSS THE AREA SUNDAY EVENING AND THROUGH THE DAY MONDAY. MAIN QUESTION ON MONDAY IS WHETHER OR NOT THERE WILL BE DRY SLOTTING ACROSS THE WESTERN CWA BEHIND THE COLD FRONT... AND AHEAD OF THE MID LEVEL COLD POOL ASSOCIATED WITH THE UPPER LOW. NAM INDICATES LACK OF QPF ACROSS THE WEST MONDAY AFTERNOON... WITH COLD POOL PRECIP MAINLY BACK ACROSS IOWA. CONSIDERING PERFORMANCE ISSUES WITH THE NEW NAM-WRF SINCE ITS DEBUT... NOT WILLING TO TOTALLY BUY INTO SUCH FINE SCALE DETAILS THIS FAR OUT. WILL STILL KEEP HIGHEST POPS FOCUSED ACROSS NORTHWEST CWA... CLOSER TO UPPER LOW POSITION. UPPER LOW SHOULD BE OVER THE TOP OF US COME TUESDAY ACCORDING TO GFS/UKMET. NAM ATTEMPTS TO DROP UPPER LOW RATHER FAR SOUTH WHICH SEEMS UNLIKELY GIVEN POSITION OF KICKER TROUGH ACROSS ONTARIO WHICH WILL EVENTUALLY ABSORB THE CUT OFF LOW. CONTINUE TO FOCUS POPS ACROSS THE NORTH... AND INDICATE DIURNAL TREND TO PRECIP COVERAGE. LONG TERM...WEDNESDAY THROUGH SATURDAY... LITTLE CONCERNED ABOUT SLIGHT CHANCE FOR PRECIP WEDNESDAY AS BROAD TROUGH STAYS ACROSS THE MIDWESTERN STATES. BEYOND THAT... WEAK HIGH PRESSURE BUILDS IN FOR THURSDAY... WHILE A BACK DOOR FRONT MAY ATTEMPT TO PRESS IN FROM THE NORTH FRIDAY. MODEL CONSENSUS STILL KEEPS THIS OFF TO THE NORTH. NEXT SIGNIFICANT CHANCE FOR PRECIP MAY COME JUST IN TIME FOR THE WEEKEND AS ANOTHER WAVE EJECTS FROM THE GREAT PLAINS. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ BARNES/HARDIMAN il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 240 PM EDT SUN SEP 3 2006 .SHORT TERM (TONIGHT-LABOR DAY) MODELS ESPECIALLY GFS AND RUC40 SHOW LIGHT SHOWERS BREAKING OUT OVER THE SHEN VALLEY TONIGHT AS WEAK WARM ADVECTION DEVELOPS ALONG/NORTH OF A WEAK H85 BDRY STALLED JUST SOUTH OF THE AREA. HPC QPF GRAPHICS SOME LIGHT PRECIP OVR THE NRN PIEDMONT AND LOWER SRN MD. NOT VERY CONFIDENT ABT SCENARIO SUGGEST MODELS AS SFC AND UPPER LVL FEATURES QUITE WEAK. WILL KEEP FCST DRY FOR TONIGHT WITH REDEVELOPMENT OF LOW CLOUDS. LABOR DAY...SWRLY MID LVL FLOW INCREASES BETWEEN APPROACHING UPPER LOW FROM THE MIDWEST AND SUBTROPICAL RIDGE NORTH OF THE BAHAMAS. THIS WILL HELP INCREASE MOISTURE OVER THE REGION. MODELS ALL IN GENERAL AGREEMENT IN BREAKING OUT PRECIP OVR THE SRN APPALACHIANS EARLY IN THE DAY THEN SPREADING SLOWLY TO THE NE AS THE DAY PROGRESSES. BASED ON 12Z GFS ENSEMBLE MEAN THINK ONLY THE SRN SHEN VALLEY HAS A CHANCE OF SEEING ANY RAIN BEFORE 8PM. && .AVIATION...P6SM BKN-OVC040 THRU THE PERIOD. && .MARINE..LIGHT AND VARIABLE WINDS. DEPENDING ON THE POSITION OF THE WARM FRONT TUESDAY...WINDS MAY REACH 15 KNOTS OR EVEN INTO SMALL CRAFT CRITERIA DURING THE AFTERNOON. 12Z GFS BUFKIT FORECAST SOUNDINGS INDICATE GUST POTENTIAL NEAR 20KTS AT KNHK. && .LONG TERM (MONDAY NIGHT THROUGH SUNDAY)... OBSERVATIONS... 500MB HEIGHT/ANOMALY PATTERN DURING THE PAST 5 DAYS INDICATES A LOW AMPLITUDE PROGRESSIVE PATTERN CENTERED ACROSS THE NORTHERN PACIFIC AND CANADIAN BORDER HAS AMPLIFIED TO A BLOCKED PACIFIC PATTERN WITH THE MEAN FLOW LIFTING NORTH INTO CENTRAL CANADA. WATER VAPOR SHOWS AN UPPER LOW ACROSS THE CENTRAL CONUS...WITH A SHEAR AXIS FROM LAKE WINNIPEG NORTHEAST THROUGH THE JAMES BAY. THE UPPER LEVEL REMNANTS OF ERNESTO ARE MOVING NORTH-NORTHWEST THROUGH THE EASTERN GREAT LAKES. 12Z SURFACE ANALYSIS PLACED THE 1016MB REMNANT CYCLONE NEAR LAKE ONTARIO...WITH AN OCCLUDED FRONT SOUTHEAST INTO THE ATLANTIC. A STATIONARY BOUNDARY STRETCHED SOUTHWEST FROM OFF THE MID ATLANTIC COAST THROUGH THE WESTERN GULF OF MEXICO. A WEAK 1022MB ANTICYCLONE WAS LOCATED ACROSS SOUTHERN LAKE MICHIGAN...WHILE THE NEXT STALLED BOUNDARY STRETCHED FROM THE JAMES BAY SOUTH THROUGH TEXAS...WITH A 1020MB CYCLONE LOCATED IN SOUTHEAST IOWA. MODELS... THE 12Z NAM (WRF-NMM)/GFS/CANADIAN ALONG WITH THE 00Z EUROPEAN AND UKMET WERE EXAMINED. THE GLOBAL MODELS WERE IN GOOD AGREEMENT WITH SHOWING ENERGY FROM ERNESTO SHEARS INTO THE UPPER LOW ACROSS THE CENTRAL CONUS...ENCOURAGING A TROUGH TO DEVELOP ACROSS THE EASTERN CONUS FOR MIDWEEK. SPLIT FLOW DEVELOPS LATE THIS WORK WEEK...WITH A NORTHERN STREAM WAVE DIVING SOUTHEAST INTO THE GREAT LAKES FOR THE WEEKEND. THE 12Z NAM SPURIOUSLY DEVELOPS A CYCLONE OFF THE CAROLINA COAST TUESDAY...WHICH AFFECTS THE PRECIPITATION DISTRIBUTION (LESS) AND FRONTAL POSITION DURING THE MIDWEEK. ENSEMBLE DATA... 00Z GFS 500MB HEIGHT ENSEMBLES SHOW GOOD CONSISTENCY WITH SHEARING A PORTION OF ERNESTOS REMNANT ENERGY SOUTHWEST INTO THE MIDWEST UPPER LOW...ENCOURAGING THE DEVELOPMENT OF AN EAST COAST TROUGH DURING THE MIDWEEK. ENERGY AT THE BASE OF THE TROUGH IS SHOWN TO RETROGRADE WESTWARD...IN FAVOR OF BUILDING HEIGHTS ACROSS THE GULF OF MEXICO AND SPLIT FLOW ACROSS THE MID ATLANTIC REGION DURING NEXT WEEKEND. 00Z GFS ENSEMBLE MOS INDICATES MEAN HIGHS HOVER NEAR 80F THROUGH THE LONG RANGE EXCEPT NEAR 70F TUESDAY WHEN MEAN POPS ARE CATEGORICAL. MEAN LOWS ARE NEAR 60F DURING THE LONG RANGE. FORECAST RATIONALE... PATTERN PROGRESSION ACROSS THE NORTHERN HEMISPHERE DURING THE PAST 5 DAYS CAN BE CHARACTERIZED AS AMPLIFYING TOWARD A BLOCKED FLOW. BLOCKING ACROSS THE CONUS WILL EVOLVE AS A PORTION OF ERNESTOS UPPER LEVEL ENERGY SHEARS SOUTHWEST INTO THE MIDWEST UPPER LOW...ENCOURAGING THE DEVELOPMENT OF AN EASTERN CONUS TROUGH THROUGH MIDWEEK. GOES PRECIPITABLE WATER IMAGERY INDICATES DEEP LAYER MOISTURE IS CURRENTLY CONFINED TO THE SOUTHEAST CONUS...AND AHEAD OF THE SECOND BOUNDARY IN SOUTHEAST TEXAS. AMPLIFYING TROUGH ACROSS THE EAST CENTRAL CONUS EARLY DURING THE WORK WEEK WILL SERVE TO STRENGTHEN THE BAROCLINIC ZONE TO THE WEST...DRAWING DEEP LAYER MOISTURE NORTHWARD INTO THE MID ATLANTIC. ISENTROPIC OVERRUNNING WILL AID IN MAKING MONDAY NIGHT AND TUESDAYS PRECIPITATION ANOTHER GOOD SOAKING ACROSS THE REGION. RAIN RATES WILL HAVE TO BE MONITORED AS MARFC 6 HOUR FLASH FLOOD GUIDANCE IS CURRENTLY 1.5" ACROSS CENTRAL VIRGINIA. 12Z GFS FORECAST PRECIPITABLE WATER VALUES NEAR 2" TUESDAY IS +2 STANDARD DEVIATIONS ABOVE THE 1960-2005 KIAD RAOB OBSERVED NORMAL FOR THIS TIME OF YEAR. AS THE TROUGH ACROSS THE EAST COAST TRANSITIONS TO SPLIT FLOW...WEAK HIGH PRESSURE WILL BUILD INTO THE REGION LATE DURING THE WORK WEEK. A SHARP COLD FRONT IS EXPECTED TO APPROACH FROM THE NORTHWEST FOR THE WEEKEND. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SHORT TERM/AVIATION...ROSA LONG TERM...ROGOWSKI MARINE...ROSA/ROGOWSKI md AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1035 PM EDT SUN SEP 3 2006 .UPDATE... UPPER MI REMAINS IN BETWEEN WEATHER SYSTEMS TONIGHT WITH UPPER LOW/REMNANTS OF ERNESTO SPINNING OVER SOUTHWEST QUEBEC AND AN UPPER LOW SPINNING OVER NORTHERN IA. REGIONAL RADAR LOOP WAS SHOWING SOME SHRAS PINWHEELING AROUND BOTH LOWS. WHILE OVERALL RAIN CHANCES WILL REMAIN LIMITED ACROSS UPPER MICHIGAN TONIGHT WILL KEEP SLGT CHC POP GOING FOR THE OVERNIGHT HOURS AS SOME SPRINKLES TO THE EAST MAY MANAGE TO MAKE IT FAR ENOUGH WEST TO AFFECT EASTERN SECTIONS OF THE U.P. LOW LEVEL MOISTURE HAS INCREASED ACROSS THE ENTIRE AREA WITH DPS IN THE MID/UPPER 50S. FCST LOWS IN THE MID 50S APPEAR TO BE ON TRACK. WHILE SOME PATCHY FOG WILL BE POSSIBLE AGAIN TONIGHT WITH THE HIGHER DPS...BKN/OVC MID/HIGH CLOUDS SHOULD PREVENT WIDESPREAD FOG DEVELOPMENT. .PREVIOUS DISCUSSION ISSUED AT 349 PM EDT... THE MAIN CONCERN WITH THIS FORECAST PACKAGE IS THE POTENTIAL FOR RAIN TONIGHT AND RAIN. WATER VAPOR IMAGERY AND RUC SHOWING TWO LOW CENTER OVER NORTHERN CONUS. ONE OF THE LOWS IS OVER SOUTHEAST ONTARIO...AND THE OTHER IS OVER KFSD. A BROAD RIDGE STRETCHES FROM THE NORTHERN ROCKIES ACROSS SOUTHERN CANADA INTO SOUTHERN QUEBEC. SURFACE ANALYSIS SHOWING A WEAK LOW OVER CENTRAL WISCONSIN. THIS LOW IS IN THE MIDST OF A LARGE PRESSURE CENTER BLANKETING MUCH OF THE NORTHERN PLAINS AND THE UPPER GREAT LAKES. ANOTHER LOW IS DEVELOPING OVER THE GREAT BASIN. COMPOSITE RADAR AND SURFACE REPORTS INDICATE SCATTERED SHOWERS WERE OCCURRING OVER SOUTHERN MINNESOTA...NORTHEAST IOWA AND WESTERN WISCONSIN IN ASSOCIATION WITH THE LOW OVER KFSD. AS THE LOW OVER ONTARIO PULLS NORTHEAST INTO SOUTHERN QUEBEC THE LOW OVER KFSD WILL RELOCATE OVER THE KDSM AREA. WEAK SHORTWAVES ROTATING AROUND THE IOWA LOW WILL SWEEP THROUGH THE FORECAST AREA TONIGHT...AS THE SURFACE LOW OVER WISCONSIN WEAKENS AND WASHES OUT. WEAK ISENTROPIC ASCENT OVER THE AREA TONIGHT. ACCORDING TO FORECAST SOUNDING...IT APPEARS THAT MOISTURE REMAINS VERY LIMITED OVERNIGHT. LOW LEVEL MEAN RH AND PRECIPITABLE WATER IS LOW. MODELS SHOW A CAPPING INVERSION AROUND 800MB. THUS WILL KEEP ONLY A SLIGHT CHANCE OF SHOWERS OVERNIGHT. WHAT MOISTURE IS AVAILABLE IS MAINLY OVER THE SOUTHERN AND EASTERN COUNTIES AS PER NAM12. THE MID LEVEL LOW WILL TRAVERSE TO THE TRI-CITY AREA ON MONDAY. WEAK SHORTWAVES ROTATING AROUND THIS LOW WILL CONTINUE TO SWEEP THROUGH THE SOUTHERN PART OF THE FORECAST AREA. THE SURFACE RIDGE WILL BLANKET THE UPPER GREAT LAKES REGION. GFS FORECAST SOUNDING PROG THE AIR MASS ABOVE 500MB WILL BE MOSTLY SATURATION....WHILE BELOW 500MB THE MEAN RELATIVE HUMIDITY WILL BE LESS THAN 70 PERCENT AND AS LOW AS 45 PERCENT ACROSS LAKE SUPERIOR. THE MID LEVEL LOW WILL MOVE INTO CENTRAL ILLINOIS BY TUESDAY MORNING. SHORTWAVES WRAPPING AROUND THIS LOW WILL STAY TO THE SOUTH OF THE FORECAST AREA. DRY AIR WILL CONTINUE TO DOMINATE CONDITIONS OVER THE FORECAST AREA. THE MID LEVEL LOW WILL SHIFT INTO SOUTHEAST INDIANA ON TUESDAY AND THEN INTO THE LOWER GREAT LAKES TUESDAY NIGHT. ANOTHER WEAK COLD FRONT WILL SLIDE ACROSS UPPER MICHIGAN TUESDAY NIGHT. THE AIR MASS WILL REMAIN DRY. THUS DO NOT EXPECT TO SEE ANY PRECIPITATION WITH THIS. SHORTWAVE ENERGY WILL MAINLY BE EAST OF THE FORECAST AREA. A SURFACE RIDGE WILL BE OVER THE FORECAST AREA ON WEDNESDAY MORNING AND WILL SHIFT INTO LOWER MICHIGAN BY THE AFTERNOON. AGAIN THE AIR MASS WILL REMAIN TOO DRY TO PRODUCE ANY PRECIPITATION. THE MODELS ARE IN A FAIRLY GOOD AGREEMENT. THE LONGWAVE TROUGH OVER HUDSON BAY WILL REMAIN STATIONARY THROUGH THURSDAY. GFS WILL DEVELOP A SHORTWAVE OVER NORTHERN ONTARIO. A CANADIAN COLD FRONT WILL SWEEP INTO NORTHERN LAKE SUPERIOR THURSDAY AFTERNOON. ISENTROPIC ASCENT WILL BE WEAK AHEAD OF THIS FRONT. LOW LEVEL MOISTURE WILL BE SCARCE AS PER GFS FORECAST SOUNDINGS. HOWEVER...THE SOUNDINGS SUGGEST THICK LAYER OF HIGH CLOUDS. BY LATE AFTERNOON...INCREASED MOISTURE FIELD WILL SPREAD INTO WESTERN LAKE SUPERIOR...AS WILL AN INCREASE IN Q-VECTOR CONVERGENCE. THUS WILL ADD A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS THERE. THE SHORTWAVE WILL SWEEP ACROSS UPPER MICHIGAN THURSDAY NIGHT. LOW LEVEL MOISTURE ALONG WITH INCREASE IN PRECIPITABLE WATER WILL ALSO SWEEP THROUGH THE FORECAST AREA ALONG WITH THE COLD FRONT. COLD AIR ADVECTION AT THE LOW LEVELS RAPIDLY DECREASES THE LI'S BEHIND THE FRONT SO WILL CALL FOR ONLY A CHANCE OF SHOWERS ALONG WITH THE FRONT. Q-VECTOR DIVERGENCE WILL INCREASE OVER THE AREA FRIDAY NIGHT. DRY AIR ADVECTION WILL DIMINISH THE CHANCE OF RAIN ON SATURDAY. THE COLD FRONT WILL PUSH INTO LOWER MICHIGAN BY EARLY EVENING. A LOW CENTER MOVING ALONG THE FRONT WILL MOVE INTO SOUTHEAST ONTARIO BY 12Z SATURDAY. WITH DRIER AIR AND MORE STABLE CONDITIONS WILL REDUCE THE CHANCE OF PRECIPITATION. THE SHORTWAVE DEVELOPING OVER ONTARIO WILL SHIFT INTO LAKE SUPERIOR BY 12Z SUNDAY AND ACROSS THE AREA ON SUNDAY. THE COLD FRONT WILL EDGE INTO SOUTHERN LOWER MICHIGAN ON SUNDAY. A SECONDARY LOW RACING ALONG THE COLD FRONT WILL MOVE RAPIDLY THROUGH LOWER MICHIGAN ON SUNDAY. THE SURFACE HIGH WILL CONTINUE TO DOMINATE THE AIR MASS OVER THE FORECAST AREA ON SUNDAY AND KEEP THE AIR DRY. IN SPITE OF THE INSTABILITY WITH THE SHORTWAVE...THE LACK OF MOISTURE AND SURFACE STABILITY WILL LIMIT THE DEVELOPMENT OF ANY PRECIPITATION. SO PLAN TO KEEP SUNDAY DRY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DLG (PREV DISCUSSION) MZ (UPDATE) mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 822 PM EDT SUN SEP 3 2006 .UPDATE...COMPLEX UPPER AIR SETUP CONTINUES TO COMPLICATE THE FORECAST. IN SUMMARY...THE REMNANTS OF THE UPPER LEVEL LOW FROM ERNESTO (CENTERED NEAR THE SOUTHERN ONTARIO/QUEBEC BORDERS) AND ANOTHER UPPER LOW (ACROSS THE CENTRAL PLAINS) APPEAR TO BE TRYING TO MELD TOGETHER. MEANWHILE...SATELLITE AND SURFACE OBSERVATIONS INDICATE THAT DIURNALLY DRIVEN CU ACROSS SOUTHWESTERN HALF OF THE FORECAST AREA HAS LARGELY DISSIPATED WITH THE LOSS OF DAYTIME HEATING. HOWEVER...AN EXTENSIVE SWATCH OF MID CLOUDS IS NOW ROTATING SOUTHWESTWARD INTO THE FORECAST AREA FROM THE NORTHEAST. THE MAIN SHORT TERM FORECAST CONCERNS WILL REVOLVE AROUND CLOUD COVER AND POPS ALONG WITH LOW TEMPERATURES AND THE POTENTIAL FOR FOG. IF THE MODELS ARE CORRECT IN BLENDING THE TWO UPPER LEVEL FEATURES TOGETHER THEN AT A MINIMUM...CLOUDS SHOULD BE ON THE INCREASE OVERNIGHT. CONSIDERING SATELLITE LOOP IS ALREADY SHOWING THIS TO BE THE CASE WILL EXPAND MOSTLY CLOUDY SKIES FROM NORTHEAST TO SOUTHWEST OVERNIGHT. DESPITE LIGHT WINDS...TEMPERATURES WILL LIKELY NOT RADIATE ALL THAT MUCH (ESPECIALLY NORTHEAST ZONES) SO HAVE ADDED A COUPLE OF DEGREES TO LOWS. THIS MAY ALSO INHIBIT FOG FORMATION BUT DEWPOINTS CURRENTLY RUNNING IN THE 50S COULD STILL ALLOW FOR SOME PATCHY FORMATION (ESPECIALLY SOUTHWEST ZONES WHERE THE CLOUDS ARE EXPECTED TO ARRIVE THE LATEST). LASTLY...APX RADAR SHOWING PLENTY OF RETURNS ACROSS EASTERN UPPER BUT NOTHING BEING REPORTED BY SURFACE OBS SO THIS IS LIKELY ONLY VIRGA WITH LOWER LEVELS ON THE DRIER SIDE. AM STILL A BIT WORRIED THAT A FEW DROPS WILL REACH THE GROUND SO HAVE ADDED IN SOME SPRINKLES UP THAT WAY. UPDATED ZONES AND GRIDS ALREADY OUT. SULLIVAN .PREV DISCUSSION...ISSUED 400 PM SEP 3 18Z RUC ANALYSIS AND VIS/IR/WV IMAGERY SHOW A NEARLY STATIONARY UPPER LEVEL LOW OVER THE FAR SW CORNER OF SD AND NE MOVING UPPER LEVEL LOW OVER EASTERN ONTARIO. NORTHERN MICHIGAN LIES BETWEEN THESE FEATURES IN A REGION OF CYCLONIC FLOW. CONSIDERABLE CLOUD COVER EXISTS OVER EASTERN UPPER AND NE LOWER...AND SOME OF THESE CLOUDS HAVE TRIED TO WORK WESTWARD...BUT HAVE BEEN RUNNING INTO MID-LEVEL DRY AIR WHICH HAS SLOWED ITS ADVANCEMENT. THE SCATTERED SHOWERS THAN PRODUCED A COUPLE WATERSPOUTS OVER LAKE HURON HAVE MOSTLY FIZZLED OUT WITH WEAKENING ISENTROPIC LIFT. A FEW BLIPS ON THE RADAR STILL EXISTS BUT NO EVIDENCE OF THEM REACHING THE GROUND. MEANWHILE...TEMPERATURES HAVE WARMED INTO THE LOWER TO MIDDLE 70S ACROSS NW LOWER WHERE THEY HAVE SEEN PLENTY OF SUNSHINE TODAY. MAIN FORECAST CONCERNS INCLUDE THE CHANCE OF PRECIPITATION OVER THE NEXT 24 HOURS WITH LINGERING MOISTURE TONIGHT...AND DIURNAL ENHANCEMENT WITH THE UPPER LEVEL TROUGH NEARBY TOMORROW AFTERNOON. TONIGHT...SURFACE LOW PRESSURE OVER LAKE ONTARIO WILL PUSH OFF TO THE NORTHEAST ALONG WITH ITS UPPER LEVEL SHORTWAVE. MEANWHILE...THE UPPER LEVEL LOW OVER SE SD WILL SLOWLY MIGRATE OVER IOWA. NAM/GFS BOTH SHOW THESE SYSTEM PHASING TOGETHER AND FORMING A 500MB TROUGH AXIS. AS THE SURFACE LOW OVER ONTARIO PULLS AWAY...BELIEVE ALOT OF THE LOW LEVEL MOISTURE WILL MOVE EAST WITH IT OVER LAKE HURON. HOWEVER...WITH THE PHASING...THINK THAT ENOUGH MID AND UPPER LEVEL MOISTURE WILL REMAIN OVER EASTERN UPPER/NE LOWER TO PRODUCE MOSTLY CLOUDY CONDITIONS...WHILE AREAS ACROSS THE CENTRAL AND NW CWA WILL STAY PARTLY CLOUDY WHERE THERE IS DRIER AIR PRESENT IN THE MID-LEVELS. WILL KEEP A 30 PCT CHANCE OF SHOWERS THROUGH 00Z TO COVER THE LINGERING MOISTURE AND WEAK 300-305K ISENTROPIC LIFT FROM TAWAS TO CHEBOYGAN TO THE SOO...BUT HAVE REMOVED ANY MENTION OF PRECIP FROM THERE. ITS QUESTIONABLE WHETHER TO KEEP A MENTION OF PATCHY FOG...WITH MANY PLACES MIXING OUT ESPECIALLY OVER THE INTERIOR OF NW LOWER. NONETHELESS...DON/T THINK THAT DEWPOINTS HAVE FALLEN FAR ENOUGH (LOWER 50S) TO REMOVE THIS WORDING SINCE MANY OF THESE SAME PLACES COULD SEE LOWS FALL IN THE UPPER 40S WITH SOME CLEARING EXPECTED AND LIGHT WINDS. LOW LEVEL CYCLONIC FLOW WILL REMAIN PRESENT AS WELL. TOMORROW...UPPER LEVEL TROUGH AXIS REMAINS NEARLY STATIONARY OVER THE GREAT LAKES...STRETCHING FROM NW IL TO QUEBEC...AND DIRECTLY OVER NORTHERN MICHIGAN. HOW MUCH CLOUD COVER WILL BE PRESENT IS STILL QUESTIONABLE. MODELS INSIST ON LEAVING A MID AND UPPER LEVEL CLOUD DECK WITHIN THIS UPPER LEVEL TROUGH...AND HAVE TRIED TO REFLECT THIS IN THE GRIDS. GFS SEEMS TO BE HANDLING THE MOISTURE A LITTLE BETTER TOMORROW...WITH A SMALL CAP AT 700MB...WHEREAS THE NAM PLACES THIS CAP ABOVE 600MB. WITH THE UPPER LEVEL TROUGH PRESENT...A LOWER CAP MAKES SENSE HERE. ALWAYS GOT TO BE CAREFUL OF DIURNAL CONVECTION IN THESE CASES. BUT MODIFIED SOUNDINGS WITH A PARCEL OF 75/53 REVEALS LESS THAN 50 J/KG ML CAPE WITH A CIN OF 30 J/KG ACROSS THE SW CWA...WHERE THE HIGHEST MID-LEVEL LAPSE RATES RESIDE (6-6.5 C/KM). CONVECTIVE TEMPERATURES ARE ONLY IN THE LOWER 70S...SO TEMPERATURES WILL HAVE TO BE WATCHED TO SEE IF THEY WARM ENOUGH TO SCRAPE BY THE CAP. CONVERSELY...DEWPOINTS WILL ALSO HAVE TO BE MONITORED TO SEE HOW MUCH WE MIX OUT. THERE IS NO OTHER FORCING PRESENT...SO WITH THIS IN MIND...HAVE KEPT POPS OUT OF THE FORECAST. MPC LONG TERM DISCUSSION...MAIN FEATURE OF INTEREST FOR THE LONG TERM PACKAGE (AT LEAST THROUGH WEDNESDAY) CLEARLY VISIBLE ON AFTERNOON WATER VAPOR SATELLITE IMAGERY AS CUTOFF MID AND UPPER LEVEL LOW WOBBLING SLOWLY EAST ACROSS NORTHWEST IOWA. FORECAST CONCERNS REVOLVE AROUND MAINLY DIURNALLY DRIVER PRECIPITATION CHANCES THROUGH MIDWEEK AND POSSIBLE ADDITIONAL SHOWER AND THUNDERSTORM CHANCES LATER IN THE WEEK AS ANOTHER SYSTEM DROPS SOUTHEAST OUT OF CANADA. MONDAY NIGHT...HAVE GONE AHEAD AND DROPPED SLIGHT CHANCE POPS. MODELS IN DECENT AGREEMENT THAT UPPER LEVEL LOW WILL MOVE ACROSS CENTRAL ILLINOIS DURING THE OVERNIGHT. WITH FEATURE FAR ENOUGH REMOVED FROM AREA...OVERALL FORCING MECHANISMS FOR PRECIPITATION APPEAR NIL. TUESDAY...CIRCULATION CENTER MOVES ACROSS THE OHIO VALLEY AND BEGINS TO OPEN UP. BEST MID LEVEL COLD POCKET PASSES SOUTH OF THE REGION IN CONJUNCTION WITH MID LEVEL LOW. HOWEVER...500MB TEMPERATURES OVER THE REGION DO DROP TO AROUND -15C TO -16C DURING THE AFTERNOON...PER 12Z GFS. TAKING A GFS POINT MODEL SOUNDING FOR THE SOUTH CENTRAL PART OF THE CWA WITH A REASONABLE SURFACE TEMPERATURE AND DEWPOINT OF 76F/55F RESPECTIVELY DOES SHOW ALMOST 200J/KG ML CAPE WITH NO INHIBITION. AS FOR FORCING...NOT A WHOLE LOT TO HANG YOUR HAT ON. POSSIBLE HARD TO TIME VORTICITY LOBES ROTATING AROUND LOW MAY HELP INITIATION. ALSO...WEAK LOW LEVEL WIND FIELDS SHOULD ALLOW LAKE BREEZE GENERATION DURING THE LATE MORNING/EARLY AFTERNOON HOURS. ENHANCED CONVERGENCE ALONG THESE MAY SPARK SOME SHOWERS. GIVEN OVERALL LACK OF INSTABILITY AND MARGINAL MID LEVEL LAPSE RATES OF 6 TO 6.5 C/KM WILL KEEP THUNDER OUT OF THE FORECAST. THE TIP OF THE MITT AND EASTERN UPPER APPEAR TOO FAR REMOVED FROM DYNAMICS AND WILL LEAVE THESE AREAS DRY. TUESDAY NIGHT...MUCH LIKE MONDAY NIGHT...LOSS OF SOLAR INSOLATION SHOULD CAUSE ANY AFTERNOON SHOWER ACTIVITY TO QUICKLY DECAY. HAVE GONE AHEAD AND REMOVED ANY MENTION OF SHOWERS. WEDNESDAY...CLOSED LOW/TROUGH CONTINUES EAST AND BECOMES ABSORBED IN LONGWAVE TROUGH DEVELOPING ACROSS EASTERN CANADA AND THE NORTHEAST. MAJORITY OF MODELS...EXCLUDING THE NAM...ARE RATHER QUICK WITH THIS TRANSLATION AND WOULD HAVE REGION IN LARGE SCALE SUBSIDENCE BEHIND DEPARTING SHORTWAVE. GIVEN RECENT MODEL TRENDS TO SPEED THIS SYSTEM UP AND RATHER GOOD MODEL AGREEMENT BETWEEN THE 12Z GFS/UKMET AND 00Z ECMWF WILL SIDE WITH THIS FASTER SCENARIO AND REMOVE CHANCE SHOWERS ON WEDNESDAY. POSSIBLE THAT LAKE INDUCED CONVERGENCE ZONES ACTING ON SOME LIMITED INSTABILITY MAY SPARK AN ISOLATED SHOWER. FEEL OVERALL THREAT VERY LIMITED AND NOT WORTH A MENTION IN ZONES/GRIDS. WEDNESDAY NIGHT AND THURSDAY...MID LEVEL SHORTWAVE RIDGE SLIDES OVER THE REGION ALLOWING DRY CONDITIONS. THURSDAY NIGHT THROUGH FRIDAY...INCLEMENT WEATHER RETURNS AS SHORTWAVE DROPS SOUTHEAST OUT OF CANADA BETWEEN EXPANDING WESTERN NOAM RIDGE AXIS AND HUDSON BAY/NORTHERN QUEBEC UPPER LEVEL LOW. ASSOCIATED LOW PRESSURE AND ATTENDANT COLD FRONT WILL SWEEP THROUGH THE REGION BY FRIDAY EVENING. AMOUNT OF MOISTURE RETURN IN QUESTION WITH SURFACE RIDGE ACROSS THE NORTHERN GULF BLOCKING MOISTURE TRANSPORT NORTH. WHILE TIMING WILL SURELY CHANGE...FELT BEST COURSE OF ACTION AT THIS TIME WAS TO MENTION A CHANCE OF SHOWERS AND STORMS BEGINNING THURSDAY NIGHT FOR THE EASTERN UPPER AND ALL AREAS ON FRIDAY. SATURDAY AND SUNDAY...DRY WEEKEND APPEARS ON TAP AS CANADIAN HIGH PRESSURE BUILDS SOUTH BEHIND DEPARTING COLD FRONT. POTENTIAL DOES EXIST FOR A RATHER SIGNIFICANT COOL DOWN DEPENDING ON HOW AMPLIFIED PATTERN BECOMES. LATEST GFS PROGS 850MB TEMPERATURES TO APPROACH 0C WITH 12Z ECMWF A LITTLE WARMER. WILL PLAY RATHER CONSERVATIVE AT THIS JUNCTURE AND FORECAST HIGHS IN THE UPPER 60S TO AROUND 70 AND WAIT FOR FUTURE MODEL ITERATIONS TO PEG DOWN AMOUNT OF COOLING. MSB && .APX...WATCHES/WARNINGS/ADVISORIES...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 400 PM EDT SUN SEP 3 2006 .DISCUSSION...18Z RUC ANALYSIS AND VIS/IR/WV IMAGERY SHOW A NEARLY STATIONARY UPPER LEVEL LOW OVER THE FAR SW CORNER OF SD AND NE MOVING UPPER LEVEL LOW OVER EASTERN ONTARIO. NORTHERN MICHIGAN LIES BETWEEN THESE FEATURES IN A REGION OF CYCLONIC FLOW. CONSIDERABLE CLOUD COVER EXISTS OVER EASTERN UPPER AND NE LOWER...AND SOME OF THESE CLOUDS HAVE TRIED TO WORK WESTWARD...BUT HAVE BEEN RUNNING INTO MID-LEVEL DRY AIR WHICH HAS SLOWED ITS ADVANCEMENT. THE SCATTERED SHOWERS THAN PRODUCED A COUPLE WATERSPOUTS OVER LAKE HURON HAVE MOSTLY FIZZLED OUT WITH WEAKENING ISENTROPIC LIFT. A FEW BLIPS ON THE RADAR STILL EXISTS BUT NO EVIDENCE OF THEM REACHING THE GROUND. MEANWHILE...TEMPERATURES HAVE WARMED INTO THE LOWER TO MIDDLE 70S ACROSS NW LOWER WHERE THEY HAVE SEEN PLENTY OF SUNSHINE TODAY. MAIN FORECAST CONCERNS INCLUDE THE CHANCE OF PRECIPITATION OVER THE NEXT 24 HOURS WITH LINGERING MOISTURE TONIGHT...AND DIURNAL ENHANCEMENT WITH THE UPPER LEVEL TROUGH NEARBY TOMORROW AFTERNOON. TONIGHT...SURFACE LOW PRESSURE OVER LAKE ONTARIO WILL PUSH OFF TO THE NORTHEAST ALONG WITH ITS UPPER LEVEL SHORTWAVE. MEANWHILE...THE UPPER LEVEL LOW OVER SE SD WILL SLOWLY MIGRATE OVER IOWA. NAM/GFS BOTH SHOW THESE SYSTEM PHASING TOGETHER AND FORMING A 500MB TROUGH AXIS. AS THE SURFACE LOW OVER ONTARIO PULLS AWAY...BELIEVE ALOT OF THE LOW LEVEL MOISTURE WILL MOVE EAST WITH IT OVER LAKE HURON. HOWEVER...WITH THE PHASING...THINK THAT ENOUGH MID AND UPPER LEVEL MOISTURE WILL REMAIN OVER EASTERN UPPER/NE LOWER TO PRODUCE MOSTLY CLOUDY CONDITIONS...WHILE AREAS ACROSS THE CENTRAL AND NW CWA WILL STAY PARTLY CLOUDY WHERE THERE IS DRIER AIR PRESENT IN THE MID-LEVELS. WILL KEEP A 30 PCT CHANCE OF SHOWERS THROUGH 00Z TO COVER THE LINGERING MOISTURE AND WEAK 300-305K ISENTROPIC LIFT FROM TAWAS TO CHEBOYGAN TO THE SOO...BUT HAVE REMOVED ANY MENTION OF PRECIP FROM THERE. ITS QUESTIONABLE WHETHER TO KEEP A MENTION OF PATCHY FOG...WITH MANY PLACES MIXING OUT ESPECIALLY OVER THE INTERIOR OF NW LOWER. NONETHELESS...DONT THINK THAT DEWPOINTS HAVE FALLEN FAR ENOUGH (LOWER 50S) TO REMOVE THIS WORDING SINCE MANY OF THESE SAME PLACES COULD SEE LOWS FALL IN THE UPPER 40S WITH SOME CLEARING EXPECTED AND LIGHT WINDS. LOW LEVEL CYCLONIC FLOW WILL REMAIN PRESENT AS WELL. TOMORROW...UPPER LEVEL TROUGH AXIS REMAINS NEARLY STATIONARY OVER THE GREAT LAKES...STRETCHING FROM NW IL TO QUEBEC...AND DIRECTLY OVER NORTHERN MICHIGAN. HOW MUCH CLOUD COVER WILL BE PRESENT IS STILL QUESTIONABLE. MODELS INSIST ON LEAVING A MID AND UPPER LEVEL CLOUD DECK WITHIN THIS UPPER LEVEL TROUGH...AND HAVE TRIED TO REFLECT THIS IN THE GRIDS. GFS SEEMS TO BE HANDLING THE MOISTURE A LITTLE BETTER TOMORROW...WITH A SMALL CAP AT 700MB...WHEREAS THE NAM PLACES THIS CAP ABOVE 600MB. WITH THE UPPER LEVEL TROUGH PRESENT...A LOWER CAP MAKES SENSE HERE. ALWAYS GOT TO BE CAREFUL OF DIURNAL CONVECTION IN THESE CASES. BUT MODIFIED SOUNDINGS WITH A PARCEL OF 75/53 REVEALS LESS THAN 50 J/KG ML CAPE WITH A CIN OF 30 J/KG ACROSS THE SW CWA...WHERE THE HIGHEST MID-LEVEL LAPSE RATES RESIDE (6-6.5 C/KM). CONVECTIVE TEMPERATURES ARE ONLY IN THE LOWER 70S...SO TEMPERATURES WILL HAVE TO BE WATCHED TO SEE IF THEY WARM ENOUGH TO SCRAPE BY THE CAP. CONVERSELY...DEWPOINTS WILL ALSO HAVE TO BE MONITORED TO SEE HOW MUCH WE MIX OUT. THERE IS NO OTHER FORCING PRESENT...SO WITH THIS IN MIND...HAVE KEPT POPS OUT OF THE FORECAST. MPC LONG TERM DISCUSSION...MAIN FEATURE OF INTEREST FOR THE LONG TERM PACKAGE (AT LEAST THROUGH WEDNESDAY) CLEARLY VISIBLE ON AFTERNOON WATER VAPOR SATELLITE IMAGERY AS CUTOFF MID AND UPPER LEVEL LOW WOBBLING SLOWLY EAST ACROSS NORTHWEST IOWA. FORECAST CONCERNS REVOLVE AROUND MAINLY DIURNALLY DRIVER PRECIPITATION CHANCES THROUGH MIDWEEK AND POSSIBLE ADDITIONAL SHOWER AND THUNDERSTORM CHANCES LATER IN THE WEEK AS ANOTHER SYSTEM DROPS SOUTHEAST OUT OF CANADA. MONDAY NIGHT...HAVE GONE AHEAD AND DROPPED SLIGHT CHANCE POPS. MODELS IN DECENT AGREEMENT THAT UPPER LEVEL LOW WILL MOVE ACROSS CENTRAL ILLINOIS DURING THE OVERNIGHT. WITH FEATURE FAR ENOUGH REMOVED FROM AREA...OVERALL FORCING MECHANISMS FOR PRECIPITATION APPEAR NIL. TUESDAY...CIRCULATION CENTER MOVES ACROSS THE OHIO VALLEY AND BEGINS TO OPEN UP. BEST MID LEVEL COLD POCKET PASSES SOUTH OF THE REGION IN CONJUNCTION WITH MID LEVEL LOW. HOWEVER...500MB TEMPERATURES OVER THE REGION DO DROP TO AROUND -15C TO -16C DURING THE AFTERNOON...PER 12Z GFS. TAKING A GFS POINT MODEL SOUNDING FOR THE SOUTH CENTRAL PART OF THE CWA WITH A REASONABLE SURFACE TEMPERATURE AND DEWPOINT OF 76F/55F RESPECTIVELY DOES SHOW ALMOST 200J/KG ML CAPE WITH NO INHIBITION. AS FOR FORCING...NOT A WHOLE LOT TO HANG YOUR HAT ON. POSSIBLE HARD TO TIME VORTICITY LOBES ROTATING AROUND LOW MAY HELP INITIATION. ALSO...WEAK LOW LEVEL WIND FIELDS SHOULD ALLOW LAKE BREEZE GENERATION DURING THE LATE MORNING/EARLY AFTERNOON HOURS. ENHANCED CONVERGENCE ALONG THESE MAY SPARK SOME SHOWERS. GIVEN OVERALL LACK OF INSTABILITY AND MARGINAL MID LEVEL LAPSE RATES OF 6 TO 6.5 C/KM WILL KEEP THUNDER OUT OF THE FORECAST. THE TIP OF THE MITT AND EASTERN UPPER APPEAR TOO FAR REMOVED FROM DYNAMICS AND WILL LEAVE THESE AREAS DRY. TUESDAY NIGHT...MUCH LIKE MONDAY NIGHT...LOSS OF SOLAR INSOLATION SHOULD CAUSE ANY AFTERNOON SHOWER ACTIVITY TO QUICKLY DECAY. HAVE GONE AHEAD AND REMOVED ANY MENTION OF SHOWERS. WEDNESDAY...CLOSED LOW/TROUGH CONTINUES EAST AND BECOMES ABSORBED IN LONGWAVE TROUGH DEVELOPING ACROSS EASTERN CANADA AND THE NORTHEAST. MAJORITY OF MODELS...EXCLUDING THE NAM...ARE RATHER QUICK WITH THIS TRANSLATION AND WOULD HAVE REGION IN LARGE SCALE SUBSIDENCE BEHIND DEPARTING SHORTWAVE. GIVEN RECENT MODEL TRENDS TO SPEED THIS SYSTEM UP AND RATHER GOOD MODEL AGREEMENT BETWEEN THE 12Z GFS/UKMET AND 00Z ECMWF WILL SIDE WITH THIS FASTER SCENARIO AND REMOVE CHANCE SHOWERS ON WEDNESDAY. POSSIBLE THAT LAKE INDUCED CONVERGENCE ZONES ACTING ON SOME LIMITED INSTABILITY MAY SPARK AN ISOLATED SHOWER. FEEL OVERALL THREAT VERY LIMITED AND NOT WORTH A MENTION IN ZONES/GRIDS. WEDNESDAY NIGHT AND THURSDAY...MID LEVEL SHORTWAVE RIDGE SLIDES OVER THE REGION ALLOWING DRY CONDITIONS. THURSDAY NIGHT THROUGH FRIDAY...INCLEMENT WEATHER RETURNS AS SHORTWAVE DROPS SOUTHEAST OUT OF CANADA BETWEEN EXPANDING WESTERN NOAM RIDGE AXIS AND HUDSON BAY/NORTHERN QUEBEC UPPER LEVEL LOW. ASSOCIATED LOW PRESSURE AND ATTENDANT COLD FRONT WILL SWEEP THROUGH THE REGION BY FRIDAY EVENING. AMOUNT OF MOISTURE RETURN IN QUESTION WITH SURFACE RIDGE ACROSS THE NORTHERN GULF BLOCKING MOISTURE TRANSPORT NORTH. WHILE TIMING WILL SURELY CHANGE...FELT BEST COURSE OF ACTION AT THIS TIME WAS TO MENTION A CHANCE OF SHOWERS AND STORMS BEGINNING THURSDAY NIGHT FOR THE EASTERN UPPER AND ALL AREAS ON FRIDAY. SATURDAY AND SUNDAY...DRY WEEKEND APPEARS ON TAP AS CANADIAN HIGH PRESSURE BUILDS SOUTH BEHIND DEPARTING COLD FRONT. POTENTIAL DOES EXIST FOR A RATHER SIGNIFICANT COOL DOWN DEPENDING ON HOW AMPLIFIED PATTERN BECOMES. LATEST GFS PROGS 850MB TEMPERATURES TO APPROACH 0C WITH 12Z ECMWF A LITTLE WARMER. WILL PLAY RATHER CONSERVATIVE AT THIS JUNCTURE AND FORECAST HIGHS IN THE UPPER 60S TO AROUND 70 AND WAIT FOR FUTURE MODEL ITERATIONS TO PEG DOWN AMOUNT OF COOLING. MSB && .APX...WATCHES/WARNINGS/ADVISORIES...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 349 PM EDT SUN SEP 3 2006 .DISCUSSION... THE MAIN CONCERN WITH THIS FORECAST PACKAGE IS THE POTENTIAL FOR RAIN TONIGHT AND RAIN. WATER VAPOR IMAGERY AND RUC SHOWING TWO LOW CENTER OVER NORTHERN CONUS. ONE OF THE LOWS IS OVER SOUTHEAST ONTARIO...AND THE OTHER IS OVER KFSD. A BROAD RIDGE STRETCHES FROM THE NORTHERN ROCKIES ACROSS SOUTHERN CANADA INTO SOUTHERN QUEBEC. SURFACE ANALYSIS SHOWING A WEAK LOW OVER CENTRAL WISCONSIN. THIS LOW IS IN THE MIDST OF A LARGE PRESSURE CENTER BLANKETING MUCH OF THE NORTHERN PLAINS AND THE UPPER GREAT LAKES. ANOTHER LOW IS DEVELOPING OVER THE GREAT BASIN. COMPOSITE RADAR AND SURFACE REPORTS INDICATE SCATTERED SHOWERS WERE OCCURRING OVER SOUTHERN MINNESOTA...NORTHEAST IOWA AND WESTERN WISCONSIN IN ASSOCIATION WITH THE LOW OVER KFSD. AS THE LOW OVER ONTARIO PULLS NORTHEAST INTO SOUTHERN QUEBEC THE LOW OVER KFSD WILL RELOCATE OVER THE KDSM AREA. WEAK SHORTWAVES ROTATING AROUND THE IOWA LOW WILL SWEEP THROUGH THE FORECAST AREA TONIGHT...AS THE SURFACE LOW OVER WISCONSIN WEAKENS AND WASHES OUT. WEAK ISENTROPIC ASCENT OVER THE AREA TONIGHT. ACCORDING TO FORECAST SOUNDING...IT APPEARS THAT MOISTURE REMAINS VERY LIMITED OVERNIGHT. LOW LEVEL MEAN RH AND PRECIPITABLE WATER IS LOW. MODELS SHOW A CAPPING INVERSION AROUND 800MB. THUS WILL KEEP ONLY A SLIGHT CHANCE OF SHOWERS OVERNIGHT. WHAT MOISTURE IS AVAILABLE IS MAINLY OVER THE SOUTHERN AND EASTERN COUNTIES AS PER NAM12. THE MID LEVEL LOW WILL TRAVERSE TO THE TRI-CITY AREA ON MONDAY. WEAK SHORTWAVES ROTATING AROUND THIS LOW WILL CONTINUE TO SWEEP THROUGH THE SOUTHERN PART OF THE FORECAST AREA. THE SURFACE RIDGE WILL BLANKET THE UPPER GREAT LAKES REGION. GFS FORECAST SOUNDING PROG THE AIR MASS ABOVE 500MB WILL BE MOSTLY SATURATION....WHILE BELOW 500MB THE MEAN RELATIVE HUMIDITY WILL BE LESS THAN 70 PERCENT AND AS LOW AS 45 PERCENT ACROSS LAKE SUPERIOR. THE MID LEVEL LOW WILL MOVE INTO CENTRAL ILLINOIS BY TUESDAY MORNING. SHORTWAVES WRAPPING AROUND THIS LOW WILL STAY TO THE SOUTH OF THE FORECAST AREA. DRY AIR WILL CONTINUE TO DOMINATE CONDITIONS OVER THE FORECAST AREA. THE MID LEVEL LOW WILL SHIFT INTO SOUTHEAST INDIANA ON TUESDAY AND THEN INTO THE LOWER GREAT LAKES TUESDAY NIGHT. ANOTHER WEAK COLD FRONT WILL SLIDE ACROSS UPPER MICHIGAN TUESDAY NIGHT. THE AIR MASS WILL REMAIN DRY. THUS DO NOT EXPECT TO SEE ANY PRECIPITATION WITH THIS. SHORTWAVE ENERGY WILL MAINLY BE EAST OF THE FORECAST AREA. A SURFACE RIDGE WILL BE OVER THE FORECAST AREA ON WEDNESDAY MORNING AND WILL SHIFT INTO LOWER MICHIGAN BY THE AFTERNOON. AGAIN THE AIR MASS WILL REMAIN TOO DRY TO PRODUCE ANY PRECIPITATION. THE MODELS ARE IN A FAIRLY GOOD AGREEMENT. THE LONGWAVE TROUGH OVER HUDSON BAY WILL REMAIN STATIONARY THROUGH THURSDAY. GFS WILL DEVELOP A SHORTWAVE OVER NORTHERN ONTARIO. A CANADIAN COLD FRONT WILL SWEEP INTO NORTHERN LAKE SUPERIOR THURSDAY AFTERNOON. ISENTROPIC ASCENT WILL BE WEAK AHEAD OF THIS FRONT. LOW LEVEL MOISTURE WILL BE SCARCE AS PER GFS FORECAST SOUNDINGS. HOWEVER...THE SOUNDINGS SUGGEST THICK LAYER OF HIGH CLOUDS. BY LATE AFTERNOON...INCREASED MOISTURE FIELD WILL SPREAD INTO WESTERN LAKE SUPERIOR...AS WILL AN INCREASE IN Q-VECTOR CONVERGENCE. THUS WILL ADD A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS THERE. THE SHORTWAVE WILL SWEEP ACROSS UPPER MICHIGAN THURSDAY NIGHT. LOW LEVEL MOISTURE ALONG WITH INCREASE IN PRECIPITABLE WATER WILL ALSO SWEEP THROUGH THE FORECAST AREA ALONG WITH THE COLD FRONT. COLD AIR ADVECTION AT THE LOW LEVELS RAPIDLY DECREASES THE LI'S BEHIND THE FRONT SO WILL CALL FOR ONLY A CHANCE OF SHOWERS ALONG WITH THE FRONT. Q-VECTOR DIVERGENCE WILL INCREASE OVER THE AREA FRIDAY NIGHT. DRY AIR ADVECTION WILL DIMINISH THE CHANCE OF RAIN ON SATURDAY. THE COLD FRONT WILL PUSH INTO LOWER MICHIGAN BY EARLY EVENING. A LOW CENTER MOVING ALONG THE FRONT WILL MOVE INTO SOUTHEAST ONTARIO BY 12Z SATURDAY. WITH DRIER AIR AND MORE STABLE CONDITIONS WILL REDUCE THE CHANCE OF PRECIPITATION. THE SHORTWAVE DEVELOPING OVER ONTARIO WILL SHIFT INTO LAKE SUPERIOR BY 12Z SUNDAY AND ACROSS THE AREA ON SUNDAY. THE COLD FRONT WILL EDGE INTO SOUTHERN LOWER MICHIGAN ON SUNDAY. A SECONDARY LOW RACING ALONG THE COLD FRONT WILL MOVE RAPIDLY THROUGH LOWER MICHIGAN ON SUNDAY. THE SURFACE HIGH WILL CONTINUE TO DOMINATE THE AIR MASS OVER THE FORECAST AREA ON SUNDAY AND KEEP THE AIR DRY. IN SPITE OF THE INSTABILITY WITH THE SHORTWAVE...THE LACK OF MOISTURE AND SURFACE STABILITY WILL LIMIT THE DEVELOPMENT OF ANY PRECIPITATION. SO PLAN TO KEEP SUNDAY DRY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1103 AM EDT SUN SEP 3 2006 .UPDATE...12Z SURFACE/RUC ANALYSIS AND LATEST VIS/IR/WV/RADAR IMAGERY SHOW WEAK SURFACE RIDING OVER MICHIGAN AND ONE LOW PRESSURE CENTERED OVER WESTERN NY STATE...AND ANOTHER OVER EASTERN SD WITH A COLD FROM TRAILING ACROSS MN/IA/MO. MOISTURE AND WEAK ISENTROPIC LIFT ON THE 300-305K SURFACES ARE WRAPPING AROUND THE NY LOW AND IS HELPING TO CREATE LIGHT TO MODERATE SHOWERS ACROSS NE LOWER. THESE SHOWERS ARE LIKELY GETTING ENHANCED BY LAKE HURON...SINCE 8C AIR AT 850MB IS FLOWING NNE OVER 19C WATER TEMPERATURE. SOME SEMBLANCE OF A CONVERGENCE AXIS WITHIN THESE BAND OF SHOWERS AS WELL (WINDS NNE AT SPT AND NW AT HTL). THE MAJORITY OF THE REMAINING ECHOES ON THE APX RADAR ARE NOT REACHING THE GROUND. 12Z APX SOUNDING SHOWS A SIGNIFICANT DRY LAYER BETWEEN 775MB AND 550MB WITH A DEWPOINT DEPRESSION OF 21C AT 750MB. A SIMILAR TAMDAR SOUNDING EXISTS AT CHIPPEWA AT 1040Z BUT WITH 20C DEWPOINT DEPRESSION AT 650MB. MAIN FORECAST CONCERNS FOR THE REST OF THE AFTERNOON PRIMARILY INCLUDE PRECIP CHANCES. FOR THE REST OF THE AFTERNOON...SHOWER ACTIVITY SO FAR REMAINS SCATTERED AT BEST. WITH THE LOW PULLING SLOWLY AWAY TO THE NE...SOME MOISTURE IS EXPECTED TO WRAP AROUND THE SYSTEM OVER EASTERN UPPER AND NORTH CENTRAL LOWER. HOWEVER...MODELS SEEM TO BE OVERDOING THE MOISTURE BASED ON THE PREVIOUSLY MENTIONED SOUNDINGS...AND THE MOISTURE STILL HAS SOME WORK TO DO IN ORDER TO GET ANY PRECIP. HAVE THEREFORE TRIMMED BACK PRECIPITATION AND LEFT THE WORDING AS SCATTERED FROM STERLING TO CHARLEVOIX TO WHITEFISH POINT. MUCH OF NORTHWEST LOWER WILL REMAIN PARTLY CLOUDY THIS AFTERNOON. MARINE...WILL KEEP SMALL CRAFTS GOING FOR THIS AFTERNOON FOR PORTIONS OF THE LAKE HURON SIDE. LATEST BUOY OBSERVATIONS OVER LAKE HURON SHOW NE WINDS GUSTING TO 17KTS AND WAVES 2.5FT. BUT THINK WITH COASTAL CONVERGENCE AND A DECENT FETCH...WAVES WILL REMAIN IN THE 3 TO 5 FT RANGE IN THE NEARSHORE AREA. ZONES OUT SHORTLY. MPC PREVIOUS DISCUSSION...ISSUED AT 420 AM EDT NRN MI FINDS ITSELF NESTLED BETWEEN TWO UPPER LEVEL SYSTEMS THIS MORNING -- ONE LIFTING SLOWLY NORTHWARD THROUGH SRN ONTARIO...WITH ANOTHER CUT-OFF LOW (NEARLY STATIONARY) OVER SE SOUTH DAKOTA. INTERACTION BETWEEN...MOVEMENT OF...AND ANY PRECIPITATION ASSOCIATED WITH THESE SYSTEMS REMAINS THE PRIMARY FORECAST CHALLENGE THROUGH THE NEXT 72 HRS. MORNING SURFACE MAP SHOWED LOW PRESSURE OVER WRN NEW YORK...WITH ANOTHER LOW OVER W CENTRAL MN. WEAK SURFACE RIDGING EXTENDED FROM LAKE SUPERIOR ACROSS LOWER MI -- BETWEEN THE TWO LOWS. THE SYSTEM TO THE E OF MI WAS PRODUCING PATCHY LIGHT RAIN ACROSS NRN LAKE HURON AND EXTREME NE LOWER MI...A RESULT OF ONTARIO UPPER LOW...MODEST 300-305K ISENTROPIC ASCENT...AND 8H-5H RH >90%. TODAY AND TONIGHT...GFS/NAM AGREE THAT ONTARIO UPPER LOW WILL CONTINUE TO LIFT N TODAY...AS S DAKOTA UPPER LOW DRIFTS INTO IA. WEAK PHASING OF SYSTEMS WILL ALLOW AN ELONGATED UPPER TROUGH AXIS TO FORM OVER THE UPPER GREAT LAKES. THIS WILL PROVIDE CONTINUED SUPPORT FOR LIGHT RAIN ACROSS MAINLY NE PARTS OF FORECAST AREA TODAY. RAIN HAS HAD A DIFFICULT TIME SPREADING WEST THUS FAR -- REMAINING MAINLY OVER LAKE HURON. HOWEVER...BOTH MODELS INSIST THAT PATCHY LIGHT RAIN WILL SPREAD WEST AND REACH THE I-75 CORRIDOR BY LATE AFTERNOON. PER GOING FORECAST...EXPECT BEST CHANCE FOR LIGHT RAIN TODAY N OF A LINE FROM HARRISVILLE TO GAYLORD TO PETOSKEY -- WITH ONLY A SMALL CHANCE FROM TRAVERSE CITY TO GRAYLING TO STANDISH. ORIENTATION OF UPPER TROUGH AXIS...AND 300-305K CONDENSATION PRESSURE DEFICITS OF 10-20 MB SUPPORT A NORTHWARD SHIFT OF THE PATCHY LIGHT RAIN BY TONIGHT. WILL THEREFORE LIMIT SLIGHT CHANCE OF SHOWERS TONIGHT TO AREAS N OF TVC-GAYLORD-APN. MONDAY AND MONDAY NIGHT...CLOSED UPPER LOW TO THE W WILL CONTINUE TO DRIFT ESE THROUGH IA AND INTO IL...AS ONTARIO UPPER LOW DEPARTS TO THE NE. THIS WILL PLACE NRN MI BACK IN WEAK RIDGE POSITION -- BOTH AT THE SURFACE AND ALOFT. RAIN CHANCES APPEAR VERY LOW. HOWEVER...WITH 8H-5H RH VARYING BETWEEN 50-80%...AND UPPER LOW/TROUGH JUST W OF REGION...WILL RETAIN RISK FOR SPRINKLES OR PATCHY LIGHT SHOWERS IN FORECAST. PRECIPITATION WON/T AMOUNT TO MUCH. TUESDAY...UPPER LOW/TROUGH WILL FINALLY SWING E INTO THE LOWER GREAT LAKES. WEAK 7H-5H QG SUPPORT ACROSS SRN AREAS...8H-5H RH OF 50-70%...AND PERHAPS SOME DIURNAL COMPONENT WARRANTS A CHANCE OF SHOWERS ACROSS NRN LOWER. ERN UPPER TOO FAR N OF UPPER LOW...AND WILL KEEP FORECAST DRY. WEDNESDAY...500 MB LOW/TROUGH WILL PUSH E THROUGH THE OHIO VALLEY (GFS SOLUTION QUITE A BIT FASTER THAN NAM). ASSUMING TROUGH MOVES EWD A BIT SLOWER THAN GFS...AND THAT COLDER AIR ALOFT REMAINS OVERHEAD...MODELS SUPPORT VT/S APPROACHING 30 BY AFTERNOON AS 8H WAA TAKES PLACE ACROSS NRN MI. MODEL SOUNDINGS SUPPORT ROUGHLY 800 J/KG CAPE BY AFTERNOON...AND WITH WEAK PRESSURE GRADIENT...LAKE BREEZES MAY PROVIDE NECESSARY FOCUS ACROSS E/SE PARTS OF FORECAST AREA FOR SOME SPOTTY AFTERNOON CONVECTION. OTHERWISE...PARTLY SUNNY EXPECTED. NO CHANGES MADE TO FORECAST BEYOND WEDNESDAY. SMITH && .APX...WATCHES/WARNINGS/ADVISORIES...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1018 AM CDT SUN SEP 3 2006 .UPDATE... UPDATED THE HAZARDOUS WX OUTLOOK TO REFLECT THE POSSIBILITY OF SOME BRIEF SEVERE WEATHER FROM RED WING AREA INTO WISCONSIN. RADAR HAS SHOWN SOME INCREASE IN STRENGTH IN THE FBL/OWA AREAS...AND SATELLITE DOES SHOW SOME SMALL BREAKS. ALL THIS AREA NEEDS IS A FEW DEGREES OF HEATING TO RESULT IN STRONGER ACTIVITY. BOUNDARY LOOPS FROM THE SFC LOW NEAR MITCHELL SD UP TOWARD AQP THEN MGG AND JUST NOW PAST MSP TO RST AREA. GIVEN THE SLOW MOVEMENT OF THE UPPER LOW...ONE MIGHT THINK THE EASTERN PORTION OF THIS BOUNDARY WILL JUST CONTINUE MOVING EAST AT THE SAME PACE AS IT HAS SINCE YESTERDAY MORNING...BUT THE 12Z NAM SHIFTS/REDEVELOPS IT EAST RATHER QUICKLY... REACHING MENOMONIE BY 18Z AND PAST EAU CLAIRE BY 21Z. RUC IS NOT AS AGRESSIVE AND IS MORE IN LINE WITH CURRENT CONDITIONS...THUS IS FAVORED. BUT RUC STILL IMPLIES BOUNDARY REACHING MENOMONIE AROUND 21Z. THIS TIMING WOULD MEAN THE RGK/LUM AREA WOULD SEE THE GREATEST CHC OF STORMS DURING THE EARLY TO MID AFTERNOON. BY 21Z THE BEST DIRECTIONAL SHEAR EXTENDS FROM RGK INTO WISC...SO THE 13Z SPC OUTLOOK DOES SEEM REASONABLE...THOUGH WE MAY NEED TO CONSIDER RGK AREA AND PEPIN COUNTY AS WELL. ANOTHER BAND OF PRECIP IN WESTERN IOWA MAY ALSO SNEAK INTO SC MN. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ TDK mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 902 PM EDT SUN SEP 3 2006 .SHORT TERM /REST OF TONIGHT/... NOCTURNAL INVERSION SETTING UP RAPIDLY PER REFLECTIVITY TRENDS. LITTLE IN THE WAY OF CLOUDINESS TO HINDER RADIATION AND SPREADS ARE GOING TO CONVERGE QUICKLY. AS SUCH...WILL BE ADDING FOG TO THE FORECAST AND REMOVING THE LINGERING SLIGHT CHANCE OF SHOWERS. WITH DEW POINTS IN THE UPPER 60S AND LOWER 70S...WILL RAISE THE OVERNIGHT MINS JUST A TOUCH AS WELL. && .PREV DISCUSSION... (ISSUED 315 PM EDT SUN SEP 3 2006) SYNOPSIS... A CUT-OFF LOW OVER THE NORTHERN PLAINS WILL DRIFT SLOWLY SOUTHEAST INTO THE MIDWEST AND OHIO VALLEY THROUGH MIDWEEK. WEAK LOW-LEVEL WARM AIR ADVECTION ALONG AN INVERTED SFC TROUGH EXTENDING FROM THE DEEP SOUTH...NORTH INTO THE CAROLINAS...WILL SERVE AS A FOCUS SHOWERS ON MONDAY...AHEAD OF A FRONTAL PASSAGE ON TUESDAY. SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... TONIGHT...REGIONAL DOPPLER NETWORK INDICATES SCATTERED SHOWERS HAVE DEVELOPED ACROSS THE SAVANNAH VALLEY IN A WEAK MOISTURE CONVERGENCE ZONE ALONG THE INVERTED TROUGH AXIS. THE RUC AND GFS SPREADS THIS MOISTURE CONVERGENCE AREA NORTH INTO WESTERN NORTH CAROLINA THIS EVENING AS WINDS VEER FROM THE SSE. EXPECT THE WARM AIR ADVECTION PATTERN TO RESULT MAINLY IN ENHANCED CLOUDINESS OVERNIGHT ACROSS MUCH OF THE CWA. THE EXCEPTION MAY BE IN THE IN THE FAR WESTERN CWA...WHERE BEST L0W-LEVEL CONVERGENCE IS EXPECTED TO SET DUE TO THE WEAK UPSLOPE COMPONENT FLOW AND WEAK SFC RIDGING BUILDING IN FROM THE NORTHWEST. KEPT A SLIGHT CHANCE POPS OVERNIGHT IN THE WESTERN PIEDMONT ONLY. ELSEWHERE...THERE IS A GOOD POTENTIAL FOR A STRATUS LAYER TO DEVELOP OVERNIGHT WITH SE TRAJECTORIES THROUGH THE BL ADVECTING ATLANTIC MARITIME MOISTURE. LOWS IN THE MID AND UPPER 60S. LABOR DAY...MID-LEVEL CAP BREAKS DOWN AS LARGE SCALE WARMING AND MOISTENING TAKES PLACE IN RESPONSE TO BACKING SW FLOW AS MID AND UPPER TROUGH DIGS SLOWLY SOUTHEAST. SHOWERS WILL BECOME MORE WIDESPREAD WITH AFTERNOON HEATING AND CONDITIONAL INSTABILITY PRESENT...FOCUSED ALONG INVERTED SFC TROUGH AXIS. HIGHEST POPS IN THE WEST ALONG UPSLOPE AND BEST LOW-LEVEL CONVERGENCE. HIGHS 82 TO 87. MONDAY NIGHT THROUGH TUESDAY NIGHT...PW'S INCREASE TO AROUND 2.0" WITH H5 HEIGHT FALLS AND UPPER LEVEL DIFFLUENCE PATTERN SPREADS EAST INTO THE CENTRAL APPALACHIANS AND THE CAROLINAS AS CLOSED LOW DIGS INTO THE OHIO VALLEY. THE GFS DEVELOPS A SURFACE WAVE ALONG THE INVERTED TROUGH AND DRAGS THE COLD FRONT ACROSS THE STATE TUESDAY AFTERNOON. CUT-OFF LOW LIFTS AND FILLS INTO AN OPEN SHORTWAVE TROUGH TUESDAY AFTERNOON TAKING MAIN VORT MAX AND PVA TO THE NORTH...HOWEVER SEVERAL VORT MINS. MOVE ACROSS LATE TUESDAY EVENING AND TUESDAY NIGHT. INSTABILITY IS MARGINAL TUESDAY AFTERNOON WITH WITH ML CAPE OF 800 TO 1200 J/KG WITH AROUND 25KTS OF BULK SHEAR. SHEAR INCREASES LATE TUESDAY EVENING...TRYING TO CATCH UP DEEP MOISTURE AND BEST INSTABILITY AS UPPER JET STREAK APPROACHES FROM THE WEST. EXPECT TO SEE A LINE OF SHOWERS WITH EMBEDDED THUNDERSTORMS TO MOVE THROUGH TUESDAY AFTERNOON ALONG THE COLD FRONT...THEN SCATTERED SHOWERS DEVELOP BEHIND THE FRONT TUESDAY NIGHT AND INTO WEDNESDAY MORNING AS UPPER DYNAMICS PASSES ACROSS THE AREA. CONTINUED THE GOOD CHANCE POPS MONDAY NIGHT INCREASING TO LIKELY TUESDAY AFTERNOON WITH DIMINISHING POPS TUESDAY NIGHT FROM WEST TO EAST TUESDAY NIGHT. FOLLOWED MOS GUIDANCE FAIRLY CLOSELY WITH HIGHS TUESDAY HIGHLY DEPENDENT ON CLOUD COVER AND ONSET OF SHOWERS. LONG TERM /WEDNESDAY THROUGH SUNDAY/... BULK OF H5 ENERGY AND MOISTURE LIFTS NORTH INTO THE NORTHEASTERN CONUS ON WEDNESDAY AS CLOSED LOW DAMPENS INTO OPEN SHORTWAVE TROUGH. MEAN LAYER RH DRIES OUT CONSIDERABLY BY WEDNESDAY MORNING AS 850 TROUGH MOVES THROUGH THE AREA AND WEAK SFC RIDGE BUILDS IN FROM THE WEST. HOWEVER...BASE OF LONGWAVE TROUGH REMAINS UPSTREAM OF CENTRAL NC THROUGH FRIDAY...KEEPING THE CWFA UNDER THE INFLUENCE OF A MOIST SW FLOW ALOFT AND A WEAK UPPER DIVERGENCE REGION EXTENDING DOWN THE EAST COAST. ILL-DEFINED SHORTWAVE ENERGY IN THE SW FLOW ALOFT IS PROBLEMATIC AND BEYOND THE FORECAST SKILL OF MODEL RESOLUTION. AS A RESULT...THERE IS LOW CONFIDENCE REGARDING POPS THURSDAY AND FRIDAY. FOR NOW WILL KEEP POPS IN THE SILENT 20 CATEGORY. TEMPERATURES THROUGH THE PERIOD WILL REMAIN AT OR BELOW NORMAL WITH ENHANCED CLOUDINESS FROM SW FLOW ALOFT AND NEGATIVE 500 HEIGHT ANOMALIES. AVIATION... WITH INCREASING MOISTURE AND DAYTIME HEATING SCT-BKN025 CU FIELD HAS DEVELOPED AVER MUCH OF THE AREA. SOME ISOLD LIGHT SHOWERS ARE POSSIBLE THIS EVENING AND OVERNIGHT MAINLY NEAR KINT...KGSO...KFAY AND KRWI. EXPECT STRATUS AND SOME FOG TO ALSO SET UP AFTER MIDNIGHT AND IFR CONDITIONS MAY DEVELOP IN MANY LOCATIONS OVER CENTRAL NC. CONDITIONS WILL IMPROVE WITH HEATING ON MONDAY BURNING OFF FOG AND STRATUS DECK. EXPECT ANOTHER DAY OF SCT-BKN035 WITH SCATTERED SHOWERS POSSIBLE. A BETTER CHANCE OF NUMEROUS SHOWERS AND THUNDERSTORMS WILL COME INTO THE FORECAST MONDAY NIGHT AND TUESDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...MLM nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 315 PM EDT SUN SEP 3 2006 .SYNOPSIS... A CUT-OFF LOW OVER THE NORTHERN PLAINS WILL DRIFT SLOWLY SOUTHEAST INTO THE MIDWEST AND OHIO VALLEY THROUGH MIDWEEK. WEAK LOW-LEVEL WARM AIR ADVECTION ALONG AN INVERTED SFC TROUGH EXTENDING FROM THE DEEP SOUTH...NORTH INTO THE CAROLINAS...WILL SERVE AS A FOCUS SHOWERS ON MONDAY...AHEAD OF A FRONTAL PASSAGE ON TUESDAY. && .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... TONIGHT...REGIONAL DOPPLER NETWORK INDICATES SCATTERED SHOWERS HAVE DEVELOPED ACROSS THE SAVANNAH VALLEY IN A WEAK MOISTURE CONVERGENCE ZONE ALONG THE INVERTED TROUGH AXIS. THE RUC AND GFS SPREADS THIS MOISTURE CONVERGENCE AREA NORTH INTO WESTERN NORTH CAROLINA THIS EVENING AS WINDS VEER FROM THE SSE. EXPECT THE WARM AIR ADVECTION PATTERN TO RESULT MAINLY IN ENHANCED CLOUDINESS OVERNIGHT ACROSS MUCH OF THE CWA. THE EXCEPTION MAY BE IN THE IN THE FAR WESTERN CWA...WHERE BEST L0W-LEVEL CONVERGENCE IS EXPECTED TO SET DUE TO THE WEAK UPSLOPE COMPONENT FLOW AND WEAK SFC RIDGING BUILDING IN FROM THE NORTHWEST. KEPT A SLIGHT CHANCE POPS OVERNIGHT IN THE WESTERN PIEDMONT ONLY. ELSEWHERE...THERE IS A GOOD POTENTIAL FOR A STRATUS LAYER TO DEVELOP OVERNIGHT WITH SE TRAJECTORIES THROUGH THE BL ADVECTING ATLANTIC MARITIME MOISTURE. LOWS IN THE MID AND UPPER 60S. LABOR DAY...MID-LEVEL CAP BREAKS DOWN AS LARGE SCALE WARMING AND MOISTENING TAKES PLACE IN RESPONSE TO BACKING SW FLOW AS MID AND UPPER TROUGH DIGS SLOWLY SOUTHEAST. SHOWERS WILL BECOME MORE WIDESPREAD WITH AFTERNOON HEATING AND CONDITIONAL INSTABILITY PRESENT...FOCUSED ALONG INVERTED SFC TROUGH AXIS. HIGHEST POPS IN THE WEST ALONG UPSLOPE AND BEST LOW-LEVEL CONVERGENCE. HIGHS 82 TO 87. MONDAY NIGHT THROUGH TUESDAY NIGHT...PW'S INCREASE TO AROUND 2.0" WITH H5 HEIGHT FALLS AND UPPER LEVEL DIFFLUENCE PATTERN SPREADS EAST INTO THE CENTRAL APPALACHIANS AND THE CAROLINAS AS CLOSED LOW DIGS INTO THE OHIO VALLEY. THE GFS DEVELOPS A SURFACE WAVE ALONG THE INVERTED TROUGH AND DRAGS THE COLD FRONT ACROSS THE STATE TUESDAY AFTERNOON. CUT-OFF LOW LIFTS AND FILLS INTO AN OPEN SHORTWAVE TROUGH TUESDAY AFTERNOON TAKING MAIN VORT MAX AND PVA TO THE NORTH...HOWEVER SEVERAL VORT MINS. MOVE ACROSS LATE TUESDAY EVENING AND TUESDAY NIGHT. INSTABILITY IS MARGINAL TUESDAY AFTERNOON WITH WITH ML CAPE OF 800 TO 1200 J/KG WITH AROUND 25KTS OF BULK SHEAR. SHEAR INCREASES LATE TUESDAY EVENING...TRYING TO CATCH UP DEEP MOISTURE AND BEST INSTABILITY AS UPPER JET STREAK APPROACHES FROM THE WEST. EXPECT TO SEE A LINE OF SHOWERS WITH EMBEDDED THUNDERSTORMS TO MOVE THROUGH TUESDAY AFTERNOON ALONG THE COLD FRONT...THEN SCATTERED SHOWERS DEVELOP BEHIND THE FRONT TUESDAY NIGHT AND INTO WEDNESDAY MORNING AS UPPER DYNAMICS PASSES ACROSS THE AREA. CONTINUED THE GOOD CHANCE POPS MONDAY NIGHT INCREASING TO LIKELY TUESDAY AFTERNOON WITH DIMINISHING POPS TUESDAY NIGHT FROM WEST TO EAST TUESDAY NIGHT. FOLLOWED MOS GUIDANCE FAIRLY CLOSELY WITH HIGHS TUESDAY HIGHLY DEPENDENT ON CLOUD COVER AND ONSET OF SHOWERS. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... BULK OF H5 ENERGY AND MOISTURE LIFTS NORTH INTO THE NORTHEASTERN CONUS ON WEDNESDAY AS CLOSED LOW DAMPENS INTO OPEN SHORTWAVE TROUGH. MEAN LAYER RH DRIES OUT CONSIDERABLY BY WEDNESDAY MORNING AS 850 TROUGH MOVES THROUGH THE AREA AND WEAK SFC RIDGE BUILDS IN FROM THE WEST. HOWEVER...BASE OF LONGWAVE TROUGH REMAINS UPSTREAM OF CENTRAL NC THROUGH FRIDAY...KEEPING THE CWFA UNDER THE INFLUENCE OF A MOIST SW FLOW ALOFT AND A WEAK UPPER DIVERGENCE REGION EXTENDING DOWN THE EAST COAST. ILL-DEFINED SHORTWAVE ENERGY IN THE SW FLOW ALOFT IS PROBLEMATIC AND BEYOND THE FORECAST SKILL OF MODEL RESOLUTION. AS A RESULT...THERE IS LOW CONFIDENCE REGARDING POPS THURSDAY AND FRIDAY. FOR NOW WILL KEEP POPS IN THE SILENT 20 CATEGORY. TEMPERATURES THROUGH THE PERIOD WILL REMAIN AT OR BELOW NORMAL WITH ENHANCED CLOUDINESS FROM SW FLOW ALOFT AND NEGATIVE 500 HEIGHT ANOMALIES. && .AVIATION... WITH INCREASING MOISTURE AND DAYTIME HEATING SCT-BKN025 CU FIELD HAS DEVELOPED AVER MUCH OF THE AREA. SOME ISOLD LIGHT SHOWERS ARE POSSIBLE THIS EVENING AND OVERNIGHT MAINLY NEAR KINT...KGSO...KFAY AND KRWI. EXPECT STRATUS AND SOME FOG TO ALSO SET UP AFTER MIDNIGHT AND IFR CONDITIONS MAY DEVELOP IN MANY LOCATIONS OVER CENTRAL NC. CONDITIONS WILL IMPROVE WITH HEATING ON MONDAY BURNING OFF FOG AND STRATUS DECK. EXPECT ANOTHER DAY OF SCT-BKN035 WITH SCATTERED SHOWERS POSSIBLE. A BETTER CHANCE OF NUMEROUS SHOWERS AND THUNDERSTORMS WILL COME INTO THE FORECAST MONDAY NIGHT AND TUESDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS... SHORT TERM...LOCKLEAR LONG TERM...LOCKLEAR AVIATION...JO nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1036 AM EDT SUN SEP 3 2006 .SHORT TERM /REST OF TODAY/... WEAK SURFACE HIGH PRESSURE CONTINUES TO PERSIST ACROSS THE AREA THIS MORNING AS FRONTAL BOUNDARY/TROUGH EXTENDS ACROSS SOUTHERN GEORGIA AND SOUTH CAROLINA. MOISTURE PROFILES AS WELL AS VERTICAL OMEGA FIELDS CONTINUE TO BE LESS THAN IMPRESSIVE FOR TODAY. THE LATEST DATA FROM THE GFS AND RUC SHOW BEST LIFT CENTERED ACROSS SOUTHERN SOUTH CAROLINA. SEE NO REASON TO DEVIATE FROM CURRENT SLIGHT CHANCE POPS WITH SLIGHTLY HIGHER VALUES ALONG THE COAST VIA SEA- BREEZE. TEMPERATURE AND DEW-POINT TRENDS LOOK GOOD. NO UPDATES. && .AVIATION... SOME MVFR CEILINGS POSSIBLE AT THE COASTAL TERMINALS THROUGH 18Z... OTHERWISE VFR TODAY WITH ISOLATED SHOWERS POSSIBLE. WINDS LIGHT AND VARIABLE 5 KNOTS BECOMING EAST TO SOUTHEAST 5-10 KNOTS BY 18Z. BROKEN VFR CEILINGS AND ISOLATED SHOWERS AT THE COASTAL TERMINALS OVERNIGHT SHOULD PREVENT DENSE FOG FROM FORMING. INLAND THOUGH GOOD PARAMETERS SETTING UP FOR DENSE FOG MONDAY MORNING WITH VLIFR EXPECTED BY 10Z. && .MARINE... MODELS NOT HANDLING THE SFC TROF OR THE POSSIBLE WEAK SFC LOW WELL OFF THE GA/SC COASTS VERY WELL...VIA LATEST MSAS. THIS HAS CAUSED MORE OF A NE WIND DIRECTION ACROSS THE WATERS AT THE MOMENT. SFC PG ALSO SLITELY TIGHTENED...ENUF TO GO AROUND 10 KT INSTEAD OF 5 TO 10. WILL VEER TO THE EAST THIS AFTERNOON DUE TO THE LINGERING OFFSHORE TROFFINESS. CULD POSSIBLY SEE SE LATER THIS AFTERNOON IF THE TROF WEAKENS ENUF. WILL GO WITH 2 TO 3 FT SEAS INTO TONIGHT. && .ILM WATCHES/WARNINGS/ADVISORIES... NC...NONE. SC...NONE. MARINE...NONE. && $$ SHORT TERM...SHK AVIATION...MRR MARINE...HOEHLER nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1137 AM EDT SUN SEP 3 2006 .SHORT TERM /REST OF TODAY/... KGSP 88-D SHOWS CONVECTION DEVELOPING ADJACENT TO THE SAVANNAH RIVER. LAPS SOUNDINGS INDICATE LOW LEVEL FLOW HAS BACKED TO A SOUTHEAST DIRECTION...WHICH WILL PROBABLY MAINTAIN LOWER CLOUDS AND KEEP ENOUGH LOW LEVEL LIFT IN THE WARM ADVECTION REGIME FOR SCATTERED SHOWERS IN THE SOUTHWEST CWFA. SO...WILL UPDATE TO INCREASE PROBABILITY OF PRECIPITATION TO SOLID CHANCE WESTERN UPSTATE/NORTHEAST GEORGIA...AND WILL ALSO INDICATE ISOLATED THUNDERSTORMS...WHERE THE OBSERVED SOUNDING ON THE PEACHTREE CITY SOUNDING SHOWED A WEAKER CAP. FIRST FEW FRAMES OF THE NEW NAM/WRF IMPLY THAT THE BETTER CONVERGENCE WILL SHIFT TO THE MOUNTAINS FOR THE AFTERNOON. && .PREV DISCUSSION... /ISSUED 1033 AM EDT SUN SEP 3 2006/ SHORT TERM /REST OF TODAY/... OBSERVED UPPER AIR SOUNDINGS FROM ACROSS THE REGION THIS MORNING SHOWS A MOIST LOWER 300 MB WITH A CAPPING INVERSION INDICATED...ESPECIALLY ACROSS THE NORTHERN CWFA. CAP SUSCEPTIBLE TO BREAKAGE IN OUR SOUTHERN CWFA LATER TODAY PER SOUNDING AT PEACHTREE CITY. UPPER AIR ANALYSIS INDICATED A LOW LEVEL CONVERGENCE ZONE IN VICINITY OF UPPER TROF AXIS ACROSS WEST GEORGIA/EASTERN ALABAMA WITH WEAK WARM ADVECTION. THE PEACHTREE CITY SOUNDING WAS NOTABLE FOR ITS WEAK SOUTHEAST FLOW IN THE LOWEST 4K FEET OR SO. AT THE SURFACE...AN INVERTED TROF CAN STILL BE ANALYZED ACROSS THE CENTRAL PART OF THE FORECAST AREA...THAT COULD ALSO ACT AS A FOCUSING MECHANISM FOR CONVECTION LATER TODAY. BOTH RUC AND FIRST FEW FRAMES OF THE NEW 12KM NAM/WRF SUPPORT SCATTERED CONVECTION DEVELOPING ALONG THE LEE OF THE APPALCHIANS LATER TODAY...AS UPPER TROF TO THE WEST DRAWS EVER CLOSER AND THE LOW LEVEL CONVERGENCE SHIFTS A BIT INTO OUR WESTERN FORECAST AREA. CURRENT FORECAST GRIDS SUPPORT CHANCE OF SHOWERS IN THE MOUNTAINS EAST INTO THE NORTH CAROLINA FOOTHILLS...WITH ISOLATED SHOWERS INDICATED ELSEWHERE. FEW THINGS TO CHANGE WITH THE MORNING UPDATE. WILL MAKE NO CHANGES TO PROBABILITIES OF PRECIPITATION OR AFTERNOON MAXES...WHICH SHOULD RANGE FROM 70S ACROSS HIGHER TERRAIN TO LOWER 80S NORTHERN FOOTHILLS AND SOME MID/UPPER 80S POSSIBLE IN THE EXTREME SOUTHERN CWFA PER LOW LEVEL THICKNESS SCHEME. COSMETIC CHANGES MADE TO SKY GRIDS TO ACCOUNT FOR RATHER WIDESPREAD CLOUD COVER AT PRESENT. PREV DISCUSSION... /ISSUED 254 AM EDT SUN SEP 3 2006/ SHORT TERM /TODAY THROUGH TUESDAY NIGHT/... HAVE BASED MOST OF THIS FORECAST PACKAGE ON THE GFS MODEL. THE NAM/WRF IS MUCH SLOWER THAN THE GFS/UKMET/ECMWF WITH AN UPPER LOW THAT APPROACHES THE TUE/WED. IT ALSO DEVELOPS A TROPICAL LOOKING LOW THAT IT BRINGS NORTH INTO EASTERN EARLY TUE. THIS FEATURE IS ABSENT ON THE GFS AND IS ALMOST CERTAINLY SPURIOUS. I/M NOT THRILLED WITH THE 00 UTC GFS MASS FIELDS EITHER...BUT I DO PREFER IT TO THE 00 UTC WRF. ISOLATED UPSLOPE SHOWERS WILL PERSIST THROUGH THE MORNING HOURS ALONG THE ESCARPMENT. CONVERGENCE OVER THE HIGH TERRAIN AND INCREASING DEEP LAYER RH VALUES WILL BE GOOD FOR LOW CHANCE POPS THIS AFTERNOON AND TONIGHT OVER MOST OF THE MOUNTAINS AND ADJACENT FOOTHILL LOCATIONS. GFS HAS AN INVERSION ABOVE 500MB...AND FOR THE MOST PART CONVECTIVE ELEMENTS WON/T BE MUCH HIGHER THAN 20KFT. THIS WILL RESULT IN MOSTLY SHOWERS DURING THE AFTERNOON HOURS AND OVERNIGHT. WENT CLOSE TO MAV MOS NUMBERS THESE PERIODS. THINKING IS ABOUT THE SAME FOR MON. LAYER RH/S ARE HIGHER YET AND GFS HAS MID TROPOSPHERIC WINDS INCREASING DURING THE AFTERNOON. THIS COUPLED WITH CONTINUED LLVL CONVERGENCE IS GOOD FOR HIGH CHANCE POPS MTNS AND WESTERN FOOTHILLS. THIS IS A LITTLE BELOW THE GENERALLY LIKELY MAV POPS ON MON. FORCING IS A BIT WEAK FOR ME TO BITE ON POPS THAT HIGH. THAT IS NOT THE CASE MON NIGHT AND TUE AS A STRONG RIGHT ENTRANCE REGION OF THE 250MB JET WORKS ITS WAY INTO THE REGION. THE GFS DEVELOPS STRONG UPPER DIVERGENCE ALONG AND JUST WEST OF THE HIGH TERRAIN...WITH CONSIDERABLE QPF. HPC WENT CLOSE TO THIS SOLUTION WITH THEIR DAY 2 QPF (12 UTC MON - 12 UTC TUE) BUT PUSHED THE QPF AXIS A BIT FARTHER EAST...OR RIGHT ACROSS THE SOUTHERN APPALACHIANS. THE GFS SHIFTS THE BEST LLVL CONVERGENCE RATHER QUICKLY EAST ON TUE...ESSENTIALLY REDEVELOPING THE SFC FRONT OVER THE EASTERN CAROLINAS. THIS LOOKS A BIT ODD...BUT I/LL GO WITH IT. THIS MEANS WE SHOULDN/T BE LOOKING AT A PROTRACTED HEAVY RAIN EVENT. OUR HEAVIEST RAIN THE PAST SEVERAL DAYS HAS BEEN ALONG THE I-77 CORRIDOR...WHICH LOOKS TO HAVE LESS OF A CHANCE OF SEEING HEAVY RAIN THIS TIME. THEREFORE...WL NOT ISSUE AN ESF WITH THIS PACKAGE. HOWEVER...A COUPLE INCHES OF RAIN IS NOT OUT OF THE QUESTION OVER THE MTNS AND FOOTHILLS MON NGHT AND TUE. LONG TERM /WEDNESDAY THROUGH SATURDAY/... NO CHANGES MADE AFTER TUE NIGHT. WE MAY NEED TO TRIM BACK POPS FOR THE WEDNESDAY PERIOD...BUT WILL WAIT FOR HPC/S INPUT ON THIS BEFORE MAKING ANY CHANGES TO THE EXTENDED. AVIATION... PRIMARY CONCERN FOR THE 06 UTC TAF PACKAGE IS LOW CIGS/VSBY THREAT THROUGH MID-MORNING. WEAK WAA PATTERN WILL CONTINUE THIS MORNING LIKELY LEADING TO CIG/VSBY RESTRICTIONS FOR THE UPSTATE TAFS AND KCLT AND HAVE HIGHLIGHTING THE PERIOD FROM 5 TO 9 AM FOR PREDOMINATE MVFR VSBYS AND OCNL IFR CIGS. KAVL IN THE TANK AT ISSUANCE AND GIVEN A LITTLE MIXING THIS MORNING...WOULD EXPECT OCNL IMPROVEMENT...BUT 1/4SM/100 FT CONDS SHOULD DOMINATE THROUGH SUNRISE. SHOWER THREAT THIS MORNING SHAPING UP TO BE TOO SPOTTY TO MENTION IN THE TAFS. LOW CIGS/VSBYS EXPECTED TO MIX OUT FROM 13-15 UTC. SCATTERED AFTERNOON SHOWER THREAT SHAPING UP ACRS THE MTNS/FTLHS...AND ALL THINGS BEING EQUAL I GUESS KAVL WOULD STAND THE BEST CHANCE OF SEEING A SHOWER...SO WILL LIMIT VCSH MENTION TO JUST KAVL. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SHORT TERM...SAB sc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1033 AM EDT SUN SEP 3 2006 .SHORT TERM /REST OF TODAY/... OBSERVED UPPER AIR SOUNDINGS FROM ACROSS THE REGION THIS MORNING SHOWS A MOIST LOWER 300 MB WITH A CAPPING INVERSION INDICATED...ESPECIALLY ACROSS THE NORTHERN CWFA. CAP SUSCEPTIBLE TO BREAKAGE IN OUR SOUTHERN CWFA LATER TODAY PER SOUNDING AT PEACHTREE CITY. UPPER AIR ANALYSIS INDICATED A LOW LEVEL CONVERGENCE ZONE IN VICINITY OF UPPER TROF AXIS ACROSS WEST GEORGIA/EASTERN ALABAMA WITH WEAK WARM ADVECTION. THE PEACHTREE CITY SOUNDING WAS NOTABLE FOR ITS WEAK SOUTHEAST FLOW IN THE LOWEST 4K FEET OR SO. AT THE SURFACE...AN INVERTED TROF CAN STILL BE ANALYZED ACROSS THE CENTRAL PART OF THE FORECAST AREA...THAT COULD ALSO ACT AS A FOCUSING MECHANISM FOR CONVECTION LATER TODAY. BOTH RUC AND FIRST FEW FRAMES OF THE NEW 12KM NAM/WRF SUPPORT SCATTERED CONVECTION DEVELOPING ALONG THE LEE OF THE APPALCHIANS LATER TODAY...AS UPPER TROF TO THE WEST DRAWS EVER CLOSER AND THE LOW LEVEL CONVERGENCE SHIFTS A BIT INTO OUR WESTERN FORECAST AREA. CURRENT FORECAST GRIDS SUPPORT CHANCE OF SHOWERS IN THE MOUNTAINS EAST INTO THE NORTH CAROLINA FOOTHILLS...WITH ISOLATED SHOWERS INDICATED ELSEWHERE. FEW THINGS TO CHANGE WITH THE MORNING UPDATE. WILL MAKE NO CHANGES TO PROBABILITIES OF PRECIPITATION OR AFTERNOON MAXES...WHICH SHOULD RANGE FROM 70S ACROSS HIGHER TERRAIN TO LOWER 80S NORTHERN FOOTHILLS AND SOME MID/UPPER 80S POSSIBLE IN THE EXTREME SOUTHERN CWFA PER LOW LEVEL THICKNESS SCHEME. COSMETIC CHANGES MADE TO SKY GRIDS TO ACCOUNT FOR RATHER WIDESPREAD CLOUD COVER AT PRESENT. && .PREV DISCUSSION... /ISSUED 254 AM EDT SUN SEP 3 2006/ SHORT TERM /TODAY THROUGH TUESDAY NIGHT/... HAVE BASED MOST OF THIS FORECAST PACKAGE ON THE GFS MODEL. THE NAM/WRF IS MUCH SLOWER THAN THE GFS/UKMET/ECMWF WITH AN UPPER LOW THAT APPROACHES THE TUE/WED. IT ALSO DEVELOPS A TROPICAL LOOKING LOW THAT IT BRINGS NORTH INTO EASTERN EARLY TUE. THIS FEATURE IS ABSENT ON THE GFS AND IS ALMOST CERTAINLY SPURIOUS. I/M NOT THRILLED WITH THE 00 UTC GFS MASS FIELDS EITHER...BUT I DO PREFER IT TO THE 00 UTC WRF. ISOLATED UPSLOPE SHOWERS WILL PERSIST THROUGH THE MORNING HOURS ALONG THE ESCARPMENT. CONVERGENCE OVER THE HIGH TERRAIN AND INCREASING DEEP LAYER RH VALUES WILL BE GOOD FOR LOW CHANCE POPS THIS AFTERNOON AND TONIGHT OVER MOST OF THE MOUNTAINS AND ADJACENT FOOTHILL LOCATIONS. GFS HAS AN INVERSION ABOVE 500MB...AND FOR THE MOST PART CONVECTIVE ELEMENTS WON/T BE MUCH HIGHER THAN 20KFT. THIS WILL RESULT IN MOSTLY SHOWERS DURING THE AFTERNOON HOURS AND OVERNIGHT. WENT CLOSE TO MAV MOS NUMBERS THESE PERIODS. THINKING IS ABOUT THE SAME FOR MON. LAYER RH/S ARE HIGHER YET AND GFS HAS MID TROPOSPHERIC WINDS INCREASING DURING THE AFTERNOON. THIS COUPLED WITH CONTINUED LLVL CONVERGENCE IS GOOD FOR HIGH CHANCE POPS MTNS AND WESTERN FOOTHILLS. THIS IS A LITTLE BELOW THE GENERALLY LIKELY MAV POPS ON MON. FORCING IS A BIT WEAK FOR ME TO BITE ON POPS THAT HIGH. THAT IS NOT THE CASE MON NIGHT AND TUE AS A STRONG RIGHT ENTRANCE REGION OF THE 250MB JET WORKS ITS WAY INTO THE REGION. THE GFS DEVELOPS STRONG UPPER DIVERGENCE ALONG AND JUST WEST OF THE HIGH TERRAIN...WITH CONSIDERABLE QPF. HPC WENT CLOSE TO THIS SOLUTION WITH THEIR DAY 2 QPF (12 UTC MON - 12 UTC TUE) BUT PUSHED THE QPF AXIS A BIT FARTHER EAST...OR RIGHT ACROSS THE SOUTHERN APPALACHIANS. THE GFS SHIFTS THE BEST LLVL CONVERGENCE RATHER QUICKLY EAST ON TUE...ESSENTIALLY REDEVELOPING THE SFC FRONT OVER THE EASTERN CAROLINAS. THIS LOOKS A BIT ODD...BUT I/LL GO WITH IT. THIS MEANS WE SHOULDN/T BE LOOKING AT A PROTRACTED HEAVY RAIN EVENT. OUR HEAVIEST RAIN THE PAST SEVERAL DAYS HAS BEEN ALONG THE I-77 CORRIDOR...WHICH LOOKS TO HAVE LESS OF A CHANCE OF SEEING HEAVY RAIN THIS TIME. THEREFORE...WL NOT ISSUE AN ESF WITH THIS PACKAGE. HOWEVER...A COUPLE INCHES OF RAIN IS NOT OUT OF THE QUESTION OVER THE MTNS AND FOOTHILLS MON NGHT AND TUE. LONG TERM /WEDNESDAY THROUGH SATURDAY/... NO CHANGES MADE AFTER TUE NIGHT. WE MAY NEED TO TRIM BACK POPS FOR THE WEDNESDAY PERIOD...BUT WILL WAIT FOR HPC/S INPUT ON THIS BEFORE MAKING ANY CHANGES TO THE EXTENDED. AVIATION... PRIMARY CONCERN FOR THE 06 UTC TAF PACKAGE IS LOW CIGS/VSBY THREAT THROUGH MID-MORNING. WEAK WAA PATTERN WILL CONTINUE THIS MORNING LIKELY LEADING TO CIG/VSBY RESTRICTIONS FOR THE UPSTATE TAFS AND KCLT AND HAVE HIGHLIGHTING THE PERIOD FROM 5 TO 9 AM FOR PREDOMINATE MVFR VSBYS AND OCNL IFR CIGS. KAVL IN THE TANK AT ISSUANCE AND GIVEN A LITTLE MIXING THIS MORNING...WOULD EXPECT OCNL IMPROVEMENT...BUT 1/4SM/100 FT CONDS SHOULD DOMINATE THROUGH SUNRISE. SHOWER THREAT THIS MORNING SHAPING UP TO BE TOO SPOTTY TO MENTION IN THE TAFS. LOW CIGS/VSBYS EXPECTED TO MIX OUT FROM 13-15 UTC. SCATTERED AFTERNOON SHOWER THREAT SHAPING UP ACRS THE MTNS/FTLHS...AND ALL THINGS BEING EQUAL I GUESS KAVL WOULD STAND THE BEST CHANCE OF SEEING A SHOWER...SO WILL LIMIT VCSH MENTION TO JUST KAVL. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SHORT TERM...44 sc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 900 PM EDT SUN SEP 3 2006 .DISCUSSION...FORECAST APPEARS TO BE GENERALLY ON TRACK PER LATEST RUC AND GFS GUIDANCE DATA. WILL UPDATE ZONES TO REMOVE EVENING WORDING WHERE NEEDED AND MAKE A FEW MINOR TWEAKS TO TEMPS AND SKY COVER. && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ LCM tn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO CO 407 AM MDT MON SEP 4 2006 .SHORT TERM... (TODAY AND TONIGHT) SHORT TERM CONCERNS INCLUDE EXTENT OF STRATUS ACROSS THE EASTERN PLAINS THIS MORNING ALONG WITH THE POSSIBILITY OF A FEW STRONG STORMS THIS AFTERNOON. CURRENT WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSIS INDICATES WEAK TO MODERATE NORTH TO NORTHWEST FLOW ACROSS THE STATE...AS OLD CUTOFF LOW CONTINUES TO SPIN OVER WESTERN IOWA ALONG WITH UPPER LEVEL RIDGING PERSISTING ACROSS THE GREAT BASIN AND INTERMOUNTAIN WEST. WATER VAPOR IMAGERY ALSO INDICATING A SHORT WAVE TROUGH ROTATING AROUND UPPER MIDWEST SYSTEM MOVING ACROSS SOUTHEAST WYOMING ATTM. AT THE SFC...WEAK TROUGH NEAR LHX KEEPING MOIST SOUTHERLY LOW LEVEL FLOW ACROSS THE FAR SE PLAINS WITH SATELLITE FOG PRODUCT INDICATING PATCHY STRATUS DEVELOPING ATTM. TODAY...NORTH TO NORTHWEST FLOW PERSISTS ACROSS THE REGION AS WESTERN IOWA UPPER LOW CONTINUES SLOWLY MOVE SOUTH AND EAST. EMBEDDED SHORT WAVE ACROSS WYOMING CONTINUES TO MOVE ACROSS EASTERN COLORADO THIS MORNING...ALLOWING FOR DEVELOPING ENHANCED UPSLOPE FLOW ACROSS THE EASTERN PLAINS THIS AFTERNOON AS SFC HIGH PRESSURE BUILDS ACROSS THE NORTHERN AND CENTRAL HIGH PLAINS. HAVE ADDED THE MENTION OF FOG ACROSS THE EASTERN PLAINS THIS MORNING...THOUGH LOOKS LIKE THE WEAK TROUGH NR LHX KEEPING JUST ENOUGH WEST TO NORTHWEST FLOW TO KEEP STRATUS AT BAY ACROSS THE I-25 CORRIDOR. SOME CONCERN THAT THE EARLY MORNING SUN ALONG WITH PASSING WAVE WILL PRODUCE ENOUGH PRESSURE FALLS ACROSS THE LOWER SLOPES OF THE EASTERN MTS FOR STRATUS ACROSS THE PLAINS TO BE SUCKED UP THE LOWER ARKANSAS VALLEY BEFORE IT BURNS OFF THROUGH THE LATE MORNING. AT ANY RATE...THE UPSLOPE FLOW COMBINED WITH WEAK LIFT FROM EMBEDDED WAVE...COULD TRIGGER ISOLATED THUNDERSTORMS ALONG THE EASTERN MOUNTAINS AND ADJACENT PLAINS. LATEST NAM RUNS KEEP A RIBBON OF 500-1000 J/KG OF CAPE UP AGAINST THE EAST SLOPES OF THE EASTERN MTS...AND COMBINED WITH BULK SHEARS AROUND 40 KTS...COULD SEE SOME ISOLATED STRONG STORMS THROUGH THE AFTERNOON AND EARLY EVENING...WITH GUSTY WINDS TO 45 MPH AND HAIL THE MAIN THREATS. MODEL SOUNDINGS INDICATING HEALTHY CAP IN PLACE ACROSS THE FAR EASTERN PLAINS AND HAVE KEEP THESE AREAS DRY. OUT WEST...DRIER AIR MAY HAMPER CONVECTION AGAIN TODAY...THOUGH WILL KEEP CURRENT ISOLATED POPS ACROSS MAINLY THE SW MTS AND SAN LUIS VALLEY. TONIGHT...NORTHWEST FLOW ALOFT CONTINUES ACROSS THE REGION WITH ANY CONVECTION THE FIRES QUICKLY DIMINISHING AFTER SUNSET. MODELS CONTINUE TO INDICATE MOIST LOW LEVEL UPSLOPE ACROSS THE PLAINS...AND WILL HAVE TO WATCH FOR POSSIBLE STRATUS DEVELOPMENT ONCE AGAIN. -MW .LONG TERM... (TUESDAY THROUGH NEXT MONDAY) AMPLIFIED UPPER FLOW PERSISTS THROUGH MID-WEEK...THEN GRADUALLY FLATTENS AS UPPER MIDWEST CUT-OFF EJECTS EASTWARD. GENERAL N-NW UPPER FLOW TUESDAY AND WEDNESDAY SHOULD KEEP MOST MOISTURE AND INSTABILITY SUPPRESSED SOUTH OF THE STATE...THOUGH ENOUGH MOISTURE LINGERS OVER THE MTS FOR ISOLATED AFTERNOON AND EVENING TSRA...WITH PERHAPS A STORM OR 2 ALONG DRIFTING ONTO THE PLAINS WED AS FLOW BECOMES A LITTLE MORE NORTHWEST. MAX TEMPS TUE AND WED SHOULD WARM TO NEAR SEASONAL LEVELS AS 700 MB THERMAL TROUGH MOVES EASTWARD. AIR MASS LOOKS TO MOISTEN ON THURSDAY AS FLOW FLATTENS...WITH PERHAPS SOME MINOR CONTRIBUTION FROM REMNANTS OF T.S. JOHN AS IT WANDERS THROUGH THE SOUTHWEST US. GFS SUGGESTS NICE S/W TROUGH AND JET STREAK WILL AID CONVECTION ON THU...THOUGH BEST DYNAMICS MAY BE JUST SOUTH OVER NM AND THE TEXAS PANHANDLE. LOOKS LIKE ANOTHER SYSTEM COMES THROUGH ON SATURDAY...WHICH SHOULD INCREASE PRECIP CHANCES ONCE AGAIN. AFTER WED...A VERY SLIGHT DOWNWARD TREND IN MAX TEMPS LOOKS LIKELY...AS HEIGHTS FALL AND MOISTURE INCREASES. MADE SOME UPWARD ADJUSTMENTS TO MAX TEMPS TUE/WED...WITH VERY MINOR TWEAKS TO REMAINING GRIDS. --PETERSEN && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 23/10 co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 229 AM MDT MON SEP 4 2006 .DISCUSSION...FORECAST CONCERNS WILL BE HIGH TEMPERATURES TODAY... VERY SMALL CHANCE OF PRECIPITATION THIS AFTERNOON AND EVENING CLOSE TO THE EXTREME WESTERN PORTION OF OUR AREA...THEN HOW MUCH IT WARMS UP ON TUESDAY AND WEDNESDAY...AND FOLLOWED BY PRECIPITATION CHANCES MID TO LATE IN THE WEEK. SATELLITE SHOWING AN AMPLIFIED PATTERN FROM THE EASTERN PACIFIC INTO THE WESTERN ATLANTIC. TROUGH NEAR THE WEST COAST HAS DEEPENED AND CAUSED DOWNSTREAM RIDGE TO BUILD. THIS HAS BEGUN TO SLOWLY PUSH SYSTEM OVER IOWA SLOWLY EAST SOUTHEAST. DECENT SHORTWAVE TROUGH IS ROTATING AROUND THE BACKSIDE OF THIS SYSTEM...AND IS MOVING INTO NORTHEAST COLORADO. BECAUSE OF THIS SHORTWAVE TROUGH...COLD FRONT WITH REINFORCING SHOT OF COOL AIR MOVING THROUGH/INTO THE AREA. AT JET LEVEL...AT 00Z THE UKMET DID A LITTLE BETTER THAN THE GFS AND NAM/WRF ON JET SEGMENT JUST TO OUR SOUTH. HOWEVER...BY 06Z THE GFS WAS DOING SLIGHTLY BETTER. AT MID LEVELS...MODELS CAPTURED MAIN FEATURES WELL. THE RUC DID BEST ON SHORTWAVE TROUGH ROTATING IN WITH THE GFS AND NAM/WRF NOT TOO BAD. HEIGHT ANALYSIS WOULD SUPPORT THE GFS SLIGHTLY OVER THE UKMET/ECMWF. THE GFS TENDED TO BE GOOD ON MOISTURE ABOVE 700 MB BUT WAS TOO WET AT THAT LEVEL WITH THE NAM BETTER. AT LOW LEVELS...THE MODELS TENDED NOT TO HAVE THE STRONGER SURFACE RIDGING FAR ENOUGH WEST. EVENTUALLY THE NAM AND ECWMF LOOK TO GRAB ONTO THIS IDEA. THE NAM LOOKED TO HAVE A BETTER DEPICTION OF THE LOW LEVEL MOISTURE AND KEPT THE LOW LEVEL MOISTURE AXIS FURTHER WEST WITH TIME. MODELS WERE CLOSE ON TEMPERATURES. BUT HAVE TO GIVE THE EDGE TO THE GFS. WILL TEND TO FOLLOW A BLEND OF THE MODELS BASED ON THEIR STRENGTHS AND WEAKNESSES SHOWN IN THE INITIAL ANALYSIS AND KNOWN BIASES. OVERALL WILL TEND TOWARD A DRIER AND COOLER SOLUTION. TODAY/TONIGHT...EAST TO NORTHEAST WINDS TO SPREAD OVER THE AREA BEHIND THE FRONT. WILL HAVE TO WATCH FOR STRATUS OR FOG FORMATION FOR AS LONG AS POSSIBLE. DEWPOINT DEPRESSIONS ARE STARTING TO GET SMALL...AND AM SEEING SOME VERY SLIGHT REDUCTIONS IS VISIBILITY ALREADY. AT THIS TIME...WILL INSERT SOME PATCHY MORNING FOG. EASTERLY WINDS AND UPSLOPE WINDS SHOULD KEEP TEMPERATURES IN AT LEAST THE 70S. LAPSE RATES ALOFT WILL CREATE SOME CLOUD COVER IN THE AFTERNOON AS WELL. PLAN ON GOING NEAR THE COOLER GUIDANCE. MAV HAS BEEN CONSISTENT WITH TEMPERATURES THE LAST COUPLE OF RUNS AS WELL. SPC HAS PLACED AREA JUST TO OUR WEST IN A GENERAL OUTLOOK FOR THUNDERSTORMS. AREA STAYS IN STRONG SUBSIDENCE FROM THE JET THROUGH THE PERIOD. IT WOULD APPEAR THAT ABOVE MENTIONED SHORTWAVE WILL MOVE THROUGH EARLY IN THE DAY...AND MAY NOT BE A FACTOR. MID LEVEL MOISTURE IS MARGINAL AT BEST...AND LOOKS TO DECREASE AS THE DAY WHERES ON. ALSO LOW LEVEL UPSLOPE DOES NOT LOOK TERRIBLY STRONG. SATELLITE SHOWING NO CLOUD COVER TO OUR NORTHWEST NOW. HOWEVER... ENOUGH MOISTURE AND DECENT MID LEVEL LAPSE RATES WILL PROBABLY CAUSE SOME AFTERNOON CU TO DEVELOP...AND THAT SHOULD BE IT. ALSO 0-6 KM WIND IS ALSO NEARLY OUT OF THE NORTH. WILL KEEP FORECAST DRY FOR NOW. HOWEVER...WILL TELL DAY SHIFT TO KEEP A CLOSE EYE ON IT. LITTLE TO NO CLOUD COVER TONIGHT AND LIGHT WINDS. PLAN ON GOING NEAR TO SLIGHTLY BELOW GUIDANCE. TUESDAY/TUESDAY NIGHT...VERY LIGHT SURFACE WIND FIELD EXPECTED DURING THE DAY. AS SURFACE RIDGE MOVES AWAY...EXPECT EAST TO SOUTHEAST WINDS AND RECYCLED COOL AIR TO STAY OVER THE AREA DURING THE DAY. THIS WILL BE BALANCED BY WHAT LOOKS LIKE A LOT OF SUNSHINE. AGAIN PLAN ON GOING NEAR COOLER GUIDANCE MAXES. SOUNDINGS SHOW A DRIER AIR MASS IN PLACE OVER THE PREVIOUS DAY WITH MAIN LOW LEVEL MOISTURE AXIS TOO THE WESTE. ANYTHING THAT FORMS IN THE NORTHERLY FLOW ALOFT SHOULD STAY TO THE WEST OF THE AREA. WILL KEEP IT DRY. WEDNESDAY/WEDNESDAY NIGHT...EASTERN UPPER LOW LOOKS TO FINALLY GET MOVING RIGHT BEFORE OR DURING DURING THE DAY. RETURN FLOW BEGINS...ESPECIALLY IN THE WEST...AND THE WARM UP LOOKS TO START. HOWEVER...THAT SHOULD BE TEMPERED SOMEWHAT BY SLIGHT UPSLOPE COMPONENT. PLAN ON GOING NEAR THE COOLER GUIDANCE. MODELS DIFFER ON THE DETAILS ON THIS PERIOD. EACH HAS THE RIDGE BROKEN DOWN DIFFERENTLY WITH SOME SHORTWAVES COMING THROUGH. MODEL DO AGREE THAT THE FLOW ALOFT WILL BE NORTHWEST. THAT COMBINED WITH RETURN FLOW MAKES ME A LITTLE NERVOUS. RETURN OF DECENT LOW LEVEL MOISTURE AND AVAILABLE MID LEVEL MOISTURE IS ALSO IN QUESTION. THE NAM IS MORE AGRESSIVE WITH THE ABOVE 700 MB MOISTURE WHERE THE GFS IS DRIER. THE GFS IS TOO WET AT LOWER LEVELS WITH THE NAM MORE APPROPRIATE. SOME JET LIFT LOOKS TO BE CLOSE TO OVER THE SOUTHERN PORTION OF THE FORECAST AREA DURING THE LATE AFTERNOON AND OVERNIGHT HOURS. WILL ALSO VERY LOW 0-6 KM WINDS. BELIEVE ANYTHING THAT FORMS WILL STAY OUT TO THE WEST. AT THIS TIME WILL PUT IN A SLIGHT CHANCE IN THE FAR WESTERN PORTION OF THE AREA. RIGHT REAR QUADRANT DEVELOPS/MOVES OVER THE SOUTHERN THIRD TO HALF OF THE FORECAST AREA THURSDAY AFTERNOON AND NIGHT. THE GFS AND ECMWF SHOWING WEAK NORTHWEST FLOW ALOFT CONTINUING BUT ONCE AGAIN DIFFER ON HOW MUCH THE RIDGE IS BROKEN DOWN. BECAUSE OF THE DIFFERENCES SHOWN HERE...AND THE UNCERTAINTY WHAT WILL HAPPEN ON WEDNESDAY AFTERNOON AND NIGHT...WILL KEEP THIS PERIOD DRY. DAY FORECASTER WILL HAVE TO LOOK AT THE WEDNESDAY INTO THURSDAY PERIOD CLOSELY AGAIN. SO NO CHANGES ARE PLANNED IN THE 4 TO 7 DAY PERIOD AT THIS TIME. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ BULLER ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 341 AM EDT MON SEP 4 2006 .SYNOPSIS... 07Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED UPPER LOWS OVER WESTERN IOWA AND SE ONTARIO AND AN UPPER LEVEL RIDGE COVERING MUCH OF THE ROCKIES INTO SOUTH CENTRAL CANADA AND EASTWARD INTO NORTHERN ONTARIO. BETWEEN THE TWO UPPER LOWS...A WEAK SHRTWV CAN BE SEEN OVER NORTHERN LAKE MICHIGAN. DESPITE THE PRESENCE OF THIS SHRTWV...THE ONLY NOTABLE EFFECT OF IT IS AN EXPANSIVE AREA OF MID AND HIGH CLOUDS COVERING MUCH OF UPPER MICHIGAN AND LAKE SUPERIOR. THESE CLOUDS ARE ALSO A RESULT OF ISENTROPIC LIFT WHICH CAN BE SEEN ON THE 315-320K SURFACES. RADAR IMAGERY DOES INDICATE THE PRESENCE OF WHAT SHOULD BE SOME SHOWERS...BUT DRY AIR IN THE LOW LEVELS AS SEEN ON THE 02Z TAMDAR SOUNDING FROM SAWYER HAS KEPT THE RAIN AS VIRGA. BECAUSE OF THE CLOUDS...TEMPERATURES HAVE STAYED UP WITH READINGS MAINLY IN THE 50S AT THE PRESENT TIME. COOLER TEMPS ALONG WITH DRIER AIR AND CLEAR SKIES IS SEEN TO THE NORTH OVER NORTHERN ONTARIO UNDERNEATH BOTH THE UPPER LEVEL RIDGE AND A SURFACE HIGH PRESSURE RIDGE. THE 00Z INL SOUNDING...WHICH WAS STILL A BIT IN THE HIGH CLOUDS...SHOWED PRECIPITABLE WATER OF 0.58 INCHES ALONG WITH DEWPOINT DEPRESSIONS OF 10-20C FROM THE SURFACE TO 400 MB. SOME LOCATIONS IN NORTHERN ONTARIO YESTERDAY AFTERNOON HAD DEWPOINTS DROPPING INTO THE UPPER 30S DUE TO MIXING. LAST ITEM TO NOTE IS A STRONG SHRTWV OVER THE NE PACIFIC WHICH IS INCREASING THE UPPER LEVEL RIDGING OVER WESTERN CANADA. THE BUILDING RIDGING COMBINED WITH THE PRESENCE OF THE TWO UPPER LOWS AND ALREADY SOME WEAK TROUGHING OVER HUDSON BAY WILL LIKELY TRANSLATE INTO TROUGHING OVER EASTERN CANADA...WHICH IS WHAT THE MODELS HAVE BEEN PREDICTING THE LAST FEW DAYS. && .SHORT TERM (TODAY AND TONIGHT)... NAM SHOWS THE CLOSED 500 MB LOW OVER WRN IA HEADING SE WITH THE REMAINS OF ERNESTO CONTINUING TO HEAD EAST. THE DEFORMATION ZONE FROM THE CLOSED 500 MB LOW SHOULD REMAIN TO THE SOUTH OF THE CWA TODAY. NAM SHOWING WEAK TO NEUTRAL 850-500 MB Q-VECTOR CONVERGENCE OVER THE CWA THROUGH TONIGHT WITH DEEP MOISTURE REMAINING TO THE SOUTH AND EAST OF THE CWA. GFS SHOWS ABOUT THE SAME THING AND WILL REMOVE POPS FOR TODAY FOR THE CWA AND GO DRY. FOR TEMPERATURES... WENT SLIGHTLY WARMER THAN FORECASTED TODAY AS CLOUD COVER WILL BE THERE...BUT WILL NOT PREVENT A FILTERED SUNSHINE TO TAKE PLACE AND SHOULD HAVE NO PROBLEM GETTING TO THE MID 70S AS IT GOT THAT WARM YESTERDAY. FOR TONIGHT...WENT COLDER THAN WHAT WAS FORECASTED AS CLOUDS WILL BE DECREASING AND LIGHT WINDS AND THIS SETS UP A GOOD RADIATIONAL COOLING NIGHT IN STORE. COULD BE SOME 30S FOR LOWS TONIGHT IN THE TYPICAL COLD SPOTS. THERE WILL ALSO BE A THREAT OF SOME PATCHY FOG WITH IDEAL RADIATIONAL COOLING SETTING UP WITH TEMPERATURES DROPPING DOWN TO THE DEW POINTS AND THINK GROUND FOG WILL HAVE NO TROUBLE FORMING. .LONG TERM (TUESDAY INTO THE WEEKEND)... TUESDAY...UPPER LEVEL RIDGE OVER NORTHERN ONTARIO IS PROGGED TO BE LOCATED OVER UPPER MICHIGAN FOR MUCH OF THE DAY. HOWEVER...THIS RIDGE WILL BE WEAKENING AS A RESULT OF AMPLIFICATION TAKING PLACE TO THE TROUGH OVER HUDSON BAY. THE AMPLIFICATION IS CAUSED BY A FEW SHRTWVS MOVING SOUTHEASTWARD. THESE SHRTWV WILL CAUSE A COLD FRONT...PRESENTLY IN NORTHERN MANITOBA....TO MOVE SOUTHWARD ACROSS LAKE SUPERIOR IN THE AFTERNOON...REACHING THE KEWEENAW PENINSULA BY 00Z. BECAUSE THE AIRMASS IS DRY AHEAD OF THE FRONT...AND THERE IS LITTLE IF ANY DYNAMICAL FORCING...MODELS DEPICT VERY FEW CLOUDS ALONG OR AHEAD OF THE FRONT. THEREFORE THE MAIN INFLUENCE IN THE FRONT IS EXPECTED TO BE COOLER TEMPERATURES AND INCREASING NE WINDS. WINDS WILL LIKELY TURN TO THE NORTH ACROSS MUCH OF UPPER MICHIGAN EVEN BEFORE THE FRONT...BUT THIS IS DUE TO LAKE BREEZES. 850MB TEMPS AROUND 11C AND PLENTY OF SUNSHINE SHOULD ALLOW TEMPERATURES TO CLIMB WELL INTO THE 70S. TUESDAY NIGHT AND WEDNESDAY...MODELS SHOW THE COLD FRONT CROSSING ALL OF UPPER MICHIGAN DURING THE NIGHT WHILE HIGH PRESSURE BUILDS SOUTHEAST FROM NORTHERN ONTARIO. THIS HIGH SHOULD BE CENTERED OVER UPPER MICHIGAN AT 00Z THU. AGAIN...AS THE FRONT CROSSES...I AM NOT EXPECTING MUCH CLOUD COVER ALONG OR AHEAD OF IT DUE TO DRY AIR. THE AIRMASS BEHIND IT IS ALSO QUITE DRY...NOTED BY PRECIPITABLE WATER OF 0.25-0.5 INCH OVER EASTERN LAKE SUPERIOR AT 12Z WED. HOWEVER... 925-950MB RH PROGS FROM THE NAM INDICATE THE POSSIBILITY OF SOME UPSLOPE LOW CLOUDS TO DEVELOP AFTER MIDNIGHT AND PERSIST INTO WEDNESDAY MORNING BEFORE MIXING OUT. THEREFORE WILL CONTINUE A PARTLY CLOUDY FORECAST. IT SHOULD BE NOTED THAT MUCH OF THE DRY AIR IS PROGGED TO STAY OVER EASTERN LAKE SUPERIOR...EASTERN UPPER MICHIGAN AND EASTERN ONTARIO. TEMPERATURES TUESDAY NIGHT WILL STAY UP ALONG THE LAKE SUPERIOR SHORELINE THANKS TO THE INCREASE OF WINDS BEHIND THE FRONT. INTERIOR LOCATIONS OVER WESTERN UPPER MICHIGAN LOOK LIKE THEY MAY DECOUPLE...THOUGH...AND THIS IS REFLECTED BY MAV AND MET GUIDANCE SHOWING LOWS THERE IN THE 40S. ALTHOUGH NE WINDS DECREASE ON WEDNESDAY...IT APPEARS THAT LAKE BREEZES WILL FORM IN THE AFTERNOON...SO LAKE SUPERIOR SHORELINE AREAS SHOULD REMAIN COOL. HOWEVER...SUNSHINE AND 850MB TEMPS STILL 10-11C WILL ALLOW OTHER PLACES TO CLIMB AT LEAST INTO THE LOW OR MID 70S. WEDNESDAY NIGHT AND THURSDAY...MODELS INDICATE ANOTHER STRONG SHRTWV MOVING SOUTHEAST ACROSS HUDSON BAY ON WEDNESDAY...RESULTING IN ANOTHER COLD FRONTAL BOUNDARY...WHICH SHOULD BE SITUATED OVER NORTHERN LAKE WINNIPEG AT 00Z THU. THE 00Z NAM IS QUICKEST IN BRINGING THIS BOUNDARY INTO UPPER MICHIGAN (12Z THU). HOWEVER...THE GFS/UKMET AND PAST FEW ECMWF RUNS SUGGEST A SLOWER SCENARIO BECAUSE OF ANOTHER SHRTWV DROPPING DOWN INTO MANITOBA WHICH DEVELOPS A LOW PRESSURE AREA OVER LAKE WINNIPEG. WILL DISCOUNT THE NAM AND FOLLOW THE MAJORITY WHICH ALSO FOLLOWS CONTINUITY. THEREFORE THE HIGH PRESSURE AREA WHICH WAS OVER THE AREA WEDNESDAY WILL DROP SOUTH INTO THE OHIO VALLEY. RETURN FLOW ON THE BACK SIDE OF THE HIGH IS NOT FORECAST TO BE PARTICULARLY STRONG...SO INTERIOR LOCATIONS MAY DECOUPLE AGAIN...RESULTING IN SOME READINGS NEAR 50. LAKE SUPERIOR SHORELINE AREAS WILL STAY WARMER SINCE THE RETURN FLOW DOWNSLOPES AND ADDITIONAL HELP FROM LAND BREEZES. ON THURSDAY...THE GFS/UKMET/ECMWF SHOW THE MANITOBA SHRTWV MOVING INTO NW ONTARIO AND THE SURFACE COLD FRONT REACHING THUNDER BAY AND DULUTH BY 00Z. THERE IS SOME ISENTROPIC LIFT AHEAD OF THE FRONT OVER UPPER MICHIGAN... HOWEVER CONDENSATION PRESSURE DEFICITS ARE QUITE LOW. THEREFORE IF ANYTHING DEVELOPS...IT SHOULD ONLY BE A FEW MID CLOUDS. THESE CLOUDS SHOULD NOT INHIBIT HEATING THAT MUCH...AND WITH SW LOW LEVEL FLOW AND 850MB TEMPS AROUND 14C...TEMPERATURES AT LEAST IN THE UPPER 70S ARE LIKELY. MUCH MORE MOISTURE IS SEEN ON RH PROGS FROM THE GFS ALONG AND BEHIND THE FRONT...BUT THIS WILL NOT AFFECT THE AREA UNTIL THURSDAY NIGHT. EXTENDED...00Z ECMWF/UKMET/GFS ARE ALL IN GOOD AGREEMENT SHOWING THE COLD FRONT CROSSING UPPER MICHIGAN THURSDAY NIGHT INTO FRIDAY MORNING WITH ANOTHER PERIOD OF BREEZY NE WINDS BEHIND IT. ALONG AND AHEAD OF THE FRONT...GFS SOUNDINGS INDICATE SOME ELEVATED CAPE (500 J/KG OR SO)...SO THE THUNDERSTORM CHANCE STILL LOOKS GOOD. PLENTY OF LOW LEVEL MOISTURE BEHIND THE FRONT ALONG WITH THE 500MB SHRTWV MOVING ACROSS ALSO SUPPORTS THE NEED FOR CHANCES OF SHOWERS. THE EXTENT OF COLD AIR COMING IN BEHIND THE FRONT IS UNCERTAIN...THOUGH. THE GFS AND UKMET ARE IN EXCELLENT AGREEMENT WITH REGARDS TO SEA LEVEL PRESSURE AND 500MB HEIGHT FIELDS...THEREFORE WOULD NOT EXPECT THEIR THERMAL FIELDS TO BE ALL THAT DIFFERENT. IN THE CASE OF THE GFS...IT SUGGESTS 850MB TEMPS OF -2C MOVING ACROSS LAKE SUPERIOR AT 12Z SAT WITH PLENTY OF LOW LEVEL MOISTURE TO SUPPORT SOME LAKE EFFECT RAIN. HOWEVER...THE 00Z ECMWF HAS TRENDED WARMER...ONLY SHOWING 850MB TEMPS DROPPING TO 4C AT MOST...WHICH IS MARGINAL FOR LAKE EFFECT RAIN. BECAUSE THE GFS AND UKMET HAVE BEEN SHOWING THIS COLD AIR MASS MOVING ACROSS...AND MORE LOW LEVEL MOISTURE...HAVE DECIDED TO PUT IN 30 PERCENT CHANCES OF RAIN FOR FRIDAY NIGHT AND SATURDAY WITH THE POSSIBILITY OF LAKE EFFECT AND/OR DAYTIME INSTABILITY SHOWERS. BY SATURDAY NIGHT...SKIES SHOULD CLEAR OUT...ALLOWING TEMPERATURES TO FALL QUICKLY. IF THE GFS/UKMET SOLUTION IS RIGHT...WE COULD BE LOOKING AT A WIDESPREAD INLAND FROST. HOWEVER...WITH THE ECMWF SUGGESTING A WARMER SCENARIO...HAVE DECIDED NOT TO GO TOO COLD YET. IT SHOULD BE NOTED THAT AT LEAST AT OUR OFFICE...THE AVERAGE FIRST OCCURRENCE OF AT OR BELOW FREEZING CONDITIONS IS NOT UNTIL SEPTEMBER 21. NO MATTER WHAT MODEL TURNS OUT CORRECT...THE WEEKEND WILL BE COOLER THAN WHAT IT HAS BEEN THIS WEEK. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ GM (SHORT-TERM) AJ (LONG-TERM) mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI 410 AM CDT MON SEP 4 2006 .DISCUSSION...FORECAST FOCUS ON PRECIP COVERAGE TODAY THRU TUESDAY ALONG WITH TEMPERATURE TRENDS. 00Z UA ANALYSIS INDICATED 500MB CLOSED LOW CNTRD OVER NWRN IA...WITH WV IMAGERY SHOWING SEVERAL DISTINCT SHORTWAVES ROTATING AROUND CORE OF LOW. FIRST S/W ROTATING THRU SRN WI ATTM (06-07Z)...WITH SECOND S/W PIN-WHEELING THROUGH SWRN IA. 250MB ANALYSIS DEPICTING NICE DIFFLUENT FLOW OVER SRN WI...WITH PROFILER NETWORK SHOWING AN IMPRESSIVE 100+KT 250MB JET PUNCHING ACRS NRN MI/CNTRL IL...PLACING US IN FAVORABLE LEFT EXIT REGION. LOCAL RADAR MOSAIC SHOWING INITIAL ECHOS DYING OVR SRN WI...WITH REDEVELOPMENT ONGOING OVER CNTRL/NRN IL. ALSO SEEING SOME AREAS OF FOG DEVELOP ONCE AGAIN THIS MORNING...HOWEVER DUE TO ADDITIONAL CLOUDINESS...LOWEST VSBYS CONFINED TO FAR WRN CWA WHERE A FEW BREAKS IN THE CLOUDS ARE OCCURRING. OVERALL...LITTLE CHANGE IN THINKING FROM THE PAST COUPLE DAYS. GFS/WRF/RUC ALL IN GOOD AGREEMENT IN TRACKING PESKY UPR LOW FROM NEAR KDSM AT 12Z MON..TO KMLI BY 00Z TUE...TO KSPI BY 12Z TUE. GFS HAS BEEN MOST CONSISTENT IN HANDLING THIS FEATURE PAST SEVERAL DAYS...SO WILL CONTINUE TO RELY ON IT WRT MASS FIELDS. AS SUCH...COMBINATION OF H5-H3 Q-CONVERGENCE/PVA...AGEOSTROPHIC CIRCULATION IN LEFT EXIT REGION OF UPR JET...AND LOW LVL MSTR CONVERGENCE SHOULD PROVIDE ADEQUATE SYNOPTIC LIFT FOR SHOWERS/TSTMS TODAY. DECIDED TO GO CATEGORICAL POPS (80%) EVERYWHERE EXCEPT FOR THE FAR NRN TIER OF COUNTIES...WHERE LIKELY POPS REMAIN...AND THIS MATCHES UP WELL WITH BOTH MOS POPS...AND SREF PROBABILISTIC FORECASTS. BIGGER QUESTION FOR TODAY WILL BE POSSIBILITY OF SEVERE STORMS? GFS STILL TRACKING COLDEST 500MB TEMPS JUST SOUTH OF WI/IL BORDER...HOWEVER STEEP 700-500MB LAPSE RATES NEAR 7C/KM...MLCAPES OF 500-1000 J/KG...AND A LOW WET BULB ZERO HEIGHT OF 7-7.5K FEET ARE ALL FAVORABLE PARAMETERS FOR HAIL (AN ISOLATED WEAK TORNADO IS ALSO POSSIBLE WITH THESE COLD CORE SYSTEMS). WE BELIEVE THE AMOUNT OF SUNSHINE WILL ULTIMATELY DICTATE POSSIBILITY OF SEVERE STORMS...AND AM A BIT CONCERNED WE MAY BE SOCKED IN WITH A FAIRLY THICK OVERCAST MOST OF THE DAY...LIMITING INSOLATION. IN ANY EVENT...SPC DOES PLACE THE MAJORITY OF CWA IN SLIGHT RISK FOR DAY1...AND THIS LOOKS REASONABLE. TEMPERATURES TODAY WILL ALSO BE TRICKY...PREDICATED AGAIN ON AMOUNT OF SUNSHINE WE RECEIVE. IF SOME BREAKS IN THE CLOUDS OCCUR...SHOULD APPROACH 70...IF WE STAY SOCKED IN CLOUDS/SHOWERS MOST OF THE DAY...TEMPS WILL STRUGGLE TO REACH THE MID 60S. OVERALL WENT SLIGHTLY COOLER THAN GUIDANCE NUMBERS. TONIGHT INTO WEDNESDAY...SRN WI TO REMAIN ON THE NRN PERIPHERY OF THE UPPER LOW THROUGH TUESDAY EVENING SO WILL KEEP A CHANCE OF SHWRS (AND DIURNAL TSTMS) IN THE FORECAST. LOW GRADUALLY OPENS UP AND EJECTS EWD ON WEDNESDAY...WITH WEAK HIGH PRESSURE BRINGING DRIER AND WARMER CONDITIONS INTO THE AREA THROUGH THE MIDDLE OF NEXT WEEK...SHOULD BE A PLEASANT STRETCH OF WEATHER. IN THE EXTENDED...MANY DETAILS STILL TO BE WORKED OUT...BUT GFS/ECMWF/CANADIAN CONTINUE TO INDICATE ENOUGH FORCING ALONG COLD FRONT DROPPING THRU STATE THURSDAY NIGHT THROUGH FRIDAY NIGHT TO WARRANT KEEPING A CHANCE OF SHOWERS AND THUNDERSTORMS IN THE FORECAST THROUGH THE END OF THE WEEK. && .MKX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ FOWLE wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1108 AM EDT MON SEP 4 2006 .DISCUSSION... THE MAIN CONCERN WITH THIS FORECAST UPDATE IS THE POTENTIAL FOR RAIN AND THE TEMPERATURES. WATER VAPOR IMAGERY AND RUC SHOWING A LOW OVER EAST CENTRAL IOWA...WITH A DEFORMATION ZONE OVER CENTRAL LAKE MICHIGAN. A LONGWAVE TROUGH IS QUEBEC AND WELL DEFINED RIDGE BLANKETS THE ROCKIES. ANOTHER RIDGE EXTENDS FROM SOUTHERN SASKATCHEWAN ACROSS SOUTH CENTRAL CANADA INTO CENTRAL QUEBEC. A WEAK SHORTWAVE ASSOCIATED WITH THE DEFORMATION ZONE IS OVER NORTHERN LAKE MICHIGAN. SURFACE ANALYSIS PORTRAYS A LARGE RIDGE OVER THE NORTHERN PLAINS AND SOUTH CENTRAL CANADA. A WEAK DRY COLD FRONT IS DEPICTED FROM NORTHERN SASKATCHEWAN TO SOUTHERN JAMES BAY. MEAN 500-300MB RELATIVE HUMIDITY COINCIDES WELL WITH THE MID AND HIGH CLOUDS INDICATED BY SATELLITE OVER THE FORECAST AREA THIS MORNING. DRY AIR DOMINATES THE AIR MASS BELOW 500MB. THE IOWA LOW WILL SLIDE OVER THE TRI-CITY AREA THIS AFTERNOON AS THE DEFORMATION ZONE MOVES INTO CENTRAL LOWER MICHIGAN. THE RIDGE OVER SOUTH CENTRAL CANADA WILL SETTLE JUST A LITTLE SOUTH AS WELL AND BE JUST NORTH OF LAKE SUPERIOR. THE NORTHERN PLAINS RIDGE WILL EXPAND INTO THE UPPER MISSISSIPPI RIVER VALLEY AND THE UPPER GREAT LAKES REGION. DRY AIR ACCOMPANYING THIS RIDGE SHOULD KEEP ANY POTENTIAL FOR PRECIPITATION FROM OCCURRING. THE MEAN 500-300MB RH INDICATES THAT HIGH CLOUDS WILL REMAIN OVER JUST THE SOUTHERN COUNTIES THIS AFTERNOON...WHILE THE REST OF THE AREA SHOULD SEE MORE SUN. TEMPERATURES ARE RUNNING AROUND GUIDANCE. HOWEVER...WITH THE EXPECTED CLEARING THIS AFTERNOON...THE TEMPERATURES SHOULD BECOME A LITTLE HIGHER THAN GUIDANCE. PLAN TO LEAVE THEM ALONE FOR NOW. TRAJECTORY FORECAST ALSO SUPPORTS WARMER AIR ADVECTING INTO THE AREA. THE MID LEVEL LOW SHOULD RELOCATE OVER PEORIA, IL TONIGHT. THE ASSOCIATED DEFORMATION ZONE WILL REMAIN OVER LOWER MICHIGAN. DRY AIR WILL ADVECT INTO THE AREA. THE SURFACE RIDGE WILL REMAIN OVER THE NORTHERN PLAINS AND STRETCHED ACROSS CENTRAL ONTARIO. WINDS WILL REMAIN LIGHT. THUS CONDITIONS SHOULD REMAIN DRY TONIGHT WITH PLENTY OF RADIATIONAL COOLING WITH A LACK OF LOW LEVEL MIXING. ADVECTION WILL COME FROM OVER LAKE SUPERIOR SO TEMPERATURES WILL BE A LITTLE COOLER THAN GUIDANCE. PLAN TO LEAVE THE FORECAST ALONE FOR NOW. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEWPORT/MOREHEAD CITY NC 1127 AM EDT MON SEP 4 2006 .SHORT TERM / REST OF TODAY/...LOWERED AFTERNOON POPS TO SLIGHT CHANCE OVER INLAND ZONES AS NOT MUCH SUPPORT FOR CONVECTION OVER THIS AREA. WEAK LOW PRES/TROUGH OFFSHORE WILL KEEP SFC WINDS OUT OF THE NORTHEAST OVER MUCH OF THE AREA TODAY BUT WILL SEE WINDS VEER TO A MORE EASTERLY/SOUTHEAST DIRECTION BY LATE AFTERNOON OVER SOUTHERN SECTIONS. WILL KEEP CHANCE POPS ALONG IMMEDIATE COAST AND SOUTHERNMOST COUNTIES WHERE BETTER CONVERGENCE WILL EXIST. REST OF FORECAST IN GOOD SHAPE WITH PARTLY CLOUDY SKIES AND AFTERNOON TEMPS IN THE MID/UPPER 80S. && .AVIATION...FOG AND LOW CLOUDS DIMINISHING WITH PREVAILING VFR CONDITIONS EXPECTED THE REMAINDER OF THE DAY. THERE IS ENOUGH LOW LEVEL MOISTURE AND INSTAB FOR A FEW DIURNAL SHOWERS OR TSTMS THIS AFTERNOON BUT COVERAGE IS EXPECTED TO BE MINIMAL. && .MARINE...MAIN CHANGE WAS TO BUMP UP WINDS TODAY/TONIGHT TO 10-15KT DUE TO WEAK OFFSHORE SFC WAVE. THIS IS IN LINE WITH THE NAM/RUC MODELS. THE GFS FCSTS WINDS CLOSER TO 10 KT. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...NONE. MARINE...NONE. && $$ SHORT TERM...WINGENROTH AVIATION...ELARDO MARINE...ELARDO nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1116 AM EDT MON SEP 4 2006 .SYNOPSIS... SURFACE ANALYSIS THIS MORNING SHOWS HIGH PRESSURE OVER PA AND THE OHIO VALLEY AND AN INVERTED TROF OVER THE SOUTHEAST GULF COAST STATES. A WARM FRONT STRETCHED FROM LA NORTHEAST THROUGH MS...AL...TN...NC AND VA. TEMPS/DEWPOINTS IN NC SOUTH OF THE WARM FRONT WERE IN THE LOWER 70S THIS MORNING AND TEMPS/DEWPOINTS NORTH OF THE WARM FRONT IN VA/WV WERE 10-15F COOLER. RUC HEIGHT ANALYSIS SHOWS A CLOSED H5 LOW OVER IA THIS MORNING...PROGGED TO MOVE SOUTHEAST TOWARDS THE MID-ATLANTIC STATES TONIGHT AND TOMORROW. && .SHORT TERM /REST OF TODAY/... CONVECTIVE SHOWERS HAVE DEVELOPED IN THE NW PIEDMONT THIS MORNING IN VICINITY OF WARM FRONT LOCATED NEAR/ALONG THE NC/VA BORDER. ISENTROPIC ANALYSIS SHOWS WEAK UPGLIDE THAT CORRESPONDS WELL WITH THE PRECIP IN THIS AREA. MODEL THETA-E FIELDS SHOW THE SFC THETA-E GRADIENT TIGHTENING BETWEEN NOW AND LATER THIS AFTERNOON OVER SOUTHERN VA AND NORTHWEST NC WITH HIGH PRESSURE TO THE NORTH IN OH/PA/WV AND A SFC TROF OVER THE SOUTHEAST STATES. WILL UP POPS TO LIKELY IN THE NW PIEDMONT WHERE SUFFICIENT LIFT SHOULD BE PRESENT TO FORCE SHOWERS AND THUNDERSTORMS THIS AFTERNOON. ALTHOUGH THE BEST LIFT WILL BE ASSOCIATED WITH THE WARM FRONT ALONG AND NORTH OF THE NC/VA BORDER AND IN THE NW PIEDMONT...SUNSHINE OVER THE COASTAL PLAIN THIS MORNING SHOULD ALLOW FOR SUFFICIENT DESTABILIZATION FOR SCATTERED CONVECTIVE CELLS TO DEVELOP ALONG DIFFERENTIAL HEATING BOUNDARIES. GIVEN CURRENT SATELLITE AND TEMP TRENDS...WILL LOWER HIGH TEMPS IN NORTHERN AND NORTHWEST PORTIONS OF THE CWA WHERE OVERRUNNING CLOUD COVER IN VICINITY OF THE FRONT WILL SHUNT HEATING FOR THE REMAINDER OF THE MORNING AND PORTIONS OF THE AFTERNOON. -VINCENT && .PREV DISCUSSION... (ISSUED 224 AM EDT MON SEP 4 2006) SHORT TERM /TODAY THROUGH WEDNESDAY NIGHT/... SEE NO REASON TO GIVE THE NAM MODEL THE SLIGHTEST BIT OF CREDIBILITY. IT HAS PERFORMED POORLY AND IS AN OUTLIER MODEL. MAIN TRIGGER FOR RAIN CHANCES TODAY APPEARS TO BE ISENTROPIC LIFT AS SOUTHERLY FLOW BEGINS TO INCREASE THIS AFTERNOON AT 850 MILLIBARS. MODELS IN ROUGH AGREEMENT IN SHOWING THE MOST SIGNIFICANT LIFT IN THE WEST AND WILL TRIM THE EAST TO 30 PERCENT FOR TODAY. MOISTURE IN THE AIR COLUMN ON THE INCREASE TONIGHT WITH SOME LOW LEVEL CONVERGENCE...CURRENT 50 POPS GOOD. SURFACE TROUGH PUSHES THROUGH CENTRAL NORTH CAROLINA TUESDAY WITH 850 MILLIBAR TROUGH LAGGING BEHIND SOMEWHAT. IF DYNAMICS WERE A LITTLE MORE CLEAR CUT WOULD CALL FOR CATEGORICAL RAINFALL BUT WILL STICK WITH LIKELY FOR NOW. THE NAM MODEL IS AN OUTLIER AND RECENT POOR PERFORMER. THE NAM IS LIKELY TOO STRONG AND TOO FAR SOUTH WITH ITS TROUGH IN THE LOWER OHIO VALLEY TUESDAY EVENING...AND HAS TOO STRONG A SURFACE LOW PLACED TOO FAR WEST IN RESPONSE. STICKING CLOSER TO THE GFS AND ITS SUPPORTING MODELS WITH WEDNESDAY DRY OTHER THAN POSSIBLE LINGERING SHOWERS EAST OF INTERSTATE 95 IN THE MORNING. ONLY CONCERN WITH TEMPERATURES IS THE RISK THAT THE TUESDAY AFTERNOON FORECAST IS TOO HIGH. TEMPERATURES OF COURSE WILL BE HIGHLY DEPENDENT ON THE DURATION TIMING AND INTENSITY OF THE RAIN TUESDAY. PREFER THE CURRENT NUMBERS FOR NOW WITH AND EYE TOWARD POSSIBLY LOWERING THEM IN A FUTURE FORECAST. SEVERE THUNDERSTORM THREAT SHOULD BE LIMITED TO TUESDAY AND MARGINAL AT BEST. POTENTIAL ENERGY VERTICALLY THROUGH THE AIR COLUMN IS EVENLY DISTRIBUTED AND LOW. ONE HAS TO CLIMB TO THE CIRRUS LEVEL TO FIND WINDS GREATER THAN 50 KNOTS. MAIN THREAT WOULD BE GUSTY DOWNBURST WINDS. AN ISOLATED THREAT AT BEST. LONG TERM /THURSDAY THROUGH SUNDAY/... SURFACE HIGH PRESSURE SETTLES OVER THE SOUTHEAST UNITED STATES EARLY IN THE PERIOD AND SLIPS EAST OFF SHORE AS THE WEEKEND APPROACHES. ANY RAIN CHANCE SHOULD BE SLIGHT AND MOSTLY CONFINED TO THE AFTERNOONS AND EVENINGS OF FRIDAY AND THE WEEKEND. TEMPERATURES NOT FAR FROM CLIMATOLOGY. AVIATION... INVERTED TROUGH BUILDING ALONG THE COAST WILL RESULT IN EAST TO SOUTHEAST FLOW. THE COMBINATION OF INCREASED MOISTURE AND LITTLE OR NO WIND WILL LEAD TO THE DEVELOPMENT OF STRATUS AND FOG. THROUGH 13Z...IFR TO LIFR CEILINGS. MVFR TO IFR VISIBILITY GSO TO INT...AND IFR TO LIFR RDU TO FAY ON EAST. AFTER 13Z CLOUD BASES 25 HUNDRED TO 4 THOUSAND FEET. VISIBILITY UNRESTRICTED EXCEPT LOWERING TO MVFR/IFR IN SCATTERED RAIN AND FOG AFTER 18Z. LIGHT EAST TO CALM WINDS THIS MORNING BECOMING SOUTHEAST 5 TO 10 MPH AFTER 17Z. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT SHORT TERM...VINCENT nc AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAND FORKS ND 948 AM CDT MON SEP 4 2006 .UPDATE...VERY FEW CHALLENGES FOR TODAY WITH HIGH PRESSURE DIRECTLY OVERHEAD. TEMPERATURES LOOK TO BE ON TRACK WITH CURRENT FORECAST. 12Z RUC/NAM SHOWING NEGATIVE CU RULE VALUES ACROSS THE SOUTHERN FA TODAY AND WILL INCREASE SKY COVER A BIT (UP TO 50%) TO ACCOUNT FOR AFTERNOON CU DEVELOPMENT. REMAINDER OF FA WILL SEE NO CLOUDS AND RESULTANT WARMER TEMPERATURES. MORNING PATCHY FOG HAS DISSIPATED. && .PREV DISCUSSION... (ISSUED 355 AM CDT MON SEP 4 2006) DISCUSSION...MAIN FORECAST CHALLENGES ARE TEMPERATURES AND PRECIPITATION. WHEN LOOKING AT THE LATEST SURFACE ANALYSIS...HIGH PRESSURE IS CENTERED BETWEEN MOT AND DVL WITH THE RIDGE AXIS EXTENDING THROUGH CENTRAL ND INTO CENTRAL SD. WHEN COMPARING MODELS...THE NAM AND GFS ARE PRETTY SIMILAR...SO USED COMPROMISE FOR FORECAST. HIGH PRESSURE IS EXPECTED TO DOMINATE THE REGION'S WEATHER THROUGH THE MIDDLE PART OF THE WEEK...PROVIDING DRY WEATHER WITH PLENTY OF SUNSHINE AND TEMPERATURES ABOVE NORMAL. WHEN LOOKING INTO THE EXTENDED FORECAST...KEPT MODEL CONTINUITY WITH THE NEXT LOW PRESSURE SYSTEM MOVING INTO THE N PLAINS BY THU...AND BRINGING THE NEXT CHANCE FOR SHOWERS AND THUNDERSTORMS ON THU NIGHT INTO FRI. THE PASSAGE OF THIS FRONT SHOULD BRING COOLER AIR INTO THE REGION AND DROP TEMPERATURES TO NEAR TO SLIGHTLY BELOW NORMAL FOR THE WEEKEND. OVERALL...ONLY MINOR CHANGES NEEDED TO ENTIRE FORECAST. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ TG/NG nd AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BLACKSBURG VA 1028 AM EDT MON SEP 4 2006 .SHORT TERM /REST OF TODAY/... SHRA CONTINUING TO MOVE SLOWLY NORTHEAST ACROSS MUCH OF THE REGION THIS MORNING IN AREA OF ISENTROPIC LIFT NORTH OF FRONT OVER THE CAROLINAS. WEAK SURFACE WAVE IN AXIS OF HIGHER THETA-E ALSO SUPPORTING LIFT AHEAD OF INIT 85H WAVE TO THE WEST AND 3H JET MAX ALONG VAPOR PLUME SEEN IN THE OHIO VALLEY PER 12Z U/A. EXPECT THIS ALONG WITH CURRENT UVV/MOIST PWATS TO KEEP FIRST ROUND OF SHRA GOING UNTIL EARLY AFTERNOON PER RUC ANALYSIS BEFORE BETTER HEATING TO THE SOUTH/SW CAUSES ADDED COVERAGE TO ADVECT BACK NE LATER ON. GIVEN COOL WEDGE IN PLACE...EHANCHED VIA RAINFALL...TRICKY AS TO AMOUNT OF INSTABILITY THIS AFTERNOON WITH THE FAR SOUTH/SW HAVING THE BEST SHOT AT INSOLATION AS SEEN IN LATEST NAM LI'S. THUS PLAN TO LIMIT ANY ORGANIZED TSRA TO THE SW/SOUTHERN ZONES LATER THIS AFTERNOON WITH OVERALL HIGH CHANCE TO LIKELY POPS ELSEWHERE ESPCLY EARLY ON. CLOUDS AND COOL POOL SUPPORT LOWERING HIGHS A CAT OR SO IN SPOTS BUT STILL A BIT ABOVE CHILLY LAMP VALUES UNLESS CLOUDS HOLD IN COOL POOL IN WAKE OF SHRA. OTRW ONLY MINOR CHANGES TO EARLIER UPDATE THIS MORNING FOR NOW. && .PREV DISCUSSION... (ISSUED 828 AM EDT MON SEP 4 2006) SHORT TERM /REST OF TODAY/... BASED ON CURRENT RADAR COVERAGE AND INTENSITY WILL SEND OUT AN EARLY UPDATE TO BOOST POPS SOUTHERN HALF TO LIKELYS FOR THE REST OF THE MORNING AND INCREASE TO HIGH CHANCE NORTH. QPF ALSO UNDERDONE OFF RADAR ESTIMATES SO WILL INCREASE AMOUNTS AS WELL AS HAVE SEEN A QUICK HALF TO ONE INCH IN SOME OF THE DOWNPOURS. REMAINDER UNCHANGED FOR NOW PENDING LATE MORNING UPDATE. PREV DISCUSSION... (ISSUED 635 AM EDT MON SEP 4 2006) AVIATION... AS PRECIPITATION BECOMES MORE WIDESPREAD BY THE EVENING... ESPECIALLY WEST OF THE BLUE RIDGE...CEILINGS WILL LOWER...WITH IFR TO LIFR CONDIITONS EXPECTED AFTER 00Z. CEILINGS AND VISIBILTIES WILL BE IFR TO MVFR IN THE EAST OVERNIGHT. PREV DISCUSSION... (ISSUED 321 AM EDT MON SEP 4 2006) SHORT TERM /TODAY/... MAIN ISSUE TODAY IS DEGREE OF CLD COVER/PRECIP POTENTIAL ALONG WITH SUBSEQUENT EFFECT ON TEMPS. EARLY MORNING ANALYSIS SHOWS POTENT UPR LOW DIGGING INTO IOWA WITH IMPRESSIVE STREAM OF SUBTROPICAL MOISTURE FROM REMNANTS OF TD JOHN BEING ADVECTED EASTWARD BY NEARLY 100 KT JET THRU THE MIDWEST. AT THE SFC...WEAK RIDGING SLIDING DOWN EAST OF THE MOUNTAINS FROM OHIO VALLEY...HELPING ADVECT SLIGHTLY LOWER THETA-E AIR SOUTHWARD INTO FAR NRN AREAS. TO THE SOUTH...BEGINNINGS OF WARM FRONTOGENESIS SHOWING UP ACRS GEORGIA...WITH EFFECTS OF WEAK ISENTROPIC LIFT ALREADY IN PLACE IN THE FORM OF SLOWLY INCREASING COVERAGE OF EARLY MORNING SHRA AND LOW/MID CLD DECK. BELIEVE THIS TREND WILL CONTINUE THRU THE DAY AS WEAK ISENTROPIC LIFT REMAINS IN PLACE AHEAD OF SLOWLY LIFTING WARM FRONT. THIS SHOULD ALLOW CLD DECK TO CONTINUE EXPANDING EARLY THIS MORNING. MAY CATCH A BRIEF BREAK BY LATE MORNING WITH COVERAGE OF SHRA BEFORE LIFT AGAIN ENHANCES BY EARLY AFTN AHEAD OF LEAD SHORTWAVE LIFTING OUT OF THE SRN PLAINS. WILL CONTINUE TO CARRY LIKELY POPS ACRS THE SOUTHWEST TODAY CLOSER TO LIFTING BOUNDARY...TAPERING TO CHANCE FAR NORTHEAST WHERE RESIDUAL AXIS OF LOWER THETA-E AIR MAY ACT TO HOLD PRECIP AT BAY FOR A WHILE. BELIEVE FORM OF PRECIP WILL MAINLY BE SHOWERS...ALTHOUGH HAVE CONTINUED TSRA MENTION ACRS THE SOUTHWEST WHERE STRONGER THETA-E ADVECTION RESIDES IN AREA OF PROGGED LOWER LI/MARGINAL CAPE FIELD. SHOULD ANY BREAKS IN CLD COVER OCCUR...COULD EVEN SEE A STRONGER STORM PER INCREASING VERTICAL SHEAR IN A MOIST ENVIRONMENT. TEMPS TRICKY GIVEN POTENTIAL FOR SOME BREAKS IN CLD COVER BY EARLY AFTN...BUT WILL HOLD HIGHS CLOSER TO WARMER MAV MOS GIVEN WARMER START THIS MORNING OWING TO INCREASING CLD COVER. LONG TERM /TONIGHT THROUGH SUNDAY/... STARTING TO SEE THE SAME SCENERIO WITH THE EVOLUTION OF THE UPPER LOW IN IOWA ON BOTH THE GFS AND NAM...HOWEVER THE DIFFERENCES IN TIMING ARE SIGNIFICANT. BOTH MODELS BRING A SERIES OF JET STREAKS DOWN THE WEST SIDE AND EVENTUALLY AROUND THE BASE OF THE UPPER LOW AS IT TRACK TOWARD SOUTHERN INDIANA. THEN THE LOW STARTS TO BECOME AN OPEN WAVE...TRACKING ACROSS THE OHIO VALLEY. THE BIGGEST QUESTION IS WHEN. 850 AND 700 MB WARM AIR ADVECTION AS WELL AS ISENTROPIC LIFT INCREASE TODAY AND SPREAD PRECIPITATION AND DEEPER MOISTURE ACROSS THE FORECAST AREA TODAY THEN SHIFT THE FOCUS OF LIFT TO THE WESTERN COUNTY WARNING AREA TONIGHT AND TUESDAY. A SURFACE LOW WILL DEVELOP IN THE TENNESSEE VALLEY BUT THE TIMING IS SLOWER ON THE NAM THAN THE GFS. DON'T WANT TO ENTIRELY DISCOUNT THE NAM. EVEN THE GFS HAS A WAVE ALONG THE FRONT WHICH SLOWS DOWN THE EASTWARD PROGRESS OF THE FRONT UNTIL THIS WAVE TRACKS EAST OF THE APPALACHIANS...WITH THE CDFNT TO THE EAST OF THE COUNTY WARNING AREA AT 00Z WEDNESDAY. SO WILL RAISE PERCENTAGE TO NEAR 100 IN THE WEST TONIGHT THEN WILL START LOWERING CHANCE OF RAIN FROM WEST TO EAST ON TUESDAY NIGHT AND BY WEDNESDAY WILL HAVE LITTLE TO NO CHANCE IN THE EAST. GUIDANCE HAS ONLY A SMALL DROP IN TEMPERATURES TONIGHT AND NEARLY STEADY OR JUST A SMALL RISE IN TEMPERATURES ON TUESDAY. HAVE LOWERED MAXIMUM TEMPERATURES FOR TUESDAY A CATAGORY OR TWO ALONG AND WEST OF THE BLUE RIDGE. NO CHANGES HAVE BEEN MADE TO THE FORECAST AFTER WEDNESDAY. AVIATION... WARM ADVECTION/ISENTROPIC LIFT HELPING DRIVE THE DEVELOPMENT OF ISOLD/SCATTERED SHOWERS EARLY THIS MORNING...AND BELIEVE THIS TREND WILL CONTINUE THROUGH 15Z OR SO. HAVE ONLY CARRIED MENTION OF VCSH AROUND KDAN CLOSEST TO STRONGER LIFT...ALTHOUGH COULD SEE A FEW SHRA CLOSE TO OTHER VIRGINIA TAF SITES. LOW/MID CLOUD DECK ALSO ON THE INCREASE THROUGHOUT THE NIGHT...WITH MVFR CONDITIONS OVERSPREADING THE AREA. SOME POSSIBILITY FOR EVEN LOWER CEILINGS ACRS NORTHEASTERN AREAS WHERE LOW CLD DECK CONTINUES TO ADVECT SOUTH FROM NORTHERN VIRGINIA. A FEW AREAS OF FOG ALSO POSSIBLE...MAINLY RIVER VALLEYS ESPECIALLY AROUND KLWB WHERE DENSE FOG POSSIBLE FOR A TIME BEFORE THICKER CLD COVER ARRIVES. MORE SHOWERS WILL DEVELOP DURING THE AFTN...WITH COVERAGE EXPECTED TO BE WIDESPREAD BY THE END OF THE TAF PERIOD. ASIDE FROM A PERIOD OF VFR CONDITIONS EARLY THIS AFTN...THINK MOST SPOTS WILL GO BACK TO MVFR LEVELS LATE IN THE DAY AS MOISTURE CONTINUES TO INCREASE. EVEN LOWER CONDITIONS IN THE IFR RANGE POSSIBLE BY THE END OF THE TAF PERIOD AS RAIN CONTINUES. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ JH va AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 335 PM EDT MON SEP 4 2006 .SYNOPSIS... 12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW POSITIVELY TILTED UPR TROFFING STRETCHING FM CUTOFF LO OVER IA INTO QUEBEC DOWNSTREAM OF FAIRLY HI AMPLITUDE RDG FM WRN NAMERICA ELONGATED INTO NW ONTARIO. SCT-BKN HI CLDS ON THE NW FLANK OF TROF TO THE SE NOTED OVER THE UPR GRT LKS THIS AFTN. 15Z TAMDAR SDNG FM SAW WAS DRY EXCEPT FOR A MOIST LYR H8-85...AND SOME ELEVATED SC HAS DVLPD WITH SFC HTG TDAY INLAND FM LK BREEZE PENETRATION. 12Z GRB SDNG LOOKS SIMILAR TO THE SAW SDNG...BUT IS A BIT MORE MOIST CLOSER TO THE TROF AXIS. SFC-H85 HI UNDER UPR RDG IS CENTERED OVER ND...AND AIRMASS TO THE NW IS QUITE DRY PER 12Z INL/YPL SDNGS. NOTHING BUT A FEW DIURNAL CU NOTED IN THIS AREA. DEEP MIXING TO SUBSIDENCE INVRN AT H775-8 ON THESE SDNGS WOULD SUPPORT HI TEMPS ARND 80...WITH DWPTS MIXING OUT INTO THE LO-MID 40S. OTRW...SOME FOG PATCHES NOTED OVER WRN LK SUP IN THE NRSHORE AREA FM ONTONAGON-P59 AND OVER THE OPEN WATERS OF ERN LK SUP. ANOTHER SHRTWV NOTED DIGGING SEWD THRU NRN CAN IN THE NW FLOW ALF ON THE WRN FLANK OF CUTOFF LO OVER BAFFIN ISLAND. MAIN FCST CONCERNS THE NEXT FEW DAYS ARE TEMPS AND TIMING OF ANY IMPACT FM SHRTWV NOW MOVING THRU NRN CAN. FOR TNGT...UPR LO OVER IA/TROF AXIS EXTENDING TO THE NE FCST TO DRIFT SLOWLY SEWD TOWARD THE OHIO RIVER VALLEY. EXPECT BULK OF HI CLD TO DRIFT SE AS WELL AS UPR RDG AXIS/DRIER AIR TO THE NW SLOWLY MOVE TOWARD THE CWA. WITH LGT WINDS UNDER RISING MSLP TNGT/FAIRLY HI SFC DWPTS OVER THE FA TDAY (THAT WL BE ADVECTED ONLY SLOWLY SWD TNGT)...GOING FCST OF FOG LOOKS TO BE ON TRACK FOR TNGT. WL RAISE FCST LO TEMPS A BIT OVER THE SRN TIER TO REFLECT HIER PWAT LINGERING CLOSER TO THE DEPARTING TROF AXIS...OTRW WL TEND AOB LO END OF MOS GUIDANCE FOR THE INTERIOR W/NCNTRL AS DRY AIR IN LLVLS SHOWN ON UPSTREAM SDNGS OOZES SLOWLY OVHD. TUE LOOKS TO BE A VERY NICE LATE SUMMER DAY WITH RDG AXIS DOMINATING. WITH MOSUNNY SKIES...DEEP MIXING TO H775-8 ON GFS FCST SDNGS YIELDS HI TEMPS AWAY FM LK SUP MODERATION IN LGT NLY FLOW ARND 80...CONSISTENT WITH 12Z YPL/INL SDNGS. WL LOWER GOING FCST DWPTS A COUPLE OF DEGREES TO REFLECT VERY DRY IN THE LLVLS OBSVD UPSTREAM THIS MRNG. SHRTWV NOW OVER NRN CAN FCST TO REACH NR JAMES BY AT 00Z WED AND THEN SWING THRU QUEBEC BY LATE WED. GFS/NAM/UKMET SHOW THIS BNDRY MOVING INTO THE CWA TUE NGT BEFORE STALLING ON WED NR THE WI BORDER ZNS. ANTECEDENT AIRMASS IS QUITE DRY AND ANY SGNFT DPVA/QVECTOR CNVGC PROGGED TO REMAIN WELL NE OF THE CWA...BUT MODELS GENERATE SOME LGT PCPN OVER THE AREA LATE TUE NGT/WED. THINK THE BEST CHC FOR PCPN WOULD BE DURING DIURNAL HTG ON WED AFTN ALG STALLED BNDRY INLAND WHERE LK BREEZES IN WEAK PRES GRADIENT MAY ENHANCE LLVL CNVGC. THIS SCENARIO WOULD BE MORE LIKELY IN JULY AND IN PRESENCE OF DEEPER MSTR (FCST PWAT <1 INCH). BUT GFS FCST SDNGS FOR IRON RIVER-IMT AREA SHOW SBCAPE CLOSE TO 1000J/KG FOR T/TD 77/50...SO WL FCST SHRA/TSRA DURING THE AFTN OVER THE INTERIOR BUT KEEP PROBABILITY RESTRICTED TO SCHC TO REFLECT RELATIVELY LO PWAT/KINX (ARND 30). IT APPEARS BNDRY WL ARRIVE LATE ENUF TUE NGT TO ALLOW TEMPS TO SINK FAIRLY SHARPLY NR THE WI BORDER TUE NGT...SO LEFT GOING FCST AS IS. LACK OF DEEPER MSTR/CLD COVER WL ALLOW TEMPS TO RECOVER WELL INTO THE 70S AND HI ENUF TO WARRANT SMALL POPS AWAY FM THE MODERATING INFLUENCE OF THE GRT LKS. IF ANY DIURNALLY INDUCED SHRA/TSRA DVLP ALG STALLED BNDRY...THEY WL DIMINISH WITH LOSS OF SFC HTG WED EVNG...ESPECIALLY AS BNDRY UNDERGOES FRONTOLYSIS WITH DVLPMNT OF WAD PATTERN. STEADY WSW WIND AND CLDS ASSOCIATED WITH WAD WL ACT TO MAINTAIN HIER LO TEMPS. FAIRLY GOOD AGREEMENT AMONG THE 00Z OPERATIONAL MODELS ON THE HANDLING OF DVLPG UPR TROFFING OVER THE GRT LKS AT THE END OF THE WEEK/NEXT WEEKEND. 06Z/12Z GFS SHOW A SIMILAR SCENARIO...BUT IS A BIT SLOWER TO PUSH ACCOMPANYING COLD FNT/DRIER AIR ASSOCIATED WITH ONTARIO HI PRES TO THE S IN RESPONSE TO SECOND SHRTWV DIVING S THRU CNTRL CAN INTO THE DEEPENING TROF. LATEST NCEP GUIDANCE SHOWS PREFERENCE FOR 00Z RUNS AND SPECIFICALLY THE MORE CONSISTENT ECMWF...SO WL FOLLOW ITS GUIDANCE MORE CLOSELY WITH ADJUSTMENTS NOTED BLO. HAVE RETAINED MENTION OF TSRA WITH UPR TROFFING DVLPG ABV H85 THERMAL RDG (00Z FRI H85 TEMP 14C) NEAR/ IMMEDIATELY IN WAKE OF FROPA LATE THU INTO FRI. PRE-FRONTAL CNVCTN WOULD BE LIMITED BY LACK OF SGNFT MSTR INFLOW AND RATHER HI ECWMF FCST H85 T-TD OF 8C AT 00Z FRI. RETAINED SHRA CHC A LTL LONGER INTO FRI NGT VS ECMWF FCST BEHIND FROPA TO REFLECT GFS REFCST ENSEMBLE SUPPORT FOR THE SOMEWHAT SLOWER SOLN OF THE 06Z/12Z OPERATIONAL GFS. ALSO BUMPED UP POPS OVER THE SCNTRL FRI TO ACCOUNT FOR UPR DVGC IN RRQ OF H3 JET MAX FCST BY 12Z GFS TO PASS THRU ONTARIO. BACKED OFF ON THE LK EFFECT RA FCST AS ECMWF SHOWING HIER H85 TEMPS NO LOWER THAN 4-6C/MORE ACYC FLOW BEHIND THE FNT. THEN DRYING TREND SAT INTO SUN BEFORE ECMWF SHOWS INCRSG MSTR LATE SUN INTO MON IN ADVANCE OF DVLPG TROFFING IN THE PLAINS. CARRIED CHC -SHRA FOR NEXT MON. AS FOR TEMPS...THU WL BE A WARM DAY WITH WSW FLOW IN ADVANCE OF FNT AND TEMPS TOWARD THE HI END OF GFS MOS GUIDANCE...THEN TURNING MUCH COOLER ON FRI AND INTO THE WEEKEND (BUT NOT AS COOL AS 00Z GFS MOS FCST AS 00Z GFS FCST H85 TEMPS TOO LO). COORDINATED WITH APX/GRB/DLH. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ KC mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BLACKSBURG VA 206 PM EDT MON SEP 4 2006 .AVIATION... EXPECT OVERALL MVFR TO IFR CONDITIONS TO PREVAIL OVER THE NEXT 24 HOURS AS FRONT AND NEXT WAVE OF LOW PRES COMBO TO PRODUCE LOW CLOUDS/SHRA OVER THE REGION. APPEARS HEAVIEST RAINFALL AND LOWEST CEILINGS WILL OCCUR OVER THE SE WVA SITES ESPCLY AFTER MIDNIGHT WHEN PERIODIC LIFR POSSIBLE. SOME BREAKS POSSIBLE TUE MORNING BUT NOT CONFIDENT ENOUGH AT THIS POINT TO RAISE CEILINGS OR VSBYS TO VFR LEVELS. && .PREV DISCUSSION... (ISSUED 1028 AM EDT MON SEP 4 2006) SHORT TERM /REST OF TODAY/... SHRA CONTINUING TO MOVE SLOWLY NORTHEAST ACROSS MUCH OF THE REGION THIS MORNING IN AREA OF ISENTROPIC LIFT NORTH OF FRONT OVER THE CAROLINAS. WEAK SURFACE WAVE IN AXIS OF HIGHER THETA-E ALSO SUPPORTING LIFT AHEAD OF INIT 85H WAVE TO THE WEST AND 3H JET MAX ALONG VAPOR PLUME SEEN IN THE OHIO VALLEY PER 12Z U/A. EXPECT THIS ALONG WITH CURRENT UVV/MOIST PWATS TO KEEP FIRST ROUND OF SHRA GOING UNTIL EARLY AFTERNOON PER RUC ANALYSIS BEFORE BETTER HEATING TO THE SOUTH/SW CAUSES ADDED COVERAGE TO ADVECT BACK NE LATER ON. GIVEN COOL WEDGE IN PLACE...EHANCHED VIA RAINFALL...TRICKY AS TO AMOUNT OF INSTABILITY THIS AFTERNOON WITH THE FAR SOUTH/SW HAVING THE BEST SHOT AT INSOLATION AS SEEN IN LATEST NAM LI'S. THUS PLAN TO LIMIT ANY ORGANIZED TSRA TO THE SW/SOUTHERN ZONES LATER THIS AFTERNOON WITH OVERALL HIGH CHANCE TO LIKELY POPS ELSEWHERE ESPCLY EARLY ON. CLOUDS AND COOL POOL SUPPORT LOWERING HIGHS A CAT OR SO IN SPOTS BUT STILL A BIT ABOVE CHILLY LAMP VALUES UNLESS CLOUDS HOLD IN COOL POOL IN WAKE OF SHRA. OTRW ONLY MINOR CHANGES TO EARLIER UPDATE THIS MORNING FOR NOW. PREV DISCUSSION... (ISSUED 828 AM EDT MON SEP 4 2006) SHORT TERM /REST OF TODAY/... BASED ON CURRENT RADAR COVERAGE AND INTENSITY WILL SEND OUT AN EARLY UPDATE TO BOOST POPS SOUTHERN HALF TO LIKELYS FOR THE REST OF THE MORNING AND INCREASE TO HIGH CHANCE NORTH. QPF ALSO UNDERDONE OFF RADAR ESTIMATES SO WILL INCREASE AMOUNTS AS WELL AS HAVE SEEN A QUICK HALF TO ONE INCH IN SOME OF THE DOWNPOURS. REMAINDER UNCHANGED FOR NOW PENDING LATE MORNING UPDATE. PREV DISCUSSION... (ISSUED 635 AM EDT MON SEP 4 2006) AVIATION... AS PRECIPITATION BECOMES MORE WIDESPREAD BY THE EVENING... ESPECIALLY WEST OF THE BLUE RIDGE...CEILINGS WILL LOWER...WITH IFR TO LIFR CONDIITONS EXPECTED AFTER 00Z. CEILINGS AND VISIBILTIES WILL BE IFR TO MVFR IN THE EAST OVERNIGHT. PREV DISCUSSION... (ISSUED 321 AM EDT MON SEP 4 2006) SHORT TERM /TODAY/... MAIN ISSUE TODAY IS DEGREE OF CLD COVER/PRECIP POTENTIAL ALONG WITH SUBSEQUENT EFFECT ON TEMPS. EARLY MORNING ANALYSIS SHOWS POTENT UPR LOW DIGGING INTO IOWA WITH IMPRESSIVE STREAM OF SUBTROPICAL MOISTURE FROM REMNANTS OF TD JOHN BEING ADVECTED EASTWARD BY NEARLY 100 KT JET THRU THE MIDWEST. AT THE SFC...WEAK RIDGING SLIDING DOWN EAST OF THE MOUNTAINS FROM OHIO VALLEY...HELPING ADVECT SLIGHTLY LOWER THETA-E AIR SOUTHWARD INTO FAR NRN AREAS. TO THE SOUTH...BEGINNINGS OF WARM FRONTOGENESIS SHOWING UP ACRS GEORGIA...WITH EFFECTS OF WEAK ISENTROPIC LIFT ALREADY IN PLACE IN THE FORM OF SLOWLY INCREASING COVERAGE OF EARLY MORNING SHRA AND LOW/MID CLD DECK. BELIEVE THIS TREND WILL CONTINUE THRU THE DAY AS WEAK ISENTROPIC LIFT REMAINS IN PLACE AHEAD OF SLOWLY LIFTING WARM FRONT. THIS SHOULD ALLOW CLD DECK TO CONTINUE EXPANDING EARLY THIS MORNING. MAY CATCH A BRIEF BREAK BY LATE MORNING WITH COVERAGE OF SHRA BEFORE LIFT AGAIN ENHANCES BY EARLY AFTN AHEAD OF LEAD SHORTWAVE LIFTING OUT OF THE SRN PLAINS. WILL CONTINUE TO CARRY LIKELY POPS ACRS THE SOUTHWEST TODAY CLOSER TO LIFTING BOUNDARY...TAPERING TO CHANCE FAR NORTHEAST WHERE RESIDUAL AXIS OF LOWER THETA-E AIR MAY ACT TO HOLD PRECIP AT BAY FOR A WHILE. BELIEVE FORM OF PRECIP WILL MAINLY BE SHOWERS...ALTHOUGH HAVE CONTINUED TSRA MENTION ACRS THE SOUTHWEST WHERE STRONGER THETA-E ADVECTION RESIDES IN AREA OF PROGGED LOWER LI/MARGINAL CAPE FIELD. SHOULD ANY BREAKS IN CLD COVER OCCUR...COULD EVEN SEE A STRONGER STORM PER INCREASING VERTICAL SHEAR IN A MOIST ENVIRONMENT. TEMPS TRICKY GIVEN POTENTIAL FOR SOME BREAKS IN CLD COVER BY EARLY AFTN...BUT WILL HOLD HIGHS CLOSER TO WARMER MAV MOS GIVEN WARMER START THIS MORNING OWING TO INCREASING CLD COVER. LONG TERM /TONIGHT THROUGH SUNDAY/... STARTING TO SEE THE SAME SCENERIO WITH THE EVOLUTION OF THE UPPER LOW IN IOWA ON BOTH THE GFS AND NAM...HOWEVER THE DIFFERENCES IN TIMING ARE SIGNIFICANT. BOTH MODELS BRING A SERIES OF JET STREAKS DOWN THE WEST SIDE AND EVENTUALLY AROUND THE BASE OF THE UPPER LOW AS IT TRACK TOWARD SOUTHERN INDIANA. THEN THE LOW STARTS TO BECOME AN OPEN WAVE...TRACKING ACROSS THE OHIO VALLEY. THE BIGGEST QUESTION IS WHEN. 850 AND 700 MB WARM AIR ADVECTION AS WELL AS ISENTROPIC LIFT INCREASE TODAY AND SPREAD PRECIPITATION AND DEEPER MOISTURE ACROSS THE FORECAST AREA TODAY THEN SHIFT THE FOCUS OF LIFT TO THE WESTERN COUNTY WARNING AREA TONIGHT AND TUESDAY. A SURFACE LOW WILL DEVELOP IN THE TENNESSEE VALLEY BUT THE TIMING IS SLOWER ON THE NAM THAN THE GFS. DON'T WANT TO ENTIRELY DISCOUNT THE NAM. EVEN THE GFS HAS A WAVE ALONG THE FRONT WHICH SLOWS DOWN THE EASTWARD PROGRESS OF THE FRONT UNTIL THIS WAVE TRACKS EAST OF THE APPALACHIANS...WITH THE CDFNT TO THE EAST OF THE COUNTY WARNING AREA AT 00Z WEDNESDAY. SO WILL RAISE PERCENTAGE TO NEAR 100 IN THE WEST TONIGHT THEN WILL START LOWERING CHANCE OF RAIN FROM WEST TO EAST ON TUESDAY NIGHT AND BY WEDNESDAY WILL HAVE LITTLE TO NO CHANCE IN THE EAST. GUIDANCE HAS ONLY A SMALL DROP IN TEMPERATURES TONIGHT AND NEARLY STEADY OR JUST A SMALL RISE IN TEMPERATURES ON TUESDAY. HAVE LOWERED MAXIMUM TEMPERATURES FOR TUESDAY A CATAGORY OR TWO ALONG AND WEST OF THE BLUE RIDGE. NO CHANGES HAVE BEEN MADE TO THE FORECAST AFTER WEDNESDAY. AVIATION... WARM ADVECTION/ISENTROPIC LIFT HELPING DRIVE THE DEVELOPMENT OF ISOLD/SCATTERED SHOWERS EARLY THIS MORNING...AND BELIEVE THIS TREND WILL CONTINUE THROUGH 15Z OR SO. HAVE ONLY CARRIED MENTION OF VCSH AROUND KDAN CLOSEST TO STRONGER LIFT...ALTHOUGH COULD SEE A FEW SHRA CLOSE TO OTHER VIRGINIA TAF SITES. LOW/MID CLOUD DECK ALSO ON THE INCREASE THROUGHOUT THE NIGHT...WITH MVFR CONDITIONS OVERSPREADING THE AREA. SOME POSSIBILITY FOR EVEN LOWER CEILINGS ACRS NORTHEASTERN AREAS WHERE LOW CLD DECK CONTINUES TO ADVECT SOUTH FROM NORTHERN VIRGINIA. A FEW AREAS OF FOG ALSO POSSIBLE...MAINLY RIVER VALLEYS ESPECIALLY AROUND KLWB WHERE DENSE FOG POSSIBLE FOR A TIME BEFORE THICKER CLD COVER ARRIVES. MORE SHOWERS WILL DEVELOP DURING THE AFTN...WITH COVERAGE EXPECTED TO BE WIDESPREAD BY THE END OF THE TAF PERIOD. ASIDE FROM A PERIOD OF VFR CONDITIONS EARLY THIS AFTN...THINK MOST SPOTS WILL GO BACK TO MVFR LEVELS LATE IN THE DAY AS MOISTURE CONTINUES TO INCREASE. EVEN LOWER CONDITIONS IN THE IFR RANGE POSSIBLE BY THE END OF THE TAF PERIOD AS RAIN CONTINUES. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ JH va AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI 322 PM CDT MON SEP 4 2006 .DISCUSSION...FORECAST FOCUS ON PRECIP COVERAGE TONIGHT AND TUESDAY AS UPR LOW EXITS RGN. WATER VAPOR IMAGERY INDICATING UPR LOW TAKING EXPECTED DIP TO THE SE FROM CURRENT POSITION IN ERN IA. CONVECTION FIRING IN NW IL...IN RGN OF SFC MOISTURE FLUX CONVERGENCE ALONG WEAK INVERTED SFC TROF AND LIFT FROM CVA AHEAD OF SHRT WV LOBE LIFTING NWD THRU NRN THIRD OF IL...SHOULD CONTINUE INTO SRN TWO TIERS OF COUNTIES BEFORE DROPPING SWD LATER TONIGHT WITH BETTER FORCING AS LOW DROPS SE. CONVECTION WILL BE SLOW MOVING AS IT PIVOTS AROUND VORT CENTER PROVIDING OPPORTUNITY FOR HVY RAIN OVER A WEST TO EAST BAND ALONG AND NORTH OF IL BORDER. HAVE SMALL STREAM ADVISORY IN LAFAYETTE CNTY WHERE DOPPLER PCPN ESTIMATES SHOW 1 -2 INCHES HAVE FALLEN IN PORTIONS OF SW LAFAYETTE SINCE 130 PM. WILL HAVE TO MONITOR FOR LOCATIONS TO THE EAST AS SRN TIER REMAINS IN THIS INFLECTION ZONE ON NORTH END OF MAIN VORT CENTER THRU REST OF AFTERNOON INTO THE EVENING. WILL BE A FAIRLY SHARP GRADIENT OF PCPN OVER SRN WI TONIGHT AS CWA REMAINS ON THE NRN PERIPHERY OF THE UPPER LOW...WITH THE BEST CHANCES CLOSE TO THE IL BORDER. NAM/GFS AND RUC ALL CONSISTENT IN LIFTING VORT LOBE TO AXIS OF 500 TROF FROM NE IL ACROSS SRN LK MI BY 06Z...THEN STALLING AS LOW DROPS SE. WILL KEEP OCCASIONAL SHRA ACROSS SRN CWA WITH SCT TO THE NORTH. LAST GASP OF UPR LOW COMES WITH VORT LOBE ROTATING THRU SE PORTION OF STATE TUE AFTERNOON...THEN DRYING FOR OVERNIGHT TUESDAY AND WED. WILL KEEP A CHANCE OF SHWRS AND AFTERNOON TSTMS IN THE FORECAST. LOW GRADUALLY OPENS UP AND EJECTS EWD ON WEDNESDAY...WITH WEAK HIGH PRESSURE BRINGING DRIER AND WARMER CONDITIONS INTO THE AREA THROUGH THE MIDDLE OF NEXT WEEK. IN THE EXTENDED...GFS/ECMWF/CANADIAN HAVE DELAYED PASSAGE OF COLD FRONT THRU STATE WILL PUSH BACK AREAL COVERAGE OF SHRA/TSTMS THRUSDAY NIGHT AND LINGER SHRA IN THE SOUTH FRIDAY NIGHT. && .MKX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ REM wi