Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 101147 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 647 AM EST WED FEB 10 2010 .SYNOPSIS... AS STRONG LOW PRESSURE MOVES FARTHER OFF THE COAST...THE PRESSURE GRADIENT BETWEEN THE LOW AND THE HIGH OVER THE MISSISSIPPI VALLEY WILL CREATE VERY WINDY CONDITIONS TODAY. LOW PRESSURE OVER THE GULF EARLY FRIDAY WILL BE WELL OFF THE CAROLINA COAST EARLY SATURDAY. AN UPPER LEVEL SYSTEM WILL QUICKLY CROSS FROM THE NORTHWEST EARLY SUNDAY. && .NEAR TERM /THROUGH TONIGHT/... A DEEP UPPER LOW CENTER IS TRANSLATING QUICKLY EWD INTO THE CENTRAL APPALACHIANS EARLY THIS MORNING. THE ASSOCIATED COLD FRONT EXTENDING S OF THIS FEATURE IS SCOURING LOW LEVEL MOISTURE ACROSS THE PIEDMONT...WITH STRONG COLD ADVECTION ALREADY STARTING ACROSS MUCH OF THE CWFA. THE TWO MAIN FORECAST ISSUES ARE SNOW AND WIND. FIRST THE SNOW. IN ADDITION TO STEADILY IMPROVING NW FLOW MOISTURE TODAY...WITH A DECENT GREAT LAKES CONNECTION...UPPER JET DIVERGENCE WILL ALSO TRAVERSE WRN NC. SNOW SHOWERS WILL INCREASE IN THE TYPICAL NW FLOW PRONE LOCATIONS...BUT VERY STRONG FLOW ALONG WITH THE UPPER JET SUPPORT COULD PUSH ISOLATED TO SCATTERED SNOW SHOWERS EWD INTO THE PIEDMONT ALONG INTERSTATE 40 TODAY. ANY ACCUMULATING SNOWFALL SHOULD BE CONTAINED MAINLY WITHIN THE CURRENT WINTER STORM WARNING AREA...AS NW FLOW MOISTURE DEEPENS ALONG THE SPINE OF THE SRN APPALACHIANS AND CONTINUES INTO TONIGHT. ALTHOUGH MODEL QPF IS NOT TREMENDOUS WITH THIS EVENT...THE STRENGTH AND DEPTH OF THE NW FLOW MOISTURE...ALONG WITH INSTABILITY IN THE FLOW...SHOULD PRODUCE STORM TOTAL SNOWFALL OF 5 OR 6 INCHES NEAR THE TN BORDER TODAY THROUGH TONIGHT...WITH 2 TO 3 INCHES IN EXTREME SE PARTS OF THE WARNING AREA. WINDS WILL BE THE BIGGER ISSUE FOR MUCH OF THE AREA. DECENT MODEL CONSENSUS EXISTS ON 850 MB WIND SPEEDS EXCEEDING 50 KT BY 12Z THIS MORNING...WITH H85 MAXIMUM FLOW IN THE COLD ADVECTION POSSIBLY REACHING 60 KT LATER THIS AFTERNOON. MODEL TIME HEIGHTS SHOW TREMENDOUS DOWNWARD OMEGA ALONG THE BLUE RIDGE TODAY...POSSIBLY ENHANCED BY FRONTOGENESIS DUE TO DOWNSLOPE WARMING JUST EAST OF THE ESCARPMENT. WITH 70 KT WINDS AT 700 MB BY 18Z TODAY...AND 100 KT AT 500 MB...DOWNWARD MOMENTUM TRANSPORT WILL BE FANTASTIC DURING PEAK MIXING. WILL CONTINUE TO ADDRESS THE HIGH WIND THREAT IN THE WINTER STORM WARNING WHERE APPLICABLE. ELSEWHERE...HAVE ALREADY UPGRADED THE HIGH WIND WATCH TO A WARNING FROM TOCCOA TO ANDERSON TO SPARTANBURG TO ROCK HILL...WITH A TIER OF ADVISORY WINDS ACROSS THE EXTREME SRN PIEDMONT. DAMAGING WIND GUSTS IN THE WARNING AREA COULD BE REMINISCENT OF MARCH 7 2004...WITH WIDESPREAD DOWNED TREES AND POWER LINES...ESPECIALLY ACROSS WRN NC. WILL ALSO MENTION SOME MINUS 5 C WIND CHILL VALUES AT HIGHER ELEVATIONS FOR BOTH THIS MORNING AND EARLY THURSDAY MORNING IN THE WARNING PRODUCTS. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... AS OF 3 AM WEDNESDAY...MOIST NORTHWEST FLOW WILL OVERLAP INTO THE DAYTIME HOURS ON THURSDAY. SCT SHSN SHOULD CONTINUE TO DEVELOP OVER THE WESTERN SLOPES OF THE NRN NC MTNS THURSDAY MORNING. DRY HIGH PRESSURE WILL MOVE EAST THE CENTRAL MISSISSIPPI RIVER THURSDAY AFTERNOON. BY 18Z...FORECAST SOUNDINGS INDICATE DEEP DRYING ALOFT...WITH ENOUGH LLVL MOISTURE TO SUPPORT SOME UPSLOPE CLOUDINESS. MTN WINDS WILL ALSO REMAIN QUITE GUSTY DURING THE MORNING HOURS. WINDS WILL WEAKEN ACROSS THE FORECAST AREA AS HIGH PRESSURE APPROACHES DURING THE AFTERNOON. NORTHWEST FLOW WILL KEEP LLVL TEMPERATURES AND THICKNESSES FAIRLY CHILLY ACROSS THE WESTERN CAROLINAS THURSDAY AFTERNOON. HOWEVER...H85 TEMPS WILL TREND WARMER THROUGH THE DAY. GIVEN SOME REBOUND IN THE THERMAL PROFILE AND INCREASE INSOLATION...TEMPERATURES WILL GENERALLY WARM 5 DEGREES ABOVE TODAY/S FORECAST VALUES. REMAINING NEARLY 10 DEGREES BELOW NORMAL. SKY COVER WILL REMAIN FAIRLY THIN THURSDAY EVENING...HIGH CLOUDS WILL ADVANCE WEST TO EAST ACROSS THE CWA DURING THE PRE DAWN HOURS. LIGHT WINDS AND COOL LLVL THICKNESS...TEMPS SHOULD FALL INTO THE 20S ACROSS THE FORECAST AREA BY FRI MORNING. CLOUDS WILL STEADILY THICKEN AND LOWER THROUGH THE DAYTIME ON FRIDAY. THE TIMING OF THE CLOUD COVER WILL KEEP TEMPS FROM WARMING STEADILY FROM LOW MORNING TEMPERATURES. I WILL FORECAST VALUES ONLY A DEGREE OR SO FROM THURSDAY/S VALUES. HPC PREFERS A BLEND OF THE ECMWF AND UKMET FRI NIGHT AND SAT. BY THIS TIME...A CLOSED LOW THAT ORIGINATED OVER SOUTHERN CA AND THE DESERT SW WILL OPEN TO A S/W AND TRACK ACROSS THE DEEP SOUTH. THE CENTER OF THE SFC LOW IS EXPECTED TO TRACK ACROSS THE NORTHERN SHORE OF GULF AND ACROSS THE FL. THE ECMWF INDICATES THAT A PERIOD OF Q VECTOR CONVERGENCE WILL FORM WELL NORTH OF THE SFC LOW AND WILL MOVE WEST TO EAST ACROSS NE GA AND THE SC UPSTATE LATE FRIDAY EVENING INTO THE EARLY MORNING HOURS OF SAT. MODEL QPF IS LESS THAN A .10 OF AN INCH...BUT COMPARES WELL WITH THE PLACEMENT OF NAM...UKMET...GEM...SREF PLUME QPF. I WILL FAVOR CHC POPS MAINLY ACROSS NE GA...SC UPSTATE...AND NC ZONES SOUTH OF I-40. TEMPERATURES WILL GENERALLY REMAIN AT OR BELOW FREEZING DURING THE QPF...YIELDING A TOTAL -SN EVENT. LITTLE TO NO ACCUMULATION EXPECTED. THE LOW AND UPPER FORCING WILL DEPART AFTER SUNRISE SATURDAY...I WILL END POPS QUICKLY DURING THE MORNING. HIGH TEMPERATURES SHOULD REMAIN AROUND 10 DEGREES BELOW NORMAL. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... AS OF 250 AM WEDNESDAY...STARTING 00Z SUNDAY WILL BE BETWEEN SYSTEMS AND NOTHING GOING ON IN THE EARLY SATURDAY NIGHT TIME. GOING INTO SUNDAY MORNING...BOTH THE GFS AND ECMWF HAVE A CUT OFF 500MB LOW ROUGHLY OVER ILLINOIS WITH THE ECMWF BEING A BIT FASTER. BOTH OF THESE MODELS ARE VIGOROUS WITH THE PRECIP SHIELD ADVANCING ACROSS TENNESSEE. IN COMPARISON TO THE GEM...WHICH ROTATES THIS CUT OFF LOW FEATURE FROM KANSAS TO ARKANSAS LATER...00Z MONDAY TO 12Z MONDAY...AND THEN FADES IT OUT NEAR OUR AREA BY 00Z TUESDAY. STICKING WITH A COMBINATION OF GFS AND ECMWF...ONCE THE CUT OFF LOW IS PASSING NEAR OUR AREA WHICH WOULD BE SUNDAY NIGHT...MOISTURE WILL TEND TO LINGER ALONG THE WESTERN SLOPES OF THE APPALACHIANS TO AROUND 00Z TUESDAY AND POSSIBLY EVEN LATER INTO MONDAY NIGHT. UPPER TROFINESS CONTINUES INTO MID WEEK...BUT SURFACE HIGH PRESSURE WILL PREVAIL TO END THE SEVEN DAY FORECAST. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
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AT KCLT...NW WINDS HAVE ALREADY BEGUN TO GUST AT TAF TIME THIS MORNING. GUSTS SHOULD INCREASE RAPIDLY TO 35 KT THROUGH 15Z...THEN LIKELY EXCEED 40 KT AT TIMES THROUGH THE AFTERNOON AND EARLY EVENING HOURS. ISOLATED GUSTS UP TO 50 KT WILL BE POSSIBLE DURING PEAK MIXING LATE THIS AFTN. WINDS WILL STEADILY DIMINISH OVERNIGHT. TOWER PERSONNEL SHOULD CLOSELY MONITOR WINDS TODAY IN CASE TOWER EVACUATIONS BECOME NECESSARY DUE TO HIGH WINDS. AT KAVL...RETURNING NW FLOW MOISTURE BEHIND THE FRONT WILL YIELD MAINLY VFR CIGS THROUGH THE MORNING...WITH MVFR CIGS INCREASINGLY LIKELY THROUGH THE AFTERNOON HOURS. A SNOW SHOWER IS POSSIBLE IN THE VICINITY. WINDS WILL BE THE MAIN ISSUE...AS GUSTS ABOVE 45 KT ARE EXPECTED WITH PEAK MIXING FROM LATE MORNING THROUGH THE AFTERNOON HOURS. TOWER PERSONNEL SHOULD CLOSELY MONITOR THE WIND SPEEDS TODAY AS A SAFETY PRECAUTION. WINDS WILL DIMINISH VERY SLOWLY OVERNIGHT. ELSEWHERE...SCATTERED STRATOCUMULUS ARE EXPECTED THROUGHOUT THE DAY IN STRENGTHENING NW FLOW COLD ADVECTION...EXCEPT VFR CIGS ARE MORE LIKELY AT KHKY THIS AFTERNOON. WIND GUSTS MAY APPROACH 40 KT WITH PEAK MIXING THIS AFTERNOON. ISOLATED GUSTS OF 40 TO 50 KT BY EARLY EVENING CANNOT BE RULED OUT...ESPECIALLY AT KHKY. TOWER PERSONNEL SHOULD CLOSELY MONITOR THE WIND SPEEDS TODAY AS A SAFETY PRECAUTION. OUTLOOK...WIND SPEEDS WILL DIMINISH THURSDAY AS DRIER HIGH PRES BUILDS IN FROM THE WEST. VFR CONDITIONS SHOULD THEN CONTINUE THROUGH THE REST OF THE OUTLOOK PERIOD.
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&& .GSP WATCHES/WARNINGS/ADVISORIES... GA...HIGH WIND WARNING UNTIL 6 AM EST THURSDAY FOR GAZ010-017-018. WIND ADVISORY UNTIL 6 AM EST THURSDAY FOR GAZ026-028-029. NC...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR NCZ033- 048>053-058-059-501-503-505. HIGH WIND WARNING UNTIL 6 AM EST THURSDAY FOR NCZ035>037-056- 057-062>065-068>072-082-502-504-506>510. SC...HIGH WIND WARNING UNTIL 6 AM EST THURSDAY FOR SCZ001>010. WIND ADVISORY UNTIL 6 AM EST THURSDAY FOR SCZ011>014-019. && $$ SYNOPSIS...DEO NEAR TERM...HG SHORT TERM...NED LONG TERM...DEO AVIATION...HG

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