000 FXUS62 KGSP 091449 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 949 AM EST THU FEB 9 2012 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH FRIDAY BEFORE A COLD FRONT MOVES ACROSS THE REGION FRIDAY NIGHT THROUGH MID DAY SATURDAY. ANOTHER AREA OF HIGH PRESSURE WILL BUILD BACK IN SATURDAY EVENING AND REMAIN INTO MONDAY. ANOTHER FRONT WILL APPROACH THE AREA FOR UNSETTLED WEATHER BY TUESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 945 AM...A NEW WRINKLE HAS BEEN ADDED TO THE FORECAST FOR TDA AS CLOUDS HAVE STARTED TO DEVELOP EAST OF THE MTNS...FROM GREENVILLE OVER TO GAFFNEY. THE LATEST RUC AND NAM RH FIELDS IMPLY THAT THESE CLOUDS...UP AROUND 4KFT...WILL SPREAD SLOWLY TO THE NORTH THIS MORNING AS WEAK LLVL WARM ADVECTION DEVELOPS OVER THE REGION. THE CLOUDS MAY EVENTUALLY SPREAD ACROSS THE NC FOOTHILLS AND UP ALONG THE E SLOPES OF THE BLUE RIDGE. AT LEAST THAT/S WHAT I/VE DONE IN THE GRIDS. THE 12 UTC GSO SOUNDING SHOWED THE MOIST LAYER AND STRONG SUBSIDENCE INVERSION THAT IS SERVING TO KEEP IT FROM MIXING OUT. OTHERWISE...TWEAKED DEWPOINTS UP A LITTLE EARLY IN THE DAY...THOUGH THEY SHOULD MIX OUT MORE IN THE AFTN. OF COURSE...IF THE CLOUD COVER IS TOO WIDESPREAD...THEN TEMPS AND DEWPOINTS WILL NEED TO BE ADJUSTED. THIS IS LIABLE TO MAKE CONDITIONS EVEN LESS FAVORABLE FOR CONTROLLED BURNS OVER THE FOOTHILLS THIS AFTN. AS OF 615 AM...CLOUDS REMAIN PARKED ALONG THE WESTERN MOUNTAINS IN LINGERING...BUT DIMINISHING...NORTHWEST FLOW MOISTURE. STRATOCUMULUS HAS ALSO MANAGED TO DEVELOP IN THE NRLY FLOW OVER THE NRN NC FOOTHILLS AND PIEDMONT. SKY COVER HAS BEEN INCREASED ALONG AND NORTH OF INTERSTATE 40...BUT THE CLOUDINESS SHOULD NOT MAKE MUCH OF A RUN SOUTHWARD TOWARD CHARLOTTE THIS MORNING GIVEN THE LIGHT DOWNSLOPE FLOW OFF THE MOUNTAINS AND THE DRYING PROFILES. OTHERWISE...SFC HIGH PRES WILL BUILD IN FROM THE WEST TODAY UNDER ZONAL FLOW ALOFT. LEE TROUGHING IS EXPECTED TO DEVELOP AT THE SFC JUST E OF THE BLUE RIDGE TO GIVE WINDS A LIGHT SW FLOW BY THIS AFTN. LITTLE MORE THAN SCATTERED CIRRUS IS EXPECTED ONCE THE NW FLOW MOISTURE QUITS. MAX TEMPS WILL LIKELY BE A CATEGORY BELOW NORMAL THIS AFTN DESPITE THE DECENT INSOLATION. MID AND HIGH CLOUDS MAY THICKEN A LITTLE TONIGHT...BUT MINS SHOULD BE AT OR BELOW GUIDANCE IN THIS COOL AND DRY AIRMASS. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AT 3 AM EST THURSDAY...AN MEAN UPPER TROUGH WILL PERSIST OVER THE EAST FROM FRIDAY THROUGH SATURDAY NIGHT. ON FRIDAY A SHORTWAVE ROUNDING THIS TROUGH WILL MOVE FROM THE SOUTHERN PLAINS TO THE GULF STATES. MEANWHILE...A COLD FRONT WILL FORM IN THE LEE OF THE APPALACHIANS. MOISTURE ALONG THIS FRONT WILL SUPPORT THE DEVELOPMENT OF PRECIPITATION...ESPECIALLY OVER THE MOUNTAINS WHERE A COLD NW UPSLOPE FLOW WILL SET UP LATE IN THE DAY. THE NEW FRONT MOVES RAPIDLY EAST FRIDAY NIGHT...DRYING THE LEE OF THE MOUNTAINS...BUT MOISTURE REMAINS OVER THE NC MOUNTAINS. ANOTHER COLD FRONT ARRIVES ON SATURDAY MORNING...ACCOMPANIED BY MUCH LESS MOISTURE THAN ITS PREDECESSOR. MODEL TIME HEIGHTS SUGGEST PRECIPITATION WILL BEGIN FRIDAY EVENING...PERHAPS EXTENDING EAST OF THE BLUE RIDGE BRIEFLY. AS THE FRONT MOVES EAST...PRECIPITATION WILL BE LEFT ALONG THE TN BORDER INTO SATURDAY NIGHT. MODEL SOUNDINGS SUPPORT A RAIN OR SNOW SCENARIO...WITH PLENTY OF MOISTURE PRESENT AT ICE NUCLEATION TEMPERATURES AND NO WARM NOSE BENEATH. ONLY THE VALLEY FLOORS AND THE FOOTHILLS CAN EXPECT RAIN EARLY FRIDAY EVENING...WITH SNOW LEVELS RAPIDLY DROPPING TO VALLEY FLOORS LATE IN THE EVENING WHILE PRECIPITATION ENDS IN THE FOOTHILLS. SNOW CONTINUES DOWN TO THE VALLEY FLOORS ON SATURDAY...BUT WITH TIME THE EVENT WILL BECOME MORE CONFINED TO THE TN BORDER REGION. AT THIS POINT IT APPEARS THAT ACCUMULATIONS OF 1 TO 2 INCHES MAY BE POSSIBLE ALONG THE TN BORDER...WITH HALF INCH AMOUNTS AT HIGHER ELEVATIONS ALONG THE BLUE RIDGE. TEMPERATURES WILL BE A FEW DEGREES ABOVE NORMAL ON FRIDAY AND FRIDAY NIGHT...FALLING TO A FEW DEGREES BELOW NORMAL ON SATURDAY...AND ALMOST 10 DEGREES BELOW NORMAL ON SATURDAY NIGHT. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 200 AM THURSDAY...THE MEDIUM RANGE FORECAST PICKS UP AT 12Z ON SUNDAY WITH A DEEP UPPER TROUGH AXIS MOVING OFF THE ATLANTIC AND A BROAD UPPER RIDGING PRESENT OVER THE CENTRAL CONUS. THE LATEST MODELS ARE IN GOOD AGREEMENT WITH AN UPPER LVL RIDGE OF HIGH PRESSURE BUILDING OVER THE EASTERN CONUS THROUGH MONDAY BEFORE A SHORTWAVE SWINGS ACROSS THE CAROLINAS MONDAY NIGHT INTO TUESDAY MORNING. ANOTHER UPPER LEVEL RIDGE OF HIGH PRESSURE IS FORECAST TO BUILD ACROSS THE EASTERN STATES THROUGH LATE WEDNESDAY AND A MOIST SOUTHWESTERLY FLOW WILL DEVELOP AHEAD OF A LOW PRESSURE SYSTEM APPROACHING FROM THE WEST THURSDAY. AT THE SFC...DRY WEATHER WITH COOLER TEMPERATURES ARE EXPECTED OVER THE REGION AS A BROAD SURFACE HIGH BUILDS ACROSS THE EASTERN STATES SUNDAY INTO MONDAY. THE LATEST 00Z GFS AND THE ECMWF SHOW BETTER CONSISTENCY WITH THE TIMING OF A WEAK UPPER LEVEL SHORTWAVE SWINGING ACROSS OUR CWFA BETWEEN 12Z AND 18Z TUESDAY. AS THICKNESS VALUES DECREASE QUIT A BIT IN RESPONSE TO THE SHORTWAVE PASSAGE...OVERNIGHT TEMPERATURES WILL BE COLD ENOUGH FOR WINTRY TYPE PCPN ACROSS MUCH OF THE REGION. THEREFORE...I KEPT AT LEAST SLIGHT CHANCE POPS IN FOR SNOW OVER THE MOUNTAINS/FOOTHILLS WITH RAIN SNOW MIX OVER THE LOWER PIEDMONT AREA THROUGH TUESDAY MORNING. ANY WINTRY PCPN WILL SWITCH TO RAIN SHOWERS AFTER SUNRISE AS TEMPERATURES RISE ABOVE FREEZING LVL. ANOTHER SURFACE HIGH WILL BUILD INTO THE REGION FOR DRY CONDITIONS WITH MODERATING TEMPERATURES TUESDAY AFTERNOON INTO WEDNESDAY. THURSDAY...MOIST SOUTHWESTERLY FLOW WILL DEVELOP OVER THE REGION AHEAD OF A LOW PRESSURE SYSTEM APPROACHING FROM THE MISSISSIPPI VALLEYS. INCREASING MOISTURE ALOFT WITH ISENTROPIC LIFTING WILL GENERATE LIGHT PCPN OVER MUCH THE REGION BY THURSDAY AND WILL BECOME MORE ACTIVE FRIDAY AS THE LOW ASSOCIATED WITH A COLD FRONT CROSSES THE CAROLINAS. TEMPERATURES WILL REMAIN 7-10 DEGREES BELOW NORMALS SUNDAY AND MONDAY...THEN STEADILY WARM THROUGH MID WEEK. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... AT KCLT AND KHKY...STRATOCUMULUS HAS MANAGED TO DEVELOP IN A NARROW MOIST ZONE ACROSS THE EXTREME NRN NC FOOTHILLS AND PIEDMONT THIS MORNING. THIS VFR DECK SHOULD NOT MAKE MUCH HEADWAY TO THE SOUTH IN LIGHT NORTHERLY FLOW SINCE PROFILES CONTINUE TO DRY AND 950 TO 850 MB FLOW IS LIGHT DOWNSLOPE FROM THE NW. WILL JUST HINT AT VFR CLOUDS WITH FEW TO SCT040 FOR THE MORNING HOURS. OTHERWISE...EXPECT JUST GRADUALLY INCREASING CIRRUS THROUGH THE PERIOD. LIGHT N TO NE WINDS THIS MORNING WILL TURN S TO SW EARLY THIS AFTERNOON AS A LEE TROUGH DEVELOPS JUST E OF THE MTNS. AT KAVL...PESKY MVFR LEVEL MOISTURE LINGERS THIS MORNING IN THE NW FLOW UP THE FRENCH BROAD VALLEY. CIGS SHOULD LIFT AND SCATTER THROUGH 14Z...WITH JUST CIRRUS REMAINING FOR THE REST OF THE PERIOD. NW FLOW GUSTS SHOULD DIMINISH QUICKLY AROUND ISSUANCE TIME...WITH WINDS BECOMING STEADILY LIGHTER THROUGH THE PERIOD. AT THE UPSTATE SITES...EXPECT FEW TO SCT CIRRUS THROUGH THE PERIOD...WITH LIGHT NE FLOW AROUND A BUILDING SFC HIGH THIS MORNING...THEN LIGHT S TO SW FLOW AHEAD OF LEE TROUGHING THIS AFTERNOON. OUTLOOK...A COLD FRONT WILL APPROACH FROM THE NORTHWEST ON FRIDAY AND MOVE EAST OF THE REGION ON SATURDAY. THE BEST CHANCE OF RESTRICTIONS WILL BE AT KAVL WITH FROPA AND JUST BEHIND IT EARLY SATURDAY. DRY HIGH PRES WILL RETURN SUNDAY THROUGH MONDAY. AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)... WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM && .FIRE WEATHER... A CAUTIONARY NOTE FOR AGENCIES DOING CONTROLLED BURNS ACROSS THE NORTH CAROLINA FOOTHILLS AND BLUE RIDGE TODAY. IF THE CLOUD COVER THAT HAS STARTED TO DEVELOP OVER THE UPSTATE SPREADS NORTHWARD...AS THE MODELS ARE ADVERTISING...TEMPERATURES WILL BE SLOWER TO RISE...MIXING HEIGHTS WILL BE LOWER AND TRANSPORT WINDS WILL BE EVEN LIGHTER THAN THE CURRENT FORECAST. PRESENT INDICATIONS ARE THAT THIS WILL HAPPEN. IF YOU ARE ON THE FENCE ABOUT BURNING...IT/S BEST TO HOLD OFF FOR TODAY. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...JOH NEAR TERM...MCAVOY SHORT TERM...JAT LONG TERM...JOH AVIATION...HG FIRE WEATHER...