073 FXUS62 KGSP 040608 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 108 AM EST MON MAR 4 2013 .SYNOPSIS... WEAK HIGH PRESSURE BUILDS IN MONDAY AS A STRONG LOW PRESSURE SYSTEM BEGINS TO MOVE SOUTHEAST THROUGH THE LOWER OHIO VALLEY BRINGING WITH IT ABUNDANT MOISTURE. THE LOW PRESSURE SYSTEM WILL CROSS THE WESTERN CAROLINAS ON WEDNESDAY...WITH HIGH PRESSURE RETURNING THROUGH THE LATE WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1245 AM...IR SATELLITE IMAGERY SHOWS DISSIPATING UPSLOPE CLOUDINESS ALONG THE NC MTN/NE TN BORDER EARLY THIS MORNING...WITH CONSIDERABLE THIN CIRRUS MOVING SE TOWARD THE APPALACHIANS IN THE DEEP LAYER NW FLOW. AN UPPER RIDGE WILL BUILD W OF THE MTN CHAIN TODAY...WITH A WEAK SFC RIDGE IN PLACE ACROSS THE REGION...AND AN EMBEDDED SFC LEE TROUGH JUST EAST OF THE BLUE RIDGE. GIVEN THE RISING HEIGHTS AND GOOD INSOLATION EARLY...TEMPERATURES SHOULD REBOUND SEVERAL CATEGORIES OVER SUNDAY VALUES...BUT STILL REMAIN 5 TO 10 DEGREES BELOW NORMAL. MID AND HIGH CLOUDS WILL THICKEN OVER THE SHALLOW RIDGE AXIS THIS AFTERNOON. MID LEVEL MOISTURE WILL WORK NE ACROSS THE AREA UNDER THE RIDGE AXIS THIS EVENING AS AN UPSTREAM SYSTEM DEVELOPS OVER THE NRN PLAINS. THE GFS IS SLIGHTLY FASTER THAN THE NAM TO BRING RETURNING LOW LEVEL UPGLIDE MOISTURE INTO THE REGION LATE TONIGHT. EVEN THE WETTER GFS...THOUGH...HAS MEASURABLE QPF CONFINED MAINLY TO THE EXTREME SW MOUNTAINS THROUGH DAYBREAK TUE. IT IS POSSIBLE SOME LIGHT FREEZING RAIN COULD BREAK OUT AROUND DAYBREAK IN SPOTS OVER THE CENTRAL MTNS IF THE PRECIP MOVES IN QUICKLY ENOUGH...BUT CONFIDENCE IS TOO LOW TO FEATURE AN ADVISORY. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... AS OF 230 PM SUNDAY...THE SHALLOW UPPER RIDGE WILL BE MOVING EAST AND OUT OF THE AREA MONDAY EVENING. AN UPPER LOW WILL BE OVER THE DAKOTAS AT 00Z TUESDAY AND MOVE TO NC BY 12Z WEDNESDAY. ALTHOUGH THE GFS HAS A TONGUE OF LIGHT PRECIP CROSSING THE NC MTNS AT 00Z TUESDAY...ALL OTHER MODELS HOLD OFF ON INITIAL PRECIP UNTIL AROUND 06Z TUESDAY. NOT ALL GUIDANCE AND MODELS AGREE...BUT STILL FEEL ENOUGH COLD AIR WILL BE IN PLACE ALONG THE SPINE OF THE NC MTNS TO HAVE LIGHT FREEZING RAIN AT THE ONSET OF THIS SYSTEM. AT THIS POINT...A TRACE TO 0.03 ICE ACCUM POSSIBLE FROM BALSAM TO WEAVERVILLE TO NEWLAND UP UNTIL JUST AFTER SUNRISE TUESDAY. AT THAT TIME ALL PRECIP SHOULD QUICKLY CHANGE OVER TO RAIN. SURFACE LOW PRESSURE FORMS OVER ARKANSAS MONDAY NIGHT AND MOVES TO OHIO BY 00Z WEDNESDAY AS THE UPPER LOW REACHES ILLINOIS. THE COLD FRONT EXTENDING SOUTH OF THE SURFACE LOW WILL BE PRECEDED BY INSTABILITY WITH CAPE VALUES IN THE 100 TO 200 RANGE ON THE GFS AND LESS THAN 100 J/KG ON THE NEW ECMWF. SLIGHT CHANCE THUNDER WILL BE CROSSING THE FORECAST AREA AROUND 00Z WEDNESDAY. AFTER THAT...TEMPS DROP TUESDAY NIGHT AND THE RAIN CHANGES OVER TO SNOW IN THE NC MTNS. SNOW SHOWERS CONTINUE ALONG THE TN BORDER THROUGH WEDNESDAY AS RAIN SHOWERS TAPER OFF IN THE PIEDMONT. NOW GOING FOR UP TO 7 INCHES OF SNOWFALL IN THE BULADEAN AND BEECH MTN AREA AS A TOTAL FOR WED AND WED NIGHT. WILL BE QUITE BREEZY TO WINDY BY MID TO LATE DAY WED AS A MORE POWERFUL SURFACE LOW DEEPENS TOWARD THE CAROLINA COAST. HIGH TEMPS AROUND 10 DEGREES BELOW NORMAL TUESDAY AND 15 OR MORE BELOW ON WEDNESDAY. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... AT 230 PM EST SUNDAY...A CLOSED UPPER LOW WILL BE NEAR THE MID ATLANTIC COAST ON WEDNESDAY NIGHT...WHILE A RIDGE WILL BE UPSTREAM OVER THE PLAINS. THIS RIDGE PROGRESSES VERY SLOWLY ON THURSDAY... ONLY CROSSING THE MS RIVER VALLEY ON FRIDAY...AND THE SOUTHERN APPALACHIANS ON SATURDAY. ON SUNDAY THE RIDGE AXIS CROSSES THE EAST COAST...WHILE AN UPPER LOW MOVES INTO THE PLAINS FROM THE SOUTHERN ROCKIES. A SURFACE WAVE WILL MOVE OFF THE CAROLINA COAST SUNDAY NIGHT...WHILE A TIGHT PRESSURE GRADIENT KEEP NW FLOW OVER THE WESTERN CAROLINA AND NE GA...WITH NW FLOW SNOW SHOWERS NEAR THE TN BORDER. ON FRIDAY HIGH PRESSURE MOVES EAST ACROSS THE TN VALLEY AND THE PRESSURE GRADIENT RELAXES. HIGH PRESSURE CROSSES THE APPALACHIANS ON SATURDAY... DRIFTING INTO SC ON SUNDAY...WHILE THE GULF OPENS UP TO MOIST INFLOW BETWEEN THE FL PANHANDLE AND TX. TEMPERATURES WILL WARM WITH RISING HEIGHTS ALOFT...REACHING NEAR NORMAL VALUES NEXT WEEKEND. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... AT KCLT...EXPECT LIGHT NW WINDS AND CLEAR SKIES THIS MORNING AS A WEAK RIDGE AXIS BUILDS INTO THE AREA. MID AND HIGH LEVEL MOISTURE WILL SLOWLY RETURN THROUGH THE REMAINDER OF THE PERIOD. WINDS SHOULD TOGGLE TO WSW EARLY THIS AFTN WITH A LEE TROUGH DEVELOPING E OF THE BLUE RIDGE AND THEN TURN MORE SRLY OVERNIGHT. EXPECT VFR CONDITIONS THROUGH THE PERIOD. ELSEWHERE...VFR CONDITIONS ARE EXPECTED AS MAINLY MID AND HIGH LEVEL CLOUDS SLOWLY INCREASE THIS AFTERNOON THROUGH TONIGHT. THE PRES GRAD WILL CONTINUE TO RELAX...WITH LIGHT NW WINDS BECOMING MORE WSW THEN SW OVER TIME. ANY MOISTURE RETURN IN LOW LEVEL UPGLIDE SHOULD OCCUR LATER TONIGHT...AND ONLY APPROACH KAVL BEYOND THE END OF THE CURRENT TAF PERIOD...WHEN SPOTTY LIGHT FZRA WILL BE POSSIBLE. OUTLOOK...A STRONG LOW PRESSURE SYSTEM WILL APPROACH FROM THE NW ON TUE AND CROSS THE REGION ON WED. DEEP MOISTURE AND PRECIPITATION WILL ACCOMPANY THE SYSTEM...WITH RESTRICTIONS LIKELY AND MIXED PRECIPITATION POSSIBLE TUE NIGHT AND WED...ESPECIALLY FROM KAVL TO KHKY. VFR CONDITIONS SHOULD RETURN ON THURSDAY AND REMAIN INTO THE WEEKEND. CONFIDENCE TABLE... 06-12Z 12-18Z 18-24Z 00-06Z KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 100% KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 100% KAVL HIGH 100% HIGH 100% HIGH 100% HIGH 100% KHKY HIGH 100% HIGH 100% HIGH 100% HIGH 100% KGMU HIGH 100% HIGH 100% HIGH 100% HIGH 100% KAND HIGH 100% HIGH 100% HIGH 100% HIGH 100% THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE) WWW.WEATHER.GOV/GSP/AVIATION_TABLES && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...PAT NEAR TERM...HG SHORT TERM...DEO LONG TERM...JAT AVIATION...HG