Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 031757 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1257 PM EST TUE MAR 3 2015 .SYNOPSIS... COOL CANADIAN HIGH PRESSURE WILL BUILD INTO THE REGION TODAY... BUT MOIST AND MILDER AIR SHOULD BE BACK ON WEDNESDAY AHEAD OF AN APPROACHING COLD FRONT. THIS FRONT IS FORECAST TO PASS THROUGH THE AREA ON THURSDAY...WITH COLD AND DRY HIGH PRESSURE RETURNING FOR FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1230 PM...PATCHES OF LIGHT RAIN AND DRIZZLE CONTINUE TO MOVE EAST MAINLY ACROSS NE GEORGIA AND UPSTATE SC...AND THE SRN PART OF THE CLT METRO AREA. THIS WAS IN GENERAL AGREEMENT WITH SOME OF THE MESOSCALE MODELS. THE LIGHT PRECIP AND CLOUD COVER HAS KEPT TEMPS COOL AND IN LINE WITH PREVIOUS THINKING. NO SIGNIFICANT CHANGES WILL BE MADE. REMAINDER OF PREVIOUS DISCUSSION... OTHERWISE...MAX TEMPS WILL OCCUR AT 12Z AT MOST LOCATIONS DUE TO DEVELOPING COLD AIR DAMMING. THE ONLY EXCEPTION WILL BE THE FAR WESTERN MTN VALLEYS NEAR THE TENN BORDER...WHICH MAY WELL WARM INTO THE 60S THIS AFTERNOON. MEANWHILE...MUCH OF THE PIEDMONT WILL REMAIN STEADY...OR SLOWLY DROP INTO THE 40S AND UPPER 30S BY THIS AFTERNOON. POPS WILL GRADUALLY DIMINISH FROM SOUTH TO NORTH THIS AFTERNOON INTO THIS EVENING...AS THE MOISTURE DEPTH DECREASES...THE BEST UPGLIDE SHIFTS TOWARD THE MID-ATLANTIC... AND THE WEDGE BEGINS ITS GRADUAL EROSION PROCESS. IN FACT...TEMPERATURES SHOULD WARM...AT LEAST SLOWLY...THROUGH THE OVERNIGHT....LIKELY RETURNING TO THE 40S AND 50S BY DAYBREAK WED. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AT 300 AM EST TUESDAY...ON WEDNESDAY MORNING AN UPPER TROUGH WILL EXTEND FROM HUDSON BAY TO NW MEXICO...WHILE AN UPPER RIDGE OVER THE WESTER CARIBBEAN EXTENDS N OF THE EAST COAST OF THE USA. BY THURSDAY THE NORTHERN PORTION OF THE UPPER TROUGH WILL HAVE PROGRESSES INTO EASTERN CANADA. A STRONG SHORTWAVE WILL MOVE THROUGH THE TROUGH FROM THE MS RIVER VALLEY TO THE UPPER OH RIVER VALLEY DURING THE DAY...CROSSING THE SOUTHERN APPALACHIANS BY EARLY EVENING. AT THE SURFACE...ON WEDNESDAY A SLOW MOVING COLD FRONT WILL REACH THE SOUTHERN APPALACHIANS BY MIDDAY...MOVING SOUTHEAST TO THE BLUE RIDGE BY EVENING. THE FRONT REACHES THE INTERSTATE 85 CORRIDOR IN THE MIDDLE OF THE NIGHT... ALTHOUGH MODERATE SHEAR WILL BE PRESENT...ONLY MODEST INSTABILITY ALONG THE BOUNDARY APPEARS TO SUPPORT JUST A FEW THUNDERSTORMS OVERNIGHT. THE FRONT FINALLY MOVES EAST OF OUR ARE BY DAYBREAK TUESDAY. TEMPERATURES WILL RUN ABOVE NORMAL AHEAD OF THE FRONT...FALLING BELOW NORMAL IN ITS WAKE. EXTENSIVE MOISTURE BEHIND THE BOUNDARY WILL SUPPORT PRECIPITATION IN ITS WAKE THROUGH ACROSS THE FOOTHILLS AND PIEDMONT FOR MUCH OF THE DAY ON THURSDAY...WHILE COLD NW FLOW RESULTS IN A CHANGEOVER TO SNOW SHOWERS IN THE NC MOUNTAINS. ON THURSDAY NIGHT THE FRONT MOVES FAR ENOUGH SE TO END PRECIPITATION EAST OF THE MOUNTAINS...AND MOISTURE DIMINISHES ALONG THE TN BORDER...RESULTING IN AND END TO SNOW SHOWERS THERE. && .LONG TERM /FRIDAY THROUGH MONDAY/... AT 300 AM EST TUESDAY...ON FRIDAY MORNING A BROAD UPPER TROUGH WILL EXTEND FROM A CLOSED LOW IN THE CANADIAN ARCTIC TO THE EASTER USA. MEANWHILE AN UPPER LOW WILL BE OVER NW MEXICO... AND A FLAT RIDGE WILL BE OVER THE CARIBBEAN. THIS PATTERN REMAINS THROUGH SATURDAY. BY SUNDAY THE MEXICAN UPPER LOW FILLS AND STARTS TO MOVE INTO THE BASED OF THE UPPER TROUGH. ON MONDAY SHORTWAVE ENERGY MOVING THROUGH THE UPPER TROUGH RESULTS IN AMPLIFICATION OVER THE EASTERN USA. AT THE SURFACE...ON FRIDAY MORNING HIGH PRESSURE CENTERED OVER THE OH RIVER VALLEY WILL EXTEND FROM NY TO TX. A COLD FRONT WILL BE OVER S FL. MOISTURE N OF THE FRONT IS EXPECTED TO BE SUFFICIENTLY FAR ENOUGH S TO KEEP PRECIPITATION OUT OF OUR AREA. THE SURFACE HIGH SETTLES FARTHER SOUTH ON SATURDAY...EXTENDING FROM NC TO TX...WHILE THE FRONT REMAINS IN S FL...AGAIN WITH ITS ASSOCIATED MOISTURE S OF OUR AREA. A COLD FRONT DROPS QUICKLY S ACROSS OUR AREA ON SATURDAY NIGHT...REACHING S GA BY SUNDAY MORNING...APPROACHING THE FIRST FRONT IN FL...WHILE ANOTHER SURFACE HIGH MOVES ACROSS THE OH RIVER VALLEY. ON MONDAY THE SECOND SURFACE HIGH REACHES THE SOUTHEAST...WHILE A STATIONARY FRONT REMAINS IN S FL. THERE ARE SOME INDICATIONS THAT MOISTURE WILL SPREAD NORTH OVER THE FL FRONT TOWARDS OUR AREA EARLY NEXT WEEK S AS SURFACE WAVE DEVELOPS IN THE GULF OF MEXICO. CONFIDENCE IS LOW AT THIS POINT...BUT IT APPEARS THAT ANY WINTER PRECIPITATION WOULD BE CONFINED TO THE MOUNTAINS ON SUNDAY NIGHT. TEMPERATURES WILL AROUND AROUND 15 DEGREE BELOW NORMAL ON FRIDAY IN COLD HIGH PRESSURE...THEN WILL WARM TO AROUND 5 DEGREES BELOW NORMAL ON SATURDAY AND SUNDAY...FINALLY REACHING NEAR NORMAL BY MONDAY. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... AT KCLT...A DIFFICULT SITUATION FOR THE AFTERNOON...AS SOME VARIABILITY IS EXPECTED WITH WIND DIRECTION ALTERNATING BACK AND FORTH BETWEEN ENE AND ESE. THE TREND SHOULD BE TOWARD THE WIND VEERING AROUND TO SE LATER TODAY. THE CEILING AND VISIBILITY WILL ALSO BE VARIABLE BETWEEN IFR/MVFR UNTIL EARLY THIS EVENING...WHEN THE MODEL GUIDANCE SUGGESTS WE WILL LOCK IN THE LOW IFR FOR THE OVERNIGHT PERIOD. A LIGHT WIND COMING AROUND TO SE WILL ONLY HELP WITH SOME WEAK MOIST UPGLIDE. AT THE SAME TIME...THE FLOW AT 850 MB WILL STRENGTHEN AS THE CORE OF A LOW LEVEL JET TRANSLATES E ACROSS THE REGION...WHICH SHOULD RESULT IN SOME LOW LEVEL WIND SHEAR DEVELOPING THE PRE-DAWN HOURS. SOME IMPROVEMENT IS EXPECTED IN THE MID TO LATE MORNING WITH BOUNDARY LAYER WARMING AND A REDUCED THREAT OF LIGHT PRECIP. ELSEWHERE...SIMILAR TO KCLT. THE NE WIND MAY HOLD ON THE LONGEST AT KHKY...BUT MOST PLACES OUTSIDE THE MTNS WILL KEEP A PREVAILING NE WIND UNTIL SOME TIME IN THE EARLY EVENING...AROUND 02Z...WHEN WIND WILL PROBABLY GO LIGHT AND VARIABLE. GUIDANCE IS QUITE PESSIMISTIC WITH IFR/LIFR CONDITIONS INDICATED. OUTLOOK...A COLD FRONT WILL MOVE SLOWLY THROUGH THE REGION WEDNESDAY THROUGH THURSDAY...BRINGING CHANCES FOR HEAVIER RAINFALL AND LOW CIGS/VSBYS TO THE AREA. VFR CONDITIONS ARE EXPECTED TO RETURN FOR FRIDAY AND SATURDAY. CONFIDENCE TABLE... 13-19Z 19-01Z 01-07Z 07-12Z KCLT HIGH 95% HIGH 100% HIGH 100% HIGH 100% KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 100% KAVL MED 74% HIGH 100% HIGH 100% HIGH 100% KHKY MED 77% 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...JAT NEAR TERM...JDL/PM SHORT TERM...JAT LONG TERM...JAT AVIATION...PM

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