504 FXUS62 KGSP 280605 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 205 AM EDT FRI MAR 28 2014 .SYNOPSIS... A MOIST FRONTAL SYSTEM WILL AFFECT THE AREA FRIDAY THROUGH SATURDAY. STRONG UPPER LEVEL RIDGING WILL BUILD IN DRY AND WARM HIGH PRESSURE SUNDAY...WHICH WILL REMAIN ACROSS THE REGION INTO THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TODAY/... 115 AM UPDATE...PCPN NOW ADVANCING THRU THE UPPER TENN VALLEY IN WEAK AND ELEVATED WARM ADVECTION UNDER CYCLONIC FLOW ALOFT. THIS ACTIVITY WAS SUGGESTED BY SOME SHORT TERM GUIDANCE TO WEAKEN AS IT APPROACHED THE MTNS...WITH THE BETTER UPPER FORCING RIDING UP TOWARD WEST VIRGINIA. THIS APPEARS TO BE THE CASE. NONETHELESS MOIST UPGLIDE SCHEME STRENGTHENS TOWARD DAWN ACRS THE BLUE RIDGE. WHILE I INITIALLY BRING IN SCHC POPS TO ACCOUNT FOR ANY LIGHT PCPN FROM THE EXISTING SHIELD...POPS RAMP UP MORE AGGRESSIVELY TOWARD 12Z. AT 1000 PM EDT THURSDAY...AN UPPER TROUGH AXIS WAS OVER THE WESTERN USA...WHILE AN UPPER RIDGE WAS ALONG THE EAST COAST. A SHORTWAVE WAS MOVING THROUGH THE TROUGH AXIS OVER THE MID MS RIVER VALLEY. THIS SHORTWAVE IS EXPECTED TO REACH THE LOWER GREAT LAKES BY DAYBREAK. A COLD FRONT NOW LEAVING THE EASTERN PLAINS IS EXPECTED TO REACH THE OH RIVER VALLEY BY DAWN. SATELLITE IMAGERY SHOWS LIMITED CLOUD COVER OVER THE WESTERN CAROLINAS AND NE GA...BUT CIRRUS ASSOCIATED WITH UPSTREAM CONVECTION WAS ENCROACHING FROM THE WEST. MODEL TIME HEIGHTS SHOW LOW LEVEL MOISTURE ARRIVING STARTING LATE THIS EVENING ON A SOUTHERLY FLOW. THIS FLOW WILL HAVE AND UPSLOPE COMPONENT INTO THE SOUTH FACING BLUE RIDGE ESCARPMENT... AND AN ISENTROPIC UPGLIDE COMPONENT OVER THE LINGERING EAST COAST SURFACE RIDGE. PRECIPITATION ASSOCIATED WITH THIS LIFT IS EXPECTED TO REACH THE AREA BEFORE DAWN. THE MODELS SUPPORT FAIRLY STRONG WINDS AT HIGH MOUNTAIN ELEVATIONS OVERNIGHT...PERHAPS REACHING ADVISORY CRITERIA ON THE VERY HIGHEST PEAKS IN WESTERN NC. LOWS WILL RANGE FROM THE MID AND UPPER 30S IN THE HIGH ELEVATIONS TO THE 40S ACROSS THE FOOTHILLS AND PIEDMONT. PRECIPITATION WILL SPREAD QUICKLY TO THE EASTERN ZONES DURING THE MORNING AND EARLY AFTERNOON. BEFORE THE END OF THE DAY... WESTERN AND SOUTHWESTERN LOCATIONS SHOULD HAVE BETWEEN ONE HALF INCH TO AN INCH OF RAIN. PRECIPITATION TYPE WILL NOT BE A PROBLEM... EVEN IN THE MOUNTAINS WHERE SIGNIFICANT WARM AIR ADVECTION IS ALREADY UNDERWAY. THE TEMPERATURE RISE WILL BE TEMPERED BY THE CLOUD COVER AND PRECIPITATION ON FRIDAY WITH HIGHS IN THE MID AND UPPER 50S WITH 60S ACROSS THE SOUTHERN AND EASTERN ZONES. && .SHORT TERM /TONIGHT THROUGH SUNDAY/... AS OF 200 PM THURSDAY...MAIN FOCUS FOR THE SHORT TERM WILL BE THE COLD FRONTAL PASSAGE DURING SATURDAY. AT THE ONSET OF THE PERIOD FRI NIGHT...WIDESPREAD RAIN SHOWERS SHOULD BE ONGOING WITH A MOIST GULF FLOW BEING LIFTED BY WEAK ISENTROPIC UPGLIDE AND THE HIGHER TERRAIN. WITH UPPER SUPPORT LACKING FRI NIGHT...DO NOT BELIEVE THAT QPF WILL BE EXCESSIVE. ON SAT...12Z MODEL SUITE IN FAIRLY GOOD AGREEMENT THAT LOW PRESSURE WILL MOVE THROUGH THE OHIO VALLEY WITH A TRAILING COLD FRONT MOVING ACROSS THE AREA FROM WEST TO EAST. THE FRONT SHOULD MOVE EAST OF THE I-77 CORRIDOR IN THE 20Z-23Z TIMEFRAME. HENCE...WILL CONTINUE WITH IDEA OF NUMEROUS SHOWERS AND EVEN SCATTERED THUNDERSTORMS. IT APPEARS THAT CLOUDINESS AHEAD OF THE FRONT WILL LIMIT THE AMOUNT OF CAPE TO ABOUT 400-600J. BULK SHEAR IS FORECAST TO INCREASE DURING SAT...BUT UPPER WINDS ALSO BECOME MORE UNIDIRECTIONAL AS THE DAY PROGRESSES SO SEVERE THREAT DOES NOT LOOK ALL THAT GREAT. SPC HAS INDICATED THE SEVERE THREAT SHOULD BE PRIMARILY EAST AND SOUTH OF OUR AREA WHICH LOOKS REASONABLE. SHOWERS AND STORMS WILL END QUICKLY IN THE I-77 CORRIDOR SAT EVENING AS FRONT MOVES TO THE EAST. HOWEVER...THERE MAY BE A BRIEF NW FLOW SNOW EVENT IN THE MOUNTAINS SAT NIGHT AS TEMPS DROP AND WINDS BECOME FAVORABLE. PLUS...THE NORTHERN MOUNTAINS MAY BE BRUSHED BY THE UPPER LOW'S DEFORMATION ZONE. THEREFORE...HAVE INDICATED SHOWERS...CHANGING TO SNOW SHOWERS THERE RIGHT NOW ANY SNOW ACCUMS SHOULD BE LESS THAN 1 INCH. ALSO...WINDS WILL BECOME GUSTY SAT NIGHT INTO SUN AS SUBSIDENCE MIXES DOWN HIGHER SPEEDS ALOFT. TEMPS WILL BE ABOVE AVERAGE THROUGH SAT AND THEN COOL TO NEAR NORMAL VALUES ON SUN. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 200 PM EDT THURSDAY...NOT TOO MUCH CONTROVERSIAL EXPECTED THROUGH THE MEDIUM RANGE. WEATHER SHOULD BE QUIET SUNDAY NIGHT AND MONDAY AS AN UPPER RIDGE BUILDS IN FROM THE WEST...SUPPORTING DRY HIGH PRESSURE THAT MOVES IN OVER THE SOUTHEAST. MIGHT BE SOME CONCERN FOR FROST EAST OF THE MTNS SUNDAY NIGHT WITH CLEARING SKY AND LIGHT WIND ALLOWING TEMPS TO DROP INTO THE MID/UPPER 30S. HIGH TEMPS MONDAY WILL REBOUND BY AS MUCH AS TWO CATEGORIES COMPARED TO SUNDAY...SO ANOTHER WARM EARLY SPRING DAY IS EXPECTED. THE MODELS INDICATE THE PASSAGE OF A SHORT WAVE ON TUESDAY MORNING BUT THE OVERALL UPPER RIDGE AXIS REMAINS ALONG THE EAST COAST. THIS WAVE WILL HAVE VERY LITTLE MOISTURE TO WORK WITH...SO NOT MUCH MORE THAN A SLIGHT CHANCE OF SHOWERS OVER THE HIGHER TERRAIN IS EXPECTED. THE UPPER RIDGE AXIS MIGRATES SLOWLY OFF THE EAST COAST DURING THE MIDDLE OF THE WEEK WHICH WILL PUSH THE SURFACE HIGH OUT OVER THE ATLANTIC. AS A RESULT...SOME RETURN FLOW OF MOISTURE FROM THE GULF SHOULD STRENGTHEN AHEAD OF THE NEXT SHORT WAVE...WHICH THE MODELS SHOW MOVING IN FROM THE WEST ON THURSDAY AFTERNOON. THIS WAVE WILL HAVE MUCH MORE MOISTURE TO WORK WITH. ALTHOUGH THE SURFACE FRONT WILL REMAIN WELL TO THE NORTHWEST...THERE WILL BE SOME UPPER SUPPORT FOR SHOWER DEVELOPMENT TO GO ALONG WITH SOME INSTABILITY. PRECIP CHANCES RAMP UP TO THE CHANCE RANGE FROM THE WEST THROUGH THURSDAY AFTERNOON...WITH PERHAPS SOME THUNDERSTORMS E OF THE MTNS. TEMPS WILL BE ABOVE NORMAL. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AT KCLT...BKN CIRRUS WILL BE SEEN UNTIL LOW VFR STRATOCU MOVE IN EARLY THIS AM...THE LATTER CLOUDS MAINLY COMING FROM DECAYING PCPN SHIELD COMING OUT OF THE TENN VALLEY. MEANWHILE LLVLS MOISTEN ON STRENGTHENING SOUTHERLY WINDS AND UPGLIDE. THERE REMAINS SOME THREAT FOR AN IFR STRATUS DECK TO DEVELOP NEAR DAYBREAK...BUT THIS IS NOT WELL AGREED UPON BY GUIDANCE. MOISTURE PROFILE HOWEVER SUPPORTS IT. SHOWERS WILL PREVAIL FROM MID MORNING ONWARD...BRINGING CIGS DOWN TO MVFR. THERE MAY BE SOMEWHAT OF A BREAK DURING THE AFTN ALLOWING SOME IMPROVEMENT IN FLT CAT...BUT AFTER SUNSET CONDITIONS WILL AGAIN WORSEN WITH MOIST FRONTAL BOUNDARY STILL NEARBY. WINDS WILL CONTINUE FROM THE S BUT STRONG 850MB JET MAY CAUSE LLWS ISSUES IN THE AREA. ELSEWHERE...GENERALLY VFR THROUGH THE EARLY AM THOUGH CIGS WILL GRADUALLY LOWER TO MVFR THRU THE MORNING...OCCURRING BY AROUND 15Z IF NOT SOONER AS MOISTURE TRANSPORT AND PRECIP COVERAGE MAXIMIZES. SOME IFR POSSIBLE AT TIMES DURING THE HEAVIEST PRECIP. A LULL MAY COME DURING THE AFTN...PERHAPS ALLOWING BETTER FLT CATS FOR A TIME...BUT PRECIP WILL AGAIN INCREASE IN COVERAGE THIS EVENING AND CIGS/VSBY AGAIN LOWER. WINDS WILL CONTINUE SOUTHERLY BUT LLWS IS LIKELY TO BE PRESENT AT LEAST SPORADICALLY THRU THE MORNING. OUTLOOK...SHOWERS AND POSSIBLY THUNDERSTORMS LATE FRIDAY NIGHT AND SATURDAY. VFR BUT WINDY ON SUNDAY. VFR WEATHER MONDAY. RESTRICTIONS IN SHOWERS POSSIBLE WHEN A COLD FRONT APPROACHES TUESDAY. VFR WEDNESDAY. CONFIDENCE TABLE... 06-12Z 12-18Z 18-24Z 00-06Z KCLT HIGH 99% HIGH 83% HIGH 93% HIGH 95% KGSP MED 67% HIGH 83% MED 72% HIGH 91% KAVL HIGH 84% MED 74% HIGH 95% HIGH 100% KHKY HIGH 86% HIGH 96% HIGH 98% HIGH 100% KGMU MED 65% HIGH 80% MED 72% HIGH 91% KAND HIGH 90% MED 62% HIGH 88% 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...SBK NEAR TERM...JAT/LGL/WIMBERLEY SHORT TERM...LG LONG TERM...PM AVIATION...WIMBERLEY