Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 010219 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1015 PM EDT SUN MAY 31 2015 .SYNOPSIS...STRONG HIGH PRESSURE WILL REMAIN OVER THE WESTERN ATLANTIC THROUGH MIDWEEK. THE FLOW AROUND THIS HIGH WILL BRING DEEP MOISTURE ACROSS OUR REGION AS A FRONT APPROACHES FROM THE NORTHWEST. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1015 PM SUNDAY... WE WILL MAINTAIN A CHANCE PROBABILITY OF SHOWERS AND THUNDERSTORMS OVER THE WESTERN PIEDMONT THROUGH AROUND 200 AM... THEN DROP BACK TO MENTION OF AN ISOLATED SHOWER POSSIBLE OVERNIGHT. THE CURRENT SCATTERED SHOWER AND ISOLATED THUNDERSTORMS WERE OUTFLOW DRIVEN AND CONFINED TO THE WESTERN PIEDMONT... MOVING NE AT 40 MPH. SEVERAL WEAK OUTFLOW BOUNDARIES CONTINUE TO FOCUS NEW DEVELOPMENT IN THE NARROW BAND OF INSTABILITY LOCATED OVER THE WESTERN PIEDMONT. THE SEA BREEZE BOUNDARY ALONG WITH HIGHER DEW POINTS WILL ADVANCE INTO THE WESTERN PIEDMONT LATE EVENING. THUS... AN UPTICK IN SCATTERED CONVECTION MAY OCCUR. THE MID/UPPER RIDGE AXIS CONTINUED TO EXTEND NW FROM THE WESTERN ATLANTIC OVER CENTRAL NC THIS EVENING. EASTERN AREAS UNDER THE RIDGE SHOULD CONTINUE TO HAVE NEARLY NIL POP OVERNIGHT. CONVECTIVE ACTIVITY SHOULD BECOME MUCH MORE ROBUST AND WIDESPREAD IN THE WESTERN PIEDMONT MONDAY AS THE THE MOISTURE INCREASES ALONG WITH INCREASING CAPE. FORECAST SOUNDINGS AND SREF PROBABILITIES INDICATE A FAIRLY GOOD CHANCE OF SOME FOG/LOW STRATUS IN THE TRIAD OVERNIGHT TONIGHT AND INTO MONDAY MORNING. THE FORECAST IS LESS CERTAIN FOR POINTS EAST BUT THERE REMAINS AN OUTSIDE CHANCE OF SOME BRIEF REDUCTIONS IN CEILING AND VISIBILITY NEAR DAYBREAK. STRATUS COULD LAST PAST DAYBREAK MONDAY MORNING IN THE TRIAD. LOWS TONIGHT IN THE UPPER 60S TO AROUND 70. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... AS OF 307 PM SUNDAY... A PATTERN CHANGE WILL FINALLY BE IN THE MAKING ON MONDAY AS AN UPPER LEVEL LONG WAVE TROUGH DIGS INTO THE MISSISSIPPI VALLEY. THIS WILL PUSH THE SURFACE FRONTAL ZONE EASTWARD ON MONDAY AND INCREASING THE CHANCES FOR PRECIPITATION ACROSS THE ENTIRE CWA...BUT STILL MORE FOCUSED IN THE WESTERN HALF. MODELS VARY ON HOW GOOD CONDITIONS WILL BE WITH THE NAM A BULLISH OUTLIER AT THIS TIME SHOWING 1800 J/KG OF INSTABILITY OVER THE WESTERN PIEDMONT BUT STILL HAS BULK SHEAR VALUES OF ONLY ABOUT 10 KTS. THE GFS BACKS THIS DOWN TO ABOUT 1000 J/KG AND 10 KTS WHICH IS PROBABLY CLOSER TO REALITY. REGARDLESS THERE WILL BE PLENTY OF LOW LEVEL MOISTURE TO WORK WITH AS FORECAST SOUNDINGS SHOW SATURATION TO UP ABOVE 700 MB. LAPSE RATES WILL BE BEST IN THIS SATURATED LAYER AS WELL. WITH INVERTED V SIGNATURES PRESENT ON THE SOUNDING AND SOME DRY AIR AT THE SURFACE...SOME WET MICROBURST ACTIVITY IS NOT OUT OF THE QUESTION. FURTHERMORE DECENT CAPE IN THE HAIL GROWTH ZONE AND A FAIRLY LOW FREEZING LEVEL AT 11000 FEET OR SO COULD ALSO PRODUCE SOME SMALL HAIL. AS A RESULT THE STORM PREDICTION CENTER HAS PUT THE CWA IN A MARGINAL RISK FOR SEVERE WEATHER ON DAY 2. CHANCES DECREASE SIGNIFICANTLY EAST OF US 1 WHERE WE CAN PROBABLY EXPECT MORE OF A DAY LIKE TODAY WITH SOME LINGERING SHOWERS OR THUNDERSTORMS BUT OVERALL NOT A VERY IMPACTFUL DAY. WITH OBVIOUSLY MORE CLOUD COVER IN THE WEST...EXPECT THE HIGHEST TEMPERATURES MONDAY AFTERNOON IN THE EAST WITH UPPER 80S TO LOW 90S EXPECTED. MID TO UPPER 80S IN THE NORTHWEST PIEDMONT. WITH THE FRONTAL ZONE LINGERING JUST EAST OF THE CWA...THE CHANCE FOR SHOWERS AND STORMS WILL CONTINUE THROUGH MONDAY NIGHT WITH THE USUAL DIURNAL LIMITATIONS AND NOT MUCH FORCING ALOFT TO HELP IT OUT BUT SOME WEAKER SHOWERS ARE DEFINITELY A POSSIBILITY. LOWS MONDAY NIGHT MAINLY IN THE MID TO UPPER 60S. && .LONG TERM /TUESDAY THROUGH SUNDAY/... AS OF 305 PM SUNDAY... BETTER-THAN-USUAL SHOWER/STORM CHANCES FOR THE FIRST FEW DAYS OF THIS STRETCH. THE APPROACHING TROUGH WILL HAVE SPLIT BY TUE WITH THE POTENT NRN STREAM SHORTWAVE CROSSING SRN QUEBEC INTO NEW ENGLAND CUTS OFF OVER THE TN VALLEY. AREAS JUST WEST AND SOUTH OF CENTRAL NC STAND TO SEE THE GREATEST FORCING FOR ASCENT FROM MID LEVEL DPVA (ALBEIT WEAK BASED ON THE WEAK MID LEVEL FLOW) AND UPPER DIVERGENCE THROUGH EARLY TUE... BUT THIS WEAK DYNAMIC FORCING WILL BE SPREADING EAST WITH THE SLOW EASTWARD WOBBLE/DRIFT OF THE LOW THROUGH WED. THE SURFACE COLD FRONT IS EXPECTED TO EXTEND FROM JUST SOUTH OF NYC DOWN THROUGH THE SRN APPALACHIANS TO AL EARLY TUE... WITH A WEAK LEE TROUGH EXTENDING THROUGH CENTRAL NC... OVER THE ERN PIEDMONT AND COASTAL PLAIN. WE`LL BE WITHIN THE THERMAL/MOISTURE RIDGE TUE WITH WEAK FLOW AND PW OVER 150% OF NORMAL... BUT SLIGHTLY DRIER AIR WILL BE LOCATED ALONG OUR EASTERN EDGE... STILL UNDER THE INFLUENCE OF THE STUBBORN WRN ATLANTIC MID LEVEL RIDGE. SREF PLACES A 70-90+% OF MEASURABLE PRECIP OVER THE WRN HALF OF THE CWA TAPERING TO LESS THAN 50% IN THE EXTREME EAST ON TUE. GFE MUCAPE FORECASTS ARE FOR 500- 1000 J/KG OVER MUCH OF CENTRAL NC (BIT HIGH ON THE NAM) BUT WITH JUST 10-15 KTS OF DEEP LAYER BULK SHEAR. GIVEN THESE INDICATORS... WILL HAVE 70% CHANCES FOR SHOWERS/STORMS LATE MORNING THROUGH MID EVENING IN THE WRN CWA TAPERING TO 40-50% EAST. ACTIVITY SHOULD DECREASE IN INTENSITY AND COVERAGE BY MIDNIGHT TUE NIGHT BUT IS LIKELY TO PERSIST GIVEN THE LINGERING MARGINAL ELEVATED INSTABILITY THROUGH THE NIGHT AND LOW LEVEL MOISTURE POOLING ALONG THE PIEDMONT TROUGH. MODELS FAVOR DIPPING THE SURFACE FRONT SOUTHWARD INTO FAR NRN AND NW NC EARLY WED... PUSHED BY A COOLER SURFACE HIGH CROSSING THE NORTHEAST STATES AND RIDGING SOUTHWARD... AS INVERTED TROUGHING BECOMES MORE DEFINED ALONG THE COAST. WITH THE UPTICK IN DYNAMIC FORCING FOR ASCENT AND PERSISTENT DEEP MOISTURE WITH A SOUTHEASTERLY LOW LEVEL FLOW... 50-60% POPS WED ARE WARRANTED. ONCE AGAIN... ACTIVITY SHOULD DECREASE BUT NOT END OVERNIGHT. WET CONDITIONS SHOULD CONTINUE THU AS THE LOW STARTS TO OPEN AND TRACK INTO THE SRN APPALACHIANS. PW VALUES WILL REMAIN ABOVE NORMAL WITH CONTINUED MARGINAL TO MODERATE DAYTIME MUCAPE. DEEP LAYER SHEAR WILL STAY WEAK BUT SHOULD BE IMPROVING TO AROUND 20 KTS. GFS AND ECMWF BOTH GENERATE WIDESPREAD MODERATE QPF AREAWIDE WITH ATLANTIC- SOURCE LOW LEVEL FLOW AND A DISSOLUTION OF THE SURFACE FRONT. WILL MAINTAIN HIGH POPS (50-60%) THROUGH THU. FORECAST UNCERTAINTY INCREASES FRI INTO SUN. THE WEAK BAGGY MID LEVEL TROUGH SHIFTS SLOWLY THROUGH OUR REGION FRI... BUT THE GFS THEN DROPS ENERGY BACK INTO THE WEST SIDE OF THE TROUGH... CULMINATING IN ANOTHER CLOSED MID LEVEL LOW OVERHEAD BY SUN. THE ECMWF IN CONTRAST MAINTAINS A VERY WEAK CYCLONIC FLOW OVER THE REGION WITH ONLY VERY WEAK DPVA. BOTH HAVE WEAK SURFACE TROUGHING HOLDING OVER THE SOUTHEAST STATES INCLUDING THE CENTRAL AND EASTERN CAROLINAS THROUGH THE WEEKEND... WITH THE GFS SHOWING LOWERING PW VALUES. EXPECT A TREND TOWARD LOWER COVERAGE WITH MORE TYPICAL SCATTERED DIURNAL SHOWERS AND STORMS FRI-SUN. EXPECT NEAR NORMAL TEMPS TUE WITH THE CLOUDS/PRECIP BALANCING THE ABOVE NORMAL THICKNESSES. TEMPS SHOULD SLIP BACK TO NEAR OR BELOW NORMAL READINGS WED... ESPECIALLY NORTHERN SECTIONS NEAR THE BACKDOOR FRONT. SHOULD SEE TEMPS REBOUND BACK TOWARD NORMAL WITH FRONTOLYSIS AND A RETURN TO A TYPICAL SUMMERTIME REGIME. -GIH && .AVIATION /00Z MONDAY THROUGH FRIDAY/... AS OF 830 PM SUNDAY... 24 HR TAF PERIOD: ISOLD SHOWERS/STORMS WILL REMAIN POSSIBLE AT THE INT/GSO TERMINALS THROUGH 03Z THIS EVENING...THOUGH OVERALL CHANCES WILL DIMINISH 00-03Z WITH THE ONSET OF NOCTURNAL STABILIZATION. EXPECT A POTENTIAL FOR MVFR/IFR CEILINGS OR FOG DURING THE EARLY MORNING HOURS (08-14Z) AT ALL TERMINALS IN ASSOC/W AN INCREASINGLY MOIST SOUTHERLY RETURN FLOW...PARTICULARLY AT THE INT/GSO TERMINALS. WIDESPREAD SHOWERS AND STORMS (PERHAPS ISOLD SEVERE) ARE EXPECTED TO DEVELOP OVER MUCH IF NOT ALL OF CENTRAL NC MONDAY AFTERNOON AND EVENING AS A SLOW MOVING UPPER LEVEL DISTURBANCE TRACKS EAST INTO THE TN VALLEY...WITH THE RELATIVE BEST CHANCE AT THE INT/GSO/RDU TERMINALS. LOOKING AHEAD: ADVERSE AVIATION CONDITIONS ASSOCIATED WITH WIDESPREAD AFT/EVE CONVECTION AND EARLY MORNING STRATUS/FOG ARE EXPECTED TO PREVAIL THROUGH MID/LATE WEEK AS THE AFOREMENTIONED UPPER LEVEL DISTURBANCE STALLS OUT OVER PORTIONS OF THE DEEP SOUTH/TN VALLEY. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...PWB/ELLIS NEAR TERM...PWB/ELLIS SHORT TERM...ELLIS LONG TERM...HARTFIELD AVIATION...VINCENT

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