Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 310702 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 259 AM EDT SUN MAY 31 2015 .SYNOPSIS...
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BERMUDA HIGH PRESSURE WILL EXTEND OVER THE REGION TODAY BEFORE GIVING WAY TO AN APPROACHING COLD FRONT FROM THE NORTHWEST MONDAY. THE FRONT IS EXPECTED TO STALL OVER THE REGION BY MID WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 255 AM SUNDAY... MID LEVEL RIDGING CURRENTLY OVER EASTERN NC WILL CONTINUE TO SLOWLY SHIFT EASTWARD AS MID LEVEL TROUGH APPROACHES FROM THE WEST. AN ASSOCIATED COLD FRONT WILL REMAIN WELL TO THE WEST AND NORTH OF CENTRAL NC TODAY. HOWEVER... WITH MID LEVEL FLOW BECOMING MORE SOUTHWESTERLY THE POTENTIAL FOR A WEAK DISTURBANCE OR TWO COMBINED WITH SOME WEAK UPSLOPE FLOW WILL LEAD TO A BETTER CHANCE FOR SHOWERS SHOWERS THIS MORNING AND AFTERNOON SHOWERS AND STORMS... PRIMARILY ACROSS THE WESTERN PIEDMONT. HOWEVER... WE MAY SEE SOME SHOWERS AND STORMS DEVELOP ON THE SEABREEZE TODAY AS IT MOVES INTO SOUTHEASTERN/EASTERN COUNTIES THIS AFTERNOON. THE SEVERE THREAT SHOULD REMAIN QUITE MINIMAL AGAIN TO NIL... GIVEN WEAK TO MODEST (AT BEST) MLCAPE... COUPLED WITH WEAK DEEP LAYER SHEAR. THUS... DO NOT PLAN TO MENTION ANY SEVERE THREAT IN THE HWO. HIGH TEMPS WILL AGAIN BE SIMILAR TO YESTERDAY... WITH THE EXCEPTION OF MAYBE A DEGREE OR TWO COOLER IN THE NW PIEDMONT WHERE WE SHOULD SEE A BIT MORE CLOUD COVER AND A BETTER CHANCE OF PRECIP AT TODAY. THUS... WILL GO WITH HIGHS RANGING FROM THE MID TO UPPER 80S ACROSS THE AREA. MOST CONVECTION SHOULD DIE OFF WITH THE LOSS OF DAYTIME HEATING THIS EVENING. OVERNIGHT LOWS SHOULD AGAIN BE GENERALLY IN THE MID TO UPPER 60S.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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AS OF 245 AM SUNDAY... MODEL GUIDANCE CONTINUES TO TREND TOWARD A SLIGHTLY SLOWER ARRIVAL OF BETTER UPPER SUPPORT TO INITIATE/SUSTAIN SCATTERED CONVECTION ON MONDAY. HAVE REFLECTED THIS BY STARTING MONDAY MORNING OUT WITH PARTLY CLOUDY-MOSTLY SUNNY SKIES AND REMOVING SLIGHT CHANCE POP IN THE NW IN THE MORNING. THE ATMOSPHERE DOES BECOME MOIST AND UNSTABLE ENOUGH TO INITIATE SCATTERED CONVECTION OVER THE NW PIEDMONT BY AFTERNOON WITH JUST ISOLATED CONVECTION EXPECTED ELSEWHERE. MODEL GUIDANCE CONTINUES TO COME INTO GOOD CONSENSUS WITH THE SCENARIO OF A CLOSED UPPER LEVEL LOW DEVELOPING OVER THE TN/LOWER MS VALLEY BY TUESDAY MORNING WITH THE TAIL END OF THE NORTHERN STREAM S/W EXTENDING ACROSS VA. THE SFC COLD FRONT ASSOCIATED WITH THE NORTHERN STREAM S/W IS EXPECTED TO DRIFT SOUTH INTO CENTRAL NC TUESDAY-TUESDAY NIGHT. THE JET HELPING TO USHER THE S/W OFFSHORE COUPLED WITH THE CLOSED LOW TO OUR SW WILL INCREASE UPPER DIVERGENCE OVER CENTRAL NC. WITH A MOIST AIR MASS IN PLACE (PRECIP WATER VALUES 1.5-1.7 INCH RANGE) AND IMPROVING SUPPORT ALOFT...EXPECT SCATTERED TO NUMEROUS SHOWERS AND T-STORMS TO DEVELOP TUESDAY AFTERNOON AND CONTINUE WELL INTO TUESDAY EVENING. SEVERE PARAMETERS NOT ALL THAT ALARMING AS BULK SHEAR GENERALLY 20KTS OR LESS AND THE LOW LEVEL AIR MASS IS SLIGHTLY UNSTABLE. MAIN CONCERN WITH BE LOCALLY HEAVY DOWNPOURS TRAINING REPEATEDLY OVER THE SAME AREA WHICH MAY LEAD TO LOCALIZED NUISANCE FLOODING ISSUES. SINCE THERE IS THE POTENTIAL FOR HEATING ON MONDAY PRIOR TO CONVECTIVE INITIATION...HAVE ADJUSTED MAX TEMPS MONDAY UPWARD A COUPLE OF DEGREES FROM PREVIOUS FORECAST. MAX TEMPS TUESDAY HIGHLY DEPENDENT ON WHEN EARLY MORNING STRATUS BREAKS...ALLOWING FOR PARTIAL SUN BEFORE CONVECTION DEVELOPS. CURRENT FORECAST OF LOW-MID 80S APPEARS ON TARGET. OVERNIGHT MIN TEMPS GENERALLY IN THE MID- UPPER 60S.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 215 PM SATURDAY... A PATTERN CHANGE FROM THE RECENT WARM/DRY CONDITIONS IS ON THE WAY... AS THE WRN ATLANTIC RIDGE WILL FINALLY GIVE WAY TO A SOUTHWARD DIP IN THE WESTERLIES OVER THE CONUS. THIS WILL BRING IMPROVING CHANCES FOR MUCH-NEEDED RAINFALL BEGINNING EARLY IN THE WORK WEEK. THE VAST MAJORITY OF CENTRAL NC HAS SEEN VERY LITTLE RAIN IN THE LAST COUPLE OF WEEKS... 1 TO 2 INCHES BELOW NORMAL OR UNDER 50% OF NORMAL... IN THE LAST 14 DAYS ACCORDING TO WATER.WEATHER.GOV/PRECIP/. THE SURFACE FRONT SHOULD BE SITUATED ACROSS SRN PA DOWN THROUGH WRN WV AND ERN KY/TN EARLY MON AS THE MID LEVEL TROUGH EXTENDS FROM THE GREAT LAKES DOWN THROUGH THE LOWER MISS VALLEY. LEE TROUGHING WILL SHARPEN THROUGH THE PIEDMONT MON WITH INCREASING PW TO 150% OF NORMAL OR GREATER... LEADING TO RISING CHANCES FOR SHOWERS AND STORMS STARTING FIRST OVER THE WRN CWA BY EARLY AFTERNOON THEN DRIFTING EASTWARD. STEERING FLOW WILL BE QUITE WEAK WITH ONLY 10-15 KTS OF DEEP LAYER SHEAR... SO EXPECT A SLOW NE MOVEMENT TO THE CELLS. LARGE SCALE MODELS AND SREF PROBABILITIES SUGGEST SCATTERED SHOWERS/STORMS MAINLY ACROSS THE NRN/WRN CWA WITH ISOLATED CELLS IN THE SOUTHEAST ALONG THE INLAND-MOVING SEA BREEZE... SUPPORTING THE EXISTING FORECAST AND WILL LEAVE POPS LARGELY AS IS. SLIGHTLY ABOVE NORMAL THICKNESSES WITH PARTLY TO MOSTLY CLOUDY SKIES SHOULD LEAD TO HIGHS CLOSE TO NORMAL... MID-UPPER 80S AS THE THERMAL RIDGE EXTENDS THROUGH CENTRAL NC. MILD MON NIGHT WITH CONVECTIVE DEBRIS MID CLOUDS AND SOME STRATUS. CONVECTION COVERAGE WILL DWINDLE WITH LOSS OF HEATING BUT DEEPENING MOISTURE AND WEAK ELEVATED INSTABILITY NECESSITATES KEEPING IN AT LEAST ISOLATED COVERAGE MON NIGHT. HAVE UPPED MON NIGHT LOWS TO THE UPPER 60S-NEAR 70. THE MID LEVEL TROUGH WILL CONTINUE TO EASE EASTWARD TUE BUT WILL BECOME UNPHASED WITH THE FASTER NORTHERN PORTION CROSSING FAR SRN QUEBEC INTO THE NORTHEAST STATES WHILE THE SOUTHERN PORTION LAGS BACK OVER THE CENTRAL GULF STATES... POTENTIALLY CLOSING OFF. (THE ECMWF HAS TRENDED IN THIS DIRECTION BUT DEPARTS FROM THE NAM/GFS IN DIGGING THE NRN STREAM SEEMINGLY TOO MUCH OVER THE ERN LAKES/NORTHEAST STATES... WITH A TOO-FAST AND TOO-FAR SOUTHWARD FRONTAL MOVEMENT DOWN THROUGH THE MIDATLANTIC LATE TUE AND TUE NIGHT. FAVOR THE CONSISTENT SLOWER AND MORE-NORTHERN GFS. THIS WILL KEEP A LIGHT SSW STEERING FLOW OVER NC. ONCE THE MORNING STRATUS MIXES OUT... CONVECTION SHOULD BE SWIFT TO INITIATE WITH PLENTIFUL MOISTURE (PW 150-180% OF NORMAL)... INCLUDING WITHIN THE MIXED PHASE REGION ALOFT... AND MODERATE MUCAPE OF 1000-2000 J/KG. LIKELY MODE OF CONVECTION WILL BE MULTICELL CLUSTERS AND PULSE STORMS WITH DEEP LAYER SHEAR REMAINING MODEST AT JUST 15-25 KTS AND DEEP FAIRLY UNIDIRECTIONAL FLOW. EXPECT NUMEROUS SHOWERS/STORMS ALONG THE SURFACE TROUGH THROUGH THE PIEDMONT... AND THE SREF SHOWS THIS AS WELL WITH A 70-90% CHANCE OF MEASURABLE RAIN OVER THE ENTIRE AREA TUE AFTERNOON. WILL HAVE LIKELY POPS AREAWIDE... TRENDING DOWN SLIGHTLY AFTER NIGHTFALL BUT PERSISTING GIVEN LINGERING MARGINAL INSTABILITY. THE FRONT SHOULD DIP DOWN TO THE NC/VA LINE OVERNIGHT... PUSHING THE BEST COVERAGE TO THE S/E CWA... BUT DON`T EXPECT THE FAR-SOUTH PUSH OF THE ECMWF WHICH SUGGESTS LITTLE TO NO CHANCE IN THE NORTH OVERNIGHT. HIGHS TUE 82-87... WITH ABOVE NORMAL THICKNESSES ONCE AGAIN TEMPERED BY CLOUDS. LOWS TUE NIGHT MID-UPPER 60S. FORECAST CONFIDENCE SLIPS STARTING WED WITH INCREASING UNCERTAINTY AS TO WHETHER OR NOT A WEAK MID LEVEL LOW WILL CUT OFF... AND IF IT DOES... EXACTLY WHERE IT SETTLES. THE GFS/ECMWF WITH VARYING STRENGTH AND PLACEMENT KEEP IT TO OUR SSW OR SW... MEANDERING OVER THE SOUTHEAST OR GULF STATES... WITH WEAK MID LEVEL FLOW PERSISTING OVER NC. THE FRONT SHOULD DIP INTO THE NORTHEAST CWA WED... THEN WASH OUT GRADUALLY THE REST OF THE WEEK WHILE GIVING WAY TO AN INVERTED TROUGH JUST OFF THE SE COAST. PW IS LIKELY TO STAY ABOVE NORMAL WITH SOUPY LOW LEVEL AIR... GENERATING TYPICAL SCATTERED DAILY SHOWERS AND STORMS WED THROUGH SAT. THICKNESSES WILL RECOVER BACK TO ABOVE NORMAL VALUES BY FRI/SAT. EXPECT HIGHS IN THE LOW-MID 80S WED TO RISE GRADUALLY EACH DAY... REACHING THE UPPER 80S BY SAT. LOWS IN THE LOW-MID 60S WARMING TO THE UPPER 60S SAT MORNING. -GIH && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... AS OF 150 AM SUNDAY... 24-HR TAF PERIOD: VFR CONDITIONS ARE GENERALLY EXPECTED DURING THE 24 HOUR TAF PERIOD. HOWEVER... PATCHY SUB-VFR CIGS AND/OR VISBYS WILL AGAIN POSSIBLE THIS MORNING... WITH THE HIGHEST LIKELIHOOD OF OCCURRENCE AT KGSO/KINT. IN ADDITION... A FEW SHOWERS WILL BE POSSIBLE AT KGSO/KINT EARLY THIS MORNING NEAR DAYBREAK. ANY SUB-VFR CIGS SHOULD LIFT BY 16Z OR SO AND ANY VISBYS RESTRICTIONS SHOULD END SHORTLY AFTER DAYBREAK (OUTSIDE OF ANY PRECIP). ISOLATED TO WIDELY SCATTERED SHOWERS AND STORMS WILL AGAIN BE POSSIBLE THIS AFTERNOON... WITH THE HIGHEST PROBABILITIES OVER THE TRIAD REGION (KGSO/KINT). THUS... HAVE INCLUDED A PROB30 FOR STORMS AT KGSO/KINT DURING THE AFTERNOON/EARLY EVENING. ELSEWHERE... PROBABILITIES ARE TOO LOW TO INCLUDE ANY MENTION OF PRECIP IN THE TAFS. LOOKING AHEAD: CHANCES FOR EARLY MORNING STRATUS/FOG AND AFT/EVE CONVECTION WILL INCREASE AT ALL TERMINALS MON-WED AS A SLOW-MOVING UPPER LEVEL TROUGH APPROACHES THE CAROLINAS/MID-ATLANTIC FROM THE WEST. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BSD/BADGETT NEAR TERM...BSD SHORT TERM...WSS LONG TERM...HARTFIELD AVIATION...BSD/VINCENT

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