Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 251824 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 225 PM EDT WED MAR 25 2015 .SYNOPSIS...HIGH PRESSURE EXTENDING SOUTH OVER THE MID-ATLANTIC REGION WILL SHIFT OUT INTO THE ATLANTIC TODAY. THIS WILL ALLOW A WARM FRONT TO LIFT NORTH THROUGH THE STATE OVERNIGHT. A COLD FRONT WILL APPROACH SLOWLY FROM THE WEST ON THURSDAY AND WILL CROSS THE AREA THURSDAY NIGHT. && .NEAR TERM /TODAY AND TONIGHT/...
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AS OF 1050 AM WEDNESDAY... WEAK WARM AIR ADVECTION ATOP A COOL DRY NEAR SFC AIRMASS HAS RESULTED IN A FEW SPRINKLES THIS MORNING AS 500MB HEIGHTS HAVE ACTUALLY INCREASED OVER THE REGION IN RESPONSE TO AMPLIFYING SHORTWAVE TROUGH DROPPING SOUTHEAST OUT OF THE ROCKIES. HOWEVER BY THE AFTERNOON AS LOW-LEVEL DRY AIR RIDGE SHIFTS OUT TO SEA...925-850MB SELY MOIST LOW-LEVEL FEED ADVECTING INLAND OFF THE SOUTHEAST COAST WILL BECOME INCREASINGLY STRONGER LATE THIS AFTERNOON AND THROUGH THE OVERNIGHT HOURS...SUPPORTING INCREASING RAIN SHOWERS AND POSSIBLY SOME ELEVATED THUNDER AS WEAK INSTABILITY DEVELOPS(MUCAPE(400-600 J/KG)OWING TO STEEP MID-LVL LAPSE RATES AND 35+ KT WLY DEEP SHEAR. AS FAR AS SEVERE POTENTIAL... OUTSIDE OF LOW- LEVEL MOISTURE TRANSPORT/WAA ...FORCING FOR ASCENT WILL BE WEAK. AND THUS WILL LIMIT SEVERE POTENTIAL. BUT GIVEN FAVORABLE EFFECTIVE SHEAR OF 35KTS...WOULD NOT BE SURPRISE IF A STORM OR TWO ACROSS EASTERN/COASTAL PORTIONS EXHIBITS WEAK ROTATION. TEMPERATURES WILL BE ONE OF THE MOST CHALLENGING ASPECTS OF THIS FORECAST. PIREP REPORTS ACROSS THE AREA INDICATE LOW-CLOUD DECK IS ONLY 300-1000FT THICK...THICKEST ACROSS THE WESTERN PIEDMONT WHERE BETTER WARM MOIST LOW-LEVEL AND THINNEST IN THE EAST IN CLOSE PROXIMITY TO THE LINGERING LOW-LEVEL DRY AIR RIDGE WHERE SKIES ARE CLEAR/SUNNY. SO THE BIGGEST POTENTIAL FOR A FORECAST BUST WRT TO TEMPERATURES WILL BE ACROSS THE EAST/CENTRAL PORTIONS OF THE FORECAST AREA WHERE JUST A HOUR OR TWO OF SUN/PARTIAL SUN COULD ALLOW TEMPERATURES TO JUMP UP CONSIDERABLY. ADDITIONALLY COULD SEE A LATE RISE IN TEMPERATURES ACROSS THE SOUTH-SOUTHEAST...GIVEN EXPECTED TIMING OF SFC WARM FRONT NORTHWARD INTO THE AREA. CONFIDENCE IS A LITTLE HIGHER IN THE WEST WHERE LOW CLOUDS WILL LIKELY HOLD ON THROUGH DIURNAL HEATING KEEPING THE CAD WEDGE IN PLACE. HIGHS RANGING FROM LOWER 50S NW TO LOWER 70S SE. EXPECT NEAR STEADY TEMPS IN THE TRIAD OVERNIGHT... PERHAPS RISING A FEW DEGREES BY SUNRISE. ELSEWHERE...EXPECT TEMPS TO REMAIN NEARLY STEADY IN THE UPPER 50S WEST OF HWY 1 TO LOWER/MID 60S EAST AND ESP SE OF HWY 1.
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&& .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 445 AM WEDNESDAY... EXPECT THE CAD WEDGE TO ERODE THU MORNING TO EARLY THU AFTERNOON AS A SFC LOW TRACKS NE THROUGH THE OH VALLEY INTO THE MID-ATLANTIC... ESTABLISHING A WARM SECTOR OVER MOST (IF NOT ALL) OF CENTRAL NC. WITH THE STRONGEST WARM ADVECTION ALREADY NORTH OF THE REGION AND UNIDIRECTIONAL /SW/ FLOW ALOFT...FORCING FOR ASCENT WILL BE ON THE WEAK SIDE OF THE SPECTRUM THROUGH EARLY/MID AFTERNOON... UNTIL THE LOW-LEVEL TROUGH PROGRESSES EAST OF THE MOUNTAINS AND THE SFC COLD FRONT APPROACH FROM THE WEST LATE THU AFT/EVE INTO THU NIGHT. EXPECT A LOW CHANCE FOR PRECIP THROUGH 18Z THU ASIDE FROM LINGERING DRIZZLE PRIOR TO WEDGE EROSION...FOLLOWED BY AN INCREASING POTENTIAL FOR SHOWERS FROM WEST-EAST LATE THU AFTERNOON INTO THU NIGHT AS THE FRONT PROGRESSES INTO THE FOOTHILLS AND WESTERN PIEDMONT. OUTSIDE OF THE WESTERN PIEDMONT...THUNDER APPEARS QUESTIONABLE GIVEN UNFAVORABLE DIURNAL TIMING AND DPVA ATTENDANT THE AMPLIFYING UPPER LEVEL TROUGH PROGGED TO LAG BEHIND THE COLD FRONT /WARM SECTOR/. EXPECT HIGHS IN THE MID/UPPER 70S...EXCEPT PERHAPS IN THE NW PIEDMONT WHERE LOWER 70S APPEAR MORE LIKELY. LOWS THU NIGHT WILL DEPEND ENTIRELY ON THE PROGRESS OF THE COLD FRONT...WITH TEMPS REMAINING IN THE LOWER/MID 60S IN ADVANCE OF THE FRONT. AT THIS TIME WILL INDICATE TEMPS FALLING INTO THE 40S IN THE TRIAD BY SUNRISE FRI...BUT REMAINING STEADY ELSEWHERE. -VINCENT && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... AS OF 330 AM WEDNESDAY... STRONG COLD FRONT WILL BE OFFSHORE OR MOVING OFFSHORE BY FRIDAY MORNING AND STRONG COLD AIR ADVECTION WILL BE UNDERWAY TO OFFSET THE POTENTIAL FOR LIMITED INSOLATION. LINGERING ANAFRONTAL SHOWERS DRIVEN BY THE COLD AIR ADVECTION WILL LINGER IN THE EAST THROUGH MID DAY. THESE WILL BE FOLLOWED DURING THE AFTERNOON INTO EARLY EVENING BY ADDITIONAL LIGHT SHOWERS WHICH WILL BE FORCED BY A TRAILING MID LEVEL SHORT WAVE WHICH WILL HAVE SUFFICIENT LINGERING MOISTURE IN THE LOW LEVELS ABOVE THE MIXING LEVEL TO PRODUCE SCATTERED SHALLOW CONVECTION. HIGHS WILL BE IN THE MID 50S WEST TO UPPER 50S EAST. LINGERING CLOUD COVERAGE AND OVERNIGHT MIXING WILL FORTUNATELY AID IN SOFTENING THE TEMPERATURE CRASH FRIDAY NIGHT AS LOW LEVEL THICKNESSES FALL NEARLY 100 METERS (25-30 DEGREES BY RULE OF THUMB) IN THE 24 HOUR PERIOD FROM FRIDAY MORNING TO SATURDAY MORNING. GUIDANCE HAS BEEN CONSISTENTLY INDICATING MID TO UPPER 30S...AND WILL CONTINUE THIS TREND WITH A WARY EYE ON THE POSSIBILITY THAT CLEARER/CALMER CONDITIONS MIGHT ALLOW US TO RADIATE LOWER. THE UPPER TROF AXIS IS OVER THE AREA ON SATURDAY AND HIGHS WILL STALL IN THE UPPER 40S ACROSS THE NORTHERN TIER TO LOWER 50S ELSEWHERE AS THE COLD AIR ADVECTION OFFSETS INCREASED SUNSHINE AS SURFACE HIGH PRESSURE MIGRATES EAST INTO THE MID ATLANTIC. AS THE HIGH BUILDS IN...RADIATIONAL CONDITIONS WILL BE NEAR IDEAL ON SATURDAY NIGHT AND SUNDAY MORNINGS DAWN MINS WILL BE IN THE UPPER 20S NORTH TO NEAR FREEZING IN THE SOUTH. WE WILL BEGIN TO SEE MODIFICATION OF THE AIRMASS SUNDAY UNDER STRONG SUN AND NEUTRAL TEMPERATURE ADVECTION...AND HIGHS WILL BE MOSTLY IN THE MID 50S. WE HAVE LOW LEVEL RETURN FLOW AND SLOWLY RISING H5 HEIGHTS SUNDAY NIGHT INTO MONDAY TO INITIATE A MODERATING TREND IN THE TEMPS. A FAST MOVING SHORT WAVE AND ASSOCIATED FRONT WILL DIVE SOUTHEAST AND ACROSS THE AREA ON MONDAY...AND WHILE WE COULD SEE SOME SHOWERS SQUEEZED OUT BY THIS SYSTEM...THEY WOULD BE LIGHT AS ITS LIMITED AVAILABLE MOISTURE WILL BE PRECIPITATED OUT AS IT MOVES ACROSS THE MOUNTAINS. WILL MAINTAIN A DRY FORECAST FOR NOW WITH HIGHS MONDAY AND TUESDAY REACHING THE 60S AFTER MORNING LOWS FROM 40 TO 45. WEDNESDAY IS LOWER CONFIDENCE...BUT LOOKS TO BE DRY WITH HIGHS REACHING THE LOWER 70S. && .AVIATION /18Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 215 PM WEDNESDAY... 24-HR TAF PERIOD: AMIDST WEAK LOW-LEVEL WARM ADVECTION ATOP A SHALLOW COOL DRY SFC AIRMASS...KINT AND KGSO WILL MAINTAIN MVFR CEILINGS WITH A SLIGHT CHANCE OF LIGHT RAIN OR DRIZZLE THROUGH THE AFTERNOON. AT RWI/FAY...CEILINGS HAVE LIFTED TO VFR 5000-9000 FT AGL) AND SHOULD REMAIN THROUGH THE REMAINDER OF THE AFTERNOON. SADDLED IN BETWEEN...RDU WILL BE ON THE THRESHOLD OF HIGH-END MVFR/LOW END VFR WITH CEILINGS GENERALLY 2500-3500 KFT. CONDITIONS ARE EXPECTED TO DETERIORATE LATE THIS EVENING AND INTO THE OVERNIGHT HOURS AS STRONG WARM MOIST AIR ADVECTION WITHIN A A STRENGTHENING 35-40KT 925MB LOW-LEVEL JET OVERSPREADS THE AREA OVERNIGHT. EXPECT CEILINGS TO LOWER TO IFR AND PERHAPS LIFR OVERNIGHT WITH SCATTERED TO NUMEROUS SHOWERS AND POSSIBLY A THUNDERSTORM OR TWO POSSIBLE. ADDITIONALLY...AS THE LOW-LEVEL JET LIFTS ACROSS THE AREA...KINT AND KGSO MAY EXPERIENCE LLWS BETWEEN 03 TO 12Z AS CAD WEDGE MAY HOLD IN PLACE. WILL NOT INCLUDE ANY LLWS AT THIS TIME...BUT LLWS MAY BE ADDED WITH THE EVENING(00Z)PACKAGE. CEILINGS ARE EXPECTED TO IMPROVE TO VFR DURING THE DAY ON THURSDAY AS AS A WARM SECTOR BECOMES MORE FIRMLY ESTABLISHED AND DRIER AIR MOVES INTO THE AREA FROM THE SOUTHWEST. BREEZY SWLY WINDS OF 20 TO 25KTS ARE ALSO EXPECTED THURSDAY AFTERNOON. LOOKING AHEAD: A COLD FRONT WILL CROSS THE AREA THURSDAY NIGHT. SCATTERED SHOWERS ARE POSSIBLE AHEAD OF THE FRONT...BUT PRECIP WILL BE MOSTLY ANA-FRONTAL WITH CATEGORICAL RAIN CHANCES AND MVFR/IFR CEILINGS RETURNING EARLY FRI MORNING...PERSISTING THROUGH THE DAY AT EASTERN TERMINALS. THE RETURN OF VFR CONDITIONS LATE FRIDAY AFTERNOON/EVENING COULD BE TEMPORARILY DELAYED UNTIL THE PASSAGE OF THE STRONG UPPER LEVEL TROUGH SATURDAY MORNING.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...CBL NEAR TERM...CBL SHORT TERM...VINCENT LONG TERM...MLM AVIATION...CBL

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