Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 261925 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 325 PM EDT SUN APR 26 2015 .SYNOPSIS...A WEAK AREA OF HIGH PRESSURE WILL BUILD INTO CENTRAL NC TONIGHT AND MONDAY...AND SETTLE OVERHEAD MONDAY NIGHT INTO TUESDAY. AN AREA OF LOW PRESSURE WILL BEGIN TO AFFECT OUR REGION TUESDAY NIGHT AND WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 245 PM SUNDAY... MAIN FORECAST CHALLENGE IN THE NEAR TERM CENTERS ON WHEN SKIES ARE EXPECTED TO CLEAR. VISIBLE IMAGERY DOES SHOW A SOUTHWARD DRIFT TO THE CLEARING-OUT OF THE LOW CLOUDS OVER CENTRAL-SOUTHEAST VA EARLY THIS AFTERNOON. THIS SURGE OF DRIER AIR IS OCCURRING IN THE WAKE OF THE PASSAGE OF THE 850MB TROUGH. THIS FEATURE CURRENTLY DRIFTING SOUTH OVER CENTRAL NC (IN VICINITY OF HIGHWAY 64). MODEL GUIDANCE SUGGEST LOW CLOUDS DEPARTING NORTH-SOUTH BETWEEN 21Z-02Z. WILL LEAN FORECAST IN THIS DIRECTION. HOWEVER...POTENTIAL FOR THE OVERCAST/BROKEN SKIES TO PERSIST A BIT LONGER THAN FORECAST AS LOSS OF INSOLATION MAY SLOW CLOUD EROSION PROCESS. OTHERWISE MAY SEE A FEW PATCHES OF RAIN WITH THE PASSAGE OF THE 850MB TROUGH OVER THE SOUTHERN COUNTIES LATE THIS AFTERNOON-EARLY EVENING. COVERAGE EXPECTED TO BE ISOLATED AND OBSERVED AMOUNTS WILL TOTAL NO MORE THAN A TRACE OR A HUNDREDTH. A LIGHT NLY WIND THIS EVENING WILL SUBSIDE TO NEAR CALM OVERNIGHT. IF PARTIAL CLEARING OCCURS...POTENTIAL FOR POCKETS OF FOG TO DEVELOP. MIN TEMPS LOW-MID 40S. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... AS OF 245 PM SUNDAY... MONDAY...A MINOR S/W WILL CROSS THE NORTHERN MID ATLANTIC MONDAY...BRUSHING NE NC IN THE LATE AFTERNOON. THIS FEATURE WILL LIKELY ENHANCE STRATOCU COVERAGE OVER THE NORTHERN COASTAL PLAIN WITH AN ISOLATED PATCH OF LIGHT RAIN POSSIBLE. ELSEWHERE THE SUN WILL MAKE AN APPEARANCE. A STEADY NW LOW LEVEL FLOW WILL AID TO DIMINISH ANY LINGERING LOW CLOUD COVER OVER THE REST OF THE PIEDMONT AND SANDHILLS. TEMPERATURES WILL RECOVER NICELY IN THIS DOWNSLOPE WIND REGIME. AFTERNOON TEMPS WILL VARY FROM THE MID-UPPER 60S IN THE PIEDMONT/NORTHERN COASTAL PLAIN TO AROUND 70 IN THE SE. MONDAY NIGHT...NOSE OF SFC RIDGE WILL EXTEND ACROSS THE REGION. DRY AIR UNDERNEATH THIS RIDGE WILL RESULT IN MOSTLY CLEAR SKIES. MIN TEMPS WILL BE CHILLY..DIPPING INTO THE UPPER 30S AND LOWER 40S. AT THIS TIME...NOT EXPECTING TEMPS TO DIP BELOW 37 DEGREES. THUS PATCHY LIGHT FROST NOT A CONCERN...BUT WILL CONTINUE TO MONITOR. && .LONG TERM /TUESDAY THROUGH SUNDAY/...
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AS OF 320 PM SUNDAY... TUESDAY AND TUESDAY NIGHT: BRIEF S/W RIDGING WILL BUILD OVER THE AREA ON TUESDAY... WITH A SURFACE RIDGE AXIS INITIALLY EXTENDING INTO THE AREA FROM THE NORTHWEST (BEFORE A PIECE OF THE HIGH BREAKS OFF OVER THE CAROLINAS). THIS SHOULD ALLOW FOR MOSTLY SUNNY TO PARTLY SUNNY SKIES... WITH LOW LEVEL THICKNESS VALUES STILL RUNNING AT LEAST SOME 20-25 METERS BELOW NORMAL. GIVEN THIS EXPECT WE SHOULD SEE HIGH TEMPS GENERALLY IN THE 60S... WITH PERHAPS A FEW LOCATIONS TOUCHING 70 ACROSS THE SOUTH/SOUTHEAST. CLOUD COVER WILL QUICKLY THICKEN ON TUESDAY NIGHT/EARLY WEDNESDAY MORNING IN ADVANCE OF A SOUTHERN STREAM SYSTEM... WITH POSSIBLY SOME RAIN SPREADING INTO THE SOUTHWESTERN/WESTERN PORTIONS OF THE AREA NEAR DAYBREAK WEDNESDAY PER THE GFS AND ECMWF. THE LATEST NAM (12Z/26TH) HAS PRECIP SPREADING INTO SOUTHERN PORTIONS OF THE AREA BY MID TO LATE TUESDAY EVENING EVEN. GIVEN THIS SEEMS TO BE A FAST OUTLIER WILL CONTINUE TO TREND TOWARDS A BLEND OF THE GFS/ECMWF FOR THIS PERIOD OF THE FORECAST. WRT LOW TEMPS... WILL SHOW A RANGE FROM THE MID 40S NE (WHERE WE WILL HAVE THE BEST NOCTURNAL COOLING) TO AROUND 50 SW. HOWEVER... WITH A DRIER SURFACE AIRMASS IN PLACE WE SHOULD SEE TEMPS BEGIN TO WETBULB WITH THE ARRIVAL OF THE PRECIP. THUS... TEMPS MAY FALL AFTER SUNSET SOME IN THE SW FROM THE LOSS OF DAYTIME HEATING... THEN STABILIZE BY MID TO LATE EVENING WITH THE INCREASING/THICKENING CLOUD COVER... BEFORE ONCE AGAIN FALLING WITH AS THE RAIN ARRIVES. THUS... LOW TEMPS ARE TRICKY FOR WEDNESDAY MORNING AND WILL BE DEPENDENT ON THE TIMING AND INTENSITY OF THE RAIN FOR LOCATIONS THAT DO INDEED SEE PRECIP MOVE INTO THE AREA DURING THE EARLY MORNING HOURS OF WEDNESDAY. WEDNESDAY THROUGH FRIDAY NIGHT: MEDIUM RANGE MODELS ARE IN BETTER AGREEMENT TODAY IN SHOWING A SOUTHERN STREAM MID LEVEL LOW OVER NORTHERN TX TO BEGIN THE WEEK TRANSLATING EASTWARD AND SPAWNING A SURFACE LOW NEAR THE GULF COAST... THEN TRACKING TOWARDS OUR REGION TUESDAY NIGHT INTO WEDNESDAY... WITH THE EXPECTED SURFACE LOW TRACKING EASTWARD-NORTHEASTWARD AND EVENTUALLY NORTHEASTWARD ALONG OUR COAST BY THURSDAY MORNING. GIVEN THE RATHER DRY AIRMASS PRECEDING THIS SYSTEM... EXPECT WE SHOULD SEE A CAD AIRMASS DEVELOP ACROSS CENTRAL NC ON WEDNESDAY AS RAIN OVERSPREADS THE REGION FROM SOUTHWEST TO NORTHEAST (POSSIBLY BEGINNING DURING THE EARLY MORNING HOURS OF WEDNESDAY (AGAIN... WE STAYED CLOSE TO GFS/ECMWF FOR TIMING). THE CAD AIRMASS IS EXPECTED TO LINGER ACROSS PORTIONS OF CENTRAL NC ON THURSDAY (WITH BELOW NORMAL TEMPS EVEN EXPECTED FOR LOCATIONS THAT EVEN SEE SOME BREAKS IN THE CLOUDS STILL)... BEFORE SLOWLY ERODING ON THURSDAY NIGHT INTO FRIDAY AS THE SURFACE LOW LIFTS OFF TO THE NORTHEAST... YIELDING MORE OF A NORTH TO NORTHWESTERLY LOW TO MID LEVEL FLOW. CHANCES FOR RAIN SHOULD BEGIN TO DECREASE BY LATE THURSDAY INTO THURSDAY EVENING... WITH GENERALLY DRY WEATHER AGAIN EXPECTED BY FRIDAY. HIGH TEMPS ON WEDNESDAY ARE EXPECTED TO BE WELL BELOW NORMAL WITH THE EXPECTED CAD DEVELOPMENT. FOR NOW HAVE LOWERED HIGHS INTO THE MID TO UPPER 50S NW TO THE MID 60S FAR NE FOR WEDNESDAY. HIGHS THURSDAY AND FRIDAY IN THE 60S TO NEAR 70 ON FRIDAY IN THE SOUTH... STILL BELOW NORMAL. LOWS ARE EXPECTED TO BE IN THE UPPER 40S TO LOWER 50S FOR THE PERIOD. SATURDAY THROUGH SUNDAY: MID LEVEL HEIGHTS ARE EXPECTED TO RISE NEXT WEEKEND. THIS COUPLED WITH HIGH PRESSURE AT THE SURFACE WILL ALLOW FOR A WARMING A DRYING TREND IN CENTRAL NC. THIS SHOULD RESULT IN HIGHS IN THE 70S AND LOWS IN THE 50S... NEAR NORMAL FOR THIS TIME OF YEAR... WITH POSSIBLY EVEN ABOVE NORMAL HIGHS FOR SUNDAY AFTERNOON (MAYBE SOME LOW 80S).
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/... AS OF 125 PM SUNDAY... HIGH LIKELIHOOD THAT MVFR CONDITIONS WILL PERSIST THROUGH 21Z ACROSS CENTRAL NC. AFTER 21Z...NLY FLOW WILL BEGIN TO INFILTRATE A DRIER AIR MASS INTO THE LOWEST 5K FEET OF THE ATMOSPHERE WHICH SHOULD AID TO DIMINISH THE LOW STRATUS. THIS SHOULD LEAD TO VFR CONDITIONS ACROSS CENTRAL NC THIS EVENING. AFTER 03Z...WILL LIKELY SEE POCKETS OF IFR/LIFR FOG DEVELOP WHICH MAY AFFECT MOST IF NOT ALL TERMINALS AFTER 06Z. THE PATCHY OR AREAS OF FOG SHOULD LIFT/DISSIPATE BY 12Z. VFR CONDITIONS ANTICIPATED MONDAY INTO TUESDAY AS AN AREA OF HIGH PRESSURE WILL DOMINATE OUR WEATHER PATTERN. ASIDE FROM A BRIEF PERIOD OF MVFR FOG TUESDAY MORNING...VFR CONDITIONS SHOULD RULE. AN APPROACHING LOW PRESSURE SYSTEM WILL BRING A CHANCE OF SUB VFR CONDITIONS TO CENTRAL NC WEDNESDAY INTO THURSDAY. IMPROVING AVIATION CONDITIONS ARE ANTICIPATED THURSDAY NIGHT INTO FRIDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...BSD AVIATION...WSS

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