Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 041814 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 215 PM EDT MON MAY 4 2015 .SYNOPSIS...
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HIGH PRESSURE OFF THE MID ATLANTIC COAST WILL EXTEND INTO THE REGION THROUGH MID WEEK. AN AREA OF LOW PRESSURE WILL FORM NEAR THE BAHAMAS DURING THE MIDDLE OF THE WEEK AND MOVE SLOWLY NORTH TOWARD THE SOUTHEAST COAST.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... AS OF 1000 AM MONDAY... A WEAK DISTURBANCE ALOFT INITIATED SOME PATCHY MID CLOUDS OVERNIGHT THAT HAVE DRIFTED EAST OVER THE COASTAL PLAIN THIS MORNING. SURFACE/850MB HIGH CENTERED JUST OFF THE NC COAST EXTENDS SOUTHWEST ACROSS SC THIS MORNING...LIMITING MOISTURE RETURN ACROSS NC...THOUGH PW HAS CREPT UP TO AROUND 0.75" PER 12Z KGSO RAOB. DEEP MIXING TODAY AROUND 6500 FT...AND WARMING ALOFT WILL KEEP MOST OF CENTRAL NC WELL-CAPPED. MOST CAMS SHOW CONVECTIVE INITIATION IN THE HIGHER TERRAIN BY 18Z...DRIFTING SLOWLY EAST IN WEAK WESTERN STEERING FLOW. ITS STILL VERY QUESTIONABLE WHETHER ANY SHOWERS WILL REACH THE WESTERN PIEDMONT BEFORE DRYING OFF AS THEY ENCOUNTER THE MORE HOSTILE ENVIRONMENT IN THE PIEDMONT. AS SUCH...WILL FOCUS ONLY A VERY SLIGHT CHANCE MAINLY FROM FORSYTH DOWN INTO DAVIDSON COUNTY AFTER 20Z. THE 12Z KGSO THICKNESS (1000-850MB) VERIFIED 11M WARMER THAN SUNDAY...SO FORECAST HIGHS 2-3 DEGREES WARMER THAN SUNDAY LOOK GOOD...79-83 NO OTHER CHANGES. && .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/... AS OF 315 AM MONDAY... GENERALLY FAIR WEATHER IS EXPECTED THROUGH THE PERIOD AS SURFACE HIGH PRESSURE EXTENDS INTO THE AREA FROM THE ATLANTIC AND WEAK RIDGING DEVELOPS OVER THE REGION. THE MAIN FORECAST PROBLEM IS ASSOCIATED WITH THE SCATTERED DIURNAL CONVECTION THAT WILL LIKELY DEVELOP ACROSS THE MOUNTAINS AGAIN ON TUESDAY AFTERNOON. WHILE THE MIXED LAYER TUESDAY AFTERNOON IS NOT AS DEEP AS TODAY AND BOUNDARY LAYER MOISTURE INCREASES SLIGHTLY...STILL BELIEVE THE POTENTIAL FOR MOUNTAIN CONVECTION REACHING CENTRAL NC IS LIMITED. THE FLOW THROUGH THE CLOUD DEPTH IS WEAKER AND MORE NORTHERLY SUGGESTING CONVECTION MAY HAVE A HARD TIME PUSHING EAST AND IN FACT MAIN DRIFT SOUTH OR REMAIN ANCHORED TO THE TERRAIN. WITH THIS IN MIND WILL OMIT POPS FOR OUR WESTERN ZONES FOR TUESDAY AFTERNOON. EXPECT MAINLY CLEAR SKIES MONDAY NIGHT WITH PARTLY CLOUDY SKIES ON TUESDAY. MAINLY CLEAR SKIES ARE EXPECTED AGAIN TUESDAY NIGHT ALTHOUGH THE NAM AND A FEW SREF MEMBERS SUGGEST SOME SHALLOW STRATUS MAY APPROACH THE SANDHILLS AND SOUTHERN COASTAL PLAIN TOWARD DAYBREAK WEDNESDAY. LOWS ON TUESDAY MORNING WILL RANGE IN THE LOWER TO MID 50S WITH HIGHS AGAIN IN THE 79-84 RANGE. LOWS TUESDAY NIGHT WILL RANGE IN THE MID TO UPPER 50S. -BLAES && .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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AS OF 215 PM MONDAY... LIKELY LOW PRESSURE DEVELOPMENT OVER THE NRN BAHAMAS DOMINATES THE MEDIUM RANGE FORECAST. WHILE SUCH DEVELOPMENT -- AND A GENERAL DRIFT TO THE NORTH OR NNW -- IS FAIRLY CERTAIN AT THIS POINT... ITS EXACT MOVEMENT... STRENGTH... AND POTENTIAL FOR TROPICAL CHARACTERISTICS REMAINS IN QUESTION. OVERVIEW: A BACKDOOR FRONT IS EXPECTED TO DROP SOUTHWARD TOWARD OUR NRN BORDER BY WED MORNING... BUT LATEST GUIDANCE HOLDS THIS FRONT (AND THE COOLER AIR BEHIND IT) JUST TO OUR NORTH... KEEPING US UNDER THE INFLUENCE OF STACKED FLAT W-E ORIENTED RIDGING THROUGH THE LOW AND MID LEVELS ACROSS NC EARLY WED. SUBTLE NEGATIVELY TILTED TROUGHING ANALYZED OVER THE NE GULF THIS MORNING IS EXPECTED TO TRACK SLOWLY ENE ACROSS FL BEFORE EMERGING OFF THE ERN FL COAST. THE NAM INTENSIFIES THE ASSOCIATED SURFACE LOW MUCH MORE QUICKLY OVER THE NRN BAHAMAS THAN THE GFS/ECMWF... AND THE NAM REMAINS THE STRONGEST AS IT DRIFTS TO THE NORTH WED... WITH THE ECMWF THE WEAKEST (MERELY AN INVERTED TROUGH WED). BY THU EVENING THE NAM/GFS PLACE THE LOW JUST OFF HILTON HEAD SC... AND WHILE THE 00Z OP ECMWF IS A BIT SOUTHEAST OF THIS POSITION... THE ECMWF ENSEMBLE MEAN IS FAIRLY CLOSE TO THE NAM/GFS POSITION. THE GOOD NAM/GFS AGREEMENT LENDS A BIT MORE CONFIDENCE IN THE GFS SOLUTION... WHICH CULMINATES IN THE LOW TRACKING NORTHWESTWARD INTO SC THU NIGHT BEFORE BECOMING STATIONARY (OR MEANDERING) AND WEAKENING JUST INLAND OVER THE SOUTHEAST STATES OVER THE WEEKEND... A FUNCTION OF THE STEERING FLOW AROUND A STRONG WRN ATLANTIC ANTICYCLONE... ALL BENEATH STRONG MEAN EAST COAST MID LEVEL RIDGING. THE OP ECMWF ON THE OTHER HAND HOLDS THE LOW OFFSHORE WITH A MORE NORTHEASTWARD DRIFT AND ACCORDINGLY REMAINS STRONGER THROUGH SAT. WPC AND HPC EXPERTS ARE FAVORING A MORE WESTWARD POSITION AS COMPARED TO EARLIER FORECASTS... A COMPROMISE SOLUTION BETWEEN THE WESTERNMOST GFS AND EASTERNMOST ECMWF WITH A SLIGHT LEAN TOWARD THE GFS... AND AT A SPEED SLIGHTLY SLOWER THAN THE GFS. WHETHER THIS LOW ATTAINS ANY TROPICAL CHARACTERISTICS IS DIFFICULT TO DETERMINE AT THIS TIME... AND ANY SPECULATION WOULD BE JUST THAT... BUT AT LEAST SUBTROPICAL DEVELOPMENT IS NOT OUT OF THE QUESTION GIVEN THAT WATER TEMPS JUST NORTH OF THE BAHAMAS ARE NEAR 80 AND ABOVE CLIMATOLOGY. LATE IN THE WEEK... TROUGHING THAT IS NOW JUST OFF THE PACIFIC NW... AND WHICH WILL STRENGTHEN INTO A CLOSED LOW NEAR VEGAS BY FRI... WILL THEN OPEN UP AND KICK EAST-NORTHEASTWARD THROUGH THE CENTRAL CONUS... HELPING TO DISSIPATE AND PUSH EASTWARD ANY REMNANT LOW OVER THE SOUTHEAST STATES. SENSIBLE WEATHER: WED LOOKS DRY FOR MOST... ALTHOUGH IN THIS WEAK FLOW REGIME... CONVECTION RESULTING FROM DIFFERENTIAL HEATING OVER THE HIGHER TERRAIN AS WELL AS ALONG THE BACKDOOR FRONT TO OUR NORTH MAY DRIFT INTO NRN AND NW SECTIONS LATE IN THE DAY. WILL KEEP LOW CHANCE POPS WED IN THESE AREAS LATE AFTERNOON INTO EARLY EVENING. BY THU AFTERNOON... FOLLOWING THE ABOVE-DISCUSSED TIMING/TRACK... WE SHOULD START SEEING BANDS OF SHOWERS WORKING INTO THE SE CWA... WITH CONVECTION STILL LIKELY FIRING OVER THE HIGHER TERRAIN JUST TO OUR NW. WILL FOCUS CHANCE POPS ON THE SE AND IN THE FAR NW THU. UNCERTAINTY GROWS EXPONENTIALLY BY FRI... BUT WITH A DECENT CHANCE OF A WEAKER BUT STACKED LOW SOMEWHERE OVER THE INTERIOR SOUTHEAST JUST INLAND... WILL LEAN TOWARD CLIMATOLOGICAL SHOWER/STORM CHANCES... HIGHER SOUTH AND SE... FOR FRI AND HEADING INTO THE WEEKEND. IF THE ECMWF IS CORRECT... WE WOULD SEE LOWER CONVECTION COVERAGE WITH STRONGER RIDGING IN PLACE OVER THE SRN APPALACHIANS. RAIN CHANCES SHOULD DIMINISH ONCE AGAIN SUN INTO MON WITH THE LIKELY WEAKENING AND DEPARTURE OF ANY REMNANT LOW OVER OUR REGION... IN RESPONSE TO THE APPROACHING TROUGH FROM THE WEST. TEMPERATURES: LOW LEVEL THICKNESSES ARE EXPECTED TO BE SLIGHTLY ABOVE NORMAL WED AND CONTINUE TO RISE A COUPLE OF METERS EACH DAY THROUGH MON. SHOULD SEE HIGHS WED AROUND 80 AND LOWS WED NIGHT AROUND 60. WITH EXPECTATIONS OF AT LEAST SOME CLOUD COVER AND POSSIBLE SHOWERS THU ONWARD... WILL KEEP HIGHS NEAR TO SLIGHTLY ABOVE NORMAL... TRENDING BACK TO AT LEAST A CATEGORY ABOVE NORMAL SUN/MON AS WE SHOULD HAVE DECREASING CLOUDS AND CONVECTION COVERAGE. ABOVE NORMAL LOWS THROUGH THE PERIOD. -GIH
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/... AS OF 140 PM MONDAY... HIGH CONFIDENCE VFR CONDITIONS THROUGH THE 24 HOUR TAF PERIOD AS HIGH PRESSURE CENTERED OFFSHORE EXTENDS INTO OUR REGION THROUGH TUESDAY. SCATTERED SHOWERS ARE EXPECTED TO FORM (AND SOME ARE ALREADY FORMING) ALONG THE MOUNTAINS TODAY...A FEW OF WHICH MAY DRIFT EAST TOWARD THE TRIAD LATE THIS AFTERNOON. CONDITIONS ARE VERY FAVORABLE FOR THE SHOWERS TO VERY FAR TO THE EAST...BUT SOME HI- RES MODELS SHOW A COUPLE SHOWERS NEAR KINT AFTER 20Z. EVEN SO...THE IMPACTS WILL BE SMALL IF ANY AT ALL...SO HAVE JUST INCLUDED A VFR TEMPO AT KINT FOR THIS TAF PACKAGE. CLEARING SKIES AND A LIGHT SOUTHWESTERLY WIND ARE EXPECTED TONIGHT THROUGH 18Z ON TUESDAY. OUTLOOK...VFR CONDITIONS ARE EXPECTED TUESDAY AND WEDNESDAY AHEAD OF A FRONT THAT WILL DROP SOUTH INTO VIRGINIA BY WEDNESDAY...THEN LIKELY REMAIN NORTH OF THE AREA AS A COASTAL LOW BEGINS TO TAKE SHAPE OFF THE SOUTHEAST COAST LATE IN THE WEEK. MOISTURE IS EXPECTED TO INCREASE EACH DAY ALONG WITH THE THREAT OF EARLY MORNING STRATUS/FOG. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BLAES NEAR TERM...BLAES/22 SHORT TERM...BLAES LONG TERM...HARTFIELD AVIATION...22

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