Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 041202 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 802 AM EDT TUE AUG 4 2015 .SYNOPSIS...
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AN AREA OF LOW PRESSURE WILL TRACK FROM THE CENTRAL SC COAST THIS MORNING TO NEAR THE OUTER BANKS OF NC BY TONIGHT. MEANWHILE...A COLD FRONT WILL APPROACH FROM THE NORTHWEST AND SETTLE INTO CENTRAL NC WEDNESDAY INTO WEDNESDAY NIGHT.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 335 AM TUESDAY... A 1011 MB SURFACE LOW CENTERED JUST SOUTH OF KCHS IS FORECAST TO TRACK NORTHEASTWARD GENERALLY ALONG THE COAST OF THE CAROLINAS THROUGH TONIGHT. DEEP CONVECTION HAS BLOSSOMED DURING THE PAST COUPLE OF HOURS IN ASSOCIATION WITH THE LOW...AND EXTRAPOLATION OF THIS ACTIVITY (AND THE TRACK OF THE SURFACE LOW) SUGGESTS IT SHOULD REMAIN CONFINED FROM SAMPSON AND WAYNE COUNTIES AND ESPECIALLY POINTS EASTWARD...IN AXIS OF FOCUSED 925-850 MB MOISTURE TRANSPORT TO THE EAST OF AN INVERTED TROUGH AXIS FROM THE LOW CENTER. OTHERWISE...A PIEDMONT TROUGH WILL SHARPEN THIS AFTERNOON...AHEAD OF A COLD FRONT THAT WAS ANALYZED THIS MORNING FROM THE LOWER GREAT LAKES TO THE LOWER OH VALLEY. THE MODELS INDICATE THE COLD FRONT WILL SETTLE SOUTH ACROSS VA TONIGHT...TO NEAR THE NC BORDER BY WED MORNING. WILL RETAIN A 20-30 PERCENT CHANCE OF A LATE AFTERNOON AND EVENING STORM FROM ACTIVITY THAT COULD EITHER DEVELOP IN-SITU INVOF A PIEDMONT SURFACE TROUGH AND/OR THAT IS MORE LIKELY TO INITIATE UPSTREAM OVER THE NC/SW VA MOUNTAINS AND INVOF THE AFOREMENTIONED FRONT...WHICH WOULD THEN PROPAGATE AWAY FROM THOSE FORCING MECHANISMS AND INTO THE NC PIEDMONT LATE THIS AFTERNOON AND EVENING. STRONG DIURNAL HEATING OF A DEEPLY MIXED BOUNDARY LAYER...AND ASSOCIATED STEEP LOW LEVEL LAPSE RATES AND 25-30 C DEWPOINT DEPRESSIONS...WOULD SUPPORT A CONDITIONAL RISK OF STRONG TO DAMAGING DOWNBURST WIND GUSTS IF CONVECTION INDEED DEVELOPS OVER OR PROPAGATES INTO...CENTRAL NC. HOWEVER...MID LEVEL FLOW AT THIS LATITUDE/OVER CENTRAL NC WILL REMAIN ONLY MODEST TO THE SOUTH OF THE MAIN BELT OF WESTERLIES AT THE BASE OF A BROAD TROUGH CENTERED NEAR JAMES BAY...SO ANY SEVERE OCCURRENCE SHOULD BE ISOLATED. HIGH TEMPERATURES NEAR OR SLIGHTLY ABOVE THOSE OF MON GIVEN A SLIGHT UPTICK IN FORECAST LOW LEVEL THICKNESS VALUES - UPPER 80S/AROUND 90 WHERE CLOUDS SHOULD BE MOST PREVALENT FROM KCTZ AND KGSB AND POINTS EASTWARD...TO 90-98 DEGREES ELSEWHERE...HOTTEST FROM AFP TO FAY. LOWS GENERALLY 70 TO 75...AFTER ANY CONVECTION THAT DOES OCCUR MOVES EAST AND/OR DISSIPATES BY LATE EVENING. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 350 AM TUESDAY... WHILE THE COLD FRONT WILL SETTLE SOUTH ACROSS CENTRAL NC AND SERVE AS A POSSIBLE TRIGGER FOR CONVECTION AGAIN WED AFTERNOON AND EVENING...GENERALLY WESTERLY FLOW ALOFT -INCLUDING A SIGNIFICANT DOWNSLOPE COMPONENT AT 850 MB- AND VEERED SURFACE FLOW INTO A PRE- FRONTAL TROUGH THAT THE MODELS INDICATE WILL HAVE DRIFTED INTO THE COASTAL PLAIN...SHOULD GENERALLY LIMIT COVERAGE. ANY SCATTERED OR WIDELY SO STORMS THAT DO FORM...HOWEVER...WOULD AGAIN POSE A RISK OF STRONG EVAPORATIVELY-ENHANCED WIND GUSTS. WEAK CAA NORTH OF THE BOUNDARY WILL TAKE THE EDGE OFF OF THE HEAT ACROSS THE NORTHERN PIEDMONT...WHERE LOWER 90S ARE EXPECTED...VERSUS MIDDLE TO UPPER 90S ONCE AGAIN OVER THE SOUTHERN PIEDMONT AND SANDHILLS. SLIGHTLY COOLER AND LESS HUMID AS THE FRONT SETTLES TO THE NEAR THE SC BORDER BY MORNING...WITH LOWS IN THE UPPER 60S TO AROUND 70 DEGREES. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 410 AM TUESDAY... THE COLD FRONT FORECAST TO BE NEAR THE NC-SC BORDER THURSDAY MORNING WILL MEANDER BACK TO THE NORTH ON THURSDAY...AS A WAVE OF LOW PRESSURE TRACKS FROM THE MID-MISSISSIPPI RIVER VALLEY REGION TOWARD THE OHIO VALLEY REGION IN RESPONSE TO A SHORTWAVE MOVING EAST FROM THE CENTRAL ROCKIES. THERE ARE STILL SIGNIFICANT MODEL DIFFERENCES IN THE AMPLITUDE/TIMING THE SYSTEM THAT RESULT IN BELOW AVERAGE FORECAST CONFIDENCE FOR LATE WEEK. THE NAM AND ECMWF SEEM TO BE MORE CONSISTENT IN SHOWING A DEEPER DISTURBANCE AND AND NOTICEABLY STRONGER SURFACE LOW THAT TRACKS JUST NORTH OF CENTRAL NC LATE THURSDAY INTO EARLY FRIDAY...WHILE THE GFS SHOWS A VARIETY OF DISTURBANCES IN WEST-NORTHWESTERLY FLOW ALOFT THAT EVENTUALLY EVOLVE INTO A DEEPER SHORTWAVE TROUGH CROSSING OUR REGION LATE FRIDAY. WILL CONTINUE BEST CHANCE POPS THURSDAY EVENING THROUGH FRIDAY AFTERNOON GIVEN THE AFOREMENTIONED CONSISTENCIES IN THE ECMWF AND NAM...THOUGH THE BEST COVERAGE MAY ULTIMATELY END UP TO OUR NORTH WITH THE RETREATING FRONTAL ZONE. WHILE THE STRONGEST MID-LEVEL WESTERLIES WILL RESIDE TO OUR NORTH DURING THIS PERIOD...THE AMPLITUDE OF THE DISTURBANCE DEPICTED IN THE ECMWF (ALBEIT IMPACTING THE AREA AT A POOR TIME DIURNALLY) AND THE PRESENCE OF THE FRONTAL ZONE SUGGEST A SEVERE THREAT ISN`T OUT OF THE QUESTION. THE TRAILING COLD FRONT WILL THEN CROSS THE AREA BY FRIDAY EVENING...USHERING IN SOME DRIER AIR AND LEAVING MOST OF THE CWA DRY AS THE FOCUS MOVES TOWARD THE COASTAL AREA FOR THE WEEKEND THE COMBINATION OF CLOUD COVER AND PERIODS OF SHOWERS/STORMS SHOULD LEAD TO HIGHS A BELOW NORMAL BY FRIDAY....REMAINING AT OR JUST BELOW NORMAL SATURDAY BEFORE SLOWLY TRENDING WARMER EARLY NEXT WEEK BENEATH RENEWED NORTHWESTERLY FLOW ALOFT. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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AS OF 800 AM TUESDAY... MOIST SOUTHERLY LOW LEVEL FLOW ON THE NNE PERIPHERY OF AN AREA OF LOW PRESSURE NEAR THE CENTRAL SC COAST THIS MORNING WILL MAINTAIN SCATTERED TO BROKEN IFR-MVFR RANGE CLOUDS AT RDU/FAY/RWI...WHICH WILL LIFT AND SCATTER TO VFR BETWEEN 13-16Z. WHILE AN ISOLATED TO WIDELY SCATTERED STORM WILL BE POSSIBLE AT ALL SITES IN ADVANCE OF AN APPROACHING COLD FRONT LATE THIS AFTERNOON AND EVENING... PARTICULARLY FROM INT/GSO TO RDU...AN AXIS OF MORE NUMEROUS SHOWERS AND STORMS WILL DEVELOP AND AFFECT THE EASTERN CAROLINAS...INCLUDING FAY AND VICINITY...BEGINNING AS EARLY AS THIS MORNING...BEFORE DIMINISHING BY THIS EVENING AS THE LOW PASSES BY TO THE EAST. ASIDE FROM A SMALL CHANCE OF A SHOWER/STORM WED-WED NIGHT... GENERALLY VFR CONDITIONS ARE EXPECTED THROUGH MID-WEEK. A FRONTAL SYSTEM WILL CROSS THE MIDDLE ATLANTIC REGION AND RESULT IN A PEAK IN THE PROBABILITY OF SHOWERS AND STORMS...AND SUB-VFR CONDITIONS...NC LATE THU-FRI.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...26 SHORT TERM...26 LONG TERM...22 AVIATION...26

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