Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221814 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 215 PM EDT TUE JUL 22 2014 .SYNOPSIS...
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A SURFACE FRONT ALONG THE COAST WEAKENS OVERNIGHT AND EARLY WEDNESDAY AHEAD OF A COLD FRONT. THIS COLD FRONT WILL MOVE THROUGH MUCH OF THE REGION THURSDAY AND THURSDAY NIGHT...SLOWING AND WEAKENING AS IT APPROACHES SOUTH CAROLINA EARLY FRIDAY. THE WEAK FRONT THEN LINGERS NEAR THE SOUTH CAROLINA BORDER AND THE NORTH CAROLINA COAST THROUGH FRIDAY NIGHT.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1100 AM TUESDAY... UPDATE...BREAKS IN THE CLOUDINESS ARE STARTING TO SHOW UP...WITH THE VERY MOIST AIRMASS IN PLACE WITH THE PLUME OF 2.0 PRECIPITABLE WATER MAINTAINING ITS GULF AND ATLANTIC FEEDS. DIURNAL HEATING WOULD BE CONDUCIVE TO WIDESPREAD CONVECTIVE COVERAGE...IF...IF WE HAD SOME MODEST LOW LEVEL FORCING/CONVERGENCE TO UTILIZE THE AVAILABLE INSTABILITY. LOW LEVEL FLOW IS ONLY WEAKLY CONVERGENT EAST OF THE AREA IN THE VICINITY OF THE COASTAL TROF. THE UPPER LOW HAS SETTLED IN THE DELTA REGION AS EXPECTED...AND MID LEVEL DYNAMICS WILL BE LESS ROBUST TODAY AS WELL. SHOULD SEE DECENT COVERAGE...BUT THE LACK OF MID AND UPPER SUPPORT SUGGEST FEWER THUNDERSTORMS AND WILL THUS ADJUST WEATEHR GRIDS TO REFLECT WORDING FAVORING SHOWERS. TEMPS ARE ON TRACK TO REACH MID 80S...AND COULD SEE SOME UPPER 80S IN THE EAST IF INSOLATION PERSISTS FOR AN HOUR OR TWO. FOR TODAY/TONIGHT: WE ANTICIPATE ANOTHER ROUND OF DECENT SHOWER/STORM COVERAGE WITHIN A MOIST AND VOLATILE AIR MASS... WITH ONCE AGAIN THE POTENTIAL FOR POCKETS OF HEAVY RAIN. LATEST SURFACE MAP SHOWS THE FRONTAL ZONE WINDING AROUND THE INTERIOR SOUTHEAST STATES AND ACROSS COASTAL NC... LEADING TO A VERY LIGHT FLOW FROM THE NE OR E INTO NC. THIS WILL KEEP LOW LEVEL ATLANTIC-SOURCE MOISTURE PUMPING INTO THE AREA... AND ALOFT AS WELL AS THE DAMP SURGE EAST AND NORTH OF THE GULF COAST LOW IS EASILY SEEN ON WATER VAPOR IMAGERY... DRAWING IN DEEPER MOISTURE OFF FL AND THE BAHAMAS. GOES SOUNDER PW VALUES ARE WIDESPREAD 2.0-2.5 OVER NC (HIGHEST ACROSS SRN NC)... AND WHILE THE BLENDED TPW AND GSO UA VALUES ARE A BIT LOWER THEY`RE STILL 120-150% OF NORMAL. MODELS SHOW THE HIGHER PW CONTINUE TO SURGE TO THE WNW INTO CENTRAL NC ON THE CYCLONIC MID LEVEL FLOW FROM THE SE AND E TODAY. IT IS POSSIBLE THAT THE BEST COVERAGE COULD HOLD OVER ERN NC AS MODELS INDICATE THAT THE MAXIMUM LOW LEVEL MOISTURE TRANSPORT WILL HOLD EAST OF THE FORECAST AREA TODAY... ALONG AND EAST OF THE STATIONARY FRONTAL ZONE. BUT THIS FRONTAL ZONE SHOULD DISSIPATE TODAY IN FAVOR OF A PIEDMONT TROUGH AS THE OFFSHORE RIDGE BECOMES A BIT MORE DOMINANT WITH THE WESTWARD NUDGE OF THE GULF UPPER LOW... AND FORECAST SOUNDINGS SHOW A DEEP LCL-0C LAYER SUPPORTING WARM RAIN PROCESSES AND HIGH PRECIP EFFICIENCY. WILL TAKE POPS UP TO 50-60%... SPREADING INTO THE SOUTH FIRST THEN TOWARD THE NNW. COVERAGE SHOULD TAPER DOWN FAIRLY QUICKLY TO ISOLATED DURING THE MID-LATE EVENING AS LOW LEVEL FLOW TAKES ON A GREATER WESTERLY COMPONENT. WILL MAINTAIN A THREAT OF LOCALLY HEAVY DOWNPOURS AND ISOLATED FLOODING CONCERNS IN THE HAZARDOUS WEATHER OUTLOOK... GIVEN THE HIGH-PW AND HIGH PRECIP EFFICIENCY COUPLED WITH THE ALREADY-WET GROUND MOST PLACES. MBE MOVEMENT SHOULD BE A BIT GREATER THAN MONDAY... BUT WITH WEAK LOW-MID LEVEL WINDS... SOME SLOWER CONVECTIVE CLUSTERS COULD STILL DROP HIGH RAIN TOTALS. HOWEVER... OVERALL LOW COVERAGE OF THESE HIGHER TOTALS HOWEVER PRECLUDE ISSUING A FLASH FLOOD WATCH AT THIS TIME. HIGHS 83-88. LOWS TONIGHT 71-75 WITH MORE FOG/STRATUS DEVELOPMENT LATE. -GIH
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&& .SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
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AS OF 240 AM TUESDAY... FOR WED/WED NIGHT: THE SURFACE PATTERN WILL FEATURE A PIEDMONT TROUGH AHEAD OF THE COLD FRONT PUSHING TOWARD THE SSE OVER THE OH VALLEY... AS 850 MB FLOW BECOMES MAINLY WESTERLY. WE`LL SEE IMPROVING DEEP LAYER SHEAR AS THE BROAD TROUGH DIGS OVER ERN CANADA/THE GREAT LAKES/NORTHEAST WITH THE WESTERLIES INCHING SOUTHWARD TOWARD NC... PROMPTING DECENT HEIGHT FALLS ALOFT OF 20-50 M. EXPECT REDUCED CLOUDINESS ON WED AS WE LOSE THE TAP OF DEEPER BAHAMIAN MOISTURE WITH MID LEVELS EXHIBITING MINOR DRYING... AND THIS SHOULD NOT ONLY PUSH UP TEMPS (THICKNESSES ARE PROJECTED TO BE 5-8 M HIGHER WED THAN TODAY) BUT SHOULD ALSO PUSH UP INSTABILITY... AND THE SREF MEAN MLCAPE WED IS 1500-2000 J/KG ACROSS THE AREA. DEEP LAYER SHEAR REMAINS MODEST HOWEVER... JUST AROUND 15-20 KTS AT MOST... BUT NEVERTHELESS EXPECT A BIT MORE ORGANIZED SCATTERED STORMS TO DEVELOP. WILL KEEP POPS AS CHANCE... FOCUSED ON THE AFTERNOON/EVENING. HIGHS 89-93. STICKY LOWS OF 71-75 WED NIGHT... WITH A CONTINUED THREAT OF ISOLATED SHOWERS/STORMS AS WE MAINTAIN MARGINAL TO MODERATE INSTABILITY AHEAD OF THE FRONT. -GIH THURSDAY AND THURSDAY NIGHT: AN UPPER LEVEL TROUGH WILL MOVE OVER CENTRAL NC FROM THE WEST AND STALL OVER THE CAROLINAS. THE INITIAL SURFACE FRONT WILL MOVE THROUGH MUCH OF CENTRAL NC THURSDAY AND THURSDAY NIGHT. THE 00Z GFS INDICATES NC WILL BE SITUATED UNDER THE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET AND FORECASTS MID LEVEL LAPSE RATES OF 6-6.5 C/KM. THE BEST INSTABILITY ON THURSDAY WILL BE ALONG AND EAST OF THE FRONT...WITH MUCAPE AND MLCAPE VALUES FORECAST FROM 1000 J/KG IN THE NW TO 2500 J/KG ALONG THE NC COAST. BULK SHEAR IS ALSO FORECAST TO BE DESCENT TO GOOD...ESPECIALLY ALONG THE EAST AND SE...WITH VALUES OF 25 TO 35 KTS...SUPPORTING MORE ORGANIZED CONVECTION AND INCREASING POTENTIAL FOR STORM TO BECOME SEVERE... ALTHOUGH THE LOW LEVEL SHEAR VALUES WILL BE RELATIVELY WEAK. THUS... EXPECT THE MAIN SEVERE THREATS TO BE DAMAGING WINDS AND HAIL. HEAVY RAIN WILL ALSO BE A THREAT ON THURSDAY GIVEN THE PWAT VALUES AROUND 2 INCHES. EXPECT HIGHS IN THE UPPER 80S NW TO LOW 90S SE AND OVERNIGHT LOWS IN THE MID 60S TO LOW 70S. FRIDAY: THE INITIAL SURFACE FRONT WILL MOVE THROUGH MUCH OF CENTRAL NC THURSDAY AND THURSDAY NIGHT...WITH WINDS VEERING AROUND TO THE NORTHWEST AND COOL HIGH PRESSURE BUILDING IN BEHIND IT FOR FRIDAY. IT IS STILL UNCERTAIN HOW FAR THE COOLER AIR WILL MAKE IT INTO THE AREA AS WEAK LOW PRESSURE IS EXPECTED TO SIT ALONG THE CAROLINA COAST FRIDAY. REGARDLESS...HIGHS ON FRIDAY SHOULD BE 3-5 DEGREES COOLER THAN THURSDAY...MID TO UPPER 80S. GIVEN THE LINGERING SFC LOW ALONG THE COAST AND THE FRONT STALLING IN THE VICINITY OF NC/VA... THERE WILL BE THE CHANCE FOR ADDITIONAL SHOWERS AND STORMS ON FRIDAY ACROSS THE SOUTHEAST. PWATS WILL DECREASE SIGNIFICANTLY THROUGHOUT THE DAY FRIDAY...DOWN TO AROUND 1.00 TO 1.20 INCHES BY FRIDAY NIGHT AS MID LEVEL DRY AIR IS ADVECTED INTO THE REGION. -KC
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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AS OF 215 PM TUESDAY... THE GFS AND THE ECMWF ARE FAIRLY CONSISTENT IN MOVING THE UPPER- LEVEL TROUGH AXIS JUST EAST OF CENTRAL NORTH CAROLINA OVERNIGHT FRIDAY INTO SATURDAY. BOTH SETS OF GUIDANCE ALLUDE TO WEAK SHORTWAVE RIDGING SATURDAY NIGHT... FOLLOWED BY A MID-LEVEL SHORTWAVE MOVING THROUGH SOMETIME ON SUNDAY WITH THE TYPICAL TIMING DIFFERENCES OUT TO THE FIFTH DAY. AS AN UPPER-LEVEL TROUGH DEEPENS OVER THE EASTERN UNITED STATES EARLY NEXT WEEK...BACKING WINDS ALOFT MORE TO THE SOUTHWEST OCCUR. THE GFS AND ECMWF ARE BOTH DRY FRIDAY NIGHT AND MOSTLY DRY SATURDAY BEHIND THE TROUGH ALOFT AND UNDER WEAK HIGH PRESSURE ESPECIALLY EARLY SATURDAY FOLLOWED BY WEAK SURFACE TROUGH DEVELOPMENT SATURDAY AFTERNOON. FOR NOW...RETAINED THE SLIGHT CHANCE OF THUNDERSTORMS ALONG AND EAST OF THE INTERSTATE 95 CORRIDOR FOR SATURDAY WITH THE ECMWF SHOWING THE PRESENCE OF SOME MID-LEVEL MOISTURE...BUT GFS MODEL SOUNDINGS ARE STABLE AND IF THE CURRENT TREND OF CHANCES BELOW CLIMATOLOGY CONTINUES EVEN THESE SMALL CHANCES MAY EVENTUALLY BE REMOVED FROM THE FORECAST. 1000-850MB THICKNESSES ARE WARMEST SUNDAY AND THAT MAY BE THE WARMEST DAY OF THE LONG-TERM PERIOD BEFORE LOWERING HEIGHTS ALOFT TAKE PLACE. THE ECMWF IS MUCH MORE MOIST AND UNSTABLE SUNDAY COMPARED TO THE GFS AND WILL MAINTAIN THE CHANCES FOR SHOWERS AND STORMS WITH THE HIGHER CHANCES ALONG AND NORTH OF U.S. 64 CLOSER TO THE EXPECTED TRACK OF ANY MID-LEVEL SHORTWAVE AND AN APPROACHING SURFACE FRONT. WITH THE DEEPENING TROUGH...BOTH THE GFS AND ECMWF CURRENTLY MOVE THE SURFACE FRONT THROUGH CENTRAL NORTH CAROLINA MONDAY INTO EARLY TUESDAY...LINGERING A SURFACE TROUGH NEAR THE CAROLINA COAST. WHILE CHANCES FOR PRECIPITATION INCREASE CLOSER TO CLIMATOLOGY EARLY NEXT WEEK ESPECIALLY ON THE GFS...GENERAL QPF IS NOT TERRIBLY HIGH AND THEN HIGHER RELATIVE TO THE REST OF CENTRAL NORTH CAROLINA ALONG AND EAST OF U.S. 1. THIS COULD BE...IN PART...DUE TO MORE OF A WESTERLY LOW-LEVEL FLOW ON FORECAST MODEL SOUNDINGS OVER THE WESTERN PIEDMONT...AT LEAST FOR MONDAY. STILL...WILL FORECAST A CHANCE OF SHOWERS AND THUNDERSTORMS THROUGHOUT CENTRAL NORTH CAROLINA MONDAY WITH THE FRONT AND THEN A SLIGHT CHANCE IN THE TRIAD AND CHANCES ELSEWHERE ON THE SEVENTH DAY...HIGHER THEN TOWARD KFAY AND KGSB...BASED ON THE EXPECTED SURFACE FRONTAL POSITION AND THE SOUTHWEST FLOW ALOFT.
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&& .AVIATION /18Z TUESDAY THROUGH SUNDAY/... AS OF 130 PM TUESDAY... FOR THE CURRENT TAF PERIOD...SPOTTY SHOWERS AND ISOLATED THUNDERSTORMS THIS AFTERNOON WILL LINGER INTO THE EVENING...WANING WITH LOSS OF HEATING. CONDITIONS WILL BE VFR EXCEPT FOR MVFR TO BRIEFLY IFR IN THE VICINITY OF CONVECTION. A TYPICAL BRIEF PERIOD OF MVFR TO BRIEFLY IFR CIGS AND VSBY IS EXPECTED TONIGHT IN THE 08-13Z TIME FRAME...EXCEPT THAT CONDITIONS WILL BE LOWER AND DEVELOP A COUPLE OF HOURS SOONER AT SITES THAT RECEIVE RAIN THIS AFTERNOON/EVENING. WINDS WILL BE MORE UNIFORMLY OUT OF THE SOUTHWEST TOMORROW...BUT STILL LIGHT...LESS THAN 10 KNOTS. AGAIN EXPECT WIDELY SCATTERED CONVECTION... MAINLY AFTER 18Z...WITH BETTER POTENTIAL FOR SHOWERS IN THE WEST... GSO/INT...AND AT FAY WHERE CONDITIONS WILL BE A LITTLE MORE UNSTABLE. SOUTHWEST FLOW WILL CONTINUE THROUGH THURSDAY AS A FRONT APPROACHES FROM THE WEST. SHOWERS AND THUNDERSTORMS WILL BE MORE WIDESPREAD ON THURSDAY INTO EARLY THURSDAY NIGHT. THERE WILL BE A LINGERING CHANCE OF CONVECTION IN THE EAST... RWI/FAY...INTO THE WEEKEND AS THE FRONT STALLS ALONG THE COAST...OTHERWISE VFR CONDITIONS ARE EXPECTED FRIDAY THROUGH SUNDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DJF NEAR TERM...MLM/HARTFIELD SHORT TERM...HARTFIELD/KC LONG TERM...DJF AVIATION...MLM

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