Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 250727 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 325 AM EDT FRI JUL 25 2014 .SYNOPSIS...A COLD FRONT PUSHING SOUTHEAST THROUGH THE REGION EARLY THIS MORNING WILL WEAKEN AND STALL NEAR THE SOUTH CAROLINA BORDER LATER TODAY...AS WEAK HIGH PRESSURE BUILDS IN FROM THE NORTH. THIS FRONT WILL DISSIPATE OVER THE WEEKEND AS SOUTHWEST FLOW RETURNS. A STRONGER COLD FRONT WILL MOVE THROUGH THE REGION EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 255 AM FRIDAY... WITH THE COLD FRONT HAVING PUSHED SOUTHWARD THROUGH MUCH OF NC... ASIDE FROM VARIABLY CLOUDY SKIES TODAY... MUCH OF CENTRAL NC WILL SEE IMPROVED WEATHER CONDITIONS... WITH THE EXCEPTION OF THE SE AND FAR SRN CWA. LAST NIGHT`S WIDESPREAD CONVECTION HAS SHIFTED OFF THE COAST... ALONG WITH A LEADING PROMINENT SHORTWAVE TROUGH SWINGING THROUGH THE BASE OF A WEAKENING TROUGH COVERING THE ERN THIRD OF NOAM. THE LOCATION OF THE COLD FRONT IS NOT EASY TO SPECIFY ON THE LATEST SURFACE MAP AS IT APPEARS TO HAVE MERGED WITH THE PREFRONTAL TROUGH... BUT IT LOOKS TO STRETCH FROM THE NC COASTAL AREA BACK ACROSS SRN NC AND NRN GA/AL. SURFACE WINDS HAVE SHIFTED AROUND TO LIGHT N OR NE AREAWIDE... AND THESE LIGHT SPEEDS COMBINED WITH STABILIZING LOW LEVELS POST-FRONT AND PLENTY OF RESIDUAL LOW LEVEL MOISTURE HAVE KEPT AREAS OF LOW CLOUDS OVER CENTRAL NC... CLOUDS THAT WILL BE SLOW TO DISLODGE/DISPERSE DESPITE LIMITED CLOUDINESS ABOVE. AS SUCH... EXPECT VARIABLY CLOUDY SKIES TODAY... WITH A BIT LOWER HUMIDITY LEVELS ESPECIALLY NORTH OF 64. THE FRONT IS EXPECTED TO REMAIN ACROSS SRN NC TODAY AS WEAK HIGH PRESSURE NOW CENTERED OVER NRN OH BUILDS IN... AND WHILE PW WILL SLIP TO NEAR/BELOW NORMAL VALUES OVER MOST OF CENTRAL NC... SOUTHERN SECTIONS SHOULD HOLD NEAR 2.0 INCHES. WITH ELEVATED DEW POINTS PERSISTING THERE ALONG WITH WEAK DPVA AND LINGERING WEAK UPPER DIVERGENCE... THE RISK OF SHOWERS/STORMS WILL CONTINUE ON OUR SOUTH... FOCUSED THROUGH THE AFTERNOON AND EARLY EVENING. A STORM OR TWO COULD BECOME STRONG GIVEN THAT DEEP LAYER SHEAR SHOULD STILL BE 25-30 KTS WITH MODELS SHOWING MUCAPE OF 1000-2000 J/KG... ALTHOUGH THIS RISK WITH BE LOWER IF THE THICKER LOW CLOUDS HANG ON LONGER AND INHIBIT INSOLATION. ISOLATED SHOWERS ARE A GOOD BET OVER THE REST OF THE FORECAST AREA THIS MORNING WITH A LOBE OF VORTICITY SWINGING THROUGH THE AREA... BUT LATE MORNING THROUGH THE AFTERNOON SHOULD BE DRY OUTSIDE OF THE AFOREMENTIONED SOUTHERN SECTIONS WITH 20-30 M HEIGHT RISES. HIGHS 84- 89... IN LINE WITH THICKNESSES THAT ARE PROJECTED TO BE 15-20 M BELOW NORMAL. MOISTURE PERSISTING BENEATH THE SUBSIDENCE INVERSION ALOFT SHOULD TRANSLATE TO PARTLY CLOUDY SKIES TONIGHT. HAVE HELD ONTO LOWS IN THE 66-71 RANGE. -GIH && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... AS OF 325 AM FRIDAY... EXPECT A LARGELY DRY DAY WITH INCREASED SUNSHINE. THE WEAKENING MID LEVEL TROUGH AXIS WILL SHIFT OFF THE COAST WITH MODEST HEIGHT RISES CONTINUING OVER NC. THE QUICKLY WEAKENING SURFACE FRONTAL ZONE NEAR THE NC/SC BORDER WILL FALL APART AND BE OVERTAKEN BY INCREASING LOW LEVEL SOUTHWEST FLOW AND DEVELOPMENT OF A WEAK PIEDMONT TROUGH. PW IS EXPECTED TO BE AT OR UNDER 1.2 INCHES TO START THE DAY... BUT IS FORECAST TO REBOUND TO AROUND 1.8 INCHES IN STRIP FROM CENTRAL VA THROUGH CENTRAL NC BY LATE AFTERNOON... WHICH THEN DRIFTS TO ERN NC SAT NIGHT. CORRESPONDINGLY THE MODELS DEPICT MODERATE INSTABILITY... MUCAPE OF 1000-1500 J/KG ON THE GFS LATE IN THE DAY... WITH AROUND 1000 J/KG LINGERING IN THE FAR EAST OVERNIGHT. BUT THE MODELS GENERATE LITTLE MORE THAN AN ISOLATED SHOWER OR STORM AS THE COLUMN REMAINS WARM/STABLE AND DRY THROUGH THE 850-500 MB LAYER. WILL KEEP THE FORECAST DRY... AS ANY CONVECTION WOULD BE EXTREMELY ISOLATED. THICKNESSES REBOUND TO JUST 5-10 M BELOW NORMAL... WHICH WITH DECENT SUNSHINE SUPPORTS HIGHS OF 89-93. LOWS 69-74... MILDER THAN TONIGHT DUE TO THE RETURN OF HIGHER DEWPOINTS. -GIH && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 305 PM THURSDAY... SUNDAY THROUGH MONDAY NIGHT... A STRONG SHORTWAVE MOVING SOUTHEAST OUT OF THE CANADIAN ROCKIES ON SUNDAY WILL BEGIN THE AMPLIFICATION OF THE LONGWAVE PATTERN HEADING INTO NEXT WEEK. CONVECTION PASSING TO OUR NORTH ACROSS VA MAY BLEED SOUTH INTO MAINLY THE NORTHERN PORTIONS OF THE AREA...PARTICULARLY SUNDAY EVENING BASED ON CURRENT PROGS. HOWEVER THE MAIN FORCING TO IMPACT CENTRAL NC WILL COME MONDAY WHEN MODELS SHOW ADDITIONAL ENERGY...ACCOMPANIED BY STRONG HEIGHT FALLS AND A BELT OF ENHANCED WESTERLIES...SWINGING ACROSS THE AREA. GIVEN THAT TEMPS ARE EXPECTED TO BE WELL INTO THE MID 90S ON SUNDAY AND AT LEAST THE LOWER 90S ON MONDAY...INSTABILITY SHOULD BE FAVORABLE AHEAD OF THE FRONT. WHILE THERE IS STILL SOME UNCERTAINTY AS TO HOW MUCH OVERLAP THERE WILL BE BETWEEN THE BEST INSTABILITY AND STRONGEST SHEAR...THE SETUP LOOKS PRETTY GOOD FOR SEVERE WEATHER AT DAY 5 IN LATE JULY. TUESDAY THROUGH THURSDAY... MEDIUM RANGE ENSEMBLES SHOW AN UNSEASONABLY DEEP UPPER TROUGH DEVELOPING OVER THE EASTERN US BY MID WEEK WITH AN UPPER LOW CENTERED JUST SOUTH OF THE HUDSON BAY. GIVEN THAT BOTH THE GFS AND ECMWF SHOW THE SYNOPTIC FRONT REACHING THE GULF OF MEXICO... CONFIDENCE IS HIGH THAT TEMPS WILL BE BELOW NORMAL MUCH OF NEXT WEEK. LOW-LEVEL THICKNESSES ARE PROGGED TO DIP BELOW 1390M...WHICH SUGGESTS HIGHS IN THE LOW/MID 90S AND LOWS IN THE LOW/MID60S... POSSIBLY TOUCHING THE UPPER 50S IN THE COOLEST SPOTS. THE AIRMASS CHANGE WILL ALSO BRING LOWER HUMIDITY...AND WITH DEWPOINTS DROPPING INTO THE 50S THE CHANCES OF SHOWERS OR STORMS WILL BE RELATIVELY LOW UNTIL RETURN FLOW DEVELOPS LATER IN THE WEEK. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 125 AM FRIDAY... PROBLEMATIC AVIATION CONDITIONS EARLY THIS MORNING... AS SCATTERED TO BROKEN CLOUDS BASED BETWEEN 600 AND 1400 FT AGL MEANDER ABOUT CENTRAL NC. WITH THESE LOW CIGS EXPECTED TO COME AND GO THROUGH DAYBREAK... THE TIMING OF MVFR/IFR CIGS IS MADE DIFFICULT. EXPECT CIGS TO VARY BETWEEN VFR AND MVFR/IFR THROUGH DAYBREAK AT ALL SITES AS THESE CLOUDS DRIFT OVER THE REGION... WITH MVFR/IFR DOMINATING. MVFR CIGS ARE EXPECTED THROUGH THE MORNING AS THESE CLOUDS LIFT SLOWLY... WITH CIGS NOT REACHING VFR UNTIL CLOSE TO 18Z... AND EVEN AFTER THIS TIME AT FAY... CLOSE TO WHERE THE COLD FRONT IS EXPECTED TO HAVE PUSHED BY AFTERNOON. A FEW SHOWERS AND ISOLD STORMS WILL BE RESTRICTED TO NEAR FAY THIS AFTERNOON. VFR CIGS ARE EXPECTED TO PERSIST THEN FROM MID AFTERNOON THROUGH THE END OF THE TAF PERIOD. AS THE FRONT SETTLES SOUTH OF ALL TAF SITES THIS MORNING... EXPECT A LIGHT BREEZE FROM THE NORTH TO DOMINATE THROUGH THE DAY. LOOKING BEYOND 06Z EARLY SAT MORNING... EXPECT CONTINUED VFR CIGS THROUGH DAYBREAK SAT... ALTHOUGH POCKETS OF IFR FOG ARE POSSIBLE 09Z- 13Z SAT MORNING... ESPECIALLY AT RWI/FAY. OTHERWISE... VFR CONDITIONS ARE LIKELY TO DOMINATE THROUGH THE WEEKEND WITH HIGH PRESSURE BUILDING IN... FOLLOWED BY A RESUMPTION OF SOUTHWEST FLOW AND PIEDMONT TROUGH LATE IN THE WEEKEND. A COLD FRONT WILL APPROACH FROM THE NW EARLY NEXT WORK WEEK... BRINGING THE POTENTIAL FOR SUB- VFR SHOWERS/STORMS... PARTICULARLY MONDAY. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...HARTFIELD LONG TERM...BLS AVIATION...HARTFIELD

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