Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 191405 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1005 AM EDT FRI SEP 19 2014 .SYNOPSIS...HIGH PRESSURE CENTERED NORTHEAST OF THE GREAT LAKES WILL EXTEND DOWN THROUGH VIRGINIA AND THE CAROLINAS THROUGH THE WEEKEND. A COLD FRONT WILL APPROACH FROM THE NORTHWEST SUNDAY... THEN MOVE SOUTHEAST THROUGH THE REGION SUNDAY NIGHT THROUGH EARLY MONDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 10 AM FRIDAY... A FEW SPRINKLES REMAIN OF WHAT WAS A DECENT AREA OF MODERATE TO HEAVY RAIN SHOWERS ACROSS THE WESTERN/SOUTHWEST PIEDMONT EARLIER THIS MORNING...FOCUSED ALONG A LOW-LEVEL MOISTURE CONFLUENCE ZONE SITUATED ALONG THE SOUTHERN FLANKS OF THE BUILDING SURFACE HIGH AND SELY ATLANTIC MOISTURE RETURN FLOW. THIS BEST BOUNDARY LAYER MOISTURE CONVERGENCE WILL GRADUALLY SHIFT SOUTH AND EAST OF THE AREA THROUGH THE REMAINDER OF THE DAY AS THE SURFACE HIGH WEDGES MORE PROMINENTLY SOUTHWARD INTO CENTRAL NC...RESULTING IN MORE OF A EASTERLY/NORTHEASTERLY LOW-LEVEL FEED. AS SUCH...IT APPEARS THAT THE BEST RAIN CHANCES ARE BEHIND US...WITH ONLY AN ISOLATED AFTERNOON SHOWER OR SPRINKLE POSSIBLE ACROSS THE FAR WESTERN PIEDMONT OWING TO WEAK UPSLOPE FLOW. LOW-LEVEL EASTERLY COMPONENT WILL RESULT IN A VERY SLOW DEMISE OF THIS MORNINGS PERVASIVE CLOUD COVER. IF SKIES REMAIN BROKEN TO OVERCAST...TEMPS WILL BE HELD DOWN IN THE MID-UPPER 70S. IF ENOUGH BREAKS OCCUR...COULD SEE TEMPS WARM INTO THE UPPER 70S-LOWER 80S. BELIEVE THE LATER SCENARIO WILL BE MORE PROBABLE ACROSS THE EAST/NORTHEAST WHILE MORE CLOUDS THAN SUN SHOULD OCCUR ACROSS THE SOUTH AND WEST. MAX TEMPS MOSTLY IN THE UPPER 70S TO AROUND 80 WITH MID 70S IN THE NW PIEDMONT. TONIGHT...EXPECT BULK OF CLOUDS TO DIMINISH WITH LOSS OF HEATING AND EVENTUAL ADVECTION OF A DRIER LOW LEVEL AIR MASS. EXPECT A STEADY EAST-NE WIND OVERNIGHT (5-10 MPH). THIS MIXING WILL PREVENT NEAR SURFACE AIR MASS FROM REALIZING FULL COOLING POTENTIAL. MIN TEMPS NEAR 60-LOWER 60S. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 315 AM FRIDAY... SATURDAY...DRY AIR RIDGE WILL EXTEND SW-NE ACROSS CENTRAL NC PROVIDING SUNNY-MOSTLY SUNNY SKIES TO START THE DAY. SHOULD SEE AN INCREASE IN HIGH LEVEL CLOUDINESS FROM THE SOUTHEAST SATURDAY AFTERNOON AS AN AREA OF LOW PRESSURE ORGANIZES OFF THE SE U.S. COAST. NOT EXPECTING THESE CLOUDS TO HAVE MUCH EFFECT INITIALLY ON TEMPS. LOW LEVEL THICKNESSES RANGE IN THE 1395-1402M RANGE...SUPPORTIVE OF MAX TEMPS NEAR-LOWER 80S. SATURDAY NIGHT...THICKER VEIL OF HIGH CLOUDS ANTICIPATED OVER MAINLY THE EAST HALF OF THE FORECAST AREA AS THE LOW PRESSURE SYSTEM MOVES NORTH-NORTHEAST OFFSHORE OF THE CAROLINA COAST. LATEST GFS SUGGEST POTENTIAL FOR LIGHT PRECIP AS FAR EAST AS I-95 CORRIDOR BY EARLY EVENING BUT THIS CURRENTLY APPEARS OVERDONE. PRESENCE OF HIGH LEVEL CLOUDS SHOULD MAINTAIN MILD OVERNIGHT TEMPS IN THE EAST WITH COOLER MIN TEMPS EXPECTED IN THE WEST WHERE SKIES WILL BE NO WORSE THAN PARTLY CLOUDY. MIN TEMPS UPPER 50S WEST TO MID 60S SE. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 345 AM FRIDAY... SPLIT STREAM FLOW WILL UNDERGO AMPLIFICATION THROUGH THE WEEKEND...AND RESULT IN A LEAD SOUTHERN STREAM TROUGH AND ASSOCIATED SFC FRONTAL WAVE LIFTING UP THE SOUTHEAST COAST...WHILE A SERIES OF STRONG NORTHERN STREAM SHORTWAVES CARVE A TROUGH AND PROPEL A SFC COLD FRONT ACROSS THE MIDDLE ATLANTIC AND NORTHEAST STATES SUN-MON. GUIDANCE IS THEN IN RELATIVELY GOOD AGREEMENT REGARDING THE SEPARATION AND RETREAT OF THE NORTHERN STREAM THAT LEAVES BEHIND MID- UPPER TROUGHINESS INVOF THE SOUTHEAST US COAST...WHILE THE AMPLIFIED RIDGING INITIALLY OVER WESTERN NOAM BUILDS...IN PROGRESS FLOW ALOFT...EASTWARD ACROSS THE GREAT LAKES/MID ATLANTIC/NORTHEAST. SUN: VERY WARM...AND DRY. AN APPALACHIAN-LEE SFC TROUGH WILL DEVELOP...BETWEEN THE AFOREMENTIONED NORTHERN STREAM SFC COLD FRONT APPROACHING FROM THE WEST AND THE OFFSHORE PASSING FRONTAL WAVE (A BAROCLINIC ONE WHICH MAY ACQUIRE SUB-TROPICAL CHARACTERISTICS AT BEST OWING TO THE STRONGLY SHEARED AND DEEP LAYER BAROCLINIC ENVIRONMENT IN WHICH IT WILL EVOLVE). UNDER MOSTLY SUNNY SKIES...FULL SUN TEMPERATURES WITH LOW LEVEL THICKNESS VALUES IN THE NEIGHBORHOOD OF 1415 METERS SUPPORT HIGHS SOLIDLY IN THE MIDDLE 80S. SUN NIGHT-MON: NWP GUIDANCE HAS CONTINUED TO HASTEN THE FRONTAL PROGRESSION THROUGH THE EASTERN CONUS SUCH THAT FROPA IN CENTRAL NC WILL LIKELY OCCUR LATE SUN NIGHT-EARLY MON PER A CONSENSUS OF THE 00Z NWP DATA. A FEW LINGERING SHOWERS FROM UPSTREAM CONVECTION...AND ALONG THE FRONTAL MOIST AXIS...MAY DRIFT INTO THE PIEDMONT SUN NIGHT...BUT DIURNAL TIMING AND GREATLY LIMITED GULF MOISTURE RETURN SUGGESTS COVERAGE SHOULD BE WIDELY SCATTERED AT BEST...BEFORE DIMINISHING WITH TIME OVERNIGHT AND EASTWARD EXTENT. THE FASTER FRONTAL PROGRESSION ALSO FAVORS THE FRONT BEING SE OF CENTRAL NC BY LATE MORNING...WHICH SHOULD ENSURE ANY ASSOCIATED REDEVELOPMENT OF CONVECTION SHOULD OCCUR IN COASTAL AREAS. LOW LEVEL DRY AIR ADVECTION WILL BE MORE PRONOUNCED THAN COLD AIR ADVECTION MON...SO TEMPERATURES ARE APT TO REMAIN RELATIVELY WARM...IN THE UPPER 70S TO LOWER 80S. TUE-THU: ANOTHER STRONG CANADIAN HIGH WILL EXPAND AND STRENGTHEN ACROSS MUCH OF THE CENTRAL AND EASTERN CONUS IN THE WAKE OF THE PASSING COLD FRONT...WHICH GUIDANCE SUGGESTS WILL CLEAR ALL BUT PERHAPS SOUTHERN FL BY MID NEXT WEEK. DRY AIR RIDGING IN CENTRAL NC WILL RESULT FROM THE PARENT HIGH CENTER OVER THE NORTHEAST...WHICH SHOULD RESULT IN DRY AND MILD CONDITIONS WITH TEMPERATURES IN THE MIDDLE 70S TO AROUND 80 DEGREES BOTH TUE-WED. SINCE THE SFC HIGH CENTER WILL BE SO WELL REMOVED FROM CENTRAL NC/OVER THE NE CONUS...THE ASSOCIATED MSLP GRADIENT WILL LIKELY MAINTAIN ENOUGH STIRRING OF THE SFC WINDS OVERNIGHT TO KEEP LOWS FROM DIPPING INTO THE 40S ON MORE THAN AN ISOLATED BASIS OVER THE NORTHERN PIEDMONT...WITH LOWS OTHERWISE IN THE 50S. BY THU...THE LOW LEVEL FLOW AROUND THE HIGH IS FORECAST TO ASSUME A MORE NE TO ENE COMPONENT...WHICH WOULD SERVE TO DIRECT MOISTURE/CLOUDINESS WESTWARD INTO CENTRAL NC WED NIGHT-THU. IN ADDITION...THE PAST COUPLE OF GUIDANCE RUNS HAVE BEEN HINTING AT THE POTENTIAL FOR ADDITIONAL SFC WAVE DEVELOPMENT INVOF THE SOUTHEAST COAST BY THU...WHICH WOULD ENHANCE BOTH CLOUD COVER AND RAIN CHANCES...PARTICULARLY OVER THE EASTERN CAROLINAS...BY THU. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... AS OF 10 AM FRIDAY... HIGH PRESSURE WILL BUILD INTO CENTRAL NC FROM THE NORTH. THE CIRCULATION AROUND THIS HIGH WILL RESULT IN AN LOW LEVEL EASTERLY FLOW ACROSS NC. THIS FETCH OFF THE ATLANTIC WILL SPREAD LOW LEVEL MOISTURE INTO OUR REGION. THIS WILL CAUSE A CLOUD DECK WITH BASES 4500-6000FT WITH OVERCAST CONDITIONS HIGHLY PROBABLE OVER THE PIEDMONT...AND SCATTER-BROKEN SKY CONDITIONS IN THE SANDHILLS AND COASTAL PLAIN. AS THE HIGH STRENGTHENS FURTHER INTO CENTRAL NC LATE TONIGHT INTO SATURDAY...DRIER AIR WILL INFILTRATE THE REGION... DIMINISHING THE CLOUD COVERAGE. A DEVELOPING AREA OF LOW PRESSURE OFFSHORE WILL SPREAD A VEIL OF HIGH CLOUDS ACROSS THE EAST HALF OF NC LATE SATURDAY THROUGH EARLY SUNDAY. A COLD FRONT WILL APPROACH FROM THE NW SUNDAY AND CROSS CENTRAL NC SUNDAY NIGHT THROUGH EARLY MONDAY. A PERIOD OF MVFR CEILINGS MAY OCCUR WITH THE FRONT. VFR CONDITIONS WILL RETURN MONDAY INTO TUESDAY AS HIGH PRESSURE AND ASSOCIATED DRIER AIR MASS BUILDS INTO OUR AREA. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...CBL/WSS SHORT TERM...WSS LONG TERM...MWS AVIATION...WSS

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