Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 051448 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1050 AM EDT SUN JUL 5 2015 .SYNOPSIS...
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A SURFACE FRONT WILL REMAIN QUASI-STATIONARY NEAR THE VA AND NC BORDER TODAY...AHEAD OF AN UPPER LEVEL TROUGH AND ACCOMPANYING AREA OF SURFACE LOW PRESSURE THAT WILL DRIFT INTO THE CENTRAL APPALACHIANS THROUGH THIS EVENING. THE FRONT WILL RETREAT NORTHWARD WITH THE MIGRATION OF THE SURFACE LOW THROUGH THE MIDDLE ATLANTIC STATES ON MON.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1050 AM SUNDAY... JUST MINOR ADJUSTMENTS MADE TO THE NEAR TERM FORECAST...NAMELY TO INCREASE POPS TO LIKELY ACROSS THE SOUTHERN COUNTIES LATE THIS AFTERNOON-EARLY EVENING. WELL DEFINED MID-UPPER LEVEL LOW DEPICTED IN 12Z UPPER AIR ANALYSIS AND WATER VAPOR IMAGERY. SPOKES OF VORTICITY ROTATING AROUND THIS FEATURE WILL LIFT ACROSS CENTRAL NC...ESPECIALLY THE WESTERN HALF OF OUR FORECAST AREA THIS AFTERNOON AND TONIGHT. ATMOSPHERE ACROSS OUR REGION REMAINS QUITE MOIST WITH PRECIP WATER VALUES 1.4-1.7 INCHES. IN ADDITION...INSOLATION...THOUGH LIMITED FOR A TIME DUE TO A DECK OF MID LEVEL CLOUDS...WILL BE ENOUGH TO RESULT IN SLIGHT-MODERATE SFC INSTABILITY BY LATE AFTERNOON. EARLY MORNING ANALYSIS DEPICTS GOOD SPEED CONVERGENCE (10-15KTS) OVER SC IN TO SOUTHERN NC...MAINLY AIMED AT OUR SOUTHERN PIEDMONT COUNTIES. BASED ON APPROACH OF A VORTICITY MAXIMUM FROM THE WEST-SW THIS AFTERNOON...BELIEVE THAT CONVECTION WILL INITIALLY BE CONCENTRATED OVER THE SOUTHERN PIEDMONT. EXPECT ADDITIONAL CONVECTION TO DEVELOP ALONG A STALLED SFC FRONT DRAPED WEST-TO-EAST ALONG THE VA BORDER. BY 00Z...MAXIMUM INSTABILITY AXIS SHOULD EXTEND ALONG THE COASTAL PLAIN OF THE CAROLINAS SO EXPECT STORMS TO MIGRATE INTO THIS REGION BY EARLY EVENING. FOR NOW...CONTENT WITH LOW END LIKELY POPS ACROSS MOST OF CENTRAL NC LATER THIS AFTERNOON INTO TONIGHT. IF IT BECOMES APPARENT THAT STORMS WILL BE CLUSTERED OVER A PARTICULAR AREA FOR A FEW HOURS...THEN CATEGORICAL POPS WILL BE NEEDED. EARLY MORNING MESO ANALYSIS DEPICTS MARGINAL BULK SHEAR (25-30KTS) NEAR OUR WESTERN PERIPHERY...AND POTENTIAL FOR LOW LEVEL LAPSE RATES 9-9.5 DEG C OVER OUR SE COUNTIES THIS AFTERNOON. THUS HAVE MENTIONED THE POSSIBILITY OF AN ISOLATED SEVERE STORM IN THE HWO WITH THE MAIN THREAT WIND GUST UP TO 60KTS. TEMPS WARMING SMARTLY ACROSS SECTIONS OF THE PIEDMONT AND COASTAL PLAIN AT MID MORNING. DECK OF MID LEVEL CLOUDS CROSSING THE REGION LATE MORNING-ERLY AFTERNOON SHOULD TEMPER WARMING A BIT. IF NOT...MAY NEED TO ADJUST MAX TEMPS IN THE NE PIEDMONT TO NEAR 90...AND LOWER 90S IN THE KFAY-KGSB VICINITY. TONIGHT...PRESENCE OF A SHEAR AXIS NEAR OUR WESTERN BORDER SUGGEST THE POTENTIAL FOR A FEW SHOWERS TO PERSIST WELL INTO THE NIGHT. OTHERWISE BULK OF CONVECTION WILL DISSIPATE PRIOR TO MIDNIGHT. MAY SEE AREAS OF STRATUS DEVELOP PRIOR TO DAYBREAK ALONG WITH AREAS OF FOG THOUGH VISIBILITIES SHOULD REMAIN AT OR ABOVE 2 MILES MOST PLACES. MIN TEMPS UPPER 60S-LOWER 70S.
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&& .SHORT TERM /MONDAY AND MONDAY NIGHT/... AS OF 435 AM SUNDAY... THE SHORTWAVE TROUGH/CLOSED MID LEVEL LOW INITIALLY OVER THE TN VALLEY WILL CONTINUE TO LIFT SLOWLY NE AND DEAMPLIFY ACROSS THE CENTRAL APPALACHIANS THIS PERIOD...TAKING WITH IT THE ASSOCIATED FORCING FOR ASCENT TO THE NW OF CENTRAL NC. THE LIFTING OUT OF THE TROUGH WILL CAUSE THE SURFACE FRONT INITIALLY OVER SOUTHERN VA TO RETREAT NORTH THROUGH THE MIDDLE ATLANTIC STATES...LEAVING BEHIND A LEE/PIEDMONT TROUGH OVER CENTRAL VA AND THE CENTRAL CAROLINAS. HEIGHT RISES BEHIND THE DEAMPLIFYING TROUGH ALOFT AND WSW LOW LEVEL FLOW ON THE WEST SIDE OF THE PIEDMONT TROUGH SUGGEST CONVECTIVE COVERAGE SHOULD BE MINIMAL OVER THE SOUTHERN AND WESTERN PIEDMONT...WITH SCATTERED CONVECTION OTHERWISE EXPECTED ALONG AND EAST OF THE PIEDMONT TROUGH...AND IN ASSOCIATION WITH THE SEA BREEZE. HIGHS SIMILAR TO THOSE OF SUN...THOUGH UP TO A COUPLE OF DEGREES HIGHER OVER THE SOUTHERN PIEDMONT...CLOSE TO WHERE THE MODELS INDICATE THE DEVELOPMENT OF A LOW LEVEL THERMAL RIDGE CENTERED NEAR CLT. LOWS AGAIN AROUND 70...WITH MAINLY DRY CONDITIONS OVERNIGHT. && .LONG TERM /TUESDAY THROUGH SATURDAY/...
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AS OF 405 AM SUNDAY... WITH THE DEPARTURE OF THE INCREASINGLY SHEARED UPPER LOW OVER THE SOUTH-CENTRAL APPALACHIANS ON TUESDAY...THE PATTERN OVER THE SOUTHEAST US WILL SHIFT BACK INTO A ORE TYPICAL SUMMERTIME REGIME...WITH THE SUBTROPICAL RIDGE BUILDING ACROSS THE SOUTHERN US. MEANWHILE...PROGRESSIVE FLOW ACROSS THE NORTHERN US WILL ALLOW A SERIES OF SHORTWAVES TO CROSS THE GREAT LAKES REGION... AND TO SOME DEGREE KEEP HEIGHTS ALOFT FROM RISING TOO QUICKLY OVER THE CAROLINAS. THE FIRST SHORTWAVE WILL CROSS THE GREAT LAKES ON WEDNESDAY...WITH A TRAILING COLD FRONT SINKING SOUTH INTO THE MID- ATLANTIC REGION...BUT GIVEN THE FACT THAT MODELS HAVE TRENDED A LITTLE STRONGER...AND WARMER...WITH THE SUBTROPICAL RIDGE....EXPECT THE FRONT TO REMAIN NORTH OF OUR AREA. A LEE TROUGH WILL BE THE MAIN FOCUS FOR ISOLATED TO WIDELY SCATTERED SHOWERS AND STORMS EACH DAY...WITH THE POTENTIAL FOR DISTURBANCES TRACKING WEST TO EAST NEAR THE FRONTAL ZONE TO PROVIDE SOME ADDITIONAL FORCING AS THE FRONT EFFECTIVELY TRIED TO SINK SOUTH INTO THE AREA BY THE WEEKEND. THIS WILL BE DEPENDENT ON HOW THE RIDGE EVOLVES...AND THE MODELS ARE NOT IN FULL AGREEMENT ON HOW QUICKLY THE CENTER OF THE RIDGE WILL BUILD WEST OVER THE SOUTHERN PLAINS...WHICH WOULD ALLOW HEIGHTS TO FALL AGAIN ALONG THE EAST COAST. FOR NOW...WILL CONTINUE TO SHOW MAINLY SLIGHT CHANCE OF LOW END CHANCE POPS EACH DAY...WITH HIGHS INCREASINGLY IN THE 90-95 RANGE.
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&& .AVIATION /12Z SUNDAY THROUGH THURSDAY/... AS OF 750 AM SUNDAY... GENERALLY LIGHT SOUTH TO SOUTHWEST LOW LEVEL FLOW WILL PREVAIL OVER CENTRAL NC...ON THE SOUTH SIDE OF A QUASI-STATIONARY SURFACE FRONTAL ZONE IN THE VICINITY OF THE VA/NC STATE LINE. SCATTERED TO NUMEROUS SHOWERS AND STORMS THIS AFTERNOON WILL BE INITIALLY MOST PROBABLE AT TRIAD TAF SITES AND RDU...IN CLOSEST PROXIMITY TO BOTH THE FRONT AND AN UPPER LEVEL TROUGH FORECAST TO DRIFT SLOWLY NORTHEAST ACROSS THE TN VALLEY. THE TROUGH ALOFT...AND PRECEDING WEAK IMPULSES IN SOUTHWESTERLY FLOW ALOFT...WILL PROBABLY TRIGGER A NORTH TO SOUTH- ORIENTED BAND OR TWO OF ADDITIONAL SHOWERS AND STORMS THROUGH THIS EVENING. THERE WILL BE A CHANCE OF STRATUS LATE TONIGHT... PARTICULARLY WHERE RAIN OCCURS PRIOR...AND AT KFAY WHERE THE NAM AND SREF INDICATE THE BEST POTENTIAL FOR IFR CEILINGS. OUTLOOK: THE AFOREMENTIONED UPPER LEVEL TROUGH OVER THE TN VALLEY WILL CONTINUE TO LIFT SLOWLY NORTHEAST THROUGH THE APPALACHIANS AND DIRECT A MOIST AND WEAKLY PERTURBED SOUTHWEST FLOW ALOFT ACROSS NC THROUGH TUE. ABOVE AVERAGE PROBABILITIES OF MAINLY AFTERNOON-EARLY NIGHTTIME SHOWERS AND STORMS --AND ASSOCIATED SUB-VFR CONDITIONS-- WILL RESULT...WITH THE RELATIVE BETTER CHANCES ON MON. SUB-TROPICAL RIDGING WILL THEN EXPAND NORTH THROUGH MID-LATE WEEK...WITH ASSOCIATED MAINLY DRY AND WARMER/HOT CONDITIONS. && ..RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...WSS SHORT TERM...26 LONG TERM...22 AVIATION..26

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