Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 051729 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 130 PM EDT SUN JUL 5 2015 .SYNOPSIS... 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. && .NEAR TERM /THROUGH TONIGHT/... 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. && .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/... 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. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... AS OF 130 PM SUNDAY... A MODERATELY UNSTABLE AND MOIST AIR MASS ALONG WITH THE APPROACH AND CROSSING OVERHEAD OF A FEW DISTURBANCES ALOFT WILL RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS ACROSS CENTRAL NC THIS AFTERNOON AND THIS EVENING. THIS SCATTERED CONVECTION MAY AFFECT OPERATIONS AT ANY OF THE TAF SITES THROUGH 01Z. EXPECT MVFR CONDITIONS IN VICINITY OF THE SHOWERS AND STORMS ALONG WITH GUSTY SFC WINDS 25-35KTS. AFTER 01Z...SHOULD SEE A DECREASE IN CONVECTIVE COVERAGE. OVERNIGHT...AND MAINLY AFTER 08Z...COULD SEE AREAS OF LOW STRATUS DEVELOP AND POSSIBLY BECOMING WIDESPREAD AFTER 10Z. CONFIDENCE ABOUT 50/50 SO HAVE MENTIONED A TEMPO GROUP FOR CEILINGS. IF GUIDANCE OR SATELLITE IMAGERY POINTS TOWARD ITS OCCURRENCE...THEN A PREDOMINATE GROUP MAY BE NECESSARY. THE WEATHER PATTERN WILL REMAIN UNSETTLED MONDAY AND POSSIBLY INTO TUESDAY AS A WEAK UPPER LEVEL LOW DRIFTS THROUGH THE CENTRAL APPALACHIANS AND MID ATLANTIC. THIS SHOULD CONTINUE A THREAT FOR SCATTERED CONVECTION MONDAY AFTERNOON...AND A LITTLE LESS OF A CHANCE ON TUESDAY. THERE WILL ALSO BE A CHANCE FOR EARLY MORNING STRATUS. THROUGH THE REMAINDER OF THE WORK WEEK...AN AREA OF HIGH PRESSURE WILL BE STRENGTHENING OVER THE SOUTHERN PLAINS/LOWER MS VALLEY AND EXPAND EAST TOWARD OUR REGION. THIS WEATHER FEATURE MAY LIMIT AFTERNOON CONVECTIVE DEVELOPMENT TO NO MORE THAN 20 TO 30 PERCENT. && ..RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...WSS SHORT TERM...26 LONG TERM...22 AVIATION..WSS

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