Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 181522 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1122 AM EDT MON AUG 18 2014 .SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES WILL CROSS THE REGION THROUGH MID-WEEK IN ASSOCIATION WITH A NORTHWEST FLOW ALOFT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1115 AM MONDAY... OVERVIEW: A POTENT SHORTWAVE LOCATED OVER SOUTHERN WV AND SOUTHWESTERN VA AT 15Z IS PROGGED TO FURTHER DEAMPLIFY AS IT TRACKS ESE THROUGH SOUTHERN VA AND NORTHEAST NC THIS AFTERNOON. THE COMPACT NATURE OF THIS FEATURE SUGGESTS DPVA WILL BE CONFINED IN CLOSE PROXIMITY THEREOF...I.E. NORTH OF HWY 64 TO THE VA BORDER. THIS FEATURE IS ALREADY AIDING CONVECTIVE DEVELOPMENT IN THE TRIAD...AND SHOULD CONTINUE TO SUPPORT SCATTERED DEVELOPMENT INVOF BUY-IGX-TDF- HNZ-LHZ-IXA THROUGH 18-21Z (W-E). ANOTHER DISTURBANCE LOCATED OVER NORTHERN GA AND NORTHWEST SC AT 15Z IS PROGGED TO TRACK EAST/ESE ACROSS UPSTATE SC AND SOUTHERN NC LATE THIS AFTERNOON THROUGH THIS EVENING...FURTHER COMPLICATING THE CONVECTIVE FORECAST. PERVASIVE CLOUD COVER AND INTERMITTENT PRECIP WILL SIGNIFICANTLY HAMPER DIURNAL DESTABILIZATION. HOWEVER...MARGINAL INSTABILITY AND TROPICAL- LIKE MOISTURE (PWAT 1.80-2.00") WILL BE MORE THAN SUFFICIENT TO SUPPORT SCT/WIDESPREAD CONVECTION AS LONG AS THE APPROPRIATE FORCING IS IN PLACE. PRECIP/TEMPS: EXPECT THE BEST CHANCE OF CONVECTION THROUGH EARLY/MID AFTERNOON TO BE ALONG AND NORTH OF HWY 64 ACROSS THE NORTHERN PIEDMONT/NE COASTAL PLAIN...WITH A SUBSIDENT PERIOD FOR SEVERAL HOURS THEREAFTER IN THAT REGION. BY MID/LATE AFTERNOON INTO THIS EVENING...EXPECT THE BEST CHANCE FOR CONVECTION SOUTH OF HWY 64 NEAR THE SC BORDER AS THE UPSTREAM WAVE IN GA/SC TRACKS NEAR OR JUST SOUTH OF THE NC/SC BORDER. WILL CONTINUE TO MENTION A LOW CHANCE OF CONVECTION OVERNIGHT GIVEN DEEP MOISTURE IN THE PRESENCE OF AN ACTIVE UPPER LEVEL PATTERN. DUE TO PERVASIVE CLOUD COVER AND INTERMITTENT CONVECTION...HIGHS TODAY WILL BE COOLER THAN EXPECTED SEVERAL DAYS AGO...ESP ACROSS THE N/NW PIEDMONT. WILL INDICATE HIGHS FROM THE LOWER/MID 80S TO UPPER 80S/NEAR 90F IN THE SANDHILLS AND SE COASTAL PLAIN. LOWS TONIGHT IN THE LOWER 70S. -VINCENT && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 300 AM MONDAY... MID/UPPER LEVEL SHORTWAVE VORT DISTURBANCE INVOF OF ARKLATEX THIS MORNING IS FORECAST TO PROGRESS EAST ACROSS THE LOWER MS VALLEY TODAY AND ACROSS THE SOUTHEAST DURING PRIME HEATING TUESDAY AFTERNOON. CONVECTIVE COVERAGE SHOULD BE MORE SCATTERED IN NATURE WITH HIGHEST POPS IN THE EAST WITHIN THE CONTINUED HIGH +2.0 PWAT AS DRIER AIR BEGINS TO SPREAD IN FROM THE WEST. 0-6KM SHEAR DROPS OFF TO 10-15KTS BUT STRONGER HEATING AND RESULTANT MODERATE DESTABILIZATION COULD SUPPORT AN ISOLATED STRONG TO SEVERE STORM TUESDAY AFTERNOON. MUCH LIKE MONDAY NIGHT...PERIOD OF SYNOPTIC SCALE SUBSIDENCE TUESDAY EVENING/NIGHT IN THE WAKE OF THE UPPER WAVE MOVING OFF THE SE COAST SHOULD RESULT IN DRY CONDITIONS TUESDAY NIGHT. WARMER ON TUESDAY WITH HIGHS RANGING FROM UPPER 80S NW TO LOWER 90S SE. LOWS TUESDAY NIGHT IN THE UPPER 60S NW TO LOWER 70S SE. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 300 AM MONDAY... THE LONG TERM PERIOD WILL BE CHARACTERIZED BY A BUILDING UPPER RIDGE ACROSS THE MISSISSIPPI RIVER VALLEY WITH A CLOSED UPPER LOW OFF THE NORTHEAST COAST...LEAVING CENTRAL NC UNDER A NORTHWESTERLY UPPER FLOW REGIME. THERE ARE DIFFERENCES AMONG THE MODELS WITH RESPECT TO THE AMPLITUDE OF THE UPPER AIR PATTERN...ESPECIALLY BY THE WEEKEND. TO BEGIN ON WEDNESDAY...THE UPPER FLOW WILL BE MORE ZONAL IN NATURE AS THE UPPER RIDGE WILL JUST BE TAKING SHAPE OVER THE NORTHERN GULF WHILE A SHORTWAVE TROUGH WILL BE TRACKING ACROSS THE GREAT LAKES. MODELS DO INDICATE A SHEAR AXIS APPROACHING THE AREA LATE WEDNESDAY AFTERNOON AND THIS COULD RESULT IN SOME CONVECTION. HOWEVER...PER FORECAST SOUNDINGS...DEEP MOISTURE WILL BE LACKING (PWAT VALUES 1.5- 1.75 INCHES...HIGHEST ACROSS THE EAST) AND THEREFORE CONVECTIVE COVERAGE IS NOT ANTICIPATED TO BE THAT GREAT. SIMILAR SET UP ON THURSDAY ALTHOUGH THE NORTHWESTERLY FLOW ALOFT WILL BEGIN TO SET UP OVER THE REGION AND THE REGION WILL BE UNDER THE INFLUENCE OF ANY POSSIBLE DISTURBANCES WITHIN THE UPPER FLOW. HOWEVER...WITH RELATIVELY LIMITED DEEP MOISTURE...WILL KEEP POPS CAPPED AT CHANCE. STILL UNDER THE INFLUENCE OF DISTURBANCES ALOFT WITHIN THE NORTHWESTERLY FLOW...WILL SHOW A GRADUAL INCREASE IN POPS BY FRIDAY AND INTO THE WEEKEND AS MOISTURE SURGES BACK INTO THE REGION (PWAT VALUES PROGGED TO EXCEED 2 INCHES). AS STATED ABOVE...MODEL DIFFERENCES BECOME MORE APPARENT OVER THE WEEKEND...WITH THE GFS PERSISTING WITH A VERY AMPLIFIED UPPER PATTERN AND THE ECMWF BEGINNING THE BREAK DOWN THE RIDGE OVER THE MISSISSIPPI VALLEY. REGARDLESS...WITH A VERY MOIST AND UNSTABLE AIR MASS...WILL KEEP PRECIP CHANCES IN THE FORECAST (MAINLY DIURNAL IN NATURE). TEMPS ON WEDNESDAY AND THURSDAY ARE EXPECTED TO BE IN THE LOW TO MID 90S...WITH SLIGHTLY "COOLER" TEMPS FOR THE REMAINDER OF THE PERIOD GIVEN THE INCREASED CLOUDS AND PRECIP CHANCES...WITH MAINLY 80S EXPECTED BY THE WEEKEND. OVERNIGHT LOWS WILL GENERALLY IN THE UPPER 60S TO LOWER 70S THROUGHOUT THE PERIOD. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... AS OF 1115 AM MONDAY... 24-HR TAF PERIOD: PERIODS OF MVFR CEILINGS AND VISBYS ASSOCIATED WITH SHOWERS AND THUNDERSTORMS ARE EXPECTED AT MOST IF NOT ALL TERMINALS THROUGH THIS EVENING. WINDS WILL BE LIGHT/VARIABLE AT NORTHERN TERMINALS AND SOUTHWEST AT 5-10 KT AT SOUTHERN TERMINALS (FAY). A PERIOD OF SUB-VFR CEILINGS AND/OR FOG WILL BE POSSIBLE AT ALL TERMINALS EARLY TUE MORNING (08-13Z)...WITH THE BEST CHANCE IN AREAS THAT RECEIVE RAINFALL THIS AFT/EVE...THOUGH CONFIDENCE REMAINS TOO LOW TO INCLUDE MENTION THEREOF WITH THE 18Z TAF ISSUANCE. LOOKING AHEAD: EXPECT A CLIMATOLOGICAL POTENTIAL FOR AFT/EVE SHOWERS AND STORMS THROUGH MID TO LATE WEEK...ALONG WITH A POTENTIAL FOR FOG AND/OR LOW CEILINGS DURING THE EARLY MORNING HOURS. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...CBL LONG TERM...KRD AVIATION...VINCENT

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