Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 181820 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 220 PM 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 MONDAY/... AS OF 220 PM MONDAY... THE MAJOR PROBLEM THROUGH THE LONG TERM PERIOD WILL BE DISCERNING WHEN AND WHERE A HIGHER PROBABILTY OF PRECIPITATION WILL OCCUR. THERE IS GOOD MODEL CONSENSUS AS TO THE TRANSITION TO A LARGER SCALE BLOCKING PATTERN OVER THE EASTERN CONUS THROUGH THE WEEKEND. THE GRADUAL MIGRATION OF AN UPPER LOW ACROSS THE GREAT LAKES AND OFF THE MID ATLANTIC COAST WEDNESDAY THROUGH FRIDAY WILL AMPLIFY INTO A DEEPER UPPER TROF DOWN THE COAST INTO EARLY NEXT WEEK. CONCURRENT AMPLIFICATION OF AN UPPER RIDGE WEST OF THE AREA WILL PRODUCE PERSISTENT NORTHWEST FLOW WHICH WILL PRESENT THE USUAL PROBLEMS WITH TIMING FEATURES THAT WILL BE STEERED INTO THE AREA. AIRMASS WILL BE REASONABLY WARM (UPPER 80S TO LOW 90S) AND MOIST...PW ~1.5 INCHES... BUT MOISTURE ADVECTION WILL BE HAMPERED BY WESTERLY FLOW ACROSS THE DEEP SOUTH...SO CHANCES OF RAIN WILL BE IN THE CLIMATOLOGICAL RANGE...30 PERCENT-ISH...WEDNESDAY THROUGH FRIDAY. A COOL SURGE WILL PROGRESS SOUTH AND ACROSS THE AREA FRIDAY NIGHT AS HIGH PRESSURE OVER FAR EASTERN CANADA IS SHUNTED DOWN THE EASTERN SLOPES OF APPALACHIANS. THIS WILL ENHANCE A COASTAL TROF IN PLACE OFFSHORE AND RESULT IN DEEP NORTH TO NORTHEAST FLOW FLOW WITH ACCOMPANYING MOIST AND COOLER MARINE-FLAVORED AIRMASS PERSISTING THROUGH MONDAY. ISENTROPIC LIFT WILL BE MINIMAL...AND MID LEVEL FEATURES IN THE NORTHWEST FLOW WILL BE NIL-CONFIDENCE THIS FAR IN ADVANCE. WOULD EXPECT PATCHY LIGHT RAIN/SHOWERS TO BE THE PREDOMINANT TYPE OF PRECIP...WITH POTENTIAL FOR CONVECTION HINGING ON UPSTREAM FEATURES WE MIGHT SEE 24-48 HOURS IN ADVANCE. THICKNESSES WOULD INDICATE A 3-5 DEGREE COOL DOWN FOR SATURDAY...AND ANOTHER 1-2 DEGREES SUNDAY AND MONDAY. THIS WOULD KEEP US IN THE MID TO UPPER 80S EACH DAY...WHICH IS MORE LIKELY TO ERR ON THE HIGH SIDE GIVEN THE LOOK OF THE PATTERN AND POTENTIAL FOR SOCKING IN SOME SATURATED MARINE LAYER AIR OVERNIGHT WITH ACCOMPANYING DENSE FOG/LOW STRATUS TO START THE DAYS. && .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...VINCENT LONG TERM...MLM AVIATION...VINCENT

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