Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 252305 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 705 PM EDT MON MAY 25 2015 .SYNOPSIS...AN UPPER LEVEL RIDGE OVER THE REGION WILL SLOWLY SHIFT OFFSHORE THROUGH MID-WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 100 PM MONDAY... A PRONOUNCED SFC RIDGE EXTENDING INTO THE REGION FROM THE EAST WILL PERSIST THROUGH TONIGHT. SOUTHWEST FLOW ALOFT WILL BECOME ESTABLISHED OVER WESTERN PORTIONS OF THE CAROLINAS TONIGHT AS THE UPPER LEVEL RIDGE EXTENDING NORTHWARD INTO THE REGION SHIFTS SLOWLY EAST TO THE SOUTHEAST COAST. SOUTHERLY RETURN FLOW /AIRMASS DESTABILIZATION/ WILL BE CONFINED TO LOCATIONS ALONG/WEST OF THE MOUNTAINS THIS AFT/EVE. TONIGHT...INCREASING LOW-LEVEL MOISTURE /WARM ADVECTION/ AND AN INCREASING POTENTIAL FOR DPVA ATTENDANT SMALL AMPLITUDE WAVES IN NEWLY ESTABLISHED SW FLOW ALOFT MAY ALLOW ELEVATED SHOWERS TO DEVELOP OVER PORTIONS OF THE FOOTHILLS AND PERHAPS THE WESTERN PIEDMONT AFTER MIDNIGHT...THOUGH OVERALL CHANCES WILL BE HIGHEST ALONG/WEST OF I-77. EXPECT SLIGHTLY WARMER TEMPS THAN YESTERDAY WITH HIGHS IN THE MID 80S AND LOWS TONIGHT IN THE LOW TO MID 60S...WARMEST IN THE WESTERN PIEDMONT WHERE STRATUS IS EXPECTED TO DEVELOP AFTER MIDNIGHT. -VINCENT && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 200 PM MONDAY... ALTHOUGH THE PRONOUNCED UPPER LEVEL RIDGE WILL REMAIN ANCHORED JUST OFFSHORE THE SOUTHEAST COAST TUE/TUE NIGHT...THE RIDGE AXIS WILL SHIFT EASTWARD TO THE CAROLINA COAST...ESTABLISHING SW FLOW ALOFT/ SOUTHERLY RETURN FLOW OVER WESTERN NC/SC. INCREASING LOW-LEVEL MOISTURE WILL AID IN MARGINAL DIURNAL DESTABILIZATION AS FAR EAST AS THE HWY 1 CORRIDOR (ROUGHLY) TUE AFTERNOON...WITH MLCAPE VALUES RANGING FROM 500-1000 J/KG...HIGHEST IN THE WESTERN PIEDMONT. LITTLE OR NO LOW-LEVEL FORCING WILL BE PRESENT TUE AFTERNOON GIVEN THE PRONOUNCED SFC RIDGE AXIS EXTENDING INTO THE REGION FROM THE EAST. ALTHOUGH A SEABREEZE WILL LIKELY MARCH INLAND INTO EAST/SE PORTIONS OF CENTRAL NC...THERMODYNAMIC PROFILES IN THE SANDHILLS/COASTAL PLAIN WILL REMAIN SUBSIDENT AND UNSUPPORTIVE OF CONVECTION. ASIDE FROM THE POTENTIAL FOR WEAK/GLANCING DPVA ATTENDANT SMALL AMPLITUDE DISTURBANCES EMBEDDED WITHIN SW FLOW ALOFT ACROSS FAR WESTERN PORTIONS OF THE STATE...FORCING APPEARS NEGLIGIBLE IN CENTRAL NC. WILL INDICATE A SLIGHT CHANCE OF SHOWERS IN THE FAR WESTERN PIEDMONT LATE TUE AFTERNOON TO ACCOUNT FOR ISOLD MOUNTAIN CONVECTION PROPAGATING INTO THE WEST/SW PIEDMONT...THOUGH SOUTHWESTERLY FLOW ALOFT IS NOT PARTICULARLY CONDUCIVE THEREOF...NOT TO MENTION THE INCREASINGLY UNFAVORABLE THERMODYNAMIC ENVIRONMENT WITH EASTWARD EXTENT. WILL CONTINUE TO INDICATE A SLIGHT CHANCE OF SHOWERS IN THE FAR WESTERN PIEDMONT TUE NIGHT GIVEN CONTINUED MOISTENING AND A POTENTIAL FOR SMALL AMPLITUDE WAVES IN SW FLOW ALOFT...OR PERHAPS IN ASSOC/W UPSTREAM CONVECTION PROGRESSING INTO THE MOUNTAINS...THOUGH ANY SUCH ACTIVITY WOULD LIKELY DISSIPATE EAST OF THE BLUE RIDGE. EXPECT HIGHS TUE SIMILAR TO TODAY...WITH LOWS TUE NIGHT A FEW DEGREES WARMER IN THE MID TO UPPER 60S. -VINCENT && .LONG TERM /WEDNESDAY THROUGH MONDAY/... AS OF 245 PM MONDAY... WEDNESDAY THROUGH FRIDAY...ONGOING MID RANGE FORECAST STILL LOOKS ON TRACK WITH THE AMPLIFIED UPPER LEVEL RIDGE HOLDING TIGHT ALONG THE EAST COAST. ECMWF AND GFS LOOK SIMILAR FOR MID-LATE WEEK...WITH THE RIDGING HAMPERING THE EASTWARD PROGRESSION OF AN APPROACHING SHORT WAVE AND ITS ASSOCIATED FRONTAL SYSTEM AND PRECIPITATION. THE DEEP RETURN FLOW AROUND THE STACKED RIDGING WILL RESULT IN INCREASED MOISTURE (PW`S >1.5 INCHES = CAPE >1K JOULES)...ESPECIALLY IN THE WEST...WHERE POPS WILL BE HIGHER DUE TO PROXIMITY OF THE STALLED FRONT AND ALSO AN INCREASED CHANCE FOR NON-DIURNAL ACTIVITY DUE TO THE POTENTIAL FOR PERTURBATIONS FROM UPSTREAM CONVECTION TO RIDE THE PREVAILING FLOW NORTHWARD ALONG THE FRONT. WILL MAINTAIN CHANCE POPS AT THIS POINT...FALLING OFF A BIT OVERNIGHT MAINLY IN THE EAST WITH LOSS OF INSOLATION. NO CHANGES ARE NEEDED IN THE TEMPERATURE FORECAST AS GUIDANCE CONTINUES TO TARGET HIGHS IN THE MID 80S WITH LOWS IN THE MID 60S. FRIDAY NIGHT THROUGH MONDAY...THE UPPER RIDGE REASSERTS ITSELF BY THE WEEKEND AS THE SHORT WAVE WHICH WAS INITIALLY BLOCKED BY THE RIDGING LIFTS NORTH OF THE AREA. THIS WILL ALLOW THE UPPER RIDGE TO RETROGRADE BACK ACROSS THE AREA AND SUPPRESS THE DEEPER MOISTURE PLUME WEST OF THE AREA. THE SUBSIDENCE=STRONGER CAPPING ALOFT WHICH WILL INHIBIT CONVECTION...AND ALSO NUDGE HIGH TEMPERATURES INTO THE UPPER 80S TO LOWER 90S SUNDAY AND MONDAY. WILL KEEP POPS IN THE LOW CHANCE RANGE AND SKEWED TOWARDS MAX HEATING DUE TO THE ABSENCE OF OTHER READILY IDENTIFIABLE LIFTING MECHANISMS TO ENHANCE ORGANIZATION OR NON-DIURNAL DISTRIBUTION. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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AS OF 705 PM MONDAY... AN AREA OF HIGH PRESSURE AT THE SURFACE AND ALOFT WILL SLOWLY DRIFT EAST TONIGHT THROUGH TUESDAY NIGHT. THE RETURN FLOW ON THE BACK SIDE OF THE HIGH WILL BEGIN TO INCREASE LOW LEVEL MOISTURE OVER CENTRAL NC. THIS WILL BECOME EVIDENT AFTER 06Z AS A LAYER OF STRATUS DEVELOPS OR MOVES INTO THE PIEDMONT COUNTIES...ESPECIALLY THE WESTERN PIEDMONT AND IN VICINITY OF THE TRIAD TERMINALS. CEILINGS IN THE IFR OR LOW END MVFR IS EXPECTED WITH POCKETS OF LIFR CEILINGS POSSIBLE. THE LOW CEILINGS WILL PERSIST THROUGH THE MID MORNING HOURS...LIFTING INTO THE LOW END OF THE VFR CATEGORY AROUND EARLY AFTERNOON. ELSEWHERE...SUCH AS THE SANDHILLS AND COASTAL PLAIN...THE STRATUS IS EXPECTED TO REMAIN FEW TO SCATTERED. IN VICINITY OF KRDU...A PERIOD OF SCATTERED TO BROKEN STRATUS BETWEEN 700-1200FT MAY OCCUR AROUND DAYBREAK THEN DISSIPATE BY MID-LATE MORNING. SFC WINDS TONIGHT INTO TUESDAY ARE EXPECTED TO REMAIN SLY AT LESS THAN 10 KTS. A SHOWER OR THUNDERSTORM MAY THREATEN THE TRIAD TERMINALS LATE TUESDAY AFTERNOON THROUGH TUESDAY EVENING BUT THIS PROBABILITY APPEARS TOO LOW TO MENTION IN THE TERMINAL FORECAST AT THIS TIME. WIDESPREAD MVFR/IFR CEILINGS EXPECTED EACH MORNING THROUGH THE REMAINDER OF THE WORK WEEK AS SLY FLOW CONTINUES TO INCREASE OR MAINTAIN LOW LEVEL MOISTURE OVER CENTRAL NC. THERE WILL BE A BETTER CHANCE FOR AFTERNOON CONVECTION BOTH WEDNESDAY AND THURSDAY WITH THE GREATEST CHANCES ON WEDNESDAY OVER THE PIEDMONT...AND AREAWIDE THURSDAY. THE HIGH PRESSURE SYSTEM WILL BEGIN TO BUILD BACK INTO THE CAROLINAS FRIDAY INTO SATURDAY. THIS WILL BEGIN TO LIMIT THE CHANCES FOR AFTERNOON CONVECTION ON FRIDAY AND MORE SO SATURDAY. THERE WILL CONTINUE TO BE DECENT THREAT FOR EARLY MORNING MVFR/IFR CEILING AND FOG FRIDAY AND SATURDAY MORNINGS.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...MLM AVIATION...WSS

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