Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 131927 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 327 PM EDT SAT SEP 13 2014 .SYNOPSIS...A COLD FRONT WILL PUSH SOUTH THROUGH THE AREA TONIGHT...AS HIGH PRESSURE BUILDS INTO THE AREA FROM THE NORTH. THE FRONTAL ZONE WILL CONTINUE TO LINGER OVER THE REGION THROUGH MIDWEEK...LEADING TO CONTINUED UNSETTLED WEATHER. && .NEAR TERM /THROUGH SUNDAY/... AS OF 245 PM SATURDAY... ...FLASH FLOOD WATCH REMAINS IN EFFECT ACROSS THE SOUTHERN PIEDMONT... SANDHILLS... AND SE COASTAL PLAIN AS HEAVY RAIN REMAINS A CONCERN THROUGH EARLY SUNDAY... STRATUS...WHILE LIFTING A BIT...HAS HELD ON STRONG OVER THE NORTHERN HALF OF THE AREA. THE WEAK WARM FRONT THAT MOVED IN FROM THE SOUTH AND COLD FRONT FROM THE NORTHWEST HAVE ESSENTIALLY MERGED AND CREATED ONE AXIS OF CONVERGENCE STRETCHING FROM THE SOUTHERN PIEDMONT TO THE NORTHERN COASTAL PLAIN. ALONG AND SOUTH OF THIS BOUNDARY...SCATTERED SHOWERS AND STORMS ARE DEVELOPING IN AN AIRMASS CHARACTERIZED BY MLCAPE OF 500-1500 J/KG AND PW OVER 2 INCHES. WIND FIELDS ARE WEAK WELL SOUTH OF THE MAIN JET OVER THE OHIO VALLEY..SO THE MAIN IMPACTS TODAY WILL BE LOCALLY HEAVY RAINFALL FROM SLOW MOVING/TRAINING CELLS. DUE IN PART TO THE LIMITED HEATING ACROSS THE NORTH...HI-RES GUIDANCE HAS TRENDED SOUTH WITH THE MAIN AREA OF CONVECTION AND HEAVY RAIN POTENTIAL...WITH THE FOCUS NOW FROM THE ANSON COUNTY EAST TOWARD WAYNE/WILSON COUNTIES. GIVEN THESE MODEL TRENDS AND DEVELOPING NORTHWESTERLY FLOW BEHIND THE AFOREMENTIONED BOUNDARY...WE REMOVED DAVIDSON AND RANDOLPH COUNTIES FROM THE FLASH FLOOD WATCH EARLIER THIS AFTERNOON. CURRENTLY FEEL THE SWEET SPOT OF FLOODING POTENTIAL WILL BE ACROSS THE SANDHILLS AND SOUTHERN COASTAL PLAIN...BUT WILL LEAVE THE REMAINDER OF THE WATCH AS IS BASED ON CURRENT RADAR TRENDS ACROSS THE SOUTH. TONIGHT...HIGH PRESSURE WILL BUILD IN FROM THE NORTH AND PUSH THE COLD FRONT SOUTH OF OUR CWA. MODELS SHOW SOME WEAK ISENTROPIC LIFT ALONG THE FRONT AS IT MAKES ITS STRONGER PUSH TO THE SOUTH LATE TONIGHT...WHICH EXPANDS ACROSS THE WESTERN PIEDMONT BY SUNDAY MORNING. FROM THIS THERE MAY BE SOME PATCHY DRIZZLE DEVELOP AS LOWER STRATUS DEVELOPS. AT THE SAME TIME...MUCH DRIER ARI WILL BE FILTERING IN FROM THE NORTH...SO ANY DRIZZLE SHOULD STAY MOSTLY CONFINED TO SOUTHERN AREAS. LOWS IN THE LOW TO MID 60S. SUNDAY...NOT MUCH IN THE WAY OF FORCING FOR PRECIP AS THE MORNING ISENTROPIC UPGLIDE RELAXES AND WE ARE LEFT WITH JUST LOW CLOUDS THAT SHOULD LIFT A BIT DURING THE AFTERNOON. WILL MAINTAIN A SMALL CHANCE OF PRECIP ACROSS THE SOUTH...BUT TRENDS HAVE BEEN TOWARD LESS AND LESS POTENTIAL. HIGHS WILL BE MUCH COOLER WITH THE SURFACE RIDGE OVER THE AREA AND OVERCAST SKIES...BUT NO PRECIP EXPECTED...READINGS SHOULD BE ABLE TO REACH THE LOWER 70S NORTHWEST TO UPPER 70S SOUTHEAST. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... AS OF 300 PM SATURDAY... SUN NIGHT: WHILE THE LOW LEVEL FRONTAL ZONE AND ASSOCIATED TEMPERATURE GRADIENT WILL BECOME MORE DIFFUSE SUN NIGHT...THE MOIST AXIS ALONG THE FRONT WILL DRIFT NORTH WITH THE DEVELOPMENT OF VEERING AND ISENTROPIC UPGLIDE-INDUCING SE 925 MB FLOW. THESE PROCESSES IN CONJUNCTION WITH NOCTURNAL COOLING...WILL RESULT IN A NORTHWARD EXPANSION AND LOWERING OF STRATUS OVERNIGHT...WITH EXCEPTION OF OVER THE FAR NORTHERN PIEDMONT WHERE DRIER AIR WILL RESIDE IN THE LOW LEVELS AND ARRIVE ALOFT TOWARD DAYBREAK. AREAS OF FOG WILL CONSEQUENTLY BE POSSIBLE IN THESE POCKETS OF RELATIVE CLEARING EARLY MON MORNING. LOWS 57 TO 65...COOLEST OVER THE NORTHERN PIEDMONT. MON: LOW LEVEL STABILITY WILL CAUSE LOW CLOUDS TO BE SLOW TO LIFT AND ERODE MON...PARTICULARLY OVER THE SANDHILLS AND COASTAL PLAIN...WHERE NWP GUIDANCE INDICATES A RELATIVE MAXIMUM IN MOISTURE DEPTH AND ASSOCIATED CONTINUED CLOUDY (OR MOSTLY SO) CONDITIONS THROUGHOUT THE DAY. WITH THE EXPECTATION OF LINGERING CLOUDINESS...HIGH TEMPERATURES ARE APT HOLD WITHIN A FEW DEGREES EITHER SIDE OF 80...IN AN ATYPICAL DISTRIBUTION OF WARMEST NW AND COOLEST SE. DEEP MOISTURE WILL ALSO REMAIN RELATIVELY MAXIMIZED OVER THE SOUTHERN AND SOUTHEASTERN HALF OF THE CWFA...WHERE PROJECTED K- INDICES AND MLCAPE IN THE LOWER-MIDDLE 30S C AND 500 J/KG... RESPECTIVELY...WILL SUPPORT A CHANCE OF SHOWERS DURING THE AFTERNOON. MON NIGHT: A STRONG S/W TROUGH WILL CROSS THE OH VALLEY AND NORTHERN MIDDLE ATLANTIC STATES MON NIGHT...AND CONSEQUENTLY SWEEP AN AREA OF 20-30 METER MID LEVEL HEIGHT FALLS; A MID LEVEL MOIST AXIS; AND SFC COLD FRONT ACROSS CENTRAL NC OVERNIGHT. THE PASSAGE OF THESE FEATURES WILL SUPPORT A CHANCE OF SHOWERS...PARTICULARLY OVER THE NORTHERN PIEDMONT AND NORTHERN COASTAL PLAIN - IN AN AREA LEAST LIKELY TO HAVE BEEN EARLIER CONVECTIVELY OVERTURNED...AND IN CLOSEST PROXIMITY TO THE PASSING MID LEVEL TROUGH. LOWS MOSTLY IN THE MIDDLE TO UPPER 60S...GIVEN A RELATIVELY LATE PASSAGE OF THE COLD FRONT... AND TRAILING CAA. TUE: AFTER A LINGERING CHANCE OF A SHOWER OVER THE FAR SOUTHEAST CWFA EARLY TUE...CLEARING SKIES WILL SUPPORT TEMPERATURES WARMING INTO THE LOWER TO MIDDLE 80S. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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AS OF 325 PM SATURDAY... THE MEDIUM RANGE WILL BE CHARACTERIZED BY A SLOWLY PROGRESSIVE LONGWAVE PATTERN ACROSS THE CONUS...WHICH WILL INCLUDE A DEVELOPING/ DEEPENING TROUGH OVER THE EASTERN US. MEANWHILE AT THE SFC...A PAIR OF SFC HIGHS WILL BUILD SOUTH FROM CANADA AND RIDGE DOWN THE EAST COAST. THE RESULT WILL BE A RELATIVELY PROLONGED PERIOD OF EAST TO NORTHEAST LOW LEVEL FLOW AND ASSOCIATED BELOW NORMAL TEMPERATURES. THE DAYTIME TEMPERATURES WILL LIKELY BE FURTHER MUTED BY PERIODS OF BKN MULTI-LAYERED CLOUD COVER WHEN A COUPLE OF WAVES OF LOW PRESSURE MAY RIPPLE ALONG AN OFFSHORE FRONTAL ZONE AND SPREAD MOISTURE/CLOUDS INLAND...WITH RAIN CHANCES HOLDING ALONG COASTAL AREAS...THU-FRI.
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&& .AVIATION /18Z FRIDAY THROUGH THURSDAY/... AS OF 145 PM SATURDAY... LOW CEILINGS CONTINUE INTO THE AFTERNOON ACROSS MOST OF CENTRAL NC...THOUGH THERE ARE SOME SIGNS OF SCATTERING OVER THE SOUTHERN AND WESTERN PIEDMONT AS A COLD FRONT MOVES INTO THE AREA FROM THE WEST. HOWEVER... THERE IS STILL A LOT OF LOW-LEVEL MOISTURE AND AT LEAST MVFR CEILINGS MAY PERSIST WELL INTO THE EVENING. SCATTERED TO NUMEROUS SHOWERS AND STORMS ARE EXPECTED TO DEVELOP ALONG AND SOUTHEAST OF THE FRONTAL ZONE...WHICH IS MAINLY FROM KRDU TO KRWI/KFAY BETWEEN ROUGHLY 19Z AND 03Z. SOME OF THE STORMS MAY BE VERY HEAVY AND PRODUCE LIFR CONDITIONS AND A WIND GUSTS OF 20-30KT. TONIGHT...HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE NORTH AS THE FRONT AND MOST OF THE PRECIP PUSHES SOUTH OF THE AREA. FORECAST SOUNDINGS SHOW MOSTLY MVFR CEILINGS...BUT THERE MAY BE SOME IFR CEILINGS/VSBYS AND PATCHY LIGHT RAIN/DRIZZLE AROUND KFAY BEHIND THE FRONT. LOW CLOUDS WILL THEN LIKELY PERSIST WELL INTO THE DAY ON SUNDAY. OUTLOOK...LOW CLOUDS AND LIGHT RAIN AND/OR DRIZZLE WILL PERSIST ACROSS THE REGION THROUGH AT LEAST EARLY NEXT WEEK AS A PERIOD OF COLD AIR DAMMING COMMENCES. THE NEARLY STATIONARY FRONT SHOULD FINALLY SHIFT SOUTHEAST OF THE AREA LATE SUNDAY NIGHT INTO MONDAY...ALLOWING A GRADUAL RETURN TO BETTER AVIATION CONDITIONS. && .RAH WATCHES/WARNINGS/ADVISORIES... FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR NCZ042-043-073>078-083>086-088-089. && $$ SYNOPSIS...BLS NEAR TERM...BLS SHORT TERM...MWS LONG TERM...MWS AVIATION...KRD/BLS

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