Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 251911 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 210 PM EST TUE NOV 25 2014 .SYNOPSIS...A STATIONARY FRONT WILL HOLD ALONG THE CAROLINA COAST TONIGHT THROUGH WEDNESDAY MORNING... AS LOW PRESSURE TRACKS NORTHEAST ALONG THE FRONT NEAR THE SOUTHEAST AND CAROLINA COAST. THIS LOW WILL MOVE NORTHEAST AWAY FROM THE AREA WEDNESDAY AFTERNOON. ANOTHER LOW PRESSURE CENTER WILL CROSS THE REGION FROM WEST TO EAST WEDNESDAY NIGHT INTO EARLY THURSDAY MORNING. THEN... HIGH PRESSURE WILL BUILD IN FROM THE WEST FROM THANKSGIVING AFTERNOON THROUGH THE HOLIDAY WEEKEND. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 120 PM TUESDAY... REST OF TODAY: LIGHT TO MDT RAIN CONTINUES TO FALL OVER OUR SE AND FAR SRN CWA EASTWARD THROUGH THE COASTAL AREA... FUELED BY HIGH PW VALUES (OVER 150% OF NORMAL) ALONG A TROPICAL-SOURCE MOISTURE PLUME... WEAK MID LEVEL DPVA... AND WAVES OF ENHANCED UPPER DIVERGENCE WITHIN THE RIGHT ENTRANCE REGION OF A STRONG (160+ KT) JET RUNNING FROM THE NRN GULF STATES TO THE ST LAWRENCE VALLEY. WHILE THE BACK (NW) EDGE OF THE STEADY RAIN WILL CONTINUE TO WAVER BACK AND FORTH ONE TO TWO ROWS OF COUNTIES... HI-RES NEAR TERM MODEL OUTPUT (INCLUDING THE WRF-NMM/ARW AND HRRR) SUPPORTS HIGH RAIN CHANCES CONTINUING OVER THE SOUTHEAST CWA (SE OF HIGHWAY 1) FOR THE REST OF THE AFTERNOON WITH MORE PATCHY OR SPORADIC LIGHT RAIN A BIT FURTHER INLAND... AND NEXT TO NOTHING OVER THE TRIAD. THE COLD FRONT... NOW POSITIONED FROM JUST EAST OF ROCKY MOUNT TO SANFORD TO JUST SE OF MONROE... CONTINUES TO PLOD ESE THROUGH CENTRAL/ERN NC... CHARACTERIZED BY A WIND SHIFT TO NW AND DROP IN DEWPOINTS. THIS FRONT WILL CONTINUE ITS SOUTHEASTWARD PROGRESS BEFORE SETTLING AT THE COAST BEFORE 00Z. TEMPS IN THE MID 50S TO LOW 60S WILL REMAIN STEADY OR FALL SLOWLY THROUGH SUNSET. FOR TONIGHT: THE LARGE SCALE MEAN TROUGH COVERING THE CENTRAL/ERN CONUS WILL KEEP THE WEATHER UNSETTLED. THE FRONTAL ZONE WILL HOLD OVER COASTAL CAROLINAS OVERNIGHT... AS SURFACE LOW PRESSURE FORMS OVER THE FAR NE GULF AND TRACKS NNE ACROSS NE FL AND ALONG THE SE COAST OVERNIGHT... TO A POSITION NEAR THE SRN NC COAST BY 12Z WED (THE GFS IS A TAD FASTER THAN THE NAM/ECMWF). A SECONDARY INVERTED TROUGH WILL EXTEND FROM THE DEVELOPING LOW THIS EVENING UP THROUGH WRN NC... AND THIS WILL HELP FOSTER RAINFALL DEVELOPMENT FARTHER WEST AND A BIT EARLIER THAN IT WOULD OTHERWISE WITH JUST A COASTAL LOW IN PLAY. WIDESPREAD RAIN IS EXPECTED TO SPREAD INTO SRN PARTS OF CENTRAL NC STARTING SOON AFTER SUNSET BEFORE SPREADING NORTHWARD OVER THE ENTIRE CWA... PERSISTING FROM MID EVENING THROUGH THE OVERNIGHT HOURS. THIS RAIN WILL BE INSTIGATED BY THIS TROUGH AND THE APPROACH OF THE LOW... IN CONJUNCTION WITH DEEP MOISTENING AND STRENGTHENING FORCING FOR ASCENT VIA DPVA (AS STRONG VORTICITY NEAR EL PASO DIVES THROUGH THE BASE OF THE MEAN TROUGH AND TOWARD THE SRN APPALACHIANS LATE TONIGHT)... STRONG HEIGHT FALLS (~150 M)... STRENGTHENING MOIST UPGLIDE (ESPECIALLY EAST HALF)... POTENTIAL BANDED PRECIP IN THE WEST... AND INTENSIFYING UPPER DIVERGENCE IN THE RIGHT ENTRANCE REGION OF A STRENGTHENING JET FROM THE GULF STATES TO THE CANADIAN MARITIMES. LATEST MODELS AND UPSTREAM PRECIP SUPPORT THE PREVIOUS TRENDS TOWARD CATEGORICAL PRECIP STARTING MID TO LATE EVENING... AND SEE NO REASON TO DEVIATE FROM THIS. LOW TEMPS ARE TOUGH AS DEWPOINTS HAVE YET TO FALL IN THE EAST (STILL IN LOW 60S) BUT HAVE SLIPPED INTO THE 30S IN THE NW CWA. WILL LEAN TOWARD STATISTICAL GUIDANCE WHICH SUPPORTS LOWS OF 39-48... CLOSE TO THE EARLIER FORECAST. SURFACE WINDS MAINLY FROM THE NORTH WILL STEADILY INCREASE TONIGHT AS THE LOW APPROACHES OUR COAST. -GIH
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&& .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
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AS OF 210 PM TUESDAY... FOR WEDNESDAY: AS THE ABOVE-NOTED FORCING FEATURES CONTINUE TO PROMPT DEEP AND RAPID ASCENT WHILE DEEP MOISTURE (PW FROM 1" WEST TO 1.5" EAST) REMAINS IN PLACE... WIDESPREAD RAIN WILL CONTINUE THROUGH WED MORNING. STORM TOTAL RAINFALL FROM TONIGHT THROUGH WED MORNING IS LIKELY TO RANGE FROM THREE-QUARTERS OF AN INCH TO AN INCH AND A QUARTER... WITH A FEW HIGHER TOTALS POSSIBLE IN THE FAR EASTERN COUNTIES (WHERE MOIST ISENTROPIC UPGLIDE WILL BE STRONGEST) AND IN THE FAR WEST BENEATH ANY BANDED PRECIP. MODELS AGREE ON PRECIP ENDING FROM SSW TO NNE FROM LATE WED MORNING THROUGH EARLY WED AFTERNOON... LIKELY EXITING THE NE CWA PRIOR TO 3 PM AS THE VORTICITY MAXIMUM SWINGS NE OVER CENTRAL NC. THE CHANCE OF A MIX WITH WET SNOW WED MORNING AS THE VORTICITY MAXIMUM PASSES OVERHEAD (POTENTIALLY CAUSING FOCUSED STRONGER LIFT THAT COULD FURTHER COOL THE LOW LEVELS) REMAINS PLAUSIBLE... BUT IS UNLIKELY TO BE WIDESPREAD OR GENERATE ANY IMPACT. THE GFS IS TOO WARM (ABOVE- FREEZING SURFACE-BASED LAYER DEPTH NEAR 2K FT) AND HAS BEEN TRENDING WARMER... AND WHILE THE NAM IS COOLER (WARM LAYER DEPTH LESS THAN 1000 FT)... THE SREF PTYPE PLUMES INDICATE VERY LOW CHANCES OF ANYTHING BUT RAIN. WILL CONTINUE WITH A PURELY LIQUID FORECAST AT THIS TIME... BUT WILL CLOSELY MONITOR TRENDS IN BOTH MODEL DATA AND UPSTREAM CONDITIONS. WE SHOULD HAVE A SHORT WINDOW OF PARTIAL SUNSHINE ESPECIALLY ACROSS THE SW WED... AND THIS WILL MAKE HIGH TEMPS A CHALLENGE... AS ANY INSOLATION WILL CAUSE INITIALLY CHILLY READINGS TO WARM UP QUICKLY. WILL STICK WITH HIGHS OF 45-51... WHICH IS IN LINE WITH THE LATEST GUIDANCE... HOWEVER THESE COULD BE TOO COOL IF WE GET APPRECIABLE SUNSHINE. FOR WED NIGHT: FOCUS THEN QUICKLY SHIFTS TO THE CLIPPER WAVE AND LOW NOW OVER WRN ND... POISED TO DIVE SOUTHEAST THEN TRACK EASTWARD ACROSS NC/VA LATE WED NIGHT. MODELS AGREE ON PRECIP SPREADING EASTWARD OVER NRN NC... MAINLY ALONG/NORTH OF HIGHWAY 64... FORCED BY STRONG DPVA WITH THE STRENGTHENING VORTICITY MAX... A SHOT OF MODEST UPPER DIVERGENCE... AND STEEP 850-500 MB LAPSE RATES ON THE ORDER OF 7.0 C/KM. WILL RETAIN GOOD CHANCE POPS IN THE NORTH (ESPECIALLY NEAR THE VA BORDER) STARTING MID-LATE EVENING... SPREADING POPS EASTWARD OVER THE NORTHERN THIRD OVERNIGHT... WITH LITTLE TO NO POPS ACROSS THE SOUTH. QPF SHOULD BE LIGHT... GIVEN THAT FORCING WILL BE ROOTED FAIRLY HIGH WITH MODEST PRECIP WATER... PLUS SREF PROBABILITIES OF MEASURABLE RAINFALL ARE RATHER SMALL AND CONFINED JUST TO THE NW AND FAR NORTH. THERMAL PROFILES WITH THIS ALSO SUGGEST JUST A CHILLY LIGHT RAIN... ALTHOUGH IF WE DO ACHIEVE SOME INSTABILITY AND FOCUSED ASCENT... WE COULD SEE A BRIEF MIX WITH WET SNOW NEAR THE VA STATE LINE. AGAIN... THE VERY LOW PROBABILITY PRECLUDES MENTIONING IT IN THE FORECAST AT THIS TIME... BUT WILL MONITOR TRENDS. LOWS IN THE MID 30S... CLOSE TO GUIDANCE AND THE PREVIOUS FORECAST LOWS. -GIH
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 310 AM TUESDAY... SURFACE HIGH PRESSURE WILL BUILD EASTWARD AND INTO THE AREA LATE WEEK... BEFORE SHIFTING TO THE SOUTH AND EAST OF CENTRAL NC BY THE WEEKEND. MID LEVEL HEIGHTS ARE FORECAST TO RISE BY LATE WEEK INTO THE WEEKEND... AS FLOW BECOMES MORE ZONAL ACROSS THE SOUTHERN HALF OF THE COUNTRY. MEANWHILE... A MID LEVEL RIDGE IS FORECAST TO BUILD NORTHWARD AND NUDGE INTO OUR AREA... WHICH WILL HELP TO KEEP ANY NORTHERN STREAM S/W ENERGY TO THE NORTH OF THE AREA NEAR THE U.S/CANADIAN BORDER. A TRAILING DRY COLD FRONT HOWEVER... IS EXPECTED TO APPROACH THE AREA BY LATE IN THE FORECAST PERIOD... IN BACKDOOR FASHION ON MONDAY. EXPECT TEMPS WILL BE BELOW NORMAL AND CHILLY UNTIL WE SEE A WARMING RETURN FLOW ON SATURDAY. THUS... EXPECT HIGHS IN THE 40S ON FRIDAY WITH LOWS FRIDAY AND SATURDAY MORNING IN THE 20S TO LOWER 30S. HIGHS FOR THE REMAINDER OF THE MEDIUM RANGE ARE EXPECTED TO BE IN THE 50S AND 60S WITH LOWS IN THE UPPER 30S TO 40S. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... AS OF 1200 PM TUESDAY... EXPECTED AVIATION CONDITIONS: POOR AT EASTERN TERMINALS... FAIR EARLY THEN BECOMING POOR TONIGHT AT WESTERN TERMINALS. PRIMARY AVIATION CONCERNS OVER THE NEXT 24 HRS: MVFR TO IFR CIGS PERSISTING AT FAY/RDU/RWI AND SPREADING FROM SE TO NW AFFECTING ALL CENTRAL NC TAF SITES STARTING 21Z-23Z AND PERSISTING OVERNIGHT. ALSO... MVFR/ IFR VSBYS IN RAIN ESPECIALLY RDU/RWI/FAY TONIGHT-WED... AND BRISK GUSTY SURFACE WINDS FROM NORTH TONIGHT 05Z-11Z AND FROM THE NW 11Z- 18Z WED AT ALL SITES. CONFIDENCE: MEDIUM THROUGH 00Z... THEN HIGH AFTER 00Z. A COLD FRONT PUSHING SLOWLY ESE THROUGH CENTRAL NC WILL SETTLE OVER COASTAL NC BY EVENING. LOW PRESSURE WILL FORM OVER NRN FL AND TRACK NE ALONG THE FRONT ALONG THE SE AND CAROLINA COAST TONIGHT THROUGH WED MORNING WHILE STRENGTHENING... THEN MOVE NORTH TOWARD NEW ENGLAND WED AFTERNOON. STEADY RAIN WITH VFR OR BRIEFLY MVFR VSBYS WILL PERSIST OVER AND NEAR FAY/RWI WITH MORE ON-AND-OFF RAIN AT RDU AND LITTLE TO NO RAIN AT INT/GSO THE REST OF THIS AFTERNOON. STEADY RAIN WITH MVFR TO IFR VSBYS WILL THEN OVERSPREAD CENTRAL NC SOUTH TO NORTH FROM LATER THIS AFTERNOON THROUGH TONIGHT. WINDS WILL START TO STRENGTHEN 04Z-06Z TONIGHT... RISING TO SUSTAINED 10-15 KTS FREQUENTLY GUSTING TO AROUND 20 KTS. LOOKING BEYOND 18Z WED... CIGS MAY BRIEFLY IMPROVE TO MVFR OR VFR 18Z-03Z... WITH DIMINISHING WINDS LIKELY. ANOTHER FAST-MOVING LOW PRESSURE SYSTEM MOVING IN FROM THE WEST WILL CROSS SRN VA AND NRN NC WED EVENING/NIGHT... BRINGING POTENTIAL IFR CIGS AND LIGHT PRECIP WED NIGHT THROUGH EARLY THU MORNING. VFR CONDITIONS EXPECTED TO RETURN AFTER 15Z THU... LASTING THROUGH SUN... AS HIGH PRESSURE BUILDS IN. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...HARTFIELD LONG TERM...BSD AVIATION...HARTFIELD

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