Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 260807 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 306 AM EST WED NOV 26 2014 .SYNOPSIS...A STRONG LOW PRESSURE SYSTEM WILL TRACK ALONG THE NC COAST THIS MORNING THEN LIFT NORTHEAST AWAY FROM OUR AREA THIS AFTERNOON. A STRONG UPPER LEVEL DISTURBANCE WILL QUICKLY TRACK ACROSS THE REGION LATE TONIGHT AND EARLY THURSDAY. HIGH PRESSURE WILL BUILD INTO THE CAROLINAS FRIDAY AND LINGER OVER THE REGION THROUGH THE REMAINDER OF THE HOLIDAY WEEKEND. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 846 PM TUESDAY... RAIN CONTINUES TO OVERSPREAD NC THIS EVENING IN RESPONSE TO THE BACKING LOW TO MID LEVEL FLOW ASSOCIATED WITH APPROACH OF SEVERAL WAVES IN THE STRONG SUBTROPICAL JET ALOFT. THE MAIN SURFACE LOW PRESSURE WAS DEVELOPING NW OF TAMPA FLORIDA... IN THE NE GULF OF MEXICO. THIS LOW IS EXPECTED TO STRENGTHEN AND TRACK NE ALONG THE MAIN COASTAL BOUNDARY TONIGHT... REACHING OFF THE NC COAST WEDNESDAY. WAA PRECIPITATION WILL CONTINUE TO OVERSPREAD OUR REGION AS THE ATLANTIC GETS TAPPED IN ADDITION TO THE GULF OF MEXICO OVERNIGHT. WITH THE LACK OF A COLD HIGH TO SUPPLY INITIAL OR INCOMING COLD AIR - ONLY THE HIGHER PEAKS OF THE BLUE RIDGE SHOULD GET ANY APPRECIABLE SNOW ACCUMULATIONS. RAIN IS EXPECTED THROUGHOUT OUR REGION... EVEN IN OUR FAR NW PIEDMONT TRIAD AS THE THERMAL PROFILE IS FORECAST TO REMAIN WARM ENOUGH FOR ALL RAIN THROUGH THE NIGHT AND THE END OF THE EVENT NOONISH WEDNESDAY (AIDED BY THE WARM BOUNDARY LAYER FORECAST EVEN WITH ADEQUATE COOLING ALOFT NEAR THE END OF THE MAIN PRECIPITATION). NOTE THIS EVENING THAT IS WAS STILL IN THE 50S IN WASHINGTON DC AS OF 800 PM... AND THE DEW POINTS WERE CLOSE TO 40. THIS CLEARLY SHOWS THE LACK OF COLD DRY AIR FOR THE SYSTEM TO WORK WITH AND BRINGS CONFIDENCE TO A HIGH LEVEL FOR THE PRECIPITATION TYPE TO BE RAIN FOR OUR REGION. ONE OF THE STRONGEST SIGNALS FOR ALL RAIN WAS THE SURFACE WET BULBS FORECASTS THROUGH THE END OF THE MAIN PRECIPITATION EVENT IN OUR NW ZONES ON WEDNESDAY ONLY DIP TO SLIGHTLY BELOW 40... SUGGESTING LITTLE IF ANY CHANCE OF A MIX OR CHANGE TO WET SNOW BEFORE ENDING EAST OF THE BLUE RIDGE... EVEN WITH RAPIDLY COOLING ALOFT. HIGH CONFIDENCE IN ALL RAIN FOR THIS EVENT. SOME OF THE LATEST GUIDANCE SUGGESTS 1 INCH OR MORE QPF WIDESPREAD ACROSS THE REGION. RUNOFF PROBLEMS ARE NOT EXPECTED DUE TO THE RECENT 30-60 DAY DRY PERIOD. 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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&& .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
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AS OF 230 AM WEDNESDAY... THE L/W TROUGH AXIS WILL PUSH TO THE EAST OF CENTRAL NC LATE WEEK... WHILE HIGH PRESSURE AT THE SURFACE BUILDS INTO THE AREA. THIS WILL YIELD A RETURN TO QUITE WEATHER WITH BELOW NORMAL TEMPERATURES. HOWEVER... A FEW WEAK DISTURBANCES ALOFT IN THE WEST-NORTHWESTERLY MID LEVEL FLOW MAY BRING SOME MID TO HIGH CLOUDS TO THE AREA BY FRIDAY NIGHT... PROBABLY PARTLY CLOUDY AT WORST THOUGH. LOWS FRIDAY MORNING... DRIVEN BY CAA... ARE EXPECTED TO GENERALLY BE IN THE MID TO UPPER 20S AS LOW LEVEL THICKNESS VALUES ARE EXPECTED TO PLUMMET TO AROUND 1280 METERS ACROSS THE NORTHWEST PIEDMONT. SIMILAR LOW LEVEL THICKNESS VALUES HAVE YIELDED LOW TEMPS GENERALLY IN THE 20-27 DEGREE RANGE IN THE PAST AT KGSO. THUS... HAVE TRENDED LOW TEMPS TOWARD THE COOL SIDE OF GUIDANCE... WHICH IS THE MAV. AFTERNOON LOW LEVEL THICKNESS VALUES ARE ONLY EXPECTED TO RECOVER TO AROUND 1300 METERS FOR FRIDAY AFTERNOON. THUS... WITH LOW LEVEL THICKNESS VALUES SOME 40 METERS BELOW NORMAL FOR THIS TIME OF YEAR... WILL LOWER HIGH TEMPS SOME... A BIT BELOW STATISTICAL GUIDANCE. EXPECT HIGH TEMPS ON FRIDAY WILL GENERALLY BE IN THE MID TO UPPER 40S. HIGH PRESSURE WILL SETTLE OVER THE REGION BY FRIDAY EVENING INTO FRIDAY NIGHT. THIS WILL YIELD LIGHT AND VARIABLE TO CALM WINDS. EVEN WITH SOME MID TO HIGH CLOUDS CROSSING THE AREA FROM TIME TO TIME... STILL THINK WE WILL SEE LOWS TEMPS FALL INTO THE MID TO UPPER 20S AGAIN.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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AS OF 255 AM WEDNESDAY... HIGH PRESSURE WILL SHIFT TO THE SOUTH AND EAST OF CENTRAL NC THIS WEEKEND ALLOWING FOR A WARMING TREND. HIGH TEMPS ARE EXPECTED TO BE IN THE 50S FOR SATURDAY AND 60S FOR SUNDAY. MID LEVEL RIDGING IS FORECAST TO BUILD NORTHWARD DURING THIS TIME FRAME AND NUDGE INTO OUR AREA. HOWEVER... AS A NORTHERN STEAM TROUGH IS FORECAST TO TRACK NEAR THE U.S./CANADIAN (EAST COAST THAT IS) BORDER DURING THIS TIME FRAME A TRAILING COLD FRONT WILL DROP SOUTHWARD AND POSSIBLY INTO CENTRAL NC BY EARLY NEXT WEEK. WITH THE MID LEVEL FLOW ONLY WSW IN ADVANCE OF THIS FEATURE (THANKS TO THE MID LEVEL RIDGE TO THE S/SE OF THE AREA) THIS SYSTEM WILL NOT HAVE THAT MUCH MOISTURE TO WORK WITH. COMBINE THAT WITH THE FROT DROPPING GENERALLY SOUTHWARD AND INTO THE AREA... WILL KEEP PRECIP CHANCES ONLY IN THE SLIGHT CHANCE CATEGORY. HIGH TEMPS EARLY NEXT WEEK WILL DEPEND ON THE TIMING OF THE FRONT. FOR NOW... WILL KEEP MONDAY MILD IN THE 60S TO AROUND 70... WITH HIGHS ON TUESDAY IN THE 50S TO NEAR 60 SOUTH. HOWEVER... SOME OF THE RAW MODEL GUIDANCES SHOWS HIGH TEMPS STRUGGLING TO GET OUT OF THE 40S ON TUESDAY NOW... AS THE SURFACE HIGH BUILDING INTO THE AREA FROM THE NORTH IS FORECAST TO BE QUITE STRONG... AROUND 1040-1045 MB. LOWS DURING THE PERIOD ARE GENERALLY EXPECTED TO BE IN THE 40S.
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&& .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 1258 AM WEDNESDAY... ADVERSE AVIATION WEATHER CONDITIONS WILL OCCUR ACROSS CENTRAL NC OVERNIGHT INTO THE FIRST HALF OF WEDNESDAY AS A STRONG LOW PRESSURE SYSTEM TRACKS ALONG THE NC COAST. WIDESPREAD IFR/LOW END MVFR CEILINGS WILL OCCUR WITH POCKETS OF LIFR CEILINGS. WIDESPREAD RAIN WILL RESULT IN MVFR VISIBILITY WITH AREAS OF IFR VISIBILITY IN HEAVIER SHOWERS. SFC WINDS WILL BECOME BLUSTERY PRIOR TO DAYBREAK WITH SUSTAINED NLY WINDS 10-18 MPH WITH GUST 30-35 MPH...ESPECIALLY AT KFAY AND KRWI. AS THE LOW PULLS AWAY FROM THE NC COAST THIS AFTERNOON...AVIATION CONDITIONS WILL BEGIN TO IMPROVE FROM THE SW AFTER 18Z. SFC WINDS WILL GRADUALLY SUBSIDE AND BACK TO A W-NW DIRECTION WHILE CEILINGS WILL LIFT INTO THE VFR CATEGORY AND THE PRECIP TAPERS OFF. A QUICK MOVING UPPER LEVEL DISTURBANCE WILL CROSS OUR NORTHERN COUNTIES LATE TONIGHT THROUGH EARLY THURSDAY MORNING...CAUSING A PERIOD OF MVFR/LOW VFR CEILINGS AND SPOTTY LIGHT RAIN. HIGH PRESSURE WILL BUILD INTO CENTRAL NC THURSDAY AFTERNOON...INITIATING A PERIOD OF VFR CONDITIONS WHICH SHOULD PERSIST THROUGH THE REMAINDER OF THE HOLIDAY WEEKEND. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...PWBADGETT/HARTFIELD SHORT TERM...BSD LONG TERM...BSD AVIATION...WSS

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