Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 222355 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 750 PM EDT WED MAY 22 2013 .SYNOPSIS... A MOIST SOUTHERLY WIND FLOW WILL PERSIST ACROSS CENTRAL NC THROUGH THURSDAY. A COLD FRONT WILL CROSS THE REGION LATE THURSDAY AND THURSDAY NIGHT. A CANADIAN HIGH PRESSURE SYSTEM WILL BUILD INTO THE CAROLINAS FRIDAY AND LINGER OVERHEAD THROUGH THE HOLIDAY WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 300 PM WEDNESDAY... CENTRAL NC CONTINUES TO SIT BETWEEN SURFACE HIGH PRESSURE OFF THE COAST AND AN ADVANCING FRONTAL SYSTEM TO THE WEST. UPPER LEVEL RIDGING OVER THE AREA AND DECREASED MOISTURE HAS LED TO A QUIETER DAY TODAY AS FAR AS CONVECTION IS CONCERNED. AS OF 18Z THE CURRENT RADAR SHOWS AN AXIS OF CONVECTION POPPING UP ALONG THE SEA BREEZE FRONT WHICH IS CURRENTLY STILL EAST OF THE I-95 CORRIDOR. THIS WILL SLOWLY ADVECT NORTHEASTWARD BUT IS NOT EXPECTED TO PROPAGATE TOO FAR INLAND THIS AFTERNOON. OTHER WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE OVER THE NEXT COUPLE OF HOURS. SEVERE PARAMETERS REMAIN LOW AND SEVERE WEATHER IS NOT EXPECTED THIS AFTERNOON. WINDS REMAIN OUT OF THE SOUTH SOUTHWEST NEAR 10 KNOTS GUSTING TO 15-20 KNOTS. HIGHS WILL TOP OUT IN THE MIDDLE 80S THIS AFTERNOON. FOR TONIGHT SHOWERS AND THUNDERSTORMS WILL END AFTER 00Z AND LOW STRATUS IS ONCE AGAIN EXPECTED ACROSS THE CWA AS DEWPOINTS REMAIN ELEVATED INTO THE MID 60S. CEILINGS SHOULD BE AROUND 1000 FEET OVERNIGHT. LOW TEMPERATURES ARE EXPECTED TO BE IN THE LOW 60S. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 300 PM WEDNESDAY... A COLD FRONT WILL APPROACH CENTRAL NC FROM THE WEST ON FRIDAY. AS A DEEP 500 MB TROUGH DIGS SOUTHWARD THROUGH THE OHIO VALLEY. AS FAR AS TIMING IS CONCERNED...SHOWERS AND THUNDERSTORMS AHEAD OF FRONT WILL BEGIN TO AFFECT THE TRIAD BY LATE THURSDAY MORNING AND CONTINUE TO PROGRESS SLOWLY EASTWARD ACROSS THE CWA BY AFTERNOON/EVENING. SEVERE POTENTIAL WITH THIS SYSTEM WILL BE GREATER THAN THE PAST COUPLE OF DAYS BUT STILL LOOKS VERY LOW. EFFECTIVE SHEAR WILL BE ABOUT 20 KNOTS SUGGESTING MORE LINEAR THUNDERSTORMS. THIS IS SUPPORTED BY THE STRAIGHT HODOGRAPHS SHOWN BY NAM FORECAST SOUNDINGS. MID LEVEL LAPSE RATES WILL BE WEEK ALTHOUGH 1000 ML CAPE OF THE TALL AND SKINNY VARIETY COULD BE REALIZED BY AFTERNOON. LATER IN THE EVENT DYNAMICS IMPROVE AS A 30 KNOT 850MB APPROACHES THE NORTHWEST. IT IS UNCLEAR AT THIS TIME WHETHER OR NOT CONVECTION WILL BE TOO FAR TO THE EAST TO TAKE ADVANTAGE OF THE INCREASED SHEAR. STORMS LINGERING BACK TOWARDS THE WEST MAY BE ABLE TO TAKE ADVANTAGE OF AN INCREASED AXIS OF DCAPE EXPECTED TO MOVE THROUGH THE CWA JUST AFTER 00Z FRIDAY. THEREFORE IF WE DO ENCOUNTER SEVERE WEATHER TOMORROW...IT WILL MOST LIKELY BE DAMAGING WINDS AND NOT HAIL. FOR NOW SPC HAS KEPT THE RALEIGH AREA OUT OF THE SLIGHT RISK AREA FOR TOMORROW. PRECIPITABLE WATERS WILL BE SIMILAR TO TODAY NEAR 1.5 INCHES BUT QPF WITH FRONTAL PASSAGE IS ONLY EXPECTED TO BE BETWEEN A QUARTER AND A HALF OF AN INCH WITH LOCALLY HEAVIER AMOUNTS POSSIBLE IN THUNDERSTORMS. LOCALIZED FLOODING COULD BE AN ISSUE...ESPECIALLY IN URBAN AREAS UNDER SLOW MOVING OR TRAINING THUNDERSTORMS. CLOUD COVER SHOULD OVERSPREAD THE AREA FAIRLY EARLY TOMORROW AND THUS WILL TREND TOWARDS THE COOLER MET GUIDANCE WITH HIGH TEMPERATURES. UPPER 70S IN THE NORTHWEST TO LOW 80S SOUTHEAST. AS THE LOWER ATMOSPHERE BEGINS TO DRY OUT LOW TEMPERATURES IN THE TRIAD SHOULD DIP INTO THE UPPER 50S IN THE NORTHWEST FOR THE FIRST TIME IN SEVERAL DAYS BUT FURTHER TO THE SOUTHEAST LOWS WILL REMAIN IN THE MIDDLE 60S AS THE FRONT IS EXPECTED TO FULLY MOVE THROUGH THE EAST UNTIL CLOSER TO 6Z ON FRIDAY. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... AS OF 310 PM WEDNESDAY... FRIDAY THROUGH SATURDAY NIGHT... A DEEP UPPER LEVEL TROUGH WILL SWING ACROSS CENTRAL NC FRIDAY AND EXIT THE REGION FRIDAY NIGHT. MAY SEE A FEW INSTABILITY SHOWERS WITH THE PASSAGE OF THIS SYSTEM HOWEVER MODEL RH CROSS SECTIONS DEPICT THE AIR MASS DRYING OUT APPRECIABLY ABOVE 5000-8000FT BY EARLY AFTERNOON. FOR NOW WILL LIMIT POPS TO SLIGHT CHANCE. OTHERWISE BRISK NW FLOW WILL ADVECT COOLER MORE STABLE AIR INTO THE REGION. SUSTAINED NW WINDS 10-15 MPH WITH GUSTS AROUND 25 MPH PROBABLE. THE ARRIVAL OF THIS AIR MASS WILL RESULT IN COOLER CONDITIONS WITH AFTERNOON MAX TEMPS IN THE LOWER 70S NORTH TO UPPER 70S FAR SE. FRIDAY NIGHT...SKIES WILL CLEAR EARLY THOUGH A STEADY NW SFC WIND WILL BE SLOW TO SUBSIDE. LOW LEVEL THICKNESSES CLUSTERING AROUND 1340M. HISTORICALLY...THIS SUGGEST MIN TEMPS NEAR 40-LOWER 40S. FAVOR THE HIGH END OF THIS REGION DUE TO EXPECTED MIXING WELL INTO THE NIGHT. MIN TEMPS 45-50. SATURDAY INTO SATURDAY NIGHT...CANADIAN HIGH PRESSURE OVER THE LOWER GREAT LAKES WILL BUILD/EXTEND INTO OUR REGION SATURDAY INTO SATURDAY NIGHT. THIS WEATHER SYSTEM WILL RESULT IN A DRY WEATHER PATTERN WITH BELOW NORMAL TEMPS. AFTERNOON THICKNESSES PROJECTED TO BE ABOUT 35M BELOW NORMAL...SUPPORTIVE OF TEMPS CLOSE TO 10 DEGREES BELOW NORMAL. ALLOWING FOR WARMTH FROM LATE MAY SUN...EXPECT AFTERNOON HIGH TEMPS IN THE MID-UPPER 70S. MOS GUIDANCE LIKELY TRENDING TOWARD CLIMATOLOGY BY SATURDAY NIGHT. WITH SFC RIDGE OVERHEAD AND CORE OF LOW LEVEL DRY ACROSS THE REGION...TEMPS SHOULD COOL QUICKLY INT EH EVENING THEN STABILIZE. MODEL RH CROSS SECTIONS HINT AT INCREASING MID-HIGH LEVEL CLOUDS OVERNIGHT INTO EARLY SUNDAY. FIRST GLANCE SUGGEST THAT CLOUD COVERAGE MAY INITIALLY BE THIN AND SPOTTY SO COULD SEE DECENT NOCTURNAL COOLING. FAVOR MIN TEMPS A FEW DEGREES COOLER THAN PREVIOUS FORECAST WITH MIN TEMPS IN THE MID-UPPER 40S. SUNDAY INTO MONDAY...DEEP UPPER LEVEL LOW OVER NORTHERN NEW ENGLAND-CANADIAN MARITIME PROVINCES WILL MAINTAIN A NW FLOW OVER THE FORECAST AREA SUNDAY. WEAK PERTURBATIONS IN THIS FLOW ALOFT WORKING WITH AVAILABLE MOISTURE WILL LIKELY CAUSE AN INCREASE IN MID-HIGH LEVEL CLOUDINESS SUNDAY INTO SUNDAY NIGHT...MORE SO ACROSS OUR WEST AND SOUTH SECTIONS AND LEAST IN THE NE. A MODIFYING AIR MASS WILL LEAD TO SLIGHTLY WARMER CONDITIONS WITH AFTERNOON TEMPS IN THE MID-UPPER 70S...AND AND MIN TEMPS IN THE MID 50S. 00Z ECMWF SUGGEST THAT THERE MAY BE ENOUGH AMPLITUDE TO AN APPROACHING MID LEVEL TROUGH TO WARRANT A SLIGHT-SMALL CHANCE POP ACROSS CENTRAL NC MONDAY AFTERNOON-MONDAY EVENING. TUESDAY INTO WEDNESDAY...AN AMPLIFYING MID-UPPER LEVEL RIDGE OVER THE EASTERN HALF OF THE U.S. WILL PLACE CENTRAL NC BACK INTO A SUMMER-LIKE PATTERN WITH A SFC HIGH ANCHORED OFFSHORE BUT EXTENDING WESTWARD INTO THE SE U.S. THIS SUGGEST A RETURN TO WARM AND SLIGHTLY HUMID CONDITIONS WITH AFTERNOON TEMPS IN THE LOW-MID 80S AND MIN TEMPS 60-65. CONVECTION APPEARS TO BE DIURNALLY DRIVEN...ADDED BY A SEABREEZE TO SE AND NW FLOW ALOFT SENDING CONVECTION OFF THE HIGHER TERRAIN INTO THE WESTERN PIEDMONT. POPS NO HIGHER THAN SLIGHT CHANCE-SMALL CHANCE AT THIS TIME...CONFINED TO THE AFTERNOON-EVENING HOURS. && .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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AS OF 750 PM WEDNESDAY... SEABREEZE AND OUTFLOW GENERATED SHOWERS HAVE MOSTLY DISSIPATED IN THE LAST HOUR...WITH MORE ROBUST CONVECTION JUST TO THE WEST OF KINT CONTINUING TO MOVE SOUTHWEST TO NORTHEAST. THERE IS NOT MUCH EVIDENCE ON RADAR OF THESE CELLS MOVING EAST MAKING MUCH PROGRESS EAST TOWARD KINT...SO WILL KEEP VCSH IN THE KINT TAF THROUGH 03Z. THE MORE PROGRESSIVE AREA OF CONVECTION AND OUTFLOW IS STILL WEST OF KHKY. THE OVERALL WEAKENING TREND OF CONVECTION IS EXPECTED TO CONTINUE THIS EVENING...WITH IFR/MVFR STRATUS EXPECTED TO DEVELOP AFTER MIDNIGHT. THE THREAT OF SCATTERED CONVECTION WILL CONTINUE ON THURSDAY AHEAD OF AN UPPER LEVEL TROUGH AND ASSOCIATED COLD FRONT OVER THE MIDWEST STATES. MODEL GUIDANCE SUGGESTS SHOWERS MAY BE POSSIBLE AS EARLY AS 12Z NEAR KGSO/KINT...WITH MORE WIDESPREAD SHOWERS AND STORMS MORE LIKELY THURSDAY AFTERNOON AS THE TROUGH AND COLD FRONT APPROACH FROM THE WEST. CEILINGS WILL BREAK BY MIDDAY THURSDAY...WITH CLOUD BASED EXPECTED TO LIFT TO AROUND 3500-4000 FT THURSDAY AFTERNOON. OUTLOOK... A COLD FRONT MOVING THROUGH THE AREA LATE THURSDAY AND EARLY FRIDAY WILL CONTINUE THE THREAT OF ADVERSE AVIATION CONDITIONS. VFR CONDITIONS ARE EXPECTED TO RETURN DURING THE DAY FRIDAY AND PREVAIL THROUGH THE WEEKEND.
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&& .CLIMATE... MORNING LOW TEMPERATURES ON THE 25TH AND 26TH ARE EXPECTED TO BE A FEW DEGREES SHY OF RECORD MIN TEMPS FOR THE DATE. RECORD MIN TEMP/YEAR SET MAY 25TH MAY 26TH RDU 43 / 1967 43 / 1979 GSO 43 / 1956 42 / 1930 .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...ELLIS SHORT TERM...ELLIS LONG TERM...WSS AVIATION...SMITH CLIMATE...RAH

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