Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 010640 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 240 AM EDT SUN MAY 1 2016 .SYNOPSIS...
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A WARM FRONT WILL RETREAT NORTH ACROSS THE MIDDLE ATLANTIC STATES TODAY...AHEAD OF SLOW-MOVING LOW PRESSURE THAT WILL CROSS THE OHIO VALLEY THROUGH TONIGHT. WARM SOUTHWESTERLY FLOW WILL RESULT THROUGH EARLY THIS WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 1000 PM SATURDAY... LATEST SURFACE MAPS SHOWS A STATIONARY FRONTAL ZONE SNAKING FROM SW NC ACROSS THE NC/SC BORDER... DENOTED BY A GRADIENT IN THETA-E AND MLCAPE. SLOW-MOVING THUNDERSTORMS HAVE INCREASED IN COVERAGE OVER THE SW PIEDMONT THIS EVENING... FED BY STRENGTHENING MOISTURE TRANSPORT COUPLED WITH INCREASING UPPER DIVERGENCE... GENERATING TORRENTIAL RAINFALL AND SOME SMALL HAIL... WITH AREAS SOUTH AND WEST OF CLT SEEING THE WORST OF IT OVER THE LAST FEW HOURS. RAIN AND ISOLATED STORMS CONTINUE TO EXPAND OVER THE REST OF THE WRN PIEDMONT INCLUDING THE TRIAD... FOLLOWING THE TREND OF INCREASING MOISTURE AND IMPROVING DYNAMICS NEAR THE NORTHEAST-RETREATING FRONTAL ZONE... AND HAVE MAINTAINED (WITH MINOR CHANGES IN COVERAGE AND ORIENTATION) A TREND TOWARD HIGHER POPS ACROSS THE WRN THIRD OF THE CWA THROUGH THE REST OF THE NIGHT. WITH PW AND MOISTURE TRANSPORT EXPECTED TO SURGE FURTHER OVERNIGHT... AND WITH UPPER DIVERGENCE GROWING OVER WRN/CENTRAL NC AND STRENGTHENING 850 MB WINDS... WILL BEEF UP QPF THROUGH THE NIGHT AND SOME MODERATE RAINFALL IS POSSIBLE. INCREASING FLOW ALOFT SHOULD SPEED UP CELL MOVEMENT WHICH WOULD HELP LIMIT THE HEAVY RAIN THREAT... ALTHOUGH SOME TRAINING OF CELLS WILL STILL BE POSSIBLE... ELEVATING RAIN TOTALS LOCALLY. HAVE HELD ONTO LOWS IN THE MID 50S NE TO MID 60S SW. -GIH && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 320 PM SATURDAY... SFC WARM FRONT WILL LIFT NWD AND EXITING THE FAR NORTHERN COUNTIES OF CENTRAL NC EARLY SUNDAY. SWLY FLOW IN THE WAKE OF THIS BOUNDARY WILL ADVECT A WARM MOIST AIR MASS INTO CENTRAL NC. WHILE EXTENSIVE CLOUDINESS EXPECTED TO PREVAIL THROUGH EARLY AFTERNOON...ENOUGH BREAK MAY DEVELOP LATER IN THE DAY TO ALLOW THE LOWER HALF OF THE ATMOSPHERE TO DESTABILIZE ENOUGH TO SUPPORT THE DEVELOPMENT OF SCATTERED-NUMEROUS SHOWERS AND A FEW THUNDERSTORMS. A FEW STORMS MAY BE STRONG OR SEVERE AS BULK EFFECTIVE WIND SHEAR INCREASES LATE IN THE DAY TO 35-40KTS (AID TO ORGANIZE CELLS INTO BROKEN BANDS)...AND SBCAPE TOPS OUT AROUND 2000J/KG. MAIN SEVERE THREAT WILL BE MARGINALLY LARGE HAIL. BULK OF CONVECTION WILL DIMINISH AFTER 02Z THOUGH A SMALL CHANCE FOR SHOWERS WILL PERSIST INTO THE OVERNIGHT. MAX TEMPS SUNDAY AFTERNOON DEPENDENT UPON WHEN/IF BREAKS DEVELOP IN THE LOW OVERCAST AND DEVELOPMENT OF SCATTERED CONVECTION. SEE LITTLE REASON TO DEVIATE FROM PREVIOUS FORECAST OF MID/UPPER 70S NORTH HALF TO 80/LOWER 80S SOUTH. MN TEMPS SUNDAY NIGHT LOW-MID 60S. && .LONG TERM /MONDAY THROUGH SATURDAY/... AS OF 325 PM SATURDAY... UNSETTLED WEATHER IS EXPECTED MONDAY AND TUESDAY AS A FRONT SLOWLY MOVES ACROSS THE CAROLINAS AND STALLS JUST OFF THE COAST BY EARLY WEDNESDAY. THE BEST INSTABILITY AND THUS CHANCE FOR CONVECTION ON MONDAY APPEARS TO BE ACROSS THE EAST...THEN MORE CONFINED TOWARD THE COAST ON TUESDAY AFTER THE FRONT MOVES ACROSS THE I-95 CORRIDOR. A BREAK IN THE WEATHER APPEARS POSSIBLE ON WEDNESDAY IN A DRYING REGIME BEHIND THE AFOREMENTIONED FRONT...BUT ANOTHER FRONT WILL QUICKLY APPROACH ON THURSDAY AS A LARGE CLOSED MID-UPR LOW DROPS SOUTH ACROSS THE GREAT LAKES REGION...THUS WILL BRING RAIN CHANCES BACK DURING THAT TIME. FOR FRIDAY AND SATURDAY...DEEP NORTHERLY FLOW WILL SET UP OVER OUR AREA AS THE AFOREMENTIONED CLOSED LOW SLOWLY MEANDERS ALONG THE MID ATLANTIC COASTAL REGION. RIGHT NOW...GUIDANCE SUGGESTS TEMPS ONLY A FEW DEGREES BELOW NORMAL...BUT THIS MAY FEEL NOTABLY COOLER THAN USUAL FOR THIS TIME OF YEAR. ALSO WORTH NOTING THE H5 TEMPS CRASH EARLY FRIDAY AND REMAIN NOTABLY COOL THROUGH SATURDAY...SO RESULTING INSTABILITY COULD SUPPORT A FEW SHOWERS DURING THIS TIME...BUT NOTHING WIDESPREAD OR ORGANIZED IN COVERAGE. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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AS OF 215 AM SUNDAY... INCREASINGLY MOIST SW FLOW JUST ABOVE A RELATIVELY COOL AND STABLE LAYER OF AIR NEAR THE SURFACE WILL RESULT IN THE EXPANSION AND LOWERING OF IFR-MVFR CEILINGS THIS MORNING. A WARM FRONT WILL RETREAT NORTH ACROSS CENTRAL NC LATE THIS MORNING-MIDDAY AT FAY AND MIDDAY-EARLY AFTERNOON ELSEWHERE...WITH AN ASSOCIATED EROSION/ SCATTERING/LIFTING OF THE PRECEDING LOW CLOUDS...AND A SUBSEQUENT DEVELOPMENT OF A WARM AND BREEZY SW WIND. HOWEVER...THE EASTWARD PROGRESSION/PASSAGE OF AN AREA OF SHOWERS THROUGH THE SAME TIME FRAME MAY TEMPORARILY SLOW THOSE PROCESSES AND THE CONSEQUENT RETURN TO VFR CONDITIONS. WHILE THE AIR MASS WILL CONSEQUENTLY DESTABILIZE AND BE RIPE FOR THE DEVELOPMENT OF SHOWERS AND STORMS LATER THIS AFTERNOON...THE ABSENCE OF ANY NOTABLE TRIGGER BOTH AT THE SURFACE AND ALOFT --ASIDE FROM LOW PREDICTABILITY MESOSCALE ONES SUCH AS DIFFERENTIAL HEATING ALONG THE RETREATING WARM FRONT-- SUGGEST ASSOCIATED FORECAST CONFIDENCE IS TOO LOW TO MAINTAIN A PROLONGED/SEVERAL HOUR PERIOD OF THUNDER TO ACCOUNT FOR SUCH OCCURRENCE AT A GIVEN POINT/TAF SITE. THE ATMOSPHERE WILL REMAIN MOIST AND CONDITIONALLY UNSTABLE THROUGH TONIGHT...SO A THREAT OF SHOWERS AND STORMS WILL CONTINUE THROUGH THE 24-HR TAF PERIOD...THOUGH STILL WITH LOW CONFIDENCE ON OCCURRENCE/LOCATION/TIMING GIVEN A CONTINUED ABSENCE OF ANY TRIGGERS APPARENT AT THIS TIME RANGE. OUTLOOK: A SERIES OF WAVES OF LOW PRESSURE WILL TRACK ALONG A STALLED FRONTAL ZONE ALONG THE MIDDLE ATLANTIC AND SOUTHEAST UNITED STATES COAST...WITH ASSOCIATED PERIODS OF RAIN AND SUB-VFR CONDITIONS OVER CENTRAL NC...LATE MON NIGHT THROUGH WED. A POLAR VORTEX WILL MEANWHILE MIGRATE FROM THE ARCTIC CIRCLE TO THE MIDDLE ATLANTIC STATES THROUGH THE END OF THE WEEK...WITH RESULTANT ENHANCED AFTERNOON CLOUDINESS AND SHOWERS/STORMS...AS DIURNAL HEATING OCCURS BENEATH VERY COLD TEMPERATURES ALOFT ATTENDING THE VORTEX.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...HARTFIELD SHORT TERM...WSS LONG TERM...RAH AVIATION...26

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