Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
623 FXUS62 KRAH 180820 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 419 AM EDT MON MAY 18 2015 .SYNOPSIS...A SURFACE TROUGH WILL STRENGTHEN ACROSS THE PIEDMONT OF VA AND THE CAROLINAS THROUGH TUESDAY. SUB-TROPICAL HIGH PRESSURE WILL OTHERWISE REMAIN OVER THE SOUTHEASTERN U.S. UNTIL A COLD FRONT CROSSES OUR REGION TUESDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 400 AM MONDAY... ON THE NORTHERN PERIPHERY OF A SUB-TROPICAL RIDGE CENTERED AT 700 MB OVER THE SAVANNAH BASIN...A SERIES OF IMPULSES ALOFT WILL DRIFT ACROSS NC THROUGH THIS EVENING. THE MOST NOTABLE IMPULSE WAS EVIDENT IN WV IMAGERY THIS MORNING DRIFTING SSE FROM NEAR THE POTOMAC RIVER...WHILE A WEAKER ONE PRECEDED IT AND HAS SUPPORTED THE RECENT OCCURRENCE THIS MORNING OF VERY LIGHT SHOWERS/SPRINKLES OVER THE NORTHERN NC PIEDMONT. THESE DISTURBANCES ARE FORECAST TO DRIFT INTO AND SHEAR OUT OVER CENTRAL NC THROUGH 00Z. YET ANOTHER IMPULSE WAS LOCATED OVER EASTERN TN...ON THE WEST SIDE OF THE SUB-TROPICAL RIDGE AXIS...AND THE MODELS INDICATE THIS FEATURE WILL DRIFT SLOWLY EAST ACROSS THE APPALACHIANS TODAY AND INTO CENTRAL NC BETWEEN 00-06Z. THE APPROACH AND PRESENCE OF THESE ALBEIT RELATIVELY WEAK DISTURBANCES...IN CONJUNCTION WITH TERRAIN FORCING; A PIEDMONT SURFACE TROUGH; THE SEA BREEZE; AND POSSIBLE DIFFERENTIAL HEATING BOUNDARY FROM EARLY MORNING SHOWERS AND MID CLOUDINESS...WILL SUPPORT THE DEVELOPMENT OF SCATTERED SHOWERS AND STORMS THIS AFTERNOON - EARLIEST FROM THE MOUNTAINS TO THE PIEDMONT. WEAK STEERING WINDS AND ASSOCIATED BULK SHEAR WILL SUPPORT A SLOW PROPAGATION ACROSS CENTRAL NC THROUGH THIS EVENING...WHILE ADDITIONAL SCATTERED CONVECTION WILL LIKELY INITIATE ALONG THE SEA BREEZE FROM VA TO THE CAROLINAS AND PROPAGATE WEST INTO THE RAH CWFA FROM THE EAST...PARTICULARLY TOWARD THE NORTHERN NC COASTAL PLAIN. ASSOCIATED PULSE STORMS WILL POSE A RISK OF STRONG WIND GUSTS AND HEAVY RAIN...BUT WEAK MID-LEVEL LAPSE RATES; WEAK SHEAR; AND WEAK DCAPE ALL SUGGEST UPDRAFTS WILL BE TOO SHORT-LIVED FOR THE DEVELOPMENT OF SEVERE HAIL OR WIND PRODUCTION. FURTHER MODIFICATION/WARMING OF THE AIR MASS...INCLUDING A CONTRIBUTION FROM INCREASINGLY NW DOWNSLOPE FLOW IN THE 925-850 MB LAYER...SHOULD SUPPORT HIGH TEMPERATURES IN THE UPPER 80S TO AROUND 90 DEGREES...THOUGH POCKETS OF MID 80S ARE PROBABLE WHERE/IF STORMS OCCUR PRIOR TO 19-20Z...MOST LIKELY OVER PORTIONS OF THE PIEDMONT. TONIGHT: ALTHOUGH THE MAJORITY OF SHOWERS AND STORMS WILL DISSIPATE AND/OR DRIFT EAST OF CENTRAL NC BY LATE EVENING-MIDNIGHT...THE AFOREMENTIONED ADDITIONAL LOW AMPLITUDE DISTURBANCE APPROACHING FROM THE EASTERN TN VALLEY AND ANOTHER FROM THE LOWER MS VALLEY... COUPLED WITH A MOIST AND LINGERING WEAKLY UNSTABLE AIR MASS...MAY SUPPORT THE DEVELOPMENT OF A FEW SHOWERS OVERNIGHT. LOWS MOSTLY IN THE MIDDLE TO UPPER 60S.
-- End Changed Discussion --
&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
-- Changed Discussion --
AS OF 415 AM MONDAY... THE MODELS CONTINUE TO INDICATE THE PIEDMONT TROUGH WILL DRIFT EAST INTO THE COASTAL PLAIN ON TUE...THOUGH CONTINUED WNW 925-850 FLOW WILL LIKELY SUPPORT THE RE-DEVELOPMENT OF A LEE TROUGH OVER THE FOOTHILLS AND PIEDMONT. WHILE BOTH MAY SERVE AS A FOCUS FOR ADDITIONAL SHOWERS AND STORMS TUE AFTERNOON...THE MODELS HAVE SUGGESTED FOR DAYS NOW THAT THE ONE OVER THE COASTAL PLAIN WILL BE THE MOST CONVECTIVELY-ACTIVE ONE IN AN ENVIRONMENT CHARACTERIZED BY RICHER BOUNDARY LAYER MOISTURE...WHERE POPS HAVE ACCORDINGLY BEEN RAISED INTO THE LOW LIKELY RANGE. THE COLD FRONT WILL THEN MOVE EAST OF THE MOUNTAINS AND CROSS CENTRAL NC WITH A RENEWED CHANCE OF A WIDELY SCATTERED SHOWER OR THREE AND SUBSEQUENTLY ENDING THE THREAT OF ANY LINGERING CONVECTION WITH FROM NW TO SE FROPA OVERNIGHT. PERSISTENCE HIGHS IN THE UPPER 80S TO AROUND 90 DEGREES...WITH LOWS IN THE 60S. AREAS OF FOG WILL BE POSSIBLE TUE NIGHT WHERE PRECEDING RAIN OCCURS DURING THE AFTERNOON AND EVENING...AT LEAST UNTIL THE COLD FRONT AND ASSOCIATED DRIER AIR ARRIVE FROM THE NW LATE.
-- End Changed Discussion --
&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
AS OF 345 AM MONDAY... THE COLD FRONT MOVING THROUGH THE AREA TUESDAY NIGHT WILL STALL TO THE SOUTH ON WEDNESDAY AND THEN LINGER OVER THE REGION THROUGH THE END OF THE WEEK AS A WAVE OF LOW PRESSURE EMANATING OVER THE SOUTHERN PLAINS MOVES EAST ALONG THE FRONTAL ZONE. MODELS CONTINUE TO EXHIBIT FAIRLY SIGNIFICANT MASS FIELD DIFFERENCES WEDNESDAY...WITH THE GFS BEING MUCH MORE AGGRESSIVE WITH THE SOUTHWARD PUSH OF THE FRONT AND NOTICEABLY WEAKER WITH THE AFOREMENTIONED WAVE OF LOW PRESSURE AS IT MOVES INTO THE MID- MISSISSIPPI RIVER VALLEY. GIVEN THAT IT IS A STRONG OUTLIER...PREFERENCE IS GIVEN TO THE ECMWF AND NAM WHEN TO COMES TO WHERE THE FRONT ENDS UP WEDNESDAY...WHICH SHOULD BE SOUTH OF THE NC/SC BORDER BUT NOT ALL THE WAY TO THE SAVANNAH RIVER BASIN. THE AIRMASS BEHIND THE FRONT WILL BE MUCH DRIER AND MORE STABLE...BUT FORECAST THICKNESSES ON THE NAM/ECMWF STILL SUPPORT MID 80S NORTH TO AROUND 90 IN THE SOUTH. MERGING SHORTWAVE OVER THE UPPER MIDWEST WILL SWING EAST ON THURSDAY AND DRIVE THE WEAK SURFACE LOW ACROSS THE TENNESSEE VALLEY AND CAROLINAS LATE THURSDAY. PRECIP CHANCES WILL INCREASE THURSDAY AND THURSDAY NIGHT AS HEIGHTS ALOFT FALL SLIGHTLY AND MOISTURE CONVERGENCE INCREASES ALONG THE FRONTAL ZONE DRIFTING BACK TOWARD THE SOUTHERN PORTIONS OF THE AREA. HOWEVER...THE FORCING ISN`T GREAT AND DESTABILIZATION WILL BE WEAK...MAINLY ACROSS SOUTHEAST CWA WHERE THE CHANCE OF AN ISOLATED THUNDERSTORM MIXED IN WITH THE SCATTERED SHOWERS WILL BE GREATEST BEFORE EVERYTHING MOVES OFF TO THE EAST BY EARLY FRIDAY. STRONGER HIGH PRESSURE IS THEN FORECAST TO BUILD ACROSS THE GREAT LAKES ON FRIDAY AND FINALLY USHER IN A LITTLE MORE OF AN AIRMASS CHANGE FOR THE WEEKEND...WITH THICKNESSES FALLING BACK BELOW NORMAL AND HIGHS LIKELY TO BE MORE IN THE UPPER 70S TO LOWER 80S FRIDAY/SATURDAY....FOLLOWED BY A WARMING TREND INTO EARLY NEXT WEEK.
-- End Changed Discussion --
&& .AVIATION /06Z MONDAY THROUGH FRIDAY/... AS OF 230 AM MONDAY... VFR CONDITIONS EXPECTED...EXCEPT IN SCATTERED SHOWERS AND STORMS THIS AFTERNOON AND EVENING...AND IN SUBSEQUENT VISIBILITY RESTRICTIONS LATER TONIGHT WHERE/IF ASSOCIATED DOWNPOURS OCCUR. A DISTURBANCE ALOFT AND BAND OF MID LEVEL MOISTURE HAS SUPPORTED THE DEVELOPMENT OF SCATTERED SHOWERS/SPRINKLES WHICH MAY AFFECT NORTHERN TAF SITES DURING THE NEXT SEVERAL HOURS. EVEN WHERE RAIN OCCURS...NO SUB-VFR RESTRICTIONS ARE EXPECTED WITH THIS LIGHT ACTIVITY. LATER TODAY...HOWEVER...A COUPLE OF ADDITIONAL WEAK DISTURBANCES ALOFT... IN CONJUNCTION WITH A PIEDMONT SURFACE TROUGH; SEA BREEZE; AND POSSIBLE DIFFERENTIAL HEATING BOUNDARY FROM EARLY MORNING SHOWERS AND MID CLOUDINESS...WILL SUPPORT THE DEVELOPMENT OF SCATTERED SHOWERS AND STORMS THIS AFTERNOON - EARLIEST AT PIEDMONT TAF SITES AND LATEST AT RWI AND FAY. ALTHOUGH THE MAJORITY OF SHOWERS AND STORMS WILL DISSIPATE AND/OR DRIFT EAST OF CENTRAL NC LATER TONIGHT...ADDITIONAL LOW AMPLITUDE DISTURBANCES ALOFT AND A MOIST AND WEAKLY UNSTABLE AIR MASS MAY SUPPORT THE DEVELOPMENT OF A FEW SHOWERS OVERNIGHT. OUTLOOK: ADDITIONAL SCATTERED SHOWERS AND STORMS MAY INTERRUPT OTHERWISE VFR CONDITIONS TUE AFTERNOON...WITH THE RELATIVE GREATEST CHANCE AT RWI AND FAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...26 SHORT TERM...26 LONG TERM...22 AVIATION...26

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.