Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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832 FXUS62 KRAH 190002 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 802 PM EDT MON MAY 18 2015 .SYNOPSIS...A SURFACE TROUGH WILL SLOWLY STRENGTHEN OVER THE PIEDMONT COUNTIES THROUGH TUESDAY. A COLD FRONT WILL CROSS CENTRAL NC TUESDAY NIGHT...THEN STALL JUST TO OUR SOUTH ON WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 312 PM MONDAY... REMAINDER OF THE AFTERNOON THROUGH TONIGHT... WHILE A MID-UPPER LEVEL RIDGE WILL MAINTAIN NOTABLE INFLUENCE OVER MOST OF CENTRAL NC THROUGH THIS EVENING...A SERIES OF UPPER LEVEL DISTURBANCES RIDING UP THE BACK SIDE OF THE RIDGE WILL TRIGGER SCATTERED CONVECTION...MAINLY OVER THE WESTERN AND SOUTHERN PIEDMONT COUNTIES...LATE THIS AFTERNOON AND TONIGHT. DEEP BUT WEAK WLY FLOW WILL STEER HIGHER TERRAIN CONVECTION EASTWARD INTO THE WESTERN PIEDMONT BY 21Z-22Z...WHILE A DISTURBANCE SEEN ON WATER VAPOR IMAGERY LIFTING NE FROM NORTHERN GA INTO SW NC WILL PROVIDE ADDITIONAL LIFT/DESTABILIZATION ALOFT TO TRIGGER ADDITIONAL CONVECTION. STILL EXPECT LIMITED COVERAGE ALONG AND EAST OF HIGHWAY 1 DUE TO PRESENCE OF UPPER RIDGE. THE EXCEPTION MAY BE THE FAR NORTHERN COASTAL PLAIN WHERE WESTWARD MOVING OUTFLOW BOUNDARIES FROM ONGOING CONVECTION IN THE ELIZABETH CITY AREA MAY BE ABLE TO TRIGGER A CLUSTER OF SHOWERS AND STORMS IN THE VICINITY OF TARBORO AND HALIFAX BY EARLY EVENING. WHILE PARAMETERS IN PLACE ARE SUFFICIENT TO INITIATE/SUPPORT SCATTERED CONVECTION...WEAK BULK SHEAR AND MARGINAL INSTABILITY SUGGEST THAT SEVERE THREAT IS MINIMAL. STILL...THE STRONGER CELLS COULD PRODUCE WIND GUSTS 35-40KTS AND POSSIBLY PEA SIZE HAIL. WHILE BULK OF CONVECTION WILL DISSIPATE WITH LOSS OF HEATING (BY 02Z- 3Z)...COULD STILL SEE ISOLATED SHOWERS PERSIST WELL INTO THE NIGHT ACROSS THE PIEDMONT DUE TO THE VERY MOIST ATMOSPHERE (PRECIP WATER VALUES AROUND 1.7 INCHES) AND PRESENCE OF WEAK SFC TROUGH. MIN TEMPS QUITE MILD FOR THIS TIME OF YEAR WITH OVERNIGHT TEMPS IN THE 65-70 DEGREE RANGE. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 312 PM MONDAY... A SERIES OF S/W ROTATING THROUGH THE GREAT LAKES AND INTO NEW ENGLAND WILL WEAKEN THE UPPER LEVEL RIDGE OVER CENTRAL NC. THE LEAD S/W IN THIS SERIES WILL ALSO USHER A SFC COLD FRONT INTO OUR REGION TUESDAY...DRIFTING SLOWLY SEWD AND EXITING OUR REGION LATE TUESDAY NIGHT. SUFFICIENT MOISTURE AND DESTABILIZATION WILL TRIGGER SCATTERED CONVECTION BY AFTERNOON...ESPECIALLY FOR LOCATIONS ALONG AND EAST OF HIGHWAY 1. OVER THE WEST-NW SECTIONS OF THE PIEDMONT...CONVECTION EXPECTED TO BE NO WORSE THAN 25-30 PERCENT COVERAGE...DECREASING APPRECIABLY IN COVERAGE BY LATE AFTERNOON. SIMILAR TO TODAY...WHILE CONVECTIVE PARAMETERS SUPPORTIVE OF CONVECTION...MARGINAL/WEAK INSTABILITY AND WEAK SHEAR WILL LIMIT CHANCE FOR THE DEVELOPMENT OF SEVERE STORMS. HIGH TEMPS TRICKY FOR TUESDAY AS POTENTIAL FOR STRONG HEATING PRIOR TO THE INITIATION OF CONVECTION. WILL FAVOR THE WARMER MAV GUIDANCE WITH MAX TEMPS UPPER 80S TO AROUND 90. IF CLOUDS/CONVECTION DEVELOP SOONER THAN EXPECTED...MAX TEMPS MAY END UP 3-5 DEGREES COOLER THAN FORECAST. WITH SLOW FRONTAL MOVEMENT ANTICIPATED TUESDAY NIGHT...A THREAT FOR SHOWERS AND ISOLATED STORMS WARRANTED WELL INTO THE NIGHT ACROSS SECTIONS OF THE COASTAL PLAIN AND SANDHILLS. DUE TO SLUGGISH MOVEMENT AND DELAYED ARRIVAL OF COOLER/STABLE AIR...HAVE ADJUSTED MIN TEMPS CLOSER TO THE WARMER MET GUIDANCE. MAY ALSO SEE AREAS OF FOG DEVELOP...ESPECIALLY AREAS THAT EXPERIENCE HEAVIER SHOWERS EARLIER IN THE DAY. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... AS OF 312 PM MONDAY... THE COLD FRONT WILL LIKELY BE LOCATED ALONG THE CAROLINA COAST AT 12Z WEDNESDAY WITH A 1028MB HIGH PRESSURE SYSTEM CENTERED NEAR THE DAKOTAS EXTENDING SOUTHEAST INTO THE OHIO VALLEY AND MID ATLANTIC. THE FLOW ALOFT ACROSS THE EASTERN CONUS IS GENERALLY WESTERLY SUGGESTING LITTLE ADDITIONAL SOUTHWARD PROGRESS FOR THE FRONT. THE AIR MASS BEHIND THE FRONT IS NOTABLY COOLER AND DRIER...ALTHOUGH IT IS UNCLEAR HOW MUCH TRUE AIR MASS CHANGE WILL BE REALIZED IN CENTRAL NC BEHIND THE FRONT. REGARDLESS...WEDNESDAY SHOULD FEATURE A QUIET WEATHER DAY WITH LOTS OF SUNSHINE. HAVE KEPT HIGHS SLIGHTLY ABOVE GUIDANCE AS THICKNESSES ARE STILL RATHER WARM AND THE TRUE AIRMASS CHANGE MAY BE SLOW TO ARRIVE CENTRAL NC. HIGHS WILL RANGE FROM 82 NORTHEAST TO 89 NEAR THE SC BORDER. HEIGHTS BEGIN TO FALL SLIGHTLY WEDNESDAY NIGHT AS MEAN TROUGHINESS AND A CYCLONIC FLOW ALOFT STRENGTHENS IN THE EASTERN US. A SHEARING SHORT WAVE TROUGH DROPS ACROSS THE GREAT LAKES INTO THE OH VALLEY ON THURSDAY AND A WEAK SURFACE WAVE DEVELOPS IN RESPONSE ACROSS THE CAROLINA PIEDMONT. DETERMINISTIC MODEL RUNS SHOW LITTLE CONSISTENCY IN THE PLACEMENT OF THE SURFACE WAVE ON THURS MORNING WITH THE EC`S LOW NEAR KFAY...THE NAM LOW NEAR KCAE AND THE GFS NEAR KSAV. STILL ALL OF THE GUIDANCE NOTE A NORTHWARD ADJUSTMENT TO THE LINGERING COLD FRONT AND SUFFICIENT CONVERGENCE AND FORCING FOR AN INCREASE IN CONVECTION ON THURSDAY AND ESPECIALLY AFTERNOON AND EVENING THAT WILL LINGER INTO THE COASTAL PLAIN ON FRIDAY MORNING. THE SURFACE LOW POSITION AND THE DEGREE OF CLOUD COVER AND PRECIPITATION WILL HAVE A BIG IMPACT ON TEMPERATURES. THE 00Z EC ENSEMBLE GUIDANCE HAD A HIGH TEMP RANGE FOR THURSDAY OF 88 TO 75 AT KRDU AND 92 TO 80 AT KFAY. HAVE INCREASED POPS UPWARD FOR THIS PERIOD. WITH VERY LIMITED INSTABILITY...THE AMOUNT AND INTENSITY OF CONVECTION ON THURSDAY SHOULD BE RATHER MODEST. HOWEVER...ITS WORTH NOTING THAT THE JUXTAPOSITION OF 35-50 KTS OF DEEP LAYER SHEAR NEAR THE VICINITY OF THE SURFACE WAVE ATTRACTS SOME INTEREST. EXPERIMENTAL SHERBS3 PARAMETERS ARE NOT TOO EXCITED EITHER. SEVERE CONVECTION APPEARS TO BE A VERY LOW PROBABILITY POSSIBILITY AT THIS POINT. HIGHS ON THURSDAY WILL RANGE IN THE UPPER 70S NEAR THE VA BORDER TO MID 80S NEAR SC. LOWS WILL RANGE IN THE LOWER TO MID 60S. ANY LINGERING SHOWERS OR STORMS SHOULD SHIFT EAST OF CENTRAL NC ON FRIDAY AFTERNOON AND EVENING AS A 1028MB AREA OF HIGH PRESSURE BUILDS INTO THE REGION. HIGHS FRIDAY SHOULD RANGE IN THE UPPER 70S TO LOWER 80S. THE AREA OF HIGH PRESSURE WILL STRENGTHEN AND BUILD INTO THE REGION ON SATURDAY...YIELDING A VERY NICE DAY WITH A MIX OF SUNSHINE AND A FEW CLOUDS. THE AIR MASS WILL BE MORE PLEASANT WITH DEWPOINTS FALLING WELL INTO THE 50S AND HIGHS RANGING FROM 79 NORTHEAST TO 84 SOUTHWEST. THE HIGH WILL SHIFT OFFSHORE ON SUNDAY AND MONDAY WITH A GRADUAL INCREASE IN SOUTHERLY FLOW. THIS WILL RESULT IN A FEW MORE CLOUDS AND AN INCREASE IN TEMPERATURES AND HUMIDITY. SUNDAY WILL BE A DRY DAY AND MONDAY SHOULD BE DRY ACROSS MOST OF THE AREA EXCEPT IN THE WEST WERE A FEW THUNDERSTORMS MAY DEVELOP IN THE MOUNTAINS AND FOOTHILLS AND PUSH INTO THE WESTERN PIEDMONT LATE IN THE DAY. HIGHS ON SUNDAY WILL RANGE IN THE LOWER TO MID 80S WITH HIGHS IN THE MID TO UPPER 80S ON MONDAY. MORNING LOWS WILL RANGE IN THE LOWER TO MID 60S. -BLAES && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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AS OF 800 PM MONDAY... 24 HOUR TAF PERIOD: SCATTERED SHOWERS AND THUNDERSTORMS MAINLY WEST OF US HIGHWAY 1 WILL CONTINUE THROUGH THE EVENING HOURS AND POSSIBLY INTO THE EARLY OVERNIGHT HOURS. MAY BE SOME BRIEF VISIBILITY RESTRICTIONS IN HEAVIER SHOWERS BUT OTHERWISE VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD OUTSIDE OF SHOWERS/STORMS. WINDS WILL VEER TO SOUTHWESTERLY AND THEN EVENTUALLY NORTHWESTERLY AS COLD FRONT APPROACHES THE AREA ON TUESDAY. THE FOCUS FOR CONVECTION WILL SHIFT EAST OF HIGHWAY 1 TUESDAY EVENING. LONG TERM: THE BEST CHANCE FOR ADVERSE CONDITIONS IN THE LONG TERM WILL BE ON THURSDAY AS A LOW PRESSURE SYSTEM OVER CENTRAL NC. OTHERWISE MAINLY VFR CONDITIONS EXPECTED.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...BLAES AVIATION...ELLIS

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