Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 090527 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 125 AM EDT WED JUL 9 2014 .SYNOPSIS...A SURFACE TROUGH WILL PERSIST OVER CENTRAL NORTH CAROLINA TODAY. A WEAKENING COLD FRONT WILL MOVE INTO OUR REGION THURSDAY...THEN DRIFT TOWARD THE COAST FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 930 PM TUESDAY... WEAK CONVECTION AIDED BY A SMALL MCV MOVING SOUTH OF MARTINSVILLE IS MOVING THROUGH THE TRIAD AND HAS MUSTERED UP A COUPLE OF 40 MPH GUSTS BUT NOT MUCH MORE. THIS SHOULD EVENTUALLY DIE OUT AS THE ENVIRONMENT BECOMES LESS FAVORABLE TO THE EAST BUT SOME LIGHT RAIN COULD MAKE IT AS FAR EAST AS THE TRIANGLE BUT THAT IS ABOUT IT. WINDS WILL STAY UP A LITTLE OVERNIGHT AT 5-10 KTS OUT OF THE SOUTHWEST. RELATIVE HUMIDITY CROSS SECTIONS AND ATMOSPHERIC SOUNDINGS ARE VERY DRY AT LOW LEVELS AND NOT MUCH FOG OR LOW STRATUS IS EXPECTED OVERNIGHT TONIGHT. IT WILL BE A WARM NIGHT AS TEMPERATURES ARE NOT EXPECTED TO GET MUCH LOWER THAN THE LOWER 70S. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 255 PM TUESDAY... BOTH THE NAM AND THE GFS FORECAST A MODEST BUT WEAKENING MID-LEVEL SHORTWAVE MOVING THROUGH CENTRAL NORTH CAROLINA WEDNESDAY...FOLLOWED BY ANOTHER MID-LEVEL WAVE WEDNESDAY NIGHT. ADVECTION OF K INDICES CONTINUES OVERNIGHT...WITH VALUES AT OR ABOVE 30 ACROSS CENTRAL NORTH CAROLINA FOR THE DAY WEDNESDAY. THE SOUTHWEST FLOW ALOFT THAT OCCURS OVER CENTRAL NORTH CAROLINA AS THE MID-LEVEL TROUGH SHARPENS TO OUR WEST SHOULD KEEP MOISTURE IN PLACE THROUGH AND BEYOND THIS PERIOD...WITH PERIODS OF LIFT IN ASSOCIATION WITH MID-LEVEL FORCING...A SURFACE TROUGH...AND THE APPROACHING FRONT FROM THE NORTHWEST FOR ISOLATED-TO-SCATTERED SHOWERS AND THUNDERSTORMS. NAM AND GFS BUFR SOUNDINGS ARE SOMEWHAT MOIST IN CENTRAL NORTH CAROLINA WEDNESDAY INTO WEDNESDAY NIGHT...MOST SO TOWARD THE TRIAD AND LEAST SO TOWARD KFAY. CHANCES FOR PRECIPITATION WEDNESDAY WILL BE GRADUATED AS SUCH...HIGHEST IN THE NORTHWEST PIEDMONT AND TOWARD THE VIRGINIA BORDER...LEAST IN THE SOUTHERN COASTAL PLAIN. BY WEDNESDAY NIGHT...WITH FORECAST LIFT AND INSTABILITY SHIFTING EAST...SIMILAR CHANCES FOR SHOWERS AND THUNDERSTORMS WILL EXIST ACROSS CENTRAL NORTH CAROLINA...HIGHEST NORTHEAST CLOSER TO THE SURFACE BOUNDARY. 1000-500MB LAPSE RATES ARE NOT VERY STRONG NORTH AND NORTHWEST OF THE TRIANGLE...ONLY FORECAST BY THE GFS TO JUST UNDER 6C/KM. FARTHER SOUTH...WHERE THERE IS POTENTIAL FOR BETTER HEATING...THOSE LAPSE RATES ARE NEAR 7C/KM. IT MAY BE OVER THE NORTHEAST PIEDMONT AND THE NORTHERN COASTAL PLAIN...WHERE THE BEST COMBINATION OF 0-3KM SHEAR...INSTABILITY...MOISTURE...AND LIFT RESIDE WEDNESDAY AFTERNOON...WHERE THE STRONGER STORMS MAY OCCUR. THE ARW WRF SUGGESTS THIS...BUT NOT CONFIDENT ENOUGH AT THIS TIME TO BE THAT SPECIFIC IN THE HAZARDOUS WEATHER OUTLOOK. SPC DAY TWO OUTLOOK SHOWS A FIVE PERCENT OUTLOOK FOR ALL OF CENTRAL NORTH CAROLINA FOR WEDNESDAY...AND WILL RETAIN THE CURRENT WORDING IN THE HWO. SREF GUIDANCE AND BUFR SOUNDINGS SUGGEST GOOD POTENTIAL FOR DECENT CLOUD COVER FOR MUCH OF WEDNESDAY IN THE NORTHWEST PIEDMONT...AND HIGH TEMPERATURES ON WEDNESDAY WILL HAVE A GRADIENT FROM THE MID TO UPPER 80S OVER THE IMMEDIATE TRIAD TO AROUND 95 TOWARD KFAY. SURFACE WINDS SHOULD GUST TO AROUND 20KT AT TIMES TOWARD KFAY WEDNESDAY IN BETTER HEATING...WITH LESSER GUSTS OUTSIDE OF ANY DEEP CONVECTION ELSEWHERE. OVERNIGHT LOWS WEDNESDAY NIGHT 68 TO 74. && .LONG TERM /THURSDAY THROUGH TUESDAY/... AS OF 230 PM TUESDAY... FOR THU THROUGH FRI NIGHT: THU STILL APPEARS TO BE THE BUSIEST WEATHER DAY IN TERMS OF STORM COVERAGE. A SURFACE TROUGH WILL HOLD OVER CENTRAL NC THU... WITH ELEVATED LOW LEVEL MOISTURE TRANSPORT MAINLY EAST/SOUTH OF THE TRIAD. ALOFT... BROAD TROUGHING SETTING UP JUST TO OUR WEST WILL DRAW IN NRN STREAM ENERGY AS WELL AS PULL IN PERTURBATIONS FROM AN UPPER LEVEL WEAKNESS OVER THE WRN GULF OF MEXICO. WHILE THE TROUGH ITSELF WILL BE SOMEWHAT WEAK AT THIS LATITUDE WITH MINIMAL HEIGHT FALLS (10 M AT MOST ON THU) AND MLLR VALUES UNDER 6.5 C/KM... THE ADDED DYNAMIC FORCING FOR ASCENT SHOULD SUPPORT AT LEAST SCATTERED CONVECTION (MAXIMIZING IN -- BUT NOT RESTRICTED TO -- THE AFTERNOON/EVENING) DESPITE MARGINAL VALUES OF INSTABILITY DUE TO LAYERS OF A MOIST ADIABATIC PROFILE (NAM MLCAPE TOPPING OUT AT 500-1000 J/KG WITH GFS MUCAPE OF 1000-1500 J/KG IN THE EAST THU). FORECAST DEEP LAYER SHEAR VALUES ARE MORE FAVORABLE THAN YESTERDAY`S MODEL RUNS... NOW AROUND 25-35 KTS OVER NRN/WRN NC... INDICATING THE POTENTIAL FOR MORE ORGANIZED CONVECTION... ALTHOUGH THIS BETTER SHEAR WILL NOT QUITE BE SPATIALLY ALIGNED IN AN IDEAL MANNER WITH THE GREATER INSTABILITY. NEVERTHELESS... PW VALUES WILL REMAIN ABOVE NORMAL (1.7-2.0 IN.)... AND THIS MOISTURE COMBINED WITH WEAK STEERING FLOW AND A DECENT WARM CLOUD DEPTH NEAR 3.5 KM SUGGESTS THAT SLOW-MOVING CELLS WITH EFFICIENT RAIN PROCESSES MAY GENERATE LOCALLY HEAVY RAINFALL. WILL BUMP UP POPS TO LIKELY... HIGHER EAST THAN WEST... ON THU EXTENDING INTO EARLY THU NIGHT... UNTIL THE MID LEVELS BEGIN TO DRY OUT A BIT. THE MID LEVEL TROUGH AXIS SHIFTS EAST OF THE SRN APPALACHIANS FRI... KEEPING ERN NC IN THE CROSSHAIRS OF SUFFICIENTLY DEEP MOISTURE AND MARGINAL SHEAR AND INSTABILITY... ENOUGH TO SUPPORT PRIMARILY AFTERNOON AND EVENING SHOWERS AND STORMS... WITH THE BEST CHANCES EAST OF I-95... ALONG/EAST OF WHERE THE SURFACE TROUGH SETTLES. EXPECT LOWER COVERAGE OVER THE REST OF CENTRAL NC WITH PW SLIPPING TO NEAR OR JUST BELOW NORMAL AND LOWER DEEP LAYER SHEAR (15-20 KTS)... ALTHOUGH GFS MUCAPE PEAKS ONCE AGAIN AT 1000-1500 J/KG OVER CENTRAL NC... SO CAN`T RULE OUT SCATTERED STORMS. WILL KEEP POPS RANGING FROM 25% NW TO 40-50% SE FRI. AN APPROACHING SHORTWAVE TROUGH... POTENT BUT SLOWLY WEAKENING... WILL DROP ESE THROUGH THE LOWER GREAT LAKES/OH VALLEY LATE FRI NIGHT... LIKELY LEADING TO CONTINUED PARTLY TO MOSTLY CLOUDY SKIES DOWNSTREAM OVER NC OVERNIGHT. THICKNESSES ARE PROJECTED TO BE NEAR NORMAL THU... WHICH WITH CONSIDERATION OF GOOD CONVECTIVE CLOUD COVERAGE WOULD SUPPORT HIGHS OF 86-92. THU NIGHT LOWS NOT FAR FROM NORMAL... 67-72. SLIGHTLY LESS WARMTH ON FRI WITH BELOW-NORMAL THICKNESSES POINTING TO HIGHS OF 86-90. FOR SAT-SUN: THE SURFACE TROUGH OVER ERN NC IS LIKELY TO DISSIPATE SAT AS IT IS OVERTAKEN BY THE ATLANTIC RIDGE BULGING WESTWARD... WITH FORMATION OF A NEW WEAK LEE TROUGH OVER THE PIEDMONT AND SOME ATTENDANT MINOR RECOVERY OF PW. THE AFOREMENTIONED WEAKENING MID LEVEL WAVE WILL CROSS THE MIDATLANTIC REGION SAT... ALTHOUGH MODEL DISPARITY EMERGES AS THE ECMWF IS SLOWER/STRONGER THAN THE GFS AND THEREFORE GENERATES MORE CONVECTION OVER CENTRAL/ERN NC. WILL RETAIN CHANCE POPS SAT... HIGHER EAST THAN WEST... GENERALLY FOLLOWING THE TYPICAL DIURNAL TREND. THE GFS DEPICTS FURTHER RECOVERY OF PW VALUES SUN WITH ANOTHER MINOR WAVE CROSSING THE REGION WITHIN VERY WEAK CYCLONIC FLOW AND A RETENTION OF THE PIEDMONT SURFACE TROUGH... AND WE SHOULD SEE YET ANOTHER ROUND OF MAINLY SCATTERED DIURNALLY-DRIVEN STORMS IN THE MID AFTERNOON INTO EARLY EVENING... WITH COVERAGE AND INTENSITY LIMITED BY THE WEAK DEEP LAYER SHEAR. FOR MON-TUE: THE GFE HAS COME INTO AGREEMENT WITH THE ECMWF`S SOLUTION (CONSISTENT OVER THE LAST FEW RUNS) REGARDING THE DEEPENING MID LEVEL VORTEX WHICH DRIFTS ACROSS THE GREAT LAKES/SE ONTARIO EARLY NEXT WEEK. THE PIEDMONT SURFACE TROUGH WILL SHARPEN AND PUSH A BIT TO THE SOUTHEAST IN RESPONSE TO THE APPROACHING SYNOPTIC COLD FRONT... EXPECTED TO PROGRESS SOUTHEAST TOWARD NW NC BY LATE TUE. PW REMAINS ABOVE NORMAL AREAWIDE MON... THEN THE HIGHER VALUES SHIFT TO OUR EAST TUE WITH THE SHIFTING TROUGH AND STRENGTHENING LOW AND MID LEVEL FLOW FROM THE WSW. WILL RETAIN CLIMATOLOGICALLY TYPICAL POPS MON (SLIGHTLY LOWER IN THE TRIAD AND HIGHER TO THE SOUTH/EAST... FOCUSED ON THE AFTERNOON INTO MID EVENING)... THEN TREND POPS BACK DOWN A TAD IN THE WEST TUE. THICKNESSES REBOUND BACK CLOSER TO NORMAL SO WILL NOT DEPART MUCH FROM SEASONAL NORMALS MON/TUE (WITH NORMAL HIGH/LOW OF 90/70 AT RDU AND 89/69 AT GSO). -GIH && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 125 AM WEDNESDAY... VFR CONDITIONS WILL GENERALLY PERSIST THROUGH 18Z. AFTER 18Z...A SERIES OF UPPER LEVEL DISTURBANCES COUPLED WITH A SLOWLY WEAKENING SURFACE COLD FRONT WILL INCREASE THE THREAT FOR SCATTERED CONVECTION ACROSS CENTRAL NC. BETWEEN 20Z AND 01Z...THE THREAT FOR SCATTERED CONVECTION AND ASSOCIATED MVFR/IFR CEILINGS AND VISIBILITIES WILL BE GREATEST ON VICINITY OF THE TRIAD TERMINALS AS WELL AS KRDU. IN VICINITY OF THE STRONGER CONVECTION...WIND GUSTS UP TO 40KTS PROBABLE. THE ATMOSPHERE WILL REMAIN UNSETTLED TONIGHT THROUGH THURSDAY NIGHT AS THE SURFACE COLD FRONT GRADUALLY DRIFTS SEWD ACROSS THE REGION AND THE SERIES OF DISTURBANCES LIFT ACROSS THE REGION. WHILE CONVECTIVE COVERAGE AND INTENSITY WILL DWINDLE OVERNIGHT...ISOLATED TO SCATTERED SHOWERS AND T-STORMS WILL STILL OCCUR WELL PAST MIDNIGHT. THE CONVECTIVE ACTIVITY IS EXPECTED TO REACH ITS PEAK COVERAGE THURSDAY AFTERNOON AND EVENING WHEN SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BE NUMEROUS. BETTER AVIATION CONDITIONS ANTICIPATED FRIDAY THROUGH SATURDAY AS A SLIGHTLY DRIER MORE STABLE AIR MASS ENCOMPASSES MOST OF THE REGION. SCATTERED AFTERNOON-EARLY EVENING CONVECTION WILL STILL BE PROBABLE IN VICINITY OF KFAY AND KRWI WHERE AVAILABLE MOISTURE AND LOW LEVEL INSTABILITY WILL BE BEST. BY SUNDAY...REMNANTS OF DECAYING THUNDERSTORM COMPLEXES ORIGINATING IN THE MIDWEST MAY BEGIN TO AFFECT CENTRAL NC...LEADING TO A BETTER CHANCE FOR SCATTERED CONVECTION AND ASSOCIATED MVFR CONDITIONS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...ELLIS SHORT TERM...DJF LONG TERM...HARTFIELD AVIATION...WSS

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