Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 020530 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 130 AM EDT TUE JUN 2 2015 .SYNOPSIS...A MID LEVEL LOW PRESSURE TROUGH AND SURFACE COLD FRONT OVER THE TENNESSEE VALLEY WILL MOVE SLOWLY EASTWARD THEN STALL OVER THE CAROLINAS THROUGH THE WORK WEEK... BRINGING UNSETTLED WEATHER. && .NEAR TERM /THROUGH TONIGHT/... AS OF 940 PM MONDAY... CENTRAL NC IS IN A RELATIVE MINIMUM OF INSTABILITY AS THE BOUNDARY LAYER HAS BEEN OVERTURNED BY EARLIER CONVECTION. THERE CONTINUES TO BE AREAS OF WEAK INSTABILITY (AROUND 500 J/KG) THAT THE OUTFLOW DRIVEN CONVECTION NORTH AND WEST OF CHARLOTTE CAN WORK ON OVER OUR WESTERN PIEDMONT REGION. WE WILL KEEP LIKELY POP GOING FOR SEVERAL MORE HOURS TO ACCOUNT FOR THE LINE OF SHOWERS AND THUNDERSTORMS THAT SHOULD REACH THE YADKIN RIVER BEFORE MIDNIGHT. ADDITIONAL CONVECTIVE CLUSTERS CONTINUE ON OLD OUTFLOWS NEAR FLORENCE SC WHICH MAY REACH THE FAYETTEVILLE AREA LATER. WE WILL KEEP THE CHANCE POP ALONG THE INTERSTATE 95 CORRIDOR TO ACCOUNT FOR THIS POSSIBILITY ALONG WITH THE RESIDUAL SCATTERED SHOWERS ONGOING FROM WILSON TO ROANOKE RAPIDS. OTHERWISE... MOST AREAS SHOULD SEE THE CHANCE OF SHOWERS AND THUNDERSTORMS DROP OFF LATER TONIGHT TO SLIGHT OR LOW CHANCES DURING THE DIURNAL MINIMUM AROUND DAYBREAK. LOWS GENERALLY 65-70. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 345 PM MONDAY... THE COLD FRONT WILL STRETCH FROM SOUTHERN VIRGINIA SOUTHWEST TO NORTHWESTERN NC ON TUESDAY MORNING. THE FRONT WILL MAKE VERY SLOW SOUTHWARD PROGRESS ACROSS CENTRAL NC ON TUESDAY AND TUESDAY NIGHT BEFORE SETTLING NEAR THE NC/SC BORDER BY WEDNESDAY MORNING. THE FRONTAL PROGRESSION MAY BE VERY LIMITED EARLY IN THE DAY AND THEN AIDED BY CONVECTIVE OUTFLOW AND PRECIPITATION DURING THE AFTERNOON AND EVENING. THE UPPER LEVEL LOW ACROSS WESTERN TN/KY AT THE START OF THE PERIOD IS CUT OFF FROM THE WESTERLIES AND SLOWLY MOVES EASTWARD REACHING SOUTHEAST TN BY WEDNESDAY MORNING. AHEAD OF THE CLOSED LOW...A NARROW BUT MOIST FETCH OF MOISTURE WILL SPREAD INTO THE CAROLINAS. WITH SREF PW VALUES CLIMBING TO AROUND 1.75 INCHES. AS THE UPPER LOW APPROACHES...FORCING FOR ASCENT INCREASES AND SCATTERED TO WIDESPREAD CONVECTION IS LIKELY TO DEVELOP DURING THE AFTERNOON AND EVENING WITH MULTIPLE ROUNDS OF CONVECTION LIKELY TO SPREAD EAST ACROSS THE AREA. THE APPROACHING UPPER LOW RESULTS IN STRENGTHENING SHEAR WITH BULK SHEAR VALUES INCREASING TO 20-30 KTS BY TUESDAY AFTERNOON WHICH SHOULD SUPPORT A SLIGHTLY INCREASED SEVERE WEATHER THREAT BUT THE MAIN HAZARDOUS WEATHER THREAT WILL BE FROM LOCALLY HEAVY RAIN. WIDESPREAD CLOUDINESS AND THE INFILTRATION OF A COOLER AIR MASS WILL RESULT IN HIGHS ONLY IN THE LOWER TO MID 80S. -BLAES. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... AS OF 310 PM MONDAY... WET WEATHER WILL CONTINUE THROUGH WED. THE MID LEVEL LOW OVER ERN TN EARLY IN THE DAY WILL CONTINUE A VERY SLOW WOBBLE TO THE EAST DURING THE DAY... AS A LOBE OF VORTICITY ROTATES NORTHWARD THROUGH CENTRAL NC. PW VALUES WILL REMAIN ELEVATED (150-180% OF NORMAL) WITH A CONFLUENT LOW LEVEL ATLANTIC-SOURCE FLOW AND AT LEAST MODERATE UPPER DIVERGENCE AS WEAK JETLETS ROTATE ABOUT THE UPPER LOW. LATEST MODEL RUNS SHOW THE FRONT DROPPING INTO FAR NRN AND NW NC EARLY WED MORNING... WHICH SHOULD HELP FOCUS RAINFALL. MARGINAL INSTABILITY PERSISTS WITH PROJECTIONS OF 500-1000 J/KG OF MUCAPE MAINLY IN THE SW CWA. THE COMBO OF MOISTURE/LIFT/INSTABILITY SUPPORTS RETAINING LIKELY POPS (AND IF TRENDS CONTINUE THESE SHOULD GO UP TO CATEGORICAL IN LATER FORECASTS). RAIN TOTALS MAY BE LOCALLY HEAVY WITH POSSIBLE TRAINING CONVECTIVE ELEMENTS. ADJUSTMENT BY EARLIER SHIFTS OF TAKING WED MAX TEMPS DOWN ESPECIALLY N AND NW OF THE FRONT (NW CWA) LOOKS GOOD AND WILL STAY THAT COURSE... WITH HIGHS FROM THE LOWER 70S NW TO LOWER 80S SE... IN LINE WITH STATISTICAL GUIDANCE. THERE MAY BE A SLIGHT BIT OF DRYING (MARGINALLY LOWER PW AND A LULL IN DPVA) ROTATING ABOUT THE LOW AND WORKING INTO THE SW CWA WED NIGHT... BUT WITH PW STILL ABOVE NORMAL AND THE SURFACE WEDGE FRONTAL ZONE IN PLACE... WILL KEEP A CHANCE OF SHOWERS IN OVERNIGHT. LOWS 61-66 NW TO SE. MORE OF THE SAME THU WITH THE SYNOPTIC CONFIGURATION SIMILAR TO WED... EXCEPT THE MID LEVEL LOW TO OUR WEST WILL HAVE DRIFTED SLIGHTLY CLOSER... INTO FAR WRN NC. INSTABILITY MAY BE A TAD HIGHER (750-1500 J/KG AREAWIDE ON THE GFS) WITH SIMILAR WEAK DPVA... UPPER DIVERGENCE... PW 150-180% OF NORMAL... AND ONSHORE-DIRECTED LOW LEVEL FLOW FOCUSED ALONG THE FRONTAL ZONE. EXPECT ANOTHER ROUND OF NUMEROUS SHOWERS AND EMBEDDED STORMS... PEAKING IN THE AFTERNOON AND EVENING. THICKNESSES ARE EXPECTED TO BE 10 M BELOW NORMAL... AND FACTORING IN THE CLOUDS AND PRECIP... PREFER TO KEEP HIGHS BELOW NORMAL (MID 70S TO MID 80S)... AND EVEN THESE MAY BE TOO HIGH IN THE NW HALF OF THE CWA. WILL TREND PRECIP CHANCES DOWN BUT NOT OUT THU NIGHT AS THE BY-NOW-WEAKENING UPPER LOW STARTS TO SHIFT OVERHEAD. LOWS IN THE MID 60S. COOLER-THAN-NORMAL WEATHER IS LIKELY TO EXTEND INTO FRI... BUT MODERATING SLOWLY AS WE GO THROUGH THE SAT-MON TIME FRAME. THE UPPER LOW WILL OPEN UP AND WEAKEN TO A BAGGY TROUGH WHILE CONTINUING AN EASTWARD DRIFT OFF THE MIDATLANTIC COAST... HOWEVER THIS TROUGH AXIS IN THE MEAN MAY LINGER OVER OUR AREA THROUGH MON... AS WEAK ENERGY MAY DROP IN FROM THE NW TO RELOAD THE TROUGH OVERHEAD. THE ECMWF IS MORE ROBUST WITH THIS... RESULTING IN ANOTHER CLOSED LOW OVER THE CAROLINAS SUN INTO MON... WHILE THE GFS IS MUCH LESS AMPLIFIED... FOCUSING INSTEAD ON STRONG NRN STREAM TROUGHING DEVELOPING OVER SOUTH CENTRAL CANADA INTO THE UPPER MIDWEST. THE GFS HAS BEEN SLIGHTLY MORE CONSISTENT BUT OTHERWISE THERE IS NO CLEAR INDICATION OF WHICH SOLUTION IS MORE LIKELY. THE FRONTAL ZONE SHOULD HOLD IN PLACE (WITH NOTHING TO MOVE IT OUT) YET CONTINUE TO SLOWLY WASH OUT WITH TIME... AND THE GFS KEEPS PW VALUES ABOVE NORMAL. SO WITH WEAK (BUT NON-ZERO) FORCING FOR ASCENT AND ABOVE NORMAL MOISTURE IN PLACE WITH LIMITED FOCUS... WE SHOULD SEE DAILY SHOWERS AND STORMS... NEAR OR JUST ABOVE CLIMATOLOGICAL COVERAGE. WILL HAVE TEMPS SLIGHTLY BELOW NORMAL FRI... RISING BACK TOWARD NORMAL BY MON. -GIH && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... AS OF 130 AM TUESDAY... A VERY MOIST AIR MASS OVER THE CAROLINAS COUPLED WITH THE APPROACH OF A LOW PRESSURE SYSTEM AND ITS ATTENDANT SFC COLD FRONT WILL RESULT IN ADVERSE AVIATION CONDITIONS ACROSS MUCH OF CENTRAL NC THROUGH WEDNESDAY NIGHT. ISOLATED SHOWERS WILL TRAVERSE SOUTH-NORTH ACROSS THE AREA EARLY THIS MORNING. AWAY FROM THE CONVECTION...THERE MAY BE AREAS OF IFR/LIFR FOG AND CEILINGS....MAINLY OVER THE PIEDMONT. WHERE THESE LOW CEILINGS/VISIBILITIES OCCUR...EXPECT CONDITIONS TO CHANGE LITTLE THROUGH 13-15Z. AFTER 12Z...EXPECT THE SHOWERS TO BECOME A LITTLE MORE NUMEROUS OVER THE PIEDMONT AND POSSIBLY OVER THE SANDHILLS AS A PERTURBATION ALOFT LIFTS NWD ACROSS THE REGION. THESE SHOWERS AND ISOLATED STORMS WILL CAUSE PERIODS OF MVFR CEILINGS/VISIBILITY. HEATING OF THE MOIST AND SLIGHTLY UNSTABLE ATMOSPHERE THIS AFTERNOON WILL CAUSE NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS TO DEVELOP WITH THE GREATEST CONCENTRATION EXPECTED OVER THE EASTERN HALF OF CENTRAL NC. THIS BATCH OF CONVECTION MAY IMPACT KRDU...KFAY AND KRWI. THE AREAS OF CONVECTION WILL BE SLOW TO DIMINISH TONIGHT AS A SFC COLD FRONT DRIFTS SOUTHWARD INTO OUR AREA. THIS FEATURE WILL LIKELY AID TO MAINTAIN A FEW SHOWERS AND STORMS WELL INTO THE NIGHT. THE UNSETTLED WEATHER PATTERN WILL CONTINUE WEDNESDAY INTO THURSDAY AS THE ATMOSPHERE WILL MAINTAIN ITS MOIST AND SLIGHTLY UNSTABLE CHARACTER. THIS WILL CAUSE PERIODS OF MVFR/IFR CONDITIONS DUE TO CEILINGS AND CONVECTION. CONDITIONS WILL BEGIN TO SLOWLY IMPROVE FRIDAY AND SATURDAY AS THE ATMOSPHERE BECOMES SLIGHTLY DRIER. THIS WILL LEAD TO FEWER SHOWERS AND STORMS DURING THE HEAT OF THE AFTERNOON-EARLY EVENING. HOWEVER...THERE IS STILL A GOOD PROBABILITY OF EARLY MORNING MVFR/IFR CEILINGS AND VISIBILITY BOTH MORNINGS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...BADGETT SHORT TERM...BLAES LONG TERM...HARTFIELD AVIATION...WSS

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