Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 290148 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 945 PM EDT THU APR 28 2016 .SYNOPSIS...A FRONTAL ZONE NEAR THE VIRGINIA NORTH CAROLINA BORDER WILL SAG SOUTH INTO NORTH CAROLINA OVERNIGHT... THEN SHIFT BACK NORTHWARD FRIDAY... BEFORE ONCE AGAIN DROPPING SOUTH THROUGH THE REGION FRIDAY NIGHT. THE FRONT WILL THEN QUICKLY RETURN NORTHWARD AS A WARM FRONT LATE SATURDAY AND SATURDAY NIGHT. && .NEAR TERM /TONIGHT/... AS OF 945 PM THURSDAY... MUCH OF THE FORECAST AREA HAS BEEN WORKED OVER WITH GROWING MLCIN... LEADING TO A DWINDLING SEVERE THREAT... ALTHOUGH A FEW POTENT STORMS FROM RALEIGH DOWN EAST STILL WARRANT SOME ATTENTION WITH EFFECTIVE SHEAR STILL FAVORABLE AT 35-45 KTS AND LINGERING INSTABILITY ALOFT (MUCAPE STILL NEAR 1000 J/KG WITH 6.0+ C/KM MLLR)... AND ADDITIONAL SUPPORT FOR ASCENT FROM WEAK UPPER DIVERGENCE MAXIMUM AND A WEAK PASSING MID LEVEL WAVE. AS THESE FEATURES HEAD EASTWARD WITH NOCTURNAL COOLING / STABILIZING AND SOME DRYING THROUGH THE COLUMN... EXPECT THE DOWNWARD TREND IN CONVECTION COVERAGE AND INTENSITY TO CONTINUE. WILL TREND POPS DOWN GRADUALLY WEST TO EAST FOR THE NEXT SEVERAL HOURS... FOLLOWING THE CONSENSUS OF THE LATEST HIGH-RES GUIDANCE AND OBSERVATIONS. THE RAIN-COOLED AIR SHOULD CONTINUE TO DRAW THE SYNOPTIC FRONT SOUTHWARD THROUGH NRN NC OVERNIGHT... DROPPING TEMPS DOWN TO LOWS IN THE UPPER 50S TO AROUND 60 NORTH OF HIGHWAY 64... WITH LOWER TO MID 60S TO ITS SOUTH. LOW CLOUDINESS WILL CONTINUE TO SPREAD SOUTHWARD THROUGH CENTRAL NC LATE TONIGHT... RESULTING IN CLOUDY SKIES ACROSS ALL BUT PERHAPS THE EXTREME SOUTH BY DAYBREAK... WITH PATCHY FOG AS WELL. -GIH && .LONG TERM /SATURDAY THROUGH THURSDAY/... AS OF 340 PM THURSDAY... A BROAD UPPER LEVEL TROUGH WILL INITIALLY COVER THE LOWER 48 SATURDAY. THIS WILL TRANSITION TO AN AMPLIFIED RIDGE OVER THE WESTERN U.S. AND AN TROUGH OVER THE EASTERN U.S. FORECAST CONFIDENCE IS LOWER THAN NORMAL DUE TO THIS TRANSITION AS MODELS USUALLY HAVING DIFFICULTY RESOLVING WHICH PARTICULAR S/W WILL CAUSE AN ENHANCED CHANCE OF PRECIP TO A GIVEN REGION. SINCE WEDNESDAY...THE MODELS HAVE SPED UP THE RETURN FLOW OF MOISTURE INTO CENTRAL NC SATURDAY INTO SATURDAY NIGHT AS THE S/W RIDGE SCOOTS QUICKLY EAST SATURDAY MORNING. THIS LOW LEVEL WARM AIR ADVECTION COUPLED WITH A SERIES OF DISTURBANCES ALOFT WILL INCREASE RAIN CHANCES SW-NE ACROSS CENTRAL NC SATURDAY AFTERNOON INTO SATURDAY NIGHT. WHILE A SHORT-LIVED HYBRID/INSITU DAMMING EVENT MAY OCCUR SATURDAY AFTERNOON-SATURDAY EVENING... MODEL GUIDANCE NOW SUGGESTING THAT A WARM FRONT WILL LIFT ACROSS THE AREA SATURDAY NIGHT...PLACING CENTRAL NC SOLIDLY IN THE WARM SECTOR ON SUNDAY. THUS HAVE ADJUSTED MAX TEMPS UP SEVERAL DEGREES FROM EARLIER FORECAST AND BACKED SFC WINDS TO A SWLY DIRECTION. S/W IN THE NORTHERN STREAM WILL DRAG A WEAK COLD FRONT ACROSS CENTRAL NC LATE MONDAY AND MONDAY NIGHT...BRINGING ANOTHER THREAT FIR SCATTERED CONVECTION. NELY LOW LEVEL FLOW WILL ADVECT A COOLER AND MORE STABLE AIR MASS TUESDAY LEADING TO PLENTY OF CLOUD COVER AND COOLER DAYTIME TEMPS. -WSS AMPLIFYING RIDGE OVER THE WESTERN CONUS WILL ALLOW FOR A DIGGING TROUGH OVER THE EASTERN CONUS WITH A DEVELOPING UPPER LEVEL FEATURE TO OUR SOUTH. GFS SHOWS A SURFACE LOW PRESSURE SYSTEM DEVELOPING OVER PORTIONS OF NORTHERN FL ON TUE AFTERNOON. ECMWF SHOWS A MUCH STRONGER BUT MUCH SLOWER DEVELOPING DISTURBANCE OVER THE MS VALLEY. WITH THE CURRENT PATTERN AND SLOW MOVEMENT OF THE ECMWF... THE GFS SEEMS TO BE THE MORE REALISTIC SOLUTION AT THIS TIME ALTHOUGH CONFIDENCE IS LOW. THE LOW WILL LIKELY DEVELOP AND MOVE NORTHWARD ALONG THE COAST FOR WED NIGHT INTO THU. GUIDANCE SUGGESTS EASTERLY AND NORTHEASTERLY WINDS IN ASSOCIATION WITH THE LOW PRESSURE SYSTEM. THE WEATHER PATTERN ASSOCIATED WITH THIS LOW COULD BRING SOME ISENTROPIC UPGLIDE ALONG WITH INCREASE RAIN CHANCES FOR WED NIGHT AND INTO THU MORNING WITH POPS TAPERING OFF AS THE DISTURBANCE MOVES NORTHEASTWARD. TEMPS ARE CURRENTLY FORECASTED TO BE 5 TO 8 BELOW CLIMO ON WED WITH INCREASING CLOUD COVER AND MOISTURE ADVECTION OFF OF THE ATLANTIC. THE COLD AIR ADVECTION ASSOCIATED WITH THIS COULD BE LIGHT ENOUGH TO ALLOW FOR TEMPERATURES TO GET CLOSER TO CLIMO. CLOUD COVER COULD LIMIT THE CURRENT FORECAST LOWS... HOWEVER GFS SUGGESTS LOW LEVEL COLD AIR ADVECTION CONTINUING WED NIGHT. -JLB && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... AS OF 815 PM THURSDAY... CLUSTERS OF SHOWERS AND STORMS OVER THE NORTHERN PIEDMONT AND NORTHERN COASTAL PLAIN WILL SLOWLY DIMINISH THROUGH 04Z/MIDNIGHT LOCAL TIME. IN VICINITY OF THE HEAVIER SHOWERS AND STORMS...EXPECT A BRIEF PERIOD OF MVFR CONDITIONS. AFTER 06Z...POCKETS OF MVFR/IFR CEILINGS AND FOG WILL DEVELOP...MAINLY IN VICINITY OF KRDU AND KRWI. ELSEWHERE...BRIEF INTERVALS OF MVFR/IFR FOG AND/OR CEILINGS WILL OCCUR BETWEEN 09Z-13Z. AFTER 14Z...EXPECT CLOUD BASES TO LIFT AND SCATTER BY MID-LATE MORNING AS DRIER AIR INFILTRATES THE REGION...RESULTING IN VFR CONDITIONS. THE OPTIMAL AVIATION CONDITIONS WILL BE SHORT IN DURATION AS A QUICK RETURN FLOW OF MOISTURE WILL ADVANCE OVER THE PIEDMONT SATURDAY MORNING. THIS WILL LEAD TO THICKENING LOWER CLOUD DECK AND SPOTS OF LIGHT RAIN DEVELOPING SATURDAY AFTERNOON. ADVERSE AVIATION CONDITIONS EXPECTED TO BE WIDESPREAD ACROSS CENTRAL NC SATURDAY NIGHT THROUGH EARLY SUNDAY DUE TO LOW CLOUDS AND WIDESPREAD RAIN. WARMER AIR WILL MAKE A RETURN SUNDAY AND MAINTAIN A THREAT OF SCATTERED CONVECTION ALONG WITH PERIODS OF MVFR CEILINGS SUNDAY AFTERNOON THROUGH TUESDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...CBL NEAR TERM...HARTFIELD SHORT TERM...CBL LONG TERM...WSS/JLB AVIATION...WSS

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