Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 020715 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 315 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/...
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AS OF 315 AM TUESDAY... CIRCULATION AROUND AN UPPER LEVEL LOW OVER THE TN VALLEY AND AN UPPER LEVEL RIDGE OFFSHORE OF THE CAROLINA COAST WILL MAINTAIN A DEEP SLY FLOW OVER CENTRAL NC THROUGH THE SHORT TERM. WATER VAPOR IMAGERY DEPICTS A PLUME OF MOISTURE ORIGINATING IN THE WESTERN CARIBBEAN BEING LIFTED NWD IN THIS SLY FLOW. THIS SET-UP WILL MAINTAIN A MOISTURE-RICH AIR MASS OVER CENTRAL NC WITH PRECIP WATER VALUES HOVERING BETWEEN 1.7-1.9 INCHES (ABOUT 150 PERCENT ABOVE NORMAL FOR THIS TIME OF YEAR). LIFT THROUGH THE ATMOSPHERE WILL BE SUPPLIED BY A SERIES OF VORTICIES ROTATING AROUND THE UPPER LEVEL LOW...AS WELL AS AN AREA OF UPPER DIVERGENCE IN RESPONSE TO A UPPER JET EXITING OFF THE MID ATLANTIC COAST. THE LIFT WILL BE FURTHER ENHANCED BY AFTERNOON HEATING. ONE SUCH VORTICITY DEPICTED BY NEAR TERM MODELS (THOUGH DIFFICULT TO DISCERN IN WATER VAPOR IMAGERY) IS EXPECTED TO LIFT NWD THROUGH WESTERN NC THIS MORNING WITH ITS SHEAR AXIS CROSSING OUR REGION THIS AFTERNOON. THIS FEATURE EXPECTED TO TRIGGER A CLUSTER OF SHOWERS LATER THIS MORNING OVER THE SOUTHERN AND WESTERN PIEDMONT WHILE THE SHEAR AXIS WILL LIKELY BE A FOCUS FOR SCATTERED-NUMEROUS SHOWERS AND STORMS THIS AFTERNOON...MAINLY OVER THE EAST HALF OF OUR FORECAST AREA. DUE TO THE AVAILABLE MOISTURE...EXPECT RAINFALL RATES ON THE ORDER OF 1-2 INCHES PER HOUR IN THE HEAVIER SHOWERS/STORMS. WHILE NOT ANTICIPATING WIDESPREAD AMOUNTS OF THIS MAGNITUDE... WHERE SHOWERS TRAIN ACROSS THE SAME LOCATION COULD QUICKLY LEAD TO NUISANCE TYPE FLOODING OF STREETS AND LOW LYING AREAS...LIKELY PROMPTING A FEW URBAN/SMALL STREAM FLOOD ADVISORIES. BULK SHEAR EXPECTED TO BE A LITTLE STRONGER THIS AFTERNOON-EARLY EVENING THAN WHAT OCCURRED MONDAY AFTERNOON BUT STILL BELOW THRESHOLDS TYPICAL FOR STRONG/SEVERE CONVECTION. MEANWHILE LOW LEVEL INSTABILITY CHARACTERIZED AS WEAK. BULK OF STORMS EXPECTED TO BE BELOW SEVERE CRITERIA THOUGH CANNOT RULE OUT A STRONG/SEVERE STORM OR TWO ACROSS THE REGION WITH THE PRIMARY THREAT OF LOCALLY DAMAGING DOWNBURST WINDS. SINCE EXPECTING AREAS OF SHOWERS TO COMMENCE SOONER THAN MONDAY AND CLOUDS SHOULD BE MORE EXTENSIVE AS WELL...HIGH TEMPS TODAY SHOULD AVERAGE 7-10 DEGREES COOLER THAN MONDAY. MAX TEMPS UPPER 70S TO AROUND 80 NW TO THE LOWER 80S SOUTHEAST. TONIGHT...AREAS OF SHOWERS AND STORMS EXPECTED TO SLOOOOWLY DIMINISH OVERNIGHT AS A SFC COLD FRONT DRIFTS SWD INTO OUR AREA FROM SOUTHERN VA. IN THEIR WAKE...EXPECT PATCHES OF FOG TO DEVELOP THOUGH DENSE FOG APPEARS TO BE A LOW PROBABILITY DUE TO EXTENSIVE CLOUDINESS AND THE WARM ATMOSPHERE. MIN TEMPS IN THE MID-UPPER 60S.
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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
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AS OF 315 AM TUESDAY... ATMOSPHERE CHANGES LITTLE WEDNESDAY/WEDNESDAY NIGHT DUE TO THE NEARLY STATIONARY UPPER LOW TO OUR WEST AND THE RIDGE TO OUR EAST. LOBES OF VORTICITY ROTATING AROUND THE LOW WILL CAUSE PERIODS OF SHOWERS AND STORMS WITH COVERAGE ENHANCED BY AFTERNOON HEATING. SIMILAR TO TODAY...RAINFALL RATES OF 1-2 INCHES PER HOUR MAY LEAD TO NUISANCE FLOODING OF STREETS/LOW LYING AREAS. SINCE FLOODING IS EXPECTED TO BE MINOR AND LIMITED IN SCOPE...NOT ANTICIPATING THE NEED FOR A FLOOD WATCH AT THIS TIME. NEAR SFC NELY FLOW BEHIND THE SLOW MOVING SFC COLD FRONT THAT SHOULD IN VICINITY OF HIGHWAY 64 WILL ADVECT SLIGHTLY COOLER AIR INTO THE NORTHERN COUNTIES. THIS LOW LEVEL CAA ALONG WITH PERIODS OF SHOWERS AND EXTENSIVE CLOUDINESS WILL RESULT IN HIGH TEMPS IN THE 70S OVER MOST OF THE REGION WITH NEAR 80/LOWER 80S CONFINED TO THE FAR SOUTH-SE. THE THREAT FOR SHOWERS AND STORMS WILL CONTINUE INTO WEDNESDAY NIGHT THOUGH COVERAGE SHOULD BEGIN TO WANE AFTER 03Z-05Z AS ATMOSPHERE UNDERGOES USUAL NOCTURNAL STABILIZATION. MIN TEMPS LOWER 60S NORTH TO MID 60S SOUTH.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 250 AM TUESDAY... THURSDAY THROUGH FRIDAY NIGHT: SURFACE HIGH PRESSURE IS EXPECTED TO EXTEND SOUTHWARD AND INTO PORTIONS OF CENTRAL NC STILL ON THURSDAY. HOWEVER... THE CENTER OF THE HIGH IS EXPECTED TO BE MOVING OFF THE NORTHEAST U.S. COAST ON THURSDAY. THIS SHOULD YIELD A MODERATING AIRMASS SOME. HOWEVER... WITH PLENTIFUL MOISTURE AND A LINGERING NORTHERLY FLOW OVER MOST OF THE AREA EXPECT WE WILL ONCE AGAIN SEE BELOW NORMAL TEMPS ACROSS CENTRAL NC... WITH HIGHS RANGING FROM THE LOWER TO MID 70S NW TO THE LOWER 80S SE. THE MID LEVEL LOW ON THURSDAY WILL SLOWLY WOBBLE EASTWARD FROM THE NC MOUNTAINS AND EVENTUALLY MAKE IT TO THE COASTAL PLAIN ON FRIDAY. THIS SHOULD CONTINUE TO GIVE US A GOOD CHANCE OF SHOWERS AND STORMS ON THURSDAY INTO THURSDAY EVENING (SCATTERED TO NUMEROUS)... WITH THE BETTER CHANCES ON FRIDAY ACROSS THE EASTERN HALF OF THE FORECAST AREA AS THE MID LEVEL LOW MOVES ACROSS THE CWA. HOWEVER... OVERALL DEEP SHEAR WILL REMAIN WEAK... WITH SURFACE INSTABILITY WEAK TO MODEST AT BEST. THUS... ANY SEVERE THREAT SHOULD REMAIN ISOLATED DURING THIS TIME... WITH LOCALIZED FLASH FLOODING (ESPECIALLY IN URBAN AREAS AND LOCATIONS THAT HAPPEN TO RECEIVE SEVERAL ROUNDS OF HEAVY PRECIP) BEING THE MAIN HAZARDOUS WEATHER THREAT DURING THIS TIME FRAME. TEMPS SHOULD REBOUND A BIT ON FRIDAY WITH A CONTINUED MODERATING AIRMASS... WITH HIGHS GENERALLY IN THE LOWER 80S. LOWS THURSDAY AND FRIDAY NIGHT GENERALLY IN THE MID 60S. SATURDAY THROUGH MONDAY: UNSETTLED FORECAST CONTINUES INTO NEXT WEEKEND. WITH THE PASSAGE OF A NORTHERN STREAM DISTURBANCE TO THE NORTH OF THE AREA ON FRIDAY NIGHT INTO SATURDAY... ANOTHER TRAILING OR BACKDOOR COLD FRONT MAY AGAIN SINK SOUTHWARD INTO CENTRAL NC. THIS COMBINED WITH A CONTINUED WEAK MID LEVEL TROUGH REMAINING ACROSS THE REGION AND POSSIBLY ADDITIONAL S/W ENERGY DROPPING SOUTHEASTWARD AND INTO THE BACK SIDE OF THE WEAK MID LEVEL TROUGH OVER THE AREA (AS SHOWN ON THE LATEST ECWMF... WHICH WOULD ENHANCE COVERAGE OF SHOWERS AND STORMS EVEN MORE) SHOULD RESULT IN AT LEAST CHANCES FOR AFTERNOON AND EVENING SHOWERS AND STORMS. STILL A LITTLE TO EARLY TO TELL HOW FAR SOUTH THIS POSSIBLE FRONT WILL MAKE IT. THUS... WILL CONTINUE TO STICK CLOSE TO WPC FOR TEMPS...WITH HIGH TEMPS NEAR TO SLIGHTLY BELOW NORMAL FOR EARLY JUNE AND LOWS NEAR NORMAL. YET ANOTHER DISTURBANCE IS EXPECTED TO TRACK FROM THE CENTRAL AND NORTHERN PLAINS ON SATURDAY INTO THE GREAT LAKES REGION BY LATE SUNDAY INTO MONDAY MORNING. THIS WILL EVENTUALLY SEND ANOTHER FRONT TOWARDS CENTRAL NC LATE MONDAY FROM THE WEST. THUS... WILL CONTINUE TO KEEP CHANCE POPS IN FOR DAY 7 IN THE FORECAST WITH NEAR NORMAL TEMPS. && .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...WSS SHORT TERM...WSS LONG TERM...BSD AVIATION...WSS

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