Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 250810 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 409 AM EDT SAT APR 25 2015 .SYNOPSIS...A WARM FRONT WILL MOVE INTO THE AREA AND STALL TODAY. AN AREA OF LOW PRESSURE WILL APPROACH FROM THE WEST THIS EVENING AND CROSS THE AREA OVERNIGHT...FOLLOWED BY A COLD FRONT ON SUNDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 340 AM SATURDAY... HIGH CLOUDS CONTINUE TO THICKEN ACROSS THE AREA THIS MORNING AHEAD OF A SHORTWAVE AND ASSOCIATED LOW PRESSURE MOVING INTO THE MID- MISSISSIPPI VALLEY REGION. AN AREA OF RAIN DRIVEN BY WARM ADVECTION IS MOVING THROUGH THE LOWER TENNESSEE VALLEY REGION AND WILL ENCROACH UPON THE WESTERN PIEDMONT AFTER SUNRISE...THOUGH THE ATMOSPHERE OVER CENTRAL IS VERY DRY WITH PW AROUND A QUARTER OF AN INCH ON THE 00Z KGSO RAOB. VIRGA SHOULD GIVE WAY TO A WIDESPREAD LIGHT RAIN IN THE WEST BY MID-MORNING AND CONTINUE TO THE EAST THROUGH EARLY AFTERNOON. THE CHANCE OF THUNDER LOOKS PRETTY LOW WITH THE INITIAL BAND OF PRECIP DUE TO WEAK LAPSE RATES AND LIMITED HEATING. A WARM FRONT WORKING NORTH THROUGH SC THIS AFTERNOON SHOULD END UP SOMEWHERE ACROSS SOUTHERN NC THIS EVENING...WITH ITS NORTHWARD PUSH HAMPERED BY THE LIGHT RAIN AND RESULTING COOL POOL OVER THE PIEDMONT. MEANWHILE...A DRY SLOT WILL SPREAD ACROSS THE REGION...BRINGING THE INITIAL PRECIP TO AN END BUT ALSO CREATING SOME POTENTIAL INSTABILITY WHICH WOULD HELP STEEPEN MID-LEVEL LAPSE RATES THIS EVENING AS THE REMNANTS OF THE AFOREMENTIONED SHORTWAVE AND ASSOCIATED 60-80M HEIGHT FALLS CROSS THE AREA. FORECAST SOUNDINGS SHOW THE INCREASE IN AT LEAST SOME WEAK MUCAPE ACROSS SOUTHERN NC BY 00Z. WITH STRONG WESTERLIES ALOFT AND 50-60KT OF BULK SHEAR...THE BIGGEST QUESTION WILL THEN BE THE COVERAGE OF CONVECTION APPROACHING FROM THE NORTHWEST AND WHETHER OR NOT WILL CAN BECOME SURFACE BASED...AND LATEST MODEL GUIDANCE SUGGESTS SBCAPE WILL BE NEGLIGIBLE. CURRENTLY...FORECAST CONFIDENCE IS LOW REGARDING SEVERE WEATHER...BUT THERE APPEARS TO BE ENOUGH POTENTIAL TO ADD A CHANCE OF THUNDER ACROSS THE SOUTH AND ADD SOME WORDING TO THE HWO. LATEST MODEL RUNS SHOW A LITTLE BETTER AGREEMENT REGARDING QPF...WITH THE BETTER POTENTIAL FOR A THIRD TO A HALF INCH ACROSS THE SOUTH IN CLOSER PROXIMITY TO THE WARM FRONT. AS FOR TEMPS...THE CURRENT FORECAST LOOKS PRETTY GOOD IN SHOWING A STRONG GRADIENT FROM WEST TO EAST BASED OF THE TIMING OF PRECIP AND ANTICIPATED IN-SITU DAMMING....WITH LOW/MID 50S WEST AND LOW/MID 60S EAST. TEMPS WILL ONLY FALL A FEW DEGREES TONIGHT AS MOST OF THE AREA REMAINS SOCKED IN WITH ABUNDANT LOW CLOUDS AND SOME AREAS OF FOG...UPPER 40S NORTH TO MID 50S SOUTH. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 340 AM SATURDAY... THE DEAMPLIFYING SHORTWAVE FROM SATURDAY NIGHT AND THE ASSOCIATED SURFACE LOW WILL MOVE EAST OF THE AREA ALONG WITH EARLY SUNDAY BUT WILL BE FOLLOWED BY ANOTHER WAVE ROUNDING THE UPPER LOW WOBBLING EAST ACROSS NEW ENGLAND. A STRONG 850MB FRONT DRAPED ACROSS THE OHIO VALLEY AND MID-ATLANTIC STATES WILL PUSH SOUTH ACROSS NC SUNDAY AFTERNOON...WHICH SHOULD HELP TO ERODE THE LINGER DAMMING COOL POOL AND LOW CLOUDS...BUT IT MAY NOT BE EARLY ENOUGH TO ALLOW FOR MUCH HEATING BEFORE SUNSET. THUS...HIGHS ARE EXPECTED TO AGAIN BE WELL BELOW NORMAL IN THE UPPER 50S AND 60S FOR MUCH OF THE AREA...WITH SOME 70S POSSIBLE ACROSS THE FAR SOUTH. WILL MAINTAIN A CHANCE OF SHOWERS WITH THE FRONT ON SUNDAY...ENDING SUNDAY EVENING. LOWS SUNDAY NIGHT IN THE 40S. && .LONG TERM /MONDAY THROUGH FRIDAY/... AS OF 405 AM SATURDAY... A DEEP...EAST TO WEST-ELONGATED CLOSED LOW WILL MOVE SLOWLY AWAY FROM THE NEW ENGLAND AND SOUTHEAST CANADA COAST...WHILE INDIVIDUAL SHORTWAVES ROTATE AROUND THE LOW IN THE MEAN...ONE OF WHICH WILL PIVOT ACROSS THE MIDDLE ATLANTIC STATES MON-MON NIGHT. THE MODELS GENERALLY SUPPORT THIS SOLUTION OF GLANCING FORCING FOR ASCENT AND STEEPENING MID-LEVEL LAPSE RATES (TO AROUND 6-6.5 C/KM) IN ASSOCIATION WITH THE COLDER MID LEVEL TEMPERATURES ACCOMPANYING THE SHORTWAVE TROUGH...ACROSS CENTRAL AND ESPECIALLY NE NC. WHILE SHOWERS OR SPRINKLES WILL BE POSSIBLE IN ASSOCIATION WITH THE PASSING WAVE OVER CENTRAL-EASTERN VA AND NE NC...IT IS LIKELY THAT THE AFFECT OVER CENTRAL NC WILL SIMPLY BE A PERIOD OF ENHANCED (SCT- BKN) CUMULUS MON AFTERNOON-EVE...WITH RELATIVE GREATEST COVERAGE AND DEPTH OVER THE NE HALF OF THE CWFA. OTHERWISE...THE FLOW IN THE LOW LEVELS WILL BE GENERALLY NE THROUGH TUE...AS HIGH PRESSURE RIDGES EAST FROM THE OH VALLEY - SUPPORTIVE OF BELOW AVERAGE TEMPERATURES IN THE MIDDLE 60S TO LOWER 70S BY DAY AND 40S BY NIGHT. SIGNIFICANT FORECAST UNCERTAINTY REMAINS FOR MID-LATE WEEK...OWING TO THE INTERACTION OF THE AFOREMENTIONED VORTEX MOVING SLOWLY AWAY FROM NEW ENGLAND -AND ASSOCIATED TRAILING CONFLUENT FLOW BENEATH HIGHER LATITUDE BLOCKING- WITH A SOUTHERN STREAM UPPER LOW APPROACHING FROM THE SW US AND PROBABLE NORTHERN STREAM INFLUENCE/AMPLIFICATION FROM SOUTHERN CANADA. THE OVERALL PATTERN WILL FAVOR A SOUTHWARD-SUPPRESSED STORM TRACK/CYCLOGENESIS AND ASSOCIATED FOCUS FOR PRECIPITATION ACROSS THE SOUTHEAST STATES TUE- THU...WITH THE RELATIVE HIGHEST PROBABILITY OF RAIN IN CENTRAL NC LATE WED THROUGH EARLY THU. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... AS OF 145 AM SATURDAY... VFR CONDITIONS EARLY THIS MORNING WITH JUST INCREASING MID AND HIGH CLOUDS THROUGH 12Z. AN AREA OF RAIN ASSOCIATED WITH WARM ADVECTION ACROSS THE LOWER TENNESSEE VALLEY REGION WILL MOVE INTO THE WESTERN PIEDMONT BETWEEN 12Z AND 15Z...THOUGH THE RAIN SHOULD BE LIGHT INITIALLY GIVEN HOW DRY THE AIRMASS IS OVER CENTRAL NC THIS MORNING. CEILINGS WILL STEADILY LOWER TO MVFR FROM WEST TO EAST BY LATE MORNING AND EARLY AFTERNOON...FOLLOWED BY IFR CONDITIONS ARE THE RAIN BECOMES MORE WIDESPREAD. A WARM FRONT IS FORECAST TO LIFT INTO THE SOUTHERN PORTIONS OF THE AREA...POSSIBLY APPROACHING KFAY DURING THE AFTERNOON. THIS MAY OFFER SOME SUPPORT FOR AN ISOLATED THUNDERSTORM FROM KRCZ TO KFAY DURING THE LATE AFTERNOON AND EVENING HOURS. THE PROBABILITY OF THUNDERSTORMS IS MUCH LOWER TO THE NORTH. POOR AVIATION CONDITIONS WILL CONTINUE OVERNIGHT AS CEILINGS ARE LIKELY TO LOWER TO LIFR AND SOME AREAS OF FOG DEVELOP OUTLOOK... ADVERSE AVIATION CONDITIONS ARE EXPECTED TO CONTINUE INTO LATE SUNDAY BEFORE IMPROVING BY MONDAY. THE NEXT CHANCE OF SUB-VFR CONDITIONS WILL BE MIDWEEK. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...22 NEAR TERM...22 SHORT TERM...22 LONG TERM...RAH AVIATION...22

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