Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 251720 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 120 PM EDT SAT APR 25 2015 .SYNOPSIS...
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A WARM FRONT WILL STALL ACROSS CENTRAL NC THIS AFTERNOON AND REMAIN STATIONARY OVERNIGHT AS AN AREA OF LOW PRESSURE TRAVERSES WEST-TO-EAST ACROSS THE REGION. A COLD FRONT WILL CROSS THE AREA ON SUNDAY.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 1030 AM SATURDAY... JUST MINOR ADJUSTMENTS MADE TO THE NEAR TERM FORECAST. MAINLY TO BRING THE RAIN IN JUST A TOUCH FASTER ACROSS THE SW THIRD AND SOME TWEAKS TO HOURLY TEMP TREND BASED ON RAIN ARRIVAL. LOW LEVEL SWLY FLOW AHEAD OF A S/W IN THE MID/UPPER LEVELS WILL INCREASE ISENTROPIC UPGLIDE LATE THIS MORNING THROUGH THE AFTERNOON. RAIN SHIELD NOW ENCROACHING UPON THE SOUTHERN PIEDMONT AT 14Z WILL CONTINUE TO SPREAD NE...MOVING INTO THE TRIANGLE REGION BY MIDDAY... AND MOST OF CENTRAL NC BY EARLY AFTERNOON. 12Z GSO SOUNDING DEPICTS A FAIRLY DRY SUB CLOUD LAYER. THIS SUGGEST A DECENT POTENTIAL FOR EVAPORATIVE COOLING ONCE RAIN SATURATES THE COLUMN. HAVE ADJUSTED HOURLY TEMPS TO TRY TO CAPTURE THE TREND OF TEMPS COOLING A FEW DEGREES ONCE THE RAIN SETS IN. BASED ON EXPECTED RAIN COVERAGE EARLY THIS AFTERNOON...MOST PLACES SHOULD BE IN THE 50S WITH THE LOWER TEMPS ACROSS THE NORTHERN PIEDMONT (LOW-MID 50S) AND 55-60 ACROSS THE SOUTH-SE. BASED ON THE LATEST NEAR TERM MODELS...SHOULD SEE RAIN SHIELD DIMINISH FROM THE SW LATE THIS AFTERNOON (AROUND 21Z) AS DRIER AIR ALOFT ADVECTS INTO THE REGION. WILL RETAIN MENTION OF THUNDER THIS EVENING ACROSS THE FAR SOUTH WITH POTENTIAL FOR STRONG CONVECTION OVER THE TN VALLEY TO DRIFT INTO OUR SOUTHERN COUNTIES AFTER 00Z. WHILE SHEAR MORE THAN SUFFICIENT TO SUPPORT ORGANIZED CONVECTION...LOW LEVEL INSTABILITY APPEARS TO BE SORELY LACKING OVER OUR REGION THIS EVENING WHICH WOULD LIMIT STRONG/SEVERE POTENTIAL. WILL CONTINUE TO MONITOR UPSTREAM CONDITIONS THROUGH THE AFTERNOON. && .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 /18Z SATURDAY THROUGH THURSDAY/...
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AS OF 120 PM SATURDAY... HIGH LIKELIHOOD THAT AVIATION CONDITIONS WILL DETERIORATE TO IFR/LIFR CEILINGS BY LATE THIS AFTERNOON...PERSISTING THROUGH EARLY SUNDAY MORNING. AREAS OF RAIN WILL DIMINISH FROM THE WEST THIS AFTERNOON WITH PATCHES OF FOG AND/OR DRIZZLE IN ITS WAKE. THERE IS LESS THAN A 1-IN-5 CHANCE OF A THUNDERSTORM THIS EVENING THROUGH THE OVERNIGHT HOURS ACROSS THE SOUTHERN COUNTIES. THIS CHANCE APPEARS BEST (BUT STILL NO MORE THAN 1:5) NEAR OR SOUTH OF KFAY. AVIATION CONDITIONS WILL BE SLOW TO IMPROVE SUNDAY WITH WIDESPREAD IFR/MVFR CEILINGS AND THE POSSIBILITY OF A FEW SHOWERS IN THE AFTERNOON-EARLY EVENING...MAINLY ACROSS THE NORTHERN COUNTIES INCLUDING KRWI...KRDU...AND THE TRIAD TERMINALS. CONDITIONS SHOULD IMPROVE SUNDAY NIGHT INTO MONDAY AS A DRIER MORE STABLE AIR MASS INFILTRATES THE REGION. THE VFR CONDITIONS SHOULD PERSIST INTO TUESDAY. A LOW PRESSURE SYSTEM APPROACHING FROM THE SW WILL BRING THE NEXT CHANCE FOR SUB VFR CONDITIONS TO CENTRAL NC WEDNESDAY INTO THURSDAY.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...22 LONG TERM...RAH AVIATION...WSS

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