Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 060523 RRA AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 125 AM EDT WED MAY 6 2015 .SYNOPSIS...BERMUDA HIGH PRESSURE WILL EXTEND INTO OUR REGION THROUGH MID WEEK. AN AREA OF LOW PRESSURE WILL FORM NEAR THE BAHAMAS AND MEANDER NEAR THE SOUTHEAST COAST THROUGH AT LEAST THE END OF THE WEEK. && .NEAR TERM /TONIGHT/... AS OF 1050 PM TUESDAY... A PERSISTENCE FORECAST WILL BE DIFFICULT TO BEAT...IN A PERSISTENT REGIME OF LOW TO MID LEVEL (SUB-TROPICAL) RIDGING EXTENDING FROM BERMUDA TO THE CAROLINAS. 10 PM TEMPERATURES THIS EVENING WERE NEARLY IDENTICAL TO THOSE OF MON...AND WITH SIMILAR PROJECTED LOW LEVEL THICKNESSES BY 12Z WED...SUSPECT LOWS WILL CONSEQUENTLY BE NEAR TO SLIGHTLY ABOVE TUE MORNING ONES. THE MOST NOTABLE DIFFERENCE BETWEEN THE TWO NIGHTS WILL BE A SHIELD OF HIGH CLOUDS THAT HAS BEEN DEFLECTED WESTWARD INTO THE CENTRAL-EASTERN CAROLINAS IN ASSOCIATION WITH AN UPPER VORT MAX OVER THE NE GOM...WHICH WILL CONTINUE TO EDGE WEST ACROSS CENTRAL NC OVERNIGHT. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 240 PM TUESDAY... A WEAK SURFACE TROUGH WILL STALL TO THE NORTH ON WEDNESDAY NIGHT... WITH HIGH PRESSURE OVER THE NE U.S. AND OFF THE CAROLINA COAST. THE BIGGER FEATURE WILL BE THE CLOSED LOW DEVELOPING OFF THE EAST FLORIDA COAST...WHICH IS EXPECTED TO MOVE NORTH-NORTHEAST TOWARD THE CAROLINAS THROUGH WEDNESDAY NIGHT. FOR NOW...IT APPEARS THAT THE SYSTEM WILL STAY TO THE SOUTH THROUGH WEDNESDAY NIGHT...WITH THE MAIN IMPACT OVER CENTRAL NC BEING INCREASING CLOUDINESS FROM THE SE AND AN INCREASE IN AFT/EVE WINDS. THERE IS A SLIGHT CHANCE FOR SOME SHOWERS/STORMS TO DEVELOP IN THE AFT/EVE ALONG THE STALLED BOUNDARY TO THE NORTH...BUT EXPECT MOST OF THE ACTIVITY TO STAY TO THE NORTH AND NORTHWEST OF CENTRAL NC. WITH LITTLE TO NO CHANGE IN AIRMASS... AND BERMUDA HIGH PRESSURE CONTINUING TO RIDGE INTO THE AREA... EXPECT HIGHS IN THE LOW TO MID 80S. WITH THE INCREASING CLOUDS OVERNIGHT AND SOME WEAK WAA...LOWS WILL BE A FEW DEGREES WARMER THAN PREVIOUS NIGHTS...MAINLY IN THE UPPER 50S. && .LONG TERM /THURSDAY THROUGH TUESDAY/... AS OF 415 PM TUESDAY... THE MAIN FORECAST PROBLEM THROUGH THE PERIOD REMAINS THE EVOLUTION OF AN AREA OF LOW PRESSURE...WITH POSSIBLE SUB-TROPICAL CHARACTERISTICS...FORECAST TO FORM NEAR THE BAHAMAS AND DRIFT NEAR THE SOUTHEAST US COAST THROUGH THE END OF THE WEEK. WHILE TWO MODEL CAMPS REMAIN...WITH SOLUTIONS RANGING FROM THE NCEP ONES ON THE WESTERN SIDE OF THE GUIDANCE ENVELOPE TO MORE EASTERN ONES DEPICTED BY THE NON-NCEP MODELS...THE SPREAD HAS SIGNIFICANTLY DECREASED IN THE PAST 24 HOURS. THE DECREASING MODEL SPREAD RESULTS FROM A WESTWARD SHIFT IN THE NON-NCEP GUIDANCE...INCLUDING THE 12Z OP ECMWF...WHICH YIELDS RELATIVE INCREASED FORECAST CONFIDENCE IN A CLOSER TO THE CAROLINAS COAST MEANDER OF THE LOW THROUGH THE WEEKEND. HOWEVER...NO SOLUTION IS TRULY OFF THE TABLE...SINCE THE STEERING FLOW FOR THE LOW IS FORECAST TO BECOME QUITE WEAK ON THE SOUTHERN PERIPHERY OF A PERSISTENT RIDGE ALOFT OVER THE EAST COAST. IN FACT...THE RIDGE...IN CONJUNCTION WITH AN ELONGATED UPPER LOW ANALYZED THIS MORNING FROM THE SE STATES TO THE YUCATAN CHANNEL...WILL FAVOR THE DEVELOPMENT OF AT LEAST A BRIEF REX BLOCK...WHICH WOULD INDEED FAVOR SLOW AND ERRATIC MOTION OF ANY CYCLONE TRAPPED WITHIN IT. IT WILL LIKELY TAKE A KICKER SHORTWAVE TROUGH TO MIGRATE SLOWLY FROM THE PAC NW TODAY TO THE MS VALLEY EARLY NEXT WEEK TO FINALLY CAUSE THE LOW TO LIFT NE AND AWAY FROM THE NC/VA COASTS EARLY NEXT WEEK. WILL FOLLOW THE WPC-PREFERRED "COMPROMISE" SOLUTION BETWEEN THE TWO MODEL CAMPS INDICATED ABOVE...BEST ILLUSTRATED BY A 12Z GFS/EC BLEND...WHOSE RESPECTIVE MASS FIELDS ARE REALLY NOT TOO DISSIMILAR. THE RESULTANT SENSIBLE WEATHER IMPACTS WILL BE INCREASING CLOUDS AND PROBABILITY OF PRECIPITATION FROM THE SOUTH AND EAST BY LATE THU...WITH THE LATTER PROBABILITIES RANGING FROM CHANCE OVER THE COASTAL PLAIN AND EASTERN SANDHILLS TO SLIGHT CHANCE OVER THE PIEDMONT. WITH THE LOW NEARBY AND FORECAST TO MOVE LITTLE...LIKELY JUST TO THE SOUTH AND EAST OF CENTRAL NC...A PERSISTENCE FORECAST OF SIMILAR POP DISTRIBUTION -HIGHEST CHANCES SE AND LOWEST NW- WILL BE HARD TO BEAT THROUGH THE WEEKEND. PROVIDED THE TIMING OF THE KICKER WAVE REMAINS CONSISTENT...MON MAY BE THE RELATIVE DRIEST DAY OF THE PERIOD IN BRIEF SUBSIDENCE BEHIND THE LOW AND IN ADVANCE OF THE FRONTAL SYSTEM ASSOCIATED WITH THE KICKER WAVE...FORECAST TO ARRIVE ON SUN. TEMPERATURES HAVE BEEN ADJUSTED DOWNWARD...INTO THE 70S MAINLY OVER EASTERN AREAS...GIVEN THE EXPECTATION OF MORE CLOUDS AND HIGHER PRECIPITATION CHANCES WITH THE MORE WESTWARD FORECAST SOLUTIONS FOR THE LOW. IF THE LOW WERE TO STAY OFFSHORE AND FARTHER SE OF NC...THE AIR MASS WOULD SUPPORT LOWER TO MIDDLE 80S...AND SOME UPPER 80S PROBABLE BY TUE. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 125 AM WEDNESDAY... 24-HOUR TAF PERIOD: HIGH CONFIDENCE THAT VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD AS HIGH PRESSURE CONTINUES TO DOMINATE THE WEATHER OVER THE CAROLINAS. THE DEVELOPING LOW PRESSURE SYSTEM NEAR THE BAHAMAS/OFF THE SOUTHEAST COAST WILL BRING PERIODS OF BROKEN CIRRUS OVER THE AREA. LOOKING AHEAD: THE MAIN AVIATION CONCERNS WILL COME LATER IN THE WEEK AND/OR INTO THE WEEKEND AS AN AREA OF LOW PRESSURE DEVELOPS OFF THE SOUTHEAST U.S. COAST. MODELS STILL DIFFER ON THE TRACK/LOCATION AND TIMING OF THIS SYSTEM AS IT PROGRESSES NORTHWARD...POSSIBLY MEANDERING IN THE VICINITY OF THE SE COAST THROUGH EARLY NEXT WEEK. REGARDLESS...THIS SYSTEM COULD RESULT IN SOME ADVERSE AVIATION IMPACTS AS EARLY AS THURSDAY IN WIDESPREAD SHOWERS AND THUNDERSTORMS...AND COULD PERSIST THROUGH SUNDAY...ESPECIALLY ACROSS EASTERN NC. ADDITIONALLY...ENHANCED EASTERLY ONSHORE FLOW FROM THIS SYSTEM COULD BRING AN INCREASE THREAT FOR MORNING STRATUS/FOG. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...RAH NEAR TERM...RAH SHORT TERM...RAH LONG TERM...RAH AVIATION...CBL

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