Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 170608 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 207 AM EDT THU APR 17 2014 .SYNOPSIS...
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UNSEASONABLY STRONG...POLAR HIGH PRESSURE WILL BUILD SOUTH FROM NEW ENGLAND TODAY...THEN LINGER THROUGH FRIDAY. MEANWHILE...LOW PRESSURE WILL DEVELOP OVER THE NORTHEASTERN GULF OF MEXICO FRIDAY...THEN MEANDER ALONG THE SOUTHEAST US COAST THROUGH THE WEEKEND.
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&& .NEAR TERM /THROUGH THURSDAY/... AS OF 1000 PM WEDNESDAY... PRESSURE READINGS CONTINUE TO RISE ACROSS CENTRAL NC THIS EVENING AS A STRONG 1036MB SURFACE HIGH OVER NEW ENGLAND REACHES DOWN THE EAST COAST. THE MAIN STORY FOR THE OVERNIGHT PERIOD IS THE POTENTIAL FOR FREEZE AND FROST. WINDS HAVE DECOUPLED IN SOME SPOTS...BUT THE BUILDING SURFACE RIDGE IS KEEPING A LIGHT WIND STIRRING OVER MOST OF THE AREA. SHOULD SEE MORE AREAS DECOUPLE BY AFTER MIDNIGHT...ESPECIALLY ACROSS WESTERN AREAS. HOWEVER...THE PRESSURE GRADIENT IS FORECAST TO TIGHTEN A BIT OVER EASTERN NC BY 09Z IN RESPONSE TO A WESTWARD MIGRATING INVERTED TROUGH OFFSHORE...AND THE RATE AT WHICH TEMPS FALL OVER THE COASTAL PLAIN WILL SLOW AS THE RIDGE AXIS SETTLES TOWARD THE PIEDMONT. COULD ISSUE A FROST ADVISORY FOR THE COASTAL PLAIN...BUT RAP SOUNDINGS SHOW THE BOUNDARY LAYER STAYING AT LEAST PARTIALLY MIXED THROUGHOUT THE NIGHT...AND THE FROST SHOULD REMAIN PATCHY IN NATURE. THE FREEZE WARNING WILL CONTINUE AS FORECAST. IR SATELLITE IMAGERY SHOWS QUITE A BIT OF STRATO CU OFFSHORE...WHICH WILL BEGIN TO SPREAD INLAND LATE TONIGHT AND TOWARD THE I-95 CORRIDOR DURING THE MID-MORNING HOURS ON THURSDAY. -SMITH THURSDAY...CIRCULATION AROUND THE LOW LEVEL RIDGE WILL RESULT IN A LONG NE FETCH OFF THE ATLANTIC INTO EASTERN NC. THIS FLOW WILL TRANSPORT A SHALLOW THIN LAYER OF MOISTURE INTO THE COASTAL PLAIN...RESULTING IN A SCATTERED TO BRIEFLY BROKEN LAYER OF STRATOCU OVER THE COASTAL PLAIN LATER THURSDAY MORNING INTO THURSDAY AFTERNOON. LAYER TOO SHALLOW TO SUPPORT ANYTHING MORE THAN SPRINKLES IF EVEN THAT. TEMPS WILL REMAIN WELL BELOW NORMAL FOR MID APRIL THOUGH SOME RECOVERY COMPARED TO TODAY ANTICIPATED. AFTERNOON THICKNESSES PROJECTED TO BE ABOUT 20M WARMT THAN THIS AFTERNOON WHICH SUGGEST AFTERNOON TEMPS THURSDAY ABOUT 5 DEGREES WARMER THAN THIS AFTERNOON. THIS IS MORE SIMILAR TO THE COOLER GFS MOS GUIDANCE. MAX TEMPS UPPER 50S TO LOWER 60S. && .SHORT TERM /THURSDAY NIGHT AND FRIDAY /... AS OF 330 PM WEDNESDAY... THURSDAY NIGHT AND FRIDAY....SFC RIDGE AXIS WILL LIKELY MAINTAIN ITS INFLUENCE OVER THE PIEDMONT OF CENTRAL NC THROUGH THIS PERIOD AS PARENT HIGH BECOMES ANCHORED OVER NORTHERN NEW ENGLAND/CANADIAN MARITIME DUE TO CONFLUENT FLOW ALOFT. WHILE THE AIR MASS UNDERNEATH THIS RIDGE WILL GRADUALLY MODIFY...PRESENCE OF DRY AIR UNDER THIS WEATHER SYSTEM WILL MAINTAIN A BASICALLY CLOUD FREE ATMOSPHERE IN THE LOWEST 10K FEET. MEANWHILE...A S/W IS PROJECTED TO MOVE EAST-SE ACROSS THE CENTRAL NC PLAINS AND INTO THE TN VALLEY WHERE IT IS PROJECTED TO BEGIN TO INTERACT WITH A SYSTEM LIFTING E-NE ACROSS THE NORTHERN GULF. UPPER LEVEL FLOW OVER THE CAROLINAS WILL BACK IN RESPONSE TO THE APPROACH OF THESE SYSTEMS...TRANSPORTING HIGH LEVEL MOISTURE INTO OUR REGION. THIS SHOULD RESULT IN AN INCREASING VEIL OF HIGH CLOUDS THURSDAY NIGHT INTO FRIDAY. THE THICKNESS OF THESE HIGH CLOUDS WILL PLAY A ROLE IN WHETHER SCATTERED FROST WILL DEVELOP OVER THE PIEDMONT THURSDAY NIGHT/EARLY FRIDAY. IN ADDITION...LOW LEVEL ELY FLOW WILL ADVECT MOISTURE OFF THE ATLANTIC INTO THE COASTAL PLAIN BY FRIDAY MORNING. MIN TEMPS MID 30S WEST TO UPPER 30S/AROUND 40 EAST. SHOULD SEE AT A MINIMUM A MIXTURE OF SUN AND CLOUDS FRIDAY WITH THE CHARACTER OF THE SKY BECOMING MOSTLY CLOUDY OR OVERCAST BY FRIDAY AFTERNOON. ISENTROPIC UPGLIDE DOES NOT APPEAR STRONG ENOUGH TO SUPPORT PRECIP FRIDAY AFTERNOON...ASIDE FROM A STRAY SHOWER ACROSS THE FAR SE. AIR MASS WILL CONTINUE TO GRADUALLY MODIFY BUT AFTERNOON TEMPS WILL REMAIN WELL BELOW NORMAL. MAX TEMPS 60-65. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... AS OF 3 PM WEDNESDAY... FRIDAY NIGHT THROUGH SUNDAY NIGHT: THE WEEKEND FORECAST CONTINUES TO HAVE SOME UNCERTAINTY WITH REGARD TO THE EVOLUTION OF A POSSIBLE CLOSED LOW LINGERING ACROSS THE SOUTHEASTERN U.S/OFFSHORE. WHILE THE NORTHERN STREAM ENERGY IS PROGRESSIVE AND PUSHES EASTWARD FRIDAY NIGHT INTO SATURDAY. IN ADVANCE OF THE NORTHERN STREAM TROUGH BOTH THE 12Z GFS AND ECMWF PULLS MOISTURE NORTHWARD... AND PRODUCED SOME LIGHT RAIN ACROSS OUR FAR SOUTHEAST/EAST ON FRIDAY NIGHT INTO EARLY SATURDAY MORNING... WITH THE BULK OF THE PRECIP EXPECTED TO BE TO OUR EAST AND SOUTH. HOWEVER... MODEL GUIDANCES IS STRUGGLING WITH WHAT WILL HAPPEN WITH THE LINGERING SOUTHERN STEAM ENERGY THAT POSSIBLY CLOSES OFF INTO A CLOSED LOW AND LINGERS NEAR FL AND OFF THE SOUTHEAST U.S. COAST. THE 12Z ECMWF HAS COME A MORE IN THE LINE WITH THE 12Z GFS IN SHOWING LINGERING MID LEVEL ENERGY SLOWLY SHIFTING EASTWARD AND FAR ENOUGH AWAY FROM THE COAST TO KEEP US DRY SATURDAY AFTERNOON THROUGH THE REST OF THE WEEKEND. HOWEVER... GUIDANCES HAS SHOWN POOR RUN TO RUN CONTINUITY. THUS... CONFIDENCE IS NOT HIGH THAT LATE SATURDAY INTO SUNDAY THAT WE WILL BE COMPLETELY DRY AT THIS TIME ACROSS OUR ENTIRE AREA (IF PRECIP LINGER... LOCATIONS ACROSS THE EAST/SOUTHEAST WOULD SEE THE BEST CHANCE/MOST). FOR NOW WILL GO WITH A DRY FORECAST AS MENTIONED ABOVE FROM SATURDAY AFTERNOON ONWARD. WITH SURFACE HIGH PRESSURE BUILDING INTO THE AREA FROM THE NORTH AND A COOL EAST TO NORTHEASTERLY LOW LEVEL FLOW EXPECT HIGH TEMPS WILL REMAIN SLIGHTLY BELOW NORMAL WITH AT LEAST SOME CLOUD COVER (MORE EAST VS WEST). THUS... WILL GO WITH HIGH TEMPS THIS WEEKEND IN THE UPPER 60S TO LOWER 70S... WITH LOW TEMPS IN THE 40S TO LOWER 50S. MONDAY THROUGH WEDNESDAY: NEXT MID LEVEL DISTURBANCE IS EXPECTED TO CROSS THE REGION ON TUESDAY... ALONG WITH A WEAK SURFACE TROUGH. HOWEVER... WITH LACK OF ANY SIGNIFICANT MOISTURE RETURN WILL KEEP POPS LOW AT THIS TIME. TEMPS EARLY TO MID NEXT WEEK ARE EXPECT TO WARM AGAIN... WITH HIGHS IN THE 70S AND LOWS IN THE 50S. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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AS OF 200 AM THURSDAY... UNSEASONABLY STRONG/POLAR HIGH PRESSURE WILL RIDGE SOUTH FROM NEW ENGLAND AND RESULT IN CLEAR/VFR CONDITIONS THIS MORNING...WHICH WILL YIELD TO BOTH INCREASING CIRRUS IN SW FLOW ALOFT FROM THE WEST...AND A BRIEF PERIOD OF SCT TO PERHAPS EVEN BKN STRATOCUMULUS BETWEEN 2500- 4000 FT MAINLY AT EASTERN TERMINALS BETWEEN MID-MORNING THROUGH EARLY AFTERNOON. THE SURFACE RIDGE WILL ALSO MAINTAIN A NORTHEASTERLY SURFACE WIND OVER CENTRAL NC...STRONGEST AND OCCASIONALLY GUSTY INTO THE UPPER TEENS KTS AT EASTERN TERMINALS... ALSO FROM MID-MORNING TO EARLY AFTERNOON. OUTLOOK: A LOW PRESSURE SYSTEM WILL DEVELOP AND LINGER OFFSHORE THE SOUTHEAST US COAST LATE FRI THROUGH THE WEEKEND...AND THIS SYSTEM MAY RESULT IN RAIN AND SUB-VFR CONDITIONS AT KFAY/KRWI/KRDU FRI NIGHT-SAT. FORECAST CONFIDENCE REMAINS BELOW AVERAGE REGARDING THE TRACK OF THE LOW AND ASSOCIATED IMPACTS OVER CENTRAL NC...HOWEVER.
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&& .CLIMATE...
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THE FOLLOWING ARE THE RECORD LOW TEMPERATURES FOR THIS MORNING: THU 04/17 LOW/YEAR FAY: 31/1953 GSO: 29/1953 RDU: 29/1962
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&& .RAH WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT THURSDAY FOR NCZ007>011-021>027-038>041-073>077-083>086. && $$ SYNOPSIS...MWS NEAR TERM...WSS/SMITH SHORT TERM...WSS LONG TERM...BSD AVIATION...MWS CLIMATE...MWS

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