Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 171318 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 915 AM EDT THU APR 17 2014 .SYNOPSIS...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. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 900 AM THURSDAY... TEMPS HAVE WARMED ABOVE FREEZING THIS MORNING. THUS... THE FREEZE WARNING IS NO LONGER IN EFFECT. TEMPS ARE EXPECTED TO WARM INTO THE LOWER TO MID 60S TODAY WITH AFTERNOON LOW LEVEL THICKNESS VALUES AROUND 20 TO 25 METERS HIGHER TODAY THAN YESTERDAY. AS OF 300 AM THURSDAY... UNSEASONABLY STRONG/1040-1045 MB POLAR HIGH PRESSURE CENTERED OVER MAINE WILL RIDGE SOUTH AND MAINTAIN CONTINUED COOL...BUT INCREASINGLY MODIFIED...NORTHEASTERLY FLOW TODAY. A SOUTHERN STREAM WAVE ALOFT AND ASSOCIATED CIRRUS OVER AL/GA WILL LIFT NORTHEASTWARD ACROSS CENTRAL NC MID-MORNING THROUGH EARLY AFTERNOON. BUFR FORECAST SOUNDINGS HAVE TRENDED LESS AGGRESSIVE WITH THE WESTWARD EXPANSION OF ATLANTIC MOISTURE BENEATH THE ~4000 FT SUBSIDENCE INVERSION EVIDENT ON REGIONAL RAOBS FROM WED. HOWEVER...EARLY MORNING SATELLITE IMAGERY INDICATES A FEW PATCHES OF STRATOCUMULUS HAVE SPREAD INLAND OVER NE SC AND SE NC THIS MORNING...SO SOME OF THIS MOISTURE - TRAPPED BENEATH THE INVERSION ABOVE - IS APT TO AFFECT AT LEAST COASTAL PLAIN COUNTIES FROM MID- MORNING TO EARLY AFTERNOON. DRY ADIABATIC MIXING THROUGH 900 MB...AND ABOUT A 20-25 METER INCREASE IN FORECAST LOW LEVEL THICKNESSES OVER THOSE OF WED...SUPPORT HIGHS MAINLY BETWEEN 60 AND 65 DEGREES. TONIGHT: CHILLY WITH GOOD RADIATIONAL COOLING...PARTICULARLY WITH MAINLY CLEAR SKIES THROUGH MIDNIGHT...FOLLOWED BY THE ARRIVAL OF ADDITIONAL CIRRUS DOWNSTREAM OF ANOTHER SOUTHERN STREAM SHORTWAVE TROUGH OVER NM THIS MORNING. LOWS GENERALLY IN THE MIDDLE TO UPPER 30S. PATCHY FROST WILL CONSEQUENTLY BE POSSIBLE...PARTICULARLY IN RURAL PIEDMONT LOCATIONS.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 315 AM THURSDAY... FRI AND FRI NIGHT: A PAIR OF SOUTHERN STREAM SHORTWAVE TROUGHS OVER NM AND SOUTH TX THIS MORNING ARE FORECAST TO CONSOLIDATE AND FORM A CLOSED LOW OVER THE SOUTHEAST STATES LATE FRI AND FRI NIGHT. SURFACE CYCLOGENESIS WILL RESULT OVER THE NORTHEASTERN GOM AND THE FL PENINSULA...AND WHILE THERE REMAINS LARGER THAN AVERAGE MODEL SPREAD FOR A 36-48 HR FORECAST...THE OVERALL TREND IN NWP GUIDANCE HAS BEEN TOWARD A STRONGER...AND CLOUDIER/WETTER FOR CENTRAL NC...SOLUTION. INDEED...IT NOW APPEARS THAT CONSIDERABLE HIGH CLOUDS EARLY FRI WILL PROGRESSIVELY THICKEN AND LOWER THROUGHOUT THE DAY...SUCH THAT A CHANCE OF RAIN WILL RESULT ALONG OUR SOUTHERN TIER OF COUNTIES BEFORE SUNSET FRI. THE RAIN...IN THE DEFORMATION ZONE OF THE DEVELOPING COASTAL LOW...WILL THEN SPREAD NORTHWARD ACROSS MOST OF THE REST OF CENTRAL NC FRI NIGHT. WHILE LIKELY POPS ARE NOW WARRANTED OVER A LARGE PORTION OF CENTRAL NC...ESPECIALLY SOUTHEASTERN AREAS...IT REMAINS UNCLEAR HOW FAR WEST/INTO THE WESTERN PIEDMONT THE RAIN SHIELD WILL EVOLVE/EXPAND...SO ONLY SMALL/SLIGHT CHANCES OF RAIN WILL BE INDICATED THERE WITH THIS FORECAST CYCLE. THE CLOUDIER/WETTER FORECAST WILL ALSO BE A COOLER THAN PREVIOUSLY THOUGHT ONE...WITH HIGHS IN THE UPPER 50S TO AROUND 60. LOWS 45-50. -MWS SOUTHERN STREAM WAVE CLOSES OFF OVER THE SOUTHEAST ON SATURDAY... BRINGING THE POTENTIAL FOR PRECIPITATION... MORE FAVORED OVER THE COASTAL PLAIN. GFS RUNS ARE MOST AGGRESSIVE WITH BRINGING PRECIP ACROSS THE AREA... HOWEVER THIS SOLUTION IS NOT SUPPORTED BY THE VAST MAJORITY OF ENSEMBLE MEMBERS. INSTABILITY LOOKS MEAGER...WITH NORTHEASTERLY SURFACE FLOW... AND PRECIPITATION WILL BE DRIVEN BY ISENTROPIC LIFT WRAPPING AROUND THE SYSTEM. WITH CLOUD COVER AND NORTHEASTERLY FLOW... EXPECT HIGHS BELOW NORMAL... IN THE LOWER 60S. LOWS IN THE LOW TO MID 40S... WITH ANY LINGERING PRECIPITATION EXITING TO THE EAST. -SEC && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 309 AM THURSDAY... THE UPPER LEVEL LOW EXITS THE SOUTHEAST COAST ON SUNDAY... AND NORTHEASTERLY FLOW WILL CONTINUE BEHIND THE DEPARTING SYSTEM... WITH A GRADUAL DECREASE IN CLOUD COVER FROM WEST TO EAST THROUGH THE DAY. HIGHS IN THE MID TO UPPER 60S. SHORTWAVE RIDGING BUILDS IN BRIEFLY ON MONDAY... BEFORE ANOTHER SOUTHERN STREAM WAVE CROSSES THE AREA LATER TUESDAY INTO EARLY WEDNESDAY... BRINGING A TROUGH/WEAK COLD FRONT THROUGH. AT THIS POINT WILL CAP AT A SLIGHT CHANCE POP FOR TUESDAY AFTERNOON AHEAD OF THE FRONT... AS THE NW FLOW SHOULD NOT SUPPORT MUCH IN THE WAY OF MOISTURE TRANSPORT. UPPER LEVEL RIDGING BUILDS IN TO THE AREA FOR THE LATTER PART OF THE PERIOD... AHEAD OF AN AMPLIFIED WESTERN CONUS TROUGH. TEMPERATURES WILL MODERATE INTO THE LOW 70S ON MONDAY TO MID 70S ON WEDNESDAY... WITH LOWS IN THE LOW 50S. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... AS OF 730 AM THURSDAY... UNSEASONABLY STRONG/POLAR HIGH PRESSURE WILL RIDGE SOUTH FROM NEW ENGLAND AND RESULT IN MOSTLY 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 STRATOCUMULUS BETWEEN 2500-4000 FT MAINLY AT EASTERN TERMINALS FROM 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. && .CLIMATE... THE FOLLOWING ARE THE RECORD LOW TEMPERATURES FOR THIS MORNING: THU 04/17 LOW/YEAR FAY: 31/1953 GSO: 29/1953 RDU: 29/1962 && .RAH WATCHES/WARNINGS/ADVISORIES...
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&& $$ SYNOPSIS...MWS NEAR TERM...BSD/MWS SHORT TERM...MWS/SEC LONG TERM...SEC AVIATION...MWS CLIMATE...MWS

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