Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 200157 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 957 PM EDT SUN OCT 19 2014 .SYNOPSIS....HIGH PRESSURE WILL MOVE OVER THE AREA TONIGHT BEFORE SHIFTING EASTWARD OFFSHORE ON MONDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 954 PM SUNDAY... HIGH PRESSURE CURRENTLY OVER WV WILL CONTINUE TO MOVE EASTWARD AND OVER THE AREA TONIGHT. CONSEQUENTLY... LIGHT WINDS AND CLEAR SKIES WILL SET UP IDEAL RADIATIONAL COOLING CONDITIONS. THE ONE POTENTIAL MITIGATING FACTOR IS AN AREA OF HIGH CLOUDS TO THE WEST IN ASSOCIATION WITH A SHORTWAVE OVER THE GREAT LAKES AND A THINNER AREA TO THE SOUTH IN ASSOCIATION WITH THE UPPER JET... HOWEVER GUIDANCE INDICATES THE BRUNT OF THIS MOISTURE WILL REMAIN NORTH AND WEST OF THE AREA... LEAVING JUST A FEW THIN AREAS OF CIRRUS CROSSING THE REGION. WILL CONTINUE WITH LOWS GENERALLY IN THE UPPER 30S TO LOW 40S... WITH THE POTENTIAL FOR MID 30S IN OUTLYING AREAS. PATCHY FROST IS POSSIBLE IN THESE AREAS... MOSTLY CONFINED TO ELEVATED SURFACES. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... AS OF 235 PM SUNDAY... MONDAY...SFC HIGH WILL DRIFT EAST...COMMENCING AIR MASS MODIFICATION. LOW LEVEL RETURN EXPECTED TO BE SWLY BY AFTERNOON WITH OCCASIONAL GUSTS AROUND 15 KTS PROBABLE. LOW LEVEL THICKNESSES REBOUND ABOUT 10M FROM LEVELS OCCURRING THIS AFTERNOON. THIS YIELDS MAX TEMPS 2-3 DEGREES WARMER THAN TODAY. FACTORING IN ADDITIONAL WARMING FROM THE LOW LEVEL SW FLOW SUPPORT MAX TEMPS NEAR 70 TO THE LOWER 70S. MONDAY NIGHT...L/W TROUGH OVER THE EASTERN U.S. UNDERGOES AMPLIFICATION THANKS TO A S/W CROSSING THE GREAT LAKES INTO SOUTHERN NEW ENGLAND. THE TAILE ND OF THIS S/W WILL CROSS CENTRAL NC MONDAY NIGHT...GENERATING AREAS OF MID-HIGH LEVEL CLOUDINESS. WARM AIR ADVECTION IN THE 8000-15000FT LAYER MAY PRODUCE ENOUGH LIFT TO INITIATE SOME PRECIP BUT THE SUB CLOUD LAYER STILL QUITE DRY. THUS...EXPECT NOTHING WORSE THAN A FEW SPRINKLES...MAINLY ACROSS THE NORTH HALF...AS THIS SYSTEM CROSSES OUR REGION. VARIABLE CLOUDINESS AND A MODIFYING AIR MASS WILL RESULT IN MIN TEMPS SEVERAL DEGREES WARMER COMPARED TO TONIGHT. MIN TEMPS IN THE 40S TO AROUND 50. && .LONG TERM /TUESDAY THROUGH SUNDAY/... AS OF 245 PM SUNDAY... FOR TUE-WED: A MID LEVEL VORTEX IS STILL EXPECTED TO DEEPEN OVER LK ERIE AND PUSH SSE THROUGH WRN PA TUE... THEN DROP TO THE DC VICINITY BY WED MORNING... AND WOBBLE NORTHWARD OVER THE MIDATLANTIC COAST WED/WED NIGHT. CYCLONIC SURFACE FLOW SETS UP TUE OVER CENTRAL NC WITH ABOVE NORMAL THICKNESSES AHEAD OF THE CLIPPER COLD FRONT WHICH PUSHES SOUTHEAST THROUGH THE AREA TUE EVENING... INTRODUCING COOLER AIR AS A NOSE OF CANADIAN-SOURCE HIGH PRESSURE BUILDS IN FROM THE NNW. EXPECT CONSIDERABLE MID CLOUDS TO START TUE AS THE 700 MB TROUGH SWINGS THROUGH. THESE SHOULD CLEAR OUT BY LUNCHTIME BUT WILL BE FOLLOWED BY LOWER BROKEN CLOUDS (ENHANCED BY DAYTIME HEATING AND SUBSEQUENT CONVECTIVE TOWERS) ACROSS THE NE AND EAST AS AN ELEVATED MOIST LAYER AT 850-700 MB SWEEPS IN FROM THE NORTH. WITH LITTLE OPPORTUNITY FOR ANY MOISTURE RETURN IN THE LOWER LEVELS... ANY CHANCES FOR PRECIP WITH THE DIGGING VORTEX ALOFT LOOK QUITE LOW. BUT THERE IS AN IMPRESSIVE AMOUNT OF DPVA AS STRONG VORTICITY LOBES ROTATE AROUND THE BASE OF THE LOW... WHICH MAY PARTIALLY COMPENSATE FOR THE RELATIVELY SHALLOW MOISTURE. NORTHEAST SECTIONS OF THE CWA WHERE THE HIGHER SURFACE DEWPOINTS WILL BE TEMPORALLY AND SPATIALLY JUXTAPOSED WITH THE BEST DYNAMIC LIFT MAY STILL SEE A QUICK SPRINKLE TUE EVENING/NIGHT... SO WILL LEAVE IN THE EXISTING SLIGHT CHANCE IN THE NE. THE ENERGY SWINGING THROUGH THE TROUGH BASE WILL CAUSE THE LOW TO SHIFT NE WED... AND WITH JUST WEAKER AND SHEARED VORTICITY DIVING SE OVER CENTRAL NC AND VERY LITTLE MOISTURE THROUGH THE COLUMN... WED SHOULD REMAIN DRY EVEN IN THE NE CWA... ALTHOUGH THIS AREA SHOULD SEE GREATER CLOUD COVERAGE WED. EXPECT WARM HIGHS TUE TO REFLECT THE MILD THICKNESSES... 69-75. LOWS SHOULD SLIP BACK INTO THE 40S AREAWIDE TUE NIGHT POST-FRONT... THEN EXPECT BELOW NORMAL HIGHS OF 62-67 WED AS THICKNESSES DROP BACK INTO THE 1330S... ROUGHLY 25 M BELOW NORMAL. LOWS WED NIGHT 40-45. FOR THU-SUN: THE DRY PATTERN LOOKS VERY LIKELY TO PERSIST. THE SURFACE AND MID LEVEL LOWS TO OUR NE SHIFT FURTHER NE AWAY FROM NC LATE IN THE WORK WEEK AS A PORTION OF THE CANADIAN-SOURCE HIGH BREAKS OFF OVER THE GREAT LAKES AND OH VALLEY AND BUILDS GRADUALLY TOWARD NC FROM THE WNW. LOW LEVEL WINDS REMAIN MOSTLY LIGHT FROM THE NW... AND THE DOWNSLOPE DRYING SHOULD ENSURE DECENT SUNSHINE AND MIXING. EXPECT ANOTHER BELOW-NORMAL DAY THU... WITH HIGHS IN THE MID- UPPER 60S... BUT THEN THICKNESSES ARE EXPECTED TO MODERATE HEADING INTO THE WEEKEND. THE GFS/ECMWF DIFFER WITH THEIR HANDLING OF A WEAK BUT FULL-LATITUDE MID LEVEL TROUGH OVER THE PLAINS THU. THE GFS FOCUSES ON THE NORTHERN PORTION OF THE TROUGH... DRAWING SHORTWAVE ENERGY SOUTHEAST INTO THE VORTEX OFF NEW ENGLAND AND PROGRESSING THE ENTIRE LOW/TROUGH OFF THE COAST BY SAT... FOLLOWED BY STRONG MID LEVEL RIDGING BUILDING OVER TX AND THE GULF STATES SUNDAY. THE ECMWF ON THE OTHER HAND PLACES GREATER IMPORTANCE ON THE SOUTHERN END OF THE PLAINS TROUGH... RESULTING IN A CLOSED LOW OVER ERN TX FRI WHICH THEN DROPS INTO THE NW GULF OVER THE WEEKEND. ALL OF THIS RESULTS IN TWO VERY DIFFERENT LONGWAVE PATTERNS OVER NOAM BY SUN... ALTHOUGH FOR NC... BOTH RESULT IN A FLAT LIGHT NW OR WNW MID LEVEL FLOW WITH NO MECHANISMS TO FORCE ASCENT AND NO REAL CHANCE TO GET ANY DECENT MOISTURE INTO THE AREA WITH HIGH PRESSURE DOMINATING AT THE SURFACE. AS SUCH... WILL KEEP THE FORECAST DRY... WITH TEMPERATURES CREEPING BACK UP JUST ABOVE NORMAL. -GIH && .AVIATION /00Z MONDAY THROUGH FRIDAY/... AS OF 745 PM SUNDAY... VFR CONDITIONS ARE EXPECTED TO CONTINUE FOR THE 24 HOUR TAF PERIOD. AN AREA OF HIGH PRESSURE WILL SETTLE OVERHEAD TONIGHT THEN DRIFT EAST ON MONDAY. THIS WILL LEAD TO LIGHT AND VARIABLE WINDS THIS EVENING BECOMING CALM... THEN INCREASING BY MID TO LATE MORNING AS A SOUTHWESTERLY RETURN FLOW DEVELOPS (WITH WIND SPEEDS BY AFTERNOON GENERALLY IN THE 7 TO 11 KT RANGE... WITH POSSIBLY A FEW WIND GUSTS TO 15-17 KTS AT KGSO/KINT). HIGH CLOUDS WILL INCREASE ACROSS THE AREA LATE TONIGHT AND CONTINUE TO STREAM ACROSS THE REGION ON MONDAY. THRE IS A GOOD CHANCE THAT VFR CONDITIONS WILL PREVAIL MONDAY EVENING THROUGH FRIDAY. A SERIES OF DISTURBANCES ALOFT ROTATING AROUND A CLOSED UPPER LEVEL LOW OVER THE NORTHERN MID ATLANTIC WILL CAUSE PERIODS OF CLOUDINESS OVER CENTRAL NC TUESDAY THROUGH WEDNESDAY NIGHT. HOWEVER CLOUD BASES SHOULD REMAIN ABOVE MVFR CRITERIA. THE UPPER LEVEL LOW WILL LIFT GRADUALLY NEWD THU INTO FRIDAY...ALLOWING HIGH PRESSURE TO BUILD INTO OUR REGION. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...SEC NEAR TERM...SEC SHORT TERM...WSS LONG TERM...HARTFIELD AVIATION...BSD/WSS

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