Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 082106 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 406 PM EST MON FEB 8 2016 .SYNOPSIS... AN UPPER LEVEL DISTURBANCE AND COLD FRONT WILL CROSS THE REGION THIS EVENING AND OVERNIGHT...FOLLOWED BY AND EXTENDED PERIOD OF COLD TEMPERATURES THROUGH THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 315 PM MONDAY... A DEEP TROUGH DIGGING THROUGH THE MIDWEST WILL SPREAD 100-150M HEIGHT FALLS ACROSS THE REGION THIS EVENING...WITH AN ASSOCIATED PAIR OF COLD FRONTS TO IMPACT THE REGION OVER THE NEXT 48 HOURS. THE BIGGEST FORECAST INTEREST THIS AFTERNOON AND EVENING IS THE BAND OF SHOWERS FORMING ALONG THE LEAD FRONT AND PREFRONTAL TROUGH OVER THE WESTERN PIEDMONT AND FOOTHILLS. THE BAND STRETCHING FROM THE TRIAD THROUGH CHARLOTTE IS FORECAST BY CONVECTION ALLOWING MODELS TO PROGRESS EAST ACROSS CENTRAL NC BETWEEN 21Z AND 03Z. WITH DEWPOINTS ONLY IN THE UPPER 20S AND LOWER 30S...THERE IS VERY LITTLE CAPE...IF ANY AT ALL. HOWEVER...AN AXIS OF STEEP 7-7.5 C/KM MID-LEVEL LAPSE RATES ASSOCIATED WITH THE DRAMATIC COOLING UNDERWAY ALOFT HAS ADVECTED OVER CENTRAL NC...PER SPC MESOANALYSIS. THIS COUPLED WITH THE (RELATIVE) WARM SOUTHERLY FLOW MAY ALLOW FOR SOME WEAK INSTABILITY TO DEVELOP...ESPECIALLY JUST IN ADVANCE OF THE FRONT. THE HRRR SHOWS THE BAND OF SHOWERS STRENGTHENING A BIT WITH TIME AND EASTWARD EXTENT LATE THIS AFTERNOON...AND GIVEN A FAIRLY DRY SUB-CLOUD LAYER AND STEEPENING LOW-LEVEL LAPSE RATES...WIND GUSTS OF 30-40MPH WITH THE SHOWERS SEEMS ENTIRELY POSSIBLE. A FEW LIGHTNING STRIKES ARE ALSO PLAUSIBLE WITHIN THE LINE GIVEN THE THE STEEP MID-LEVEL LAPSE RATES...BUT WITHOUT BETTER FORECASTS CAPE...PREFER TO MONITOR THE EVOLUTION OF THE CONVECTIVE ELEMENTS BEFORE ADDING THUNDER TO THE FORECAST. A WEAK SURFACE LOW IS FORECAST TO DEVELOP OVER SOUTHEAST VA BY MIDNIGHT AND THEN QUICKLY MOVE OFF THE COAST TUESDAY MORNING. MODELS HAVE TRENDED DRIER WITH PRECIP WRAPPING AROUND THE LOW LATE TONIGHT...ALTHOUGH THE NAM CONTINUES TO SHOW SOME OMEGA AND MOISTURE IN THE -12C TO -18C LAYER FROM DANVILLE TO EMPORIA...SO IT SEEMS LESS LIKELY THAT WE`LL SEE ANY PRECIP THAT CHANGES OVER TO SNOW AFTER MIDNIGHT BUT A FEW FLURRIES CANNOT BE RULED OUT. LOWS 28-33. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 315 PM MONDAY... THE DEEP UPPER TROUGH TO OUR WEST WILL MAKE ITS WAY OVERHEAD ON TUESDAY...WITH A DISTURBANCE WITHIN THE TROUGH FORECAST TO SWING ACROSS VA AND NORTHERN NC DURING THE AFTERNOON. STEEP LAPSE RATES ALOFT...ALONG WITH THE STRONG DCVA AND MOISTENING BETWEEN 5-10K FEET(COINCIDENT WITH THE ICE NUCLEATION ZONE)...MAY LEAD SOME ISOLATED SHOWERS NEAR THE NC/VA BORDER....ESPECIALLY LATER IN THE DAY FROM ROXBORO TO ROANOKE RAPIDS. HOWEVER...MODELS CONTINUE TO INDICATE MUCH BETTER COVERAGE NORTH OF THE BORDER AND THE ECMWF IS THE ONLY MODEL TO INDICATE ANY QPF IN THE NORTHERN COASTAL PLAIN. HIGHS WILL REACH THE UPPER 30S WEST TO MID 40S EAST...BUT DEWPOINTS IN THE LOWER 20S WOULD PUSH WETBULB PROFILES COLD ENOUGH TO SUPPORT SNOW SHOWERS OR FLURRIES. COLD ADVECTION WILL CONTINUE TUESDAY NIGHT BEHIND THE ARCTIC FRONT...WITH TEMPS FALLING INTO THE LOW/MID 20S. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... AS OF 400 PM MONDAY... COLD MID-LATE WEEK...AND EVEN COLDER --PERHAPS RECORD SO-- THIS WEEKEND...WITH A COUPLE OF OPPORTUNITIES FOR PRECIPITATION (LATE FRI- FRI NIGHT AND LATE MON-TUE). A HIGHLY AMPLIFIED PATTERN CHARACTERIZED BY A STRONG WESTERN NOAM RIDGE AND EASTERN NOAM TROUGH WILL UNDERGO A BRIEF RELAXATION LATE IN THE WEEK...IN ADVANCE OF A POLAR VORTEX THAT WILL SETTLE ACROSS SOUTHEAST CANADA AND NEW ENGLAND...AND EFFECTIVELY RE-AMPLIFY THE FLOW...THIS WEEKEND. A PROGRESSIVE PACIFIC TROUGH WILL THEN FLATTEN THE WESTERN NOAM RIDGE SUN-MON. WITHIN THE NW FLOW ALOFT...SHEAR VORTICITY AND ASSOCIATED LOW AMPLITUDE TROUGHS WILL AMPLIFY INTO THE BASE OF THE TROUGH OVER THE EASTERN STATES MID-LATE WEEK...WITH EACH SUPPORTING AN AREA OF LIGHT PRECIPITATION STREAKING SOUTHEASTWARD FROM THE NORTHERN PLAINS TO THE CENTRAL-SOUTHERN APPALACHIANS. THE MODELS SUGGEST THE LEAD DISTURBANCE WILL HAVE A MORE LIMITED MOISTURE SUPPLY AND LITTLE LOW LEVEL SUPPORT FOR THE MAINTENANCE OF PRECIPITATION EAST OF THE APPALACHIANS ON THU...WHILE THE SECOND WILL BE ACCOMPANIED BY A LOW- MID LEVEL WAA REGIME AND CONSEQUENTLY HAVE A BETTER CHANCE OF SUPPORTING A BRIEF PERIOD OF LIGHT PRECIPITATION...MOST LIKELY IN THE FORM OF SNOW...OR A RAIN/SNOW MIX ACROSS THE SOUTHERN COUNTIES...CENTERED AROUND FRI EVENING. A POTENTIALLY MORE SIGNIFICANT SYSTEM WILL ACCOMPANY THE AFOREMENTIONED PACIFIC TROUGH...AS THE AFOREMENTIONED POLAR VORTEX SUPPRESSES THE NORTHERN STREAM/PROMOTES CONFLUENT FLOW ALOFT...WHICH WOULD SUPPORT THE SOUTHEASTWARD MAINTENANCE OF A 1040-1045 MB HIGH FROM THE ARCTIC. WHILE THIS WOULD YIELD INITIALLY JUST NEAR RECORD COLD CONDITIONS FOR THE WEEKEND...THE EASTWARD MIGRATION OF THE PACIFIC TROUGH AND AN INCREASINGLY ACTIVE SOUTHERN STREAM WOULD RAISE THE PROBABILITY OF STREAM INTERACTION...AND STORMINESS AND APPALACHIAN COLD AIR DAMMING...MON-TUE. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... AS OF 100 PM MONDAY... SOUTHERLY WINDS WILL SLOWLY INCREASE THIS AFTERNOON AHEAD OF A COLD FRONT AND BAND OF SHOWERS EXPECTED TO CROSS CENTRAL NC BETWEEN 20Z AND 02Z...THEN TURN TO WESTERLY BEHIND THE FRONT. A BRIEF PERIOD OF MVFR CONDITIONS AND A WIND GUST TO 30-35MPH IS POSSIBLE WITH THE SHOWERS...THOUGH THE STRONGER GUSTS WOULD BE VERY ISOLATED AND ARE NOT INCLUDED IN THE TAF. AS THE SHOWERS EXIT THE COASTAL PLAIN LATE THIS EVENING...A SURFACE LOW IS FORECAST TO FORM ALONG THE FRONT OVER SOUTHERN VA..WHICH MAY DRAW SOME ADDITIONAL MOISTURE SOUTH ACROSS THE NORTHERN COASTAL PLAIN AND CAUSE A FEW EXTRA SHOWERS OR SNOW SHOWERS...MAINLY NORTH OF KRDU AND KRWI AFTER 09Z. WESTERLY WINDS WILL INCREASE TO 9-12KT AND GUST TO AROUND 20KT ON TUESDAY OUTLOOK...WEDNESDAY AND THURSDAY WILL FEATURE VFR CONDITIONS WITH GUSTY NORTHWEST WINDS OF 20-25. THE NEXT CHANCE OF SUB-VFR CONDITIONS WILL COME FRIDAY AS A WEAK LOW PRESSURE SYSTEM CROSSES THE AREA. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BADGETT NEAR TERM...SMITH SHORT TERM...SMITH LONG TERM...2 AVIATION...SMITH

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