Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 221711 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 111 PM EDT MON SEP 22 2014 .SYNOPSIS... A LARGE HIGH PRESSURE SYSTEM OVER THE MID MISSISSIPPI VALLEY WILL MOVE EAST TODAY AND TONIGHT AND WILL COVER MUCH OF THE EASTERN UNITED STATES THROUGH WEDNESDAY. LOW PRESSURE WILL DEVELOP ALONG THE SOUTHEAST COAST THURSDAY AND FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 925 AM EDT MONDAY... EDITED THE NEAR TERM GRIDS TO REFLECT CURRENT CONDITIONS. LOWERED WIND SPEEDS A BIT AS THEY ARE WEAKENING QUICKER THAN ANTICIPATED. ALSO EXPANDED CLOUD COVER EASTWARD THROUGH THE NRV FOR THE NEXT FEW HOURS AS VIS SATELLITE CONFIRMS LOW STRATO CU HANGING ON. EAST OF THE BLUE RIDGE MOST LOCATIONS ARE ALREADY MOSTLY SUNNY OR CLEAR. 12Z SOUNDING SHOWS PLENTY OF COOL AND DRY AIR CONTINUING TO MOVE INTO THE REGION. DEWPTS ACROSS THE MOUNTAINS ARE ALREADY DOWN TO THE UPPER 40S AND THEY WILL CONTINUE FALLING THROUGHOUT THE DAY. AS OF 400 AM EDT MONDAY... DEEP UPPER TROF OVER THE GREAT LAKES AND OHIO VALLEY THIS MORNING. SHORT WAVE OVER MISSOURI REACHES THE BASE OF THE TROF AND CLOSES OFF AN UPPER LOW NEAR SOUTH CAROLINA TONIGHT. MODELS ALSO SHOWING COLDER 500 MB TEMPERATURES OVER THE FORECAST AREA THIS AFTERNOON AND TONIGHT. FRONT HAS CLEARED FORECAST AREA. 850 MB TEMPERATURES WILL DROP TODAY AND TONIGHT AND WILL REACH +8 TO +10 BY 12Z/8AM TUESDAY. AN EVEN BIGGER CHANGE IN THE DEW POINTS WAS ALREADY UNDERWAY. SURFACE DEW POINTS HAVE LOWERED INTO THE UPPER 40S IN SOUTHEAST WEST VIRGINIA. BY THIS AFTERNOON PRECIPITABLE WATER VALUES WILL BE LESS THAN 0.50 INCHES. SURFACE HIGH PRESSURE THE WAS CENTERED OVER THE MID MISSISSIPPI VALLEY THIS MORNING WILL MOVE EAST INTO THE OHIO VALLEY TONIGHT. WINDS WILL STILL BE GUSTY AT HIGHER ELEVATIONS THIS MORNING...BUT AS THE HIGH GETS CLOSER...WINDS WILL DIMINISH. WINDS WILL DECOUPLE THIS EVENING. WITH A MOSTLY CLEAR SKY AND THE LIGHT TO CALM WINDS OVERNIGHT...EXPECT THE COOLER AIR OVER THE RELATIVELY WARMER AREA RIVERS AND LAKES WILL RESULT IN FOG FORMATION. BUFKIT SOUNDINGS SHOWED A SHALLOW LAYER OF MOISTURE AND INSTABILITY FROM SOUTHEAST WEST VIRGINIA INTO THE ALLEGHANY HIGHLANDS THIS MORNING. WILL KEEP A SIGHT CHANCE OF SHOWERS IN SOUTHEAST WEST VIRGINIA THROUGH NOON. AS THE WINDS AND UPSLOPE FORCING DIMINISHES...THE CLOUDS WILL DISSIPATE. THIS MAY TAKE MOST OF THE DAY IN THE FAR NORTHWEST PART OF COUNTY WARNING AREA. STAYED BELOW GUIDANCE FOR MINIMUM TEMPERATURES TONIGHT...ESPECIALLY IN THE WESTERN VALLEYS BASED ON IDEAL RADIATIONAL COOLING CONDITIONS AFTER MIDNIGHT AND SURFACE DEWPOINTS DIPPING INTO THE 30S. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 AM EDT MONDAY... A STRONG DRY HIGH PRESSURE SYSTEM WILL BE CENTERED OVER NEW ENGLAND...WEDGING DOWN THE MID ATLANTIC THROUGH THE PERIOD. FOR THE MOST PART...THIS WEDGE WILL KEEP THE AREA COOL AND DRY. MODELS ARE DEVELOPING A CUT-OFF LOW OVER THE CAROLINAS ON TUESDAY. THE STRENGTH OF THIS LOW VARIES BETWEEN MODELS. IN RESPONSE TO THIS UPPER LOW...A DISTURBANCE IS EXPECTED TO DEVELOP OFF THE SOUTHEAST COAST. THE NAM KEEPS THIS DISTURBANCE AND ITS PRECIPITATION ALONG THE SOUTHEAST COAST THROUGH WEDNESDAY...THEN SLOWLY PUSHES IT INLAND TOWARDS THE THE NC/VA PIEDMONT WEDNESDAY NIGHT. THE GFS IS A LITTLE MORE PROGRESSIVE...ADVANCING THIS PRECIPITATION NORTHWARD ALONG THE COAST WEDNESDAY INTO WEDNESDAY NIGHT. LIGHT RAIN ENTERS THE PIEDMONT WEDNESDAY EVENING. THE ECM IS SLOWER AND TRACKS THE UPPER LEVEL LOW NORTHWARD OVER THE APPALACHIANS. THIS SCENARIO WOULD BRING PRECIPITATION FURTHER WESTWARD/INLAND THAN THE GFS/NAM FOR WEDNESDAY AND WEDNESDAY NIGHT. THE ECM HAS LIGHT PRECIPITATION TO THE BLUE RIDGE WITH STRONGER CONVECTION OVER THE COASTAL PIEDMONT OF VA/NC WEDNESDAY NIGHT. ANY ONE OR A COMBINATION OF THE MODELS COULD BE RIGHT. IT DOES APPEAR THE LOW OVER THE SOUTHEAST WILL STRENGTHEN THE WEDGE THROUGH THE PERIOD. A STRONGER WEDGE WOULD SUPPORT LIGHTER PRECIPITATION AND MORE SO TOWARDS THE PIEDMONT. SINCE CONFIDENCE IS LOW FOR MEASURABLE RAINFALL...WILL CONTINUE TO CARRY SLIGHT CHANCE POPS FOR RAIN ALONG AND EAST OF THE BLUE RIDGE. THE WEDGE WILL KEEP TEMPERATURES COOLER THAN NORMAL ON TUESDAY. KEPT TUESDAY TEMPERATURES NEAR GUIDANCE SINCE THE MODELS ARE ADVERTISING A MOSTLY CLEAR DAY AND A DRY EASTERLY FLOW. DESPITE THE STRENGTH OF THE WEDGE ON WEDNESDAY...EASTERLY FLOW AND A FETCH OFF THE ATLANTIC WOULD INCREASE THE CHANCE FOR STRATUS CLOUDS TO OVERSPREAD THE AREA LATE IN THE DAY WEDNESDAY AND WEDNESDAY NIGHT. FOR NOW...WILL LEAN TEMPERATURES TOWARDS THE COOLEST GUIDANCE (NAM). IF THE CHANCES FOR RAIN LOOKS MORE LIKELY...WEDNESDAY TEMPERATURES ALONG AND EAST OF THE BLUE RIDGE WILL BE LUCKY TO HIT THE UPPER 60S. THIS FORECAST PACKAGE HAS UNIFORM TEMPERATURES IN THE LOWER TO MID 70S WEDNESDAY. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 100 PM EDT SUNDAY... A STRONG SURFACE HIGH OVER THE NE STATES ON THURSDAY WILL SLOWLY DRIFT WESTWARD TO THE GREAT LAKES BY THE WEEKEND. THIS WILL LEAD TO A PROLONGED EASTERLY FLOW ACROSS THE REGION. HIGH TEMPERATURES WILL BE 5-10 DEGREES BELOW NORMAL RANGING FROM THE MID TO UPPER 60S ACROSS THE MOUNTAINS TO LOWER 70S EAST OF THE BLUE RIDGE. MODELS ARE STARTING TO AGREE ON A WEAK UPPER LEVEL DISTURBANCE FORMING ACROSS THE SE STATES LATE IN THE WEEK...HOWEVER THERE IS STILL MAJOR DIFFERENCES ON PLACEMENT WHICH WILL AFFECT HOW MUCH MOISTURE CAN GET PULLED UP INTO THE REGION. THE GFS CONTINUES TO BE MUCH DRIER THAN THE ECMWF. DUE TO THE MODEL DIFFERENCES...ONLY SLIGHT CHANCE POPS IN FROM THE BLUE RIDGE EASTWARD. && .AVIATION /17Z MONDAY THROUGH FRIDAY/... AS OF 100 PM EDT MONDAY... WEST TO NORTHWEST WINDS ARE CALMING DOWN THIS AFTERNOON AND SHOULD BE SUSTAINED BETWEEN 5-10KTS INTO THE EARLY EVENING. MVFR CEILINGS ARE HOLDING ON AT BLF...HOWEVER IT WILL BE SCATTERING OUT BY 21Z. VFR CONDITIONS SHOULD HOLD THROUGH MUCH OF THE OVERNIGHT. SEASONABLY COOL TEMPERATURES ARE EXPECTED TO RESULT IN SOME PATCHY RIVER FOG TUESDAY MORNING AS THE COOL AIR PASSES OVER THE MUCH WARMER WATERS. THIS SHOULD RESULT IN A FEW HOURS OF IFR CONDITIONS AT LWB AND MVFR/IFR CONDITIONS POSSIBLE IN BCB FOR AN HOUR OR TWO RIGHT AROUND DAWN. BY 14Z TUESDAY ALL TAF LOCATIONS WILL BE VFR AND WILL STAY AT THOSE CONDITIONS THROUGH THE REMAINDER OF THE TAF PERIOD. HIGH PRESSURE BUILDING IN TO THE NORTH WILL RESULT IN WINDS SLOWLY SHIFTING FROM A W/NW DIRECTION TODAY TO AN EASTERLY DIRECTION ON TUESDAY. EXTENDED AVIATION DISCUSSION... HIGH PRESSURE AND DRIER AIR IN THE REGION THROUGH WEDNESDAY WILL RESULT IN MAINLY VFR CONDITIONS. RIVER VALLEY FOG WILL STILL BE POSSIBLE AT NIGHT AS WINDS DIMINISH AND COOL AIR MASS DECOUPLES. THERE IS STILL SOME MODEL DIFFERENCES REGARDING A LOW PRESSURE SYSTEM FORMING FROM THE GULF COAST LATER THIS WEEK. SEVERAL MODELS SHOW MOISTURE INCREASING OVERNIGHT WEDNESDAY THROUGH THURSDAY EVENING WHICH MAY RESULT IN PERIODS OF IFR/MVFR CEILINGS AND VSBYS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS/CF SHORT TERM...RCS LONG TERM...CF AVIATION...AMS/CF/RAB

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