Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 221131 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 731 AM 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 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 /12Z MONDAY THROUGH FRIDAY/... AS OF 730 AM EDT MONDAY... COLD FRONT EXTENDED FROM OFF THE MID ATLANTIC COAST TO THE GULF COAST STATES AT 11Z/7AM. SURFACE WIND WERE FROM THE WEST TO NORTHWEST BEHIND THE FRONT WITH GUSTS UP TO 20 KNOTS AT HIGHER ELEVATIONS. ENOUGH PRESSURE GRADIENT TO SUPPORT GUSTY WINDS IN THE MOUNTAINS THROUGH NOON. MVFR CEILINGS ARE EXPECTED TO REMAIN IN THE WESTERN UPSLOPE AREAS....INCLUDING KBLF AND KLWB THROUGH EARLY AFTERNOON. VFR CONDITIONS WILL CONTINUE EAST OF THE BLUE RIDGE. AS HIGH PRESSURE BUILDS IN AND THE NORTHWEST UPSLOPE FLOW WEAKENS...THE CLOUDS WILL ERODE. HIGH CONFIDENCE THAT KLWB AND KBLF WILL IMPROVE TO VFR AFTER 21Z/5PM. HAVE ADDED LIFR FOG IN FOR KLWB AFTER MIDNIGHT. EXPECTING COOL AIR OVER THE RELATIVELY WARMER GREENBRIER RIVER WILL PRODUCE FOG. 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. A LOW PRESSURE SYSTEM COMING OUT OF THE GULF COAST MAY BRING IFR CONDITIONS TO THE REGION AS EARLY AS WEDNESDAY NIGHT. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS SHORT TERM...RCS LONG TERM...CF AVIATION...AMS/RAB

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