Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 312317 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 717 PM EDT FRI JUL 31 2015 .SYNOPSIS... HIGH PRESSURE WILL BUILD EAST INTO THE MID ATLANTIC REGION TONIGHT. THIS HIGH CENTER WILL STAY OVER MOST OF REGION THIS WEEKEND. A COUPLE OF UPPER DISTURBANCES MAY BRING A FEW SPOTTY SHOWERS TO THE MOUNTAINS LATE SATURDAY OR SUNDAY...BUT THE MAJORITY OF OUR AREA WILL STAY DRY. && .NEAR TERM /THROUGH SATURDAY/... AS OF 152 PM EDT FRIDAY... HIGH PRESSURE CENTERED AROUND MISSOURI THIS AFTERNOON WILL BUILD EASTWARD TONIGHT INTO SATURDAY. SCATTERED AFTERNOON CU WILL DIMINISH OR DISSIPATE BY SUNSET WITH THE LOSS OF SOLAR HEATING. TONIGHT...THE FLOW STARTS TO BACK TO THE WEST AS A WEAK UPPER SHORTWAVE PIVOTS UNDER THE BROAD TROUGH ACROSS THE MID ATLANTIC REGION. AIRMASS IS TOO DRY TO GENERATE ANYTHING MORE THAN CLOUDS WITH ANY SHORTWAVE ROTATING AROUND THE UPPER TROUGH. GREAT NIGHT TO OPEN YOUR WINDOWS. THE COMBINATION OF LIGHT WINDS AND SOME LOW LEVEL MOISTURE MAY PRODUCE PATCHY FOG IN THE FAVORED VALLEYS. LEANED TOWARDS THE COOLER MOS COOP GUIDANCE FOR LOW TEMPERATURES TONIGHT. LOW TEMPERATURES TONIGHT INTO SATURDAY MORNING WILL RANGE FROM AROUND 50 DEGREES IN THE COLDEST DEEPER VALLEYS TO THE LOWER 60S IN THE PIEDMONT. HIGH PRESSURE WILL BRING LOWER HUMIDITY AGAIN SATURDAY. ABUNDANT SUNSHINE AND LIGHT DOWNSLOPE WIND FLOW WILL WARM HIGH TEMPERATURES SATURDAY INTO THE UPPER 70S IN THE NORTHWEST MOUNTAINS TO THE LOWER 90S. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... AS OF 335 PM EDT FRIDAY... BROAD UPPER TROF WILL REMAIN ANCHORED FROM THE JAMES BAY AREA SOUTH INTO THE UPPER AND LOWER GREAT LAKES SATURDAY NIGHT INTO MONDAY MORNING...WITH WEAK SURFACE HIGH PRESSURE SYSTEM LINGERING OVER THE MID APPALACHIAN REGION. THIS SETUP WILL ENSURE A CONTINUATION OF DRY WEATHER AND RELATIVELY LOW DEW POINTS THAT WILL SUPPORT EFFICIENT DAYTIME HEATING...WITH GOOD RADIATIONAL COOLING AT NIGHT...RESULTING IN MARKED DIURNAL TEMPERATURE SWINGS OF AROUND 30F. BY MONDAY AFTERNOON INTO MONDAY NIGHT...APPROACH AND EVENTUAL PASSAGE OF AN UPSTREAM SHORTWAVE TROF DIVING SOUTHEAST THROUGH/OUT OF THE UPPER GREAT LAKES WILL BRING AN INCREASE IN CLOUDS ALONG WITH A THREAT FOR WIDELY SCATTERED SHOWERS/THUNDERSHOWERS INTO UPSLOPE AREAS OF THE WESTERN BLUE RIDGE NORTH INTO THE ALLEGHANY HIGHLANDS. HOWEVER...WESTERLY LOW LEVEL FLOW AHEAD OF THE WAVE SHOULD PREVENT ANY POTENTIAL FOR SPILL-OVER INTO DOWNSLOPE AREAS EAST OF THE BLUE RIDGE. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 335 PM EDT FRIDAY... ENERGY ASSOCIATED WITH GREAT LAKES TROF EXPECTED TO BE NORTHEAST OF THE BLACKSBURG FORECAST AREA BY DAYBREAK TUESDAY. ATTENDANT COOL FRONT WILL LIKELY SLOW AND THEN STALL OVER/NEAR THE MID APPALACHIAN AND MID ATLANTIC REGION LATER TUESDAY INTO TUESDAY NIGHT AS TROF SPOKE LIFTS NORTHEAST AND AWAY FROM AREA AND AS UPPER FLOW IN ITS WAKE GRADUALLY FLATTENS TO MORE OF A ZONAL CONFIGURATION. EAST-WEST BAROCLINIC ZONE WILL THEN BECOME ESTABLISHED OVER THE FORECAST AREA FOR THE REST OF THE LONG-TERM PERIOD...WITH ADDITIONAL UPSTREAM SHORT WAVES AND/OR MESOSCALE VORTICITY CENTERS FROM DECAYING OLD MIDWEST CONVECTIVE COMPLEXES PROVIDING SUFFICIENT ENERGY/SUPPORT TO MAINTAIN THREAT FOR SCATTERED CONVECTION THROUGH THE PERIOD. GRADUALLY RISING DEW POINTS WILL SLOWLY COMPRESS THE DIURNAL TEMPERATURE CURVE BACK TO AROUND 20F AS SULTRY AIRMASS SLOWLY REESTABLISHES ITSELF OVER THE AREA. EXPECT OVERNIGHT LOWS DURING THE PERIOD TO RANGE FROM THE 60S IN THE MOUNTAINS TO AROUND 70 IN THE PIEDMONT...WITH HIGHS RANGING FROM MAINLY 80S IN THE MOUNTAINS TO LOWER-MID 90S ACROSS THE PIEDMONT. && .AVIATION /23Z FRIDAY THROUGH WEDNESDAY/...
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AS OF 132 PM EDT FRIDAY... VFR CONDITIONS EXPECTED FOR MOST AREAS THROUGH 00Z-00Z 8PM-8PM TAF TIME PERIOD. THE EXCEPTION TO THIS RULE WILL BE SOME BRIEF...LATE NIGHT/EARLY MORNING PATCHY RIVER OR MOUNTAIN VALLEY FOG. ANY THAT DOES DEVELOP WILL QUICKLY MIX OUT BY 13Z/9AM SATURDAY. HIGH CONFIDENCE IN CEILINGS...VISIBILITIES AND WINDS DURING THE TAF PERIOD. EXTENDED AVIATION FORECAST... AS OF 132 PM EDT FRIDAY... MAINLY VFR THIS WEEKEND WITH HIGH PRESSURE IN PLACE. A FEW UPPER DISTURBANCES MAY BRING A FEW VFR CIGS TO THE MOUNTAINS LATER SATURDAY INTO SUNDAY. THE THREAT OF SHOWERS WILL BE LOW THOUGH A BACKDOOR FRONT MAY ALLOW FOR SOME AGAIN LATER MONDAY OR TUESDAY. WITH SUSTAINED WINDS STAYING LIGHT TO CALM AT NIGHT AND MAINLY CLEAR SKIES...THE FOG THREAT WILL EXIST IN THE TYPICAL PREDAWN HOURS AT KLWB/KBCB BY EARLY NEXT WEEK.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...KK/WP NEAR TERM...KK SHORT TERM...WERT LONG TERM...WERT AVIATION...DS/KK/WP

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