Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 041759 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 159 PM EDT FRI SEP 4 2015 .SYNOPSIS... A BACKDOOR COLD FRONT WILL APPROACH THE REGION FROM THE NORTH TODAY BEFORE SLIDING THROUGH THE AREA LATER TONIGHT INTO SATURDAY. INCREASING MOISTURE AHEAD OF THE BOUNDARY WILL LEAD TO MORE WIDESPREAD COVERAGE OF SHOWERS AND STORMS LATER TODAY INTO THIS EVENING. HIGH PRESSURE WILL WEDGE IN FROM THE NORTHEAST SATURDAY INTO SUNDAY...AND REMAIN IN PLACE THROUGH EARLY NEXT WEEK...RESULTING IN SOMEWHAT COOLER WEATHER OVER THE HOLIDAY WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1250 PM ED FRIDAY... ADJUSTMENTS TO THE FORECAST FOR THE AFTERNOON INCLUDE AN INCREASE BY TWO TO THREE DEGREES TO THE HIGH TEMPERATURE AT MANY LOCATIONS. LATEST READINGS ACROSS THE AREA SHOW TEMPERATURES ALREADY WITHIN ONE OR TWO DEGREES OF THE FORECAST HIGHS. WHILE WE WILL BE BE SEEING MORE CLOUD COVER AS CONVECTION FIRES...TEMPERATURES SHOULD BE ABLE TO GAIN AROUND FIVE MORE DEGREES OF WARMING AT MOST LOCATIONS. HAVE MADE MINOR TWEAKS TO THE PROBABILITY OF PRECIPITATION TO BETTER REFLECT WHERE CONVECTION IS FIRING CURRENTLY...AND EXPECTATIONS OVER THE NEXT FEW HOURS BEFORE BLENDING WITH THE PREVIOUS FORECAST FOR THE LATE AFTERNOON. NO OTHER NOTABLE ADJUSTMENTS AT THIS TIME. AS OF 945 AM EDT FRIDAY... SOME PATCHY FOG STILL EXIST OVER PARTS OF THE GREENBRIER...NEW...AND JACKSON RIVER BASINS...BUT IS DISSIPATING. THIS TREND WILL CONTINUE SO THAT MOST OF THESE AREAS WILL BE FOG- FREE BY 1100 AM. THE PROSPECTS OF A GREATER COVERAGE OF SHOWERS AND STORMS IS STILL ON TRACK FOR TODAY. THE LATEST FORECAST WILL REFLECT ONE SMALL CHANGE. ONSET TIME OF INITIATION HAS BEEN DELAYED AN HOUR...MORE IN THE 11AM TO NOON RANGE. THE REMAINDER OF THE FORECAST HAS BEEN LEFT THE SAME. AS OF 220 AM EDT FRIDAY... WEAK HIGH PRESSURE OVER THE AREA EARLY THIS MORNING WILL GIVE WAY TO INCREASING MOISTURE ADVECTION THIS AFTERNOON AHEAD OF A BACKDOOR COLD FRONT THAT WILL DRIFT SOUTH INTO NORTHERN VA BY THIS EVENING. THIS ALONG WITH A PIECE OF MID LEVEL SHORTWAVE ENERGY IN THE OHIO VALLEY THAT SHOULD SCOOT SOUTHEAST JUST AHEAD OF THE BOUNDARY AND INTERACT WITH MOIST PWATS/STRONG INSTABILITY TO RESULT IN AREAS OF DEEP CONVECTION LATER ON. MOST MODELS SUGGEST INITIAL DEVELOPMENT ALONG THE BLUE RIDGE AIDED BY DEVELOPING LOW LEVEL NE FLOW AHEAD OF THE SHORTWAVE AND ALONG AN AXIS OF PROGGED HIGHER 85H THETA-E. HOWEVER A FEW SOLUTIONS INCLUDING ENSEMBLES SUGGEST A SECONDARY AREA OF BETTER COVERAGE OUT ACROSS THE PIEDMONT WHERE APPROACH OF THE SHORTWAVE AND FOLDING OF THE FRONT EAST OF THE MOUNTAINS MAY INDUCE A WEAK WAVE OVER THE SOUTHEAST. THUS TRENDED LIKELY POPS A BIT MORE TOWARD THE EASTERN SLOPES OF THE BLUE RIDGE BY MID AFTERNOON...AND THEN SHIFTED SOUTH TOWARD NW NC/SOUTHSIDE VA WHERE GUIDANCE SHOWS STRONGER PRE-FRONTAL CONVERGENCE LATE PER PROGGED HIGHER PWATS COMING IN LINE WITH THE WAVE. OTHERWISE RUNNING WITH DECENT CHANCE POPS ELSEWHERE ALTHOUGH SEVERE POTENTIAL LIMITED BY WEAK SHEAR AND MOIST SOUNDINGS OVERALL. HOWEVER GIVEN THE DEGREE OF HEATING WITH HIGHS AGAIN LIKELY PUSHING 90 BLUE RIDGE AND POINTS SE...SOME DOWNBURST POTENTIAL WITH ANY ORGANIZED SLOW MOVING CLUSTER OF STORMS. AXIS OF SHRA/TSRA MAY AGAIN ORGANIZE MORE OVER THE PIEDMONT AND SOUTHERN SECTIONS BEFORE SLIDING SW THIS EVENING WELL AHEAD OF THE FRONT AND PRIOR TO THE EXODUS OF THE WAVE ALOFT. THIS SHOULD ALLOW ENOUGH COVERAGE FOR CONTINUED LIKELY POPS SOUTHEAST...AND CHANCE ELSEWHERE BEFORE LOSS OF HEATING AND EXITING LIFT CAUSE WEST BOUND CONVECTION TO BECOME MORE SHALLOW OVERNIGHT. APPEARS BEST COVERAGE AFTER MIDNIGHT TO END UP OVER THE SOUTHERN/SW SECTIONS ALONG THE NOSE OF THE DEVELOPING WEDGE WHERE WILL BE GETTING MORE OF A EAST/SE TRAJECTORY INCLUDING LOW LEVEL FOCUS ALONG THE FRONT. MAY EVEN SEE A BIT OF DRYING FAR NE SECTIONS LATE TONIGHT AND OVER THE FAR WEST WITH DOWNSLOPE...OTHERWISE LOOKING AT RANGE FROM LOW CHANCES NORTH TO HIGHER CHANCES SW LATE. EXPECT OVERALL CLOUDY SKIES AND LINGERING MOIST DEWPOINTS TO HOLD TEMPS UP DESPITE LOW LEVEL COOL ADVECTION SO STAYED WITH MOSTLY 60S FOR LOWS. && .SHORT TERM /SATURDAY THROUGH MONDAY/... AS OF 300 AM EDT FRIDAY... A HYBRID WEDGE WILL REMAIN ALONG THE EAST COAST OVER THE WEEKEND. THIS WEDGE WILL BE CENTERED OFF THE NEW ENGLAND COAST AND WILL STRETCH SOUTH INTO GEORGIA. WITH WEAK ISENTROPIC LIFT...EASTERLY FLOW AND ATLANTIC MOISTURE...MOSTLY CLOUDY SKIES ARE EXPECTED. RAIN/DRIZZLE IS ALSO POSSIBLE ALONG THE BLUE RIDGE EACH PERIOD AND OVER THE PIEDMONT DURING THE AFTERNOON AND EVENING HOURS. THE PARENT SURFACE RIDGE DRIFTS EAST ON MONDAY...LEAVING A BAGGY HIGH OVER THE MID ATLANTIC REGION. THIS WILL KEEP A CHANCE FOR LIGHT RAIN/DRIZZLE ALONG AND EAST OF THE BLUE RIDGE INTO MONDAY NIGHT. SOME DRY AIR MAY BE ABLE TO ADVECT INTO THE REGION AS A POSSIBLE CLOSED LOW FORMS OVER NORTHERN FLORIDA. TEMPERATURES WILL BE TRICKY WITH A WEDGE IN PLAY OVER THE WEEKEND AND INTO EARLY NEXT WEEK. EASTERLY FLOW WILL KEEP AFTERNOON TEMPERATURES A FEW DEGREES COOLER THAN NORMAL BUT HELP WARM THE WEST WITH DOWNSLOPE FLOW. ISENTROPIC LIFT WILL KEEP THE AREA CLOUDY BUT THERE COULD BE A FEW BREAKS IN THE CLOUDS DURING THE AFTERNOON...ONLY TO FILL BACK IN DURING THE EVENING. THESE CLOUDS AND ANY RAIN FALLING COULD COOL AFTERNOON TEMPERATURES 5F-8F COOLER THAN NORMAL. AS OF THIS FORECAST PACKAGE...CONFIDENCE IS NOT HIGH FOR AN ALL DAY RAIN EVENT AND ANY BREAKS IN THE RAIN OR CLOUDS WILL ALLOW TEMPERATURES TO WARM. WITH CONTINUED CLOUDINESS...TEMPERATURES WILL RUN MUGGY AND WARMER THAN NORMAL EACH NIGHT. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... AS OF 100 PM EDT THURSDAY... STARTING WITH A BROAD UPPER LOW OVER THE SOUTHEAST UNITED STATES AND A STRONG RIDGE IN THE SOUTHERN PLAINS BY MONDAY NIGHT. 500 MB HEIGHTS FALL OVER THE NORTHEAST UNITED STATES MONDAY NIGHT THROUGH WEDNESDAY. BY THURSDAY THE NORTHERN STREAM BECOMES MORE DOMINANT WITH MORE TROUGHING ACROSS ALL OF THE EAST. AT THE SURFACE AND LOW LEVELS FORECAST AREA WILL BE IN A DEEP WEDGE COVERING THE EAST SIDE OF THE APPALACHIANS INTO MONDAY NIGHT WITH EAST TO SOUTHEAST WINDS. THE WEDGE WILL BREAK DOWN ON TUESDAY. THEN SOUTHWEST FLOW WILL BRING A RETURN OF MOISTURE AND WARMER 850 MB TEMPERATURES TUESDAY NIGHT AND WEDNESDAY. A WELL DEFINED COLD FRONT AND THE LEADING EDGE OF COOLER AIR WILL REACH THE FORECAST AREA ON THURSDAY. WAVES OF LOW PRESSURE ALONG THE FRONT IN THE CENTRAL UNITED STATES MAY SLOW DOWN THE TIMING AND THE EASTWARD MOVEMENT OF THE FRONT FOR WEDNESDAY AND THURSDAY. TEMPERATURES WILL AGAIN BE ABOVE NORMAL IN THE WARM SECTOR AHEAD OF THE COLD FRONT ON WEDNESDAY AND THURSDAY. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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AS OF 135 PM EDT FRIDAY... ISOLATED TO SCATTERED SHOWERS WILL CONTINUE TO DEVELOP THIS AFTERNOON AND LINGER INTO THE EARLY PART OF TONIGHT. THE GREATEST CONCENTRATION WILL BE ACROSS THE NORTHERN AND EASTERN SECTIONS OF THE FORECAST AREA. WHILE MOST OF THE REGION WILL EXPERIENCE VISUAL FLIGHT RULES...LOCATIONS UNDER THE HEAVIER SHOWER OR THUNDERSTORM CORES WILL EXPERIENCE BRIEF INSTRUMENT FLIGHT RULES/MARGINALVISUAL FLIGHT RULES CONDITIONS. OVERNIGHT...EASTERLY FLOW WILL INCREASE THROUGH A DEEPER PORTION OF THE ATMOSPHERE. LOOKING FOR LINGERING ISOLATED SHOWERS TO LAST INTO THE EARLY MORNING HOURS OF SATURDAY. AS MOISTURE BANKS UP INTO AND ACROSS THE BLUE RIDGE...LOOK FOR INCREASING AREAS OF MARGINAL VISUAL FLIGHT RULES CEILINGS WITH POCKETS OF INSTRUMENT FLIGHT RULES CEILINGS AND MARGINAL VISUAL FLIGHT RULES VISIBILITIES FOR MIST. SATURDAY MORNING INTO THE EARLY AFTERNOON...EXPECT A GRADUAL TREND OF CEILINGS AND VISIBILITIES IMPROVING TO VISUAL FLIGHT RULES LEVELS. ISOLATED SHOWERS WILL BE ON THE INCREASE AROUND NOONTIME...BUT CONFIDENCE IN THEIR LOCATION IS NOT GREAT ENOUGH TO INCLUDE ANY IN THE PREVAILING WEATHER OF THE TERMINAL AERODROME FORECASTS. EXTENDED AVIATION DISCUSSION... HIGH PRESSURE WILL GRADUALLY WORK INTO THE REGION BY THE END OF THE WEEKEND...AND REMAIN OVER THE REGION INTO THE EARLY PART OF NEXT WEEK. LINGERING MOISTURE AND AN EASTERLY FETCH WILL HELP MAINTAIN SOME ISOLATED TO SCATTERED SHOWERS ACROSS MAINLY WESTERN AND SOUTHERN PARTS OF THE AREA...ESPECIALLY ON SATURDAY AND SUNDAY AFTERNOON. MOISTURE STARTS TO INCREASE AGAIN MONDAY INTO TUESDAY WHILE THE INFLUENCE OF THE RIDGE WEAKENS. COVERAGE OF SHOWERS...AND POSSIBLY A FEW STORMS...WILL LIKEWISE START TO INCREASE. PAST SATURDAY...CEILINGS AND VISIBILITIES WILL PRIMARILY BE VISUAL FLIGHT RULES. THE EXCEPTION WILL BE LINGERING PATCHY MARGINALVISUAL FLIGHT RULES ACROSS PARTS OF THE REGION SATURDAY AFTERNOON. ALSO...OVERNIGHT AND EARLY MOUNTAIN AND RIVER VALLEY INSTRUMENT FLIGHT RULES/MARGINAL VISUAL FLIGHT RULES FOG/MIST ARE EXPECTED.
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&& .HYDROLOGY... AS OF 745 PM EDT THURSDAY... THE WEEKLY UNITED STATES DROUGHT MONITOR ISSUED ON SEPTEMBER 3RD SHOWS THE EFFECT OF A DRIER THAN NORMAL AUGUST ACROSS MUCH OF THE AREA. ABNORMALLY DRY CONDITIONS...D0 ON THE DROUGHT SCALE HAVE BEEN EXPANDED INTO A LARGE PORTION OF SOUTHSIDE VIRGINIA COVERING MUCH OF THE DAN AND LOWER ROANOKE RIVER BASINS. PARTS OF THE UPPER YADKIN RIVER BASIN IN NORTH CAROLINA ARE ALREADY IN D1 OR MODERATE DROUGHT. AUGUST RAINFALL WAS AS LOW AS 50 PERCENT OF NORMAL OR LESS IN PARTS OF THE AFOREMENTIONED AREAS. SEVERAL NWS COOPERATIVE CLIMATE STATIONS IN SOUTHERN VIRGINIA RECORDED WELL UNDER 2 INCHES OF RAIN THE ENTIRE MONTH OF AUGUST INCLUDING HUDDLESTON IN BEDFORD COUNTY AT 1.17 INCHES AND ROCKY MOUNT IN FRANKLIN COUNTY AT 1.36 INCHES. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...DS/JH NEAR TERM...DS/JH SHORT TERM...RCS LONG TERM...AMS AVIATION...DS HYDROLOGY...PC

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