Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 191958 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 358 PM EDT TUE MAY 19 2015 .SYNOPSIS...
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HIGH PRESSURE OVER THE OHIO VALLEY AND UPPER MIDWEST WILL MOVE EAST TONIGHT...INTRODUCING A MUCH DRIER AIRMASS TO THE MID ATLANTIC REGION FOR WEDNESDAY. AN UPPER LEVEL DISTURBANCE WILL PASS ACROSS THE REGION THURSDAY...FOLLOWED BY TRANQUIL WEATHER FOR FRIDAY AND SATURDAY COURTESY OF DRY HIGH PRESSURE.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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AS OF 345 PM EDT TUESDAY... CHANGE IN AIRMASS IS UNDERWAY WITH FALLING DEWPOINTS. SURFACE COLD FRONT HAS MOVED EAST OF THE MOUNTAINS. ANY SHOWER ACTIVITY WILL QUICKLY MOVE EAST THIS EVENING AND AWAY FROM THE FORECAST AREA. TREND THROUGH THE EVENING WILL BE FOR CLEARING SKIES WITH FAIR/DRY WEATHER EXPECTED THE NEXT 24 HOURS PER HIGH PRESSURE WHICH IS BUILDING INTO THE MID ATLANTIC REGION FROM THE NORTHWEST. TEMPERATURES TONIGHT AND WEDNESDAY WILL ACTUALLY RESEMBLE SOMETHING CLOSE TO NORMAL WITH 50S FOR LOWS AND 70S TO AROUND 80 FOR HIGHS. WITH LOW DEWPOINTS FORECAST FOR WEDNESDAY...AFTERNOON HUMIDITY MINIMUMS MAY DIP TO BETWEEN 25-30 PERCENT.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
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AS OF 330 PM EDT TUESDAY... A GOOD DEGREE OF UNCERTAINTY IN THE FORECAST EARLY IN THE SHORT TERM PERIOD AS GUIDANCE DIFFERENCES ON HANDLING OF SURFACE FEATURES... WHICH WILL HAVE AN IMPACT ON RAIN CHANCES WEDNESDAY NIGHT THROUGH THURSDAY. SHORT WAVE ENERGY EJECTING OUT OF AN WESTERN UPPER LEVEL RIDGE WILL COMBINE WITH SOME SHORT WAVE ENERGY ROTATING AROUND AN UPPER TROF OVER THE GREAT LAKES AND HEAD IN OUR DIRECTION. THIS WILL HELP DRIVE DEVELOPMENT OF A SURFACE LOW OVER THE SOUTHEAST US LATE WEDNESDAY NIGHT...WHICH WILL THEN MOVE OFF THE MIDDLE ATLANTIC COAST BY THURSDAY NIGHT. THE OPERATIONAL GFS RUN IS ON BOARD WITH OTHER MODELS IN HANDLING OF DYNAMICS BUT IS MUCH LESS AGGRESSIVE AND FURTHER EAST IN DEVELOPING PRECIPITATION OVER THE AREA. OTHER OPERATIONAL RUNS AND ENSEMBLES DO GENERATE A MUCH MORE COHESIVE PRECIPITATION SHIELD NORTH AND WEST OF THE LOW ASSOCIATED WITH ENHANCED LIFT IN DEFORMATION AREAS AND RR QUAD OF UPPER JET WHERE WE NORMALLY EXPECT TO SEE THESE FEATURES. THUS WILL LEAN TOWARD THE WETTER GUIDANCE AND RAMP POPS UP TO HIGH CHANCE FOR MOST AREAS BY LATE WED NIGHT AND THROUGH THURSDAY. BELIEVE THUNDER CHANCES WILL STAY JUST SOUTH OF THE FOOTHILLS/PIEDMONT OF NC SINCE WE WILL BE IN A COOLER AND MORE STABLE ENVIRONMENT WITH THE LOW TRACKING TO OUR SOUTH. AS THE LOW DEPARTS THURSDAY NIGHT...HIGH PRESSURE WILL BUILD IN FROM THE UPPER MIDWEST AND WE WILL SEE STEADILY IMPROVING CONDITIONS WITH QUIET WEATHER EXPECTED AS WE HEAD INTO THE WEEKEND. TEMPERATURES WILL START OFF A BIT COOL ON THURSDAY WITH PRECIPITATION ON THE COOL SIDE OF THE LOW...BUT VALUES WILL REBOUND TO SEASONAL LEVELS WITH GENERALLY UPPER 60S/AROUND 70 BLUE RIDGE WEST AND LOW TO MID 70S EAST.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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AS OF 330 PM EDT TUESDAY... UPPER PATTERN WILL BE DEVELOPING A LARGE TROF OVER THE EASTERN US DURING THE EXTENDED PERIOD...WITH A BERMUDA HIGH OFF THE COAST. THIS WILL GIVE US A VERY COMFORTABLE AND PLEASANT SATURDAY FOLLOWED BY HEAT AND HUMIDITY MOVING BACK INTO THE REGION BY SUNDAY...WITH THE TRULY UNCOMFORTABLE CONDITIONS HOLDING OFF UNTIL THE FIRST PART OF NEXT WEEK. HOWEVER THE CHANCES FOR SHOWERS AND THUNDERSTORMS WILL BE ONLY MODEST AS SIGNIFICANT DYNAMIC FORCING WILL BE ABSENT...LEAVING US TO RELY ON OROGRAPHIC FORCING FROM THE BLUE RIDGE WEST TO FOCUS LIFT AND GENERATE SOME CONVECTIVE ACTIVITY. PWATS WILL ONCE AGAIN BE RISING ABOVE ONE INCH SO THE POSSIBILITY OF LOCAL DOWNPOURS WILL BE INCREASING. BY TUESDAY A COLD FRONT WILL BE APPROACHING FROM THE WEST AND LOOKS TO BRING GREATER COVERAGE OF PRECIPITATION TO THE REGION TUESDAY AFTERNOON AND EVENING. AFTER A COMFORTABLE SATURDAY...EXPECT RISING TEMPERATURES TO BE ABOUT 10 DEGREES ABOVE NORMAL AS WE HEAD INTO NEXT WEEK.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/... AS OF 200 PM EDT TUESDAY... SCATTERED SHOWERS/STORMS OVER THE AREA THIS EVENING WILL DISSIPATE BY SUNSET. A MUCH DRIER AIRMASS WILL ADVECT INTO THE FORECAST AREA OVERNIGHT AND WEDNESDAY. THIS DRY AIRMASS WILL PREVENT DEEP CONVECTION WEDNESDAY. ASIDE FROM THE SHOWER ACTIVITY THIS EVENING ANTICIPATING MAINLY VFR THROUGH THE VALID TAF PERIOD. SOME OF THE MODELS INDICATE THAT A SHALLOW LAYER OF MOISTURE MAY GET TRAPPED UP AGAINST THE WEST SIDE OF THE APPALACHIANS LATE TONIGHT. THIS MAY RESULT IN A PERIOD OF LOW STRATUS 4-8FT AGL VCNTY OF KBLF EARLY WEDNESDAY MORNING. ANY LOW CLOUD THAT DOES FORM SHOULD DISSIPATE QUICKLY WEDNESDAY MORNING. EXTENDED AVIATION DISCUSSION... AN UPPER LEVEL DISTURBANCE WILL LIKELY BRING SOME MVFR CEILINGS AND SHOWERS BACK INTO THE AREA THURSDAY...MOVING OUT FRIDAY MORNING...WITH VFR CONDITIONS RETURNING FRIDAY AFTERNOON AND SATURDAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...PM SHORT TERM...MBS LONG TERM...MBS AVIATION...PM

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