Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231948 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 348 PM EDT WED APR 23 2014 .SYNOPSIS...
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COOL HIGH PRESSURE OVER THE OHIO VALLEY WILL BUILD SOUTHEAST PASSING OVERHEAD TONIGHT AND THURSDAY. ANOTHER COLD FRONT WILL CROSS THE AREA FROM THE WEST ON FRIDAY.
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&& .NEAR TERM /THROUGH THURSDAY/...
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AS OF 210 PM EDT WEDNESDAY... MAINLY A TEMP FORECAST OVER THE NEXT 24 HOURS AS THE UPPER TROUGH DEPARTS OVERNIGHT AND SHORTWAVE RIDGING BUILDS OVERHEAD ON THURSDAY. THIS WILL ALLOW THE COOL SURFACE HIGH TO SLIDE SE ACROSS THE REGION LATER TONIGHT AND THEN TO THE COAST ON THURSDAY. THIS WILL KEEP VERY DRY AIR IN PLACE BUT ALLOW FOR DIMINISHING WINDS TONIGHT AND THE ONSET OF WEAK SW FLOW THURSDAY AFTERNOON AS THE RIDGE DEPARTS. MAY START TO SEE SOME HIGH CLOUDS RETURN FROM THE WEST LATER THURSDAY OTRW CLEAR OVERNIGHT AND MAINLY SUNNY THURSDAY. MAIN CONCERN WITH LOW TEMPS TONIGHT GIVEN POTENTIAL FOR GOOD RADIATIONAL COOLING AFTER MIDNIGHT AS DEWPOINTS REMAIN LOW AND WINDS GO LIGHT UNDER CLEAR SKIES. THIS WOULD SUPPORT VALUES GOING BELOW FREEZING MOUNTAINS...WITH SOME 20S VALLEYS...AND WELL INTO THE 30S OUT EAST WHERE THE GROWING SEASON HAS STARTED. HOWEVER SIMILAR TO TEMPS A FEW NIGHTS BACK...DEWPOINT DEPRESSIONS LOOK QUITE LARGE GIVEN DRY AIR WHICH WONT SUPPORT MUCH FROST OUTSIDE THE BOTTOMS/LOW SPOTS...WHILE COLDEST VALUES WILL BE BRIEF NEAR DAWN PENDING HOW FAR WINDS DECOUPLE. THUS AFTER COORDINATION WITH SURROUNDING SITES...HAVE OPTED OUT OF A FROST ADVISORY FOR NOW WHILE INCREASING THE PATCHY COVERAGE EAST LATE WITH LOWS MAINLY MID/UPPER 30S. SHOULD QUICKLY RECOVER ON THURSDAY PER 85H WARMING AND WEAK SW FLOW AIDED BY HEATING OF DRY AIR WHICH WILL PUSH MOST INTO THE 60S IF NOT LOW 70S IN SPOTS.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
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AS OF 330 PM EDT WEDNESDAY... SHORT WAVE COMING OUT OF THE MID MISSISSIPPI VALLEY WILL CROSS THROUGH THE OHIO VALLEY THURSDAY NIGHT...REACHING THE FAR WESTERN COUNTY WARNING AREA AROUND 12Z/8AM FRIDAY MORNING. THIS FEATURE WEAKENS AS IT CROSSES THE AREA. THE CORRESPONDING SURFACE COLD FRONT IS EXPECTED TO PASS THROUGH DURING THE DAY FRIDAY. WILL SPEED UP ARRIVAL TIME OF PRECIPITATION FRIDAY MORNING. WITH THIS TIMING...APPEARS THE BEST OPPORTUNITY FOR THUNDERSTORMS WILL BE EAST OF THE BLUE RIDGE...AHEAD OF THE FRONT IN THE AFTERNOON. VERY LITTLE CHANGE IN AIRMASS BEHIND THE FRONT ON FRIDAY NIGHT. HAVE MAINTAINED A LOW CHANCE OF PRECIPITATION IN THE FAR NORTHERN COUNTY WARNING AREA AS A SECONDARY FRONT COMES IN FROM THE NORTH ON SATURDAY.
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&& .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
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AS OF 330 PM EDT WEDNESDAY... A MORE PRONOUNCED PUSH OF COLD AIR WILL COME IN BEHIND A FRONT ON SATURDAY NIGHT. THE FRONT WILL STALL SOUTH OF THE FORECAST AREA ON SUNDAY. HIGH PRESSURE BUILDS IN NORTH OF THE BOUNDARY AND WILL KEEP THE WINDS FROM THE EAST ON SUNDAY. HAVE KEPT SUNDAY MAXIMUM TEMPERATURES BELOW GUIDANCE WITH THE EXPECTED EAST COMPONENT OF THE WINDS AND INCREASING CLOUD COVER. THE UPPER PATTERN BECOMES MORE AMPLIFIED THROUGH THIS TIME FRAME. WILL HAVE AN UPPER RIDGE OVER THE EASTERN UNITED STATES SATURDAY NIGHT THROUGH MONDAY. THEN A CLOSED LOW TRACKS THROUGH THE CENTRAL UNITED STATES TUESDAY AND WEDNESDAY. SURFACE LOW PRESSURE DEVELOPS IN THE CENTRAL PLAINS BY MONDAY WITH BROAD FLOW OFF THE GULF OF MEXICO. MOISTURE WILL LIFT OVER THE STALLED BOUNDARY IN THE TENNESSEE VALLEY ON MONDAY. MODELS WERE OFFERING DIFFERENT SOLUTIONS FOR THE TRACK OF THE SURFACE LOW TUESDAY AND WEDNESDAY WITH THE ECMWF MUCH FARTHER NORTH AND WEST THAN THE GFS. WPC WAS LEANING TOWARD A TRACK OF THE SURFACE LOW THROUGH THE OHIO VALLEY WITH A STRONG COLD FRONT COMING THROUGH THE REGION ON WEDNESDAY. WITH OVERALL SOUTHWEST FLOW AND THE FRONT REMAINING TO THE WEST UNTIL WEDNESDAY...HAVE TRENDED TOWARD WARMER TEMPERATURES FOR MONDAY THROUGH WEDNESDAY.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... AS OF 1255 PM EDT WEDNESDAY... WIDESPREAD VFR CONDITIONS UNDER MAINLY CLEAR SKIES WILL PREVAIL DURING THE NEXT 24 HOURS INTO THURSDAY AFTERNOON. GUSTY NW WINDS WILL CONTINUE THIS AFTERNOON...WITH SUSTAINED 12-17 KTS INCLUDING GUSTS TO 20-25 KTS. WINDS WILL DIMINISH AND BECOME LIGHT TONIGHT WITH RETURN OF LIGHT SOUTH TO SOUTHWESTERLY FLOW THURSDAY AS HIGH PRESSURE PASSES OVERHEAD AND OFF THE MID ATLANTIC COAST. EXTENDED AVIATION DISCUSSION... A COLD FRONT WILL CROSS THE AREA EARLY FRIDAY...WITH A BRIEF PERIOD OF MVFR RESTRICTIONS POSSIBLE AS SHOWERS/ISOLATED STORMS MOVE EAST WITH THE FRONT THROUGH THE AREA. STRONG HIGH PRESSURE BUILDS IN FRIDAY NIGHT INTO SATURDAY WITH VFR EXPECTED UNDER GUSTY NORTHWEST WINDS. WINDS DIMINISH SATURDAY NIGHT FOLLOWED BY HIGH PRESSURE PASSING ACROSS SUNDAY WITH FAIR DRY WEATHER. MOISTURE WILL START TO RETURN NORTH SUNDAY NIGHT AS A BOUNDARY LIFTS NE AHEAD OF LOW PRESSURE ACROSS THE CENTRAL U.S. THIS WILL LIKELY BRING SUB-VFR CONDITIONS LATER SUNDAY NIGHT AND ESPCLY ON MONDAY. && .FIRE WEATHER...
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AS OF 330 PM EDT WEDNESDAY... RED FLAG WARNING REMAINS IN EFFECT FROM THE VIRGINIA BLUE RIDGE NORTHWARD INTO NORTH CENTRAL VA FOR CONTINUED GUSTY NORTHWEST WINDS AND LOW HUMIDITY. FIRE DANGER STATEMENT ELSW FOR INCREASED FIRE DANGER WHERE WINDS WONT BE QUITE AS STRONG AND FUELS A BIT WETTER. OTRW WINDS WILL RANGE FROM 15 TO 20 MPH SUSTAINED...WITH GUSTS OF 25 TO 30 MPH THROUGH EARLY THIS EVENING. HUMIDITY MINIMUMS NEAR 20 PERCENT WILL ALSO BE COMMON RESULTING IN CONTINUED MARGINAL RED FLAG CRITERIA UNTIL AROUND SUNSET. IN ADDITION...IT HAS BEEN 7 DAYS SINCE MEASURABLE RAINFALL HAS OCCURRED IN ROANOKE VALLEY AND THE IMMEDIATE BLUE RIDGE COUNTIES...INCLUDING THE NEW RIVER AND SHENANDOAH VALLEYS. THIS HAS ALLOWED LEAVES AND BRUSH TO BECOME DRY AND VERY RECEPTIVE TO FIRE...10 HOUR FUEL MOISTURE DROPPING TO AROUND 7 PERCENT OR LOWER. CONCERN IS FOR RAPID FIRE SPREAD IF A WILDFIRE OCCURS. WINDS SHOULD FINALLY DIMINISH OVERNIGHT AS HIGH PRESSURE BUILDS IN WITH HUMIDITY LEVELS RECOVERING TO 70-80 PERCENT OR HIGHER AFTER MIDNIGHT. WINDS WILL BE MUCH LIGHTER ON THURSDAY AND GRADUALLY TURN MORE SW UNDER 10 MPH. HOWEVER RELATIVE HUMIDITY WILL AGAIN DROP WITH HEATING DURING THE AFTERNOON WITH LEVELS LIKELY DROPPING TO BELOW 25-30 PERCENT ACROSS MOST OF THE REGION. A COLD FRONT MAY BRING SOME WETTING RAIN IN THE FORM OF SCATTERED SHOWERS AND ISOLATED STORMS DURING FRIDAY.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR VAZ007- 009>020-022>024-032>035-047. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/PM NEAR TERM...JH SHORT TERM...AMS LONG TERM...AMS AVIATION...JH/PM FIRE WEATHER...JH/PM

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