Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 151146 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 746 AM EDT TUE APR 15 2014 .SYNOPSIS... A STRONG COLD FRONT WILL SWEEP THROUGH THE REGION THIS AFTERNOON...BRINGING ABOUT A RETURN TO WINTERLIKE TEMPERATURES AND EVEN A CHANCE FOR SNOW IN THE MOUNTAINS. HIGH PRESSURE WILL BUILD ACROSS THE AREA WEDNESDAY AND REMAIN IN CONTROL OF THE AREAS WEATHER THROUGH FRIDAY WITH MODERATING TEMPERATURES. A WEAK DISTURBANCE MOVING TOWARD THE REGION FROM THE NORTHWEST MAY BRING THE NEXT CHANCE OF SHOWERS TO THE REGION FOR THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 445 AM EDT TUESDAY... MULTIPLE WEATHER CONCERNS TO TRAVERSE THE REGION NEXT 12 HOURS AS A STRONG COLD FRONT MOVES THROUGH THE REGION FROM WEST TO EAST THIS AFTERNOON...ULTIMATELY BRINGING A RETURN TO WINTERLIKE TEMPERATURES FOR THE FIRST TIME IN NEARLY TWO WEEKS. FIRST CONCERN IS MODERATE TO EVEN HEAVY RAINFALL IN ADVANCE OF A STRONG COLD FRONT SLATED TO MOVE FROM WEST TO EAST THROUGH THE REGION THIS AFTERNOON. MOST OF THE HEAVY RAIN IS ONGOING NOW...AND SHOULD BE PRIMARILY FOCUSED OVER THE PIEDMONT THROUGH EARLY AFTERNOON...WHERE IT HAS BEEN MUCH OF THE NIGHT. SINCE MIDNIGHT...RAINFALL OF 1 TO 1.5 INCHES HAS BEEN COMMON THROUGH THE NC PIEDMONT COUNTIES INTO PATRICK...HENRY...AND FRANKLIN COUNTIES IN VA. STOKES COUNTY CALLED AROUND 1 AM TO REPORT MINOR STREET FLOODING. AS THE RAINFALL SHIFTS FURTHER EAST...IT WILL MOVE INTO AREAS WHERE THE FFG VALUES ARE HIGHER...GENERALLY 2.5 TO 3.0 INCHES IN THREE HOURS...WHICH IS NOT EXPECTED. IN COORDINATION WITH NEIGHBORING OFFICES...DECIDED NOT TO ISSUE FLOOD WATCH AND HANDLE POTENTIAL FLOODING PROBLEMS WITH SPS/FLS AS NEEDED. NEXT CONCERN WILL BE THE WIND BEHIND THE FRONT. VERY TIGHT PRESSURE GRADIENT WILL DEVELOP QUICKLY ALONG WITH STRONG CAA. STRONGEST WINDS WILL BE ALONG THE BLUE RIDGE AS TYPICAL FOR THIS TYPE OF PATTERN. HOWEVER...WINDS DO NOT MEET HIGH WIND WARNING CRITERIA...SO HAVE ISSUED A WIND ADVISORY FROM WATAUGA NORTHEASTWARD TO ROANOKE FROM 2 PM TO MIDNIGHT. THE TIME FRAME OF THE VERY STRONG WINDS WILL BE A NARROW WINDOW...AND MOSTLY FOCUSED WITHIN A FEW HOURS OF FRONTAL PASSAGE. STRONG CAA WILL QUICKLY NET WINTERLIKE TEMPERATURES JUST A FEW HOURS AFTER FRONTAL PASSAGE. LOW-LEVEL THICKNESS VALUES QUICKLY DROP TO CRITICAL SNOW LEVELS WITHIN A FEW HOURS ACROSS THE MOUNTAINS AS 850MB TEMPS PLUNGE TOWARD -12C IN EASTERN WV BY 06Z WED. HAVE CONTINUED MENTION OF -SHSN THROUGH THE MOUNTAINS OF EASTERN WV...SOUTHWEST VA...NORTHWEST NC AS TEMPERATURES DROP. ACCUMULATIONS UP TO AN INCH APPEAR POSSIBLE...MAINLY AFTER 00Z WHEN SFC TEMPS FALL BELOW FREEZING IN THOSE AREAS. A NON-DIURNAL TEMPERATURE TREND IS CLEARLY IN ORDER FOR TODAY...WITH THE MILD 50 AND 60 DEGREE READINGS THIS MORNING QUICKLY GIVING WAY TO 30S AND 40S BY LATE AFTERNOON. THE FREEZE THREAT TONIGHT IS COVERED IN THE SHORT TERM SECTION BELOW. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... AS OF 400 AM EDT TUESDAY... WILL START THE EVENING OFF WITH NORTHWEST WINDS HOLDING STRONG ACROSS THE MOUNTAINS...WITH 45 TO 55 MPH GUSTS AT SPOTS ALONG THE BLUE RIDGE SOUTH OF ROANOKE. TEMPERATURES BY SUNSET WILL BE COLD ENOUGH THAT RAIN SHOWERS WILL HAVE ALREADY CHANGED TO SNOW ALONG OUR WESTERN RIDGELINES...WITH AN ADDITIONAL HALF INCH OF SNOW POSSIBLE THROUGH MIDNIGHT ACROSS WESTERN GREENBRIER COUNTY. WIND SPEEDS AND SNOW SHOWERS WILL GRADUALLY DIMINISH THROUGH THE NIGHT AS COLD HIGH PRESSURE MOVES UP THE OHIO RIVER VALLEY. ALL MODELS ARE IN GOOD AGREEMENT THAT TEMPERATURES WILL FALL BELOW FREEZING AREAWIDE BY SUNRISE WEDNESDAY...WITH WIND SPEEDS DIMINISHING ENOUGH ACROSS THE PIEDMONT FOR A FEW PATCHES OF FROST TO POSSIBLY DEVELOP. A FREEZE WARNING WILL BE IN EFFECT FOR COUNTIES EAST OF THE BLUE RIDGE FOR TUESDAY NIGHT...MEANING THAT ANY VEGETATION SENSITIVE TO FREEZING TEMPERATURES MAY BE KILLED IF NOT PROTECTED. ALTHOUGH WE DO NOT BEGIN ISSUING FREEZE WARNINGS FOR THE MOUNTAINS UNTIL BEGINNING APRIL 30TH...WE SHOULD BE MINDFUL THAT THE RECENT WARM WEATHER MAY HAVE CAUSED SENSITIVE VEGETATION TO BEGIN GROWING THERE AS WELL...WHICH WOULD ALSO BE AFFECTED BY THE COLD. AT ANY RATE...HIGH PRESSURE WILL BUILD SOUTHWARD TO HUG THE EASTERN FACE OF THE APPALACHIANS ON WEDNESDAY...ALLOWING WINDS TO SHIFT INCREASINGLY NORTHEASTERLY. CAN EXPECT ANOTHER ROUND OF FREEZING OVERNIGHT LOWS FOR WEDNESDAY NIGHT AREAWIDE...THIS TIME WITH A MUCH BETTER CHANCE FOR AREAS OF FROST TO DEVELOP DUE TO THE LIGHT WIND SPEEDS AND CLEAR SKIES. AS SUCH...EXPECT WE WILL NEED ANOTHER FREEZE WARNING FOR WEDNESDAY NIGHT EAST OF THE BLUE RIDGE. LOOK FOR A SLIGHT WARMING TREND AS WE HEAD INTO THE FINAL DAYS OF THE WORKWEEK AS WINDS ALOFT SHIFT SOUTHWESTERLY AHEAD OF ANOTHER APPROACHING TROUGH. AT THE SURFACE...BELIEVE MODELS ARE TRYING TO ERODE THE COLD HIGH PRESSURE WEDGED AGAINST THE APPALACHIANS TOO QUICKLY...AND THEREFORE HAVE UNDERCUT MODEL GUIDANCE BY A FEW DEGREES FOR THURSDAY AND FRIDAY TEMPERATURES. THAT STATED...BELIEVE THURSDAY NIGHT LOWS WILL BE A FEW DEGREES WARMER...WITH THE POTENTIAL FOR FREEZING TEMPERATURES LIMITED TO THE SHENANDOAH VALLEY AND THE MOUNTAINS. THE HIGH PRESSURE WEDGE WILL FINALLY BEGIN TO BREAK FRIDAY EVENING AS ANOTHER LOW PRESSURE SYSTEM MOVES ACROSS THE GREAT LAKES... DRAGGING A COLD FRONT TOWARD OUR AREA. EXPECT A FEW SHOWERS ACROSS THE MOUNTAINS AS THE FRONT PASSES...BUT WITH NO RETURN FLOW OF MOISTURE FROM THE GULF OR ATLANTIC AHEAD OF THE BOUNDARY... PRECIPITATION IS EXPECTED TO BE LIGHT. && .LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 355 PM EDT MONDAY... WEAK TROUGH THROUGH THE MIDWEST EVENTUALLY PUSHES EAST...AND WEDGING HIGH PRESSURE EVENTUALLY DEPARTS THIS WEEKEND. WITH A RATHER DRY ANTECEDENT AIRMASS...QUESTIONABLE IF THIS MIDWEST TROUGH PRODUCES ANY PRECIP ONCE IT ARRIVES ACROSS THE OHIO VALLEY AND MIDDLE ATLANTIC THIS WEEKEND. OP GFS IS FAR MORE WET THAN THE ECMWF. THUS...POPS WERE KEPT RATHER LOW. A ZONAL UPPER FLOW TAKES SHAPE BY LATE WEEKEND INTO EARLY NEXT WEEK...WITH UNEVENTFUL AND DRY WEATHER CONTINUING ACROSS THE REGION. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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AS OF 745 AM EDT TUESDAY... CIGS/VSBYS HAVE BEEN MORE VARIABLE AND WITH INCREASING PERIODS OF MVFR OR BETTER EARLIER THAN EXPECTED. HOWEVER...STILL EXPECT MVFR TO OCCASIONALLY IFR CIGS/VSBYS IN AREAS OF RAIN SHOWERS AND FOG EXPECTED THROUGH AROUND 16Z...AT WHICH POINT A STRONG COLD FRONT WILL MOVE THROUGH...IMPROVING CIGS TO VFR AFT 18Z PIEDMONT...BUT WITH CONTINUED MVFR CIGS IN UPSLOPE FLOW AND -SHRA OR EVEN POSSIBLY -SHSN EASTERN WV TAF SITES. BCB WILL SEE PERIODS OF MVFR CIGS CONTINUING THROUGH EVENING. SKC EXPECTED EAST OF THE ALLEGHANYS AFT 04Z...EARLIER PIEDMONT. VSBYS SHOULD IMPROVE TO VFR ALL AREAS BY LATE AFTERNOON...EARLY AFTERNOON ACROSS THE PIEDMONT ONCE THE FRONT MOVES THROUGH. WINDS WILL BE ONE OF THE GREATEST CONCERNS THIS TAF VALID CYCLE...MAINLY BEHIND THE FRONT. AHEAD OF THE FRONT...A GENERAL INCREASE OF SSE- SSW WINDS OF 10-20KTS CAN BE EXPECTED...BUT BEHIND THE FRONT...EXPECT WNW-NW 15-20KTS WITH GUSTS 30-40KTS. IT APPEARS THAT THIS WILL ONLY BE FOR A NARROW WINDOW OF ABOUT 12 HOURS...THEN DIMINISHING FAIRLY RAPIDLY AFT 04Z. MEDIUM CONFIDENCE IN CIGS/VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND DIR/SPD THROUGH THE TAF VALID PERIOD. LOW CONFIDENCE IN POTENTIAL FOR -SHSN AT BLF/LWB THROUGH TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... MUCH DRIER AIR WORKS IN BEHIND THE FRONT WEDNESDAY WITH STRONG HIGH PRESSURE WEDGED IN FROM THE NE. THIS SHOULD ALLOW A RETURN TO WIDESPREAD VFR WITH THIS SCENARIO CONTINUING THURSDAY WITH HIGH PRESSURE RIDGING IN FROM OFF NEW ENGLAND AND THE NEXT COLD FRONT TO THE NW. THIS FRONT APPROACHES FROM THE WEST FRIDAY BUT APPEARS SLOW AND WEAK ENOUGH TO MAINTAIN VFR DURING THE DAY FOR NOW. THIS SYSTEM MAY BRING MVFR CIGS TO THE MOUNTAINS SATURDAY ALONG WITH A FEW SHOWERS OTRW VFR ELSW TO START THE WEEKEND.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR VAZ022>024- 032>035-043>047-058-059. WIND ADVISORY FROM 2 PM THIS AFTERNOON TO MIDNIGHT EDT TONIGHT FOR VAZ014>017-022. NC...FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR NCZ003>006- 019-020. WIND ADVISORY FROM 2 PM THIS AFTERNOON TO MIDNIGHT EDT TONIGHT FOR NCZ001-002-018. WV...NONE. && $$ SYNOPSIS...RAB NEAR TERM...RAB SHORT TERM...NF LONG TERM...KM AVIATION...JH/RAB

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