Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 160842 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 442 AM EDT WED APR 16 2014 .SYNOPSIS...
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HIGH PRESSURE WILL MOVE UP THE OHIO RIVER VALLEY THIS MORNING AND AFTERNOON...AND THEN BUILD SOUTHWARD ALONG THE EASTERN FACE OF THE APPALACHIANS. THIS HIGH PRESSURE WILL REMAIN IN CONTROL OF THE WEATHER PATTERN THROUGH FRIDAY. A WEAK DISTURBANCE MOVING TOWARD THE REGION FROM THE NORTHWEST MAY BRING THE NEXT CHANCE OF SHOWERS TO THE REGION FOR EARLY IN THE WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 400 AM EDT WEDNESDAY... SURFACE OBSERVATIONS INDICATING WIND SPEEDS DIMINISHING AS HIGH PRESSURE ADVANCES UP THE OHIO RIVER VALLEY. STILL A FEW BANDS OF LOW CLOUDS ACROSS SOUTHEAST WEST VIRGINIA...BUT THESE BANDS WILL CONTINUE TO FADE THROUGH THE MORNING AS WINDS BECOME INCREASINGLY NORTHERLY AS THE HIGH APPROACHES. ALREADY OBSERVING TEMPERATURES BELOW FREEZING ACROSS PORTIONS OF THE PIEDMONT...AND AS ATMOSPHERIC MIXING DECREASES WITH DIMINISHING WIND SPEEDS...EXPECT MORE LOCATIONS TO FALL BELOW FREEZING BEFORE SUNRISE. HIGH PRESSURE WILL MOVE SOUTH OF THE GREAT LAKES INTO NEW ENGLAND THIS AFTERNOON...WHILE ALSO BUILDING SOUTHWARD TO HUG THE EASTERN FACE OF THE APPALACHIANS. AS THE HIGH BUILDS IN...WILL SEE WINDS GRADUALLY SHIFT FROM NORTHERLY THIS MORNING...TO NORTHEASTERLY BY THIS EVENING. FORECAST MODELS OFTEN UNDERESTIMATE THE STRENGTH OF THESE HIGH PRESSURE WEDGES HUGGING THE MOUNTAINS...AND WENT A FEW DEGREES BELOW MODEL GUIDANCE FOR AFTERNOON HIGHS...DESPITE THE ABUNDANT SUNSHINE. EXPECT AFTERNOON TEMPERATURES TO CLIMB INTO THE UPPER 40S AND LOW 50S AREAWIDE. WINDS WILL BECOME LIGHT BY SUNSET AND...WHEN COMBINED WITH CONTINUED CLEAR SKIES...WILL RESULT IN ANOTHER NIGHT OF STRONG RADIATIONAL COOLING...ALLOWING TEMPERATURES AREAWIDE TO AGAIN FALL BELOW FREEZING. IN ADDITION...THE LACK OF ATMOSPHERIC MIXING WILL ALSO PROMOTE AREAS OF FROST. WILL THEREFORE ISSUE ANOTHER FREEZE WARNING FOR AREAS EAST OF THE BLUE RIDGE FOR WEDNESDAY NIGHT. OVERNIGHT LOWS WILL BOTTOM OUT RANGING FROM THE MID 20S TO THE LOW 30S MOST LOCATIONS...WITH A FEW VALLEY BOTTOMS FALLING INTO THE UPPER TEENS.
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&& .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
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AS OF 400 AM EDT WEDNESDAY... MODELS IN GOOD AGREEMENT AT THE BEGINNING OF THIS PERIOD AS A LARGE CANADIAN HIGH DRIFTS TO THE NORTHEAST OF THE REGION. THIS WILL SET UP A WEDGE PATTERN...INITIALLY DRY. 850MB TEMPS REBOUND TOWARD 0C THU FROM THE VERY COLD -12C CURRENTLY IN PLACE...BUT THEN HOVER IN THE -2C TO 4C RANGE NORTH-SOUTH THROUGH FRIDAY AS NE FLOW FROM THE PARENT SFC HIGH SETS UP ACROSS THE REGION THUS RETARDING ANY APPRECIABLE WARMING. SKIES SHOULD REMAIN MOSTLY SUNNY THU...HELPING TO WARM TEMPS FROM WIDESPREAD BELOW FREEZING TEMPS AGAIN DURING THE EARLY MORNING. GIVEN THE PATTERN...HAVE FAVORED THE COLDER ECMWF MOS GUIDANCE. FRIDAY...THE MODELS BEGIN TO DIVERGE...WHICH BECOMES A MORE APPRECIABLE DIVERGENCE BY SATURDAY...ON THE TRACK/INTENSITY OF A NORTHERN STREAM SHORT WAVE AND THE TRACK/INTENSITY/DEVELOPMENT OF A SOUTHERN STREAM CLOSED LOW ALONG THE SOUTHEAST U.S. COAST. HPC MODEL PREFERENCE IS WITH THE ECMWF SOLUTION...WHICH FAVORS DEVELOPMENT OF A FAIRLY DEEP CLOSED LOW ALONG THE NE FL/GA/SC COAST. THE GFS FAVORS THE NORTHERN STREAM SHORT WAVE...AND AS A RESULT SHOWS ANOTHER FAIRLY SIGNIFICANT SURGE OF COLD AIR INTO THE REGION SATURDAY WITH UPSLOPE -SHRA POSSIBLE ACROSS THE ALLEGHANYS. WHILE THE ECMWF DOES NOT DISCOUNT THIS TROUGH...IT SHOWS LITTLE PCPN AND LITTLE APPRECIABLE COLD ADVECTION...FOCUSING MORE ENERGY INTO THE SE U.S. SYSTEM...HENCE INDICATING MORE SUBSIDENCE ACROSS OUR CWA. THE NAM AND CANADIAN OFFER SLIGHTLY DIFFERENT SOLUTIONS AS WELL...BOTH SHOWING GREATER POTENTIAL FOR -SHRA FURTHER NORTH WITH THE SOUTHERN SYSTEM AND THE NAM HAVING MORE FROM BOTH. AT ANY RATE...AT LEAST THROUGH SAT AND UNTIL THE MODELS CAN COME TO BETTER CONSENSUS...HAVE KEPT THE SOUTHERN COUNTIES DRY...BUT DID INCREASE POPS ACROSS THE NC PIEDMONT TO 14 PERCENT LEANING TOWARD THE ECMWF. FOR THE MOUNTAINS...HAVE SHOWN SLIGHT CHC POPS INTO GREENBRIER/SUMMERS IN ASSOCIATION WITH NW FLOW SHORT WAVE...DEPICTED TO SOME EXTENT BY ALL MODELS. USED A ECMWF/GFS BLEND FOR TEMPS FRI-SAT...BUT HAVE LEANED TOWARD THE COLDER ECMWF MOS AS NOTED ABOVE WITH PREVAILING NE FLOW ACROSS THE PIEDMONT AND/OR COLDER NW FLOW SAT BEHIND SHORT WAVE.
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&& LONG TERM /SUNDAY THROUGH TUESDAY/... AS OF 415 AM EDT WEDNESDAY... MUCH OF WHAT OCCURS...AT LEAST AT THE BEGINNING OF THIS PERIOD...WILL DEPEND ON THE TRACK OF THE SE U.S. UPPER LOW. BY MON...THIS SYSTEM SHOULD BE FAR ENOUGH EAST TO NO LONGER INFLUENCE THE AREA. OVERALL...MOSTLY DRY CONDITIONS EXPECTED...BUT WILL NEED TO WATCH SE-E PARTS OF THE CWA FOR CLOUD COVER AND COOL...MARITIME EASTERLY FLOW AS LOW PRESSURE REMAINS JUST SOUTHEAST OF THE CWA. A WEAK UPPER RIDGE WILL BUILD OVER THE TOP OF THE SE UPPER LOW PROMISING TO CONTINUE A GRADUAL WARMING TREND THROUGH THE PERIOD...BUT AGAIN LIKELY TEMPERED BY THE EASTERLY FLOW IN PLACE BETWEEN THE LOW TO THE SOUTHEAST AND SFC HIGH PRESSURE TO THE NORTHEAST. MODEL DIFFERENCES CONTINUE TO BE QUITE SIGNIFICANT WITH RESPECT TO THE NEXT SYSTEM POTENTIALLY IMPACTING THE AREA EARLY NEXT WEEK...WITH THE ECMWF BRINGING ANOTHER AREA OF CLOSED LOW PRESSURE...ALBEIT WEAKER...INTO THE SE U.S. CLOSED LOW...WHILE THE GFS BRINGS MORE OF AN OPEN TROUGH TOWARD THE REGION. AT ANY RATE...EXPECT INCREASING CHANCES FOR RAIN BY MON-TUE OF NEXT WEEK. INSTABILITY APPEARS MARGINAL AT THIS POINT...ESPECIALLY PER ECMWF SOLUTION. THUS...HAVE MADE NO CHANGES TO CURRENT LONG TERM GRIDS WITH LOW CHC POPS AND NO MENTION OF TSRA. SURFACE HIGH FILLING IN BEHIND FRIDAY`S WEAK BOUNDARY EVENTUALLY COVERS NEW ENGLAND AND THE ENTIRE MIDDLE ATLANTIC TO CLOSE THE WEEKEND. AGAIN...THIS HIGH MAY EVENTUALLY PARK OVER NEW ENGLAND SETTING UP ANOTHER DRY WEDGE PER THE ECMWF. THUS...SUNDAY MAY BE COLDER THAN SATURDAY. THE GFS HAS ANOTHER SURFACE HIGH JUST OFF THE CAROLINA COAST...WITH ELIMINATES THE EASTERLY COMPONENT/DRY WEDGE...GIVING MORE OF A SOUTHERLY BREEZE AND A WARMER SUNDAY. WILL GO BETWEEN THE MEX AND ECMWF MOS FOR HIGHS ON SUNDAY. THE PATTERN REMAINS DRY AND BENIGN...UNTIL NEXT TUESDAY NIGHT...WHEN BOTH THE ECMWF AND GFS AGREE ON A FRONT WITH RAIN SHOWERS. WENT WITH CHC POPS AT THE END OF THE LONG TERM WITH THE MODEL AGREEMENT AT THIS TIMERANGE. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... AS OF 200 AM EDT WEDNESDAY... WIND SPEEDS CONTINUE TO ABATE THIS MORNING AS HIGH PRESSURE SHIFTS UP THE OHIO RIVER VALLEY TO BECOME THE DOMINANT FEATURE IN THE WEATHER PATTERN. WINDS WILL VEER AS THE HIGH CONTINUES EAST... BECOMING NORTHERLY BY SUNRISE...WHICH WILL HELP ERODE REMAINING LOW CLOUDS ACROSS SOUTHEAST WEST VIRGINIA AND THE MOUNTAIN EMPIRE. CLEAR SKIES WILL THEN PERSIST THROUGH THE REMAINDER OF THE TAF PERIOD. AS HIGH PRESSURE APPROACHES NEW ENGLAND...IT WILL ALSO BUILD SOUTHWARD...WEDGING AGAINST THE EASTERN FACE OF THE APPALACHIANS. WINDS WILL BECOME EAST NORTHEASTERLY DURING EARLY AFTERNOON...AND WILL REMAIN SO INTO THURSDAY. WIND SPEEDS ARE EXPECTED TO REMAIN AROUND 10KT DURING THE AFTERNOON WITH SLIGHTLY HIGHER GUSTS...AND WILL DROP TO 2KT TO 4KT AFTER SUNSET. HIGH PRESSURE WILL LINGER INTO FRIDAY...MAINTAINING VFR CONDITIONS THROUGH THE END OF THE WORKWEEK UNDER LIGHT EAST TO NORTHEAST FLOW. THE NEXT COLD 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 FOR THE WEEKEND WITH HIGH PRESSURE FOLLOWING THIS SYSTEM FOR SUNDAY. && .HYDROLOGY... AS OF 200 AM EDT TUESDAY... RAINFALL OF 1 TO 2 INCHES ON TUESDAY WILL CAUSE RISES ALONG MAINSTEM RIVERS INTO MIDWEEK. MUCH OF THE HEAVIEST RAIN OCCURRED ALONG THE DAN RIVER BASIN WITH LEVELS FORECASTED TO REACH MINOR FLOOD STAGE AT SOUTH BOSTON WEDNESDAY MORNING. OTHER LOCATIONS ALONG THE DAN AROUND DANVILLE AND PACES AS WELL AS RANDOLPH ALONG THE LOWER ROANOKE RIVER WILL SEE BANKFULL CONDITIONS. A RIVER FLOOD WARNING REMAINS IN EFFECT AT SOUTH BOSTON INTO LATE THURSDAY. && .CLIMATE...
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AS OF 400 AM EDT WEDNESDAY... POSSIBLE RECORD LOWS FOR APRIL 16TH BLACKSBURG 24F 2008...FORECASTED LOW 24F. LEWISBURG 25F 2008....FORECASTED LOW 21F. APRIL 17TH RECORD LOWS ROANOKE 27F 1980......FORECASTED LOW 31F. LYNCHBURG 27F 1904....FORECASTED LOW 30F. DANVILLE 28F 1962.....FORECASTED LOW 30F. BLUEFIELD 25F 2001....FORECASTED LOW 32F. BLACKSBURG 20F 1974...FORECASTED LOW 26F. LEWISBURG 25F 2001....FORECASTED LOW 20F.
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&& .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR VAZ022>024- 032>035-043>047-058-059. FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT THURSDAY FOR VAZ022>024-032>035-043>047-058-059. NC...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR NCZ003>006-019- 020. FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT THURSDAY FOR NCZ003>006-019-020. WV...NONE.
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&& $$ SYNOPSIS...NF NEAR TERM...NF SHORT TERM...RAB LONG TERM...KM/RAB AVIATION...NF HYDROLOGY...JH CLIMATE...JC/KM

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