Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 252314 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 614 PM EST THU DEC 25 2014 .SYNOPSIS...
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HIGH PRESSURE WILL BRING QUIET WEATHER TO THE REGION AS WE HEAD INTO THE WEEKEND. THEN AS THE HIGH PUSHES TO OUR EAST...A COLD FRONT APPROACHING FROM THE WEST WILL RESULT IN A CHANCE OF RAIN FOR SATURDAY NIGHT AND SUNDAY. OUR WEATHER WILL THEN REMAIN UNSETTLED INTO EARLY NEXT WEEK AS HIGH PRESSURE TRIES TO BUILD INTO THE REGION FROM THE WEST...WHILE THE RESIDUAL FRONT STALLS TO THE SE.
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&& .NEAR TERM /THROUGH FRIDAY NIGHT/... AS OF 300 PM EST THURSDAY... WE WILL HAVE QUIET WEATHER THROUGH THE END OF THE WEEK WITH RIDGING ALOFT AND HIGH PRESSURE BUILDING AT THE SURFACE THROUGH TOMORROW AFTERNOON. EXPECT CLEAR SKIES EAST OF THE BLUE RIDGE...BUT NORTHWEST WINDS CONTINUE TO GENERATE UPSLOPE CLOUDS WEST OF THE RIDGE...AND VISIBLE SATELLITE PICS SHOW THE CLOUDS ERODING FROM THE SOUTH A BIT SLOWER THAN ANTICIPATED. MODEL GUIDANCE IS INDICATING THAT MOISTURE TRAPPED UNDER THE SUBSIDENCE INVERSION WILL KEEP THE CLOUDS LINGERING INTO TONIGHT. THE LOWER CLOUDS SHOULD BE GONE AS WE HEAD TOWARD DAYBREAK...BUT MID/HIGH CLOUDS WILL THEN OVERSPREAD THE REGION INTO FRIDAY NIGHT AS THE UPPER RIDGE AXIS PUSHES TO OUR EAST AND A WEAK SHORT WAVE MOVES THROUGH. BLUSTERY NORTHWEST WINDS WILL BE CALMING DOWN AS WE HEAD TOWARD EVENING...THEN EXPECT WINDS TO REMAIN LIGHT THROUGH FRIDAY NIGHT. NIGHT TIME TEMPERATURES WILL BE RUNNING A BELOW NORMAL WITH READINGS GENERALLY IN THE UPPER 20S TO LOWER 30S TONIGHT...BUT FRIDAY SHOULD WARM TO SEASONABLE LEVELS WITH MOST LOCATIONS IN THE 50S TO NEAR 60 DEGREES. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 PM EST THURSDAY... FORECAST AREA WILL BE UNDER THE INFLUENCE OF A HIGH PRESSURE RIDGE OFF THE SOUTHEASTERN U.S. COAST EARLY SATURDAY. THIS WILL MAKE FOR A VERY MILD DAY WITH HIGHS RUNNING WELL ABOVE NORMAL FOR LATE DECEMBER...GENERALLY IN THE 50S TO LOW 60S FAR SE. THE DAY STARTS OUT MOSTLY SUNNY BUT CLOUDS WILL INCREASE THROUGH THE DAY AS A SLOW- MOVING FRONTAL BOUNDARY ASSOCIATED WITH A TROUGH AND SHORT-WAVE OVER THE CENTRAL U.S. IMPINGES ON THE RIDGE BY EVENING. CLOUDS AND POPS WILL INCREASE OVERNIGHT SATURDAY WHICH WILL HELP TO HOLD OVERNIGHT TEMPS UP AT UNSEASONABLY MILD LEVELS...UP TO 15F OR MORE ABOVE NORMAL IN THE MOUNTAINS. HENCE DO NOT EXPECT ANY P-TYPE ISSUES AT THE ONSET OF THIS EVENT AS HIGH CHANCE AND THEN LIKELY POPS DEVELOP FROM EARLY TO MIDDAY SUNDAY. FRONT WILL BE SLOW TO MOVE EAST AS IT ENCOUNTERS THE DEEP-LAYERED SOUTHWEST FLOW AROUND THE SOUTH ATLANTIC RIDGE AND EXPECT CLOUDS AND RAIN CHANCES TO CONTINUE MUCH OF SUNDAY AND ON INTO EARLY MONDAY. WITH NO SIGNIFICANT SOURCE OF COLD AIR THERMAL PROFILES CONTINUE TO INDICATE ALL RAIN FOR THIS EVENT ALTHOUGH 12Z GFS WAS COLDER THAN PREVIOUS RUNS WITH FAR NW GREENBRIER SLIPPING BELOW 0C AT H85 BY 12Z MONDAY..ALBEIT WITH LITTLE OR NO QPF AT THAT TIME. GEM AND ECMWF ARE WARMER AND WETTER WITH QPF BY 12Z MONDAY SHOWING UP TO 0.75 INCHES IN THE SOUTHWEST CWA BUT USED A BLEND OF MODELS AND HPC FOR SUBSTANTIALLY LESS IN THE GRIDS BY THAT TIME...GENERALLY AROUND 0.25 TO 0.50 IN THE SOUTHWEST AND LESSER AMOUNTS NORTH. HIGHS SUNDAY WILL BE MILD AGAIN BUT A LITTLE LESS SO THAN SATURDAY DUE TO FULL OVERCAST...UPPER 40S NW TO MID-50S SHOULD DO IT. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 300 PM EST THURSDAY... EARLY PART OF NEXT WEEK LOOKS TO BE UNSETTLED WITH LARGE SCALE TROUGH OVER THE WESTERN TWO THIRDS OF THE COUNTRY EJECTING AT LEAST ONE FINAL S/WV PIECE OF ENERGY TOWARD SRN APPALACHIANS ON MONDAY...WITH POTENTIALLY SOME VERY LIMITED LINGERING MOISTURE ON WESTERN SLOPES INTO TUESDAY. STILL SOME MODEL DIFFERENCES IN 12Z CYCLES...WITH ECMWF AND CANADIAN REMAINING MOST AGGRESSIVE WITH S/WV AND AMOUNT OF MOISTURE OVERRUNNING THE RNK FCST AREA AS SFC LOW TRACKS TO THE SOUTH. ECMWF IS FASTER THAN WET CANADIAN AND HAS ANY PRECIP EXITING BY MIDDAY MONDAY. GFS AND AT LEAST SOME OF ITS ENSEMBLES ARE WEAKER AND MORE PROGRESSIVE WITH THIS S/WV...KEEPING MOST LIGHT PRECIP TO OUR SOUTH. IN ALL CASES...LOW LEVEL THERMAL PROFILES TOO WARM FOR ANY WINTRY PRECIP. BEST FOR NOW TO GO WITH COMPROMISE OF ALL THESE IDEAS...WHICH ENDS UP BEING CLOSE TO ECMWF BUT LEANING A LITTLE TOWARD GFS. NOT GOING AS WET SLOW AS CANADIAN. BUT WITH UNCERTAINTY THROUGH LATE MONDAY DO NOT FEEL IT PRUDENT TO GO WITH HIGHER THAN 50 POP ANYWHERE...BUT HAVE HIGHEST POPS IN EAST MONDAY WITH EXITING SYSTEM...AS WELL AS LINGERING UPSLOPE CHANCE POPS FAR WEST...AND KEEPING SOME VERY LOW CHANCE POPS INTO MON NIGHT PERIOD. AFTER THAT MODELS NOW IN BETTER AGREEMENT THAT BY MID WEEK A FLAT UPPER TROUGH SETTLES MORE INTO THE EASTERN THIRD OF THE COUNTRY WITH SPLIT FLOW OVER THE ROCKIES...AS SIGNIFICANT ENERGY CUTS OFF FROM THE FLOW OVER SRN CALIFORNIA. GOOD TO SEE ALL THE MODELS AGREEING ON THIS IDEA...YET HAVE TO BE A LITTLE LEERY OF MODEL SKILL IN DEVELOPING THIS CUTOFF...SO STILL CANNOT RULE OUT SOME WEAK WAVES HEADING IN OUR DIRECTION THROUGH MID WEEK...BUT CHANCES LOOK BETTER FOR BROAD DRY BUT COOL SURFACE HIGH TO DOMINATE WITH WESTERLY FLOW...AND PERHAPS STILL JUST ENOUGH MOISTURE TO SNEAK OUT SOME SPRINKLES OR FLURRIES IN THE FAR WEST AT TIMES. HAVE LOWERED POPS TUESDAY TO ONLY SLIGHT CHANCE IN FAR WEST...AND DECIDED TO TAKE OUT COMPLETELY FOR WED GIVEN MODEL AGREEMENT OF DRY HIGH PRESSURE REALLY PUSHING IN FROM WEST...ALTHOUGH STILL SOME WEAKLY CYCLONIC FLOW AT MID LEVELS AND LIKELY SOME LOW LEVEL CLOUDS IN WEST IN ADDITION TO POSSIBILITY OF HIGH LEVEL CLOUDS EVERYWHERE. MOST LIKELY DRY INTO THURSDAY AS WELL...BUT ECMWF ADVERTISING SOME BETTER ENERGY ONCE AGAIN TRYING TO PUSH INTO THE SFC RIDGE LATE IN THE WEEK...LATEST 12Z RUN SLOWED THIS DOWN A BIT...SO HAVE LEFT POPS OUT FOR NOW UNTIL PERHAPS OVERNIGHT...AND THEN WILL HAVE TO SEE WHAT FUTURE RUNS DO WITH THIS BY NEXT FRIDAY. GRADUAL COOLING TREND THROUGH THIS PERIOD DUE TO BROAD BUT RATHER FLAT UPPER TROUGH AND ASSOCIATED LARGE SFC HIGH FROM CENTRAL U.S. SHIFTING TOWARD APPALACHIANS...AND TEMPS WILL END UP PRETTY CLOSE TO SEASONAL NORMS BY MID WEEK. BOTTOM LINE IS NO MAJOR WINTRY WEATHER TO DEAL WITH THROUGH NEW YEARS DAY. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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AS OF 555 PM EST THURSDAY... LOW LEVEL MOISTURE UNDER THE COLD POOL HAS RETREATED NORTH OF THE AREA THIS EVENING AND NOT EXPECTING MUCH IN THE WAY OF ADDED CLOUD COVER OVERNIGHT GIVEN DRY ADVECTION IN PLACE. THIS COMBINED WITH HIGH PRESSURE BUILDING OVERHEAD SHOULD PROVIDE FOR WIDESPREAD VFR TONIGHT UNDER LIGHT WINDS. CANT COMPLETELY RULE OUT SOME SPOTTY FOG LATE...MAINLY IN THE RIVER BOTTOMS NEAR THE AIRPORTS AND ESPCLY OVER THE EAST GIVEN THE WET GROUND FROM RAINFALL ON WEDNESDAY. LATEST MODELS SHOW A GRADUAL LOWERING OF DEWPOINTS AS WELL OVERNIGHT...BUT GIVEN FAVORABLE FORECAST FOG STABILITY VALUES WILL KEEP SOME REDUCED BUT BRIEF VFR/MVFR VSBYS IN SPOTS AT TIMES TOWARD DAYBREAK. HIGH SLIDES TO THE EAST FRIDAY ALLOWING A WEAK RETURN SW FLOW TO DEVELOP BY AFTERNOON. HOWEVER OTHER THAN FOR SOME SHEARED WARM ADVECTION MID/HIGH CLOUDS THE COLUMN REMAINS QUITE DRY SO CONTINUED GOOD FLYING CONDITIONS FOR FRIDAY INTO FRIDAY NIGHT. EXTENDED DISCUSSION... ANOTHER COLD FRONT WILL APPROACH THE REGION SATURDAY AND BE OVER OR JUST WEST OF THE AREA SUNDAY. THIS MAY ALLOW MULTIPLE WEAK WAVES OF LOW PRESSURE TO RIDE UP THE BOUNDARY AND ACROSS THE REGION LATER SATURDAY NIGHT/SUNDAY RESULTING IN PERIODS OF SUB- VFR IN LOWER CIGS/RAIN. BOUNDARY MAY LINGER OVER OR JUST SOUTH OF THE AREA EARLY NEXT WEEK PENDING FUTURE PROGRESS OF THIS SLOW MOVING SYSTEM BY THEN. THIS COULD LEAVE SOME DEGREE OF MOISTURE INCLUDING MVFR CIGS OVER THE TAF SITES INTO AT LEAST MONDAY OR MONDAY NIGHT BEFORE PERHAPS SEEING SOME IMPROVEMENT TO VFR ON TUESDAY.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...MBS NEAR TERM...MBS SHORT TERM...PC LONG TERM...SK AVIATION...AMS/JH/MBS

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