Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 250434 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1134 PM EST WED DEC 24 2014 .SYNOPSIS...
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A COLD FRONT WILL SWING EAST ACROSS THE REGION OVERNIGHT BRINGING GUSTY WEST WINDS AND DRIER AIR BY CHRISTMAS MORNING. HIGH PRESSURE WILL THEN BUILD OVER THE EASTERN UNITED STATES THURSDAY INTO THE WEEKEND WITH GENERALLY FAIR WEATHER EXPECTED INTO SATURDAY. ANOTHER COLD FRONT ARRIVES BY SUNDAY WITH THE NEXT CHANCE OF SHOWERS FOR LATE IN THE WEEKEND.
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&& .NEAR TERM /THROUGH THURSDAY/... AS OF 925 PM EST WEDNESDAY... COLD FRONT NOW PUSHING ACROSS THE FAR WESTERN COUNTIES SHOULD REACH THE BLUE RIDGE BY MIDNIGHT AND OUT EAST DURING THE EARLY MORNING HOURS. MOST SHOWERS HAVE ALL BUT DISSIPATED ALONG THE BOUNDARY UPON ENCOUNTERING THE LINGERING WEDGE BUT STILL APPEARS A FEW LIGHTER BANDS OF SHOWERS POSSIBLE OVER THE WEST DURING THE NEXT COUPLE OF HOURS. HOWEVER NOT ENOUGH TO KEEP ANY THUNDER GOING NW WITH A GRADUAL REDUCTION IN POPS WEST UNTIL SEEING THE BRIEF UPSLOPE KICK IN LATER ON. OTHER CONCERN IS OUT EAST WHERE THE FRONT WILL LIKELY SLOW UNDER THE SW FLOW ALOFT ALLOWING PERHAPS ANOTHER SPEED MAX TO ZIP UP FROM THE SOUTH INTO THE EARLY MORNING HOURS. LATEST HRRR CONTINUES TO SUGGEST A FEW ADDED HOURS OF RAIN ESPCLY PIEDMONT AND SUPPORTED BY THE 00Z NAM SO ADDED IN MORE CHANCE POPS EAST OVERNIGHT ESPCLY GIVEN FILLING BACK IN OF PRECIP ON REGIONAL RADARS TO THE SOUTH ATTM. OTRW SEEING A TEMP DROP OF ALMOST 10 DEGREES IN AN HOUR DURING THE FROPA WITH GUSTS TO 30-35 KTS BUT STILL BELOW ADVISORY GIVEN LEVELING OFF OF SPEEDS ONCE THE BOUNDARY CROSSES. EXPECT FOG TO FINALLY FADE ENOUGH AFTER MIDNIGHT TO DROP MENTION FOR THE MOST PART OVERNIGHT AS WELL. BUMPED UP LOW TEMPS IN THE EAST WHERE ONCE THE WEDGE BREAKS EXPECT A BRIEF TEMP SURGE FOR A COUPLE HOURS BEFORE GRADUAL COOLING REDEVELOPS BEHIND THE FRONT. HOWEVER GIVEN MIXING EXPECT LOWS TO BE A FEW DEGREES WARMER THAN EARLIER THOUGHT. PREVIOUS UPDATE AS OF 520 PM EST WEDNESDAY... SENT AN UPDATE TO BOOST DENSE FOG COVERAGE ALONG/EAST OF THE BLUE RIDGE THIS EVENING BEFORE THE COLD FRONT FINALLY ARRIVES AND HELPS MIX THINGS OUT BEFORE MIDNIGHT. ALSO ISSUED A SPS FOR THE FOOTHILLS AND PIEDMONT GIVEN THE QUICK DROPOFF IN VISIBILITIES OVER THE PAST HOUR. MAY NEED A BRIEF ADVISORY IF CONDITIONS WORSEN BUT HOLDING OFF FOR NOW GIVEN THE GRADUAL APPROACH OF THE FRONT FROM THE WEST. ALSO TWEAKED POPS DOWN AND ADDED MORE DRIZZLE BLUE RIDGE EAST WHILE DELAYING CONVECTION OVER THE WEST. MOST LATEST SHORT TERM SOLUTIONS QUICKLY WEAKEN THIS SHALLOW CONVECTION UPON CROSSING THE WESTERN SLOPES IN THE NEXT COUPLE OF HOURS BUT SOMETHING TO WATCH. TEMPS REMAIN STUCK IN THE 40S ACROSS THE CENTRAL AND EAST SO ADJUSTED DOWN FOR STEADY READINGS THERE THIS EVENING BEFORE SEEING A QUICK JUMP WHEN THE FRONT ARRIVES AFTER 00Z. PREVIOUS DISCUSSION AS OF 340 PM EST WEDNESDAY... AT 3 PM...THE WEDGE OF COOL SHALLOW AIR REMAINED ALONG AND EAST OF THE BLUE RIDGE. THIS MORNING...A SHORT WAVE PASSED OVER THIS WEDGE AND BROUGHT A FAIR AMOUNT OF RAIN (0.50 TO 1.50 INCHES) TO THE REGION. THIS WAVE HAS PASSED WITH ONLY LIGHT RAIN/DRIZZLE LEFT IN ITS WAKE. GRAY CLOUDY CONDITIONS WILL PERSIST INTO THIS EVENING WHILE A LULL IN THE RAIN WILL LAST FOR A FEW HOURS BEFORE A COLD FRONT AND ASSOCIATED SHOWERS ENTER THE WEST LATE THIS AFTERNOON...EXITING THE PIEDMONT LATE THIS EVENING. THE WEDGE HAS LEFT MOST OF THE AREA IN A STABLE ENVIRONMENT BUT CAN NOT RULE OUT A RUMBLE OF THUNDER FROM ELEVATED CONVECTION AS THE COLD FRONT PASSES THIS EVENING. SHOWERS WITH THE FRONT MAY HAVE SOME GUSTY WINDS WITH THEM...BUT IT WILL BE THE SHARP PRESSURE RISES BEHIND THE FRONT THAT WILL BRING A FEW HOURS OF BREEZY AND GUSTY CONDITIONS TO THE REGION. THE STRONGER LONGER LASTING BREEZY AND GUSTY WINDS WILL OCCUR EARLY CHRISTMAS MORNING WITH A TIGHT PRESSURE GRADIENT...MODEST COLD AIR ADVECTION AND A 50 KT LOW LEVEL JET. HIGH PRESSURE BUILDS IN QUICKLY THURSDAY AFTERNOON TO SHUT DOWN THE WINDS. AS THE WEDGE ERODES...TEMPERATURES ARE WARMING INTO THE MID TO UPPER 50S. AREA ALONG AND EAST OF THE BLUE RIDGE...PARTICULARLY IN THE FOOTHILLS AND PIEDMONT COUNTIES...MAY NOT SEE HIGH TEMPERATURES TODAY UNTIL THIS EVENING (5P-7P). ONCE THE FRONT MOVES EAST...TEMPERATURES WILL SLOWLY DROP INTO THE 30S AND 40S. AS THE UPPER LEVEL TROUGH PASSES OVERHEAD FRIDAY MORNING...A FEW SHOWERS ARE POSSIBLE. TEMPERATURES AND BOUNDARY LAYER ARE TO WARM FOR SNOW EXCEPT FOR HIGHER ELEVATIONS AND WESTERN SLOPES. AFTER A BREEZY COOL MORNING...AFTERNOON HIGHS WILL WARM INTO THE 40S WEST TO 50S EAST. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... AS OF 250 PM EST WEDNESDAY... TRANQUIL AND MILD CONDITIONS ARE IN STORE FOR THE INITIAL POST- CHRISTMAS PERIOD OVER THE CENTRAL/SOUTHERN APPALACHIAN REGION. A SURFACE AND UPPER RIDGE OF HIGH PRESSURE CENTERED OVER THE SOUTHEASTERN U.S. WILL DOMINATE THE PATTERN IN OUR REGION FOR SEVERAL DAYS AS UPPER TROUGHING AND STORMINESS IS CONFINED TO THE WESTERN CONUS. VERY MILD TEMPS ON FRIDAY WITH WIDESPREAD 50S LIKELY FOR HIGHS UNDER A PLEASANT LATE DECEMBER SUN. WINTER WEATHER LOVERS PREPARE TO BE LESS THAN PLEASED. THE HIGH WILL SHIFT OFF THE EAST COAST BY LATE SATURDAY AS HEIGHT FALLS AND A COLD FRONT OVER THE MID-MISSISSIPPI VALLEY SLOWLY PUSH EAST. SKIES WILL BE CLEAR FRIDAY NIGHT AND MOST OF SATURDAY WITH TEMPERATURES AGAIN RUNNING 10-15F ABOVE LATE DECEMBER NORMALS...LOWS IN LOW TO MID-30S AND HIGHS LOW 50S TO NEAR 60. HIGH CLOUDS WILL INCREASE LATE SATURDAY AHEAD OF THE FRONT WITH ANOTHER MILD NIGHT IN STORE AS TEMPS LIKELY TO REMAIN ABOVE FREEZING IN NEARLY ALL AREAS. POPS SLOWLY INCREASE AS WELL TO CHC BY EARLY SUNDAY IN THE FAR WEST WITH RAIN AS THE P-TYPE IN ALL BUT VERY COLDEST LOCATIONS. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 300 PM EST WEDNESDAY... LATE WEEKEND INTO MID NEXT WEEK LOOKS TO BE POTENTIALLY UNSETTLED WITH LARGE SCALE TROUGH OVER THE WESTERN TWO THIRDS OF THE COUNTRY KICKING SEVERAL SHORT WAVES OUT INTO SOUTHERN APPALACHIAN REGION. MODELS OFFER SIGNIFICANT DIFFERENCES IN THE STRENGTH AND TIMING OF THESE WAVES...AND AMOUNT OF GULF MOISTURE THEY ARE ABLE TO TAP. ALSO RUN-TO-RUN INCONSISTENCIES ARE MAKING THIS OVERALL A RATHER LOW CONFIDENCE FORECAST. AM CONCERNED THAT THE ECMWF IN PARTICULAR HAS HAD A TENDENCY TO DIG THE SHORT WAVES A LITTLE TOO MUCH AND THEN ULTIMATELY DRIVE A DEEPENING SFC WAVE TOO FAR NORTH UP THE APPALACHIANS OR TO THE WEST OF US. THE FLATTER MORE PROGRESSIVE GFS HAS BEEN BETTER AS OF LATE. LATEST 12Z ECMWF HAS TRENDED TOWARD THE MORE SUBDUED GFS FOR THE FIRST SYSTEM HEADED UP OUR WAY SUNDAY INTO MONDAY...WHILE CANADIAN NOW HAS A MUCH STRONGER SYSTEM TRACKING JUST TO OUR SOUTH ON MONDAY AND MONDAY NIGHT. WILL LEAN MORE TOWARD THE WEAKER/FLATTER IDEA ADVERTISED IN THE LATEST GFS AND NOW ECMWF...AT LEAST THROUGH TUES. ECWMF IS A LITTLE STRONGER WITH ANOTHER WAVE ON WEDNESDAY...WHILE GFS IS FASTER...COLDER...AND GENERALLY KEEPS IT SOUTH OF US. WHILE CONFIDENCE IN THE TIMING AND STRENGTH OF THESE SYSTEMS IS QUITE LOW RIGHT NOW...THERE IS MORE CLARITY THAT THIS WILL AT THE VERY LEAST BE A CLOUDY PERIOD...AND THAT LOW LEVEL TEMPS AND THICKNESSES WILL GENERALLY BE WARM ENOUGH NOT TO HAVE ANY REAL PRECIP TYPE CONCERNS...WITH THE POSSIBLE EXCEPT OF HIGHEST RIDGES ACROSS THE FAR NORTH SUNDAY AND MONDAY...WITH ANY SYSTEM ON WEDNESDAY THERE COULD BE ENOUGH DAMMING SETTING UP THAT OVERRUNNING COULD BE SOME SORT OF WINTRY MIX...BUT NOT EVEN SURE WE WILL HAVE PRECIP ON WED. ECMWF WOULD SUGGEST FREEZING RAIN. A LITTLE MORE CONFIDENCE AT THE BEGINNING OF THIS PERIOD...SO HAVE SOME LIKELY AND HIGH CHC POPS IN FOR SUNDAY...BUT ALL RAIN...AND MOST LIKELY LIGHT. AS WE GET INTO THE WEEK...THE LARGE SFC HIGH NOSES IN MORE AND MORE AND EACH DAY LOOKS A LITTLE COOLER THAN THE PREVIOUS ONE WHICH IS REFLECTED IN THE TEMPERATURE FORECAST. WHILE I HAVE LOWERING POPS EACH DAY...LARGELY DUE TO INCREASING UNCERTAINTY...AM KEEPING A LOW CHC TO SLIGHT CHC IN THROUGH THE PERIOD WITH MORE INDICATION OF SOME WINTRY PRECIP AS WE GET INTO TUES NIGHT AND WED. OVERALL...FORECAST REALLY REFLECTS A VERY BROAD BRUSH RATHER THAN GOING EXACTLY WITH ANY ONE SOLUTION...AND EXPECT THERE WILL BE QUITE A FEW CHANGES TO THE EARLY WEEK FORECAST AS WE GET INTO THE WEEKEND. NOT MUCH CHANCE FOR A MAJOR STORM DURING THIS PERIOD...AND AFTER SUNDAY ITS POSSIBLE THAT DRY BUT COOL HIGH PRESSURE MANAGES TO DOMINATE...BUT BEST GUESS FOR NOW IS SOMETHING IN BETWEEN. AS ALWAYS...STAY TUNED! && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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AS OF 1125 PM EST WEDNESDAY... FLYING CONDITIONS WILL GRADUALLY IMPROVE OVERNIGHT AS A COLD FRONT SWEEPS ACROSS FROM THE WEST AND REMOVES THE LINGERING LOW CLOUDS...FOG AND DRIZZLE THAT HAVE PERSISTED WITHIN A STRONG WEDGE FOR THE LAST COUPLE OF DAYS. HOWEVER EASTERN SITES SUCH AS KLYH/KDAN MAY STILL BE SLOW TO IMPROVE TO MVFR UNTIL EARLY THURSDAY WHEN BETTER MIXING BEHIND THE FRONT DEVELOPS. THUS WILL BE HOLDING ONTO LINGERING IFR THERE INTO THE OVERNIGHT WITH A SLOW RISE IN BOTH CIGS AND VSBYS BY DAWN. ELSW STILL LOOKING AT MVFR CIGS FOR THE MOST PART WITH IFR FAR WEST GIVEN UPSLOPE FLOW INTO KBLF OVERNIGHT. A FEW SHOWERS STILL POSSIBLE OVER THE AREA DURING THE NEXT FEW HOURS BEFORE MORE UPSLOPE NATURE RAIN/SNOW SHOWERS GET GOING TOWARD SUNRISE. WEST WINDS WILL REMAIN STRONG AT TIMES OVER THE WEST OVERNIGHT WITH GUSTS TO 30-40 MPH POSSIBLE WITH LIGHTER SPEEDS WITHIN THE LINGERING WEDGE AT KLYH/KDAN. THURSDAY...MVFR CEILINGS AND UPSLOPE RAIN/SNOW SHOWERS SHOULD PERSIST IN THE MOUNTAINS...MAINLY KBLF/KLWB INTO EARLY AFTERNOON WITH VFR CONDITIONS RETURNING IN THE PIEDMONT. IN BETWEEN...SOME LINGERING MVFR STRATO-CU POSSIBLE AROUND KBCB/KROA THURSDAY MORNING BEFORE THINGS MIX OUT UNDER GUSTY WESTERLY WINDS BY MIDDAY. WINDS AGAIN MAY GUST TO 25-30 KTS THURSDAY MORNING BEFORE QUICKLY DIMINISHING DURING THURSDAY AFTERNOON AS HIGH PRESSURE BUILDS IN. EXTENDED DISCUSSION... THURSDAY NIGHT AND FRIDAY HIGH PRESSURE SHOULD BUILD OVER THE SOUTHEAST...WHICH WILL PROVIDE VFR WEATHER WITH LIGHTER WINDS. ANOTHER COLD FRONT WITH ASSOCIATED LOW PRESSURE WILL APPROACH THE REGION SATURDAY AND BE OVER OR JUST WEST OF THE AREA SUNDAY. GIVEN THE SLOWER TRENDS...APPEARS WEATHER MAY STAY VFR FOR SATURDAY WITH SUB-VFR CONDITIONS RETURNING WITH CLOUDS/PRECIP ON SUNDAY FOR NOW. BOUNDARY MAY LINGER OVER OR JUST SOUTH OF THE REGION EARLY NEXT WEEK WITH POSSIBLE RETURN TO VFR MONDAY AFTERNOON AT THIS POINT.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/RCS NEAR TERM...JH/RCS SHORT TERM...PC LONG TERM...SK AVIATION...JH/RCS

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