Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 251445 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 945 AM EST THU DEC 25 2014 .SYNOPSIS... A COLD FRONT WAS MOVING EAST TOWARD THE COAST THIS MORNING. HIGH PRESSURE OVER THE GULF COAST WILL THEN BUILD ACROSS THE EASTERN UNITED STATES TODAY AND REMAIN OVER THE REGION THROUGH SATURDAY. ANOTHER COLD FRONT ARRIVES BY SUNDAY WITH THE NEXT CHANCE OF PRECIPITATION. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 930 AM EST THURSDAY... FORECAST IS IN QUITE GOOD SHAPE THIS CHRISTMAS MORNING SO JUST SOME MINOR ADJUSTMENTS TO WORK LATEST OBS INTO GRIDS. LATEST SAT IMAGES AND AREA RADAR LOOPS SHOW THAT NWLY WINDS ACROSS THE REGION ARE GIVING US THE TRADITIONAL UPSLOPE CLOUDS/LIGHT PCPN WEST OF THE BLUE RIDGE WITH DOWNSLOPE CLEARING TO THE WEST. WITH PARENT LOW CONTINUING TO PULL WELL INTO CANADA...LOW LEVEL MOISTURE WILL BE ERODING QUICKLY THIS AFTERNOON AND WINDS WILL BACK AROUND A BIT AS HIGH PRESSURE BUILDS IN FROM THE LOWER MISSISSIPPI VALLEY...ALLOWING FOR STEADY IMPROVEMENT WEST OF THE RIDGE. WINDS HAVE BEEN BLUSTERY THIS MORNING BUT BELOW ADVSY CRITERIA AND LOW LEVEL FLOW WILL BE SLACKENING FROM HERE ON OUT. PREVIOUS AFD... COLD FRONT WAS JUST EXITING THE FAR EASTERN COUNTIES OF THE FORECAST AREA. THE WESTERN EDGE OF THE FRONTAL PRECIPITATION EXTENDED FROM CHARLOTTESVILLE TO DANVILLE. LATEST HRRR HAS THIS PRECIPITATION EXITING THE EASTERN COUNTY WARNING AREA AROUND 10Z/5AM. WILL KEEP CHANCE OF SHOWERS IN THE WESTERN UPSLOPE AREAS THIS MORNING. MOISTURE ABOVE 700 MB MOVES OUT OF THE FORECAST AREA THIS MORNING ALONG WITH THE COLD FRONT. MODELS ERODE THE LOW LEVEL MOISTURE THIS EVENING. WILL KEEP SOME CLOUD COVER IN THE NORTHWEST THROUGH THIS EVENING. LOCATIONS TO THE EAST WILL CLEAR OUT THIS MORNING. SURFACE HIGH PRESSURE WAS OVER THE GULF COAST. THE HIGH MOVES ACROSS THE SOUTHEAST UNITED STATES TODAY AND WILL BE CENTERED OVER THE FORECAST AREA BY FRIDAY MORNING. SURFACE DEW POINTS DROP INTO THE 20S BY LATE TODAY. WITH THE DRY AIR MASS THAT WILL BE IN PLACE...DIURNAL VARIATION IN TEMPERATURES WILL BE 20 TO 25 DEGREES. EXPECT VALLEYS TO DECOUPLE THIS EVENING. WILL KEEP LOW TEMPERATURES AT OR BELOW GUIDANCE TONIGHT. MSAS SHOWED BEST PRESSURE RISES OVER THE GREAT LAKES EXTENDING INTO NORTHERN VIRGINIA. 850 WINDS WILL BE AROUND 50 KNOTS FROM THE WEST EARLY THIS MORNING...BUT WILL STEADILY DIMINISH TO BELOW 20 KNOTS TONIGHT.
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&& .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM EST THURSDAY... HIGH PRESSURE WILL KEEP THE REGION DRY THROUGH SATURDAY. TEMPERATURES WILL MODERATE AS THE CENTER OF THE HIGH SHIFTS EAST AND INCREASING SOUTHWEST WINDS USHER IN A WARM AIR ADVECTION PATTERN ACROSS THE REGION. SATURDAY NIGHT THROUGH SUNDAY NIGHT A BAROCLINIC ZONE WILL ESTABLISH ITSELF FROM NEAR THE MISSISSIPPI DELTA NORTHEAST INTO THE LOWER OHIO VALLEY. A SERIES OF DISTURBANCES WILL TRACK ALONG THIS BOUNDARY AND BRING MULTIPLE PERIODS OF RAIN ACROSS THE FORECAST AREA. CONFIDENCE IS LOW REGARDING TIMING AND TRACK OF EACH OF THESE SYSTEMS BASED UPON THE GENEROUS SPREAD IN MODEL SOLUTIONS OF THE FEATURES. HOWEVER...BY THE DAY SUNDAY...IT IS LIKELY THAT RAIN WILL OCCUR DURING SOME PERIOD OF THE DAY TIME HOURS...AND LIKEWISE DURING THE SUNDAY NIGHT PERIOD. TEMPERATURES WILL BE ABOVE NORMAL DURING THIS PERIOD OF THE FORECAST. && .LONG TERM /MONDAY 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 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. 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 /15Z THURSDAY THROUGH MONDAY/... AS OF 1125 PM EST WEDNESDAY... COLD FRONT WAS WELL EAST OF THE REGION THIS MORNING AND RAIN HAS MOVED OUT OF THE VIRGINIA AND NORTH CAROLINA FOOTHILLS. WINDS WILL GUST FROM THE WEST UP TO 30 KNOTS BEHIND THE FRONT THIS MORNING. THIS WILL COMBINE WITH LINGERING LOW LEVEL MOISTURE TO PRODUCE MVFR CLOUDS IN KBLF AND KLWB AS WELL AS RAIN AND SNOW SHOWERS IN THE MOUNTAINS. HIGH PRESSURE OVER THE GULF COAST REGION WILL MOVE INTO THE AREA TONIGHT...RESULTING IN DIMINISHING WINDS AND UPSLOPE CLOUDS. HIGH CONFIDENCE THAT RAIN/SNOW SHOWERS WILL DISSIPATE BY 00Z TONIGHT WITH THE CLOUDS OVER THE MOUNTAINS BECOMING SCATTERED THIS EVENING. VFR CONDITIONS ARE EXPECTED FRIDAY. EXTENDED DISCUSSION... HIGH PRESSURE SHOULD BUILD OVER THE SOUTHEAST...WHICH WILL PROVIDE VFR WEATHER WITH LIGHTER WINDS THROUGH FRIDAY NIGHT. ANOTHER COLD FRONT WITH ASSOCIATED LOW PRESSURE WILL APPROACH THE REGION SATURDAY AND BE OVER OR JUST WEST OF THE AREA SUNDAY. BOUNDARY MAY LINGER OVER OR JUST SOUTH OF THE REGION EARLY NEXT WEEK WITH POSSIBLE RETURN TO VFR MONDAY AFTERNOON. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...MBS/AMS SHORT TERM...DS LONG TERM...SK AVIATION...AMS/JH

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