FXUS61 KRNK 081219
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
719 AM EST TUE DEC 8 2009
.SYNOPSIS...
HIGH PRESSURE BUILD INTO THE MID ATLANTIC TODAY. A STRONG AREA
OF LOW PRESSURE WILL MOVE INTO THE GREAT LAKES REGION TUESDAY
NIGHT INTO WEDNESDAY...BRINGING A COMPLEX SERIES OF FRONTS THROUGH
OUR REGION.
&&
.NEAR TERM /THROUGH TONIGHT/...
COMPLEX LOW PRESSURE SYSTEM WILL BE TRACKING THROUGH THE ROCKIES
TODAY AND INTO THE GREAT LAKES TONIGHT. A SHORT WAVE AHEAD OF THIS
SYSTEM IN THE NORTHERN GULF WILL GENERATE A WEAK WAVE OF LOW
PRESSURE ALONG THE WARM FRONT.
SURFACE WEDGE WILL DEVELOP THIS MORNING AND WILL BE ENHANCED AS
PRECIPITATION BEGINS TO FALL INTO THE DRY AIRMASS WE ARE STARTING
OUT WITH. MODELS SHOW THERE IS ENOUGH SATURATION FOR PRECIPITATION
AFTER ABOUT 18Z TODAY IN THE SOUTHWEST HALF OF THE COUNTY WARNING
AREA. TIMING IS SIMILAR ON THE GUIDANCE BUT TEMPERATURE PROFILES ARE
STILL SHOWING SOME DIFFERENCES. THE NAM HAS A VERY STRONG LAYER OF
WARM AIR ABOVE THE WEDGE BY TONIGHT WHILE THE GFS HAS THE COLDEST
PROFILES. THE LOCAL WRF IS A SPLIT BETWEEN THE TWO. EXPECT SOME
EVAPORATION TO COOL TEMPERATURES AND BRING DOWN THE WET BULB BY THIS
EVENING. TEMPERATURES ACROSS THE NEW RIVER VALLEY WILL BE AROUND
FREEZING SO HAVE ISSUED A WINTER WEATHER ADVISORY FOR LATE THIS
AFTERNOON UNTIL UNTIL WEDNESDAY MORNING.
FARTHER NORTH IT TAKES LONGER FOR THE WARM AIR ALOFT TO GET WARM
ENOUGH FOR FREEZING RAIN. EXPECT PRECIPITATION TO BEGIN AS
RAIN...SNOW...OR SLEET NORTH OF ROANOKE AND LYNCHBURG. HAVE ISSUED A
WINTER WEATHER ADVISORY FOR THIS AREA STARTING EARLY SINCE THE ONSET
OF THE PRECIPITATION WILL LIKELY BE SLEET AND ENDING LATER WEDNESDAY
NIGHT.
FOR ALL LOCATIONS...THE WARM FRONT IS PUSHES THE WEDGE OUT BY 09Z
AND ALL MODELS ON BUFKIT WERE SHOWING TEMPERATURES AT ALL LEVEL
RISING WELL ABOVE FREEZING.
MODELS CONTINUE TO SHOW A 50 TO 70 KNOT 850 MB JET THAT STARTS FROM
THE SOUTHEAST THIS EVENING THEN BECOMES SOUTHWEST BY WEDNESDAY
MORNING. THERE IS ENOUGH TIME WITH THE STRONG SOUTHEAST TO SOUTH
WINDS FROM MERCER COUNTY DOWN TO WATAUGA COUNTY FOR SOME HIGH WINDS
SO HAVE ISSUED A HIGH WIND WARNING. THE REST OF THE HIGHER
ELEVATIONS IN SOUTHEAST WEST VIRGINIA INTO BATH COUNTY WILL BE IN A
WIND ADVISORY. BATH COUNTY IS A LITTLE MORE QUESTIONABLE DEPENDING
ON HOW DEEP THE WEDGE IS WHEN THAT JET REACHES THEIR HIGHER
ELEVATIONS TONIGHT.
TEMPERATURES WILL NOT FOLLOW THE TYPICAL DIURNAL TREND. USED THE
ADJMET AS A BASE FOR HOURLY NUMBERS.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
THE PARENT WEATHER SYSTEM WILL BE OCCLUDED OVER THE GREAT LAKES
WEDNESDAY WITH A SECONDARY SURFACE REFLECTION MOVING OUT OF THE AREA
AND INTO THE MID ATLANTIC. RAIN SHOULD STILL BE ENCOMPASSING THE
ENTIRE AREA WEDNESDAY MORNING WITH A DRY SLOT ENTERING THE
SOUTHWESTERN CWA. THE ASSOCIATED COLD FRONT WILL ENTER THE WEST BY
THE AFTERNOON ACCOMPANIED BY STRONG AND GUSTY WINDS. HIGH WIND
WARNINGS/ADVISORIES WILL CONTINUE FOR THESE STRONG AND GUSTY
SOUTHWEST WINDS ACROSS THE EXTREME WESTERN CWA. THERE IS A CATCH 22
WITH THIS WIND EVENT. THE WINDS ASSOCIATED WITH THE DISTURBANCE
WILL SUBSIDE DURING THE EARLY MORNING HOURS WEDNESDAY. A FEW HOURS
LATER...STRONG WINDS WITH THE FRONT WILL BLOW THROUGH. WE COULD
ISSUE HIGH WIND PRODUCTS FOR TUESDAY NIGHT...THEN ANOTHER FOR
WEDNESDAY MORNING FOR STRONG SOUTHWEST WINDS. TO AVOID SOME
CONFUSION...WE WILL CONTINUE WITH ONE SET OF HIGH WIND PRODUCTS
TUESDAY NIGHT INTO WEDNESDAY DESPITE WINDS FALLING BELOW CRITERIA
FOR A FEW HOURS.
FOLLOWING THE FRONTAL PASSAGE...PRESSURE RISES AND A WESTERLY JET
WILL BRING ANOTHER ROUND OF POSSIBLE HIGH WIND WARNING AND
ADVISORIES TO AREA ALONG AND WEST OF THE BLUE RIDGE WEDNESDAY NIGHT
AND THURSDAY. WILL HIGHLIGHT IN THE HWO AND HAVE WINDY/GUSTY
CONDITIONS IN TEXT PRODUCTS. AS THE FRONT PUSHES TO THE EAST COAST
WEDNESDAY NIGHT...BITTER COLD TEMPERATURES AND UPSLOPE SNOW SHOWERS
WILL FOLLOW. TRAJECTORIES ARE FROM THE WEST AND SNOW ACCUMULATIONS
WILL BE CONFIDED TO EXTREME WESTERN SLOPES OF SOUTHEAST WEST
VIRGINIA. SCATTERED FLURRIES WILL BE SEEN ACROSS THE REST OF THE
MOUNTAINS THURSDAY.
WITH THE RAIN EXITING THE AREA BY THE AFTERNOON...TEMPERATURES WILL
LIKELY SOAR IN TO THE 50S ACROSS MOST OF THE AREA...LOW TO MID 60S
ACROSS SOUTHSIDE. WITH THIS WEEKEND SNOW AND COLD
TEMPERATURES...WEDNESDAY MAY SEEM SPRING-LIKE. DO NOT BREAK OUT THE
SPRING CLOTHES....BECAUSE THE WARM TEMPERATURES WILL NOT LAST LONG.
TEMPERATURES BY THURSDAY MORNING WILL BE BACK INTO THE 20S AND 30S
WITH WIND CHILLS VALUES INTO THE TEENS ACROSS SOME MOUNTAIN
LOCATIONS. THURSDAY HIGHS WILL STRUGGLE TO GET ABOVE FREEZING ACROSS
THE WEST WHILE DOWN SLOPING WARMS THE EAST INTO THE 40S. A SECOND
SURGE OF COLD AIR WILL MOVE IN THURSDAY NIGHT WITH MOUNTAIN
TEMPERATURES IN THE TEENS AND 20-25F IN THE PIEDMONT.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
THERE IS REASONABLE AGREEMENT BETWEEN THE GEFS/GFS/ECMWF REGARDING
PRECIPITATION THIS WEEKEND. HOWEVER...THERE IS MUCH DISAGREEMENT
WITH HOW COLD THE ATMOSPHERE MAY BE LEADING UP TO THIS EVENT. VERY
DRY AIR...IN THE FORM OF 8F-15F DEWPOINTS WITH CONTINENTAL HIGH
PRESSURE OVERHEAD WILL PRECEDE THE EVENT FRIDAY INTO FRIDAY NIGHT.
THE 12Z OP GFS IS MUCH COLDER THAN THE 12Z ECMWF AND THE 12Z
GEFS FOR THE ENTIRE EVENT SAT AND SAT NIGHT...SO PRECIP TYPE IS
DIFFICULT THIS FAR OUT. RIGHT NOW THE OP GFS LOOKS TOO
COLD...HOWEVER...DESPITE THE QUICK WAA AT H85...BOUNDARY LAYER IS
GOING TO BE SUBFREEZING CONSIDERING MANY SPOTS WILL DECOUPLE FRIDAY
NIGHT...AND THEN CLOUDS WILL MOVE IN QUICKLY SATURDAY. THIS SHOULD
PREVENT MUCH INSOLATION...AND MAY EVENTUALLY GIVE A SLEET/SNOW MIX IN
THE BLUE RIDGE...WITH POSSIBLY MORE SNOW INTO SE WEST VA.
CONSIDERING UNCERTAINTY WILL KEEP WX TYPE JUST RAIN OR SNOW FOR
NOW. ALONG THE PIEDMONT AND SOUTHSIDE...ONSET OF PRECIP MAY FIRST
BE SNOW BUT THEN QUICKLY CHANGE OVER TO RAIN AS WARM AIR OVERCOMES
ANY WEDGE THAT MAY BE IN PLACE ALONG THE SE CWA. AS WINDS BECOME
MORE S AND SW SATURDAY NIGHT...PRECIP MAY CHANGE TO ALL RAIN SAVE
SE WEST VA. CONJECTURE AT THIS POINT BUT THIS IS DEFINITELY A
SYSTEM TO WATCH FOR WINTRY PRECIPITATION. THE AREA OF LOW PRESSURE
ALONG THE COAST EXITS INTO SUNDAY...WITH UPSLOPE PRECIP ACROSS SE
WEST VA...ALTHOUGH A MOSTLY WEST WIND ISN'T VERY FAVORABLE. ALBEIT
DRY INTO THE END OF THE LONG TERM...H85 TEMPS REMAIN AROUND 0C SO
NO BIG WARMUPS ARE EXPECTED.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
MVFR CEILINGS WILL SPREAD ACROSS THE FORECAST AREA FROM WEST TO
EAST BY THE END OF THE DAY. AS THE AIRMASS BECOMES SATURATED AND
CEILINGS CONTINUE TO LOWER RAIN PRECIPITATION WILL BECOME
WIDESPREAD ACROSS THE AREA. THE NAM...GFS AND LOCAL WRF HAD RAIN
BEGINNING AT BLF AND LWB AROUND 18Z WITH THE PRECIPITATION
REACHING ROA...LYH AND DAN BY 21Z. SNOW AND SLEET ARE LIKELY NORTH
OF ROA AND LYH BY THIS AFTERNOON. THE WINTER MIX WILL CHANGE TO
FREEZING RAIN AFTER 00Z WITH LWB GETTING RAIN FROM 00-05Z. AS
WARMER AIR ADVANCES NORTH INTO THE REGION OVERNIGHT ALL OF
PRECIPITATION WILL CHANGE OVER TO RAIN. MVFR TO IFR CONDITIONS
WILL PERSIST THROUGH THE DAY ON WEDNESDAY.
WINDS JUST ABOVE THE WEDGE OF COLD AIR WILL BE INCREASING FROM THE
SOUTHEAST AND SOUTH TONIGHT. LOW LEVEL WIND SHEAR HAS BEEN ADDED
TO THE TAFS TO REFLECT THE LOWER EDGE OF A 50 TO 70 KNOT LOW LEVEL
JET. A STRONG COLD FRONT WILL COME THROUGH THE AREA ON WEDNESDAY
MORNING. WINDS WILL STAY STRONG AND GUSTY THROUGH WEDNESDAY
NIGHT...BUT WILL BE OUT OF THE WEST TO NORTHWEST BEHIND THE COLD
FRONT.
WINDY AND GUSTY CONDITIONS POSSIBLE INTO THURSDAY NIGHT. HIGH
PRESSURE BUILDS IN ON FRIDAY BRINGING A RETURN TO VFR ACROSS THE
REGION ALONG WITH LIGHTER WINDS. ANOTHER WEAK STORM SYSTEM LOOKS
TO BRING A POSSIBLE MIXED BAG OF PRECIP BACK TO THE AREA WITH
MVFR/IFR CONDITIONS ON SATURDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 6 AM EST
WEDNESDAY FOR VAZ018>020-023-024-034-035.
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM EST
WEDNESDAY FOR VAZ010>016.
HIGH WIND WARNING FROM 4 PM THIS AFTERNOON TO 1 PM EST
WEDNESDAY FOR VAZ007-009-015.
WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 1 PM EST WEDNESDAY
FOR VAZ020.
NC...HIGH WIND WARNING FROM 4 PM THIS AFTERNOON TO 1 PM EST
WEDNESDAY FOR NCZ001-018.
WV...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 6 AM EST
WEDNESDAY FOR WVZ043>045.
HIGH WIND WARNING FROM 4 PM THIS AFTERNOON TO 1 PM EST
WEDNESDAY FOR WVZ042.
WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 1 PM EST WEDNESDAY
FOR WVZ043-045.
&&
$$
SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...RCS
LONG TERM...KM
AVIATION...AMS/RCS
