FXUS61 KRNK 102339
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
639 PM EST THU DEC 10 2009
.SYNOPSIS...
A LARGE HIGH PRESSURE SYSTEM WILL MOVE EAST ACROSS THE
MID ATLANTIC FRIDAY...THEN OFF THE COAST SATURDAY. AN AREA
OF LOW PRESSURE WILL TRACK SOUTH OF THE REGION OVER THE WEEKEND
AND MAY SPREAD WINTRY PRECIPITATION IN OUR AREA LATE SATURDAY
NIGHT INTO SUNDAY.
&&
.NEAR TERM /THROUGH FRIDAY/...
STRONG COLD AIR ADVECTION WILL CONTINUE THROUGH TONIGHT WITH HIGH
PRESSURE SETTLING OVERHEAD FRIDAY. PRESSURE GRADIENT IS FORECAST
TO REMAIN TIGHT THROUGH THE OVERNIGHT AND THEN WEAKEN FRIDAY.
WINDS...ESP IN THE MTNS...WILL REMAIN GUSTY OVERNIGHT. THIS WILL
PROMOTE LOW WIND CHILLS...NEAR ZERO WEST OF THE BLUE RIDGE...AND
COLD ENOUGH FOR A WIND CHILL ADVISORY...M5-M15 FOR PARTS OF THE
VA HIGHLANDS AND INTO THE MTNS OF WVA (GREENBRIER AND NORTH).
WIND GUSTS (40KTS) THAT WOULD SUPPORT THE NEED FOR A WIND
ADVISORY ARE MAINLY CONFINED TO ELEVATIONS ABOVE 3000 FEET. AS
SUCH HAVE TAILORED THE WIND ADVISORY TO JUST THE NC MTNS AND
GRAYSON VA.
TEMPS TONIGHT WILL DIP INTO THE TEENS MTNS...NEAR 20 EAST OF THE
MTNS. WITH COLD CANADIAN HIGH IN FIRM CONTROL FRIDAY...NOT
EXPECTING ANY SIGNIFICANT REBOUND. TEMPS FRIDAY LIKELY TO REMAIN
AOB FREEZING IN THE MTNS FOR MOST OF THE DAY...AND STRUGGLING TO
MAKE IT TO 40 EAST OF THE BLUE RIDGE.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
HIGH PRESSURE OVER SOUTHWEST VIRGINIA SATURDAY MORNING WILL BRING
TRANQUIL WEATHER. WITH MOSTLY CLEAR SKIES AND LIGHT VALLEY
WINDS...WENT BELOW GUIDANCE VALUES FOR LOWS FRIDAY NIGHT.
BUFKIT SOUNDINGS INDICATE HIGH/MID LEVEL CLOUDS INCREASE ON SATURDAY
AS THE SFC HIGH SHIFTS EAST...AND WITH THE ARRIVAL OF WARM AIR
ADVECTION BY SATURDAY AFTERNOON. AT THIS POINT...ALL EYES FOCUS ON
DEVELOPING ISENTROPIC LIFT/WAA ASSOCIATED WITH A SHORT WAVE ZIPPING
THROUGH THE SOUTHEAST US.
CONSIDERING HOW DRY THE LOW LEVELS OF THE ATMOSPHERE WILL BE ON
SATURDAY...LEANING TOWARD THE SLOWER NAM TIMING OF PRECIPITATION
SATURDAY NIGHT. EVEN THE NAM...HOWEVER...NOW BRINGS PRECIP INTO THE
AREA FROM THE SOUTHWEST BEFORE 06Z AND INCREASED POPS DURING THIS
TIME.
FORECAST SOUNDINGS SUGGEST PRECIP FOR MUCH OF THE FORECAST AREA WILL
START AS A WINTRY MIX...CHANGING TO FREEZING RAIN...THEN RAIN BY
MIDDAY SUNDAY WITH STRONG WAA. THIS WINTRY PRECIP THREAT WILL BE
ADDED TO THE HWO.
ISENTROPIC LIFT AND PRECIP COVERAGE DIMINISHES SUNDAY
AFTERNOON...BUT WEAK UPSLOPE WINDS AND SHALLOW MOISTURE MAY KEEP
LINGERING RAIN/SNOW SHOWERS ALONG THE WESTERN SLOPES OF SOUTHEAST WV.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
AREA OF LOW PRESSURE MOVING OUT OF THE GULF OF MEXICO...AND
PROGGED TO AFFECT THE CWA ON TUESDAY TAKING A MORE SOUTHWARD JOG
ON THE ECMWF/GFS/GEFS. HOWEVER...WITH A WEAK 50/50 LOW IN PLACE AND
UPPER RIDGING OVER THE NORTH ATLANTIC...THIS LOW HAS A BETTER
CHANCE OF TAKING MORE OF SW-NE TRACK INTO THE MIDDLE ATLANTIC THAN
THIS WEEKENDS SYSTEM. HOWEVER...DOES NOT APPEAR TO BE MUCH COLD
AIR IN PLACE...UNTIL AFTER THIS SYSTEM EXITS TO THE EAST. IN
FACT...THE BIGGEST CHANGE TO THE LONG TERM WAS TO WARM TEMPS
MONDAY AND TUESDAY...AS H85 ADJUSTMENTS ARE SEVERAL DEGREES WARMER
THAN CURRENT MEX NUMBERS AND GOING FORECAST. COLDER AIR WILL NOT
BE ABLE TO PENETRATE THE MIDDLE ATLANTIC AND SOUTHEAST....UNTIL
ONE OF THE SHRTWVS FROM THE SW CONUS IS ABLE TO PHASE/MERGE WITH
THE POLAR VORTEX MOVING INTO HUDSON BAY. ATTM...APPEARS THAT THE
PREDOMINATE PRECIP TYPE WOULD BE RAIN FOR TUESDAY'S SYSTEM...WITH
SNOW IN SE WEST VA WITH UPSLOPE FLOW INTO WED MORNING. BOTH ECMWF/GFS
ALLOW SUB -10C H85 AIR TO ARRIVE WEDNESDAY ACROSS SE WEST
VA...ALTHOUGH THE BITE WILL BE TAKEN OFF OF THIS CHILL THANKS TO
DOWNSLOPING FURTHER EAST. ONCE THE TROUGH AXIS MOVES INTO OUR
CWA...THE DOWNSLOPE COMPONENT WILL WEAKEN...ALLOWING PERHAPS SOME
LOWER 40S MAX TEMPS TO REACH INTO THE PIEDMONT AND SOUTHSIDE
THURSDAY. CONSIDERING THE HIGH LATITUDE BLOCKING IN PLACE...THE
EASTERN TROUGHINESS COULD BE THE BEGINNING OF A PATTERN
CHANGE...WITH THE COLDER H85 VALUES OFF THE OP GFS FAVORED OPPOSED
TO THE WARMER ECMWF PAST THURSDAY.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
WINDS WILL REMAIN GUSTY AT TIMES THROUGH FRIDAY...WITH 40-50 KTS
STILL AROUND 5KFT....AS HIGH PRESSURE SLOWLY MOVES EAST...WITH A
GRADIENT REMAINING UNTIL 18Z FRI. IF SURFACE WINDS WEAKEN ENOUGH
NEAR DAWN AT LWB...A WIND SHR GROUP MAY BE NECESSARY EARLY FRIDAY. ANY
CLOUD COVER THROUGH TONIGHT WILL BE MAINLY CONFINED TO THE
WINDWARD SLOPES OF WVA...PRIMARILY WEST AND NORTH OF LWB.
ELSEWHERE EXPECT MAINLY CLEAR SKIES WITH VFR CONDITIONS
PREVAILING.
VFR WEATHER WITH UNRESTRICTED FLIGHT CONDITIONS ARE EXPECTED OVER
ALL TERMINAL FORECAST SITES (KROA...KLYH...KDAN...KBLF...KLWB)
SATURDAY...BUT THEN DETERIORATE SATURDAY NIGHT INTO SUNDAY.
AN AREA OF LOW PRESSURE IS EXPECTED TO DEVELOP OVER THE GULF OF
MEXICO SATURDAY...THEN SLIDE TO ALONG THE SOUTH CAROLINA COAST BY
SUNDAY. THIS WILL BRING AN INCREASE IN CLOUD COVER SATURDAY NIGHT
AND A THREAT FOR A WINTRY MIX OVER THE MID ATLANTIC REGION SUNDAY.
THE SYSTEM SHOULD EXIT THE REGION SUNDAY NIGHT WITH IMPROVED
FLIGHT CONDITIONS MONDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WIND CHILL ADVISORY UNTIL 10 AM EST FRIDAY FOR VAZ020.
WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR VAZ015.
NC...WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR NCZ001-018.
WV...WIND CHILL ADVISORY UNTIL 10 AM EST FRIDAY FOR WVZ045.
&&
$$
SYNOPSIS...PM
NEAR TERM...PM
SHORT TERM...PH
LONG TERM...KM
AVIATION...KM/PM
