FXUS61 KRNK 110229
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
929 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/...
HIGH PRESSURE CONTINUES TO EDGE CLOSER TO THE AREA FROM THE WEST. 
PRESSURE GRADIENT STILL REMAINS OVER THE AREA WITH A LOW LEVEL JET 
AROUND 45 KTS. THE STRONGEST PRESSURE RISES AND COLD AIR ADVECTION 
IS MOVING EAST OF THE AREA THIS EVENING. THE WINDS OVER THE LAST 
COUPLE OF HOURS HAVE DROPPED BELOW ADVISORY CRITERIA AT ALL SITES. 
EVEN THOUGH TONIGHTS WINDS WILL REMAIN WINDY...WILL GO AHEAD AND 
CANCEL THE WIND ADVISORY OVER THE NORTH CAROLINA HIGH COUNTRY. 

BITTERLY COLD DRY AIR WILL CONTINUE TO FILTER INTO THE REGION 
TONIGHT. DEW POINTS WILL DROP INTO THE SINGLE DIGITS. LUCK 
ENOUGH...TEMPERATURES WILL NOT DRIP TO THE DEW POINT BUT WILL BE 
COLD AND IN THE 10-15F RANGE ACROSS THE MOUNTAINS. MOUNTAIN VALLEYS 
MAY FAIR A LITTLE WARMER IN THE UPPER TEENS. WITH WIND REMAINING IN 
THE HIGHER ELEVATIONS...WIND CHILLS WILL FALL BELOW ZERO EARLY THIS 
MORNING. MORE AREAL COVERAGE OF BELOW ZERO WIND CHILLS ACROSS 
GREENBRIER AND BATH COUNTIES TO HAVE AN WIND CHILL ADVISORY FOR 
FRIDAY MORNING. EAST OF THE BLUE RIDGE...TEMPERATURES WILL BOTTOM 
OUT IN THE LOWER 20S WITH CHILLS IN THE 10-20F RANGE.

MINOR FLOODING WILL CONTINUE OVERNIGHT ALONG THE JAMES RIVER NEAR 
BREMO BLUFF...THE ROANOKE RIVER AT RANDOLPH...AND THE DAN RIVER AT 
SOUTH BOSTON. THE FLOOD STATEMENT (FLSRNK) WILL BE UPDATED BY 
1100 PM.

PREVIOUS DISCUSSION...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 /03Z 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.

&&

.HYDROLOGY...
MINOR FLOODING WILL CONTINUE OVERNIGHT ALONG THE JAMES RIVER NEAR 
BREMO BLUFF...THE ROANOKE RIVER AT RANDOLPH...AND THE DAN RIVER AT 
SOUTH BOSTON. SEE THE FLOOD STATEMENT (FLSRNK) FOR MORE DETAILS.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WIND CHILL ADVISORY UNTIL 10 AM EST FRIDAY FOR VAZ020.
NC...NONE.
WV...WIND CHILL ADVISORY UNTIL 10 AM EST FRIDAY FOR WVZ045.

&&

$$
SYNOPSIS...PM
NEAR TERM...PM/RCS
SHORT TERM...PH
LONG TERM...KM
AVIATION...KM/PM
HYDROLOGY...RCS