-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 060944
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
444 AM EST FRI DEC 6 2013

.SYNOPSIS...
-- Changed Discussion --
A COLD FRONT MOVES ACROSS SOUTHEASTERN WEST VIRGINIA TODAY THEN
CRAWLS ACROSS VIRGINIA TONIGHT. ARCTIC HIGH PRESSURE WELL BEHIND
THE FRONT WILL WEDGE SOUTH ALONG THE MOUNTAINS SATURDAY...BEFORE
INTERACTING WITH PRECIPITATION RETURNING NORTH BY SUNDAY.
SOUTHWESTERLY FLOW RETURNS MONDAY BEFORE A STRONGER COLD FRONT
ARRIVES TUESDAY MORNING. COLD AND DRY HIGH PRESSURE RETURNS BY
TUESDAY NIGHT.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 400 AM EST FRIDAY...

ALTHOUGH THE MAIN BODY OF RAINFALL WILL BE SLOW TO MOVE EAST
TODAY...FROM TIME TO TIME RENEGADE SHOWERS WELL EAST OF THE FRONT
WILL DEVELOP IN THE VERY MOIST WARM SECTOR WITH DECENT ISENTROPIC
LIFT. ATTM...A QUICK MOVING SLUG OF RAIN IS ENTERING NW NC AND
WILL REACH THE NEW RIVER VALLEY IN A FEW HOURS IF IT HOLDS
TOGETHER. SHALLOW NATURE OF THE FRONT EDGE OF THE ARCTIC AIR IS
ALREADY ARRIVING ACROSS SE WEST VA...WITH TEMPS AT LWB/BLF HEADED
DOWN. HOWEVER...REALLY TRICKY TEMP FORECAST THERE AS THE BOUNDARY
GETS PUSHED BACK WEST A TAD WITH AREA OF LOW PRESSURE DEVELOPING
ALONG THE FRONT AND PASSING OVER THE NEW RIVER VALLEY LATER
TODAY. WOULD THINK LWB/BLF HAVE REACHED THEIR HIGHS FOR TODAY IN
THE MORNING BUT LAV GUIDANCE SAYS NO. HARD TO SEE MUCH TEMP RISE
SO WILL KEEP TEMPS STEADY THERE TODAY. NICE SHOT OF WINDS THANKS
TO THE ARRIVAL OF A LOW LEVEL JET STREAK AS LOW PRESSURE MOVES SW
TO NE RIGHT ALONG THE BLUE RIDGE LATE AFTERNOON. NOT OUT OF THE
QUESTION THAT ONE OF THE STRONGER RENEGADE SHOWERS IS ABLE TO TAP
INTO THESE GUSTY WINDS ALOFT PRODUCING A 40 MPH GUST AS THE
SHOWERS RACE TO THE NE. ALSO CAN`T RULE OUT A RUMBLE OF THUNDER OR
TWO...AS A FEW STRIKES WERE EVEN OBSERVED A FEW HOURS AGO JUST
EAST OF LYH. MAIN BODY OF RAINFALL THEN IS FORCED EAST FINALLY
THIS EVENING AS RIPPLES OF LOW PRESSURE DART INTO PA/NY/NJ. AS
WINDS VEER SHARPLY THIS EVENING...DOWNSLOPING MAY CREATE THE
TYPICAL RAIN SHADOW WITH MUCH LESS PRECIP THROUGH THE ROANOKE AND
NEW RIVER VALLEYS AS RAIN REDEVELOPS THROUGH THE PIEDMONT AND
SOUTHSIDE LATE TONIGHT. AGAIN LLVL NATURE OF THE ARCTIC AIRMASS
MAKES P TYPE QUITE TRICKY ACROSS THE HIGHEST PARTS OF SE WEST VA
LATE TONIGHT. THE SAVING GRACE IS THAT MOST OF THE PRECIP WILL BE
GONE. WITH MOISTURE/QPF DWINDLING QUICKLY BEHIND THE
FRONT...WOULDN`T EXPECT MUCH...ALTHOUGH THERE COULD BE A LIGHT MIX
OF FIRST FREEZING RAIN...THEN SLEET AND POSSIBLY SNOW JUST AFTER
SUNRISE SATURDAY ABOVE 3000 FEET ACROSS SE WEST VA. GENERALLY HAVE
MINOR AMOUNTS OF ICE/SLEET/SNOW BUT IT IS IMPORTANT TO POINT OUT
THAT THIS WILL NOT BE THE TYPICAL SMOOTH TRANSITION FROM RAIN TO
SNOW AS THE PRECIP CUTS OFF IN SE WEST VA.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
-- Changed Discussion --
AS OF 315 PM EST THURSDAY...

NOT A LOT OF CHANGE EARLY ON WITH THE SLOW MOVING COLD FRONT AND
ASSOCIATED WAVE CROSSING THE REGION FROM THE NW FRIDAY NIGHT AND
SPILLING SOUTH OF THE AREA EARLY SATURDAY. MODELS AGAIN WEAKEN THE
AXIS OF LIFT ALONG/BEHIND THE FRONT FRIDAY EVENING WITH HEAVIEST QPF
AND HIGHEST POPS ALONG THE WESTERN SLOPES THROUGH LATE
EVENING...THEN LESS ALONG/EAST OF THE BLUE RIDGE EXCEPT SE WHERE THE
BOUNDARY MAY STALL AND THE LOW LEVEL NE FLOW MAY ENHANCE SHOWERS
LATE. STILL APPEARS ENOUGH MOISTURE ACROSS THE NW LATE FRIDAY NIGHT
TO WARRANT KEEPING IN SOME LIGHT MIX MENTION AT ELEVATION BUT
OVERALL THINK ANYTHING FROZEN AT THIS POINT QUITE SPOTTY ACROSS SE
WVA. COLD AIR WILL BE SLIDING IN FROM THE NORTH/WEST ALTHOUGH TEMPS
MAY ACTUALLY GET COLDER AFTER DAYBREAK SATURDAY WHEN THE BETTER 85H
COLD ADVECTION ARRIVES.

GUIDANCE HAS CONTINUED THE TREND FROM YESTERDAY IN PUSHING THE
DEEPER MOISTURE TO THE SE SATURDAY AS THE LARGE ARCTIC HIGH BUILDS
IN FROM THE NW AND INITIALLY GIVES THE MOISTURE A PUSH. MAY SEE THE
ENTIRE CWA GO DRY BY SATURDAY AFTERNOON BUT FOR NOW LEAVING IN SOME
POP MAINLY EASTERN HALF THROUGH MIDDAY AND MAINLY FAR SE LATE IN THE
DAY. COULD EVEN HAVE SOME CLEARING TAKE PLACE NW PENDING HOW STRONG
THE DRY ADVECTION IS SO CUT BACK ON CLOUD COVER SOME NORTH HALF
DURING THE AFTERNOON. HIGHS CHILLY WITH LOW LEVEL NORTH/NW FLOW WITH
TEMPS 30S WEST TO 40S/NEAR 50 FAR SOUTH.

MAIN CONCERN THEN WITH THE POTENTIAL FOR A SIGNIFICANT WINTER EVENT
FROM VERY LATE SAT NIGHT INTO SUNDAY AND PERHAPS SUNDAY NIGHT ACROSS
THE NORTH. LATEST GUIDANCE HAS AGAIN SLOWED THINGS UP A BIT WITH
LOTS OF COLD/DRY AIR SLIDING DOWN EAST OF THE BLUE RIDGE AS THE
STRONG WEDGE DEVELOPS WITH THE HIGH BUILDING FARTHER SOUTH. THIS
WILL MAKE FOR COLDER TEMPS SAT NIGHT BEFORE THICKENING CLOUDS AND
LIGHT PRECIP RETURN FROM THE SOUTH/SW AFTER MIDNIGHT PER ISENTROPIC
LIFT AHEAD OF ANOTHER WAVE HEADING UP WEST OF THE MOUNTAINS.

LATEST FORECAST SOUNDINGS SHOW DRY AIR HOLDING LONGER WITH PRECIP
NOT REACHING INTO THE SOUTHERN HALF OF THE AREA UNTIL AFTER MIDNIGHT
AND POINTS NORTH SUNDAY AROUND DAYBREAK. PRECIP THEN LOOKS TO
ACCELERATE INTO THE WEDGE SUNDAY MORNING FROM THE SW BUT REMAIN
INCONSISTENT IN QPF AMOUNTS WHICH ARE CRITICAL GIVEN COLDER PROFILES
FROM 12Z RUNS. HOWEVER MOST SHOWING THE BEST LIFT WITH A WARM
FRONT ALOFT TYPE FEATURE THAT DEVELOPS OVER THE CENTRAL/NORTHERN
CWA SUNDAY MORNING AND SHIFTS NORTH DURING THE AFTERNOON LEAVING
MORE SPOTTY NATURE PRECIP ELSW INTO SUNDAY EVENING. BOTH THE NAM
AND GFS ARE COLDER THAN THE EARLIER SOLNS WITH LESS OF A WARM NOSE
EARLY ON AND DEEPER LOW LEVEL COLD AIR SUPPORTIVE OF MORE OF A
SNOW/SLEET MIX AT THE ONSET ESPCLY HIGHWAY 460 NORTH. THUS
INCLUDING SOME LIGHT ACCUMULATIONS NW SUNDAY MORNING AS THINGS
REMAIN BELOW FREEZING AT 85H AND THINGS BECOME MORE ISOTHERMAL
UNTIL THE STRONGER WARM ADVECTION ARRIVES IN THE AFTERNOON. SOME
SLEET ALSO POSSIBLE ELSW AS THINGS WET BULB DOWN AT THE ONSET BUT
THINKING MORE OF A PROLONGED FREEZING RAIN EVENT ESPCLY SRN BLUE
RIDGE AND ACROSS THE VA COUNTIES SOUTH OF 460. WEDGE MAY BE ENOUGH
TO FORCE TEMPS DOWN ENOUGH TO PRODUCE SOME SPOTTY FZRA INTO NW NC
BUT HOLDING OFF GOING THAT COLD ATTM. OTRW FEW CHANGES TO HIGH
POPS SUNDAY WITH HIGH POPS FOR LOW QPF SUNDAY NIGHT WHEN THE
GREENBRIER VALLEY AND SRN SHENANDOAH VALLEY MAY HOLD ONTO FREEZING
RAIN OVERNIGHT. SINCE MOSTLY A 6TH PERIOD AND BEYOND EVENT...WILL
HOLD OFF ON HEADLINES FOR NOW AND KEEP MENTION IN THE HWO.
-- End Changed Discussion --

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
AS OF 350 PM EST THURSDAY...

COMPLICATED FORECAST CONTINUES THROUGH THE EXTENDED PERIODS AS
SOUTHWEST FLOW ALOFT CONTINUES ACROSS THE REGION AT THE SAME TIME
ARCTIC AIR CONTINUES TO STREAM SOUTHEASTWARD FROM WESTERN/CENTRAL
CANADA INTO THE CENTRAL AND EASTERN U.S. OUR REGION REMAINS ON OR
NEAR THE BOUNDARY BETWEEN THE ARCTIC AIR AND THE WARMER AIR TO THE
SOUTHEAST...HOWEVER...THROUGH THE LONGER TERM PERIODS IT APPEARS
THAT THE ARCTIC AIR WILL WIN OUT ACROSS OUR REGION AND THE FRONTAL
WILL FINALLY BE PUSHED INTO THE SE STATES AS THE UPPER FLOW
FINALLY BECOMES NW.

MON MORNING WE ARE STILL DEALING WITH THE END OF THE POTENTIAL
SIGNIFICANT ICING EVENT ADDRESSED IN THE SHORT TERM PERIODS AS THE
WEDGE BOUNDARY FINALLY LIFTS INTO NORTHERN VA. MODELS HAVE
CONTINUED TO TREND COLDER...WHICH REQUIRES HOLDING ONTO THE -FZRA
A FEW MORE HOURS INTO MID-MORNING MONDAY THAN EARLIER INDICATED.
WILL CHANGE ALL PRECIPITATION TO -RA BY 15Z MON AS THE FORECAST
AREA BRIEFLY MOVES INTO A WARM SECTOR SANDWICHED BETWEEN THE
RETREATING COLD AIR WEDGE AND THE NEXT SURGE OF ARCTIC AIR TO THE
WEST. THROUGH THE DAYLIGHT HOURS...WE SHOULD SEE ONLY LIQUID PCPN
ACROSS THE REGION.

BY 06Z TUE...THE NEXT SURGE OF ARCTIC AIR SHOULD MOVE INTO OUR WV
COUNTIES AND OUR FAR SW VA CONTINUES. GIVEN THE STRENGTH OF THIS
SECOND SURGE OF COLD AIR...WOULD EXPECT -RA TO QUICKLY CHANGE TO
-SN FROM WEST TO EAST DURING THE EVENING. AT THE SAME TIME...THE
DEEPER MOISTURE IS SHIFTING EAST INTO THE PIEDMONT WHERE AT THIS
POINT IT SHOULD STILL BE WARM ENOUGH FOR MOSTLY -RA. THUS...SNOW
ACCUMULATIONS OUTSIDE MOUNTAIN UPSLOPE -SHSN EASTERN WV...SHOULD
BE MINIMAL...BUT COULD NOT RULE OUT AN INCH OR SO IN SOME SPOTS
WEST OF I-81/I-77. THERE IS CONSIDERABLE DISCREPANCY BETWEEN THE
GFS/ECMWF IN THIS TIME FRAME...WITH THE ECMWF PUSHING THE MOISTURE
WELL EAST OF THE CWA BEFORE ANY APPRECIABLE COLD AIR MOVES INTO
THE REGION FROM THE WEST...WHILE THE GFS TRIES TO MOVE YET A THIRD
WAVE ALONG THE FRONTAL BOUNDARY ACROSS THE REGION FROM THE SW.
GIVEN THE OVERALL CONFLUENT FLOW IN THIS TIME FRAME...NOT
EXPECTING ANY SIGNIFICANT PCPN OR MORE IMPORTANTLY WINTER WX
ISSUES. AGAIN...HOWEVER...THERE WILL BE MOUNTAIN UPSLOPE
-SHSN...WITH MINOR SNOW ACCUMULATIONS EASTERN WV COUNTIES INTO FAR
SW VA AND THE NW NC MOUNTAINS.

FOR THE REMAINDER OF THE EXTENDED...AT THIS POINT IT APPEARS DRY.
THE CENTER OF THE ARCTIC AIR MASS DRIFTS OVER THE REGION BY THU
WITH A VERY DRY/COLD AIR MASS. AGAIN...THERE ARE CONSIDERABLE
DIFFERENCES BETWEEN THE ECMWF AND GFS WITH RESPECT TO TEMPERATURES
IN THIS TIME FRAME. GIVEN THE STRENGTH OF THIS ARCTIC AIR
MASS...HAVE LEANED HEAVILY TOWARD THE COLDER GFS. THE COLDEST DAY
SHOULD BE THU WHEN THE ARCTIC HIGH IS CENTERED RIGHT OVER THE CWA.
WOULD NOT BE THE LEAST SURPRISED TO SEE MIN TEMPERATURES IN THE
SINGLE DIGITS IN LOCATIONS SUCH AS LWB. HOWEVER...THE PREVAILING
WEST AS OPPOSED TO A STRONG NW-N FLOW ALOFT SHOULD RESULT IN THE
COLDER AIR REMAINING NORTH AND WEST OF THE CWA..SO WE SHOULD STAY
AOA 20 DEGREES FOR MINS ACROSS THE PIEDMONT. ANY PRECIPITATION
WED-FRI SHOULD BE CONFINED TO UPSLOPE MOUNTAIN -SHSN WITH DRIER
DOWNSLOPE WEST FLOW EAST OF THE ALLEGHANYS. EVEN ACROSS EASTERN
WV...SNOW ACCUMULATIONS SHOULD BE FAIRLY LIMITED WITH OVERALL
SNOW ACCUMULATIONS THERE EVEN AN INCH OR LESS.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
AS OF 1145 PM EST THURSDAY...

STRONG COLD FRONT WILL BE APPROACHING FROM THE OHIO VALLEY...STALLING
WEST OF THE APPALACHIAN MOUNTAINS TONIGHT. A BROAD BAND OF RAIN
FROM CENTRAL PENNSYLVANIA TO CENTRAL TENNESSEE WILL BRING RAIN
WITH MVFR VISIBILITIES TO KLWB AND KBLF TONIGHT. STRATUS AND FOG
WITH SCATTERED SHOWERS IS EXPECTED FOR THE REST OF THE AREA.
CEILINGS WERE ALREADY MVFR AT 00Z/7PM. HIGH CONFIDENCE THAT
KROA...KBCB...KLYH AND KDAN WILL LOWER TO IFR OR LIFR OVERNIGHT WITH
MVFR FOG. LITTLE IMPROVEMENT IS EXPECTED ON FRIDAY. CEILINGS WILL
REMAIN IN THE IFR TO MVFR RANGE WITH RAIN BECOMING MORE
WIDESPREAD...ESPECIALLY IN THE LATE AFTERNOON AND EVENING.

EXTENDED AVIATION...A COLD FRONT WILL MAKE SLOW PROGRESS ACROSS
THE AREA LATE FRIDAY...RESULTING IN MVFR AND IFR CONDITIONS IN
ADDITION TO WIDESPREAD RAIN SHOWERS...BEFORE THE FRONT PASSES EAST
FRIDAY NIGHT INTO SATURDAY MORNING. MAY SEE A BRIEF IMPROVEMENT TO
VFR ON SATURDAY AS HIGH PRESSURE BUILDS IN FROM THE
NORTH...HOWEVER IFR WILL RETURN SATURDAY NIGHT AS ANOTHER SYSTEM
APPROACHES FROM THE SOUTHWEST...BRINGING FREEZING RAIN...SNOW AND
SLEET TO THE AREA SUNDAY. AN ARCTIC COLD FRONT WILL MOVE THROUGH
ON MONDAY...BRINGING A SLOW IMPROVEMENT TO VFR FOR TUESDAY.

HIGH PRESSURE IS EXPECTED TO PROVIDE FAIR WEATHER WITH VFR
CONDITIONS FROM TUESDAY THROUGH THURSDAY.

&&

.CLIMATE...
WARM TEMPERATURES THE NEXT COUPLE DAYS WILL APPROACH RECORDS AT THE
CLIMATE SITES. BELOW ARE THE CURRENT RECORDS.

DECEMBER 5 CURRENT RECORD HIGH TEMPERATURES (YEAR)

ROA76(2001)
LYH76(2001)
DAN 75(1982)
BCB70(2001)
BLF71(2001)
LWB68(2001)

DECEMBER 5 CURRENT RECORD HIGH MINIMUM TEMPERATURES (YEAR)

ROA58(1982)
LYH60(1982)
DAN57(1982)
BCB52(1982)
BLF55(1994)
LWB53(1994)

DECEMBER 6 CURRENT RECORD HIGH MINIMUM TEMPERATURES (YEAR)

ROA52(2011)
LYH52(2011)
DAN60(2011)
BCB51(2011)
BLF56(2011)
LWB 52  (1998)

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

$$
SYNOPSIS...JH/KM
NEAR TERM...KM
SHORT TERM...PM
LONG TERM...RAB
AVIATION...AMS/KK
CLIMATE...CF