-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 070506
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1206 AM EST SAT DEC 7 2013

.SYNOPSIS...
A COLD FRONT WILL MOVE SLOWLY SOUTHEAST 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.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 1030 PM EST FRIDAY...

FOR TONIGHT...COLD AIR IS FILTERING IN FROM THE NW AND NE AND HAVE
UPDATED GRIDS TO REFLECTED THE SLOW MOVEMENT OF BOTH FRONT INTO
THE FORECAST AREA. WE MAY SEE SOME FROZEN PRECIPITATION OVERNIGHT
AS THE COLD AIR MOVES IN HOWEVER WE DO NOT ANTICIPATE ANY
SIGNIFICANT ACCUMULATION DUE TO THE WARM GROUND SFC TEMPS WE HAVE
SEEN RECENTLY. MOST OF THE PRECIPITATION WILL TAPER OFF DURING
THE OVERNIGHT WITH BETTER CHANCES IN THE SOUTHEAST. EXPECT
MOISTURE/QPF TO DWINDLE OFF QUICKLY BEHIND THE FRONT.

SURFACE FRONT WILL BE SOUTH OF THE REGION SATURDAY WITH COLD HIGH
PRESSURE BUILDING INTO THE AREA FROM THE NORTHWEST. COLD AIR WILL
CHANNEL DOWN THE EAST SIDE OF THE APPALACHIANS SATURDAY SETTING UP A
DAM OF COLD AIR THAT WILL BE HARD TO DISPLACE SATURDAY NIGHT. DURING
DAYLIGHT HOURS ON SATURDAY...THERE IS THE CHANCE FOR RAIN ACROSS
SOUTHERN PORTIONS OF FORECAST AREA. USED A NON-DIURNAL CURVE FOR
TEMPERATURES TONIGHT AND SATURDAY. LOWS TONIGHT WILL RANGE FROM THE
MID TO UPPER 20S IN THE NORTHWEST TO THE MID 40S IN THE PIEDMONT.
TEMPERATURES WILL FALL FROM SATURDAY MORNING HIGHS IN THE LOWER
30S IN THE MOUNTAINS TO THE UPPER40 TO LOW 50S IN THE
PIEDMONT...TO READINGS IN THE UPPER 20S TO THE AROUND 40 DEGREES
SATURDAY AFTERNOON.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
AS OF 315 PM EST FRIDAY...

MODEL GUIDANCE AMONG THE PREFERRED GFS/ECMWF SOLUTIONS IS STILL
OFFERING A SOLUTION WHERE A WAVE MOVES NORTHEAST THROUGH THE REGION
SATURDAY NIGHT INTO SUNDAY. THIS WAVE IN TURN HELPS LIFT THE
FRONT...THAT SATURDAY NIGHT WILL BE STALLED JUST SOUTH OF THE
REGION...BACK ACROSS OUR AREA. PRECIPITATION IS EXPECTED TO
OVERSPREAD THE AREA AS AS BOTH THE WAVE CROSSES THE REGION AND THE
FRONT RETURNS. INITIALLY...THE LOW LEVEL T/TD PROFILE WILL BE SUCH
THAT MOST OF THE NORTHERN PORTION OF THE REGION WILL RECEIVE A MIX
OF SLEET AND SNOW THROUGH THE NIGHT. FARTHER SOUTH...ENOUGH OF A
WARM NOSE WILL ALREADY BE IN PLACE FOR A RAIN VERSUS FREEZING RAIN
FORECAST WITH THE SURFACE TEMPERATURE BEING THE DETERMINING FACTOR.
THE AMOUNT OF FREEZING RAIN IN THIS PART OF THE AREA WILL INCREASE
IN COVERAGE AS SURFACE TEMPERATURES FALL IN RESPONSE TO THE WET
BULBING EFFECT OF THE PRECIPITATION.

DURING THE DAY SUNDAY...THE STRENGTH OF THE WARM NOSE INCREASES TO
AS MUCH AS +6 TO +7 C ACROSS THE AREA...WHILE MOST OF THE REGION AT
THE SURFACE REMAINS AT OR BELOW FREEZING THANKS TO A STRONG COLD AIR
DAMMING WEDGE THAT WILL ONLY BE REINFORCED BY THE PRECIPITATION.
THIS WILL RESULT IN A TRANSITION FOR THE ENTIRE REGION RECEIVING
ONLY FREEZING RAIN OR RAIN BY THE AFTERNOON...WITH THE FAR NORTHERN
TIER COUNTIES BEING THE LAST TO COMPLETE THE TRANSITION FROM SNOW TO
SLEET TO FREEZING RAIN. THE FAR SOUTHWEST PORTION OF THE AREA MAY
RECEIVE ENOUGH WARM AIR ADVECTION SO THAT OUTSIDE THE INFLUENCE OF
THE WEDGE...A COLD RAIN WILL BECOME MORE PROBABLE AS THE DAY
PROGRESSES. ALSO...THE HIGHER RIDGE TOPS OF THE SOUTHERN ALLEGHANYS
BE HIGH ENOUGH IN ALTITUDE SO AS TO BE MILD ENOUGH TO RECEIVE RAIN
THROUGHOUT THE DAY.

SUNDAY NIGHT...THE WARM AIR ADVECTION ALOFT CONTINUES...THUS
CAUSING ADDITIONAL STRENGTHENING OF THE MAGNITUDE OF THE WARM
NOSE ALOFT. THE FRONTAL BOUNDARY...AND THUS THE BEST REGION OF FOCUS
FOR THE GREATEST PRECIPITATION...SHIFTS FROM BEING ACROSS THE
CENTRAL PORTION OF THE FORECAST AREA...TO JUST INTERSECTING THE
NORTHWEST PORTIONS. AT THE SURFACE...A STRONG WEDGE HOLDS IN PLACE
WITH TEMPERATURES AT OR BELOW FREEZING OVER THE
CENTRAL...NORTHERN...AND NORTHEAST PARTS OF THE FORECAST AREA.
ADDITIONAL FREEZING RAIN IS EXPECTED IN THIS REGION.

AT THIS TIME...NO CHANGES ARE BEING MADE TO THE CURRENT WINTER STORM
WATCH CONFIGURATION AND TIMING. WOULD NOT BE SURPRISED TO SEE ANY
SUBSEQUENT WARNINGS CONTINUE FOR THE NORTHERN PARTS OF THE AREA INTO
MONDAY MORNING. WHILE FORECAST QPF NUMBERS WILL CONTINUE TO
FLUCTUATE...THE LATEST THINKING PLACES 0.25 TO 0.50 INCHES OF ICE
ACROSS THE CENTRAL...NORTHERN...AND NORTHEASTERN PARTS OF THE
REGION...AND SOUTHWEST ALONG THE CREST OF THE BLUE RIDGE INTO THE
NORTHERN MOUNTAINS OF NORTH CAROLINA. OUTSIDE OF THIS REGION...MOST
OTHER LOCATIONS WOULD RECEIVE LESS THAN 0.10 INCHES OF ICE. TRACE
AMOUNTS OR ONLY A FEW HUNDREDTHS ARE EXPECTED OVER THE FAR WESTERN
PORTION OF THE REGION. SNOW/SLEET IS NOT EXPECTED TO BE GREAT IN
TOTAL. MOST OF THIS WOULD OCCUR ACROSS THE NORTHERN HALF OF THE
REGION SATURDAY NIGHT INTO SUNDAY MORNING AND BE IN THE 0.50 TO 1.5
INCH RANGE.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 255 PM EST FRIDAY...

WEDGE SHOULD BE CONTINUING TO WEAKEN BY EARLY MONDAY WITH ONGOING
STRONG 85H WARM ADVECTION SLOWLY CAUSING THE COLD POOL TO FADE WITH
TIME DURING THE DAY AS THE COLD FRONT TO THE WEST APPROACHES. BASED
ON LATEST MODEL SOUNDINGS AND IDEA THAT THE WEDGE WILL BE SLOW TO
EXIT UNTIL A FEW HOURS AFTER SUNRISE...WILL KEEP IN SOME LIGHT
FREEZING RAIN MENTION MAINLY GREENBRIER INTO THE HIGHLANDS EARLY ON.
OTRW RETURNING DEEPER BAND OF MOISTURE SHOULD BE CROSSING THE WEST
THRU MIDDAY MONDAY AND THEN LIKELY WEAKENING ALONG THE BLUE RIDGE BY
EARLY AFTERNOON AS WEAK ENERGY SHEARS BY TO THE NE. HOWEVER AS THE
BOUNDARY SLOWS AGAIN HEADING EAST MAY SEE YET ANOTHER IMPULSE RIDE
UP THRU THE CAROLINAS RESULTING IN ANOTHER ROUND OF RAIN SE LATE.
WILL HAVE BASICALLY ALL LIQUID DURING THE AFTERNOON AS SURFACE TEMPS
WARM ENOUGH TO PUSH MOST INTO THE 40S IF NOT 50S SE.

FRONT PUSHES OUT TO THE BLUE RIDGE MONDAY NIGHT BEFORE SEEING
ANOTHER WAVE ALONG THE BOUNDARY WHICH MAY RESULT IN ANOTHER SWATH OF
PRECIP RIDING UP THE BAROCLINIC ZONE BACK TO THE MOUNTAINS BY EARLY
TUESDAY. HOWEVER WESTWARD EXTENT REMAINS TRICKY ALONG WITH TEMPS AS
MOST GUIDANCE SHOWING VALUES COLD ENOUGH ALOFT FOR SNOW FAR WEST BY
EARLY TUESDAY WITH MOSTLY RAIN ELSW UNTIL THE 85H 0C LINE SWINGS
EAST DURING THE DAY WHEN THE BOUNDARY LAYER MAY BE TOO WARM ESPCLY
EAST. THUS RUNNING WITH MAINLY CHANCE POPS MONDAY NIGHT BUT HIGHER
SE AND THEN A GRADUAL NW TO SE DECREASE IN COVERAGE TUESDAY WITH -SN
NW LATER MONDAY NIGHT/EARLY TUESDAY AND A MIX BLUE RIDGE TO JUST
RAIN EAST FOR NOW. SHOULD FINALLY RETURN TO DRY BUT VERY CHILLY
WEATHER FOR THE REST OF THE WEEK AS STRONG HIGH PRESSURE BUILDS EAST
REACHING THE COAST ON FRIDAY. THIS WILL KEEP TEMPS WELL BELOW NORMAL
WITH MOST HIGHS IN THE 30S FOR MUCH OF THE REST OF THE WEEK.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
AS OF 1200 AM EST SATURDAY...

POOR AVIATION CONDITIONS EXPECTED THROUGH THE FIRST 8-10 HOURS OF
THE TAF...THEN SOME IMPROVEMENTS THROUGH THE REMAINDER OF THE TAF
VALID PERIOD. AN ARCTIC FRONT WAS CREEPING INTO SW VA...BUT MAKING
BETTER PROGRESS AS A BACKDOOR COLD FRONT SOUTHWARD THROUGH THE
PIEDMONT AS ARCTIC HIGH PRESSURE BUILDS EASTWARD NORTH OF 40 DEG
LAT. OVERNIGHT...THE COLD AIR WILL CONTINUE TO FILTER IN FROM THE
WEST AND NORTH AND SHOULD FILTER THROUGH MOST OF THE CWA IN ONE
DIRECTION OR ANOTHER BY DAYBREAK...BUT MOSTLY IT APPEARS FROM THE
NORTH. RAIN...IMMEDIATELY BEHIND THE FRONTAL BOUNDARY...WILL
CONTINUE PROGRESSING THROUGH THE PIEDMONT...AND MOST PCPN AFT 08Z
WILL BE IN THE FORM OF -DZ. TEMPS SHOULD REMAIN ABOVE FREEZING
THROUGH 12Z IN MOST AREAS...SO HAVE REMOVED ANY MENTION OF FROZEN
PCPN WITH THIS TAF SET. EXPECT MOSTLY MVFR-IFR CIGS
OVERNIGHT...WITH LOCALIZED POCKETS OF IFR CIGS...ESPECIALLY AT
BLF. VSBYS MOSTLY MVFR IN -RA AND DZ...WITH ISOLATED POCKETS OF
IFR...POSSIBLY LIFR AT BLF IF CIGS DROP BELOW 004. WINDS...NW-NE
THROUGH THE CWA AT SPEEDS OF 7-10KTS WITH LOW END GUSTS ACROSS THE
PIEDMONT OVERNIGHT AS COLD AIR SURGES DOWN FROM THE NE. AFT 18Z
SAT...EXPECT IMPROVEMENT OF CIGS AT BCB/ROA/DAN AT WORST...WITH
LYH/LWB/BLF POTENTIALLY REMAINING IFR TO LOW END MVFR THROUGH MUCH
OF THE DAY. CLOUDS WILL LOWER AFT 06Z AND WINTER PCPN WILL ALSO BE
AFTER THIS TAF VALID PERIOD.

MEDIUM CONFIDENCE IN CIGS AND VSBYS THROUGH TAF VALID PERIOD.
MEDIUM TO HIGH CONFIDENCE IN WIND SPD/DIR THROUGH TAF VALID
PERIOD.


EXTENDED AVIATION...

AFTER THE BRIEF BREAK IN THE POOR WEATHER ON SATURDAY...WE GET
RIGHT BACK INTO POOR CONDITIONS AS HIGH PRESSURE MOVES IN TO A
WEDGE POSITION AND OVERRUNNING LEADS TO LOW CIGS AND MIXED PCPN
FROM S TO N SATURDAY NIGHT...THEN CONTINUING ON SUNDAY. TEMPS
SHOULD MODERATE ENOUGH TO END THE WINTRY PCPN BY MONDAY...BUT WE
WILL STAY WITH PCPN AND LOW CLOUDS/VSBYS RIGHT INTO TUESDAY. HIGH
PRESSURE FINALLY BUILDS IN LATER ON TUESDAY WITH A RETURN TO VFR
FOR THE MIDDLE OF THE WEEK.
-- End Changed Discussion --

&&

.CLIMATE...
BELOW ARE THE CURRENT RECORDS.


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...WINTER STORM WATCH FROM LATE SATURDAY NIGHT THROUGH LATE
     SUNDAY NIGHT FOR VAZ010>020-022>024-032>035-043>047-058-
     059.
NC...WINTER STORM WATCH FROM LATE SATURDAY NIGHT THROUGH LATE
     SUNDAY NIGHT FOR NCZ001>006-018>020.
WV...WINTER STORM WATCH FROM LATE SATURDAY NIGHT THROUGH LATE
     SUNDAY NIGHT FOR WVZ042>045.

&&

$$
SYNOPSIS...JH/KK/KM
NEAR TERM...JC/KK
SHORT TERM...DS
LONG TERM...JH
AVIATION...MBS/RAB
CLIMATE...CF