Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 090452
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1152 PM EST MON FEB 8 2016

.SYNOPSIS...
A STRONG CYCLONE IN THE UPPER LEVELS OF THE ATMOSPHERE WILL SINK
SOUTH ACROSS THE GREAT LAKES AND INTO THE OHIO VALLEY OVERNIGHT.
THE AREA OF LOW PRESSURE WILL CUTOFF AND REMAIN NEARLY STATIONARY
FOR THE NEXT THREE DAYS. THE COLDEST OF THE AIR WILL NOT ARRIVE
UNTIL TUESDAY. WEAK UPPER LEVEL IMPULSES WILL MOVE ACROSS THE
MOUNTAINS DURING THE WEEK RESULTING IN A PROLONGED SNOW SHOWER
EVENT ESPECIALLY OVER THE MOUNTAINS THROUGH MIDWEEK.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
AS OF 1140 PM EST MONDAY...

HIGH-RES MODELS ESPECIALLY THE RAP13 SEEMS TO HAVE A DECENT HANDLE
ON THE SNOW SHOWERS MOVING ACROSS SW VA/NW NC ATTM. SNOW SQUALL
PARAMETER PER MESOANALYSIS OFF THE RAP INDICATES MOISTURE AND LOW
LVL INSTABILITY TO ENHANCE ANY SNOW THAT MOVES ACROSS SW VA/NW NC
AND SRN WV THROUGH 06Z. SHOULD PICK UP ANOTHER INCH OR SO BETWEEN
MIDNIGHT AND 2AM...THEN A LULL THEN BETTER UPPER VORT MOVES ACROSS
BY 12Z...WHICH SHOULD BRING ANOTHER AREA OF ENHANCED SNOW SHOWERS
TO THE WRN SLOPES. NO CHANGES WERE NEEDED TO THE WINTER WX
HEADLINES. BLOWING SNOW APPEARS TO BECOME AN ISSUE TUESDAY WITH
WINDS PICKING UP BEHIND THE SHORTWAVE.

PREVIOUS MID EVENING DISCUSSION...

TRANSITIONING MORE TOWARD UPSLOPE REGIME AS WE HEAD THROUGH THE
NIGHT. BAND OF HEAVIER SNOW FADING ACROSS ROCKBRIDGE/BATH COUNTY
ATTM. UPSTREAM...SNOW SHOWERS ARE SCATTERED FROM THE KY/VA BORDER
INTO PORTIONS OF NE TN...AND ACROSS THE CUMBERLAND PLATEAU OF TN
NEAR I-75. MODELS FAVOR THE NEXT ROUND REACHING SRN WV INTO FAR
NW NC BETWEEN 10 PM AND 1 AM. THIS WILL BE PUTTING DOWN ANOTHER
INCH OF SNOW...WITH POTENTIALLY HIGHER ON THE RIDGES. MESOANALYSIS
STILL SHOWING SOME FAVORABLE CONDITIONS WITH RESPECT TO HEAVIER
SNOW SHOWERS ACROSS THE NC/TN BORDER...SO WILL HAVE TO MONITOR
CONDITIONS FOR INCREASE IN SNOW AMOUNTS. OTHERWISE...EAST OF THE
MOUNTAINS...THE SKIES SHOULD CLEAR UP SOME BEFORE NW FLOW
INCREASES BRINGING MORE CLOUDS IN LATE.

PREVIOUS DISCUSSION FROM EARL EVENING...

FOCUS IS ON TRANSITION OF RAIN TO SNOW IN THE WEST...BUT OVERALL
RADAR COVERAGE IS MORE SCATTERED THAN CATEGORICAL IN TERMS OF
POPS. WILL FOLLOW CLOSE TO THE 22Z HRRR AND 18Z LOCAL WRF AS IT
SLIDES A NARROW BAND OF SNOW ACROSS THE NEW RIVER VALLEY INTO THE
SHENANDOAH VLY AND BLUE RIDGE NORTH OF CARROLL COUNTY VA THROUGH
EVENING. THERE IS SOME GOOD REFLECTIVITY SIGNATURES AND WITH
COLDER AIR ALOFT WE HAVE HAD SOME THUNDERSNOW REPORTS. SOME AREAS
COULD SEE A GOOD 1-2 INCHES OF SNOW IN A 1 HOUR PERIOD AND AN SPS
WILL COVER THIS THROUGH THE NEXT COUPLE OF HOURS.


ONCE THIS MESOLOW ALONG THE FRONT OVER SW VA MOVES EAST
EXPECT A DRIER PERIOD BUT UPSLOPE KICKS IN.

PREVIOUS DISCUSSION FROM EARLY AFTERNOON...
TODAY`S PRECIPITATION DID NOT START UNTIL LATE IN THE
MORNING...WHICH ALLOWED TEMPERATURES TO PEAK IN THE UPPER 30S TO
LOWERS 40S WEST OF THE BLUE RIDGE TO THE UPPER 40S TO LOWER 50S
EAST. WARM AIR ADVECTION AHEAD OF A COLD FRONT BROUGHT SOME SNOW
TO HIGHER ELEVATIONS AND WHITE RAIN TO THE VALLEYS THIS AFTERNOON.
THIS PRECIPITATION LOWERED TEMPERATURES ACROSS THE MOUNTAINS
DURING THE AFTERNOON BY 5F OR SO. BECAUSE THE WARM BOUNDARY IS SO
SHALLOW...SNOW WAS ABLE TO MAKE IT TO THE GROUND EVEN...THOUGH
TEMPERATURES WERE ABOVE FREEZING.

THE FIRST COLD FRONT...LOCATED ACROSS THE OHIO AND TENNESSEE
VALLEYS...WILL MOVE ACROSS THE MOUNTAINS EARLY THIS EVENING...THEN
ACROSS THE PIEDMONT BY MIDNIGHT. THIS FRONT MAY BE A FEW HOURS
SLOWER TO CLEAR THE AREA...AS A SURFACE REFLECTION DEVELOPS ALONG
THE FRONT TRACKING ACROSS THE PIEDMONT THIS EVENING. PRECIPITATION
WITH THE FRONT WILL REMAIN LIGHT WITH SNOW OR WHITE RAIN ACROSS
THE MOUNTAINS AND A COLD RAIN IN THE EAST. A SECOND COLD FRONT
WITH ARCTIC AIR WILL APPROACH THE AREA EARLY TUESDAY MORNING.
PRECIPITATION AHEAD AND BEHIND THIS FRONT WILL BE ALL SNOW WITH
ACCUMULATIONS PRIMARILY ALONG WESTERN SLOPES. WESTERN SLOPES OF
GREENBRIER AND SUMMERS COUNTY COULD SEE 2-3 INCHES THIS AFTERNOON
INTO TONIGHT. WESTERN SLOPES FROM THE BLUEFIELD-RICHLANDS AREA TO
THE GRAYSON HIGHLANDS AND NORTHWEST NORTH CAROLINA HIGH COUNTY
COULD HAVE 1-2 INCHES...POSSIBLE 3-4 INCHES ABOVE 4000 FT.

FOR HEADLINES...WE WILL CONTINUE THE WINTER WEATHER ADVISORY FOR
THE FIRST FRONT THROUGH 6PM THIS EVENING FOR OUR WESTERN COUNTIES.
WE WILL ALLOW THIS ADVISORY TO EXPIRE. WE WILL THEN UPGRADE THE
CURRENT WINTER STORM WATCH TO A WINTER STORM WARNING FOR WESTERN
SLOPES OF GREENBRIER COUNTY SOUTH INTO SUMMERS AND MERCER COUNTY.
OTHER COUNTIES IN THE WATCH WILL BE CHANGED TO A WINTER WEATHER
ADVISORY FROM THE ALLEGHANY HIGHLANDS TO THE MOUNTAIN EMPIRE AND
NORTHWEST NORTH CAROLINA HIGH COUNTY. AT THIS TIME...NO OTHER
COUNTIES WILL HAVE HEADLINES TO INCLUDED THE NEW RIVER AND ROANOKE
VALLEYS...WHO MAY SEE SOME SNOW TONIGHT INTO TUESDAY WITH ONLY
LIGHT ACCUMULATIONS.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 330 PM EST MONDAY...

DEEP UPPER LOW OVER THE OHIO VALLEY TUESDAY AND WEDNESDAY. SHORT
WAVE OVER THE FORECAST AREA TUESDAY MORNING ALONG WITH MUCH COLDER
TEMPERATURES ALOFT...IN THE RANGE OF -30 TO -36 WILL PROVIDE SOME
LIFT AND RELATIVE INSTABILITY. THIS SHOULD EXTEND SNOW SHOWERS
WELL EAST OF THE BLUE RIDGE ON TUESDAY...ESPECIALLY NORTH OF
ROANOKE. 850 MB TEMPERATURES WILL CONTINUE TO DROP...REACHING -18
TO -20 BY 12Z/7AM THURSDAY. MODELS ARE SIMILAR IN OVERALL SYNOPTIC
PATTERN BUT SUBTLE DIFFERENCES SHOW UP IN SPEED AND LOCATION OF
SHORT WAVED EMBEDDED IN THE LARGE UPPER TROF.

ENOUGH COLD AIR COMING IN THAT WESTERN SLOPE LOCATIONS AND AREAS
WITH SNOW SHOWERS WILL HAVE STEADY OR EVEN SLIGHTLY FALLING
TEMPERATURES DURING THE DAY WEDNESDAY. EXPECTING SNOW TO LIQUID
RATIOS OF 25:1 BY WEDNESDAY NIGHT. ENOUGH DRY AIR AND DOWNSLOPING
ON WEDNESDAY AND THURSDAY TO HAVE SOME CLEARING EAST OF THE BLUE
RIDGE.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 250 PM EST MONDAY...

EASTERN UPPER TROF GETS RE-ENFORCED FRIDAY NIGHT AND
SATURDAY...THEN TROF AXIS MOVES OF THE COAST ON SUNDAY. BOTH THE
ECMWF AND GFS BRING A CLIPPER ACROSS THE CENTRAL UNITED STATES
MONDAY THEN INTO THE MID ATLANTIC REGION BY TUESDAY. WPC SUGGESTED
THE TRACK OFF THE ECMWF MAY BE TOO FAR SOUTH.

SOME 850 MB WARM AIR ADVECTION AND LOW LEVEL CONVERGENCE ALONG
THE LEADING EDGE OF THE NEXT SURGE OF ARCTIC AIR. BEST LIFT LOOKS
TO BE ON FRIDAY WITH SOME UPPER DIFFLUENCE. SNOW SHOULD BE MORE
WIDESPREAD THAN JUST UPSLOPE. THEN GUSTY WINDS AND VERY LOW WIND
CHILL VALUES ON FRIDAY NIGHT THROUGH SATURDAY NIGHT WITH NORTHWEST
850 MB WINDS APPROACHING 50 KNOTS. WIND CHILLS WILL AGAIN BE IN
ADVISORY CRITERIA...BETWEEN -5 TO -19 IN THE MOUNTAINS ON SATURDAY
NIGHT.

A ROUGHLY 1045 MB SURFACE HIGH WILL BUILD INTO THE AREA FRIDAY
NIGHT AND SATURDAY. THIS FEATURE WILL BE CENTERED OVER THE MID
ATLANTIC REGION MONDAY MORNING. WINDS WILL DIMINISH ENOUGH WITH
THE APPROACH OF THIS HIGH...AND WITH THE ASSOCIATED DRY AIR...TO
END UPSLOPE SNOW SHOWERS IN THE MOUNTAINS SUNDAY.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AS OF 1145 PM EST MONDAY...

WILL SEE A PERIOD OF SNOW SHOWERS AFFECT MAINLY BLF AND SOME AT
BCB/LWB EARLY WITH IFR/MVFR VSBYS/CIGS. FURTHER EAST CLEARING
SKIES AND LIGHT WINDS ALLOWED FOR FOG FORMATION AT LYH/DAN THANKS
TO EARLIER RAINFALL. EXPECT THE FOG STAYING AROUND THROUGH 09Z
THEN SOME IMPROVEMENT FROM LIFR/IFR TO MVFR. AS WINDS PICK UP AS
THE SHORTWAVE MOVES ACROSS AFTER 12Z LOOK FOR VFR VSBYS. OVERALL
CIGS FROM ROA EAST SHOULD STAY VFR...POTENTIALLY TOUCH HIGH END
MVFR IF A FLURRY OR LIGHT SNOW SHOWER PASSES BUT SEEMS THAT THE
TIME PERIOD FOR THIS IS SMALL AND NOT ENOUGH TO WARRANT MENTION IN
THE TAF.

A DECENT UPPER DISTURBANCE IS GOING TO MOVE OVER SRN WV/SW VA
10-14Z...WHICH WILL BRING AN AREA OF HEAVIER SNOW SHOWERS TOWARD
BLF/LWB. THIS WILL BRING CIGS/VSBYS BACK TOWARD IFR MAINLY BLF.

ONCE THIS WAVE MOVES BY WINDS WILL BE PICKING UP BUT SNOW
SHOWERS/FLURRIES WILL PERSIST THROUGH THE REST OF THE PERIOD FROM
BCB TO BLF/LWB...WITH MAINLY MVFR CIGS BLF/LWB AND LOW END VFR AT
BCB.

EXTENDED DISCUSSION...

SUB-VFR SHOULD BECOME MORE CONFINED TO THE MOUNTAINS AND WESTERN
SLOPES TUESDAY NIGHT INTO MIDWEEK WITH PROLONGED MVFR/IFR
CONDITIONS AT KBLF/KLWB IN SNOW SHOWERS THROUGH AT LEAST WEDNESDAY
NIGHT AS ARCTIC AIR ARRIVES. POTENTIAL ALSO FOR PERIODS OF MVFR AT
KBCB/KROA AS IMPULSES ROTATE ACROSS THE MOUNTAINS AND BANDS OF
SNOW DEVELOP DURING THE OVERNIGHT HOURS. ACCUMULATING SNOW IS
LIKELY IN THE MOUNTAINS WEST OF THE BLUE RIDGE. FLURRIES MAY ALSO
OCCUR AS FAR EAST AS THE PIEDMONT WHERE INTERVALS OF VFR TO MVFR
CIGS COULD ALSO OCCUR.

CONDITIONS SHOULD BRIEFLY RETURN TO MAINLY VFR THURSDAY/THURSDAY
NIGHT AS WEAK HIGH PRESSURE BUILDS IN AND MOISTURE DECREASES.

ANOTHER SYSTEM MOVING ACROSS THE SOUTH MAY BRING SUB VFR
CONDITIONS WITH WINTRY PRECIP FRIDAY INTO FRIDAY NIGHT. ANOTHER
ARCTIC FRONT CROSSES BY SAT MORNING WITH GUSTY WINDS AND UPSLOPE
SNOW SHOWERS WITH SUB VFR IN THE MTNS.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR VAZ007-
     009>012-015-019-020.
NC...WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR NCZ001-018.
WV...WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR WVZ042>044-
     507.
     WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR WVZ043-508.

&&

$$
SYNOPSIS...RCS
NEAR TERM...RCS/WP
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...RCS/WP


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