-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 061213
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
713 AM EST THU MAR 6 2014

.SYNOPSIS...
ARCTIC HIGH MOVES FROM QUEBEC TO SOUTH OF NOVA SCOTIA THROUGH
FRIDAY WHILE WEDGING SOUTHWEST OVER US. LOW PRESSURE MOVES FROM
THE GULF OF MEXICO...NORTHEAST OFF THE SOUTHEAST COAST THROUGH
FRIDAY WHILE STRENGTHENING. THE LOW HEADS OUT TO SEA FRIDAY NIGHT
WITH WEAK HIGH PRESSURE PUSHING IN FROM THE WEST SATURDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 645 AM EST THURSDAY...

UPDATED GRIDS TO REFLECT LESS CLOUD COVER AS WE HAVE SOME BREAKS
BETWEEN CIRRUS DECKS. APPEARS THE NEXT BATCH OF CIRRUS ALONG WITH
SOME MID CLOUDS ARRIVES BY EARLY AFTERNOON IN THE SOUTHERN CWA.
WITH WEDGE IN PLACE...ONLY MINOR TWEAKS TO TEMPS THROUGH MIDDAY.
NO OTHER MAJOR CHANGES MADE.

PREVIOUS DISCUSSION AT 345 AM...

1040MB ARCTIC HIGH SITUATED OVER SOUTHWEST QUEBEC THIS MORNING
WEDGED AS FAR SOUTH AS ERN GA. THE LOWER CLOUDS THAT WERE EARLIER
FORECAST HAVE NOT TRANSPIRED DUE IN PART TO DRY AIRMASS. GIVEN LACK
OF LOW LVL MOISTURE NEARBY VIA SATELLITE AND OBS DO NOT SEE ANY
THREAT OF LOW CLOUDS OR FREEZING DRIZZLE...AND THEY HAVE BEEN
REMOVED.

THE 00Z MODELS INITIALIZED FAIRLY WELL WITH THE 00Z 12KM NAM THE
BEST IN TERMS OF LOW LVL THERMAL PROFILES. GFS SEEMED OVERDONE ON
QPF AND A DEGREE OR TWO TOO COLD AT 8H.

SO FOR THIS FORECAST...THE MAIN DILEMMA COMES LATE THIS AFTERNOON
INTO FRIDAY MORNING. LOOKING AT LOW PRESSURE OVER THE GULF OF MEXICO
THIS MORNING WHILE UPPER SYSTEM DIGS SOUTHEAST ACROSS THE RED RIVER
VALLEY OF TX/OK. THIS UPPER SYSTEM WILL LIFT THE SFC LOW NORTHEAST
ACROSS NRN FLORIDA THIS AFTERNOON...AND OFF THE SC/NC COAST BY
FRIDAY MORNING. AT THE SAME TIME...THE SFC HIGH CENTER SHIFTS FROM
QUEBEC TO SOUTH OF NOVA SCOTIA. THIS HIGH WILL SLOW THE STORM SYSTEM
DOWN...AND WILL WITH KEEP THE FLOW INTO OUR AREA MORE OUT OF THE
NORTHEAST...WEDGING US IN. MODELS IN FAIRLY GOOD AGREEMENT IN TERMS
OF PRECIP ARRIVING IN THE SOUTHERN FORECAST AREA BY EARLY
EVENING...THEN SHIFTING NORTH ACROSS THE REST OF THE AREA LATE
TONIGHT. ONE ISSUE WILL BE HOW FAR WEST THE PRECIP SHIELD EXTENDS.
THE 00Z ECMWF/NAM/SREF AND HPC EXTEND AT LEAST 0.01" LINE ALL THE
WAY TO THE VA/KY BORDER NORTHEAST INTO SOUTHEAST WV...WHILE THE 00Z
CMC/GFS ARE DRIER. LEANED TOWARD THE BLEND...AND GIVEN THAT THE
UPPER SYSTEM AND SFC LOW ARE MORE WOUND UP...THE PRECIP SHOULD BE
MORE CONCENTRATED. THE NAM HIGHLIGHTS A STRONG LOW LVL JET AT 8H
OVERNIGHT WITH 50+ KNOTS OUT OF THE EAST. THIS WILL EXTEND THE
PRECIP FURTHER WEST. AT THE SAME TIME...THE NAM WITH THE STRONG EAST
FETCH OFF THE ATLANTIC WARMS THE 8H LAYER WELL ABOVE 0C WHILE
KEEPING SFC TEMPS BELOW 32F WHICH SPEAKS TOWARD MORE OF AN ICE
EVENT. MEANWHILE...THE GFS WHICH INITIALIZED COOLER IS SHOWING MORE
OF A SLEET/SNOW TO SOME FZRA/RA. GIVEN THE LACK OF ICE EVENTS IN OUR
CLIMATOLOGY AND HISTORICALLY FOR OUR FORECAST AREA...MEANING OVER
1/4" OF ICE...THE DECISION WAS MADE TO BLEND THE TWO. ALSO...GIVEN
MILLER A SCENARIO...THE THOUGHT OF SUCH A STRONG WARM NOSE SEEMS
OVERDONE...AS WE USUALLY GET THAT MORE FROM MILLER B STORMS.

WITH ALL THAT IN MIND...PER COLLABORATION WITH NEIGHBORING WFOS AND
HPC GUIDANCE...WE WILL SEE A LOW END TYPE ICE/SNOW/SLEET
EVENT...ADVISORY LEVEL FOR THE NC AND SRN VA COUNTIES. CONFIDENCE IS
LOW AS TO IMPACTS AS THE CLOUDS HANG TOUGH...BUT REMAIN OF MOSTLY
MID/HIGH VARIETY...AND WITH MARCH SUNSHINE COULD WARM IT INTO THE
LOWER 40S IN THE NC COUNTIES. HOWEVER...WEDGE IS STRONG AND WENT
BELOW MOS GUIDANCE ON HIGHS...RANGING FROM THE LOWER 40S SOUTHEAST
TO LOWER TO MID 30S NORTH AND ALONG THE BLUE RIDGE.

AS LOWER CLOUDS ARRIVE THIS EVENING WITH PRECIP...THE ISSUE WILL BE
TEMPS VS DEWPOINT SPREAD...AND WETBULB EFFECTS. WE HAVE SEEN CASES
WHERE ONCE PRECIP ARRIVES THAT DEWPOINTS ACTUALLY SHOOT UP MORE THAN
THE TEMPS COMING DOWN. THE IMPACT OF THE CLOUD COVER AND HOW FAR
TEMPS FALL WILL AFFECT ICE ACCRETION ON SFCS.

THIS SYSTEM SHOWS ENOUGH STRENGTH AND OVERALL UVM THAT PRECIP SHOULD
COME DOWN HEAVY ENOUGH TO ALLEVIATE SOME ICE ACCUMULATION...BUT
THREAT FOR ELEVATED SFCS AT LEAST DROPPING BELOW FREEZING IS ENUF TO
WARRANT THE ADVISORY. THE ICE WILL BE MAINLY A CONCERN ALONG AND
EAST OF THE BLUE RIDGE...WITH LESS THAN A .10" EXPECTED...WITH
HIGHEST AMOUNTS ACROSS THE FOOTHILLS OF NC/SRN VA.

IN THE MTNS WE WILL SEE MORE OF A SLEET/SNOW SCENARIO AT THE ONSET
THRU THE NIGHT...AS THE EAST FLOW SHOULD ACT TO COOL THE THERMAL
PROFILE THANKS TO UPSLOPE. LOOKING AT 1-3 INCHES OF SNOW/SLEET.
ALTHOUGH THIS IS BELOW ADVISORY LEVELS WHICH FOR THE MTNS IS 3" IN
12 HOURS...THERE COULD BE JUST ENOUGH SLEET AND ICE TO HAVE MORE OF
AN IMPACT.

WILL TAKE THE ADVISORY AS FAR NORTH AS FLOYD...AND EAST TO CHARLOTTE
COUNTY. PER COORDINATION WITH OTHER OFFICES WILL LET THE DAY SHIFT
REEVALUATE THE NWD EXPANSION OF ADVISORY IF NEEDED. AT THIS
TIME...CONFIDENCE IS HIGH THAT WARNING LEVEL WINTER PRECIP WILL NOT
OCCUR.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
AS OF 430 AM EST WEDNESDAY...

MODELS ARE IN GOOD AGREEMENT WITH WEATHER FEATURES BUT STILL SOME
DIFFERENCES IN THERMAL PROFILES. MODELS HAVE THE UPPER LEVEL LOW
OVER THE SOUTHEASTERN US WHILE THE SURFACE LOW IS OFF THE SOUTHEAST
COAST FRIDAY MORNING. THE UPPER LEVEL LOW DRIFTS OFF THE CAROLINA
COAST BY EARLY EVENING. RAIN WILL END ACROSS THE MOUNTAIN BY LATE
AFTERNOON AND OVER THE PIEDMONT IN THE EVENING.

THE ECM IS THE COLDEST MODEL AND SUPPORTS MOSTLY SNOW INTO EARLY
FRIDAY MORNING FOR THE MAJORITY OF THE FORECAST AREA. THE GFS IS
NEARLY ISOTHERMAL AND WOULD PROMOTE SNOW ACROSS THE BLUE
RIDGE/FOOTHILL COUNTIES AND COUNTIES NORTH OF HIGHWAY 460 INTO THE
EARLY MORNING. THE GFS INTRODUCES A WARM NOSE INTO NORTHWESTERN
NORTH CAROLINA PIEDMONT AND SOUTHSIDE VIRGINIA SHORTLY AFTER SUNRISE
TO CHANGE ANY SNOW OVER TO SLEET AND/OR FREEZING RAIN. THE NAM HAS A
FEW HOURS OF SNOW AT THE ONSET...THEN PUSHES IN A STRONG WARM NOSE
AROUND 3KFT WELL BEFORE SUNRISE. PRECIPITATION WILL THEN CHANGE OVER
TO SLEET...THEN OVER TO FREEZING RAIN AS BOUNDARY LAYERS BECOMES
SHALLOW. THIS STRONG WARM NOSE BY THE NAM IS A BY PRODUCT OF A 70
KTS LOW LEVEL JET. THE GFS DEPICTS A MORE REALISTIC JET OF 40-50
KTS. I PUT MORE WEIGHT INTO THE ECM EARLY FRIDAY MORNING...THEN A
BLEND OF THE GFS/ECM THROUGH THE REST OF THE DAY.

WE WILL SEE THE WEDGE ERODE THROUGH THE DAY FRIDAY. ANY AREAS SEEING
SNOW EARLY IN THE MORNING WILL CHANGE OVER TO SLEET. THIS WILL BE
FOR AREAS ALONG THE BLUE RIDGE AND NORTH OF HIGHWAY 460. BY
NOON...THE WEDGE SHOULD BE GONE WITH THE POSSIBLE EXCEPTION OF THE
SOUTHERN SHENANDOAH VALLEY TO THE HILL CITY OF LYNCHBURG...WHO MAY
CARRY SLEET INTO THE EARLY AFTERNOON. THE REST OF THE AREA WILL HAVE
A COLD RAIN BY EARLY AFTERNOON. AREAS SEEING THE WEDGE ERODING
FIRST...SUCH AS SOUTHSIDE VA AND RICHLANDS/BLUEFIELD AREA MAY SEE
LIGHT FREEZING RAIN CHANGING OVER TO ALL RAIN BY LATE MORNING. ANY
ADDITIONAL ACCUMULATIONS OF SNOW/SLEET OR ICE WILL BE LIGHT FRIDAY
MORNING BUT ENOUGH TO HAVE AN ADVISORY THROUGH NOON.

FOR AREAS OUTSIDE OF THE WEDGE FOR THE MAJORITY OF THIS EVENT...SUCH
AS THE RICHLANDS-BLUEFIELD AREA AND THE MOUNTAIN
EMPIRE...TEMPERATURES FRIDAY WILL WARM INTO THE LOWER 50S. AREAS
HANGING ON TO THE WEDGE THROUGH NOON SHOULD SEE AFTERNOON
TEMPERATURES IN THE MID TO UPPER 40S. THE VIRGINIA PIEDMONT SHOULD
KEEP THE WEDGE UNTIL LATE AFTERNOON AND MAY ONLY SEE HIGHS NEAR 40F.
THERE IS SOME GOOD NEWS WHEN WE HAVE SLEET OR FREEZING RAIN IN THE
FORECAST. YOU KNOW WARM AIR IS ALOFT AND EVENTUALLY IT WILL COME TO
THE SURFACE. SATURDAYS TEMPERATURES WILL WARM INTO THE 50S ACROSS
THE WEST TO LOWER TO MID 60S IN THE EAST. THESE TEMPERATURES ARE 5F-
10F WARMER THAN NORMAL. TEMPERATURES SUNDAY GET KNOCK BACK DOWN TO
SEASONAL LEVELS WITH A WEAK FRONTAL PASSAGE SATURDAY NIGHT INTO
SUNDAY MORNING. TEMPERATURES WILL REMAIN WARM ENOUGH TO KEEP
PRECIPITATION AS RAIN. THE MAJORITY OF THIS RAIN WILL FALL ALONG THE
WESTERN SLOPES. RAIN ADVANCE EAST WILL SHRINK IN COVERAGE AS A WEST
WINDS DEVELOPS FAIRLY QUICKLY AS THE FRONT TRACKS ACROSS THE REGION.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
AS OF 400 PM EST WEDNESDAY...

HIGH PRESSURE WILL BUILD EAST OUT OF KENTUCKY INTO OUR REGION
SUNDAY NIGHT WITH WARM AIR PUSHING NORTH FROM THE TENNESSEE
VALLEY. LOWS WILL DROP TO MID 20S IN THE NORTHWEST MOUNTAINS TO
MID 30S IN THE EAST. HIGH PRESSURE WILL MOVE EAST ACROSS OUR
REGION ON MONDAY. A WEST FLOW WILL ALLOW TEMPERATURES TO MODERATE
ON MONDAY. HIGHS MONDAY WILL WARM INTO THE MID 50S IN THE
MOUNTAINS TO THE MID 60S IN THE PIEDMONT.

LOW PRESSURE CENTER DEVELOPS IN THE GULF MONDAY NIGHT AND TRAVELS
EAST ON TUESDAY. MEANWHILE...A COUPLE OF LOW PRESSURE WAVES ALONG A
FRONTAL BOUNDARY FORM IN THE CENTRAL US. SECOND FRONTAL BOUNDARY
WILL SLIDE EAST TUESDAY INTO WEDNESDAY. LEANED POPS TOWARDS HPCGUIDE
FOLLOWING THE GLOBAL ENSEMBLE MEANS BLEND. UNSETTLED WEATHER
EXPECTED LATE TUESDAY NIGHT INTO WEDNESDAY WITH RAIN BEING THE MAIN
PRECIPITATION TYPE. WENT WITH COOL HIGHS ON WEDNESDAY WITH CLOUD
COVER AND RAIN EXPECTED. HIGHS WEDNESDAY WILL RANGE FROM THE LOWER
40S IN THE MOUNTAINS TO THE LOWER 60S IN THE SOUTHEAST.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
AS OF 655 AM EST THURSDAY...

LOW CLOUD STAYED NORTH OVER MD...AND MAINLY CIRRUS AFFECT THE AREA
THIS MORNING. MODELS KEEPING THE AVIATION FORECAST VFR TODAY WITH
INCREASING NE TO SE WINDS AROUND 10 KNOTS...SOME GUSTS TO 20
KNOTS.

THE THREAT OF WINTRY PRECIP ARRIVES THIS EVENING AND ESPECIALLY
OVERNIGHT. GREATEST THREAT WILL BE IN THE BCB-ROA CORRIDOR AND
POINTS EAST AS THE LOW MOVE NORTHEAST OFF THE SOUTHEAST COAST.

AT THIS TIME...KEPT VSBYS VFR WITH THE PRECIP GIVEN DRIER AIRMASS.
HOWEVER DO HAVE CIGS FALLING TO MVFR AT ALL SITES BY MIDNIGHT.
POTENTIAL FOR IFR AT BLF/DAN LATE. PTYPE OVERALL THROUGH 12Z LOOKS
MAINLY SLEET WITH SOME SNOW MIXED IN...CHANGING TO FZRA AT DAN/BLF
AFTER 08Z.

THE WINTRY PRECIP AND IFR/MVFR CONDITIONS PERSIST INTO FRIDAY
MORNING WITH PTYPE CHANGING TO MOSTLY RAIN BY 18Z. SYSTEM EXITS
OUT TO SEA BY FRIDAY EVENING WITH PRECIP ENDING. SHOULD SEE RETURN
TO VFR AFTER 06Z SAT.

EXTENDED AVIATION DISCUSSION...
VFR CONDITIONS PERSIST INTO SUNDAY...AS HIGH PRESSURE RETURNS.

POTENTIAL FOR SUB-VFR CONDITIONS OVER SOUTHEAST WEST VIRGINIA SUNDAY
NIGHT INTO MONDAY AS A CLIPPER SYSTEM CROSSES THE AREA.
-- End Changed Discussion --

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO NOON EST
     FRIDAY FOR VAZ015>017-032-033-043-044-058-059.
NC...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO NOON EST
     FRIDAY FOR NCZ001>006-018>020.
WV...NONE.

&&

$$
SYNOPSIS...WP
NEAR TERM...WP
SHORT TERM...RCS
LONG TERM...KK
AVIATION...DS/RAB/WP