Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 050434
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1134 PM EST WED MAR 4 2015

.SYNOPSIS...
A COLD FRONT WILL MOVE EAST ACROSS THE REGION OVERNIGHT...BEFORE
HEADING OFFSHORE LATE THURSDAY. COLD AIR FILTERING IN BEHIND THE
FRONT WILL CAUSE WIDESPREAD RAIN ACROSS THE AREA TO CHANGE TO A
WINTRY MIX OVER THE MOUNTAINS TONIGHT AND ELSEWHERE ON THURSDAY. HIGH
PRESSURE OVER THE MISSISSIPPI VALLEY WILL MOVE INTO THE AREA FOR
FRIDAY THROUGH SUNDAY.
&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 815 PM EST WEDNESDAY...

AXIS OF LIGHT TO MODERATE RAIN HAS FINALLY SHIFTED EAST ACROSS THE
NW COUNTIES THIS EVENING AHEAD OF ANOTHER WEAK WAVE ALONG THE
FRONT OVER NE TN. SURFACE COLD FRONT NEAR THE WESTERN SLOPES WILL
CONTINUE TO ONLY DRIFT SLOWLY EAST OVERNIGHT GIVEN THIS IMPULSE
ALONG THE BOUNDARY SO SWITCH TO ANY FROZEN OR FREEZING PRECIP MAY
BE DELAYED UNTIL AFTER MIDNIGHT FAR NW...AND AROUND DAWN OR LATER
INTO THE NEW RIVER VALLEY PER LATEST SHORT TERM GUIDANCE. THUS
SLOWED UP THE CHANGEOVER A BIT OVERNIGHT WHILE KEEPING CAT POPS
NORTH/WEST EARLY THEN ACROSS MUCH OF THE CWA BEFORE DAWN AS THE
AXIS OF DEEPER MOISTURE FINALLY FOLDS SOUTHEAST. TOYED WITH
EXTENDING THE WARNING SOUTH INTO CRAIG COUNTY FOR THURSDAY BUT
GIVEN DECREASE IN PROJECTED SNOW OFF MODELS AND MORE SLEET NATURE
TO FORECAST SOUNDINGS PER LARGE WARM NOSE ALOFT WILL HOLD OFF FOR
NOW. BUMPED UP LOWS SOME IN THE EAST AND NEAR THE BLUE RIDGE GIVEN
LAGGING COLD ADVECTION OUT EAST WHERE TEMPS COULD STILL BE CLOSE
TO 50 AT SUNRISE BEFORE FALLING. SHOULD FINALLY SEE THE FAR WEST
DROP BELOW FREEZING AROUND DAWN WHILE SPOTS CLOSE TO THE BLUE
RIDGE SEE THEIR COLDER TEMPS AN HOUR OR SO EITHER SIDE OF 12Z.

PREVIOUS DISCUSSION AS OF 311 PM EST WEDNESDAY...

EROSION OF THE COLD AIR AND SOME SUNSHINE HAS ALLOWED TEMPERATURES
TO CLIMB INTO THE MID 60S TO LOWER 70S ACROSS SOUTHERN LOCATIONS OF
FORECAST AREA THIS AFTERNOON. FRONTAL BOUNDARY REMAINS TO OUR
WEST AS SEVERAL WAVES OF LOW PRESSURE SLOWING PROGRESS EAST THIS
AFTERNOON. ONCE THE AREA OF LOW PRESSURE PUSHES NORTHEAST...COLD
FRONT WILL TRAVEL EAST THIS AFTERNOON INTO TONIGHT.

MODELS ARE IN REASONABLE AGREEMENT ON TIMING OF COLDER AIR AND
PRECIPITATION ALTHOUGH SOME FLUCTUATIONS ON QPF. MODEL BLEND OF
THE 00Z ECMWF/12Z GFS AND PREVIOUS FORECAST WAS USED. NOT BUYING
INTO THE AMOUNT OF SNOW THE NAM IS SHOWING...THOUGH THIS SETUP IS
VERY TRICKY AS WE USUALLY DO NOT GET HEAVY SNOW POST FRONTAL. THE
NAM HAS A BETTER HISTORY THIS WINTER...THOUGH WETTER THAN THE
OTHER MODELS.

NONETHELESS THE BLEND OF THE GFS/ECMWF FAVOR EXPANDING THE WARNING
SOUTHWEST AND EAST TO INCLUDE THE REST OF SE WV...AS WELL AS NORTH
OF THE JAMES RIVER IN AMHERST TO SOUTH OF RIVER IN BUCKINGHAM. GIVEN
THE IMPACT OF SLEET IN CUTTING SNOW TOTALS...USED AN INCH LESS THAN
WHAT WE NORMALLY USE FOR SNOW AMOUNTS FOR THE HEADLINES. STILL LOOKS
LIKE THE SETUP FAVORS 4-8 INCHES OF SNOW ACROSS THE MOUNTAINS OF SE
WV INTO THE ALLEGHANY HIGHLANDS...AND WOULD NOT BE SURPRISED FOR
DOUBLE DIGITS IN THE NW CORNER OF GREENBRIER COUNTY AND THE HIGHEST
RIDGES OF BATH COUNTY. AS YOU HEAD SOUTHWARD...AMOUNTS WILL BE MORE
LIMITED...BUT ENOUGH FOR ADVISORY. ONLY THE NC PIEDMONT AND
FOOTHILLS WILL STAY UNDER AN INCH FOR SNOW/SLEET. THE COLDER WILL BE
ARRIVING BY THU AFTERNOON IN THE SOUTHEAST WHICH SHOULD LIMIT
ACCUMULATIONS SOMEWHAT.

THE PTYPE WILL BE RAIN THIS EVENING...THEN LOOK FOR SLEET MOVING
INTO THE MOUNTAINS OF WV/FAR SW VA BY LATE EVENING...REACHING THE I-
81 CORRIDOR TOWARD DAWN AND EAST OF THE BLUE RIDGE BY MIDDAY/EARLY
AFTERNOON. THE SNOW WILL REACH THE WV MTNS BY DAWN...THE NEW RIVER
VALLEY/ROANOKE AREA BY LATE MORNING AND THE PIEDMONT THROUGH THE
AFTERNOON.

THE BIG QUESTION WILL BE HOW FAR SOUTHEAST THE FRONT MOVES AND HOW
QUICK THE COLD AIR PUSHES IN WITH HOW MUCH MOISTURE REMAINS.

THIS SCENARIO FAVORS A SMALLER TRANSITION ZONE...SO FREEZING RAIN
WILL BE LIMITED FOR AN HOUR OR TWO AT MOST IN THE MOUNTAINS AND
PORTIONS OF THE NEW RIVER VALLEY LATE TONIGHT/THURSDAY MORNING.
TEMPERATURES TONIGHT WILL BE TRICKY BEHIND THE FRONT BUT THINK BY
MORNING THE COLDER AIR WILL BE IN THE MOUNTAINS WITH 20S TO NEAR
30...WITH LOWER 40S SOUTHSIDE. TEMPERATURES DURING THURSDAY WILL
CONTINUE TO FALL.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 305 PM TUESDAY...

ON THURSDAY NIGHT...THE MOISTURE EXITS QUICKLY BUT COULD SEE
LINGERING SNOW ACROSS THE PIEDMONT UNTIL 9 PM. HIGH PRESSURE WORKS
IN BY LATE THURSDAY NIGHT...THOUGH COULD SEE JUST ENOUGH WIND FOR
WIND CHILLS TO ZERO OR JUST BELOW OVER THE SE WV MTNS...INTO THE
ALLEGHANY HIGHLANDS. STRONG RADIATIONAL COOLING WILL PUSH ACTUAL
OVERNIGHT LOW TEMPERATURES TO AROUND ZERO IN SPOTS ACROSS THE
MOUNTAINS...AND TO THE UPPER TEENS/LOW 20S ACROSS THE NORTH
CAROLINA PIEDMONT. THE SAME HIGH PRESSURE SYSTEM WILL REMAIN
ACROSS THE REGION ON FRIDAY...KEEPING TEMPERATURES ON THE CHILLY
SIDE.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 300 PM EST WEDNESDAY...

SATURDAY...HIGH PRESSURE BUILDS OVER THE REGION...WITH ITS CENTER
SHIFTING EAST OF THE AREA BY SATURDAY NIGHT. THE RESULT WILL BE A
DRY FORECAST...WITH MODERATING TEMPERATURES. AFTER HIGHS ON FRIDAY
IN THE UPPER 20S TO MID 30S ACROSS THE FORECAST AREA...HIGHS ON
SATURDAY WILL RANGE MORE IN THE 40S WEST TO LOWER 50S EAST.

THERE HAS BEEN CONSIDERABLE VARIATION IN THE MODEL GUIDANCE DURING
THE SUNDAY THROUGH TUESDAY TIME PERIOD. WHILE EACH IS FAIRLY
CONSISTENT THAT A LONG WAVE TROUGH WILL DEVELOP ACROSS THE EASTERN
THIRD OF CONUS...THERE HAVE BEEN INCONSISTENCIES AS TO WHETHER OR
NOT...AND WHEN...AND WHAT TRACK A SOUTHERN STREAM SYSTEM MAY GET
PICKED UP ON THE EAST SIDE OF THIS TROUGH AND PROGRESS NORTHEAST
ACROSS OUR AREA. THE GFS HAS NOT BEEN FAVORABLE OF THIS OCCURRENCE.
THE ECMWF WAS OPTIMISTIC ON AN ARRIVAL A SOUTHERN SYSTEM ON
MONDAY. OUR FORECAST TODAY WILL REFLECT TEMPERATURES CONTINUING
TO MODERATE THROUGH MONDAY...WITH THE THINKING THAT THE DEVELOPING
TROUGH AXIS WILL REMAIN TO OUR WEST...AND WE WILL CONTINUE IN WARM
AIR ADVECTION AT THE SURFACE. IT WILL ALSO REFLECT THE POTENTIAL
FOR SOME ISOLATED TO SCATTERED UPSLOPE SNOW SHOWERS ACROSS
SOUTHEAST WEST VIRGINIA WHERE 850 MB FLOW WILL BE MORE W-NW. IT
WILL ALSO ALLOW FOR A SLIGHT CHANCE OF A SOUTHERN STREAM SYSTEM
IMPACTING THE AREA ON TUESDAY WITH RAIN OR FREEZING RAIN.

THE LATEST GUIDANCE FOR THE EARLY TO MIDDLE PART OF NEXT WEEK
CONTINUES TO FLUCTUATES IN REGARDS TO THE TIMING AND TRACK OF A
SOUTHERN STREAM SYSTEM. THE LATEST TRENDS BRING THE GFS INTO PLAY
NOW FOR BRINGING A SYSTEM THROUGH THE AREA ON WEDNESDAY...THE
CANADIAN AND ECWMF STILL A LITTLE EARLIER. IN ADDITION TO THE SMALL
CHANCE OF PRECIPITATION ON TUESDAY...WE WILL ALSO ADD WEDNESDAY INTO
THE MIX TO REFLECT THE MODEL VARIATIONS AND A SMALL POTENTIAL EACH
DAY FOR A LOW AND ITS ASSOCIATED PRECIPITATION TO PROGRESS OVER OR
NEAR THE REGION. WHILE MOST OF THE REGION SHOULD EXPERIENCE RAIN ON
WEDNESDAY...A FEW SPOTS IN THE SOUTHEAST WEST VIRGINIA MAY BE COLD
ENOUGH FOR A BRIEF PERIOD OF FREEZING RAIN. HIGH TEMPERATURES ON
WEDNESDAY WILL BE MILDER THAN THOSE OF TUESDAY. EXPECT A RANGE OF
LOW TO MID 50S ACROSS THE MOUNTAINS WITH UPPER 50S TO LOWER 60S
ACROSS THE PIEDMONT.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AS OF 1125 PM EST WEDNESDAY...

FLYING CONDITIONS WILL CONTINUE TO DETERIORATE OVER THE MOUNTAINS
OVERNIGHT AND IN THE EAST BY DAYBREAK THURSDAY. THIS WILL RESULT
IN WIDESPREAD MVFR TO IFR CIGS OVER THE MOUNTAIN LOCATIONS WITH
PERIODIC MVFR VSBYS AND PERHAPS IFR AT TIMES AT KBLF/KLWB. BRIEF
MVFR MAY OCCUR AT KROA AND POINTS EAST OVER THE NEXT FEW HOURS
BEFORE TRENDING TO OVERALL MVFR OVERNIGHT. WINDS WILL SHIFT NW-N
BEHIND THE FRONT. THE PRECIPITATION WILL GRADUALLY TRANSITION FROM
RAIN TO A RAIN/SLEET MIX...TO A SNOW/SLEET MIX TO MAINLY ALL SNOW
BEFORE ENDING OUT EAST THURSDAY AFTERNOON. THIS TRANSITION WILL
START FIRST AROUND 06Z/1AM AROUND KBLF...AND THE LAST LOCATION TO
TRANSITION TO ALL SNOW WILL BE KDAN AROUND 22Z/5PM. BY LATE IN THE
AFTERNOON THURSDAY...CIGS/VSBYS WILL START TO IMPROVE IN THE WEST.
A CLEARING TREND IS EXPECTED THURSDAY EVENING...ESPECIALLY IN THE
EAST WITH VFR TO MVFR CIGS LIKELY LINGERING IN THE WEST THURSDAY
EVENING.

MEDIUM CONFIDENCE ON CEILINGS...VISIBILITIES AND WINDS DURING THE
TAF PERIOD.

EXTENDED FORECAST...

FRIDAY TO SUNDAY WILL SEE A RETURN TO HIGH PRESSURE AND VFR
WEATHER. SOME RAIN AND SNOW SHOWERS ARE POSSIBLE ON MONDAY IN THE
WESTERN MOUNTAINS WITH BRIEF MVFR EXPECTED.
&&

.HYDROLOGY...
AS OF 820 PM EST WEDNESDAY

FLOODING HAS BEEN WIDESPREAD ACROSS TAZEWELL AND MERCER COUNTIES
TONIGHT AS RAINFALL OF 0.50 TO 0.75 INCHES FROM EARLIER COMBINED
WITH SNOW MELT FROM THE REMAINS OF THE SNOWPACK TO CAUSE A RAPID
HYDROLOGIC RESPONSE. IN TERMS OF RIVERS THE BLUESTONE AND CLINCH
HAVE BEEN THE MOST AFFECTED ALONG WITH MODERATE FLOOD LEVELS
REACHED AT SPANISHBURG AND MINOR FLOODING AT RICHLANDS AND
PIPESTEM. THESE LOCATIONS MAY CONTINUE TO SLOWLY RISE OVERNIGHT
ESPECIALLY WITH THE POTENTIAL FOR MORE RAINFALL TO MOVE OVER THE
AREA. THE BIG QUESTION IS HOW MUCH MORE LIQUID PRECIPITATION
OCCURS BEFORE THE TRANSITION TO FROZEN. AT THIS POINT ABOUT AN
ADDITIONAL ONE HALF TO ONE INCH OF RAIN /0.50 TO 1.00 INCHES/ IS
FORECAST WHICH COULD EXTEND THE FLOODING. THE ENTIRE HYDROLOGIC
SITUATION SHOULD STABILIZE ONCE THE FREEZING TEMPERATURES AND
PRECIPITATION TAKES OVER VERY LATE TONIGHT.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WINTER WEATHER ADVISORY UNTIL 7 PM EST THURSDAY FOR VAZ007-
     009>018-022-034.
     WINTER STORM WARNING UNTIL 7 PM EST THURSDAY FOR VAZ019-020-
     023-024.
     WINTER WEATHER ADVISORY FROM 6 AM TO 10 PM EST THURSDAY FOR
     VAZ032-033-043>046-058-059.
     WINTER STORM WARNING FROM 3 AM TO 7 PM EST THURSDAY FOR VAZ035-
     047.
NC...WINTER WEATHER ADVISORY UNTIL 7 PM EST THURSDAY FOR NCZ001-002-
     018.
WV...WINTER STORM WARNING UNTIL 7 PM EST THURSDAY FOR WVZ042>044-
     507-508.

&&

$$
SYNOPSIS...AMS
NEAR TERM...JH/KK/WP
SHORT TERM...NF
LONG TERM...DS
AVIATION...AMS/DS/JH/KK
HYDROLOGY...JH


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