Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 042017
AFDRNK

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

.SYNOPSIS...
A COLD FRONT WILL EAST ACROSS THE REGION THIS EVENING INTO
TONIGHT...BEFORE MOVING OFFSHORE LATE THURSDAY. HIGH PRESSURE OVER
THE MISSISSIPPI VALLEY WILL MOVE INTO THE AREA FOR FRIDAY THROUGH
SUNDAY. WIDESPREAD RAIN IS EXPECTED TODAY WITH WINTER
PRECIPITATION TONIGHT AND THURSDAY.

&&

.NEAR TERM /THROUGH THURSDAY/...
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 /20Z WEDNESDAY THROUGH MONDAY/...
AS OF 1245 PM EST WEDNESDAY...

MVFR CONDITIONS WITH POCKETS OF IFR/LIFR IN LOW CLOUDS...FOG AND
RAIN THIS AFTERNOON INTO TONIGHT. SOUTHWESTERLY WINDS WILL
GRADUALLY MIX TO THE SURFACE THIS AFTERNOON...RESULTING IN AN
INCREASE OF WIND SPEEDS TO AROUND 10KTS WITH UP TO 20KT GUSTS.

A COLD FRONT WILL PASS ACROSS THE MOUNTAINS THIS AFTERNOON INTO
TONIGHT. THIS BOUNDARY SHOULD REACH KDAN AFTER 05/00Z. ARCTIC AIR
WILL BUILD IN BEHIND THE FRONT...WHICH WILL CAUSE TEMPERATURES TO
FALL TONIGHT. RAIN WILL TRANSITION TO SLEET AND FREEZING RAIN...THEN
OVER TO SNOW IN MOST LOCATIONS. FOR TIMING EXPECT RAIN CHANGING TO
SLEET BY AROUND 05/05Z FOR KBLF/KLWB...BEFORE CHANGING TO SNOW BY
AROUND 05/10Z. CHANGE OVER TO SLEET FOR KBCB/KROA WILL HAPPEN
CLOSER TO 05/10Z...WITH THE CHANGE TO SNOW NOT TAKING PLACE UNTIL
AFTER SUNRISE THURSDAY. WITH THE CHANGE TO SNOW... SIGNIFICANT
REDUCTIONS IN VISIBILITY CAN BE EXPECTED. CEILINGS WILL FALL TO
IFR/LIFR LEVELS BEHIND THE FRONT.

SLEET WILL CHANGE TO SNOW FROM NORTHWEST TO SOUTHEAST ON THURSDAY.
ROUNDS OF HEAVY SNOW WILL BE POSSIBLE IN THE VICINITY OF THE BLUE
RIDGE LATE THURSDAY MORNING AND DURING THE AFTERNOON AS A WAVE OF
LOW PRESSURE PASSES ALONG THE COASTAL PLAIN. LOW MVFR/IFR
CONDITIONS WILL BE WIDESPREAD THROUGH THE DAYTIME...WITH CLEARING
DURING THE 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.

&&

.HYDROLOGY...
AS OF 300 PM EST WEDNESDAY

FLOODING HAS BEEN WIDESPREAD ACROSS MAINLY TAZEWELL AND MERCER
COUNTIES TODAY AS RAINFALL OF 0.50 TO 0.75 INCHES OVERNIGHT AND THIS
MORNING 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 SHARP RISES ON THE
EAST RIVER AND BRUSH CREEK IN MERCER COUNTY AND INDIAN CREEK IN
MONROE...ALONG WITH NUMEROUS SMALLER AND UNGAGED STREAMS. BOTH THE
BLUESTONE AND CLINCH SHOULD CREST IN THE NEXT FEW HOURS A FEW FEET
ABOVE MINOR FLOOD STAGE. THE BREAK IN RAINFALL THAT HAS TAKEN PLACE
SINCE LATE THIS MORNING THROUGH  AFTERNOON HAS BEEN A HUGE BLESSING
SINCE ALMOST EVERY DROP THAT FELL SEEMED TO BE RUNNING OFF INTO THE
RIVERS AND CREEKS. THE BIG QUESTION IS HOW MUCH MORE LIQUID
PRECIPITATION OCCURS BEFORE THE TRANSITION TO FROZEN. AT THIS POINT
ABOUT AN ADDITIONAL ONE QUARTER TO ONE-HALF INCH OF RAIN /0.25 TO
0.50 INCHES/ IS FORECAST WHICH COULD EXTEND THE FLOODING SOMEWHAT
BUT IS UNLIKELY TO REVERSE A FALLING TREND ONCE IT IS ESTABLISHED.
THE ENTIRE HYDROLOGIC SITUATION SHOULD STABILIZE ONCE THE FREEZING
TEMPERATURES AND PRECIPITATION TAKES OVER LATE TONIGHT.





&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 7 PM EST
     THURSDAY FOR VAZ007-009>018-022-034.
     WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 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 FROM MIDNIGHT TONIGHT TO 7 PM EST
     THURSDAY FOR NCZ001-002-018.
WV...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 7 PM EST
     THURSDAY FOR WVZ042>044-507-508.

&&

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


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