Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 031839
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
139 PM EST TUE MAR 3 2015

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE MID ATLANTIC COAST TODAY...THEN A
WARM FRONT WILL LIFT NORTH THROUGH THE REGION THIS EVENING. LOW
PRESSURE OVER THE CENTRAL PLAINS WILL TRACK INTO SOUTHEAST CANADA
AND WILL PUSH A COLD FRONT INTO THE REGION ON WEDNESDAY. COLDER
AIR BEHIND THE FRONT WILL ALLOW FOR A TRANSITION FROM RAIN TO SNOW
WEDNESDAY NIGHT AND THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 138 PM EST TUESDAY...

WITH TEMPERATURES RISING THIS AFTERNOON INTO THIS EVENING. THE
THREAT FOR WIDESPREAD ICING PROBLEMS HAS ENDED...THUS THE WINTER
WEATHER ADVISORY IS CANCELLED. SOME LIGHT RAIN AND PATCHES OF
DRIZZLE ARE EXPECTED FOR THE THIS AFTERNOON. ISOLATED POCKETS OF
ICE MAY BE POSSIBLE ON THE COLDEST SURFACES. DRIVER SHOULD WATCH
FOR SLICK ICY SPOTS ON ROADWAYS.

AS OF 1000 AM EST TUESDAY...

CANCELLED THE WINTER WEATHER ADVISORY MAINLY WEST OF I77 WHERE
TEMPERATURES WERE ABOVE FREEZING MARK AND EXPECTED TO REMAIN AS
SUCH...AND RADAR COVERAGE IS LIGHT. STILL CONCERN OVER DIABATIC
COOLING OF TEMPERATURES WITH LIGHT PRECIPITATION...THUS WILL HOLD
WITH REST OF WINTER WEATHER ADVISORY AT THIS TIME. MODIFIED POPS
WITH LATEST RADAR TRENDS. SHAPED MORNING TEMPERATURES WITH SFC OBS
AND LATEST MODEL TRENDS. MORE CHANGES LATER THIS MORNING IN THE
ACTIVE WEATHER PATTERN .


AS OF 415 AM EST TUESDAY...

LOWER CLOUDS WERE JUST FILLING IN ACROSS THE FORECAST AREA THIS
MORNING. HAVE MADE ADJUSTMENTS TO THE TIMING OF THE PRECIPITATION
BASED ON RADAR TRENDS AND THE TIMING SHOWN ON THE LAST FEW RUNS OF
THE HRRR AND THE LATEST WRF GUIDANCE. HAVE THEREFORE MADE ADJUSTMENTS
TO THE VALID TIME OF THE ADVISORIES. APPEARS A MORE ORGANIZED AREAS
OF PRECIPITATION WILL CROSS THE NORTHERN COUNTY WARNING AREA BETWEEN
8AM AND NOON. STILL EXPECTING A BETTER PROBABILITY OF PRECIPITATION
ON THE EASTERN SLOPES OF THE BLUE RIDGE. OTHERWISE...NO WELL DEFINED
FEATURES THAT WILL DEFINE WHERE AND WHEN PRECIPITATION WILL FALL.

WHEREVER THE PRECIPITATION IS...IT WILL BE LIGHT. BUFKIT NOT
SHOWING GOOD DENDRITIC GROWTH AND BY 15Z/10AM...WARM NOSE WILL BE
WELL STRONG ENOUGH TO RESULT IN LIQUID AS THE HYDROMETEORS FALL
THROUGH THAT LAYER. SO SURFACE TEMPERATURES WILL BE THE DECIDING
FACTOR IN PRECIPITATION TYPE. NEW RIVER VALLEY THROUGH THE
ALLEGHANY HIGHLANDS WERE BELOW FREEZING. ONLY A SLOW RISE IN
TEMPERATURES EXPECTED TODAY. GUIDANCE KEPT THE NORTHEAST
COUNTIES...MAINLY FROM LYNCHBURG INTO AMHERST AND ROCKBRIDGE
COUNTY BELOW FREEZING FOR MUCH OF THE DAY. HAVE DELAYED THE START
OF THE WINTER WEATHER ADVISORY AND EXTENDED THE ADVISORY THROUGH
LATER IN THE DAY WHERE THE TEMPERATURE REMAINS BELOW FREEZING.

TONIGHT...A STRONG LOW LEVEL JET PUSHES UP TEMPERATURES AND DEW
POINTS. LOWS WILL OCCUR IN THE EVENING. AFTER MIDNIGHT...THE COLD
FRONT APPROACHES AND THE PROBABILITY OF MODERATE RAIN IN THE
NORTHWEST COUNTY WARNING AREA INCREASES.

&&

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

EXPECT TO START WEDNESDAY WITH A COLD FRONT SITUATED FROM THE
ALLEGHANY HIGHLANDS THROUGH THE MOUNTAIN EMPIRE. STRONG MOISTURE
FLOW INTO THE AREA ON A 50KT TO 60KT SOUTHWESTERLY LOW LEVEL JET
WILL PUSH PRECIPITABLE WATER VALUES TO 1.0-1.1 INCHES IN THE
WEST...AND AS HIGH AS 1.4 INCHES FURTHER EAST...ALL SIGNIFICANTLY
ABOVE NORMAL FOR EARLY MARCH.

DURING THE MORNING...RAIN WILL BE WIDESPREAD WEST OF THE BLUE
RIDGE...ALTHOUGH THE STRONGEST LIFT/HEAVIEST RAINFALL IS EXPECTED TO
BE WEST OF THE CONTINENTAL DIVIDE...JUST SKIRTING OUR SOUTHEAST WEST
VIRGINIA COUNTIES...PARTICULARLY THE WEST FACING SLOPES. FURTHER
EAST...WILL LIKELY SEE A BAND OF HEAVY RAIN JUST AHEAD OF THE FRONT
AS IT SLOWLY DRIFTS EAST THROUGH THE DAY...WITH SOME DRYING TAKING
PLACE BEHIND THE BOUNDARY AS WINDS SHIFT NORTHWESTERLY AND
DOWNSLOPE.

DURING WEDNESDAY AFTERNOON AND EVENING...THE COLD FRONT WILL
SLOW/STALL ACROSS THE SOUTHSIDE AND NORTH CAROLINA PIEDMONT AS A
STRONG WAVE DEVELOPS OVER NORTHERN GEORGIA AND PUSHES NORTHEAST
ALONG THE BOUNDARY. THE WAVE WILL PASS JUST SOUTHEAST OF OUR AREA
DURING THE EARLY MORNING HOURS OF THURSDAY...WITH STRONG CONVERGENCE
DEVELOPING FROM THE ALLEGHANY HIGHLANDS SOUTHWARD ALONG THE BLUE
RIDGE...SUPPORTING AN ADDITIONAL ROUND OF POTENTIALLY HEAVY RAIN.

AS THE WAVE PASSES OUR AREA DURING LATE THURSDAY MORNING...IT WILL
ENHANCE THE NORTHWESTERLY FLOW ACROSS THE MOUNTAINS...DRAWING COLD
AIR ASSOCIATED WITH ARCTIC HIGH PRESSURE FURTHER ACROSS OUR AREA.
THE SURGE OF COLDER AIR HUGGING THE SURFACE WILL CAUSE RAIN TO
CHANGE TO SLEET AND/OR FREEZING RAIN FOR A FEW HOURS ACROSS THE
MOUNTAINS...BEFORE FINALLY CHANGING TO SNOW BY THURSDAY AFTERNOON.
BECAUSE WE ARE EXPECTING MORE SLEET AND FREEZING RAIN THAN
PREVIOUSLY FORECAST...WENT WITH LOWER SNOWFALL TOTALS FOR THURSDAY.
RIGHT NOW...LOOKING AT THE POSSIBILITY OF WINTER STORM SNOW AND
SLEET AMOUNTS FOR WESTERN GREENBRIER...AND PERHAPS BATH AND
ROCKBRIDGE COUNTIES IN SPOTS...BUT DO NOT HAVE ENOUGH CONFIDENCE TO
GO WITH A WINTER STORM WATCH AT THIS POINT. WILL LET THE DAY SHIFT
HAVE ANOTHER LOOK AT THE COMING 03/12Z MODEL RUNS.

PRECIPITATION WILL WIND DOWN THURSDAY AFTERNOON AND EVENING AS HIGH
PRESSURE BUILDS IN FROM THE WEST...SETTLING ACROSS THE MID AND UPPER
OHIO RIVER VALLEY BY FRIDAY MORNING. STRONG RADIATIONAL COOLING WILL
MEAN ONE MORE SHOT OF SINGLE DIGIT TEMPERATURES TO START THE DAY
ACROSS THE MOUNTAINS...WITH TEENS EXPECTED ACROSS THE PIEDMONT. HIGH
PRESSURE WILL SHIFT TO NEW ENGLAND...WHERE IT WILL THEN WEDGE
SOUTHWARD FRIDAY NIGHT...HUGGING THE EASTERN FACE OF THE
APPALACHIANS.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 145 PM EST MONDAY...

HIGH PRESSURE WILL BE IN CONTROL OF OUR WEATHER PATTERN THROUGH
AT LEAST SATURDAY NIGHT. THE HIGH WILL GRADUALLY BUILD INTO THE
AREA FROM THE WEST...AND MAKE ITS WAY TO THE COAST BY SATURDAY.
THIS WILL ALLOW FOR A TREND TOWARD MILDER CONDITIONS AS THE LOW
LEVEL FLOW ACROSS THE AREA BECOMES GRADUALLY MORE SW-W...WHILE A
SHORTWAVE RIDGE AND RISING 850 TEMPS TAKE PLACE.

SUNDAY INTO MONDAY A GENEROUS AMOUNT OF VARIATIONS IN THE MODELS
TAKE PLACE. WHILE BOTH THE GFS AND THE NAM EVENTUALLY COME INTO
AGREEMENT OF A LONG WAVE TROUGH OVER THE EASTERN THIRD OF CONUS BY
MONDAY OR TUESDAY OR NEXT WEEK...HOW THE SOLUTIONS COME TO BE THAT
WAY HAVE NOTABLE DIFFERENCES. THE GFS IS MORE PROGRESSIVE IN
ESTABLISHING THE TROUGH IN THE EAST BY SUNDAY...AND ANY SOUTHERN
STREAM SYSTEMS EASILY BYPASS OUR REGION EXITING THE U.S. NEAR THE
GA/FL BORDER. THE ECWMF IS NOT A QUICK TO ESTABLISH AN EAST COAST
TROUGH...AND A SUCH...SOUTHERN STREAM SYSTEMS HAVE A BETTER
OPPORTUNITY TO PROGRESS NORTHEAST THROUGH OUR REGION ON THE EAST
SIDE OF AN APPROACHING SHORTWAVE TROUGH.

OUR FORECAST FOR SUNDAY INTO MONDAY WILL BE A CONSENSUS OF THESE
TWO...WITH IT RESEMBLING A WATERED DOWN VERSION OF THE ECWMF IN
TERMS OF PRECIPITATION POTENTIAL ON SUNDAY AND SUNDAY NIGHT...AND
ALSO STAYING ON MORE OF THE MILD SIDE THAN COLD IN REGARDS TO
MONDAY.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
AS OF 1230 PM EST TUESDAY...

MVFR CONDITIONS WITH POCKETS OF IFR IN PRECIPITATION...CLOUDS AND
FOG THIS AFTERNOON INTO TONIGHT. STRONG SOUTH TO SOUTHWEST WINDS
ALOFT WILL BRING ABUNDANT MOISTURE INTO THE REGION THIS AFTERNOON
INTO TONIGHT. TEMPERATURES WILL SLOWLY RISE THIS AFTERNOON INTO
TONIGHT. THIS WILL END THE THREAT FOR FREEZING RAIN/FREEZING
DRIZZLE ACROSS OUR AREA. TRIMMED BACK AND NARROWED THE WINDOW FOR
LOW LEVEL WIND SHEAR IN THE TAFS FOR TONIGHT. CEILINGS AND
VISIBILITIES WILL BE IFR TO LIFR FOR MUCH OF THE AREA IN LOW
CLOUDS AND FOG THIS EVENING INTO WEDNESDAY MORNING.

ANOTHER LOW PRESSURE SYSTEM THAT WILL IMPACT ALL OF THE REGION
WILL TRACK FROM THE CENTRAL PLAINS INTO SOUTHEAST CANADA BY WEDNESDAY.
THIS WILL RESULT IN WIDESPREAD SUB-VFR CONDITIONS ACROSS THE AREA WEDNESDAY
AND THURSDAY WITH ABUNDANT RAIN. A COLD FRONT WILL CROSS THROUGH
THE AREA ON WEDNESDAY.

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

EXTENDED FORECAST...

 WINTER PRECIPITATION IS LIKELY BEHIND THE FRONT WEDNESDAY NIGHT
AND THURSDAY. AT THIS TIME THE MOST LIKELY PRECIPITATION TYPES ARE
SNOW AND SLEET.

FRIDAY AND SATURDAY WILL SEE A RETURN TO HIGH PRESSURE AND VFR
WEATHER.

&&

.HYDROLOGY...
AS OF 300 PM EST MONDAY

LIKELY TO SEE SOME SUBSTANTIAL RISES ON AREA RIVERS AND STREAMS IN
RESPONSE TO UPCOMING RAIN EVENT AND SNOWMELT IN THE
MOUNTAINS...QUESTIONS REMAIN ABOUT HOW SUBSTANTIAL. SIGNIFICANT SNOW
AMOUNTS ARE NOW CONFINED TO PARTS OF THE UPPER JAMES AND
GREENBRIER RIVER BASINS WHERE THE LATEST AVAILABLE ESTIMATES FROM
THE NATIONAL OPERATIONAL REMOTE SENSING CENTER SHOW ROUGHLY 1 TO 3
INCHES OF SNOW WATER EQUIVALENT WITH ISOLATED 4 INCHES IN THE
HIGHEST ELEVATIONS OF THE GREENBRIER. IN THE OTHER MAJOR RIVER
BASINS...NEW...ROANOKE/DAN AND TENNESSEE... MELTING OVER THE
WEEKEND AND TODAY HAS REDUCED THE SNOW TO LESS THAN 1 INCH OF SNOW
WATER AND IN MOST PLACES ZERO.

THE OTHER ELEMENT OF COURSE IS THE QPF. 12Z MODELS (INCLUDING
LATEST EC) HAVE NUDGED THE HEAVIEST QPF A LITTLE MORE TO THE
WEST...REDUCING AMOUNTS IN THE JAMES AND GREENBRIER SOME. IT STILL
APPEARS AS IF 1 TO 2 INCHES COULD FALL ACROSS THE WESTERN BASINS
BY 12Z THURSDAY AND COMBINED WITH SNOWMELT THIS COULD PRODUCE AT
LEAST MINOR RIVER FLOODING ALONG THE GREENBRIER AND POSSIBLY THE
UPPER JAMES. GUIDANCE RECEIVED FROM OHRFC THIS MORNING SUGGESTED
MINOR FLOOD STAGE AT ALDERSON WV ON THE GREENBRIER LIKELY BY EARLY
THURSDAY WITH THE COMBINED SNOWMELT AND QPF. HOWEVER...GIVEN THE
CONTINUED UNCERTAINTIES WILL HOLD OFF ON A FLOOD WATCH AT THIS
POINT.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

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


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