Area Forecast Discussion
Issued by NWS Blacksburg, VA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS61 KRNK 170246
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
946 PM EST TUE DEC 16 2014

.SYNOPSIS...
A COLD FRONT WILL MOVE EAST INTO THE ATLANTIC OCEAN TONIGHT. HIGH
PRESSURE IS EXPECTED TO RETURN FOR WEDNESDAY ASSOCIATED WITH DRY
WEATHER FOR MID WEEK. UNSETTLED WEATHER WILL RETURN FOR THE
WEEKEND AS AN AREA OF LOW PRESSURE MOVES ACROSS THE SOUTHEAST
STATES...REACHING INTO THE MID ATLANTIC REGION SATURDAY.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 935 PM EST TUESDAY...

RADAR VERY QUIET BUT TO BE EXPECTED AS MOISTURE IN THE LOW LEVELS
ACROSS THE MOUNTAINS IS OVERSHOT BY THE RADAR BEAM.
NONETHELESS...AS SHORTWAVE PIVOTS ACROSS THE AREA OVERNIGHT THE NW
FLOW IS GOING TO GENERATE ISOLATED/SCATTERED RAIN/SNOW SHOWERS. AS
THE NIGHT WEARS ON THE MOISTURE BECOMES SHALLOW SO THAT DZ/FZDZ
WILL OCCUR. GIVEN THE LACK OF COVERAGE OF BELOW FREEZING
TEMPS...OPTED TO JUST ISSUE A SPECIAL WX STATEMENT FOR THE NC
MTNS/GRAYSON HIGHLANDS AND WRN GREENBRIER TO ACCOUNT FOR ANY LIGHT
ICING/RIME ICING LATE TONIGHT.

THE FOG OUT EAST TO ERODE AS DRIER AIR WORKS IN AND WINDS PICK UP
SLIGHTLY. ALREADY HAVE SEEN LYH GO FROM 1/4SM FG TO 10SM IN LESS
THAN 1 HOUR.

STILL EXPECT LOWS FROM THE LOWER 30S ACROSS THE WRN SLOPES TO
UPPER 30S...NEAR 40 EAST.

PREVIOUS VALID DISCUSSION...

FOR EAST SIDE OF THE MOUNTAINS...STRONG DOWNSLOPE FLOW WILL MAINTAIN
CLEAR TO PARTLY CLOUDY SKIES OVERNIGHT. WEST TO NORTHWEST WINDS
OF 30-35 KTS ARE PROGGED AT 85H...SO SURFACE WINDS WILL BECOME
GUSTY...ESPECIALLY ALONG THE RIDGE CRESTS AND JUST LEE OF THE BLUE
RIDGE. LOW TEMPERATURES OVERNIGHT WILL RANGE FROM THE UPPER 20S IN
ELEVATIONS ABOVE 3500 FT TO THE MID AND UPPER 30S IN THE PIEDMONT.

UPPER TROF SHIFTS OFFSHORE WEDNESDAY AS WE TRANSITION TO A MORE
ZONAL UPPER FLOW BY WEDNESDAY NIGHT. BLUSTERY NORTHWEST WINDS WILL
CONTINUE INTO WEDNESDAY. DOWNSLOPING DRYING EXPECTED FOR THE EAST.
WHILE IN THE WEST...UPSLOPE FLOW WILL RESULT IN A VERY SHALLOW
MOIST LAYER LOCKED IN UNDER THE SUBSIDENCE INVERSION. WILL
CONTINUE CLOUDS AND THE UPSLOPE LIGHT RA/FZRA THROUGH THE MORNING
HOURS...THEN PRECIPITATION ENDS WHILE CLOUDS LINGER. HIGH
TEMPERATURES WEDNESDAY WILL RANGE FROM THE MID 30S IN THE
NORTHWEST MOUNTAINS TO THE MID 50S IN THE SOUTHEAST.

&&

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

PATTERN IS PROGRESSIVE AND ZONAL THROUGH FRIDAY. MODELS BRING A
SHORT WAVE FROM THE MISSISSIPPI VALLEY THROUGH THE MID ATLANTIC
REGION THURSDAY AND THURSDAY NIGHT. MODELS NOT SHOWING MUCH
CONSENSUS WITH THE LOCATION OF ANY PRECIPITATION ON THURSDAY.
WHATEVER PRECIPITATION DOES FALL WILL BE LIGHT.

SURFACE HIGH PRESSURE WILL EXTEND FROM THE UPPER MISSISSIPPI VALLEY
TO THE TENNESSEE VALLEY THROUGH FRIDAY. THE RIDGE MOVES FAR ENOUGH
EAST BY THE END OF THE DAY FRIDAY FOR SURFACE AND LOW LEVEL WINDS TO
COME AROUND TO THE EAST.

NO CHANGE IN AIR MASS THROUGH THE PERIOD BUT WITH CLOUDS ON
THURSDAY WILL KEEP MAXIMUM TEMPERATURES NEAR COOLER MET GUIDANCE.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 230 PM EST TUESDAY...

FRIDAY NIGHT...A SURFACE NOSE OF HIGH PRESSURE WILL BE ACROSS THE
REGION...ALTHOUGH NOT WITH THE BEST ORIENTATION FOR OPTIMAL WEDGE
CONDITIONS. DESPITE THIS...WE STILL ANTICIPATE A MIX OF TEMPERATURES
A FEW DEGREES EITHER SIDE OF FREEZING AT THE ONSET OF THE
EVENT...AND THROUGH THE SATURDAY NIGHT TIME PERIOD. AT
85H...SOUTHERLY WINDS WILL TRANSPORT MOISTURE INTO THE REGION IN
ASSOCIATION WITH AN AREA OF LOW PRESSURE MOVING THROUGH THE GULF
COAST STATES. GUIDANCE HAS SLOWED BY AN AVERAGE OF 6 HOURS ON THE
ARRIVAL OF PRECIPITATION INTO THE AREA. HAVE ADJUSTED ACCORDINGLY
WITH THE FORECAST. MODEL GUIDANCE IS SHOWING ENOUGH OF A RUN TO RUN
DIFFERENCE WITH EACH OTHER...AND WITH ITS OWN EARLIER RUNS FOR THERE
STILL TO BE NOTABLE UNCERTAINTY AS TO THE LOW LEVEL THERMAL PROFILE
AT THE ONSET...AND DURING THE COURSE OF THE PRECIPITATION EVENT THIS
LOW WILL BRING TO OUR REGION THROUGH SATURDAY NIGHT. BY
SUNDAY...THERE IS BETTER AGREEMENT WITH THE MODELS THAT THE AREA
WILL BE ON THE BACKSIDE OF THE SYSTEM WITH ENOUGH COLD AIR ACROSS
THE REGION WITH A STIFF NORTHWEST WIND TRAJECTORY FOR UPSLOPE SNOW
SHOWERS IN THE WEST TO CONCLUDE THE EVENT.

THE BEST CONSENSUS OF THE MODELS SUGGEST SOME TYPE OF WINTRY MIX
WHERE THE SURFACE AND BOUNDARY LEVEL TEMPERATURES ARE COLD ENOUGH
LATE FRIDAY NIGHT...THROUGH SATURDAY NIGHT. MOST OF THIS WINTRY MIX
LOOKS TO BE CONFINED TO THE MOUNTAINS. ANY MIX ACROSS THE PIEDMONT
WILL BE LIMITED BY MILDER SURFACE AND BOUNDARY LEVEL TEMPERATURES
THERE...WITH THE BEST POTENTIAL FOR A MIX TO BE ALONG AND NORTH OF
THE ROANOKE RIVER VALLEY. SOUTHSIDE VIRGINIA...SOUTH INTO PARTS OF
NORTH CENTRAL NORTH CAROLINA AT THIS POINT LOOK TO BE PRIMARILY RAIN.

GIVEN THESE VARIOUS UNCERTAINTIES AND LOCAL POLICY...THE FORECAST
FRIDAY NIGHT THROUGH SATURDAY SATURDAY NIGHT WILL BE A RAIN VERSUS
SNOW FORECAST...WITH THE FLEXIBILITY OF SOME AREAS WITH RAIN AND
SNOW SIMULTANEOUSLY. WHILE OUR FINAL WEATHER PICTURE MAY DEPICT A
GREATER RANGE OF WINTRY PRECIPITATION TYPES...RAIN VERSUS SNOW IS A
CONSERVATIVE APPROACH TO TAKE AT THIS POINT. IN A COUPLE OF
DAYS...OUR CONFIDENCE MAY HAVE INCREASED ENOUGH TO ALLOW FOR A
GREATER MIX OF PRECIPITATION TYPES IN THE FORECAST DURING THIS
PERIOD OF THE FORECAST.

AS MENTION EARLIER...BY THE TIME WE GET TO SUNDAY...MODEL GUIDANCE IS
IN FAIRLY GOOD AGREEMENT THAT THE SYSTEM WILL BE LIFTING OUT OF THE
REGION...AND SUB FREEZING AIR WILL HAVE WRAPPED IN BEHIND THE SYSTEM
AT THE LOWER LEVELS. ANY LINGERING PRECIPITATION HAS A GREATER
CHANCE TO BE SNOW OR RAIN WITHOUT THE PRESENCE OF A WARM NOSE ALOFT.
BY SUNDAY AFTERNOON INTO SUNDAY NIGHT...LINGERING UPSLOPE SNOW
SHOWERS ACROSS THE PREFERRED AREA OF SOUTHEAST WEST VIRGINIA AND
NEIGHBORING PARTS OF SOUTHWEST VIRGINIA WILL GRADUALLY ERODE AS
DRIER AIR WORKS ITS WAY INTO THE REGION AND THE LOW LEVEL FLOW
GRADUALLY BACKS WEST TO SOUTHWEST.

MONDAY INTO MONDAY NIGHT...HIGH PRESSURE BUILDS INTO THE THE REGION
WITH LIGHT WINDS...LIMITED CLOUD COVER AND NO PRECIPITATION EXPECTED.

TUESDAY WILL BE ANOTHER DAY WITH CONSIDERABLE UNCERTAINTY. THE GFS
IS QUICK TO BRING THE COLD FRONT TOWARDS THE REGION IN ASSOCIATION
WITH AN UPPER TROUGH PUSHING THROUGH THE GREAT LAKE REGION. THIS
SYSTEM IS KEPT DISTINCT FROM A DISTURBANCE OFF THE COAST OF THE
CAROLINAS THAT HAS LITTLE OR NO INTERACTION WITH THE GREAT LAKES
TROUGH THROUGH AT LEAST THE END OF OUR FORECAST PERIOD. FOLLOWING
THIS SOLUTION YIELD LIMITED COVERAGE OF RAIN OR SNOW REACHING THE
WESTERN PARTS OF THE AREA THROUGH THE END OF THE DAY TUESDAY. THE
ECMWF SOLUTION ALSO HAS THE TWO SYSTEMS DISTINCT THROUGH
TUESDAY...BUT FOR A DIFFERENT REASON. THIS SOLUTIONS IS FARTHER WEST
WITH THE COASTAL SYSTEM...AND WRAPS MOISTURE...AND A WARM
NOSE...INTO OUR AREA DURING THE COURSE OF THE DAY TUESDAY. THE GREAT
LAKES SYSTEM IS NOT AS PROGRESSIVE...AND HAS THE TIME TO ELONGATE MORE
SOUTH INTO THE MISSISSIPPI RIVER VALLEY. IF THE ECMWF IS ON
TRACK...THE AREA WILL HAVE A GENEROUS COVERAGE OF A WINTRY MIX
MOVING INTO THE REGION FROM SOUTHEAST TO NORTHWEST ON TUESDAY. OUR
FORECAST AT THIS POINT WILL RESEMBLE MORE THAT OF THE GFS.

TEMPERATURES DURING THE FORECAST PERIOD WILL BE TRICKY. WHILE WE ARE
EXPECTING A GENERAL TREND TOWARDS MILDER TEMPERATURES EACH DAY PAST
TUESDAY...HOW MUCH...AND WHERE ANY SUBSTANTIAL ACCUMULATIONS OF SNOW
ARE DEPOSITED WILL PLAY A FACTOR IN BOTH THE HIGHS AND THE LOWS. AT
THIS POINT...AM LEANING ON THE LOW SIDE OF GUIDANCE...WITH SOME
ALLOTMENT TOWARDS EVEN MORE COOLER WHERE...AT LEAST NOW...THE BEST
CHANCE OF SNOW IS EXPECTED. AT THIS POINT...WILL NOT TOUCH THE FOG
POTENTIAL ONCE WE START TO GET INTO THE RETURN FLOW SIDE OF THE
SURFACE HIGH. ALTHOUGH...AS MILDER AIR STARTS ADVECTING ACROSS ANY
REMAINING SNOWPACK...THE DEW POINT OF THAT AIR WILL LIKELY BE MILDER
THAN THE TEMPERATURE OF THE SNOW IT WILL BE MOVING ACROSS.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
AS OF 625 PM EST TUESDAY...

SURFACE COLD FRONT CONTINUES TO PUSH EAST THROUGH THE REGION THIS
EVENING. WHILE THE IMPACT OF THE WIND SHIFT HAS TAKEN PLACE ALOFT
IN AREAS EAST OF THE CREST OF THE BLUE RIDGE...IT HAS NOT WORKED
ITS WAY TO THE SURFACE IN ALL LOCATIONS YET. WE EXPECTED NORTHWEST
WINDS TO PREVAIL AT ALL LOCATIONS OVERNIGHT. IN THE EAST...THIS
WILL HELP ERODE THE LINGERING IFR/MVFR CLOUD COVER ALONG AND EAST
OF A KLYH-KDAN LINE AS THE NIGHT PROGRESSES. GUSTY CONDITIONS AND
SCATTERED LIGHT RAIN SHOWERS OR SPRINKLES ARE POSSIBLE THIS
EVENING ACROSS THE MOUNTAINS ALONG WITH A CONTINUATION OF IFR/MVFR
CLOUD COVER. LOCALIZED IFR CONDITIONS ARE POSSIBLE TONIGHT ALONG
THE WESTERN SLOPES VCNTY OF KBLF AND JUST WEST OF KLWB WITH THE
POTENTIAL FOR LIGHT FREEZING DRIZZLE AND FOG.

DURING THE DAY WEDNESDAY...EXPECT A GRADUAL IMPROVEMENT TO VFR
CONDITIONS ACROSS THE MOUNTAINS WITH CLOUD COVER ERODING FROM
EAST TO WEST. WINDS WILL REMAIN GUSTY...IF NOT GUST A LITTLE
STRONGER NEAR 25KTS IN SOME LOCATIONS FROM THE LATE MORNING
THROUGH THE MID AFTERNOON. WINDS WILL START TO WEAKEN IN THE LATE
AFTERNOON...BUT STILL PREVAIL IN THE 8 TO 10 KT RANGE.

EXTENDED DISCUSSION...

THURSDAY AND FRIDAY LOOK RELATIVELY BENIGN. THERE IS THE POTENTIAL
FOR A PERIOD OF MVFR THURSDAY ASSOCIATED WITH AN UPPER LEVEL
DISTURBANCE WHICH IS FORECAST TO PASS JUST SOUTH OF THE REGION
VCNTY OF THE VA/NC BORDER.

POTENTIAL EXISTS FOR A WINTER STORM TO IMPACT THE REGION THIS
WEEKEND...FLIGHT CONDITIONS DETERIORATING ACROSS THE AREA LATE
FRIDAY NIGHT INTO SATURDAY. LOW PRESSURE IS EXPECTED TO FORM OVER
TEXAS FRIDAY...THEN TRACK NORTHEAST TO NEAR THE MID ATLANTIC
COAST BY LATE SATURDAY. THIS TRACK WILL PLACE OUR FORECAST AREA ON
THE COLD SIDE OF THE SYSTEM PROVIDING AN OPPORTUNITY FOR
ACCUMULATING SNOW OR A WINTRY MIX. AVIATION INTERESTS WILL NEED TO
MONITOR THIS SITUATION AS LATER FORECASTS BECOME AVAILABLE. THIS
WILL LIKELY HAVE AN IMPACT ON AIR TRAVEL OVER THE WEEKEND...FROM
THE SOUTHERN APPALACHIANS AND CAROLINAS NORTH TO THE MID ATLANTIC.

&&

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

&&

$$
SYNOPSIS...PM
NEAR TERM...KK/WP
SHORT TERM...AMS
LONG TERM...DS
AVIATION...DS/KK/PM


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.