Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 281735
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1235 PM EST SAT FEB 28 2015

.SYNOPSIS...
COLD HIGH PRESSURE WILL WEDGE SOUTH ALONG THE EASTERN SLOPES OF
THE APPALACHIANS TODAY AND PERSIST INTO SUNDAY. OUR NEXT WEATHER
SYSTEM WILL BRING A LIGHT WINTRY MIX TO THE AREA SUNDAY INTO
MONDAY. TEMPERATURES WILL MODERATE THROUGH THE MIDDLE OF THE
WEEK...PRIOR TO THE PASSAGE OF A STRONG COLD FRONT WEDNESDAY INTO
THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1033 AM EST SATURDAY...
WITH SOME SUNSHINE AND TEMPERATURES WARMING ABOVE FREEZING...DECIDED
TO CANCEL WINTER WEATHER ADVISORY FOR BLACK ICE ACROSS NORTH
CAROLINA. NUDGED HIGH TEMPERATURES UP A FEW DEGREES FOR THIS
AFTERNOON IN THE SOUTHEAST.

AS OF 916 AM EST SATURDAY...

A 1044 MB SURFACE HIGH PRESSURE CENTERED OVER PENNSYLVANIA WILL
PUSH SOUTH INTO OUR REGION TODAY INTO TONIGHT. MADE SOME MINOR
ADJUSTMENTS IN TEMPERATURES FOR THIS MORNING INTO THIS AFTERNOON.
WILL WAIT FOR THE 12Z MODEL RUN BEFORE MAKING ANY ADJUSTMENTS TO
TONIGHT FORECAST WITH THE RETURN MOISTURE AS THE HIGH SLIDES EAST.
MORE CHANGES LATER...

AS OF 230 AM EST SATURDAY...

DEVELOPING WEDGE DOWN THE EASTERN SLOPES OF THE MOUNTAINS THE MAIN
ISSUE OVER THE NEXT 24 HOURS AS ARCTIC HIGH PRESSURE SLIDES SE FROM THE
MID ATLANTIC STATES TODAY TO ALONG THE EASTERN SEABOARD OVERNIGHT. THIS
WILL CREATE MORE OF AN EASTERLY COMPONENT TO THE LOW LEVEL FLOW TODAY
ALLOWING SOME LOW LEVEL MOISTURE TO WORK WESTWARD UNDER THE INVERSION
WHILE BEING TOPPED BY SHEARED HIGH/MID LEVEL CLOUDINESS FROM DAMPENING
SHORTWAVE ENERGY TO THE WEST. GIVEN SUCH LOW DEWPOINTS DOESN`T APPEAR
THAT THE MOISTURE WILL EVER GET DEEP ENOUGH TO PRECIPITATE ANYTHING
MORE THAN SPOTTY FLURRIES/DRIZZLE OUT EAST TODAY SO LEAVING POPS
OUT FOR NOW. HOWEVER CLOUDS REMAIN TRICKY WITH POTENTIAL TO SEE A
LOW CLOUD CANOPY GET LOCKED IN ALONG/EAST OF THE BLUE RIDGE TODAY
WITH MORE MID DECK OVER THE WEST. THIS MAY SPELL AN EVEN COLDER
DAY THAN WHAT MOS SHOWS ESPCLY WHERE STARTING OFF IN THE SINGLE
DIGITS AND TEENS. THEREFORE LEANING TOWARD MORE CLOUDS THROUGH THE
AFTERNOON AND HIGHS CLOSER TO THE COLDER MAV MOS OUTSIDE OF THE
SOUTHEAST WHERE THE MET LOOKS BETTER PER STARTING OUT A BIT WARMER
UNDER LOW CLOUDS ALREADY.

PARENT SURFACE HIGH WILL SLOWLY WEAKEN OVERNIGHT WITH THE LOW LEVEL
TRAJECTORY TURNING MORE SOUTHEAST OVER THE WEST WHERE MOST MODELS
CONTINUE TO SHOW AN AXIS OF RETURN MOISTURE RUNNING UP INTO THE SW
ZONES LATE. NAM CONTINUES TO BE THE WETTEST AS TYPICAL WITH RETURN FLOW
ISENTROPIC LIFT TYPE SITUATIONS...WHILE THE EC/CMC REMAIN BASICALLY
DRY...AND THE GFS IN BETWEEN PLUS SLIGHTLY SLOWER. GIVEN PAST EVENTS
WILL TREND TOWARD THE NAM TIMING BUT WITH QUITE LESS QPF WHICH WILL BE
RUNNING INTO RESIDUAL COLD/DRY AIR THAT WILL BE RETREATING AS STEADY
WARMING ALOFT KICKS IN. THIS SCENARIO UNDER A DEVELOPING WARM NOSE
ALOFT WOULD PERHAPS BRING SOME LIGHT FREEZING RAIN/SLEET INTO PARTS OF
NW NORTH CAROLINA LATE WITH A LIGHT WINTRY MIX SPREADING UP ALONG THE
SOUTHERN BLUE RIDGE AND POINTS EAST OF BCB/ROA BY DAYBREAK. HOWEVER
WONT GO HIGHER THAN LOW CHANCE TO SLIGHT POPS FOR NOW...BUT INCLUDE
A MENTION IN THE HWO OVER THE SOUTH/SW LATE FOR AT LEAST SPOTTY
ICING GIVEN FORECAST SURFACE WET BULBS STILL BELOW FREEZING. OTHERWISE
MAINLY CLOUDY MOST SPOTS WITH EARLY LOWS...MOSTLY 20S...STEADYING
OR SLOWLY RISING AFTER MIDNIGHT WITHIN THE SURFACE-85H WEAK WARM
ADVECTION REGIME.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
AS OF 330 AM EST SATURDAY...

COMPLICATED FORECAST THROUGH THE SHORT TERM. GUIDANCE HAD TRENDED
TOWARD THE FASTER NAM AND PRECIPITATION LOOKS TO ARRIVE IN THE AREA
SUNDAY MORNING WITH GOOD ISENTROPIC LIFT AS WARM SWLY WINDS RUN OVER
THE TOP OF THE COLD AIR WEDGE. SPEAKING OF THE WEDGE...BELIEVE THIS
WILL BE A TOUGH NUT TO CRACK WITH VERY COLD ANTECEDENT CONDITIONS
AND A SNOW PACK TO REINFORCE THE COLD AIR. HAVE TRENDED THE TEMP
FORECAST DOWN EAST OF THE BLUE RIDGE. AS IS USUALLY THE
CASE...EXPECT TEMPS WEST TO SLOWLY RISE THROUGH SUNDAY AND CONTINUE
RISING INTO SUNDAY NIGHT. AREAS TO THE EAST WILL RISE EVER SO SLOWLY
DURING THE DAY ON SUNDAY BUT EXPECT A SURGE IN TEMPS LATE SUNDAY
NIGHT INTO MONDAY AS THE APPROACHING COLD FRONT FINALLY BOOTS THE
WEDGE OUT. THIS MEANS WESTERN AREAS WILL BE LOOKING AT A MIX OF
FREEZING RAIN AND SLEET SUNDAY MORNING THEN GOING TO RAIN BY THE
AFTERNOON. NORTHERN AND EASTERN AREAS WILL BE LOOKING AT MAINLY
FREEZING RAIN AND SLEET...AND THE PRECIPITATION WILL LIKELY END
BEFORE IT HAS A CHANCE TO CHANGE OVER. THE UPSIDE IS THAT THIS LOOKS
LIKE A LOW QPF EVENT SO WHILE FREEZING RAIN AND A GLAZE OF ICE WILL
BE FAIRLY WIDESPREAD IT WILL BE UNDER ONE TENTH OF AN INCH. AS
COLDER AIR MOVES IN WITH THE FRONT WE WILL SEE UPSLOPE SNOW SHOWERS
WITH SOME MINOR SLUSHY ACCUMULATIONS OF AN INCH OR LESS ACROSS THE
FAR WESTERN SLOPES LATE SUNDAY NIGHT INTO MONDAY MORNING.

THINGS QUIET DOWN AS HIGH PRESSURE BUILDS IN MONDAY AFTERNOON WITH
GUSTY NORTHWEST WINDS. HOWEVER...OUR REPRIEVE WILL BE SHORT LIVED AS
THE NEXT SYSTEM WILL BE APPROACHING FROM THE WEST AND SPREAD
PRECIPITATION BACK INTO THE AREA TUESDAY MORNING. THIS LOOKS LIKE
ANOTHER WEDGE SCENARIO WITH MIXED PRECIPITATION BUT DETAILS ARE
SKETCHY AT THIS POINT SO WILL BE LOOKING TO LATER MODEL RUNS TO SEE
HOW THE SITUATION EVOLVES.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
AS OF 315 PM EST FRIDAY...

TUESDAY NIGHT LOWS WILL FALL INTO THE UPPER 30S AND LOW 40S MOST
LOCATIONS. BY WEDNESDAY MORNING...THE LOW PRESSURE SYSTEM WILL BE
LOCATED OVER SOUTHERN CANADA...AND WILL DRAG A STRONG COLD FRONT
TOWARD THE APPALACHIAN CHAIN. FORECAST MODELS VARY IN THE TIMING OF
THE FRONT`S ARRIVAL INTO OUR AREA...WITH THE GENERAL CONSENSUS
LEANING TOWARD THE FRONT REACHING OUR SOUTHEAST WEST VIRGINIA
COUNTIES DURING THE EVENING. AS SUCH...EXPECT WEDNESDAY TEMPERATURES
TO BE THE WARMEST WE HAVE SEEN IN WEEKS...WITH HIGHS RANGING FROM
THE LOW/MID 50S FOR THE MOUNTAINS...AND THE UPPER 50S TO MID 60S FOR
THE PIEDMONT.

ATMOSPHERIC MOISTURE ACROSS OUR AREA AHEAD OF THE FRONT WILL BE
SIGNIFICANTLY ABOVE NORMAL FOR EARLY MARCH...SO WILL BE KEEPING OUR
EYE ON THE POTENTIAL FOR WIDESPREAD HEAVY RAIN FOR WEDNESDAY
EVENING/WEDNESDAY NIGHT...ESPECIALLY IF THE COLD FRONT BECOMES
STALLED ACROSS OUR AREA AS SOME MODELS SUGGEST. WHILE WE SHOULD SEE
A SIGNIFICANT REDUCTION IN THE SNOWPACK ACROSS OUR AREA BEFORE THE
HEAVY PRECIPITATION ARRIVES...EXPECT THERE WILL STILL BE AREAS OF
FROZEN GROUND DUE TO THE PROLONGED COLD WEATHER OF RECENT WEEKS...
WHICH WILL CAUSE MUCH OF THE RAIN TO TRANSLATE DIRECTLY INTO RUNOFF
RATHER THAN SOAK INTO THE GROUND. WILL CONTINUE TO MONITOR THE
EVOLUTION OF THIS SYSTEM THROUGH THE WEEKEND FOR THE POTENTIAL OF
FLOODING WEDNESDAY NIGHT.

THE COLD FRONT WILL REPRESENT THE LEADING EDGE OF YET ANOTHER ARCTIC
AIRMASS...WHICH WILL ADVANCE FROM THE CENTRAL PLAINS UP THE OHIO
RIVER VALLEY ON THURSDAY. DOWNSLOPE NORTHWESTERLY FLOW WILL LEAD TO
DRYING CONDITIONS AND DIMINISHING CLOUD COVER ACROSS OUR AREA...WITH
AFTERNOON HIGHS RANGING FROM THE 30S WEST TO THE 40S EAST.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AS OF 1235 PM EST SATURDAY...

AS HIGH PRESSURE IN PENNSYLVANIA WEDGES SOUTH INTO OUR
REGION...EASTERLY FLOW EXPECTED THIS AFTERNOON INTO TONIGHT.
VFR CONDITIONS WILL LOWER TO MVFR THIS EVENING INTO TONIGHT.
MID AND HIGH CLOUDS WILL INCREASE ABOVE THE TRAPPED LOW LEVEL
MOISTURE IN ADVANCE OF AN APPROACHING COLD FRONT.

THE LOW LEVEL WIND FLOW WILL CONTINUE TO VEER SOUTHEASTERLY
ACROSS THE MOUNTAINS AND EASTERLY ACROSS THE PIEDMONT AS THE
CENTER OF HIGH PRESSURE SHIFTS OFF THE NEW ENGLAND COAST.
PRECIPITATION WILL BEGIN TO MOVE INTO THE AREA LATE
TONIGHT...STARTING OFF AS BRIEF SNOW/SLEET FOR MANY LOCATIONS BUT
GRADUALLY CHANGING OVER TO FREEZING RAIN AS WARM AIR ALOFT BUILDS
NORTHWARD ALONG THE APPALACHIAN CHAIN.

A WINTRY MIXTURE WILL TRANSITION TO FREEZING RAIN AND RAIN
ON SUNDAY. AS TEMPERATURES WARM ABOVE FREEZING FROM SOUTH TO
NORTH DURING AFTERNOON SUNDAY...CAUSING ALL FREEZING
PRECIPITATION TO CHANGE OVER TO RAIN. MVFR/ IFR CEILINGS AND
REDUCTIONS IN VISIBILITY DUE TO PRECIPITATION ARE EXPECTED
AREAWIDE.

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


A SHARP COLD FRONT WILL CROSS THE AREA MONDAY AFTERNOON WITH
NORTHWEST WINDS INCREASING.

ON THE HEELS OF THE SUNDAY/MONDAY SYSTEM WILL BE YET ANOTHER
POTENTIALLY POTENT SYSTEM THAT MAY IMPACT ALL OR PARTS OF THE
REGION TUESDAY INTO WEDNESDAY WITH SUB-VFR DEVELOPING IN MOST
LOCATIONS LATER TUESDAY INTO WEDNESDAY.

&&

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

&&

$$
SYNOPSIS...DS/JH
NEAR TERM...JH/KK
SHORT TERM...MBS
LONG TERM...NF
AVIATION...JH/KK



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