Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 252013
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
313 PM EST SUN JAN 25 2015

.SYNOPSIS...
AN ALBERTA CLIPPER WILL APPROACH THE REGION FROM THE WEST BY EARLY
THIS EVENING...BEFORE MOVING ACROSS THE CENTRAL APPALACHIANS
OVERNIGHT INTO MONDAY. THIS SYSTEM WILL BRING PERIODS OF SNOW AND
RAIN TO MUCH OF THE REGION LATER TONIGHT INTO MONDAY. STRONG
NORTHWEST FLOW SHOULD FOLLOW THIS FEATURE MONDAY NIGHT INTO
TUESDAY BEFORE HIGH PRESSURE BUILDS IN FOR THE MIDDLE OF THE WEEK.
&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 230 PM EST SUNDAY...

CLIPPER SYSTEM REMAINS THE BIG CONCERN LATER TONIGHT INTO MONDAY AS IT
SLIDES EAST INTO SOUTHERN WEST VA LATE TONIGHT BEFORE JUMPING TO A NEW
COASTAL LOW NEAR CAPE HATTERAS EARLY MONDAY. MAIN PRECIP SHIELD WITH
THIS SYSTEM EARLY TONIGHT LOOKS TO REMAIN ALONG THE AXIS OF THE SURFACE
LOW AND ALONG A CONVEYOR BELT TO THE NORTH LATE CLOSER TO A SECONDARY
BOUNDARY OVER PENNSYLVANIA. HOWEVER AS THIS COLD POOL BEGINS TO CROSS
THE MOUNTAINS TOWARD MONDAY MORNING...MODELS SUGGEST AN ENHANCED AREA
OF LIFT IN THE WARM ADVECTION/DIFFLUENT AXIS JUST EAST OF THE SURFACE
LOW WHEN ENERGY TRANSFER BEGINS TO TAKE SHAPE. THIS POSSIBLE AREA OF
HEAVIER PRECIP OF CONCERN IN CAUSING ADDED COLUMN/BOUNDARY LAYER COOLING
WHICH COULD LEAD TO A FEW HOURS OF SNOW ESPCLY GREENBRIER EAST
ACROSS THE HIGHLANDS INTO THE SOUTHERN SHENANDOAH VALLEY LATE.
SINCE CONSENSUS OF MOST GUIDANCE SHOWS THIS AND HAVE TRENDED
COLDER...UPPING AMOUNTS FOR QUICK BURST OF WET SNOW BY DAYBREAK
MONDAY BUT TRICKY AS IF PRECIP IS LIGHTER THEN MAY ONLY BE RAIN
OUTSIDE THE HIGHEST ELEVATIONS. SINCE CORRIDOR LOOKS TO FOCUS
ALONG THE I-64 CORRIDOR AND RIGHT AROUND RUSH HOUR...PLAN TO HOIST
A WINTER WEATHER ADVISORY FOR A FEW COUNTIES ACROSS THE NORTH
OVERNIGHT INTO MIDDAY MONDAY FOR 1-4 INCHES OF WET SNOW. IF THINGS
ORGANIZE MORE THEN COULD SEE HEADLINES NEEDED FARTHER SOUTH INTO
CRAIG/BOTETOURT CTYS AND EAST TO AMHERST BUT TOO IFFY TO INCLUDE
FOR NOW.

ELSEWHERE...EXPECTING PERHAPS A MIX TO SNOW AT TIMES SOUTH INTO THE
ROANOKE/NEW RIVER VALLEYS AND POINTS WEST AFTER MIDNIGHT BUT WITH MUCH
LESS ACCUMULATION AT THIS POINT. MAY SEE AN INCH OR TWO NW NORTH
CAROLINA MOUNTAINS BUT STAYING BELOW ADVISORY LEVELS THERE. OTHERWISE
SHOULD BE MOSTLY RAIN FROM LYH TO BEDFORD TO MTV TO UKF AND POINTS EAST
THROUGH MORNING. HIGHEST CATEGORICAL POPS MAINLY ALONG/NORTH OF HIGHWAY
460 WITH LIKELYS CENTRAL SECTIONS AND OVERALL CHANCE COVERAGE SOUTH.
LOWS MOSTLY IN THE 30S EXCEPT CLOSER TO 30 HIGHER ELEVATIONS OVER THE
NORTH AND POSSIBLY STAYING AROUND 40 SOUTH WHERE CLOUDS MAY TEND TO
LOCK IN WARMTH FROM THIS AFTERNOON.

COASTAL LOW QUICKLY DEEPENS AND TAKES MUCH OF THE DEEPER MOISTURE
NORTH/EAST BY MIDDAY MONDAY WITH A QUICK PUNCH OF COLD ADVECTION
WRAPPING INTO THE WEST DURING THE AFTERNOON. GUIDANCE AGAIN SUGGESTING
THAT DURING THIS TRANSITION THAT RAIN/SNOW MAY STILL LINGER OVER THE
WEST UNDER THE PASSAGE OF THE 5H LOW DURING THE MORNING. THIS WOULD BE
ENOUGH ESPCLY GIVEN COOLING ALOFT OVERTOP THE ONSET OF LOW LEVEL COLD
ADVECTION TO PRODUCE ADDED SNOWFALL OVER THE NW BEFORE AFTERNOON DRYING
OCCURS AND SOME DEGREE OF UPSLOPE KICKS IN. HOWEVER STILL APPEARS MAY
BE ENOUGH MOISTURE EVEN IN THE EAST UNDER THE PHASING SYSTEM TO PRODUCE
CONTINUED SPOTTY -RA SO ALTHOUGH EXPECT POPS TO STEADILY DECREASE BY
AFTERNOON...LEAVING IN SOME LINGERING CHANCE COVERAGE WITH LOW LIKELYS
FAR WESTERN SLOPES. SURGE OF COLD AIR ALONG WITH DECENT PRESSURE RISES
SUGGESTS INCREASING NW WINDS DURING THE AFTERNOON WITH SPEEDS PERHAPS
JUST BELOW ADVISORY NW NORTH CAROLINA MOUNTAINS AND QUITE BLUSTERY
ELSEWHERE. KEPT HIGHS MOSTLY IN THE 30S NW TO 40-45 BLUE RIDGE AND
UPPER 40S SE PENDING THE DEGREE OF CLOUDS/PRECIP MONDAY AFTERNOON.
&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 200 PM EST SUNDAY...

MONDAY NIGHT THROUGH TUESDAY...THE AXIS OF THE UPPER TROUGH WILL
CONTINUE TO SHIFT EAST OF THE REGION WITH NORTHWEST FLOW CONTINUING
ACROSS THE AREA. EMBEDDED WITHIN THAT FLOW WILL BE RESIDUAL MOISTURE
WITH AT LEAST LAKE ERIE ORIGINS...AND PERHAPS LAKE MICHIGAN. EXPECT
TO SEE A UPSLOPE SNOW SHOWERS ACROSS THE PREFERRED AREAS OF
SOUTHEAST WEST VIRGINIA...SOUTH INTO THE NORTHERN MOUNTAINS OF NORTH
CAROLINA. ADDITIONAL SNOWFALL TOTALS WILL BE GREATEST ACROSS WESTERN
GREENBRIER COUNTY WHERE TWO TO THREE MORE INCHES ARE POSSIBLE.
ELSEWHERE...WHERE MEASURABLE SNOW OCCURS...AMOUNTS WILL BE GENERALLY
BE LESS THAN AN INCH. RESIDUAL ISOLATED...LIGHT SNOW SHOWERS WILL
CONTINUE ACROSS WESTERN GREENBRIER COUNTY THROUGH TUESDAY EVENING
WITH LITTLE ADDITIONAL ACCUMULATION. ACROSS THE FAR NORTHEAST AND
EASTERN PORTIONS OF THE AREA...RESIDUAL LIGHT SNOW WILL BE POSSIBLE
MONDAY NIGHT ON THE BACKSIDE OF THE DEPARTING UPPER TROUGH. NO
MEASURABLE SNOWFALL IS EXPECTED. THE AFOREMENTIONED NORTHWEST WINDS
WILL BE ON THE GUSTY SIDE. THE HIGHER ELEVATIONS WILL EXPERIENCE
GUSTS IN THE 30 TO 40 MPH RANGE MONDAY NIGHT WITH SLIGHTLY SLOWER
GUSTS THROUGHOUT THE DAY TUESDAY.

LATE TUESDAY NIGHT THROUGH WEDNESDAY...SURFACE HIGH PRESSURE BUILDS
INTO THE AREA. THE CENTER OF THE HIGH SHIFTS TO THE EAST WEDNESDAY
NIGHT AND ALLOWS SURFACE WINDS TO TURN SOUTHWEST. NO PRECIPITATION
IS FORECAST...BUT CLOUDS WILL BE ON THE INCREASE WEDNESDAY NIGHT IN
ADVANCE OUR NEXT GREAT LAKES CLIPPER SYSTEM.

TEMPERATURES DURING THIS PORTION OF THE FORECAST PERIOD WILL TREND
FROM BEING A LITTLE BELOW NORMAL TO NEAR OR SLIGHT ABOVE NORMAL.
&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 230 PM EST SATURDAY...

UPPER LEVEL PATTERN WILL BE GOING BACK TO SPLIT FLOW FOR THE
EXTENDED WITH A CUTOFF LOW OVER THE BAJA PENINSULA DOMINATING THE
SOUTHERN STREAM...AND A WESTERN RIDGE/EASTERN TROF FOR THE NORTHERN
STREAM. GFS IS LESS AMPLIFIED WITH THE NORTHERN STREAM WHICH GIVES
IT A WARMER LOOK THAN THE ECMWF.

WE WILL SEE A NORTHERN STREAM LOW MOVE BY TO OUR NORTH ON THURSDAY
WHICH WILL BRING US A CHANCE OF LIGHT SYNOPTIC PRECIPITATION WHICH
LOOKS TO BE MIX TO RAIN FOR THURSDAY. THIS SYSTEM WILL THEN SWING A
COLD FRONT THROUGH THE REGION THURSDAY EVENING WHICH SETS THE STAGE
FOR UPSLOPE SNOW SHOWERS THURSDAY NIGHT INTO FRIDAY. THE WINDS
BEHIND THE COLD FRONT LOOK QUITE BLUSTERY RIGHT THROUGH FRIDAY.

HIGH PRESSURE THEN BUILDS OVER THE MID ATLANTIC REGION AND FORMS A
BIT OF A WEDGE WITH QUIET WEATHER FOR FOR SATURDAY. EURO WANTS TO
BRING A SURGE OF ARCTIC AIR INTO THE REGION AS WE HEAD INTO SUNDAY.
GFS IS NOT ON BOARD WITH THIS AND ENSEMBLES WERE NOT INDICATING A
MAJOR ARCTIC OUTBREAK. WILL BE LEANING MORE TOWARD THE GFS/ENSEMBLE
SOLUTION AND KEEP TEMPS SUNDAY INTO SUNDAY NIGHT A GOOD 20F WARMER
THAN THE ECMWF.
&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
AS OF 1205 PM EST SUNDAY...

OVERALL CONTINUED VFR THIS AFTERNOON WITH MAINLY PASSING MID AND
HIGH CLOUD CANOPY UNTIL LATE WHEN SOME LOWER VFR CIGS MAY ARRIVE
ACROSS THE FAR WESTERN SITES. STEADY SOUTHWEST WINDS SHOULD REMAIN
IN THE 7-15 KNOT RANGE BEFORE DIMINISHING THIS EVENING. CIGS
SHOULD THEN QUICKLY LOWER TO MVFR IN LIGHT RAIN AHEAD OF THE
CLIPPER SYSTEM...STARTING AT WESTERN SITES BY 03Z/10PM...AND
AFTER 06Z/1AM EASTERN SITES. THE LOWER LEVEL SOUTHERLY FLOW
SHOULD HELP LOWER CEILINGS MAY RESULT IN WIDESPREAD IFR TO LIFR
CONDITIONS BEFORE DAYBREAK...BUT PRECIPITATION SHOULD REMAIN
RATHER LIGHT. AT KBLF AND KLWB THERE MAY BE SNOW MIXED IN AT
TIMES...AND EVEN MAY START BRIEFING AS SNOW...AND THEN CLOSER TO
DAWN MONDAY MAY SWITCH OVER TO ALL SNOW ESPCLY AT KLWB AS MODEL
CONTINUE TO TREND COLDER MAKER FOR A BIT HIGHER CONFIDENCE OF MORE
SNOW AT KWLB WHERE SOME ACCUMULATION POSSIBLE BY EARLY MONDAY.

MONDAY...EXPECT MVFR TO IFR CEILINGS AND VISIBILITIES TO PERSIST WITH
THE CLIPPER AND THE ASSOCIATED LIGHT RAIN/SNOW. FLOW TURNS MORE
WESTERLY BY MIDDAY AND COLDER AIR FILTER IN BEHIND SURFACE
FRONT...AND RAIN OR RAIN SHOWERS WILL CHANGE OVER TO SNOW AT KBLF
WHILE REMAINING MOSTLY SNOW AT KLWB...AND INTERMITTENT SNOW
SHOWERS AT KBCB...PERHAPS KROA AS WELL. LATE MONDAY AND MONDAY
NIGHT SOME ADDED VERY LIGHT ACCUMULATIONS OF SNOW ARE MORE LIKELY
AT KBLF/KLWB WITH NW WINDS INCREASING ACROSS THE REGION AS WELL.
MVFR TO VFR CONDITIONS SHOULD RETURN AT KROA...KLYH AND KDAN
DURING THE DAY MONDAY.

TUESDAY...A REINFORCING SHOT OF ENERGY COMES IN THROUGH THE
NORTHWEST UPPER FLOW. HIGH CONFIDENCE FOR MVFR CONDITIONS IN THE
MOUNTAINS BOTH MONDAY AND TUESDAY WITH OCNL IFR DUE TO SCATTERED
SNOW SHOWERS. LOWER CONFIDENCE THE MVFR CIGS WILL SPILL OVER THE
MOUNTAINS INTO THE ROANOKE VALLEY AND SOUTHSIDE VIRGINIA.

BY MONDAY NIGHT...ANY PTYPE WILL BE SNOW DUE TO COLDER
TEMPERATURES. WINDS WILL ALSO BE GUSTY MONDAY NIGHT AND TUESDAY
BEHIND THE REINFORCING SURGE OF COLD AIR.

BY WEDNESDAY...HIGH PRESSURE WILL PROVIDE A DAY OF TRANQUIL
WEATHER AND REGION-WIDE VFR CONDITIONS BEFORE ANOTHER CLIPPER
ARRIVES THURSDAY AFTERNOON WITH POSSIBLE ADDED SUB-VFR IN LIGHT
PRECIPITATION.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO NOON EST
     MONDAY FOR VAZ019-020-024.
NC...NONE.
WV...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO NOON EST
     MONDAY FOR WVZ507-508.

&&

$$
SYNOPSIS...JH
NEAR TERM...JH
SHORT TERM...DS
LONG TERM...MBS
AVIATION...AMS/JH/PM/SK



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