Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 081219
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
719 AM EST MON FEB 8 2016

.SYNOPSIS...
A STRONG CYCLONE IN THE UPPER LEVELS OF THE ATMOSPHERE WILL SINK
SOUTH ACROSS THE GREAT LAKES AND INTO THE OHIO VALLEY TODAY. THE
AREA OF LOW PRESSURE WILL CUTOFF AND REMAIN NEARLY STATIONARY FOR
THE NEXT THREE DAYS...TEMPERATURES FALLING AFTER TODAY AND
REMAINING BELOW FREEZING THROUGH MUCH OF THE UPCOMING WEEK. THE
LEADING EDGE OF THIS AIRMASS WILL ARRIVE IN THE FORM OF A COLD
FRONT...THIS FRONT CROSSING THE MOUNTAINS THIS AFTERNOON...
ASSOCIATED WITH RAIN AND SNOW SHOWERS. THE COLDEST OF THE AIR WILL
NOT ARRIVE UNTIL TUESDAY. WEAK UPPER LEVEL IMPULSES WILL MOVE
ACROSS THE MOUNTAINS DURING THE WEEK RESULTING IN A PROLONGED
SNOW SHOWER EVENT ESPECIALLY OVER THE MOUNTAINS THROUGH MIDWEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 445 AM EST MONDAY...

COLD ARCTIC LOW...SURFACE AND ALOFT...WAS CENTERED OVER
WISCONSIN. TWO FRONTS TRAILED SOUTH FROM THE LOW. THE FIRST
EXTENDED FROM MICHIGAN SOUTH THROUGH OHIO AND INTO CENTRAL KY/TN.
THIS FIRST FRONT WAS ASSOCIATED WITH AN AREA OF RAIN...
TEMPERATURES JUST AHEAD OF THE FRONT IN THE 40S...AND 30S JUST
BEHIND THE FRONT. THE SECOND FRONT EXTENDED FROM WISCONSIN SOUTH
THROUGH IOWA AND INTO THE CENTRAL PLAINS. THIS FRONT WAS THE
LEADING EDGE OF THE ARCTIC BITTER COLD WITH TEMPERATURES BEHIND
THIS FRONT IN THE SINGLE DIGITS AND TEENS.

THE FIRST FRONT IS PROGGED TO CROSS OUR FORECAST AREA TODAY...
ARRIVING IN OUR FAR WESTERN COUNTIES NEAR THE APPALACHIAN DIVIDE
TOWARD NOON...THEN MOVING EAST OF THE MOUNTAINS THIS
AFTERNOON...CROSSING THE PIEDMONT THIS EVENING. IN SPITE OF
TEMPERATURES IN THE 20S ACROSS THE CWA EARLY THIS MORNING...WARM
AIR ADVECTION AHEAD OF THE FRONT SHOULD ALLOW TEMPERATURES TO RISE
ABOVE FREEZING...REACHING THE UPPER 30S TO NEAR 40 IN THE
MOUNTAINS...AND UPPER 40S TO NEAR 50 IN THE PIEDMONT. WITH
TEMPERATURES THIS WARM...EXPECTING ANY PRECIPITATION ASSOCIATED
WITH THE FRONT TO FALL AS A MIX OF RAIN/SNOW IN THE MOUNTAINS...
AND ALL RAIN EAST OF THE BLUE RIDGE.

WILL MAINTAIN THE EXISTING WINTER WEATHER ADVISORY FOR OUR FAR
WESTERN COUNTIES WHERE 1 TO 2 INCHES OF SNOW IS POSSIBLE TODAY.
NOT OVERLY CONFIDENT ON THE ACCUMULATION SINCE IT WILL DEPEND ON
WHETHER EVAPORATIONAL COOLING CAN MAINTAIN A P-TYPE OF ALL SNOW.
HIGHEST ELEVATIONS WILL HAVE THE BEST CHANCE TO REMAIN ALL
SNOW. LOWER ELEVATIONS WILL NOT. TOTAL MODEL QPF IN LIQUID
EQUIVALENT FORM IS 0.1 TO 0.2 INCHES.

ITS NOT IN THE FORECAST ATTM...BUT SOMETHING TO WATCH OUT FOR IS
THE POTENTIAL FOR ISOLD THUNDER. WITH TEMPERATURES RISING INTO THE
40S IN THE BOUNDARY LAYER...THIS MAY CREATE JUST ENOUGH
INSTABILITY TO DRIVE A LINE OF DEEPER CONVECTION RIGHT ALONG THE
FRONT. FALLING HEIGHTS AND STEEPENING LAPSE RATES ALONG THE
LEADING EDGE OF THE UPPER TROF MAY DRIVE SOMETHING MORE ROBUST
THIS AFTERNOON. IF THIS OCCURS THEN COLDER AIR WITHIN THE
DOWNDRAFTS COULD DRIVE HEAVIER RAIN/SNOW RATES THAN WHAT IS
CURRENTLY FORECAST.

BY TONIGHT THE FIRST FRONT WILL BE MAKING ITS WAY ACROSS THE
PIEDMONT AND HEADED FOR THE COAST. COLD AIR ADVECTION WILL BE
DRAWING DOWN THE TEMPERATURE WITH ANY LINGERING MOISTURE CHANGING
OVER TO SNOW SHOWERS. ARRIVAL OF THE SECOND FRONT LATE TONIGHT
INTO TUESDAY WILL THEN BRING ONSET OF A MUCH COLDER AIRMASS AND AN
OPPORTUNITY FOR STEADIER HEAVIER SNOW SHOWER ACTIVITY FOR THE
MOUNTAINS.

WILL MAINTAIN WINTER STORM WATCH FOR WESTERN COUNTIES BEGINNING
TONIGHT AND CONTINUING INTO MID WEEK. WILL FINE TUNE THIS HEADLINE
ONCE WE GET PAST TODAYS PRECIPITATION EPISODE. THERE SHOULD BE A
PHYSICAL BREAK BETWEEN THE PRECIP THAT OCCURS TODAY VERSUS THE
SNOW SHOWER ACTIVITY TONIGHT WHICH WILL THEN PERSIST INTO MID
WEEK.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 400 AM EST MONDAY...

UPPER TROUGH WILL SLOWLY SLIDE EAST ACROSS OUR AREA TUESDAY INTO
WEDNESDAY NIGHT. SEVERAL SHORTWAVES WILL ROTATE AROUND THE UPPER
TROUGH DURING THE PERIOD. THE NAM...GFS AND ECMWF SHOWED A HEALTHY
SHORTWAVE IN THE MOUNTAINS TUESDAY MORNING WHICH PIVOTS EAST TUESDAY
NIGHT INTO WEDNESDAY. PERSISTENT NORTHWEST WINDS FROM THE SURFACE
THROUGH AROUND 700 MB...WILL RESULT IN SNOW SHOWERS AND SNOW
FLURRIES. THE CHALLENGE IN THE FORECAST IS WHEN AND HOW FAR EAST
BANDS OF SNOW SHOWERS PUSH. WITH GOOD COLD AIR ADVECTION AND
FORECAST SOUNDINGS SHOWING PRIME ICE CRYSTAL GROWTH...WILL
SPREAD THE CHANCE OF SNOW SHOWERS AND FLURRIES FURTHER EAST TUESDAY
INTO THE PIEDMONT. HIGH TEMPERATURES ON TUESDAY WILL RANGE FROM
AROUND 20 IN THE MOUNTAINS TO AROUND 40 IN THE PIEDMONT. WITH THE
SHORTWAVE ROLLING EAST TUESDAY NIGHT...KEPT THE SNOW SHOWERS AND
SNOW FLURRIES CONTINUING. LOW TEMPERATURES WILL RANGE FROM AROUND 10
DEGREES IN THE NORTHWEST MOUNTAINS TO THE MID 20S IN THE PIEDMONT.
ENOUGH COLD AIR...COMBINED WITH MODERATE WINDS...WILL RESULT IN COLD
WIND CHILL VALUES. IN THE MOUNTAINS...IT WILL BE COLD ENOUGH FOR
WIND CHILL ADVISORIES TUESDAY NIGHT INTO WEDNESDAY MORNING.
FOR TUESDAY INTO TUESDAY NIGHT...SNOW ACCUMULATIONS WILL VARY FROM A
COATING TO CLOSE TO 3 INCHES IN THE WESTERN MOUNTAINS.

DEEPER MOISTURE WILL ERODE FROM SOUTH TO NORTH ON WEDNESDAY AND
WEDNESDAY NIGHT...WITH THE SNOW SHOWERS ENDING FIRST IN THE
NORTHWEST NORTH CAROLINA MOUNTAINS AND EVENTUALLY IN SOUTHEAST WEST
VIRGINIA ON THURSDAY. HIGHEST SNOW AMOUNTS AROUND A COUPLE OF INCHES
WILL BE ON THE HIGHER WEST FACING SLOPES AND COLDEST WIND CHILLS
WILL BE AT HIGHER ELEVATIONS WEDNESDAY NIGHT. HIGH TEMPERATURES
WEDNESDAY WILL VARY FROM THE MID TEENS IN THE MOUNTAINS TO THE MID
30S IN THE PIEDMONT. LOW TEMPERATURES WEDNESDAY NIGHT WILL VARY FROM
THE SINGLE DIGITS IN THE MOUNTAINS TO THE TEENS IN THE PIEDMONT.
THE COMBINATION OF WIND AND TEMPERATURES WILL CREATE WIND CHILLS
BELOW ZERO IN THE MOUNTAINS WEDNESDAY NIGHT INTO THURSDAY MORNING.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 250 PM EST SUNDAY...

CLOSED 500 MB LOW REMAINS OVER SOUTHEAST CANADA BUT HEIGHTS RISE
OVER THE REGION. LONG WAVE TROUGH REMAINS OVER THE EAST THROUGH
SUNDAY WITH MODELS SHOWING DIFFERENCE IN TIMING AND INTENSITY OF
SHORT WAVES EMBEDDED WITHIN THE TROUGH.

SURFACE HIGH PRESSURE WILL BE CENTERED OVER THE FORECAST AREA ON
FRIDAY MORNING. MORE ARCTIC AIR COMES IN SATURDAY AND SUNDAY. BOTH
GFS AND ECMWF ARE SHOWING VARIATIONS OF A 1040 MB HIGH BUILDING WELL
INTO THE OHIO VALLEY AND MID ATLANTIC REGION DURING THAT TIME FRAME.

SNOW SHOWERS WILL BE ENDING IN THE NORTHWEST COUNTY WARNING AREA.
WILL HAVE A LOW PROBABILITY OF SNOW IN THE FORECAST FOR FRIDAY OR
SATURDAY THAT IS ASSOCIATION WITH A SOMEWHAT STRONGER SHORT WAVE
TRACKING THROUGH THE BASE OF THE UPPER TROF. BUT AT THAT TIME
FRAME...LOCATION AND TIMING ARE LIKELY TO CHANGE.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
AS OF 700 AM EST MONDAY...

DEEP UPPER LOW SAGGING SOUTHWARD THROUGH THE GREAT LAKES WILL
BRING INCREASING CLOUDS TO THE CENTRAL APPALACHIANS.


CLOUD BASES WILL BEGIN TO LOWER INTO THE MVFR CATEGORY IN THE
14Z-18Z TIME FRAME ASSOCIATED WITH LIGHT RAIN/SNOW. THIS
PRECIPITATION IS ASSOCIATED WITH BAND OF STRONGER DYNAMIC FORCING
AND INITIAL FRONTAL BOUNDARY. ALTHOUGH THIS INITIAL BAND OF
PRECIPITATION WILL SPREAD INTO THE PIEDMONT...TEMP PROFILES
SUGGEST THAT IT MAY LARGELY BE RAIN IN THOSE AREAS. HAVE CARRIED
ONLY -RA FOR KDAN AND KLYH...WITH A -RASN MIX KROA...WITH LOW
CONFIDENCE IN SNOW THERE. THE HIGHER ELEVATIONS ACROSS THE
MOUNTAINS SHOULD SEE MOSTLY SNOW WITH SOME LIGHT ACCUMULATIONS.

THE INITIAL BAND OF FRONTAL FORCED PRECIPITATION SHOULD MOVE EAST
OF THE CWA BY MID AFTERNOON. AT THAT POINT...AND WITH COLDER
ARCTIC AIR BEGINNING TO FILTER INTO THE REGION FROM THE
WEST...PRECIPITATION SHOULD GENERALLY END EAST OF THE BLUE RIDGE
EXCEPT FOR A FEW FLURRIES LATER IN THE EVENING...BUT -SHSN SHOULD
COMMENCE IN EARNEST ACROSS THE ALLEGHANYS WITH MVFR CIGS LOWERING
TO IFR.

WINDS WILL REMAIN LIGHT...LESS THAN 6KT AHEAD OF THE APPROACHING
FRONT...THEN BECOME WESTERLY AND INCREASE IN MAGNITUDE AFTER
FROPA.

EXTENDED DISCUSSION...

SUB-VFR SHOULD BECOME MORE CONFINED TO THE MOUNTAINS AND WESTERN
SLOPES TONIGHT INTO MIDWEEK WITH PROLONGED MVFR/IFR CONDITIONS AT
KBLF/KLWB IN SNOW SHOWERS THROUGH AT LEAST WEDNESDAY NIGHT AS
ARCTIC AIR ARRIVES. POTENTIAL ALSO FOR PERIODS OF MVFR AT
KBCB/KROA AS IMPULSES ROTATE ACROSS THE MOUNTAINS AND BANDS
OF SNOW DEVELOP DURING THE OVERNIGHT HOURS. ACCUMULATING SNOW IS
LIKELY IN THE MOUNTAINS WEST OF THE BLUE RIDGE. FLURRIES MAY ALSO
OCCUR AS FAR EAST AS THE PIEDMONT WHERE INTERVALS OF VFR TO MVFR
CIGS COULD ALSO OCCUR.

CONDITIONS SHOULD BRIEFLY RETURN TO MAINLY VFR THURSDAY/THURSDAY
NIGHT AS WEAK HIGH PRESSURE BUILDS IN AND MOISTURE DECREASES.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WINTER STORM WATCH FROM 6 PM EST THIS EVENING THROUGH THURSDAY
     MORNING FOR VAZ007-009>012-015-019-020.
     WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR VAZ007-
     009-015.
NC...WINTER STORM WATCH FROM 6 PM EST THIS EVENING THROUGH THURSDAY
     MORNING FOR NCZ001-018.
     WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR NCZ001-
     018.
WV...WINTER STORM WATCH FROM 6 PM EST THIS EVENING THROUGH THURSDAY
     MORNING FOR WVZ042>044-507-508.
     WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR WVZ042-
     043-508.

&&

$$
SYNOPSIS...PM
NEAR TERM...PM
SHORT TERM...KK
LONG TERM...AMS
AVIATION...PM


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