Area Forecast Discussion
Issued by NWS Charleston, WV

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614
FXUS61 KRLX 090011
AFDRLX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
711 PM EST MON FEB 8 2016

.SYNOPSIS...
ARCTIC FRONT CROSSES TONIGHT. UNSETTLED/COLDER IN ITS WAKE TUESDAY
AND WEDNESDAY UNDER LARGE MID/UPPER LEVEL LOW...WITH ROUNDS OF
SNOW SHOWERS THAT LINGER THROUGH MUCH OF THE WEEK.

&&

.NEAR TERM /THROUGH TUESDAY/...MESOSCALE UPDATE...
700 PM UPDATE...

TRACKING A POTENT LINE OF SQUALLS MOVING THRU SE OH AND INTO N WV
AT THIS HR. EXPECT BRIEF WHITEOUT CONDITIONS AND GUSTY WINDS AS
THIS MOVES THRU. THIS HAS HAD A HISTORY OF PUTTING DOWN A SLUSHY
HALF INCH TO INCH WITH EVEN SOME EMBEDDED LIGTHNING OBSERVED. THE
TEMP HERE AT THE OFFICE DROPPED FROM 42 TO 33 IN 15 MINUTES TIME
AS THE SQUALL WENT THRU AS HAS HELD NEARLY STEADY SINCE.

QUICK ON ITS HEELS IS ANOTHER POTENT LINE OF SQUALLS MOVING THRU E
KY ATTM. THIS WILL TRACK INTO THE AREA AS THE EVENING PROGRESSES
WITH AGAIN BRIEF WHITEOUT CONDITIONS. BEHIND THAT WE WAIT FOR THE
TRUE CAA TO BE USHERED IN BY A POTENT S/W TROF AND FRONT AFTER
MIDNIGHT.

HAVE REWORKED HOURLY GRIDS INCLUDING POP/TEMP/WX TO REFLECT RADAR
TRENDS. ACCUMULATIONS WERE REWORKED TO ACCOUNT FOR THE CURRENT
SQUALL MOVING THRU AS WELL AS OVERNIGHT PERIOD USING LATEST
NAM/HRRR/GFS. AM CONCERNED AMOUNTS MAY STILL BE TOO LOW OVER
PORTIONS OF SE OH AND N WV LOWLANDS THRU TOMORROW GIVEN AN
EMERGING CONSENSUS ON THE PROLONGED LOCATION OF BETTER FORCING.
WILL WAIT FOR 00Z NEAR TERM MODELS TO ROLL IN BEFORE MAKING ANY
MEANINGFUL CHANGES TO ACCUMULATIONS FOR THOSE AREAS.

PREVIOUS DISCUSSION BELOW...

OTHER THAN ADJUSTING THE TIME PERIODS FOR THE CHANGE TO ALL SNOW
SHOWERS IN THE LOW LANDS TONIGHT...AND THE MOST LIKELY TIME PERIODS
THEREAFTER FOR SNOW SHOWERS AND THUS ACCUMULATIONS...NOT TOO MUCH
CHANGE FROM PREVIOUS FORECAST WHEN IT COMES TO FINAL SNOW
ACCUMULATIONS THROUGH THE DAY TUESDAY. ONE THING IS TO SLOW THE
ARCTIC FRONT TONIGHT JUST A BIT PER MODEL CONSENSUS. AHEAD OF THIS
FRONT...LOW LEVEL SOUTHWESTERLY FLOW AND EVEN PEEKS OF SUNSHINE HAVE
ALLOWED TEMPERATURES TO REACH THE 40S IN MANY LOW LAND SPOTS...BUT
WITH AIR ALOFT QUITE COLD...STILL WET SNOW OUTSIDE THE MOUNTAINS MAY
BE MIXED IN WITH THE RAIN SHOWERS THIS AFTERNOON...AND IN THE
MOUNTAINS MAINLY SNOW SHOWERS. NEVERTHELESS...SNOW ACCUMULATIONS
THIS AFTERNOON AND EVENING MAINLY CONFINED TO THE HIGHER ELEVATIONS
OF THE MOUNTAINS. FOR TONIGHT...HAVE MINOR SNOW ACCUMULATIONS IN THE
LOW LANDS GIVEN THE DELAY OF THE COLDER AIR AND NIGHT TIME LOWS NOT
THAT FAR BELOW FREEZING...GENERALLY AROUND AN INCH OR SO...WITH 1 TO
4 INCHES IN THE MOUNTAINS. FOR TUESDAY...POST FRONTAL SNOW SHOWERS
WIDESPREAD WITH UPPER DISTURBANCES ROTATING AROUND THE MEAN UPPER
TROUGH TO OUR WEST. MODELS INDICATE THAT THE NORTHERN PORTIONS OF
THE AREA WILL THE MAIN TARGET FOR THE HIGHEST AMOUNTS...ESPECIALLY
NORTHERN MOUNTAINS...WHERE DAY TIME ACCUMULATIONS WILL RANGE FROM 1
TO 2INCHES LOW LANDS TO 2 TO 4 INCHES NORTHERN MOUNTAINS. THIS WILL
MAINLY BE IN THE MORNING BEFORE THE STRENGTHENING FEBRUARY SUN TAKES
EFFECT. LOOK FOR HIGHS TUESDAY TO STAY BELOW FREEZING.1015 AM UPDATE.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
LARGE L/W UPPER LEVEL TROUGH OVER THE AREA TUE NT AND
WED...STARTS TO LIFT OUT OF THE AREA WED NT AND THU.

ONE IN A SERIES OF VORT LOBES ROTATING AROUND THE BASE OF THE
TROUGH WILL BE EXITING TUE NT...AND A MORE W THAN NW LOW LEVEL
FLOW WILL KEEP THE LAKE MI PLUME N OF THE FCST AREA. THIS MAY
RESULT IN A LULL IN SNOW SHOWERS OVER THE MIDDLE OHO VALLEY.

NEXT S/W IS PROGGED TO BE NEGATIVELY TILTED AND ESSENTIALLY BECOME
THE MAIN L/W TROUGH AXIS AS IT CROSSES THE FCST AREA WED INTO WED
NT. WITH DIURNAL HEATING...SNOW SHOWERS APPEAR LIKELY THROUGHOUT
MUCH OF THE FCST AREA WED. AS THE LOW LEVEL FLOW VEERS A BIT MORE
TO THE NW LATE WED INTO WED NT...THE LAKE MI PLUME MAY EASE BACK
SWD INTO NRN PORTIONS OF THE FCST AREA...BEFORE THE ENTIRE PATTERN
STARTS TO DRY OUT WED NT AND THU...AS UPPER HEIGHTS START TO RISE
AND THE H85 COLD TROUGH STARTS TO LIFT OUT.

THERE ARE LIKELY TO BE ADDITIONAL FINER DETAILS IN THE MIX AS
THIS ALL PLAYS OUT...BUT UPSLOPE SNOW SHOWERS IN AND NEAR THE
MOUNTAINS WILL BE ESSENTIALLY ONGOING WELL INTO WED NT BEFORE
STARTING TO TAPER OFF.

STILL FIGURING ON AN INCH OR TWO PER 12 HOUR PERIOD FOR THE
LOWLANDS AND 2 TO 3 IN THE MOUNTAINS TUE NT...GRADUALLY WANING
THEREAFTER. WITH 24 HOUR SNOW AMOUNTS STILL WELL BELOW WARNING
CRITERIA...THE AREA WIDE ADVISORY LOOKS GOOD THOUGH COULD SEE
HAVING TO EVENTUALLY EXTEND IT IN THE MOUNTAINS THROUGH AT LEAST
WED. THAT WILL LIKELY BE A CASE OF DWINDLING AMOUNTS IN A
CONTINUATION OF THE EXISTING ENCROACHMENT.

NO MAJOR CHANGES TO TEMPERATURES IN THIS BELOW NORMAL
PATTERN...BLENDED IN BIAS CORRECTED GUIDANCE FOR LOWS AND BLENDED
IN RAW NAM OUTPUT FOR HIGHS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
SOME LINGERING SNOW SHOWERS ACROSS THE NORTHERN MOUNTAINOUS COUNTIES
TO START THE PERIOD. THIS IS DUE TO NW FLOW ALOFT. HOWEVER...A
SURFACE HIGH PRESSURE IS NOSING IN SO IT WILL BE A TIGHTROPE WALK
BETWEEN NORTHWEST FLOW AND DEPARTING MOISTURE. SOME UNCERTAINTY ON
POPS THIS WEEKEND...AS ECMWF SLIDES A SURFACE LOW TO OUR NORTH
DRIVING A COLD FRONT THROUGH. HOWEVER...THE GFS IS MUSH LESS ROBUST
WITH THIS SYSTEM...WITH A WEAKER FRONT AND LESS MOISTURE. STAYED IN
CHANCE POPS FOR NOW.

EITHER WAY...REINFORCING SHOT OF COLD AIR ARRIVES WITH THIS FRONT
SETTING UP A VERY CHILLY WEEKEND. STILL BREEZY DURING THIS TIME AS
THE NEXT HIGH PRESSURE DOES NOT NOSE IN UNTIL DURING THE DAY SUNDAY.
WILL MENTION POTENTIAL FOR WIND CHILL ADVISORY IN THE HWO. MOST
WIDESPREAD ISSUE LOOKS TO BE SATURDAY NIGHT...BUT SHOULD HIGH ARRIVE
SOONER THAN FORECAST...WIND COULD SHUT DOWN EARLY.

ANOTHER SYSTEM LOOKS TO IMPACT THE END OF THE PERIOD...BUT WITH
FAIRLY DRASTIC DIFFERENCES IN THE MODELS STUCK CLOSE TO WPC FOR NOW.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
A SOMEWHAT LOW CONFIDENCE AVIATION FORECAST THRU THE VALID TAF
PERIOD.

A POTENT SQUALL WILL MOVE OVER THE N TAF SITES THRU 02Z WITH BRIEF
WHITEOUT CONDITIONS CORRESPONDING TO IFR CIGS/LIFR VSBY ALONG WITH
GUSTY WINDS 25 TO 30 KTS. ANOTHER SQUALL WILL MOVE INTO THE AREA
FROM THE W THIS EVENING WITH YET ANOTHER LOWERING OF CONDITIONS
BACK INTO IFR CIGS/LIFR VSBY FOR A TIME. OUTSIDE OF THOSE
BANDS...MAINLY MVFR AND VFR CIGS/VSBY.

THE ACTUAL COLD FRONT AND ASSOCIATED S/W TROF WILL SWING THRU
GENERALLY AFTER 06Z WITH GUSTY WINDS AND PERHAPS ANOTHER SQUALL.
BEHIND THAT THE COVERAGE IN SHSN WILL INCREASE ESPECIALLY OVER SE
OH AND N WV WHERE A PROLONGED IFR OR WORSE SET UP IS ENVISIONED
THRU TUE AFTERNOON. ELSEWHERE...SOME IFR CONDITIONS IN SCT SHSN
FOR S TERMINALS BEHIND THE FRONT WILL CARRY THRU TUE MORNING WITH
PERHAPS MORE OF A MVFR/IFR SHSN REGIME TAKING HOLD.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z WEDNESDAY...

FORECAST CONFIDENCE...LOW

ALTERNATE SCENARIOS: TIMING AND EXTENT OF IFR WILL VARY IN SNOW
SHOWERS OVERNIGHT AND ESPECIALLY ON TUE.

EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH:   TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW:    TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.

DATE                                                                 TUE
UTC 1HRLY       00   01   02   03   04   05   06   07   08   09   10   11
EST 1HRLY       19   20   21   22   23   00   01   02   03   04   05   06
CRW CONSISTENCY  H    M    M    M    M    M    M    L    L    L    L    L
HTS CONSISTENCY  M    M    M    M    L    L    L    L    M    M    M    M
BKW CONSISTENCY  M    H    H    H    H    M    M    M    L    L    L    L
EKN CONSISTENCY  M    L    M    H    H    M    M    L    L    L    L    L
PKB CONSISTENCY  M    M    H    H    H    H    M    M    L    L    L    L
CKB CONSISTENCY  M    L    M    M    M    M    M    M    L    L    L    L

AFTER 00Z WEDNESDAY...
PERIODS OF IFR CONDITIONS IN SNOW SHOWERS ALL THE WAY THROUGH
WEDNESDAY NIGHT...ESPECIALLY NORTH AND EAST PORTIONS OF AREA.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WINTER WEATHER ADVISORY UNTIL 7 AM EST WEDNESDAY FOR
     WVZ005>011-013>020-024>040.
     WINTER WEATHER ADVISORY UNTIL 7 AM EST WEDNESDAY FOR WVZ046-
     047.
OH...WINTER WEATHER ADVISORY UNTIL 7 AM EST WEDNESDAY FOR OHZ066-
     067-075-076-083>087.
KY...WINTER WEATHER ADVISORY UNTIL 7 AM EST WEDNESDAY FOR
     KYZ101>103-105.
VA...WINTER WEATHER ADVISORY UNTIL 7 AM EST WEDNESDAY FOR VAZ003-
     004.

&&

$$
SYNOPSIS...TRM/JMV/MZ
NEAR TERM...JMV/30
SHORT TERM...TRM
LONG TERM...MZ
AVIATION...30



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