Area Forecast Discussion
Issued by NWS Charleston, WV

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740
FXUS61 KRLX 121117
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
617 AM EST Tue Dec 12 2017

.SYNOPSIS...
Strong upper trough brings cold air and snow showers today.
Another system arrives by late week with another chance for snow
showers.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 415 AM Tuesday...

As of 09Z, the cold front was almost through the area and will
likely be east of the mountains by daybreak. Looking at upstream
observations early this morning, the cold air is rushing in very
quickly behind the front as previously forecast. High
temperatures for the day have been hit already this morning and
we can expect our temperatures to now continue to drop through
the day today. Radar is not showing much now, but there have
been a few flakes falling at Snowshoe with the front approaching,
and we can expect snow showers to become more widespread in the
mountains in the NW upslope flow after the front passes.

Elsewhere, snow showers/squalls will become more widespread by
later this morning to early this afternoon as deep upper trough
sinks southward over the area. Decent fetch across Lake Michigan
with the NW flow will advect lake moisture to the SE. Current
forecast soundings this afternoon indicate a fairly saturated
dendritic growth zone, and lapse rates become quite steep this
afternoon...not surprising with an 18 decimeters h500 fall from
this morning through this afternoon with the negatively tilted
upper trough.

As mentioned in the previous forecast, expecting to see areas
of lake streamers set up and bring short/intense periods of snow
at times. This will likely make for interesting travel today,
as snow squalls could cause very rapidly changing travel
conditions with areas of reduced visibilities and slick roads.

Have slightly tweaked snowfall totals overall and as such I
decided to include Southeast Raleigh County into the Winter
Weather Advisory. Although they don`t necessarily reach snowfall
criteria, the thought is that strong wind gusts causing blowing
snow with reduced visibilities and wind chills below zero
overnight warranted an advisory. All other areas are highlighted
in the HWO today, and we will likely handle heavier snow showers
this afternoon with Special Weather Statements.

Snow showers across the Lowlands will wind down tonight, but
upslope mountain snow should continue through the overnight
hours. Forecast accumulations across the Lowlands will likely be
spotty depending on where the heaviest squalls hit, but
definitely not unlikely for a few jackpot areas that see 1 to 2
inches.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
As of 233 AM Tuesday...

High pressure builds into the area on Wednesday bringing any
remaining mountain snows to an end. As the high builds in, winds
should diminish allowing the wind chill advisories to come to an
end as well.

The dry weather does not last long. An upper level trough and
surface low pressure will push east Wednesday night into
Thursday bringing another round of wintry precipitation to the
region.

Another upper level trough and surface low will bring yet
another period of unsettled weather from late Thursday night
into Friday night.

Went with model blends for temperatures through the period.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
As of 233 AM Tuesday...

Another area of high pressure will build in Saturday. As a
result, dry weather is anticipated for much of Saturday into
early Sunday. Another low pressure system will approach the area
from the southwest on Sunday and then push east Sunday night.
Expect precipitation associated with this feature to spread into
the area on Sunday with precipitation chances expected to
continue into Monday.

With southwesterly winds in place ahead of the low, expect
temperatures to rebound with daytime temperatures above normal
on Saturday. The airmass immediately behind the low is not that
cold. So expect afternoon readings on Sunday to be close to
normal.

&&

.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
As of 620 AM Tuesday...

A strong upper level system will be pushing into the region
today. In the NW flow, we will see lake effect streamers of snow
spread across the area and bring periods of heavy snow. In the
mountains the snow will be more persistent and IFR conditions
will be more likely at EKN and BKW today, while other sites will
be more hit or miss.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z WEDNESDAY...

FORECAST CONFIDENCE: Medium.

ALTERNATE SCENARIOS: Timing of snow showers and deteriorating
conditions on today will vary from forecast. Conditions may be
worse than currently forecast.

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 12/12/17
UTC 1HRLY       10   11   12   13   14   15   16   17   18   19   20   21
EST 1HRLY       05   06   07   08   09   10   11   12   13   14   15   16
CRW CONSISTENCY  H    M    H    M    M    M    L    H    H    H    M    M
HTS CONSISTENCY  H    H    H    M    L    M    M    M    H    H    M    M
BKW CONSISTENCY  H    H    M    H    M    L    L    L    L    L    L    L
EKN CONSISTENCY  H    M    M    M    L    L    L    L    L    L    L    L
PKB CONSISTENCY  H    H    M    M    M    M    M    H    H    H    M    M
CKB CONSISTENCY  H    M    M    M    L    M    M    M    M    L    L    L

AFTER 12Z WEDNESDAY...
Scattered snow showers and gusty winds will result in continued
areas of IFR into Wednesday morning particularly across the
mountains. Another round of snow is expected Wednesday night and
Thursday, particularly across the north, with IFR conditions
possible.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Winter Weather Advisory until 7 AM EST Wednesday for WVZ516-
     518-520-522>526.
     Wind Chill Advisory from 4 PM this afternoon to 1 PM EST
     Wednesday for WVZ518-520-522>526.
OH...None.
KY...None.
VA...None.

&&

$$
SYNOPSIS...JSH/MPK
NEAR TERM...JB/MPK
SHORT TERM...JSH
LONG TERM...JSH
AVIATION...MPK



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