Area Forecast Discussion
Issued by NWS Charleston, WV

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215
FXUS61 KRLX 031914
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
214 PM EST Sat Dec 3 2016

.SYNOPSIS...
Weak upper trough Sunday into Sunday night. Low pressure Monday
night Tuesday. Briefly milder in its wake mid week, then much
colder late week.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 145 PM Saturday...

As expected the stratus has held firm today as cirrus overspreads
the area ahead of the next system. Even though some of this
stratus will lift as the low level flow turns more SE, this will
keep temps from dropping much tonight so another day of going
above guidance for lows.

A southern stream system will approach Sunday in the form of a
surface wave with induced isentropic lift overspread the TN Valley
into SW VA. Given how dry the low levels are, this will fall as
virga initially before reaching the ground around sunrise. Thermal
profiles suggest some wet snow may fall on the highest ridges in
SW VA early Sunday morning but with little if any accumulation.
Most of the lift will slide into VA as the day progresses with a
S/W trof tracking thru the OH Valley. This combined with some
downsloping SE flow should leave much of the area dry as the
shadow and dry air keep any precip as virga until late in the day.
Across the mountains, in particular Pocahontas County, light
precip will fall as a mixture with all snow on the ridges. Temps
on Sunday should manage to warm well into the 40s across the
Lowlands with 30s in the mountains.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 430 PM Saturday...

Precipitation overspreads the area from southwest to northeast on
Sunday, as a weak short wave trough crosses. This will be a split
system, with the best forcing associated with the short wave
passing north of the forecast area. However, channeled vorticity
and southern stream moisture will make for another precipitation
maxima to the south. With this maxima coming close to the
forecast area from the south, precipitation is most likely late
Sunday far southern portions of the forecast area, mainly the
southern mountains.

Precipitation may begin as a wintry mix far south first thing
Sunday morning, but low level warming will bring about a quick
change over to rain, without much accumulation or hazard. As the
system moves off to the east on Sunday night, there may be enough
cold air aloft for a wintry mix in the northern mountains.
However, since the moisture layer will be becoming shallow, lack
of ice crystals may lead to just drizzle / freezing drizzle but,
again, not much hazard.

Weak Pacific high pressure crosses Monday, as upper level ridging
crosses late Monday. This will be quickly followed by the next
system, an upper level closed low over northwest Mexico early
this morning, that ejects out into TX early Monday morning, and
then dampens out as it moves up the Ohio Valley Tuesday morning.
This, and its attendant surface low pressure system and associated
warm advection and dynamics, will result in rain overspreading the
forcast area quickly as dawn Tuesday approaches.

The rain will diminish from southwest to northeast Tuesday as the
system lifts on through. Little in the way of cold air initially
follows the system Tuesday night, so an overcast, damp night
appears in store, but any lingering precipitation will be light,
and primarily of the liquid variety.

Temperature close to a raw and MOS based blend.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 430 PM Saturday...

Much colder air arrives this period, but with lingering questions
as to when the colder air arrives. Models disagree on the degree
of cold air eventually coming in Wednesday and Wednesday night in
the wake of the Tuesday system, and on the timing of a cold front
on Thursday. The two factors combined result in a 15 F degree or
more spread between temperature outcomes Thursday. The forecast
represents a blend, but a little toward the colder solution, per
WPC preference and coordination with neighboring offices.

Rain showers in the wake of the cold front Thursday are thus most
likely to mix with and change to snow showers in the west, and
over the higher terrain.

Cold canadian air takes over by Thursday night, and dominates
through the balance of the forecast, with highs below freezing for
the first time this early winter season Friday, and maybe getting
back above freezing over the lowlands on Saturday, as upslope snow
showers diminish.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
As of 200 PM Saturday...

Widespread MVFR cigs mainly across the mountains of WV, and north
central WV through the late afternoon. Otherwise, a general
improvement to low VFR much of the area this evening, although
MVFR cigs may continue to linger across parts of the higher
terrain including at site KEKN.

A system approaches from the SW on Sunday with cigs gradually
lowering into MVFR across KBKW. Light rain will try to overspread
the area but dry air in the low levels will keep much of this
across SW VA and the E Slopes, where a light wintry mix is
expected, especially in the high terrain where IFR conditions will
develop.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z SUNDAY...

FORECAST CONFIDENCE: Medium.

ALTERNATE SCENARIOS: Timing of category changes in clouds may
vary this evening.

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.

UTC 1HRLY       18   19   20   21   22   23   00   01   02   03   04   05
EST 1HRLY       13   14   15   16   17   18   19   20   21   22   23   00
CRW CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M
HTS CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M
BKW CONSISTENCY  M    H    H    H    H    H    H    H    H    H    H    M
EKN CONSISTENCY  M    M    M    M    M    M    M    M    M    M    M    L
PKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M
CKB CONSISTENCY  M    M    M    H    M    M    M    M    H    H    H    M

AFTER 18Z SUNDAY...
IFR possible in rain and snow, particularly in the mountains
Sunday night into Monday. Additional IFR possible in rain and snow
towards mid week.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.

&&

$$
SYNOPSIS...30/26
NEAR TERM...30
SHORT TERM...TRM
LONG TERM...TRM
AVIATION...30



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