Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 140450
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
1150 PM EST Wed Dec 13 2017

.SYNOPSIS...
Snow showers mainly across the northern portion of the area
tonight into Thursday morning.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 1150 PM Wednesday...With wind gusts in the higher
elevations possibly reaching as high as 50 mph overnight through
Thursday morning, it was decided that a wind advisory will be
needed.

As of 1125 PM Wednesday...Winds are still running a little
higher than previously forecast so decided to bump up wind gusts
more using RUC momentum transfer based on forecast mixing
heights. This appears to have a good handle on the current
situation. Expecting winds to pick up to over 45 mph in the
higher elevations over the next few hours as the tightest
thermal packing nudges across the mountains. After 15Z that
gradient should ease abit based on the model consensus with high
pressure quickly moving in behind the system.


As of 1005 PM Wednesday...

Made some significant increases to the wind gusts tonight based
somewhat on what is happening upstream in Ohio. High resolution
models are not predicting the same type of momentum transfer in
terms of gusts for our area, but 30kts is possible, slightly
higher in the highest ridges.

As of 220 PM Wednesday...

Clipper system moves across north of the area tonight and exits
tomorrow morning. Moisture is limited initially and this will
limit snow accumulations. The usual upslope areas of the Eastern
mountains may see 1-3 inches, elsewhere little or no
accumulations. Wind chills will be close to criteria but will
hold off for now. System exits quickly tomorrow and should see
improvement from west to east throughout the day.

Cold high pressure builds into the area Thursday into Thursday
night. Another clipper system will pass by well to our north
Friday into Friday night. This will limit any precipitation to
our northern tier zones and our Eastern mountain upslope areas.
Elsewhere should be mainly dry.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 245 PM Wednesday...

Weak high pressure builds into the area Thursday night ahead of
yet another clipper system. This time, the parent low stays up
across the Great Lakes with only a dragging weak cold front
behind. Behind well south of favorable lake-enhanced low-level
moisture transport, only a slight chance of snow is advertised
across the northern counties with a low chance across the
mountains given a small component of upslope enhancement.
Modest warm air advection ahead of the front bump afternoon
temperatures across the lowlands above freezing after a cold
night in the teens and 20`s. Behind the front, winds turn
westerly as opposed to northwesterly, making cold air advection
into the area negligible - setting up a slightly warmer Friday
night/Saturday morning with lows in the mid-20`s in the lowlands
and mid-teens to around 20 F in the mountains.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...

Weak high pressure builds again behind the short term period`s
clipper system Saturday. Winds near the surface turn
southwesterly beginning Saturday morning, warm advecting through
the weekend with temperatures reaching into the 30`s/40`s on
Saturday and into the 40`s/upper 40`s my Sunday. Models agree on
a warm front lifting up through the area Sunday accompanied by
scattered rain showers and perhaps a snow/mix upon onset during
the morning.

The associated cold front moves through by Monday night. Model
discrepancies are aplenty beyond this point - from the surface
through the upper-levels. The progression of a Rockies trough
across the CONUS will dictate sensible conditions through the
rest of the period. So, went for a general blend beyond this
point with a notable period of possible upslope precipitation
during Tuesday.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
As of 1005 PM Wednesday...

Increased winds through 15Z significantly across all terminals
with gusts to 30kts.

As of 640 PM Wednesday...

Snow showers develop across CKB and EKN tonight with a couple of
upper level waves and surface troughs, along with low end
accumulations, generally 1 to 3 inches for those areas. Other
terminals will see less than an inch and no restrictions, while
CKB and EKN could see IFR visibilities after 04Z tonight. Using
TEMPOs for the most part with this issuance for the IFR.
Thinking is that the activity will be on and off in nature.

Winds also increase with the passage of the surface troughs, and
gusts to 20kts are possible tonight into the post-dawn hours
Thursday.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z FRIDAY...

FORECAST CONFIDENCE: Medium to High.

ALTERNATE SCENARIOS: Timing of ceilings and snow showers
tonight may vary.

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                                                  THU 12/14/17
UTC 1HRLY       03   04   05   06   07   08   09   10   11   12   13   14
EST 1HRLY       22   23   00   01   02   03   04   05   06   07   08   09
CRW CONSISTENCY  H    H    H    L    H    H    M    M    M    H    H    M
HTS CONSISTENCY  H    H    H    L    H    H    H    M    H    H    H    M
BKW CONSISTENCY  H    H    H    H    M    H    L    L    L    M    M    L
EKN CONSISTENCY  M    L    L    L    L    L    L    L    L    L    M    M
PKB CONSISTENCY  H    H    L    M    M    M    H    H    H    H    L    M
CKB CONSISTENCY  H    H    H    M    H    L    L    M    M    M    H    M

AFTER 06Z FRIDAY...
Another round of snow is expected across the northern portion of
the area on Friday and Friday night, with IFR conditions
possible in heavier snow showers.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Wind Advisory until noon EST Thursday for WVZ516-518-520-
     522>524-526.
OH...None.
KY...None.
VA...None.

&&

$$
SYNOPSIS...JS/MC
NEAR TERM...JS/MPK/26
SHORT TERM...MC
LONG TERM...MC
AVIATION...26


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