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FXUS61 KRLX 261329
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
929 AM EDT Wed Sep 26 2018

.SYNOPSIS...
Cold front pushes through today. Wave rides up along front
Thursday into Thursday night. High pressure with drier weather
for the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 920 AM Wednesday...

Sfc cold front is progressing across OH this morning and is just
NW of the CWA, as of writing. Areas of showers continue to
develop well ahead of the front with a band of heavier showers
trying to develop along the front itself.

Ongoing precip this morning should negate significant
atmospheric destabilization today. However, effective bulk
shear values are currently around 40 kts, which should be
sufficient for at least a marginal strong wind gust to occur
with any convection that can manage to develop along the front
later this morning and early afternoon. SPC has maintained a
marginal risk of severe weather for roughly the northern half
of the CWA for today.

Have increased POPs across E KY and W WV for this morning by
about 10 to 20 percent, mainly to account for radar trends (and
delayed thunder mention until late morning). Also increased
wind speeds for the higher elevations along the eastern CWA.

Will maintain Flash Flood Watch as some embedded heavier rains
could still fall today on saturated soils.

As of 640 AM Wednesday...

First band of showers has actually fallen apart early this
morning. Next and last band, pending redevelopment later today,
was entering the western flank of the forecast area.

410 AM Wednesday...

Cold front stretching from northeast to southwest, through
approximately a Detroit - Evansville line, approaches the middle
Ohio Valley this morning, and crosses midday and early this
afternoon, and then crosses the central Appalachians late this
afternoon.

Severe potential ahead of this front will be limited by early
timing, post-equinox sun angle, as well as clouds and showers
associated with a wave crossing the area early this morning,
out ahead of the front. The gridded PoP forecast loses
distinction between this line, and one last general band or
zone of showers and thunderstorms, more immediately ahead of the
cold front, later this morning.

CAPE is progged to get just above 1000 J/KG just ahead of the
front, while effective bulk shear approaches 40 kts before the
frontal passage takes out the CAPE. Thus, a marginal threat for
severe exists, primarily on wind gusts, and this primarily due
to wet ground, in which trees could more easily be felled by
lesser wind. This is reflected in the latest SWODY1.

Low clouds and fog may form for a time tonight in the wake of
the front, before drier air filters into the middle Ohio Valley
overnight. Fog and stratus is thus most likely to persist over
the mountains. However, if higher clouds thin out, they will
likely start to thicken again toward dawn, as the front starts
to buckle in response to a wave forming along it, near or south
of the Tennessee Valley. This also lessen the fog and stratus.

While the PoP forecast reflects a slightly sharper northwest
cutoff of the precipitation, temperatures and dew points
reflect its slower progress, and then its buckling toward dawn.
Highs today occur early over the middle Ohio Valley.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
As of 415 AM Wednesday...

Main change from the previous forecast was to keep unsettled
weather in the forecast Thursday into early Friday. The culprit
being a potent disturbance traversing the base of the mean
longwave trof, as the persistent ridge off the East Coast holds
keeps the surface front close by. This resulted in increasing
pops Thursday and Thursday night into likely across central and
eastern WV along with the southwest VA counties. Areas along the
OH River and especially the southeast OH counties may hold on
to drier conditions. QPF looks light, with higher amounts
remaining east of the CWA.

Mid level dry air surges in early Friday as the system departs
to the northeast. However, abundant low level moisture will
linger such that low stratus will be the rule at least through
midday. In fact, enough westerly flow in the low levels may
result in orographically enhanced lift for patchy drizzle Friday
morning. Eventually by afternoon, enough mixing occurs to allow
the stratus to scatter into a robust cu field. A secondary cold
front looks to cross Friday evening with little fanfare, and high
pressure noses in for Saturday. This will finally allow lower
dewpoints to settle...more typical of late September.

Temperatures were derived from a blend of NBM and NAM, resulting
in cool afternoons and mild nights Thursday and Friday. While
Saturday will see a rebound in temperatures for highs, lows
Saturday night will be quite a bit cooler than of late. Finally
a decent Autumn fire pit night shaping up.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 430 AM Wednesday...

High pressure slides off to the east Sunday with return flow
allowing temperatures and dewpoints to recover. This trend
continues early next week, as the upper level ridge migrates
west into the southeast states. Some WAA showers may skirt
southeast OH from time to time, but thankfully, no significant
rain makers are on the horizon.

&&

.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
As of 640 AM Wednesday...

Band of showers ahead of a cold front was dissipating early this
morning, with minimal aviation impacts.

Another band of showers and thunderstorms will cross today.
MVFR to brief IFR conditions, along with thunder and gusty
winds, are possible.

The front will cross this afternoon, with brief MVFR stratocu
in its wake into tonight. MVFR stratocu and visibility is most
likely in the mountains overnight, settling to IFR late, mainly
on stratus.

South to southwest flow will switch to northwest behind the
front this afternoon.

CONFIDENCE: Medium.

ALTERNATE SCENARIOS: Timing of precip and associated conditions
may vary today. Fog/stratus 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.

AFTER 12Z THURSDAY...IFR in stratus, mainly in the mountains
early Thursday morning, and at times in showers and post rain
stratus and fog overnight Thursday night into Friday morning.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Flash Flood Watch until 5 PM EDT this afternoon for WVZ005>011-
013>020-027>031.
OH...Flash Flood Watch until 5 PM EDT this afternoon for OHZ066-067-
075-076-083>087.
KY...Flash Flood Watch until 5 PM EDT this afternoon for KYZ101>103-
105.
VA...None.

&&

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