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000
FXUS61 KRLX 131822
AFDRLX

AREA FORECAST DISCUSSION
National Weather Service Charleston WV
222 PM EDT Thu Aug 13 2020

.SYNOPSIS...
A weak frontal boundary will remain stalled over the region
through the rest of the work week. Weather remains unsettled
through the upcoming weekend. Cold front Sunday night.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 222 PM Thursday...

Latest surface analysis shows a quasi-stationary boundary is in
place across southern OH and northern WV. This feature has provided
enough of a focus for scattered convection across the mountains and
more isolated activity across the lowlands so far this afternoon.
With MLCAPE values around 1000-1500 J/kg and weak shear, any
thunderstorm activity that develops should be pulse type convection.
Thus, greatest concern for the remainder of the afternoon and
evening is locally torrential downpours that could result in
localized water issues given plenty of moisture with PWATs around
1.6 to 1.8 inches and slow storm motions. Since many areas in the
mountains received 1 to 2 inches of rain yesterday, FFG values have
dropped considerably across eastern portions of our forecast area
and with convection mainly focused across the mountains once again
today, WPC has a Slight Risk for Excessive Rainfall mainly across
our mountainous counties and a Marginal Risk extending to areas near
Interstate-79.  Thus, will need to keep a close eye on this area
through the remainder of the day but thunderstorm activity should
remain isolated enough across the lowlands to mitigate a greater
flood threat.

As instability wanes tonight, the majority of the precipitation
activity should diminish but a few light showers may linger into the
overnight hours across the mountains. Otherwise, another night of
valley fog and/or low stratus appears to be possible as many areas
decouple amid moist low levels. After fog lifts Friday morning,
attention turns to an upper trough across the middle Ohio
Valley that will slowly approach our area through the day. As a
result, showers and storms will once again be expected across
the area Friday afternoon and evening. Since this feature will
provide better upper level support compared to recent days, this
should allow for better precipitation coverage across the area.
While chances for severe weather should remain low, a
warm/moist environment will remain in place so additional
downpours localized water issues will be possible once again.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 205 PM Thursday...

Southwesterly flow increases Friday night in response to an
approaching southern stream wave. This may assist in updraft
organization of lingering afternoon convection keeping it going
through the evening hours. Stronger forcing arrives by the morning
hours Saturday with numerous showers and thunderstorm expected
through the day. This will keep temps and surface based instability
down a bit compared to previous days, but synoptic forcing,
particularly on the left entrance quadrant of the H200 wind max will
be more than sufficient to squeeze out very efficient rainfall
across portions of the middle Ohio Valley in an environment of near
climatological maximum precipitable water values with substantial
warm cloud depth.

Should still have relatively high flash flood guidance here for the
most part with limited rainfall expected Friday - but may begin to
see some localized high water issues. Further south, a low level
moist convergent axis could cause additional water issues for our
southeastern counties where localized heavy rain last night and
again tonight precedes it. Currently, WPC has the mountains
outlooked as a slight risk for excessive rainfall (where confidence
is higher that flash flood guidance will be lower) with a marginal
risk over most of the remainder of the area.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 205 PM Thursday...

The 1.6 to 2.0 inch precipitable water plume finally departs to the
east Sunday with passage of the trough axis/low level closed
circulation making for a mainly dry morning. Will catch a glancing
blow from a northern stream disturbance/surface cold front Sunday
evening with some additional showers and thunderstorms
possible. While mid-level lapse rates nor shear are particularly
impressive, could see some better organized updrafts with at
least some wind/hail potential with this should the front
accelerate and come through in the late afternoon/evening, but
for now looks more like a late evening/overnight passage.

Cooler and mainly dry weather prevails for Monday and Tuesday under
northwesterly flow with surface dew points dipping back down toward
the upper 50s feeling pretty good after the recent run of 70s.
Sadly, heat and humidity looks to make a return by the end of the
week along with a reintroduction of diurnal showers and storms.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
As of 108 PM Thursday...

High pressure to the north of the area should maintain mainly
VFR conditions across the region through the remainder of the
afternoon. However, there may be brief periods of IFR/MVFR
restrictions as a stalled frontal boundary over the area should
provide enough focus for scattered showers and thunderstorms.
Greatest chance for thunderstorm activity is expected to be
across the mountains and less of a chance across the lower
elevations.

Any precipitation across the area should dissipate tonight with
the loss of daytime heating. However, light to calm winds and
moisture in the low levels of the atmosphere should support the
development of fog and/or low stratus overnight. An extended
period of IFR or even LIFR conditions will be possible where fog
and/or stratus develops. Otherwise, any fog across the area
should lift by around 13Z on Friday and VFR conditions should
then return to most of the area. However, MVFR stratus may
linger throughout most of the morning across the mountains. In
addition, an upper level disturbance will approach the area
tomorrow with another round of showers and thunderstorms and
possible further restrictions by the end of the TAF period.

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

FORECAST CONFIDENCE: Medium.

ALTERNATE SCENARIOS: Timing, duration, and extent of fog
overnight may vary from 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.

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

AFTER 18Z FRIDAY...
Brief IFR in showers and thunderstorms Friday afternoon and
evening. Another round of showers and thunderstorms will then
be possible on Saturday with additional brief IFR restrictions.

&&

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

&&

$$
SYNOPSIS...JP/RG
NEAR TERM...RG
SHORT TERM...JP
LONG TERM...JP
AVIATION...RG