Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 201948
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
348 PM EDT Fri Oct 20 2017

.SYNOPSIS...
High pressure remains in control, with cool nights and warm
afternoons through the weekend. A strong cold front and low
pressure system crosses early next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 150 PM Friday...

Mainly clear overnight...though cirrus will try to spread into
the area toward dawn. Another beautiful warm day Saturday with
some passing cirrus. I continue to go a little below guidance
for overnight lows, especially in the mountain valleys with near
ideal radiational cooling once again. Highs on Saturday were
nudged near the warm side of the envelope with 10 t0 15 degrees
above average expected.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 345 PM Friday...

High pressure remains in control with deep southwesterly flow
continuing to bring above-average warmth into the Mid-Ohio
Valley and Central Appalachia. Low-level cloud cover will begin
to build in from the southeast with the approach of a deep
trough late Sunday.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 345 PM Friday...

A briefly cut-off low will merge again with the northern jet
and undergo cyclogenesis in the central to eastern CONUS by the
start of the next work week. Models are beginning to hone in on
a solution that suggests a storm track through the Ohio Valley
though substantial track differences still exist. More
expeditious guidance brings rain showers in starting midday
Monday, although downsloping would favor a delayed onset until
Monday night - closer to a consensus blend of guidance. An even
greater delay in rain is possible if cyclogenesis is
concentrated further south allowing greater warm air advection
to push the frontal zone north. Nevertheless, the forecast
depicts an elongated frontal zone passing through the area early
Tuesday morning. Though exact frontal position is up for
debate, high confidence exists for gusty, widespread rainfall
Monday night through Tuesday.

Being that cyclogenesis in this case is aided by strong
divergence associated with a 120+ kt 300mb jet, and the
deepening of this low tightens height gradients through the
column, winds are expected to increase first with system onset
Tuesday morning and again with the secondary cold front on the
back side of the system Wednesday morning. The secondary cold
front will usher in the coldest air experienced thus far this
season with northwest flow behind. Showers may linger through
Wednesday tapering off Thursday under the influence of a brief
ridge. Pattern remains active with another trough to round out
the week.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
As of 150 PM Friday...

High pressure overhead today with mostly clear skies. Low level
flow should be weaker tonight through Saturday morning, so IFR
or worse river valley fog will be possible. However, current
thinking is for shallow fog confined tight to the rivers with
terminals staying above the fog layer. The exception being EKN
where enough agreement in guidance for dense fog late.

VFR conditions areawide Saturday amid some passing cirrus.

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

FORECAST CONFIDENCE: Medium overnight.

ALTERNATE SCENARIOS: IFR or worse fog could sneak into CRW/PKB
in the 11 to 12Z timeframe.


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    M
HTS CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M
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    M
CKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M

AFTER 18Z SATURDAY...
Dense valley fog possible each morning through the weekend, and
in rain at times early next week.

&&

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

&&

$$
SYNOPSIS...30/MC
NEAR TERM...30
SHORT TERM...MC
LONG TERM...MC
AVIATION...30



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