Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 220006
AFDRLX

AREA FORECAST DISCUSSION
National Weather Service Charleston WV
706 PM EST Thu Feb 21 2019

.SYNOPSIS...
High pressure in control through early tonight. Several systems
will bring unsettled weather mainly across the south tonight
into Friday night and then spreading north through the weekend.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 705 PM Thursday...

Sped up the POPs slightly across the west. Have echoes aloft,
most of it likely not reaching the ground yet, but brought low
end POPs in to cover just in case. No major changes to the
advisory area in the mountains for the freezing rain.

As of 209 PM Thursday...

Surface high pressure system remains on control of our weather
into early tonight. A series of shortwaves then should result
in increasing clouds as well as precipitation moving back into
the region from the southwest tonight.

Based on latest model guidance, have increased POPs to likely
tonight across southwest VA as well as far southern WV and the
WV mountains. The precipitation should fall as rain in most of
these locations. However, freezing rain is possible across the
highest elevations of the northern mountains where up to 0.10
inches of ice is possible. After consultation with our neighbors,
have gone ahead and issued a winter weather advisory.

Models suggest northern edge of precipitation should move back
to the south during the day. Because of consistency between the
models, have gone ahead with this thinking.

Could see 0.25 to 0.50 inches of rain across our far southern
counties tonight through Friday.

Previous temperature forecast generally looks good. Have only
made minor tweaks to reflect latest guidance.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 310 PM Thursday...

Scattered showers linger as a remnant frontal boundary stalls
Friday evening across the southern third of the area. Meanwhile,
a deeply amplified trough ejects from the Rockies during this
time, producing a variety of potential hazards as it approaches
and crosses our area. A light glaze along the highest ridges and
peaks of the north/central WV mountains is possible early
Saturday as precipitation moves into the area, but impacts would
be minimal with quickly warming temperatures.

The trough of interest rotates negatively into the Plains
Saturday, strengthening southwest flow to 50 kts at 850 mb,
lifting the remnant boundary North as a warm front in the Ohio
Valley. As a result, moisture increases to 1.3"+ PWAT area-wide
by Saturday afternoon. This leaves ample opportunity for
moderate to heavy rainfall basically everywhere Saturday into
Saturday night. While many long-range models have consistently
placed an axis of heavy rainfall of 1-2" near and South of the
64 corridor, the NAM and SREF have trended and shifted the
corridor further North into the Middle Ohio Valley and into SE
Ohio. Most of these lowland areas are already saturated, and
have streams already running high, and the mountains have
considerable liquid captured in snowpack, so flood vulnerability
exists basically everywhere. The greatest threat would
therefore exist where any axis of heavy precipitation sets up.

Fortunately, convective rainfall looks unlikely on Saturday with
a strong low-level temperature inversion keeping things pretty
well capped in this warm frontal scenario. Some elevated
instability exists in the OH/KY/WV Tri-state region Saturday
afternoon, but currently not enough confidence to include thunder
in that portion of the forecast. Saturday night, thunderstorm
threat increases in spite of fairly limited instability, and is
chiefly tied to the cold front itself, where frontal lift can
tap into modest elevated CAPE on the order of 500 J/KG CAPE.
Very high shear on the order of 80+ kts 0-6km means that one or
more potent lines of thunderstorms will form ahead of the front
packing isolated damaging wind gusts. Storms will tend to be
much stronger toward the West over parts of the lower Ohio and
Tennessee Valleys where stronger daytime instability exists,
however those storms will likely spill into Appalachia as they
weaken with the setting sun thanks to aforementioned strong low-
and mid- level flow. So, strong gusts, mainly sub-severe, are
likely area-wide, but saturated grounds mean trees and power
lines can come down with wind gusts well below severe criteria.

Models place the cold front near the Ohio River during the pre-
dawn hours of Sunday and then quickly shoves it across the WV
mountains by late morning. Moisture aloft quickly diminishes
behind the front, ending the flood and thunderstorm threat. Low-
to mid-level moisture remains in the cold-advective scheme, so
do expect area-wide cloud cover to remain through the period
with lingering drizzle/freezing drizzle in the mountains
tapering off Sunday evening. Strong winds do linger however
through Sunday as the upper level trough rotates up and out
toward the northeast, with gusts 30-40+ kts possible everywhere.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 315 PM Thursday...

Zonal flow takes hold across much of the CONUS with the departure of the short-
term period`s trough, which makes for a relatively quiet and
much-needed dry period, albeit with a degree of temperature
uncertainty given weak forcing. The GFS tends to keep the region
on the warm side and the ECMWF on the cool side. Long- range
models bring in the next system by mid-week.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
As of 630 PM Thursday...

The forecast starts off with VFR dominating until a frontal
band to our south spreads precipitation northward into the
southern half of the region. Clouds will spread lower all around
and be aggressively lower in the southern portions of the area.
Rain showers will spread from South to North as well bringing
MVFR ceilings to some terminals. BKW will encounter rain first,
just before midnight, and continue for the duration of this
forecast period. There will be brief periods of rain showers
with MVFR ceilings at HTS/CRW around midnight for a few hours.
BKW will also have brief periods of IFR visibility in any
heavier rain showers especially early in the morning. Winds will
be northerly and light overnight and shift to the north-
northeast by early morning. One thing worth mentioning, if any
rain does make it into the eastern mountains where temperatures
are below freezing (far north) there can be patchy freezing
rain across the highest elevations early in the morning.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SATURDAY...

FORECAST CONFIDENCE: High.

ALTERNATE SCENARIOS: None.
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                                                                 FRI
UTC 1HRLY       00   01   02   03   04   05   06   07   08   09   10   11
EST 1HRLY       19   20   21   22   23   00   01   02   03   04   05   06
CRW CONSISTENCY  H    H    H    H    H    H    H    H    H    M    H    H
HTS CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
BKW CONSISTENCY  H    H    H    H    M    M    M    M    L    M    M    L
EKN CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
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 00Z SATURDAY...
IFR possible in rain beginning Friday night and continuing
through Saturday night.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Winter Weather Advisory until 10 AM EST Friday for WVZ523-526.
     Flood Watch from 1 AM EST Friday through Sunday morning for
     WVZ005>007-013>015-024>027-033-034-515>520.
OH...Flood Watch from 1 AM EST Friday through Sunday morning for
     OHZ083-086-087.
KY...Flood Watch from 1 AM EST Friday through Sunday morning for
     KYZ101>103-105.
VA...Flood Watch from 1 AM EST Friday through Sunday morning for
     VAZ003-004.

&&

$$
SYNOPSIS...JSH/MC
NEAR TERM...JSH/26
SHORT TERM...MC
LONG TERM...MC
AVIATION...JZ


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