Area Forecast Discussion
Issued by NWS Charleston, WV

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983
FXUS61 KRLX 220710
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
210 AM EST Thu Feb 22 2018

.SYNOPSIS...
Cold front stalled across the south early this morning, and
meanders through the end of the week as surface waves pass.
Areas of significant rainfall possible into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 100 AM Thursday...

Surface boundary currently stalled out across southern coal
fields and southern mountains, with a surface wave beginning to
move out of the lower Mississippi Valley. Also have 500mb
shortwave trough coming out of the southern plains. All of this
is resulting in an area of precipitation stretching from Texas
into the middle Ohio River Valley. High res models seem to have
a decent handle on this, so used a blend of HRRR and NAMNest to
tighten up POP gradients. Through this morning, have an area of
100 POPs developing across SE Ohio as the surface wave
approaches and nudges the front back to the NW. As the surface
wave passes, have the higher POPs crossing the Ohio River and
gradually decreasing as the front drifts back to the SE -- away
from the better mid and upper level support -- and stalls in or near
the SE corner of the forecast area. Have 0.5-0.75 inches of rain
with the wave today, mainly along and NW of the Ohio River. Plan
to keep an eye on new data as it rolls in this early this
morning to help decide if the flood watch need to be moved
earlier -- but with the current QPF think we can handle this
first wave with no significant issues and have not changes the
watch timing.

The next surface wave in the train approaches tonight, with a
similar trend of pushing the surface boundary back north. Have
an area of high chance POPs along the front tonight. Opted to
not go likely at this time due to lack of mid and upper level
support, anticipating scattered showers.

Temperatures through the period are very tricky, as the surface
boundary provides a rather sharp gradient. Used a blend of high
res models on the hourly temps trying to capture its meandering
over the next 24 hours. However this leads to rather low
confidence, as a 20 mile change in the boundary position will
result in up to 10-15 degrees difference in temperatures at any
given spot. In general terms... it will be very mild across the
SE with highs today near 70, but much of SE Ohio and NE Kentucky
will struggle to bump above 50.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
As of 200 AM Thursday...

Frontal boundary lifts back north Friday with additional waves
moving along the front, enhancing precipitation, particularly
across northern zones where flood watch is in place. The front
will sag south, and waffle around the area in vicinity of Ohio
River late Friday into Saturday, before finally lifting back
north again late Saturday, as a strong low pressure system moves
northeast out of the southern plains. Good southwesterly
flow/llj/moisture tap from Gulf, with PW values rising to over
1.4 inches. Time period of greatest precipitation looks to be
Saturday night/early Sunday, with a general inch and a half of
qpf, if not more in spots. Drying trend gradually takes place on
Sunday, as high pressure builds in behind departing cold front.


&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 210 AM Thursday...
High pressure in control during the period with dry and mild
conditions.

&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
As of 100 AM Thursday...

Not a good day for non-instrument flight as low MVFR and IFR
conditions are expected across most of the forecast area through
the TAF period. A surface wave will move through today, with
rain showers. These are already moving into the Tri-state area,
and will mainly be along and west of the Ohio River through the
predawn, before shifting eastward later this morning into this
afternoon. Winds are mostly out of the N to NE currently, but as
the wave passes winds will vary quite a bit from place to place.

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

FORECAST CONFIDENCE: Medium.

ALTERNATE SCENARIOS: Timing of MVFR/IFR conditions may vary
through the TAF period.

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 02/22/18
UTC 1HRLY       06   07   08   09   10   11   12   13   14   15   16   17
EST 1HRLY       01   02   03   04   05   06   07   08   09   10   11   12
CRW CONSISTENCY  M    M    M    L    M    L    M    M    M    M    H    L
HTS CONSISTENCY  H    M    H    M    M    L    L    M    M    M    L    M
BKW CONSISTENCY  H    H    H    M    H    H    H    H    H    H    H    M
EKN CONSISTENCY  M    M    M    M    M    M    M    M    M    M    M    L
PKB CONSISTENCY  H    H    H    H    H    H    M    M    M    M    M    L
CKB CONSISTENCY  M    L    M    M    H    H    H    H    H    M    M    L

AFTER 06Z FRIDAY...
IFR possible at times in showers into the weekend.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Flood Watch from this evening through Sunday morning for
     WVZ005>011.
OH...Flood Watch from this evening through Sunday morning for
     OHZ066-067-075-076-083>087.
KY...Flood Watch from this evening through Sunday morning for
     KYZ101-103.
VA...None.

&&

$$
SYNOPSIS...MZ/SL
NEAR TERM...MZ
SHORT TERM...SL
LONG TERM...SL
AVIATION...MZ



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