Area Forecast Discussion
Issued by NWS Charleston, WV-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KRLX 232022
Area Forecast Discussion
National Weather Service Charleston WV
322 PM EST Thu Feb 23 2017
Unseasonably warm through Friday. A strong cold front crosses
pre- dawn Saturday morning, followed by cooler weather for the
weekend. A couple systems next week with precipitation chances.
.NEAR TERM /THROUGH FRIDAY/...
As of 120 PM Thursday...
Widely scattered showers associated with warm advection and weak
upper level short wave trough should be gone by late afternoon,
as the upper level wave exits. Otherwise a warm southwest flow
of unseasonably warm air dominates this period. Forcing
associated with a cold front approaching from the west late
Friday, and the associated convective threat, is progged to hold
west of the forecast area through 23Z Friday.
Inherited temperatures were accepted, close to guidance tonight
and a little above on Friday, not to mention as much as 8
degrees above record highs for Friday.
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
-- Changed Discussion --As of 310 PM Thursday...
Possible severe weather late Fri night into Sat morning...
Strong cold front approaches the region late Friday night. Out
ahead of the front a line of showers and thunderstorms will be
likely, but there is still a bit of uncertainty on how strong
this line of convection will be as it enters the Ohio Valley.
Although an EML plume pushes over the area, with Mid-level
lapse rates maxing out at 8.5C/km by 00Z Saturday, a strong cap
will be in place. By the time the front pushes in several hours
later, the plume shifts east, but lapse rates remain in the 7 to
7.5C/km range with colder air aloft moving in with the upper
trough. Low level moisture is quite limited and CAPE values
overnight only are in the 300 to 600 J/kg range. This will
certainly be a limiting factor, however the concern for severe
weather still remains because of the very strong 0-6km bulk
shear of +50 knots out ahead of the front.
The strong lapse rates and marginal instability should still be
enough to keep an upstream QLCS intact as it crosses our region,
however it is likely to weaken considerably as it pushes east.
It will be likely that any line of convection will have strong
wind gusts with it, and given the strong unidirectional shear it
is possible that some damaging winds will be possible. The greatest
threat will be in the Ohio Valley and a decreasing threat is
expected as the system head east.
The front will exit the region later Saturday morning and colder
air pushes in behind it. There is potential that with the cold
air advection and NW flow behind the front that we see a few
upslope snow showers across the mountains. However, moisture is
very limited so very little accumulation is expected. High
pressure will build in Sunday and snow showers come to an end
-- End Changed Discussion --
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 320 PM Thursday...
High pressure will be drifts eastward Sunday night. A southern
stream driven system pushes into the area on Monday. GFS us
still more robust and a bit earlier with this system than the
ECMWF. Due to the uncertainty, I went with a blend of ensemble
and operational guidance for this period which gives low chance
PoP for now. The next system moves in midweek as a surface low
comes out of the Rockies. Current guidance has this system
passing to our north and dragging a cold through the region
Wednesday night. With decent agreement between the overall
guidance, have decided to go with likely PoP even being Day 6 of
.AVIATION /21Z THURSDAY THROUGH TUESDAY/...
As of 120 PM Thursday...
Morning MVFR cu was most persistent over the western lowlands
early this afternoon. It may take until 20-21Z for it to mix out
over the middle Ohio Valley. MVFR mist is possible in the
deeper valleys overnight tonight, Otherwise VFR conditions
prevail in a south to southwest flow of unseasonably warm air.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z FRIDAY...
FORECAST CONFIDENCE: Medium to High.
ALTERNATE SCENARIOS: MVFR stratocu may persist more than
forecast this afternoon. MVFR (or worse) valley fog may affect
more sites than EKN overnight tonight. Increasing flow will
lessen the chance toward dawn Friday.
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
EST 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00
CRW CONSISTENCY H H H H H H H H H H H M
HTS CONSISTENCY M 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 M M H L H L H H H H H M
CKB CONSISTENCY H M H M H H H H H H H M
AFTER 18Z FRIDAY...
No widespread IFR conditions are expected at this time.