Area Forecast Discussion
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FXUS61 KRLX 240750
Area Forecast Discussion
National Weather Service Charleston WV
250 AM EST Fri Feb 24 2017
Unseasonably warm today. 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 TONIGHT/...
As of 245 AM Friday...
Have some good operational model agreement with the timing of
the cold front tonight that will bring showers and thunderstorms
to the CWA, generally after 06Z. Plenty of dynamics with this
system, with an increasing low level jet and tightening 500mb
height gradient in the trailing upper level low, but
thermodynamic parameters lack a bit with dewpoints in the low
50s and no appreciable advection of moisture at 850mb. That
said, there should be enough going on, warranting the slight
risk in the far western CWA for the Day 1 outlook. Given the
time of day, QLCS formation to the west may be on the gradual
wane heading into our area during the overnight, but strong
flows could also be enough to keep a line of storms going. This
is reflected in the outlook and the ending of the slight risk
over the far western zones.
Prior to the front, could be looking at some all time record
highs for February today with low 80s in the forecast.
.SHORT TERM /SATURDAY THROUGH SUNDAY/...
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
.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 /08Z FRIDAY THROUGH TUESDAY/...
As of 1235 AM Friday...
VFR dominated forecast ahead of a cold front that will push
towards the Ohio River Valley near the end of the forecast
period. Ceilings to lower ahead of the system, but should stay
well above any restriction thresholds.
Expecting the flow to pick up through the period as well out
ahead of the aforementioned cold front. Since the wind will
exist at the surface, will forego any LLWS in the forecast, but
it should be noted that low level wind speeds will increase
fairly dramatically with height, into the 5000ft level with the
low level jet. These low level winds will be strongest at the
end of the forecast.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z SATURDAY...
FORECAST CONFIDENCE: High.
ALTERNATE SCENARIOS: EKN may dip into IFR for vsby tonight with
fog if low level flow is not strong enough.
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 02/24/17
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 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 06Z SATURDAY...
No widespread IFR conditions are expected at this time.