Scientific Forecaster Discussion
fxus61 krlx 240304
Area forecast discussion
National Weather Service Charleston WV
1004 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 1000 PM Thursday...
Adjusted hourly temps to reflect quick drop off in the protected
valleys and hollows.
As of 630 PM Thursday...
Forecast in good shape this evening. A couple of renegade Stout
showers across Perry County, otherwise mild and quiet this
evening. As for Friday, it still appears many all time record
highs for the month of February will be challenged. Little in
the way of cloud cover with a downsloping southeast low level
flow to boost numbers.
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/...
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 northwest 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
European model (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 /03z Friday through Tuesday/...
as of 630 PM Thursday...
Some passing altocu and cirrus tonight with VFR conditions
prevailing. The lone exception being ekn, where some MVFR fog is
forecast. Low level flow picks up tonight with a marginal low level wind shear
setup for the Ohio River sites. Will have to monitor this
evening, but it does not appear strong enough to meet criteria
VFR conditions on Friday with just some passing mid and high
clouds from time to time. Winds may become gusty by mid to late
morning with 15 to 25 kt gusts developing, primarily across
Forecast confidence and alternate scenarios through 00z 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 weather forecast office 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 Friday 02/24/17
UTC 1hrly 03 04 05 06 07 08 09 10 11 12 13 14
EST 1hrly 22 23 00 01 02 03 04 05 06 07 08 09
crw consistency h h h h h h h h h h h M
heights 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 M M M M 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 00z Saturday...
no widespread IFR conditions are expected at this time.