Area forecast discussion
National Weather Service Charleston WV
232 PM EDT Wednesday may 22 2013
Synopsis...
a cold front crosses late tonight...followed by another late
Thursday. Upper low crosses early Friday...followed by high
pressure...with cooler and drier air...for the weekend.
&&
Near term /through Thursday/...
230 PM update...
included severe attributes in weather grids with issuance of severe watch.
Previous discussion below...
tracking another middle level wave moving NE across central Ohio/Kentucky as
upper trough drops down into upper MS valley. Most of hi res
models...RUC...and NAM seem to have a grasp on this feature as it
heads across County Warning Area into this afternoon. Used low level moisture convergence
coupled with middle level lift along with current satellite trends for
timing. Cap over area eroding currently just as this feature will
be moving into west and S zones. As such begin to ramp up probability of precipitation across
portions of NE Kentucky and west lowlands next hour or two...over to Kanawha
valley by 20z...with likely probability of precipitation...with scattered wording up to that
point. Not sure how much development reaches into southeast Ohio or along
Ohio River up north. Thus have only low probability of precipitation there initially. Other area
of convective initialization across much east ridges of mountains down to
SW Virginia aided with some southeast upslope flow. In fact models indicate this
convection may try to come off the ridges toward i79 corridor to
coincide with convective band moving through Kanawha valley.
Thus...have some Cat probability of precipitation in this area by 21z. May see a lull west
zones once this moves through until cold front approaches by 00z as
bl tries to stabilize. Question then becomes how active is front
as it moves through tonight. Think southeast Ohio stands to see greatest
coverage of frontal precipitation should afternoon activity stay mostly east and S
of them. Will roll with model consensus with likely probability of precipitation slowly
sliding east overnight with front. Gradually decrease thunder as
well. Surface front becomes rather diffuse and hard to find overnight.
Some low stratus expected with boundary overnight in addition to east
slopes. This may mitigate dense fog. However...across west zones may
see some partial clearing which may allow for some late fog to set
in.
Storm Prediction Center continue slight risk over much of area for this aftn/eve. Model
soundings look similar to yesterday. Should see some decent ml cape
across the area with slightly better flow aloft compared to
yesterday. Think wind is greatest concern again today with downdraft
cape and surface-700 mb Delta Theta values indicative of damaging wind
potential. Freeze level looks to be around 12k with wetbulb heights closer
to 10k...so cant rule out some larger hail. Coded up the strong
attributes in weather grids for this afternoon.
Precipitable waters around 1.5 again today but storm motion/speed may mitigate
water concerns in soggy Coal fields/SW VA/mtns. Will monitor
trends though should ridge tops get going early.
Upper trough tracks east on Thursday with potential secondary front as well.
May see a couple bands of precipitation move through with some lulls in
in between...especially in morning. Surface instability a little low
but steepening lapse rates may bring a small hail concern in the
afternoon.
Inherited temperatures overall looked rather good and only needed some
minor tweaks. Should be cooler tomorrow as upper heights fall.
&&
Short term /Thursday night through Saturday/...
unsettled weather slowly diminishes Thursday and Friday...as upper
trough...and associated cold front sweeps across the region. This
will keep a chance for showers and thunderstorms in the forecast for
the start of the short term period. The storms may contain some
stronger wind gusts as there will still be moderate winds aloft. No
severe weather is expected Thursday and Friday at this time.
A drier...and cooler air under northwesterly flow...will take hold
for Friday through Saturday as the upper trough pushes east. Colder
night seems to be Friday night...generally in the lower 40s
lowlands...ranging to the middle 30s higher elevations...particularly
Saturday morning...enhanced by radiational cooling per good
clearing...and light surface winds
High pressure builds from the north Friday into the weekend. Some
fog development possible early Saturday morning.
&&
Long term /Saturday night through Wednesday/...
have generally followed wpc thinking for this portion of the
forecast.
High pressure will be in control of the weather across the area into
Sunday night. However...models suggest a few weak middle-level
shortwave may move southeast. Believe area should remain dry...with
a few more clouds beginning Saturday night
A warm front will then develop and approach the region on Monday. As
a result...there will be a chance of showers and storms Monday and
Tuesday...mainly during the afternoon and evening hours.
Temperatures on Saturday should be near normal with daytime highs in
the 70s across The Lowlands...with 60s across the higher
elevations. As the high pushes east on Sunday...expect temperatures
to warm to slightly above normal values Monday and Tuesday.
&&
Aviation /19z Wednesday through Monday/...
mountain rain showers/thunderstorms and rain through afternoon aided by heating and southeast low level flow. Have
tempo groups in for mountain sites for IFR visibility in convection.
Elsewhere...scattered convection increasing in coverage through afternoon as a
middle level impulse moves through with greatest increase pegged c
lowlands and points east. Put some tempo groups for kcrw where
greatest confidence lies. Some damaging wind gusts possible in any
stronger convection which will have to be monitored for tafs.
Maximized coverage around 21z here. Will then follow cold front
traversing across after 00z from west with another band of rain showers and
potential thunderstorms and rain with brief IFR visibility possible. Expect low stratus to
develop overnight...scattered out across west by 12z. Fog tricky tonight and
highly dependent on where it rain and any stratus. For now...have
general MVFR visibility most taf sites. Should it clear out west late...then
some predawn dense fog may develop for khts/kpkb.
Any stratus and/or fog will lift by 13z with low end VFR based cumulus
late morning on. Upper trough crosses tomorrow with increase once
again in rain showers activity and possibly some thunderstorms and rain.
Forecast confidence and alternate scenarios through 18z Thursday...
Forecast confidence...medium to high.
Alternate scenarios: timing and degree of flight restrictions due to
convection this afternoon and tonight could vary...as well as timing
and extent of dense valley fog overnight tonight.
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.
UTC 1hrly 18 19 20 21 22 23 00 01 02 03 04 05
EDT 1hrly 14 15 16 17 18 19 20 21 22 23 00 01
crw consistency h h h h h h h h h h h h
heights consistency h h h h h h h h h h h h
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 M M M
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 M
After 18z Thursday...
IFR conditions possible in early Saturday morning.
&&
Rlx watches/warnings/advisories...
WV...none.
Ohio...none.
Kentucky...none.
Virginia...none.
&&
$$
Synopsis...arj/30
near term...30
short term...arj
long term...arj
aviation...arj
