Area forecast discussion
National Weather Service Charleston WV
156 am EDT Wednesday may 22 2013
Synopsis...
cold front approaches Wednesday and moves across Thursday. Cooler
high pressure Friday and the weekend.
&&
Near term /through today/...
130 am update...
no major changes as convection has dissipated for the nt.
1030 PM update...convection winding down across the forecast area
as it drifts NE. Decreased probability of precipitation quicker than previous forecast as
the precipitation ends from west to east.
Previous discussion...
tricky forecast for this afternoon regarding convection potential. Not
seeing much in the way of development along morning outflow low level
as it exits mountains model soundings show area losing cap shortly. Will
allow for isolated development in north mountains on ridges where
developing S to southeast low level flow later this afternoon should allow for
some rain showers.
Of bigger concern is convective line getting going across S Kentucky/Tennessee
with subtle short wave trough. NAM...RUC...and hi res WRF models are picking
up on this and allowing for it to get into County Warning Area late this
afternoon/early evening. Will allow for likely probability of precipitation to encroach using
consensus surface moisture convergence and middle level Omega fields for
general timing. Have this entering west zones by 22z if not a little
sooner...into central zones around 00z...and exiting mountains shortly
after 03z. Model soundings show meager amnts of moisture which is
really the only limiting factor. Models generate 2 to 3k ml cape this
afternoon with relatively low freeze levels amid steep lapse rates. So there
is a hail concern. General flow aloft is rather weak...however
there is somewhat greater of a concern for downbursts given surface to
700 mb Theta diff and amount of downdraft cape prognosticated. Model soundings
show a decent low level dry layer to contribute to this. Coded up small
hail and gusty wind wording in grids. Storm Prediction Center added west half of County Warning Area to
slight risk with it 1630z update.
Things quite down tonight. With nothing to grab hold of for
forcing...elected to Nix probability of precipitation overnight. Some middle and hi clouds may
hamper fog development and will depend on who receives rainfall. Bl
winds also increase late which may keep much of fog at Bay...save
for deeper hollows and mountain valleys.
Things turn active once again tomorrow as upper level trough amplifies
across upper MS valley. Hard to pinpoint forcing to grab hold of until
prefrontal bands encroach later in afternoon. Keep probability of precipitation in chance range
until then. Storm Prediction Center continue to highlight a chunk of County Warning Area in slight risk.
&&
Short term /tonight through Friday/...
short term period starts out with the County Warning Area in the warm sector of low
pressure system that will push east across the Great Lakes region
early in the period. Conditions will continue to be warm and humid
on Wednesday in the southerly flow out ahead of the approaching cold
front and upper trough. Temperatures on Wednesday are not expected
to be as high as on Tuesday...due to expected cloud cover...and
precipitation.
Wednesday will see increased shower and thunderstorm activity as the
cold front and upper trough pushes closer to the area. Several
embedded shortwaves will round the base of the trough...and move
northeast through the area. Still looking like there could be severe
weather on Wednesday...particularly in southeast Ohio...eastern
Kentucky...and WV counties near to the Ohio River as good upper
dynamics...instability...and 0-6km bulk shear of 30+ kts will exist.
Strong/damaging winds...and hail will be primary threats...with
fzlvs prognosticated to be around 11k feet. Cold front will end up
somewhere along/near southeast Ohio zones by 12z Thursday.
Upper trough will push through the area Thursday and
Friday...keeping a mention of showers and thunderstorms in the
forecast through at least Thursday night. Much cooler and drier air
is expected to work its way into the County Warning Area for the weekend as high
pressure across the north builds in.
&&
Long term /Friday 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 /06z Wednesday through Sunday/...
convection is over for the overnight...so the only restrictions to
nocturnal and early Wednesday morning aviation is dense valley fog which
may affect the crw and ekn runways.
A cold front approaching from the west during the heating of the day
Wednesday will contribute to strong convection once again. Any
thunderstorm Wednesday afternoon and Wednesday nt could produce IFR conditions
and very strong wind gusts. Dense Post rain nocturnal valley fog is
again likely in the wake of thunderstorms Wednesday nt.
Surface flow will continue light S to SW at nt...becoming a bit gusty
outside thunderstorms during the day Wednesday. Light to moderate SW flow
aloft overnight will become S to SW Wednesday.
Forecast confidence and alternate scenarios through 06z Thursday...
Forecast confidence...medium.
Alternate scenarios: timing and extent of dense valley fog overnight
could vary...as well as timing and degree of flight restrictions due
to convection Wednesday afternoon and evening.
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 Wednesday 05/22/13
UTC 1hrly 06 07 08 09 10 11 12 13 14 15 16 17
EDT 1hrly 02 03 04 05 06 07 08 09 10 11 12 13
crw consistency h h h h h h h h h h h h
heights consistency h h M M M h M h h h h h
bkw consistency h h h h h h h h h h h h
ekn consistency h M l l l l l M h M M h
pkb consistency h h M M M M M h h h h h
ckb consistency h h M M M M M h h h h h
After 06z Thursday...
IFR conditions possible Wednesday nt into Thursday morning in showers and
thunderstorms...and Post rain nocturnal valley fog.
&&
Rlx watches/warnings/advisories...
WV...none.
Ohio...none.
Kentucky...none.
Virginia...none.
&&
$$
Synopsis...jsh/arj/30
near term...trm/mz/30
short term...sl
long term...jsh
aviation...trm
