Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
609 am EDT Tuesday Jul 22 2014
weak flow continues today. Flow begins to increase tonight.
Moisture increases Wednesday. Cold front passes Wednesday night.
Drier air arrives on Thursday. High pressure in full control Friday.
Near term /through tonight/...
expect today to be the second of our 2 day dog day pattern.
No big changes. Fog is less this morning...as temperatures in many
spots are 1 to 3 degrees milder...compared to 24 hours ago. But
like Monday morning...just as much fog in Ohio as West Virginia.
That weak wind flow continues today...with the warm stable layer at
10 to 15 thousand feet. Will continue to mention a chance pop for mountain
thermals this afternoon into early evening. 700 mb flow begins to
veer to weak west by late in the day...so not figuring on cells
coming off the mountains westward. Also...with upper winds starting
to have a west to east component...some haze and smoke aloft may be
noticed around sunset this evening for the Ohio Valley counties.
Forecast maximum temperatures today are a degree or so hotter than
Another warm and muggy night. With boundary layer increasing in the
Ohio Valley...southeast Ohio may be the warmest overnight. Still
left a slight chance pop through the late night hours over the
southern mountains including bkw. Will not play up any thick fog
late tonight...may be some in the deeper mountain
valleys...depending on leftover clouds. Not figuring on any thick
fog over the western lowlands.
Despite the faster frontal timing...still no pop above 14 percent into
southeast Ohio by 12z Wednesday.
Short term /Wednesday through Thursday night/...
various short-term nwp coming into better agreement with regard to
the quicker handling and progression of the trough/cold front
prognosticated to affect our area Wed/Thu.
Upper trough continues to dig southeastward across the Great Lakes
Wednesday. Associated cold front will be entering Northwest Ohio at 12z Wednesday and
should be nearing Perry County around 21z Wednesday. As such...sped up the
progression of likely probability of precipitation into the northwest zones by the 19z-20z
time frame. Overall organized severe threat appears minimal with
only about 20kts shear. However...with SBCAPE upwards of 2000j/kg
and MLCAPE around 1200-1300j/kg producing el/S of 40-42kft...and
halfway decent middle-level lapse rates for our region...it/S possible a
storm or two may reach severe limits. Strong winds would be the main
hazard...but large hail is a possibility. Not much change with maximum
temperatures from previous forecast for most the WV/Virginia zones but did nudge temperatures
down just a tick across the northwest zones with the earlier arrival of
dense cloud cover. Still expecting upper 80s and a few 90s across
the central and eastern lowlands.
Front will continue southeastward becoming located near the i79
corridor between 00z Thursday and 03z Thursday...and through the forecast area by
09z - 12z Thursday. Have only slight chance probability of precipitation for southeast Ohio by 06z Thursday
with likely probability of precipitation continuing in the mountains...with middle/high chance
probability of precipitation in the mountains and no public probability of precipitation near and west of the Ohio
by 12z Thursday. Also ended thunder chances with the progression of the
front itself. With the quicker arrival of the front...lowered mins
just a bit overall...but particularly over the northwest zones where
dewpoints should be in the middle 50s by the 09z-12z Thursday time frame.
Might also see some brief gusts around 15kts or so with the passage
of the front itself.
The base of the upper trough finally swings across between 12z-18z Thursday
with surface high pressure continuing to build in out of the northwest.
Will keep at least slight to low chance probability of precipitation primarily in the
eastern mountains with a good amount of low level moisture trapped
underneath a strengthening subsidence inversion. Elsewhere...most
lowland locations will probably remain dry with maximum temperatures only in
the upper 70s. A bit of a tough call on sky cover...coded up partly
cloudy skies for the afternoon hours for The Lowlands but some
indication that a fairly extensive cumulus field may redevelop underneath
aforementioned inversion. Ended all public probability of precipitation by 03z Friday with
cumulus dissipating overnight but hanging on longer of course in the
eastern mountains. Lowered mins by a good 4-6 degrees pretty much
across the board with mins mainly in the upper 50s expected for The
Lowlands by early Friday.
Long term /Friday through Monday/...
populated grids with HPC guidance with a few minor tweaks. 500 mb
trough slides east...while at the surface there will be and area of
weak high pressure...with generally dry atmospheric column on
Friday and Saturday. A large occluding system meanders south for
Sunday...as cut-off low develops over the Great Lakes. Both European model (ecmwf)
and GFS in fairly good agreement in playing out this scenario late
in the period for a general upswing in precipitation chances by
Aviation /10z Tuesday through Saturday/...
predawn fog was not as widespread as 24 hours ago or forecast for
this predawn. Though...low clouds are still lurking on the eastern
slopes though at dawn...including the upper Greenbrier valley. So
some ceilings near 1 thousand feet into 14z there...before lifting.
Isolated to scattered slow moving convection over mountain counties
again today...first probably forming 16z to 19z. With middle level flow
starting to veer to west late today...did not include any convection
in ckb to crw tafs. A few showers may linger over southern mountains
including bkw vicinity after dark this evening.
Ceilings 2 to 4 thousand feet broken over mountains near
convection...otherwise clouds mostly 3 to 5 thousand feet above ground level scattered
Some haze aloft likely toward sunset this evening. With increasing
flow overnight Tuesday night...only figuring on deeper mountain
valleys reaching MVFR in fog by 06z Wednesday.
Holding off showers into southeast Ohio until after 12z Wednesday...but
clouds at 4 to 6 thousand feet likely increasing there near 12z
Forecast confidence and alternate scenarios through 12z Wednesday...
Forecast confidence: high.
Alternate scenarios: coverage of mountain convection this afternoon
may be only isolated rather than scattered.
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 11 12 13 14 15 16 17 18 19 20 21 22
EDT 1hrly 07 08 09 10 11 12 13 14 15 16 17 18
crw consistency l l M h h h h h h h h h
heights consistency l l M h h h h h h h h h
bkw consistency M M h M M h h h h h h h
ekn consistency l l l h h h h h h h h h
pkb consistency l l h h h h h h h h h h
ckb consistency M M M h h h h h h h h h
After 12z Wednesday...
IFR conditions are possible with frontal convection arriving from
northwest to southeast for Wednesday afternoon into evening.
Secondly...IFR possible later with Post frontal ceilings especially
over mountains late Wednesday night into early Thursday morning.
pkb ASOS is not sending a complete observation. National Weather Service techs will be
looking at the problem today.