Scientific Forecaster Discussion
fxus61 krlx 230740
Area forecast discussion
National Weather Service Charleston WV
240 am EST Thu Feb 23 2017
unseasonably warm today and Friday. A strong cold front crosses
first thing Saturday morning, followed by cooler weather for
Near term /through tonight/...
as of 230 am Thursday...
In the warm sector today with areas of morning fog. Column
humidities still have maxima meaning clouds should linger
through a good portion of the day. May even see a scattered
sprinkle or shower.
A little instability this afternoon may result in some cumulus
build up, but largely should avoid any thunder.
Clouds on the decrease tonight as drier air moves overhead as
the warm front moves well to the north.
Short term /Friday through Saturday/...
as of 310 PM Wednesday...
Models continue to slow down frontal passage. Latest European model (ecmwf) and
NAM guidance having the front near the Ohio River by 12z
Saturday and the GFS continues to bisect WV with the front by
that time. I have held off on pop until a few hours later than
previous forecast, with categorical pop in the Ohio Valley
between 6z - 7z, but this may still be a bit early.
The main concern with this front will be the possibility of
isolated damaging wind gusts in convection. Overall,
instability is rather weak, with NAM and GFS indicating anywhere
from 300 to 600 j/kg of cape with the highest values in the
Ohio Valley. However, wind shear values are very impressive with
65 to 70 knots of 0 - 6km bulk shear. Also, upper trough turns
slightly negative as it crosses the region and 700mb to 500mb
lapse rates increase to 8c/km. It is possible that we could see
a weakening qlcs entering the Ohio Valley by early Saturday
morning. With the impressive wind shear and modest instability
in the Ohio Valley, there is a chance that convection could
bring some strong wind gusts down to the surface. With the
overnight timing of the front though, the threat for damaging
winds will be low, but isolated damage and power outages will be
possible in the Ohio Valley and that threat will decrease
heading east across West Virginia.
The cold front clears the area on Saturday and strong cold air
advection pushes in behind it. There may be enough lingering
moisture with the upslope northwest flow behind the front that the
mountains squeeze out a few snow showers.
Long term /Saturday night through Wednesday/...
as of 315 PM Wednesday...
Start off the long term with high pressure over the region, but
this will be short lived as zonal pattern is set up across the
U.S. Guidance is in a little better agreement with southern
stream wave pushing across the area on Monday. This will be the
first of what looks like several systems moving through the
progressive pattern next week.
Aviation /08z Thursday through Monday/...
as of 1230 am Thursday...
Could not state the forecast any better than the previous
shift, so here it is: a low confidence aviation forecast
tonight given the battle waging between stratus and fog
formation. I feel fairly confident on ceilings improving as the
evening progresses given the low level flow turning more
southwesterly. Given the amount of low level moisture in place
combined with low dewpoint depressions and a wet ground...any
place could fog pretty quickly this evening if there are any
substantial breaks in the clouds. I've allowed for some IFR vsby
in fog to develop where some breaks in the clouds are more
likely to occur, from heights- crw-ekn. Some weakly forced showers
may develop toward morning along and west of the Ohio River
which will bring ceilings down once again into MVFR and possibly IFR
across southeast Ohio through 15z. These showers will tend to
lift northeast as the day progresses, however, chances are too
small to include in tafs attm. Otherwise expect some 3 to 4
thousand foot stratocu across the area through the afternoon.
Surface flow will be light south beneath light to moderate
Forecast confidence and alternate scenarios through 06z Friday...
Forecast confidence: low tonight. Medium for Thursday.
Alternate scenarios: dense fog may be more prevalent should
clouds break more than forecast.
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 Thursday 02/23/17
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 M l l l l l M M M M M l
heights consistency l l l l l l l l M M M M
bkw consistency M M M M M M M M h h h M
ekn consistency M M M M l l l M M M M l
pkb consistency h M h M M M M h M M h M
ckb consistency M M M l M l l l M h h M
After 06z Friday...
no widespread IFR conditions are expected at this time.