Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
636 am EDT Wednesday Aug 27 2014
weak cold front crosses this afternoon into tonight. Weak high
pressure dominates Thursday and Friday. Hooter and more humid
Saturday. Deeper moisture Sunday associated with disturbance aloft.
Near term /through tonight/...
synoptically...surface front currently crossing Northwest Ohio and north
Indiana. Anticipate the front reaching northwest County Warning Area around 15z...crossing
the Ohio River 19z-20z...all the while weakening as it sinks south.
Have best chance of probability of precipitation along the front during the
afternoon...gradually fading into tonight. Front looks to clear County Warning Area
to the south...but enough moisture remains to kept slight chance
probability of precipitation in southern quarter of County Warning Area through the night. Based on forecast
soundings...expect low stratus deck to develop in mainly WV/Virginia
portions of County Warning Area overnight with light north/northwest flow in the boundary
Met continues to perform well on high temperatures in this pattern...so
leaned that way...cooling highs maybe a degree average across County Warning Area.
Used a consensus blend for lows...cooling the north a touch and
warming the south.
Short term /Thursday through Friday night/...
still thought the 00z NAM solution was a bit quick/fast drying out
the low level moisture...left in the dew point gradient associated
with the weakening front. So will hold onto a slight chance probability of precipitation in
some of our southern WV and southwest Virginia counties Thursday
morning...mainly bkw on SW. By afternoon...will have that slight
chance probability of precipitation lingering for a shower or storm just in our 2 Virginia
counties Thursday afternoon. Certainly the further north/northeast
on Thursday...the drier the air.
The 500 mb ridge axis moves over US on Friday...so we lose the northwest
flow aloft. At or below 850 mbs though the weak flow is somewhat southeast and
upslope into our eastern slopes. Will continue the chance probability of precipitation
Friday afternoon from our Greenbrier valley on SW in the southern WV
mountains to SW Virginia.
The only chance made to Saturday was to increase maximum
temperature. The last of the dry air that was shoved on the way
down into the deep south will return NE...through our vicinity on
Saturday. 850 mbs temperatures near 20c.
Long term /Saturday through Tuesday/...
on the Wednesday morning graveyard shift...enough consistency with
the 00z models to jump into the start of the long term...and
increase probability of precipitation to 60 percent/likely for much of our County Warning Area for Sunday.
No front or well defined surface system...but middle level disturbance
rides northeast through our vicinity on Sunday with deep moisture.
Previous discussion below
Leaned toward wpc with some tweaks during the long term period.
Models in good agreement with persistent northwest flow backing to
southwest by the start of the period as upper ridge axis moves off
to the east. This will allow a continued good moisture feed into the
area through the period...with at least a slight chance of precipitation
for much of the time. Continued middle/high chance probability of precipitation Sunday and into
Monday as one front approaches and brushes by the area to the north
during that time frame. Tuesday appears drier at this point in time
before another cold front approaches Tuesday night.
Aviation /12z Wednesday through Sunday/...
fog has been a bit more sporadic this morning than last.
Anticipate any remaining fog dissipating by 13z. VFR conditions
should be in place today. As a cold front approaches from the
northwest...will see some showers and maybe a rumble of thunder...mainly
across western County Warning Area today. Have mention of thunderstorms in the vicinity at pkb and heights. May
need to expand it farther east based on trends later this
afternoon. Did not include any restrictions with the precipitation...but
cannot rule out the need for an amendment/tempo should a cell
approach a terminal this afternoon/evening.
Forecast soundings indicate some low stratus tonight...especially
across the mountains and into the eastern WV lowlands. Farther
east...clouds could scatter out and some fog would be possible.
Overall fairly low confidence on exact low stratus vs. Fog line.
Forecast confidence and alternate scenarios through 12z Thursday...
Forecast confidence: medium.
Alternate scenarios: timing and density of fog/low stratus may vary
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 h h M h h h h h h h h h
bkw consistency h h h h h h h h h h h h
ekn consistency l l l h h h h h h h h h
pkb consistency M M M h h h h h h h h h
ckb consistency M M h h h h h h h h h h
After 12z Thursday...
local IFR in valley fog early Friday morning. IFR possible in