Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
252 am EDT Friday Jul 31 2015
dry with high pressure in control today. Weak surface trough
Friday night...followed by a weak disturbance Saturday night.
Series of disturbances continues into next week.
Near term /through tonight/...
no significant changes were needed to the previous forecast. Cold
front to the east of the County Warning Area...with high pressure building in from
the west. Much lower dew points as of late...with much of the area
experiencing dew points in the upper 50s to lower 60s. Still
expecting some patchy fog to develop towards morning in favored
river valleys...but nothing widespread expected at this point with
the somewhat drier air mass in place. Any fog should burn off
relatively quickly this morning.
Overall...mostly sunny day on tap...with overall relatively low
humidity for this time of year. A cold front...at 06z located
across the upper Midwest...will sink south towards the region late
tonight. This may create a slight chance of showers...across parts
of southeast Ohio and northern WV late tonight. However...with an
overall lack of decent moisture...and rather dry air at lower
levels...any precipitation will be light...possibly even in the
form of just sprinkles. Kept a slight chance across aforementioned
areas late tonight...and removed mention of thunder due to overall
lack of forcing/instability. Main effect with front will be a
slight increase in cloud cover overnight.
Short term /Saturday through Sunday night/...
high pressure slowly drifts from the Tennessee Valley eastward or east-southeastward to the
southern Appalachians this period. In the meantime...several upper
level short wave troughs cross. The first exits first thing Sat
morning...having dried up by then. The second crosses overnight
Sat nt into Sun morning. It...too...will be moisture starved and
is not likely to produce any precipitation despite the nam12
solution...preferred the gfs40.
The third short wave trough will benefit from low level inflow from the
SW and may be able to bring precipitation into the middle Ohio
Valley sun nt. It should also...though...dry up as it pushes
farther east-southeastward...and a stronger short wave trough approaches from the northwest
toward Monday morning.
Other than some lightning...none of these features are expected to
have a significant impact on interests in the forecast area.
Blended in the met guidance for highs Sat and lows Sat nt...and
the mav for highs sun. Lows sun nt were close to a bias corrected
blend. Not much change overall. Have highs sun a couple of ticks
higher than for Sat as 850 mb temperatures climb from around 16c Sat
to 18c on average on sun.
Long term /Monday through Thursday/...
general agreement in the long range concerning overall synoptic
evolution...with an upper level ridge across the southern states shifting
west and a persistent trough building across the east.
However...there is disagreement concerning how much the western
ridge will amplify...which introduces a good bit of uncertainty
into the forecast.
For our area...this uncertainty will yield relatively low
confidence in precipitation forecast as models are having difficulty
resolving spatial and temporal evolution of waves embedded in the
larger scale flow. Regardless...thinking the pattern will become
disturbed enough for some rain/thunderstorms through the upcoming week.
As for temperatures...should see some break in the higher afternoon
readings owing to increased clouds...slightly higher rain
chances...and our increased distance from the western ridge.
Aviation /07z Friday through Tuesday/...
06z Friday through 06z Saturday...
MVFR/patchy IFR valley fog expected in favored river valleys
generally 08-12z. VFR conditions return area wide with light
surface winds after 12z.
Forecast confidence and alternate scenarios through 06z Saturday...
Forecast confidence: medium tonight otherwise high.
Alternate scenarios...timing and extent of fog overnight in
question and highly dependent on boundary layer winds.
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 Friday 07/31/15
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 M l l M M h h h h h
heights consistency h h h M M M M h h h h h
bkw consistency h h h h h h h h h h h h
ekn consistency M l l l l l M h h h h h
pkb consistency h h M M M M h h h h h h
ckb consistency h h M M M M M h h h h h
After 06z Saturday...
River Valley IFR fog possible early Saturday morning.