Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
749 PM EDT Thursday Jul 31 2014
upper level disturbances cross the central Appalachians tonight and
Friday. A new upper level trough settles over the middle Ohio
Valley this weekend...and then pulls out early next week.
Near term /through Friday/...
730 PM update...
the few showers across the northwest zones this afternoon and
earlier this evening have dissipated as expected. Overall forecast
is on track...but adjusted probability of precipitation over the far southern zones to
reflect current radar trends/thinking...as some showers and a few
lightning strikes brush the Virginia counties northeastward up towards
the Raleigh County area.
noted a few showers starting to pop up over the middle Ohio
Valley...where the cumulus field is most Stout. Have accounted for
isolated convection this afternoon...dying off early relative to
Otherwise main feature this period is a pair of southern stream short wave features
that move NE across an ever increasing southeast portion of the forecast area
overnight into Friday. WV imagery shows dry slot between northern and southern
streams over the area this morning already shifting northward...allowing
deeper moisture to encroach upon SW Virginia and southern WV. This shift
corresponds with a rising height field as the main upper low just S
of Hudson Bay fills...and the l/west trough begins to loosen its grip
over the eastern Continental U.S..
Have showers and thunderstorms becoming increasingly likely over the
southeastern fringes of the CST area by dawn Friday...and over the mountains by
midday Friday...with an increasing chance over The Lowlands Friday
afternoon. The westward expansion of coverage Friday afternoon will be
mainly driven by diurnal heating. However...at the same
time...under the cloud shield...the stability actually increases
over the mountains...so the chance for thunder there actually
wanes. The last of the S/W/S starts to pull away to the east late Friday
Lows tonight looked like a reasonably compromise of the latest bias
corrected guidance while an all blend seemed to provide a consistent
solution for highs Friday.
Short term /Friday night through Sunday night/...
unsettled weather returns to the area over the weekend. Upper trough
with several disturbances moving through the area to continue
through the weekend. Models continue to keep bulk of
precipitation...dynamics to east of mountains...and continued to
play the trend of higher probability of precipitation across mountains...with chance across
lowlands. With an overall light flow pattern expected...showers and
storms that develop over the weekend will be rather slow moving. The
higher precipitable water will exist to the east of the mountains...so no major
water issues are expected...however...due to the expected slow
nature of storms...repetitive slower movers over any given area
could cause swollen creeks and streams and perhaps urban water
Additional shortwave energy will dig south and east across the area
Saturday night into Sunday...with a frontal boundary pushing east
across the area Sunday night into Monday. Drier weather behind the
front for the start of next week.
Long term /Monday through Thursday/...
high pressure gradually building in from the west for the start of
next week...for a brief break in much of the precipitation.
However...heat and humidity will be on the increase throughout next
week...as southerly flow increases and heights build out ahead of an
approaching storm system...which will spread showers and
thunderstorms back into the area towards the end of the extended
period. Temperatures look like they will finally rise to normal or even
above normal for this time of year.
Aviation /00z Friday through Tuesday/...
VFR conditions are expected to prevail through the evening hours.
A heavier shower to the southwest of bkw may impact that terminal
in the next hour with perhaps MVFR visible.
Ceilings will lower on southeast flow tonight in the southeast mountains...with
MVFR stratocu getting as far northwest as bkw by dawn Friday and then likely
persisting through the balance of the taf period. Showers and
thunderstorms are likely in the mountains from near dawn Friday
through around the 18z time frame...before beginning to taper from
southwest to northeast after 18z. There is a chance for showers
and thunderstorms further west by 18z Friday. Clouds associated with
the upper level disturbance triggering the convection...should
prevent a repeat of the dense valley fog tonight...with visibilities no
worse than MVFR expected.
Forecast confidence and alternate scenarios through 00z Saturday...
Forecast confidence: medium to high.
Alternate scenarios: fog or reduced visibilities late overnight / early
Friday morning may vary from the MVFR currently forecast. Uncertainty
of effects of showers and thunderstorms increases Friday
morning...especially in the mountains.
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 08/01/14
UTC 1hrly 00 01 02 03 04 05 06 07 08 09 10 11
EDT 1hrly 20 21 22 23 00 01 02 03 04 05 06 07
crw consistency h h h h h h h h h h h h
heights consistency h h h h h h h h h h h h
bkw consistency h h h h h h h h M M h h
ekn consistency h h h h h h h h h M M M
pkb consistency h h h h h h h h h h h M
ckb consistency h h h h h h h h h h h h
After 00z Saturday...
no significant IFR conditions expected.