Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
555 am EDT Friday Jul 25 2014
high pressure and weak winds into Friday. Strong warm air advection
Saturday. A series of disturbances in a west/northwest flow aloft
with rounds of convection mainly Saturday night through Sunday night.
Near term /through tonight/...
VAD winds at 925 mb blowing a bit stronger at 08z...than was
figuring. Krlx for example was 15 to 20 knots. But still figuring on
it to be weakening through dawn. Have areas of fog or low stratus
clouds in the western slopes...mostly from Sutton area on S and SW
to the tug Fork border with eastern Kentucky. Some evaporating/
shrinking areas of low clouds still possible at 13 to 14z in these
western slopes areas.
Over southern mountains...also figuring on patches of fog and low
clouds through dawn...then lifting a bit sooner into scattered
Further west and north...in the cooler air...maybe some patchy fog
along waterways 11-12z.
Have subsidence inversion at the top of the mixing layer around 5
thousand feet mean sea level today. With light winds today...figuring on limited
mixing...so did not make any big adjustments upwards in the maximum
temperature forecast for today. Dew points in the south should
still lower a bit this afternoon.
Picturing a fairly pleasant late July Friday evening. Have just
some high clouds streaking in overnight. Any fog during the late
night and early Saturday morning hours should be limited to the
deeper mountain valleys. Boundary layers winds start to increase
06z to 12z Saturday in the Ohio Valley counties.
Short term /Saturday through Monday night/...
there is reasonable model agreement on the mass and quantitative precipitation forecast fields this
period...indicating a very unsettled period. The pattern undergoes
amplification...with the southern edge of the westerlies across the
Ohio Valley transitioning into a mean eastern U.S. Upper trough. One
short wave tracks across the Great Lakes Saturday...dragging a warm
front northeast across the area. Believe the models are on the right
track in keeping most of the convection associated with this front
north of the area...especially as the vigorous southwest to west 850
mb low level jet stays generally to the north at this time. Will put
lower chance probability of precipitation north Saturday...and keep the south dry. With more
sunshine and southerly flow...expect temperatures Saturday to reach
into the middle and upper 80s with increasing humidity.
Saturday night into Sunday night look to be quite stormy and
wet...ahead of a significant cold front that will cross the area
later Sunday night and early Monday. Good upper dynamics from a
vigorous short wave supporting the cold front...will combine with
precipitable waters around 2 inches and a moderate low level westerly 850 mb jet
ahead of the front...to bring widespread showers and thunderstorms.
A few of the storms may be severe per Storm Prediction Center outlook...with locally
heavy rains. However...although the models drag heavy quantitative precipitation forecast amounts
right across our area...if the anticipated mcs's drop southward to
the west of our area per 1000-500 mb thickness orientation...that
would drastically lessen the rain amounts for our area. Thus...will
stick to a prolonged period of probability of precipitation in the likely range. This will
still warrant mention of possible water problems in the hazardous
weather product...along with possible severe storms.
Monday will be the transition day as the cold front exits...with
precipitation decreasing from west to east and much cooler temperatures
overspreading the area.
Long term /Tuesday through Thursday/...
lingering showers are possible as the last shortwave exits the
eastern mountains. Gradually reduced probability of precipitation Sunday night into early
Monday morning. Another cold front approaches the area from the
northwest early Monday morning...keeping the possibility for more
High pressure behind the cold front takes control later Monday
through the middle of next week with near normal temperatures.
Fused a blend of
different guidance...kept warmer temperatures for a muggy Sunday night.
Low turn northwest by Monday bringing cooler pleasant temperatures
during the first half of the week.
Aviation /10z Friday through Tuesday/...
high pressure and weak winds into tonight.
Have widespread fog or low stratus from kekn on SW to kcrw into the
southern WV Coal fields and Buchanan and Dickenson counties in Virginia
for dawn. So even though kcrw has been reporting scattered clouds
during the predawn hours...can still see them getting a ceiling.
Further north and west...only a few patches of fog figured just
along rivers in the cooler and drier air mass along Route 50
corridor...say Uni...pkb to ckb.
In the weak low level flow...figuring low stratus in the Sutton to
crw to heights and Williamson corridor lingering for 12z to 14z...and
breaking up around 14z to 15z.
After a night of fog and low clouds with variable conditions at
kbkw...have low stratus lifting and scattering out over the southern
plateau around Beckley.
After 15z..mostly scattered clouds at 3 to 5 thousand feet above ground level.
After 23z...just high clouds at or above 15 thousand feet above ground level for overnight.
Some IFR in fog may form 06z to 12z Saturday in the deeper mountain
valleys of eastern and southern West Virginia...including Elkins.
Forecast confidence and alternate scenarios through 12z Saturday...
Forecast confidence: medium.
Alternate scenarios: timing the areal coverage of the lingering low
stratus in the western slopes after 12z and how quickly it lifts and
evaporates could 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.
Date Friday 07/25/14
UTC 1hrly 08 09 10 11 12 13 14 15 16 17 18 19
EDT 1hrly 04 05 06 07 08 09 10 11 12 13 14 15
crw consistency l l l l l l M M h h h h
heights consistency l l l l l l M M h h h h
bkw consistency l l l l l l h M M M h h
ekn consistency l l l l l l h h h h h h
pkb consistency l l l l l l h h h h h h
ckb consistency l l l l l l h h h h h h
After 12z Saturday...
IFR possible in rounds of convection Saturday night into Sunday