Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
655 PM EST Wednesday Nov 26 2014
a weaker clipper system crosses the southern Appalachians late
tonight. Colder air with lingering low level moisture Thanksgiving.
High pressure Friday/Saturday. Another system Sunday night/Monday.
Near term /through Thursday/...
precipitation is fizzling out over the central lowlands as the
main energy of the coastal system continues to the northeast. Dry
slot is holding on over the tri state area...and figure it will
remain there without any further eastward progress thanks to low
level cold air advection. Snow has ended in bkw and will lift out
of Rand/Poca in the next 4 to 6 hours after a decrease in
Meanwhile...over the middle Mississippi Valley...a clipper type
system dives into the Tennessee Valley as the upper level low
carves a path into the deep south. With that said...the next round
of precipitation is not far behind for the southern zones tonight.
However...system is frontolytic in nature...and figure that will
go against the quantitative precipitation forecast and subsequent snowfall amount projections.
Through 00z Friday...not expecting more than an inch or two from
McDowell into Rand/Poca counties.
Further to the west...while the aforementioned low pressure system
will slow the cold air advection tonight...850mb temperatures drop
towards the -10c mark across southeast Ohio. Northwest flow brings
the potential for upsloping conditions...and in the colder air
aloft...the chance for snow showers exists all the way back into
portions of southeast Ohio. This will begin after 18z Thursday as
the low level moisture depth begins to increase.
Using a blend of the guidance...manually adjusted the min
temperatures downward tonight over the southern mountains...and
likewise for the afternoon maximum temperatures Thursday. All in
all...not much to the diurnal temperature curve from late this
afternoon until this time tomorrow.
Short term /Thursday night through Saturday/...
hanging on to some probability of precipitation following the clipper type system to start
the short term...than have some enhancement Thursday afternoon and
Thursday night as upper trough passes and colder air oozes in.
Moisture quickly moves out Thursday night as high pressure noses in
from the SW. A weak warm front passes to the west and brings some
clouds late Friday into Friday night as the surface high slowly
heads southeast. Not expecting any precipitation from the warm front.
Saturday will warm back to near normal with south to southwest flow.
Blended in raw consensus for lows. Going a touch cooler than
previous forecast in the higher terrain Thursday night...and then
going with a non diurnal above 3500 feet Friday night. Blended in the
mav for highs.
Long term /Saturday night through Wednesday/...
generally used the European model (ecmwf) ensemble mean for the forecast...with a bit
of the GFS blended in. High pressure slides eastward Saturday night
and Sunday...providing a southerly flow. Next frontal boundary
pushes into the region Sunday night into Monday. Handling of this
front beyond Monday becomes a bit murky. Some models develop a wave
along the front for Tuesday while others push the front to the south
and dissolve it. Will keep some small probability of precipitation Tuesday into Wednesday due
to the uncertainty...but confidence is low.
Aviation /00z Thursday through Monday/...
area between features this Wednesday evening. Lowered confidence
to low because of the area around crw to ckb that saw their air mass
saturated from the East Coast storm...but now the clouds were
thinning. A few breaks may develop this evening...which could cause
the visibility to drop temporarily into the 1 to 3 mile range. Otherwise
still IFR and LIFR over WV mountains due to low stratus and lingering
flurries...drizzle...or freezing drizzle 00z to 12z.
Meanwhile...where air did not saturate on Wednesday...in southeast Ohio and
NE Kentucky...ceilings higher...mostly 3 to 5 thousand feet broken.
Middle deck associated with the secondary clipper like system advancing
quickly over the lower clouds 03z to 06z. Light snow reforming over
southern counties...mostly S of crw...have bkw taf site affected the
most during the predawn hours.
Clipper system exits after 12z...with boundary layer winds finally
increasing and helping to lift the ceilings in WV between 15z to
18z. Have ceilings mostly 2 to 3 thousand feet broken/overcast with scattered
snow showers in the colder air at 850 mbs 18z Thursday to 00z Friday.
Visibility occasionally near 3 miles in snow showers mostly central and northern
WV during that 18z to 00z period.
Forecast confidence and alternate scenarios through 00z Friday...
Forecast confidence: low.
Alternate scenarios: visibility may not drop vicinity crw 00z to 03z this
evening if breaks in clouds do not occur. Visibility over mountain
counties...including bkw...may be more variable overnight than
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 00 01 02 03 04 05 06 07 08 09 10 11
EST 1hrly 19 20 21 22 23 00 01 02 03 04 05 06
crw consistency l l l l l h h h h h h h
heights consistency h h M M h h h M M M M M
bkw consistency M M M h M M M M M M M h
ekn consistency M h h M M M M h h h h h
pkb consistency M M M M M h M h h h h h
ckb consistency h h h h h h h h h h h h
After 00z Friday...
IFR conditions in snow showers may linger overnight Thursday night over