Scientific Forecaster Discussion
fxus61 krlx 091133
Area forecast discussion
National Weather Service Charleston WV
633 am EST Mon Dec 9 2019
off and on rain Tuesday ahead of a cold front. Sharply colder
air and snow showers for Tuesday night/Wednesday. High pressure
but cold into Friday. Unsettled for the weekend.
Near term /through tonight/...
as of 625 am Monday...
Brought down the wind gusts as they looked too high, and
increased the pops over the next few hours based on radar
As of 245 am Monday...
500mb flow is now becoming very active, and with the surge of
lower level moisture, rain coverage is expected to be on the
increase going forward. Meanwhile, cold front will push through
the lower Ohio Valley today and into the middle Ohio Valley
tonight. The result is persistent off and on rain for the
northern and western zones in the short term, and a marginal
risk of excessive rain over this area in day 1. Further south,
more likely to get a reprieve in the rain with a brief drier
push of lower level air until the front begins to work through
the County Warning Area. At the Break Point with the short term, the cold air
advection really begins a strong advance into the northwestern
zones of southeastern Ohio by 12z Tuesday.
Short term /Tuesday through Wednesday night/...
as of 210 am Monday...
A low to the north will start this period off spreading rain across
the area due to its associated frontal boundary. Qpfs have come
down a lot since previous forecast runs mainly due to the
increase in speed of the southern stream frontal boundary that
will be draped across the area which will shorten the length of
time this feature rides over over US. During the Tuesday
evening time frame, the cold front will be moving across to the
east transitioning most of the rainfall to snow with very
efficient cold air advection and soundings are in agreement with
this. Frontal passage is set for early morning on Wednesday
where a possibility for a surge of snow showers takes place
with robust frontogenesis available and a low level jet of 60kt
coupled with a strong jet streak, all which will help enhance
some snow development along the band of frontogenetical
forcing. Good upslope flow direction right along the backside of
the cold front will add to accumulations in the mountains as
opposed to The Lowlands. However, the moisture does get cut off
early morning Wednesday for The Lowlands and finally in the
mountains near Elkins and Snowshoe shortly afterwards in the
late morning with possible lingering flurries into the early
Getting a handle on snow accumulations has been really tough
considering quantitative precipitation forecast has been decreasing over time and the frontal
movement has increased. However, there will be a nice window of
opportunity for preferred ice growth although it will quickly
diminish as moisture disappears with colder dryer air getting
filtered in. Since The Lowlands has less of a window of snow
growth, totals are conservative with traces amounts in the Ohio
Valley and up to an inch in The Lowlands of WV. In contrast,
the mountains will have much higher totals from upslope and a
lengthier snow growth window for the higher elevations with
expected totals anywhere from 1.5 to 4 inches in the highest
peaks. These values may vary of course in later shifts due to
the complexity of this snow forecast.
Long term /Thursday through Sunday/...
as of 230 am Monday...
High pressure will dominate until Friday morning when the next
system approaches the area from the southwest. It looks like
models are diverging even more on the track of the surface low
which will make a difference on how much snow or rain occurs.
Regardless, it looks like the area will endure a somewhat
unsettled weekend and then may have a short break afterwards.
Models do hint at another disturbance for the beginning of the
new work week. The take away here is that the weekend has even
more of a chance at being unsettled than previous model runs and
an active pattern starts to arise for the beginning of the
Aviation /12z Monday through Friday/...
as of 625 am Monday...
Cold front approaches from the west this forecast period and
will pass after 03z Tuesday.
Ceilings continue to gradually lower and eventually will have
predominant MVFR values for the bulk of the period with off and
on rain moving through the region. More frequent rain expected
along the river terminals, and the crw-ckb line and east should
get into a break from the rain after 16z today for a few hours.
Regardless, any ceiling improvements to VFR will be temporary.
Visibilities are not forecast to reach IFR for very long at any
of the terminals, and do not feel that the atmosphere will
become soupy in rain due to the strength of the wind. This is
also a reason why ceilings should stay MVFR and not dip into IFR
values either. Brief IFR in a more moderate shower cannot be
ruled out, but the thought is that this would be too short lived
for any prevailing or tempo group at this time.
Forecast confidence and alternate scenarios through 12z Tuesday...
Forecast confidence: medium.
Alternate scenarios: observations likely to bounce in and out of
rain requiring tempos.
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 Monday 12/09/19
UTC 1hrly 10 11 12 13 14 15 16 17 18 19 20 21
EST 1hrly 05 06 07 08 09 10 11 12 13 14 15 16
crw consistency h h M M h h h h l l M M
heights consistency h h h h M h h h h h M h
bkw consistency h h h M h h h l h h h h
ekn consistency h h h h h h h M M M M l
pkb consistency h h M M h l l l M M M h
ckb consistency h h M h l h l l l l M M
After 12z Tuesday...
IFR expected at times Tuesday with rain. IFR possible Tuesday
night and Wednesday in snow showers, most likely in the