Scientific Forecaster Discussion
fxus61 kpbz 182212
Area forecast discussion
National Weather Service Pittsburgh PA
512 PM EST Thu Jan 18 2018
high pressure brings dry weather and a warming trend into
Saturday. Light rain chances return later in the weekend, before
a cold front brings more widespread rain by Monday.
Near term /until 6 am Friday morning/...
clear skies should continue through the overnight as high
pressure remains in control. Decoupling is already starting to
occur and wind speeds are falling off a bit. This trend will
need to be watched due to deep snow cover and the potential for
more dramatic temperature fall-offs overnight should be fully
decouple. Warm advection is still occurring off the deck, so
they should keep the ridges warmer than they have been, but in
the lower elevations, another cold night is in store. Fries
Short term /6 am Friday morning through Saturday night/...
mid-level flow becomes increasingly zonal during this period as
troughing pulls east of New England, while an upper low tracks
across the deep south. This will allow temperatures to continue
to moderate through Saturday, with highs reaching the 30s on
Friday and the 40s on Saturday. These temperatures will allow
for some snowmelt during the day, while subfreezing temperatures
Friday night will help to slow runoff a bit. Clouds will begin
to increase on Saturday as southwest flow brings a bit more
moisture into the area.
500 mb heights may begin to creep upward Saturday night in
response to a trough digging into the Western Plains. Over our
area, weak isentropic lift may work with sufficient moisture to
allow for the development of light rain or drizzle Saturday
night. Quantitative precipitation forecast will remain a few hundredths of an inch at most at
this point. Soundings indicate too much warm air for snow.
However, depending on how quickly temperatures drop during the
evening, some light freezing rain or drizzle may be possible
near and north of I-80 as values may straddle freezing. This is
a low probability event for now and an severe weather potential statement mention is not
Long term /Sunday through Thursday/...
forcing remains weak on Sunday, and the threat of light rain or
drizzle will continue into the night. The models continue to
lift a strong, vertically stacked low center across the upper
Midwest and Great Lakes Monday and Tuesday, although speed and
timing differences remain. It still appears that the highest
precipitation probabilities remain Monday and Monday night, and
in the form of rain, given the continued above normal
temperatures. Quantitative precipitation forecast may not be excessive given the occluding
system and the stretching out of the surface cold front, but
rainfall amounts will still need to be monitored given the
melting snowpack and river ice concerns.
Seasonable temperatures return behind the front on Tuesday, with
some lingering rain or snow showers. Dry weather is figured for
Wednesday and Thursday with developing high pressure.
Aviation /22z Thursday through Tuesday/...
VFR will prevail through the period, save for a few clouds in
the vicinity of kfkl and kduj as shortwave passes to the north
West-southwest wind will remain gusty through the afternoon, diminishing
with the loss diurnal heating/mixing at sunset.
restriction potential returns over the weekend with approaching