Scientific Forecaster Discussion
fxus61 kpbz 130811
Area forecast discussion
National Weather Service Pittsburgh PA
311 am EST Fri Dec 13 2019
precipitation chances return today with a weak disturbance.
Widespread rain is expected tonight and Saturday with crossing low
Near term /through today/...
a shortwave embedded in SW flow aloft is progged to track from the
Tennessee Valley to central/eastern PA today. Mainly slight/low
chances for rain are expected across the region, though the higher
terrain areas across wrn Maryland and nrn WV are expected to be closer to
more favorable upper support and deep layer moisture with precip more
With cold air in place at the sfc, and cooling upslope southeast
flow, a period of light freezing rain is expected across ern Tucker
and Garrett counties. Will maintain the Winter Weather Advisory as
is. Some brief, patchy, light freezing rain is possible across
Preston County through the Laurel Highlands if precip occurs this
morning. If later information indicates higher precip probabilities
in these areas, a quick expansion of the advisory may be needed,
otherwise not enough confidence in this occurrence to expand the
Expect any precip to taper off this afternoon with the passage of the
initial wave, with seasonable high temperatures.
Short term /tonight through Sunday night/...
an upper trough is progged to dig across the central Continental U.S. Tonight,
crossing the upper Ohio Valley region Saturday. A sfc low is expected
to develop across the southeast Continental U.S. In response to the digging upper
trough, tracking along the East Coast over the weekend. Rain should
overspread the region tonight and Saturday in warm, moist advection
and increasing shortwave support. Quantitative precipitation forecast amounts are expected to range
from 1/3 to 3/4 of an inch, so no significant Hydro concerns are
Rain should mix with and eventually change to snow in cold advection
after the sfc low tracks by to our east/NE later Saturday and Saturday
night, though no significant accumulation is expected with the
sfc/boundary layer slowly cooling for most locations, though colder
areas across the higher terrain could see a couple of inches.
Snow shower chances should continue Sunday both with upslope flow,
and a sfc trough across Lake Erie/northwest PA. Moisture in the dendritic
layer is expected to be limited, precluding any more than a coating
of additional accumulation in some areas. Brief shortwave ridging
should return dry weather most of Sunday night, though snow chances
return late with another approaching central Continental U.S. Trough and
associated sfc low.
Long term /Monday through Thursday/...
rain and snow chances increase Monday and Tuesday as the trough and
sfc low track across the region. A reinforcing trough should maintain
low/slight snow shower chances Wed before low level ridging returns
mainly dry weather Thursday. Temperatures should average below
seasonable levels through the period.
Aviation /08z Friday through Tuesday/...
MVFR cig restrictions expected today with increasing moisture and a
crossing shortwave. Any precipitation will be scattered and light
during the day. Further deterioration to IFR or lower is expected
tonight through Saturday with more widespread precipitation
associated with low pressure moving up the coast. Nearly all analogs
show IFR restrictions during this time and 60-80% indicate LIFR
restrictions are likely through much of the weekend.
Maryland...Winter Weather Advisory from 7 am this morning to 3 PM EST this
afternoon for mdz001.
WV...Winter Weather Advisory from 7 am this morning to 3 PM EST this
afternoon for wvz514.