Scientific Forecaster Discussion
fxus61 kpbz 201935
Area forecast discussion
National Weather Service Pittsburgh PA
235 PM EST Wed Nov 20 2019
dry weather and a warming trend will continue through tomorrow. Some
light precipitation, mostly in the form of rain, will accompany a
cold front Thursday night and Friday. Another system over the weekend
will provide further rain and snow shower chances.
Near term /through tonight/...
clouds have lifted across southwest PA and northern WV as low-level
mixing has increased, but with decent moisture still trapped beneath
a subsidence inversion and ongoing northwest flow, mostly cloudy
conditions continue. Scattered to broken cumulus have formed across
much of southeast Ohio where the sky was clear earlier.
With high pressure settling into the region tonight and mid-level
ridging building, expect the trend to partly cloudy conditions to
continue into tonight. As wind will be light overnight, some patchy
mist may form again towards morning, especially in areas that can
stay mostly clear. Seasonable temperatures mostly around freezing are
Short term /Thursday through Friday/...
dry weather continues for much of Thursday as the mid-level ridge
axis moves through and as surface high pressure pulls east. A
dampening shortwave rides across the upper Midwest into the Great
Lakes by Thursday afternoon. This will push a warm front northward
across our region. As a result, developing southwest flow/warm
advection will help push temperatures back into the 50s for much of
the cwa, slightly above normal for this time of year.
The warm advection will also bring an increase in clouds through the
day in advance of a cold front. This boundary will cross during the
late Thursday night/Friday morning period. With the weakening
shortwave sliding north of our cwa, and the upper jet positioned
such that the best upper level divergence lies to our south, it
appears that support for lift splits around our region. Will
continue with mainly likely pops for the expected light quantitative precipitation forecast event.
Precipitation will remain liquid into Friday afternoon, before
temperatures aloft become cold enough to allow for snowflakes later
in the day. No accumulation is expected.
Thursday night will feature mild temperatures ahead of the front.
Temperatures will initially drop on Friday behind the front, before
steadying out during the afternoon hours.
Long term /Friday night through Tuesday/...
Friday night will feature mainly dry weather under transient ridging.
A stronger shortwave arrives in the middle Mississippi Valley by
Saturday morning and lifts toward our region by the evening hours.
This will bring another round of rain and snow showers to the region
through Saturday night. The weak associated surface low will continue
to dissipate as it crosses Saturday night, with a new coastal system
forming thereafter. Quantitative precipitation forecast amounts will remain minor, with values
generally around a quarter-inch of liquid or less. Any snow
accumulation would be very minor and mostly limited to nighttime
After isolated showers depart Sunday morning, high pressure will
then provide mainly dry weather through Tuesday. Temperatures will
begin to trend a little above normal with generally flat west-southwest flow
aloft. The end of the extended period may feature a strong low
pressure system lifting across the western Great Lakes next
Wednesday, with the possibility of strong wind gusts. This possible
system will need to be watched closely, as it would occur on one of
the busiest travel days of the year.
Aviation /19z Wednesday through Monday/...
MVFR to low VFR ceilings will continue over the next few hours as
abundant low-level moisture is trapped underneath a Stout inversion
with a light northwest wind.
The sky may gradually begin to clear out this evening as ridging
builds into the area and the wind begins to back to a more westerly
and then southerly direction. Fog development is possible overnight
given low-level moisture and low wind initially, but southerly wind
should pick up towards dawn, limiting fog development. Have left out
of taf package due to low confidence at this point.
more widespread restrictions are expected late-week with a frontal