Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
841 PM EST Sat Feb 13 2016
very cold temperatures and dangerous wind chill indices can be
Near term /through Sunday/...
no changes were needed for the late evening update as snow shower
potential continues to fade with weakening flow.
Otherwise...the Wind Chill Advisory has been maintained although
building high pressure will continue to gradually degrade the wind
component. No change was needed for the frigid temperature prognosis.
Sunday will be generally dry and continued cold...even though middle
and high cloudiness is expected to rapidly encroach as warm...moist
advection ensues in advance of another shortwave trough. Light snow
may develop near zzv as night falls...chance probability of precipitation were maintained in
Short term /Sunday night through Tuesday/...
shortwave moving east across the Great Lakes will bring warm
advection along with an increase in deeper moisture Sunday night
into Monday. This will give a period of snow especially south of
Pittsburgh with some accumulation possible. Temperatures look to
rise later Sunday night and will push to near the seasonal
Southward digging shortwave in the upper trough and pivoting
upper level jet will support a low pressure system that will ride
northward along the Middle-Atlantic States Monday...followed by
another system on Tuesday. There remain some uncertainty in the
track of this system...with the GFS much faster and less amplified
with the first low than the European model (ecmwf) at this time. Based on National
guidance and current model trends...have opted to side with the
GFS. While warm advection is not as strong as it is on the
European model (ecmwf)...there are some p-type concerns...especially on Tuesday as
the second low pressure moves over the Ohio Valley.
Model soundings...while on the cooler side...support lower snow
ratios Monday night...with the best lift placed below the layer
for efficient snow growth. Thus...the current snowfall forecast
was depicted as such. However...if the quantitative precipitation forecast that is forecast in the
model materializes...snow amounts could reach values for
headlines. At this point...have highlighted these concerns in the
severe weather potential statement.
Temperatures were constructed heavily on the GFS with
consideration for ensemble guidance.
Long term /Tuesday night through Saturday/...
second low will be crossing Tuesday night with warm advection
continuing. Again...p-type issues remain with rain and snow
changing to snow with cold advection Wednesday with the systems
departure. Ridging and a warm up looks to take place by late in
the period. Heavy emphasis was used on the superblend for the long
Aviation /02z Sunday through Thursday/...
still cannot rule out some MVFR or even IFR visibilities in snow
showers...although snow shower coverage should rapidly decrease
this evening. Wind gusts will also diminish with nightfall. Middle
level clouds should scatter out as winds back to the west-
southwest...and the winds will continue to back through the
period. Although high level clouds will move during the day on
Sunday...conditions should remain VFR. Cannot rule out snow
arriving to zzv by 00z Monday...but the odds are low at this time.
Outlook.../Sunday night through Thursday/...
low pressure systems will bring widespread restrictions later
Sunday night through Wednesday.
Maryland...Wind Chill Advisory until 9 am EST Sunday for mdz001.
Ohio...Wind Chill Advisory until 9 am EST Sunday for ohz040-041-050.
PA...Wind Chill Advisory until 9 am EST Sunday for paz007>009-
WV...Wind Chill Advisory until 9 am EST Sunday for wvz001-002-021-