Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
836 PM EST Thursday Nov 26 2015
dry weather and warmer temperatures can be expected through
Friday. Rain chances return on Saturday with the passage of a
cold front. Colder temperatures are expected over the weekend.
Near term /until 6 am Friday morning/...
higher clouds have started to edge eastward from our region this
evening...yielding a bit of clearing that trends suggest should
last through the remainder of the evening and tonight...so partly
cloudy skies overall continue to look like a good bet. In
fact...layer relative humidity projections really do not start to amplify up until
late Friday afternoon...so radiational cooling tonight should be
decent neglecting other considerations. It is those other
considerations that look to keep temperatures up
Surface pressure gradients should continue to increase with
southwesterly flow continuing through the morning. Mixing from
this should allow for temperatures to stay out of free
fall...yielding lows generally in the 40s across the area. This is
roughly in line with what high temperatures should be this time of
the year. Fries
Short term /6 am Friday morning through Sunday/...
continued southwest flow will help maintain warm temperatures and
dry conditions through Friday. The eastward shift of the cold front
remains sluggish as the upper shortwave trough is prognosticated to
gradually weaken over the Great Lakes due to blocking flow
downstream over the western Atlantic.
The front is expected to gradually drag southward and support likely
probability of precipitation Friday night into Saturday. However...chance probability of precipitation are
maintained for the rest of the weekend as a split flow pattern
initiates and a series of impulses from the upstream large cut off
low potentially stall the boundary over the far south.
Post frontal temperatures will trend closer to seasonal levels.
Long term /Sunday night through Thursday/...
the naefs as well as the latest GFS and European model (ecmwf) deterministic
solutions are in good agreement in the progression of deep cutoff
low pressure across the central Continental U.S. And over the Great Lakes by the
middle of next week. The long term forecast thus is of initially
warm temperatures and likely probability of precipitation with a subsequent cooling to near
seasonal averages after passage of that systems occluded and
eventual cold front. The guidance blend was used in construction
of the long term forecast.
Aviation /02z Friday through Tuesday/...
VFR conditions expected to prevail...although lower ceilings and
rain showers associated with a cold front will advance in from the
west right at the end of the taf period.
Winds expected to stay at or below 10kts from the south tonight.
Low-level wind shear is again possible tonight...although it
appears marginal given that the lower atmosphere should remain
coupled overnight. With lower confidence in the occurrence...decided
to keep low-level wind shear out of the tafs at this time.
Still...winds in the 1-2kft range could Jump Up to 30-40kts from
the southwest at times. Tax
Outlook...Thursday night through Monday/...
restrictions are possible with an approaching low pressure system
Monday night through Tuesday.