Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
1025 am EST Friday Nov 27 2015
rain chances return tonight and continue through Saturday night
with the advance and passage of a cold front.
Near term /through tonight/...
no appreciable changes were needed for the late morning update as
lingering high pressure will maintain warm temperatures and dry
conditions for most of the day. Already extensive high cloudiness
via moist SW flow aloft will only increase...with lower cloud and
shower development from the northwest late this afternoon and into
the evening as the front draws near.
Pop timing...with numbers cumulating in likely to categorical
probs...were tweaked using high res and model blend guidance as
the front will sag across the region through the night. With slow
frontal progress and boundary layer saturation...overnight lows were
forecast 10 to 15 degrees above the avgs for zones south of the
i80 corridor...again using the guidance blend.
Short term /Saturday through Monday/...
the front is forecast to continue sagging southward on Saturday...with
NAM again indecisive over the past several runs as to southward progress
with the approach of another shortwave. Better probability of precipitation numbers were
thus focused southward...and maintained through the weekend along and
south of the I 70 corridor as per GFS/ensembles/blends...with
cooler/seasonal temperatures filtering over the northern counties and southward for
the start of the new week.
Long term /Monday night through Thursday/...
model solutions are in good agreement pertaining to the
progression of a deep cutoff low pressure across the central US
moving to the Great Lakes by the middle of next week. The long
term forecast is of initially warm temperatures and likely probability of precipitation
with a subsequent cooling to near seasonal averages after passage
of that system's cold front. The guidance blend was used in
construction of the long term forecast.
Aviation /15z Friday through Tuesday/...
VFR can be expected today...but an approaching cold front will
deteriorate conditions from northwest to southeast this evening.
Outlook...Saturday through Tuesday/...
widespread restrictions Saturday will slowly improve from north
to south in the afternoon as a cold front sinks south.
Restrictions are possible with an approaching low pressure system