Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
650 am EDT Friday Mar 27 2015
light precipitation and well below normal temperatures will
persist into Saturday morning...with temperatures returning to
normal by middle week.
Near term /through tonight/...
although a surface cold front has moved east of the region...an
upper trough is currently across the western Great Lakes. The trough
will cross the region this evening...bringing a reinforcing round of
precipitation. With extensive cloud cover today and
west-northwesterly winds continuing through the day...temperatures
will be more similar to middle January values instead of late March
values. Nearly all locations will remain in the 30s during the day
and drop into the teens overnight. As a result...many locations will
see snow...although accumulations should generally be confined to
grassy surfaces. Still...an inch of snow would not be unreasonable
north of Interstate 80 and in the higher elevations of PA/WV/MD.
Short term /Saturday through Sunday/...
with the upper trough moving to central Pennsylvania by Saturday
morning...any lingering precipitation should quickly push east after
sunrise. Even with skies clearing Saturday...cold northwesterly
winds will keep highs from rising much above todays values. Winds
will diminish Saturday night as high pressure moves
overhead...allowing for full radiational cooling and yet another
night of lows in the teens. Return flow behind the high pressure
will finally bring some relief from colder temperatures...although
daytime values on Sunday will still remain 5-10 degrees below
normal. Next front crosses the region Sunday night...with models
still varying in exact timing and amount of deep moisture present.
GFS appears to be the fast outlier...and have gone closer to
NAM/sref timing. Raised probability of precipitation from previous forecast...but still do
not have confidence to add likely probability of precipitation anywhere. Sunday night should
finally bring a period of near normal temperatures...meaning that
precipitation should generally fall as rain. Flow differences
between the GFS/European model (ecmwf) result in some uncertainty as to whether
showers will linger into Monday. For now...have gone with chance
probability of precipitation diminishing through the day. Highs on Monday should continue to
creep up a couple more degrees.
Long term /Sunday night through Thursday/...
the longwave pattern will become more zonal in the extended with
temperatures returning to near normal and shortwaves Tuesday
afternoon through Tuesday night and again on Thursday bringing chances
of precipitation to the region.
Aviation /12z Friday through Tuesday/...
MVFR conditions expected to improve to VFR by middle morning as
ceilings lift slightly with increased mixing...with scattered-broken stratocu in
cold northwesterly flow aloft persisting throughout the day. Winds
will remain out of the northwest.
Outlook.../Friday night through Tuesday/...
restrictions will be possible through early Saturday with
troughing over the area...but not persistent or widespread as
moisture is limited. VFR then expected until early Monday morning
as low pressure impacts the region.