Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
1008 am EDT Friday may 22 2015
some showers will accompany a cold front across the region today.
Sub average temperatures will linger into Saturday...then warm
rapidly for the remainder of the Holiday weekend.
Near term /through tonight/...
with 10am update...have updated chances of precipitation based on
current radar trends. Light showers across northwestern
Pennsylvania are diminishing as the morning continues...but with
additional heating expected this afternoon...showers are expected
to develop once again along the encroaching cold front.
Cold surface ridging will build in the wake of the front with a
clearing sky and diminished wind...hence radiational
cooling tonight with dew points dropping into the upper 20s and
Temperatures are projected at or just below freezing expected
across the I-80 corridor. Southward and over the ridges...middle 30s
are expected...with locally freezing temperatures in elevated valleys.
Widespread frost is thus anticipated and a frost advisory was
issued to accompany the freeze warning for the I 80 counties.
Short term /Saturday through Monday/...
high pressure will gradually move east by Saturday night with a
gradual warming trend. Temperatures will recover toward seasonal
norms. Upper level ridge will begin to build across the
southeastern states Sunday with warming temperatures and gradually
increasing clouds. By Sunday night and Monday dew points will be
on the increase...with a developing warm front moving into the
Great Lakes. New models trending best moisture and lift north into
New York state Monday...but for now have left chance probability of precipitation across
the region with increasing low level instability. A warm and
increasingly humid Memorial Day is in store.
Long term /Monday night through Thursday/...
southwest flow is prognosticated to develop through most of the period.
Weak crossing shortwaves embedded in the flow are expected to keep
periodic chances for showers/storms in the forecast. An upper trough
is prognosticated for a late week passage with better focus for precipitation.
Used tweaked wpc ensemble based guidance to smooth out some model
differences. Temperatures should average 10 to 15 degrees above
Aviation /14z Friday through Tuesday/...
a weak cold front accompanied by scattered showers will cross the
region this morning followed by an afternoon increase in VFR
altocu...cu. Maintained a tempo or vicinity shower mention in the
tafs. Nevertheless...only local restrictions are expected with a
wind veer to the northwest.
Outlook.../Saturday through Tuesday/...
weak disturbances could bring restrictions late Monday and Tuesday.
Maryland...frost advisory from midnight tonight to 9 am EDT Saturday for
Ohio...frost advisory from midnight tonight to 9 am EDT Saturday for
PA...freeze warning from midnight tonight to 9 am EDT Saturday for
Frost advisory from midnight tonight to 9 am EDT Saturday for
WV...frost advisory from midnight tonight to 9 am EDT Saturday for