Scientific Forecaster Discussion
fxus61 kpbz 210546
Area forecast discussion
National Weather Service Pittsburgh PA
1246 am EST sun Jan 21 2018
warming temperatures and patchy light rain will be interrupted
by a Monday night cold front.
Near term /through tonight/...
changes for the midnight update were cosmetic in nature - forecast
of increasing stratus and light rain/drizzle remains on track.
Warm, moist advection will continue today over the upper Ohio region
as the area is in the broad eastern flank/warm sector of deep low
pressure emerging from The Four-Corners region. No real changes
were needed for the near term forecast as chances for light rain
were maintained with a temperature forecast about 10 degrees
above the averages.
Despite abundant cloud cover, condensational heating from the
increasing boundary layer dampness will escalate the melt of the
remaining snowpack and aid the rot of river ice before more widespread
rain arrives late Monday. No flood-headlines are thus anticipated.
Short term /Monday through Wednesday night/...
the aforementioned low is projected to deepen as it digs toward
the Great Lakes through Monday. Warm but damp weather can thus be
expected over the immediate area until that system pulls a cold
front across the upper Ohio on Monday night. Precip probabilities
for Monday were adjusted for warm frontal positioning, a change
which features likely numbers(albeit still for light rain) for
northern zones during the morning followed by a transitional
period as the low to the west matures.
The low is projected across the Great Lakes by early Tuesday
with more widespread rain anticipated locally with cold frontal
passage on Monday night. Categorical pops were maintained and
quantitative precipitation forecast is still limited to a half inch or less as per rapid system
progression and dry slot encroachment. That quantitative precipitation forecast limitation and
timing, along with the prior reduction in snowpack should alleviate
broad flood issues.
Seasonable temperature in the wake of the front is expected to
change rain showers to snow on Tuesday with upper support via
The Crossing mid level trough. Progression, a relatively warm
boundary layer, and an ice-choked Lake Erie should limit
accumulation potential before snow shower chances taper off
with building high pressure on Wednesday.
Long term /Thursday through Saturday/...
building high pressure in advance of another low emerging over
the plains is likely to dry and warm conditions before rain
chances return for next weekend with the advance of that
Aviation /06z Sunday through Thursday/...
degraded conditions (mvfr and eventual ifr) can be expected
throughout the taf period as moisture advection continues today
on south-southwest wind.
restriction potential continues for the first half of the week
with the approach and passage of a frontal system.