Area Forecast Discussion
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FXUS61 KPBZ 261853

Area Forecast Discussion
National Weather Service Pittsburgh PA
153 PM EST Sun Feb 26 2017

High pressure will bring clearing skies this evening. Rain
chances return with a weak crossing disturbance Monday, and with
a Tuesday warm front. A late Wednesday cold front will return
wintry weather for the last half of the week.


High pressure at the surface is building in from the southwest.
Lingering flurries will taper down quickly this afternoon as
heights build and flow backs to the southwest. By late this
afternoon, mostly sunny skies should be seen through a majority
of the forecast area. Temperatures are expected to reach near-
normal values this afternoon, aided by increased insolation.

Mostly clear skies will carry into the night under high pressure
at the surface. Increasing southwest flow aloft will advect
moisture back into the region by Monday morning. This will first
manifest as high clouds residing across our southern zones by
daybreak. Low to mid-level moisture catches up by midday monday,
and increasing isentropic lift should provide enough support for
showers to develop. Could see a light mix right at the onset of
the showers, but with dew points and temperatures increasing
quickly, rain will be the dominant precipitation type. Will
continue to cap PoPs at chance as the warm front is transient
and the upper-level moisture quickly evacuates eastward.


Warm advection generally characterizes the entirety of the short
term forecast. The weak warm front that will have moved
northward on Monday will continue its northward migration on
Monday night. The area should enter the warm sector on Tuesday.
This will result in well above normal temperatures returning to
the area. However, the regime this week is far different when
compared to last week. Whereas ridging was present almost all of
last week, this week will be characterized by deep high speed
southwesterly flow aloft. As such, with substantially higher
PWATs in place and ill-timed short waves embedded in the flow,
fairly quick hitting and copious rain-making showers will be
likely throughout the short term period.

By the time Wednesday rolls around, the large scale pattern
looks to evolve such that the upper trough that will have been
anchored to our west will start to eject eastward. This will
drive a surface front toward the CWA by Wednesday night. Decent
instability is present with the front as well as very strong 0-6
km shear. As such, some gusty storms will be possible, however
given the lack of consistency on the frontal timing, it`s
probably a bit early to accurately assess severe potential.


Cold advection will be underway as the cold front drives through
and exits the area on Wednesday night. Timing amongst the
guidance has become more spread as compared to previous model
cycles, so while confidence in the passage is still high, timing
is not. However, all areas look to be cold enough in the
majority of the atmospheric column to support snow shower
chances in northwesterly flow by Thursday.

Guidance continues to favor a wave dropping toward the area
Thursday night into Friday with decent enough agreement between
the GFS and ECMWF to run with likely PoPs during that juncture.
Still with the 12z runs today, the column maintains a cool
enough profile with its passage to support all snow, and given
the QPF and temperature fields, an accumulating snow somewhere
in the region does now seem likely.

Moderating temperatures and drier conditions will be favored
toward the weekend as the upper trough that will have resided
over the area late in the week starts to lift out. Fries


Light snow showers are tapering down east of KPIT and should
cease to exist by 3pm. Mid-level cloud deck is eroding quickly
as high pressure builds in from the southwest. Clear skies will
be left in the wake. Winds will back slightly to the southwest
through the evening, but should generally remain 10kts or less.
High clouds will then increase late tonight into early Monday. A
warm front will return the possibility of showers Monday, but
little to no restrictions are expected with this activity.

Restrictions will be possible again Tuesday morning as the next
weather system impacts the region.




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