Area Forecast Discussion
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FXUS61 KPBZ 262202 AAA

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
502 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.


500pm update...Only very minor changes to previous forecast.
Most noticeable will be the modifications in sky cover later
this evening over the south. Sped up the onset of mid-clouds in
line with latest operational and hires guidance. Temperatures
were adjusted with the latest guidance as well.

Previous discussion...
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. TAx


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


VFR forecast overnight, as high and mid clouds will slowly increase
from the southwest. A warm front will bring MVFR clouds to the
area Monday morning. There is a risk for showers with the
boundary, but have decided to leave out mention with current
forecast due to the scattered nature expected. Any showers that
do fall, are not expected to bring restrictions.

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




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