Area Forecast Discussion
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FXUS61 KPBZ 220922

Area Forecast Discussion
National Weather Service Pittsburgh PA
522 AM EDT Sun Apr 22 2018

High pressure will provide dry weather and seasonable
temperatures into Monday. Rain chances return by Monday night
with approaching upper level low pressure.


Minor adjustments to sky cover and hourly T/Td at 520 AM,
otherwise the forecast is on track.

Previous discussion...

Weak troughing aloft, as well as RRQ jet dynamics, are
responsible for the sheath of mid and high clouds across the
area. The departure of the upper support plus dry advection from
the north will help to gradually shunt the clouds south of the
region with time, such that most areas should enjoy a mostly
sunny afternoon. Tonight will be mostly clear as well, as a
mid-level ridge axis crosses overnight.

Warm advection will be fairly modest today, if present at all,
but temperatures should be able to achieve seasonable levels
both today and tonight.


An upper low will slowly churn across the lower Mississippi
Valley and then the Tennessee Valley by Tuesday morning, before
lifting northeast and arriving in our area as a degenerating
open wave Tuesday night. The models are in decent agreement
with this scenario, with still some minor details on the arrival
of moisture and isentropic lift. The arrival of light rain
looks a bit quicker now though overall, and have reintroduced
small PoPs to the southern counties Monday afternoon. Increasing
rain chances Monday night then lead to at least likely PoPs
areawide Tuesday and Tuesday night as the disturbance crosses.
Low level southeast flow into the ridges during these latter two
periods will lead to higher rain chances and QPF overall. The
better moisture tap and forcing will lie off to our east and
southeast however, closer to the Blue Ridge.

Temperatures will max out a few degrees above climatology Monday
before the rain arrives. Cooler temperatures due to the clouds
and rain are figured for Tuesday.


A followup shortwave will kick a cold front across the region on
Wednesday, keeping temperatures a shade below normal into
Thursday. Cannot rule out a few snowflakes mixing in Wednesday
night/Thursday morning behind the front, as 850 mb temperatures
could drop below 0C once again. A dry interlude is possible
Thursday afternoon/evening in brief surface ridging.
Precipitation chances return Friday and Saturday as another
shortwave arrives. Some model solutions close this off into an
upper low over or near our region, while others are more
progressive. In any case, below normal temperatures should


Sfc high pressure should maintain VFR conditions through the TAF
period as dry advection and ridging aloft gradually erode the
mid level cloud cigs from N-S.

Periodic restrictions are likely Mon night through Wed with slow
moving low pressure.




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