Area Forecast Discussion
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FXUS61 KPBZ 211859

Area Forecast Discussion
National Weather Service Pittsburgh PA
159 PM EST Tue Feb 21 2017

A weakening front may provide a few showers tonight and into
Wednesday. More showers are possible starting Thursday afternoon
due to a warm front. The unseasonable warmth will continue.


Decent upper moisture plume has led to thickening mid and high
level cloud cover through the day. Prefrontal rain band
continues to fall apart as upper level support wanes. The 500 mb
shortwave which is helping to push the boundary is shearing out
over the northern Great Lakes. The front will enter the region
tonight, but will begin to break up as it becomes parallel to
the increasingly zonal flow aloft. While weak southerly flow
remains at the surface, much of the deep moisture will remain
bottled up to our south. This, along with the general lack of
lift, points to continued low PoPs tonight. Have 30ish values in
place for most of the CWA overnight with the expectation of
less than .10 inch over the area. Quite mild overnight, with low
temperatures 5 to 10 degrees above the daily normal MAX values.


Generally zonal flow continues into this period, with more
amplified flow towards the end ahead of the strong system
approaching Friday night. A few showers may linger along the
dying boundary Wednesday morning, before flat ridging provides a
dry interlude Wednesday afternoon through much of Wednesday

Flow begins to amplify Thursday as a strong shortwave begins to
dig over the Plains. The increasing southwest flow will push
moisture and a warm front towards the region with time.
Modest isentropic lift at 300/305K will also support chance PoPs
for showers. Some modest instability of 300 J/kg or less is
noted on model soundings, but elected to hold off on thunder
mention for now.

The unseasonable warmth continues through this period, with high
temperatures consistently running 20-25 degrees above average.
Made only minor modifications to numbers using bias-corrected
guidance. See climate section for details on record high
temperatures this week, some of which could be in jeopardy.


Warm front will lift north of the area Friday increasing
southerly flow into the area. 12Z GFS continues the trend of
slowing down the progression of the strong cold front late
Friday into early Saturday. Delayed timing should allow for
enhanced clearing in the warm sector, and as a result,
temperatures will soar. Have kept with the trend of bumping up
Friday`s highs, although not quite to the MEX numbers.

Will continue with likely PoPs for this boundary, with a chance
for thunder, though the overnight passage may be a bit of a
limiting factor. Temperatures should return to near normal
values, with snow showers as the system departs.

Very broad troughing is then expected through early next week,
with another system progged for passage in the deterministic


VFR conditions expected to persist through the evening with high
clouds on the increase. A low pressure system well north of the
area will bring a weak cold front tonight. This boundary will
result in little more than a few showers, but will lead to an
increase in low-level moisture. This will manifest in lowering
CIGs down to MVFR for most locations by Wednesday morning. A few
locations (FKL/ZZV) could see brief spells of IFR as well.
Any lingering restrictions mid Wednesday morning will see
gradual improvement through the early afternoon.

Restrictions are likely with a Friday night/early Saturday cold


Record high temperatures for climate sites:

            Wed            Thu            Fri
          ---------      --------        --------
PIT       70 (1922,30)   70 (1922)       70 (1875,1906)
ZZV       67 (1992)      64 (2000)       70 (1961)
MGW       70 (1980)      68 (1996)       75 (1975)
DUJ       60 (1983)      63 (1985)       60 (1985)
HLG       57 (1949)      62 (2000)       63 (2016)
PHD       73 (1997)      69 (1975)       66 (1985)




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