Area Forecast Discussion
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FXUS61 KPBZ 251804
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
204 PM EDT Sun Jun 25 2017

.SYNOPSIS...
Upper low pressure will maintain cooler temperature and a periodic
shower chance for the first half of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Mid-level temperatures look to fall off another 4-5C by through
the late afternoon and evening hours as a mid-level short wave
crosses the area concurrent with peak heating. A fairly vigorous
upper jet streak will be transiting likewise, and the
combination of DPVA, right entrance region upper divergence, and
increasing lapse rates will yield a good combination of forcing
for ascent and instability. This will at the very least
generate a marked uptick in cumulus development along a boundary
that moves through this afternoon. The mitigating factor will
likely be fairly lean layer moisture. However, given the
instability profiles, 12z sounding convective temperature of 71F
that should easily be eclipsed, and hi-res model depictions,
isolated showers with the passing short wave seem like a fairly
good bet and were added to the forecast for most areas.
Furthermore, model soundings suggest wet bulb zero heights
falling off toward 5 kft, which would favor some small hail
development in the more vigorous updrafts.

With cold advection underway through the day through the column,
high temperatures will be largely restricted to several degrees
below normal.

Even with the cold pool overhead, stabilization should occur
fairly efficiently overnight due to dry air, a weakening wind
field, and loss of favorable jet streak dynamics. This should
allow temperatures to fall off rapidly with the lower dewpoints
in place, resulting in low temperatures well below normal. Fries

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
Mean troughing will remain across the area through the short
term period. This combined with the passage of a more vigorous
mid-level system will allow for rather unsettled conditions with
scattered showers throughout the period. Likewise, with mid-
level cooling, lower convective temperatures, and subdued 850 mb
temperatures, even with decent mixing, surface temperatures will
remain well below normal. Fries

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
The pattern rapidly evolves to favor flat ridging moving toward
the Appalachians by the latter half of the work week. However,
the lack of deepening of the system that shifts toward the upper
Mississippi Valley combined with a fairly weak subtropical ridge
off the southeastern U.S. coast will mean moisture advection
should occur fairly readily over the flat ridge. As such, while
a short period mid-week looks dry, humidity and thunderstorm
chances should return with warmer air later in the week. Fries

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
VFR conditions will continue through the period with diurnal cu
and gusty winds diminishing with the loss of heating/mixing
tonight. Scattered showers are possible, mainly in the vicinity
of the northern terminals, as a shortwave passes through the
upper trough and temperatures continue to cool aloft. The same
can be said for tomorrow.

.OUTLOOK...
Brief restrictions are possible with showers and scattered
storms tomorrow and Tuesday with the passage of the upper
trough axis.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...None.
PA...None.
WV...None.

&&

$$


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