Area Forecast Discussion
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FXUS61 KPBZ 210518 AAC
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
118 AM EDT Wed Jun 21 2017

.SYNOPSIS...
The risk for showers and storms return today and will continue
into the weekend. The best chance for widespread activity will
arrive on Friday.

&&

.NEAR TERM /THROUGH TODAY/...
The overnight forecast will be composed using latest
radar/satellite trends and a blend of hires guidance. Rather
vigorous shortwave will swing across Lake Erie and dive
southeastward overnight through PA. The strongest part of the
wave will rotate eastward, meaning the large scale ascent moving
southward will decrease overnight. There is a weak surface
boundary situated in close proximity with the upper level energy
and it will slowly push southward overnight as well. The current
activity has developed ahead of the boundary, fueled by the
aforementioned shortwave, and is moving more to the east,
following the main energy aloft. Will show a slow southward
progression of low chance/slight chance PoPs overnight, but
expect most of the showers to dissipate once the heart of the wave
is gone.


The weak boundary will sag southward overnight, stalling just
north of PIT around dawn.

A stalled front will lay across the middle of the region
through much of the day. This front will become the focal point
for additional development this afternoon. Would expect a
combination of daytime heating, although it may be curbed by
cloud cover, and an afternoon shortwave, to be the trigger to
get showers and possibly a storm to fire this afternoon. The
strength of development would likely be predicated on how much
sun we see. Convective temps will be in the upper 70s, so
sunshine will help to push surface readings to those levels. If
convection does fire, it will move southward late this afternoon
and into the evening with the shortwave driving the surface
boundary to the south. Activity will dissipate during the
evening hours due mainly to the loss of daytime heating.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...
The unsettled pattern continues into Thursday with a shortwave
moving across the area. Again, stuck with low chance pops,
primarily across northern counties. The most active weather
period for the week still appears to occur Friday into Friday
night. Models are in good agreement that another cold front will
enter the region from the west late Friday and move through
Friday night. Showers will overspread the area well ahead of
the surface boundary Friday morning, as a series of shortwaves
move across the southern half of the area. If these waves end up
tracking as forecasted, would think most of the rain for the
first half of the day would be over the south, until the front
arrives. This may help to curb stronger convection with the
boundary. Still much to be worked out for the Friday forecast.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The chance of showers will linger south and east of Pittsburgh
Saturday along the back side of the front, and an additional
shortwave could spark showers on Sunday. High pressure should
build in for Monday and Tuesday, resulting in quiet weather.
Temperatures will remain below normal through the extended
forecast.

&&

.AVIATION /05Z WEDNESDAY THROUGH SUNDAY/...
General VFR is expected to be marred only be scattered, high
based showers later tonight and Wednesday as a shortwave trough
traverses the region. Sfc wind will back from west to south
with the approach of that disturbance, then veer to the west
with passage on Wednesday afternoon.

.OUTLOOK...
Widespread restrictions are likely Friday with the encroachment
of a cold front.

&&

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

&&

$$



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