Area Forecast Discussion
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FXUS61 KPBZ 240721

Area Forecast Discussion
National Weather Service Pittsburgh PA
321 AM EDT Sat Jun 24 2017

A cold front sweeping through this morning returning
comfortable humidity levels to the area. Below normal
temperatures greet us early next week.


Scattered light showers are bi-secting the area ahead of the
approaching cold front. These showers will result in little more
than re-wetting the pavement as they move east and erode from
drier air moving in during the pre-dawn.

The cold front will move through later this morning, leaving in
its wake lower dewpoints and clearing skies. Despite drying
through the column, some residual moisture will be present in
the mid-levels today. This will allow afternoon cu to develop as
cold air advection commences. Northern zones near and north of
I-80 could see an afternoon shower develop as a weak upper-level
shortwave passes through the broader trough. Precipitation
amounts with this activity should be negligible.

Increasing sunshine will compete against the cold air advection;
the result will be high temperatures right around the average.


The presence of a broad upper-level trough will dominate the short
term, bringing progressively cooler temperatures and afternoon rain
chances. A weakening shortwave trough will cross the Great Lakes
Sunday, bringing slightly deeper moisture and ascent, mainly across
the north. Cold advection will provide instability in the form of
steepening lapse rates through the mid-levels. Will carry chance
PoPs along and north of I-80, with slight chances reaching southward
near the Pittsburgh.

Monday will follow a similar pattern as Sunday, with a shortwave
trough digging into the Great Lakes. Models continue to show this
trough sliding further south than the previous shortwave. Again,
bolstered by steepening lapse rates, showers and thunderstorms are
expected to spread southward through the afternoon and evening. Rain
chances will continue into Monday night as the main upper-level
trough axis passes overhead.

Temperatures will continue to cool through the early part of the
week, dropping around 3-5F off the daily highs and lows from today`s
expected numbers. By Monday, temperatures will be about 10 degrees
below average.


The middle of the week will feature cool temperatures, left over
from persistent northwest flow from the broad upper trough.
Despite building high pressure at the surface, rain chances will
exist Tuesday before the axis of the main trough finally shifts
east of the area.

High pressure will take firm hold of the area Wednesday into
Thursday, restoring dry conditions areawide and allowing
temperatures to begin moderation. By the latter part of the
week, the center of the high shifts to just off the Mid-
Atlantic coast. This will will establish a return to a warm and
humid airmass that will fuel showers and thunderstorms by the
early weekend. Currently, the best chance of precipitation
exists on Saturday, as low pressure returns to the Great Lakes.


Condition improvement is expected through the morning as rain
ends and dry advection ensues in the wake of the front. Sfc wind
will veer to the West with passage and mixing will support gusts
near 20 kt by afternoon.

Chance for restrictions will come with afternoon convection on
Sunday and Monday as an upper trough settles over the region.




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