Area Forecast Discussion
Issued by NWS Pittsburgh, PA

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FXUS61 KPBZ 212129

Area Forecast Discussion
National Weather Service Pittsburgh PA
529 PM EDT Wed Oct 21 2020

Unseasonably warm and and mainly dry weather will continue the
remainder of the week before rain and cooler temperatures return late
Friday and Saturday morning with a cold front.



A weak frontal boundary draped over the region will lift north
overnight with precipitation, if any, limited to a few isolated
sprinkles north of PGH. Patchy fog or low stratus development
(dependent on near-surface turbulence) is forecast overnight with
light winds and a favorable hydrolapse. Overnight temperatures will
be very mild...close to record High Mins in some locations.


The remaining cloud cover will lift north of the region by Thursday
afternoon in the southerly flow. The ridge and offshore surface high
will continue to keep dry weather and much above normal temperatures
in the forecast for Thursday and Thursday night. Record temperatures
do not look like they will be threatened, although expected Thursday
highs in the upper 70s to near 80 may come within a few degrees in
one or two cases.

The Plains trough will rotate across the Upper Mississippi Valley
Friday morning, lifting across the Great Lakes by the evening hours
along with an associated surface low. This will also push the next
front toward the region, with PoPs returning to areas west of
Pittsburgh later Friday afternoon. This initial activity should be
fairly scattered and weak as the main surface low remains well off
to the north. Another very warm late October day can be expected
ahead of the front.


Frontal passage will occur during the Friday night/Saturday morning
period. It still appears that rain amounts and areal coverage of
precipitation will remain somewhat limited, as with the main surface
low and mid-level wave remaining well to the north, only right
entrance region jet dynamics will provide support for lift.
Transitory surface ridging should then provide a dry interlude
Saturday afternoon and night. Temperatures will be knocked back down
to seasonal levels behind the boundary.

The pattern thereafter looks to be even more active. A fresh trough
will likely be carved over over the Rockies and Plains Sunday and
Monday, while ridging near the southeast CONUS trough hangs on. This
will place our region in an area of warm and moist southwest flow
that will bring increased rain chances into the early part of next
week. Current indications are that a frontal passage is possible
Tuesday that would bring drier and cooler air by Wednesday, although
the details become tricker towards the tail end of the forecast.


Restrictions will be possible overnight as low stratus/fog
developmentlooks likely with light winds and a favorable

Widespread restrictions will be possible with a late Friday / early
Saturday cold front.




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