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NWS Area Weather Forecast Discussion
County Warning Area [CWA]: PBZ
Regional NWS Weather Office: Pittsburgh, PA

FXUS61 KPBZ 130317

Area Forecast Discussion
National Weather Service Pittsburgh PA
1117 PM EDT Sat Jun 12 2021

Mainly dry weather is expected tonight. Shower and thunderstorm
chances will increase on Sunday with a crossing cold front.


Mainly dry weather is expected tonight under mid level ridging. A few
showers are possible across NW PA to E Central OH late tonight as
waning convection across MI moves SE in NW flow aloft. Satellite
images show tops have been warming on this convection, indicating a
diminishing trend. Some patchy fog will be possible, mainly in the
river valleys. Lows are expected to be 5 to 10 degrees above average.


A trough centered near Hudson Bay, Canada will propagate sely
through the Great Lakes on Sunday and Monday. Subsequently, surface
frontogenesis should initially prompt thunderstorm development
coincident with peak heating.

In association with developing thunderstorms, model soundings
indicate a strengthening CAPE profile, with 2300 j/kg present Sunday
afternoon. Ample shear within the instability profile (40kts from
0-6km), and dry, cool mid level air could result in a few organized
severe thunderstorms. The SPC has outlooked the area in a marginal
risk(1/5) west of Pittsburgh, and a slight risk(2/5) for roughly
Pittsburgh on east. The best chance for severe storms will be during
the afternoon and early evening. Showers/storms should end Sunday
evening after surface cold frontal passage.

Some most recent CAMs continue to show more discrete cells as the
front tracks southeast through the area. There is a concern of some
early morning convection stunting the afternoon but models soundings
continue to show the morning cap so its possible instability will
build through the morning and into the afternoon before severe
convection will be allowed to develop. This set up bears some
watching. The other concern with the 18Z model soundings is the
abundance of DCAPE developed with the cells. An apparent dry mid
level will set the stage for some microbursts as well.

The same low pressure looks to dive farther south on Monday afternoon
and with it, jet support, and vorticity advection will allow for the
chance for thunderstorms. At this time, the SPC has not outlooked
the area for any chance of severe weather. The atmosphere looks as if
it`ll have to combat less instability, as a result of previous days
convection, but uncertainty remains for this time frame.


A longwave trough is expected to persist across the Eastern CONUS
through Tuesday. A weak shortwave rotating through the trough could
result in low chcs for showers Tuesday, mainly E of PIT. Sfc high
pressure building under the trough should result in dry and cooler
weather Wed and Thu.

The trough should exit the E Coast by late week. Ridging, ahead of
another approaching trough, should result in dry and warmer weather
weather Thu night and most of Friday.


VFR and mostly clear night skies will allow for patchy fog
development Sunday morning due to abundant sfc moisture and light
wind. There is some uncertainty in how widespread fog will be and if
low stratus will develop, but favored river valley TAF sites and less
stratus given slightly drier air in place than previous days.

Shower and thunderstorm chances will increase Sunday aftn with the
approach of a cold front, though an isolated morning light rain
showers may be ongoing from decaying upstream convection. Probability
of thunder will be greatest around and S/E of KPIT where instability
will be greatest, with potential for earlier frontal passage
precluding thunder mention at FKL/DUJ at this time. Any thunderstorm
could briefly reduce restrictions and produce strong wind gusts.

Periodic rain chances from passing shortwaves within a developing
eastern U.S. trough may also create intermittent restrictions through
Tuesday.  VFR under high pressure is expected by mid-week.





Forecast Discussion from: NOAA-NWS Script developed by: El Dorado Weather