Severe Thunderstorm Warning 140, NWS Pittsburgh, PA

Area Forecast Discussion
National Weather Service Pittsburgh PA
229 PM EDT Tue Jul 31 2018

.SYNOPSIS...
Daily chances for showers and storms are expected through the
week with increased moisture and passage of a slow-moving low
pressure system.

&&

.NEAR TERM /THROUGH TONIGHT/...
A shortwave trough responsible for ongoing convection will help
sharpen the warm front that is straddling the forecast area.
North of the frontal boundary, broad convective coverage with
light-moderate rain can be expected.

To the boundary's south, a moist, unstable warm sector will
support semi-organized convection in a moderate-shear, moist
environment. Given warm-sector storms, the combination of low
LCL, enhanced low-level CAPE and broad hodographs with
increasingly-favorable critical angle will favor rotating storms
capable of a tornado or two and damaging wind gusts during the
afternoon.

Any afternoon convection will shift ewd tonight and decay with
loss of heating, but showers and storms will increase in
coverage early Wed morning and begin spreading nwwd with time.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
A stagnant upper-level ridge in the wrn CONUS and the Bermuda
High to the east will maintain a trough in the central CONUS
thru the next couple of days. Today's surface low will not
migrate far Wed and Thu, and its associated cold front advancing
across the OH Valley will maintain chances for showers/storms
for much of Wed before diminishing in coverage on Thu.
Temperature should be near or slightly below seasonal average (in
the lower 80s) Wed-Fri owing to persistent cloud cover.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The unsettled pattern continues. There are still enough
differences in model runs to maintain a forecast of daily
shower/storm chances following a diurnal cycle. So far,
Saturday appears to be the drier day of the weekend compared to
Sunday. Temperature will climb to slightly above seasonal
average as heights and thicknesses increase.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Large area of rain with embedded thunderstorms will spread
eastward across the PA and WV terminals over the next several
hours. By and large, thunderstorm coverage will be focused HLG-
MGW with mainly a steady rain further north with some convective
enhancement. VFR ceilings generally prevailing through the rain,
with localized IFR visibilities in the heavier showers (LIFR
visibilities briefly possible MGW 1930-21Z.

Behind the precipitation edge later this afternoon, widespread
MVFR to IFR stratus has developed and is presently expected to
continue through the overnight hours. Areas of fog are also
possible before another axis of rain spreads in tomorrow
morning.

Winds will be light but erratic in direction, with an overall
east to southeast tendency, becoming variable toward 12Z.

OUTLOOK... Periodic restrictions are likely this week
with persistent moist southerly flow and multiple crossing
disturbances.

&&

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

&&

Kramar

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