Area Forecast Discussion
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FXUS61 KPBZ 192209 AAA
Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
609 PM EDT Wed Apr 19 2017
A series of low pressure systems will keep periodic rain chances
in the forecast through late week.
.NEAR TERM /THROUGH THURSDAY/...
-- Changed Discussion --610pm update...have made adjustments to overnight PoPs in line
with latest radar trends and hires model guidance. Leading edge
of shortwave trough is crossing Western Lake Erie and is
sparking a unorganized line of showers and storms. Shortwave is
expected to continue to move east-southeast this evening and
then be followed by a more significant wave of energy after
midnight. Models are putting more emphasis on the first wave, as
far as activity is concerned. Atmosphere ahead of trough is not
overly unstable, either at the surface or aloft, but there may
be enough shear to allow for, already developed convection, to
be maintained through the evening and into the overnight hours.
As the surface stabilizes this evening, additional convective
development will be dependent on the unstable layer above
5000ft. Have increased the PoPs overnight, creating the timing
and location in line with the movement and speed of the two
waves tonight. Have also added in the mention of gusty winds and
small hail. Confidence in stronger winds is low, but hail is a
possibility as the freezing level is reachable and lies within
the unstable layer aloft. Temperatures have been updated as
Shower activity will increase in coverage this evening as
models have been consistent depicting a line of
showers/thunderstorms this evening along surface boundary
crossing the region from the NW to SE....followed by a MCV which
is progged to cross the region later in the evening to several
hours after midnight. Instability is expected to be minimal but
there is potential for strong wind gusts with storms.
Overnight lows will be mild with cloud cover and continued WAA
ahead of the approaching cold front.
-- End Changed Discussion --
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/...
Showers and Thunderstorms will be possible again on Thursday
mainly during the afternoon and evening once/if convective
temperatures are achieved which now look to be in the upper 70s.
Activity during the day will be largely dependent on
instability. Any decent breaks in cloud coverage should be
sufficient. The main threat is the potential for strong winds
associated with any storms that have a strong enough updraft to
push cores above drier air progged to be around 20-25kft. Update
the HWO to mention slight risk of damaging winds for western
zones. With near 99 percentile PWAT values by that time will
need to keep an eye on rain rates.
A cold front will cross Thursday night but unfavorable
overnight FROPA timing and waning instability should help limit
potential for severe storms. The SPC marginal outlook still
appears reasonable at this time.
Temperatures will return to seasonal levels by Friday.
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
A trough from the NE CONUS to the Plains should keep rain
chances and cool temps across the area over the weekend as it
approaches and crosses the region, and as a surface low tracks to
our south. Building ridging should return dry and warmer weather
by early next week.
.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
MVFR cigs are beginning to lift to just above 3kft this
afternoon. This will likely continue through the evening before
A fast moving disturbance will move through the southern Great
Lakes tonight, bringing showers and possible thunderstorms,
mainly from HLG and north. Expect IFR restrictions beginning
with this activity late evening into the overnight. Winds will
generally be south 5-10 KTs.
Restrictions will be possible Thursday with low pressure and a
cold front. Widespread restrictions are possible Saturday and
Sunday with strong low pressure.