Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
501 PM EDT Sat Jul 30 2016
periodic showers and storms will continue through the weekend.
High pressure brings the return of dry conditions for much of
Near term /until 6 am Sunday morning/...
first area of showers and storms south and west of Pittsburgh
will transition across the southeast ridges through 00z as
shortwave exits east. Next impulse moving east across lower Great
Lakes on front side of mid level trough is producing a second area
of showers and thunderstorms now moving across eastern Ohio into
northwest Pennsylvania. Likely pops will be continued generally
along and north of the PA Turnpike this evening as this system
moves east. Storms are moving at 15kts are better, so flood threat
will be diminished unless any storms can train. No changes to
previous temperature forecast.
Deeper moisture does start to exit to the east overnight, likely
resulting in some amount of scattering out of mid and high clouds
even while the boundary layer remains very moist. This will mean
any amount of radiational cooling will result in widespread fog
and stratus development by morning.
Short term /6 am Sunday morning through Monday night/...
yet another short wave trough will translate southeast toward the
area on Sunday. With abundant low level moisture still in place,
the left exit of a northeastward translating upper jet streak, as
well as some mid-level cooling as the 500 mb wave tracks through the
area, scattered showers and thunderstorms will again develop on
Sunday. However, the coverage is unlikely to be as widespread as
was seen today.
Much drier air follows the exits of the Sunday system to the east.
The only exception to this may be a stray shower in the ridges on
Monday as low-level moisture may linger in the ridges a bit longer
than other areas. This may just barely manage to allow for a bit
more unstable profile and a shower or two during the peak heating
Northwesterly flow then encompasses the area by Monday night. This
will bring in much cooler and drier air for the overnight, which
could very well mean a night during which we can all shut off the
air conditioning and open the windows! Fries
Long term /Tuesday through Saturday/...
shortwave ridging will maintain dry and benign weather on Tuesday.
The shortwave ridge flattens a bit for the remainder of the week
as ripples rotate around the broad upper ridge over the Southern
Strong advection of warm, moist air is expected late in the coming
week. As a result of the arrival of this warm air, temperatures
will climb into the upper 80s-near 90 on Thursday and Friday. The
combination of the moist airmass and the weakening upper ridge
will support increasing chances for thunderstorms late in the
week, especially on Friday as a frontal boundary invades the
region from the northwest.
Aviation /21z Saturday through Thursday/...
heavy rain in showers and thunderstorms has been yielding
occasional LIFR/vlifr conditions /ceiling and visibility/.
Convective coverage is shifting more toward the eastern terminals
early this afternoon, which is expected to lead to increasing
cloud height as modest mixing occurs in the wake of the convection.
Showers and storms will develop again later this afternoon, but
coverage and impact to specific terminals is uncertain, so only
vicinity remarks were used at this time until timing and impacts
can be determined more confidently.
Outlook /Saturday night through Wednesday/...
broad upper troughing should maintain the potential for periodic
restrictions in showers and thunderstorms through Monday.