Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Pittsburgh PA
747 am EDT Sat Aug 23 2014
showers and thunderstorms will become less common as the weekend
GOES on...with warm and humid conditions persisting into the new
Near term /through tonight/...
special weather stmt for patchy dense fog was issued through 14z given
current conds. Previous discussion follows...
Recent rainfall from the past day or so combined with a very
humid air mass in place has allowed for widespread fog development
behind these showers. Some locally dense fog is likely...however
coverage seems as though it will fail to be sufficient to
necessitate a dense fog advisory.
This afternoon...the upper flow slowly becomes more longitudinal
as an upper ridge builds over the Great Lakes and a sweeping
trough digs off shore the northeast. With rising heights to our
west...mid-level temperatures look to increase from west to east
slowly into the weekend. This will gradually bring down the
chances of diurnal showers and thunderstorms from west to east as
the vertical extent of instability seems increasingly likely to be
cut off by warm air aloft. As such...the best chances of
redevelopment of showers and thunderstorms this afternoon will be
over the ridges...while points to the west in Ohio have a far
lower risk of a shower.
The upper ridge looks to continue to build into the region
tonight...with the jet axis shifting to the east of the region.
This should end the chance of precipitation overnight
tonight...but keep humid air in place. Once again...areas of fog
will be possible as a result. Fries
Short term /Sunday through Tuesday/...
high pressure quickly fills in behind the exiting upper trough sun
leading to a drying trend for the beginning of the week. Models have
continued to pull moisture out faster with each New Run. It now appears
that if any lingering showers exist with the diurnal heating Sun
afternoon...they will stay primarily south of the Mason Dixon line over the
high terrain of southeastern WV and out of our area.
Monday...with the axis of the ridge directly over the area and dry
air in place...cloud develop should even be limited. Abundant
sunshine will help keep temperatures close to or above normals. By late
Monday the upper ridge axis tilts west to east allowing a little
more moisture to stream across the northern periphery of the high. Some
clouds may develop into Monday night/tues...but the dry weather will
Long term /Tuesday night through Friday/...
ridging will persist through midweek keeping the trend of warm and
dry weather in place. Model guidance continuing to struggle with the
details surrounding a potential tropical system in the Atlantic.
While this system should have no direct impact to our immediate
area...the broad scale pattern including timing the breakdown of the
ridge will be impacted. A cold front will be in the neighborhood
towards the end of the week with associated shower chances.
Aviation /12z Saturday through Wednesday/...
occasional LIFR fog/ceilings noted at some terminals with MVFR/IFR at
others...both resulting from stagnant saturated air mass in the region.
Fog expected to lift by 14z...with broken ceilings between 1-3kft expected until
this afternoon. After 17z or so...VFR conds should persist.
IFR/LIFR fog/ceilings could return late tonight as air mass not expected to be
Outlook.../Sunday through Wednesday/...
Hipres will build into the region sun-Tue. Modest drying at surface may
preclude fog development through at least Tuesday. Showers and thunderstorms will become
increasingly likely Wednesday afternoon and evening...with attendant visibility and ceiling