Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
1126 am EDT Friday Jul 11 2014
high pressure will keep the area dry through most of Saturday. The
next cold front will arrive late Sunday and into early Monday.
Near term /through tonight/...
with surface high centered directly overhead...sunny and mostly dry
conditions will continue through this evening. An outside chance
of showers or isolated thunderstorm exists along the eastern periphary
of the ridges as a little more moisture has pooled there.
Otherwise dry and pleasant conditions will last through Saturday.
Short term /Saturday through Sunday/...
surface high will drift eastward tonight and Saturday. With the
area on the back side of the high and ridging in the upper
levels...overall flow will become southwesterly. This will allow
for temperatures to warm and humidity levels to rise.
Models are now showing a different story for the timing and
strength of a shortwave expected to swing through Saturday night.
Models are weakening the wave over the upper Ohio Valley and
focusing on a stronger wave over the northern Great Lakes. The
weakening of the southern wave is likely due to a stronger ridge
that will be in place over the region on Saturday. As this wave
forces it way into the ridge it wastes much of its energy. The
stronger wave will be well to the north and will move eastward in
the zonal flow. This scenario will slow the onset of probability of precipitation Sat
night and push the more likely time for showers/storms into the
daytime hours on Sunday.
Until models find a consistent solution for Sat night/Sunday...
forecast will be on the low confidence side. The timing and
placement of the waves will be the crucial element for the
forecast for the end of the weekend.
Sunday could be a day to keep an eye on as atmosphere destabilizes
and deep moisture increases. However...morning cloud cover will
be important...possibly holding temperatures down below convective
Long term /Sunday night through Thursday/...
shower and thunderstorm chances will continue as a series of upper level disturbances
crosses the region ahead of a slow moving cold front. The fnt will finally
cross the area Tuesday. Surface high pressure will then build in through Thursday under a
Great Lakes upper trough with cooler and drier conds.
Aviation /15z Friday through Tuesday/...
VFR conditions expected the remainder of the day as cloud
coverage will be limited to fair weather cumulus with bases between
Outlook.../Saturday through Wednesday/...
local restrictions due to showers and thunderstorms will be possible
Sunday through Tuesday...followed by a period of VFR conditions.