Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
330 am EDT Thursday Jul 2 2015
a crossing upper disturbance will increase rain chances for the
start of the Holiday weekend.
Near term /through tonight/...
surface high pressure should maintain stability and dry weather
for most of the region through today...although as crossing
shortwave will spread some middle and upper cloudiness over the
area. That disturbance may also support some showers over areas
south of I 70 due to presence of the stalled frontal
boundary...objectively analyzed over central WV early this
Filtered insolation and weak cold advection on light north wind
should limit temperatures to a few degrees under the seasonal averages.
Short term /Friday through Sunday/...
models have been consistent in advancing another weak shortwave
across the frontal zone on Friday...with GFS and srefs again
progging more extensive precipitation probabilities although NAM again
projects likely numbers over the WV ridges.
Any precipitation would diminish with slow eastward progress of the
supporting disturbance on Friday night and probability of precipitation have been thus
constructed. Low...diurnally supported probability of precipitation are appropriate for
Saturday with yet another shortwave GFS/NAM prognosticated across the
area while all but southeastern counties should be dry on Sunday
with building high pressure.
Temperatures under this pattern are likely to remain just under
the seasonal averages...although further recovery is possible on
Sunday should heights rise as projected. Either way...few changes
were needed for short term temperatures.
Long term /Sunday night through Wednesday/...
compared to 24 hours ago...models are in much better agreement
with the broad scale features of the extended forecast. Still
cannot rule out the possibility that the seemingly-permanent
frontal boundary will linger near southern counties for one more
day and allow for isolated/scattered showers on Monday. Otherwise
the region should be dry. The prognosticated cold front that previously
had widely varying projected times for passage now has some
agreement from deterministic as well as ensemble models of a
Tuesday night and Wednesday passage. Have changed the forecast
accordingly. With the cold front to the west Monday and
Tuesday...this should allow for more sunshine and have also bumped
up high temperatures those two days.
Aviation /07z Thursday through Monday/...
high pressure will allow for the bl to decouple overnight and
with few clouds...think that restrictions in fog will once again
be likely. Only question will be how low visibilities and ceilings will
go...with some high clouds overhead. For now...opted to stay
close to the previous forecast...bringing a return to VFR after
sunrise. Wind will remain light through the period.
Outlook.../Friday through Monday/...
after another round of fog/stratus restrictions Friday
morning...afternoon showers/storms Friday and Saturday could
provide additional restrictions.