Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
314 PM EDT Friday Sep 19 2014
high pressure will maintain dry conditions through Saturday as
southerly winds warm temperatures up to at or above normal.
Chances for showers and thunderstorms increase Sunday with the
passage of a cold front.
Near term /through Saturday/...
broad surface high firmly entrenched over New England will ensure dry
conditions persist through the near term. As the high has slowly
pivoted east over the last day or two...our area has found itself
on the SW quadrant...bringing southeasterly flow into the area. This
southeast flow has been advecting middle-Atlantic moisture along the
eastern slopes of the Appalachians and is currently manifesting itself
in increased cloud cover evident on the latest visible satellite
images. Should continue to see altocu development spread west with
slightly increased moisture through the early evening.
Clouds will dissipate some tonight...mainly across the lower
terrain...but southerly flow increases as surface gradient begins to
tighten ahead of the Sunday cold front. Am trending lower with
cloud cover overnight...but increased bl flow alone should
preclude extensive fog development. Warm southerly breezes will
allow temperatures Saturday to reach slightly above normal...with
some locations across the south flirting with the 80 degree mark.
Short term /Saturday night through Monday night/...
moisture will increase Sat night on southwesterly wind ahead of a cold front that is expected
to cross the region on sun. This increasing moisture will keep temperatures from
falling too aggressively Sat night...with minima in the upper 50s-lower
60s. Showers forming along the advcg front may move into far northwestern
zones by late Sat night.
500 mb shortwave trough will begin to acquire neutral to negative tilt on sun
as it crosses the southern Great Lakes. The concurrence of increasing shear as 500 mb
jet strengthens...continued moisture advection ahead of cold front and increasing lift
should promote development of cnvctv line along surging cold front. The
intensity of the line will depend upon amount of sunshine that occurs
ahead of the boundary. Provided deep cnvctn develops...there will be a potl
for damaging wind gusts with organized cnvctv line segments. This potl
will be highlighted in the severe weather potential statement at this time.
Probability of precipitation were increased considerably on sun in line with guidance trends.
Best chance for precipitation appears to be Sun afternoon as cold front crosses the region.
Any showers will shift eastward by early evening...with perhaps some lake-
effect showers forming across northern zones Sun night.
Surface hipres moves into the region by Monday...bringing an end to precipitation and
promoting cooler temperatures through Monday night.
Long term /Tuesday through Friday/...
overall dry and cool pattern is expected for the remainder of the
long term period.
Aviation /19z Friday through Wednesday/...
VFR conditions today with scattered altocu and light southeasterly
winds. Expecting more of the same for Saturday...save for
increased southerly surface flow that could at times gust 15-20kts.
Outlook...Friday night through Tuesday...
general restrictions and gusty winds are likely with a Sunday