Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1131 am EDT Wednesday Jul 29 2015
summertime heat and humidity will be the main weather story today
across central Pennsylvania. A cold front will move through the
Keystone state on Thursday...with isolated severe thunderstorms
possible near the lower Susquehanna valley. Friday will be
seasonably warm and dry with much lower humidity to close out July
Near term /through tonight/...
patchy fog nearly completely burned off this morning. Forecast on
track with a hazy hot and humid afternoon across the area. Pretty
decent chance that State College will have its first 90 degree day
in 2 years. Hrrr shows widely scattered convection firing off on
southern County Warning Area ridges and drifting slowly eastward. Middle level temperatures
still warm and this will limit widespread convection.
Short term /Thursday through Thursday night/...
short term model data over the last two cycles are a tad faster
with the eastward mvmt of the surface cold front forecast to sweep across southeastern
Canada and the northeast/Middle Atlantic States on d2/Thursday. Weak
height falls are still expected to overspread central PA on the
southern periphery of strong upper trough amplifying over eastern Canada.
Early-day cloud cover west/isolated showers along eastward-advancing cold
front should extend further into the interior central zones.
While the best large scale forcing for ascent/0-6km shear and
middle-level lapse rates will be displaced further to the north over
the New England states...still think that the southeastern 1/3 to 1/4 of
the County Warning Area stands at better than 50/50 odds to see a scattered thunderstorms ahead
of the cold front...a few of which may be strong to marginally
severe with localized wind damage potential given steep low-level
lapse rates and dcape values in excess of 1000 j/kg. Previous Storm Prediction Center
d3 marginal risk has been shifted south/east now covering only portions
of the lower susq valley. Drier low precipitable water air quickly spreads into the
area behind the frontal passage and ends the precipitation risk in the far southeast
counties by late Thursday evening/00z Friday.
Long term /Friday through Tuesday/...
little change is anticipated in the large scale flow pattern
across the eastern U.S. Through the medium range period...with a
mean ridge in the west and broad trough extending southward from Hudson
Bay vortex and east of the Continental Divide. Convective precipitation
should be rather sparse and focused along weakening northern stream
frontal systems progressing southeastward from the Great Lakes about every
1-2 days starting on Saturday. Confidence in timing is low
especially into early next week given increasing model spread.
Temperatures should cool back to seasonal averages into the
beginning of August.
Aviation /16z Wednesday through Sunday/...
fog dissipated and VFR conditions this afternoon under high
pressure. Clouds will start to advance tonight ahead of a cold
front approaching from the west. MVFR ceilings and visibilities are possible
beginning in the southwest and then spreading eastward as showers
in advance of the front may nudge into bfd before sunrise
The front should pass Thursday bringing drier conditions and a
decrease in the coverage of showers and thunderstorms late
Thursday into Friday.
Sat...mainly VFR...PM thunderstorms and rain poss west.