Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
341 PM EDT Sat Aug 1 2015
high pressure centered over the middle Mississippi Valley will
ridge up the Ohio River valley and into Penn through the rest of
this weekend. This weather feature and persistent west-northwest
flow aloft will maintain fair and dry weather with comfortable
humidity into early Monday. A deeper trough will dig down across
the Great Lakes on Monday and Tuesday...sending a strong cold
front through the region on Monday.
Near term /until 6 am Sunday morning/...
a weak surface trough extended from near kbgm to kjst at 19z. A
gradually veering of the surface wind by about 20-30 degree will occur
for several hours late this afternoon and evening in the wake of
the trough...with surface wind speeds averaging 8-10 kts. Gusts for
the rest of this afternoon will be generally in the middle teens
based on BUFKIT NAM soundings with the depth of vertical mixing up
to around 7 kts above ground level.
Relatively cooler temperatures aloft/850-500 mb lapse rates of slightly
greater than 6c/km will reside across the ncent mountains this
afternoon. Combine this with the presence of the surface trough...
surface dewpoints near 60f...and strong heating of the day and we should
see isolated showers /and perhaps a few low-topped thunderstorms and rain/ between
Temperatures will rise just another degree f or two and end up pretty close
to normal across the northwest half of the County Warning Area...and slightly warmer than
normal in the southeast. Someone may see 90f in the lower susq thanks to
a light- MDT westerly downslope flow.
Short term /6 am Sunday morning through Monday/...
surface high pressure ridge will be slicing right through the region
on Sunday providing abundant sunshine and comfortable temperatures and
humidity with surface dewpoints in the 50s...to around 60f in the southeast
Temperatures to get back to normal across the northwest and perhaps add a degree f
or two to Saturday/S maxes elsewhere.
Another weak trough headed our way from the upper glakes in the
otherwise...dry northwest flow will help to funnel some limited low level
moisture ahead of it and spark isolated-scattered rain showers/thunderstorms and rain later
Sun night across the northwest zones...and elsewhere Monday as a cold
front moves through.
Stronger storms are possible Monday afternoon...but the timing of
the cfront is still a little uncertain. Moderately strong deep layer
shear from the west to west-southwest...but marginal cape...equates to Storm Prediction Center/S
outlook for marginal severe across much of the County Warning Area. Have kept probability of precipitation
in the high chance/low likely for the daylight hours Monday.
Model blended temperatures suggest that highs Monday could edge into the
l90s in the lower susq prior to the cfropa...while maxes will be
in the upper 70s to middle 80s across the northwest half of the state.
Long term /Monday night through Saturday/...
minor changes were made in long term pattern. Upper level trough
will begin to move through early Monday which should bring a cold
front through Monday night into Tuesday. As this line should
coincide with daytime heating expect a chance for showers and
thunderstorms. After that system moves through zonal flow is
expected with a quasi-stationary boundary along the Mason Dixon
line. Expect showers and thunderstorms to be possible along this
boundary through the second half of the week. The broad upper
level trough that will dominate the weather pattern this up coming
week will finally move through next weekend which could spark
another chance for precipitation.
Temperatures should average near normal into early next week before
trending cooler later in the week.
Aviation /19z Saturday through Thursday/...
VFR expected to dominate the majority of the period as high
pressure moves across the region within primarily west-northwest
flow. Isolated showers /mostly sprinkles/ will occur late this
afternoon/early this evening...generally across the higher terrain of
central and northern Penn in vicinity of of a southeast moving surface trough and a pocket of
slightly cooler temperatures aloft. Skies will clear out by late this
evening as instability wanes. Northwest winds will lighten up too...and
back to the west-southwest by daybreak Sunday. West-SW winds at 5-7 kts
during the day Sunday.
Mon-Wed...VFR...except for brief MVFR in isolated-scattered
mainly afternoon and evening showers/thunderstorms.