Scientific Forecaster Discussion
fxus61 kctp 251647
Area forecast discussion
National Weather Service State College PA
1247 PM EDT Mon Sep 25 2017
unseasonable late-September heat will continue in central PA
through mid week. Mostly dry weather will also prevail with
a passing shower possible in spots on Wednesday and Friday or
Saturday. A pattern change will bring cooler, Fall-like weather
back to the area for second half of the week into the upcoming
Near term /through tonight/...
another unseasonably warm and muggy late-September day in
progress with Max temperatures fcst to reach the mid 80s to
low 90s or +15-20 degrees above normal. It will feel even
warmer with Max hx values between 90 and 95 degrees; a few spots
may event get into the mid-upper 90s. Hard to deviate from
persistence in this pattern. Tonight will be another repeat:
very mild with mainly clear skies and more valley fog after
midnight lasting into early Tuesday morning.
Short term /Tuesday through Tuesday night/...
another day of summerlike heat and humidity expected across
central PA. Highs may be trimmed a bit across southeast PA as
some clouds bands associated with Maria wrap into the area. Some
hires and even coarser global models try to develop some
isolated convection Tuesday afternoon but odds remain strongly
in favor of dry wx pattern.
Long term /Wednesday through Monday/...
the blocking high that has been responsible for the recent
extended spell of dry and anomalously warm conditions is
forecast to start breaking down by mid week, with shortwave
energy sliding along the US-Canadian border finally chewing away
at the high heights and bringing some cooler air eastward.
In the meantime Maria is still forecast to drift northward into
the offshore waters off of Cape Hatteras on Wednesday. But the
aforementioned northern stream shortwave finally gives it the
incentive to take a hard turn east as the storm passes 35 deg
For our area, it looks like the first chance we will have to
see any rain might be later Wednesday with a weakening cold
front that is destined to fall apart in the unfavorable shear on
the northwest side of the sprawling hurricane. Any rainfall
looks to be scattered and light, bringing little change to the
dry conditions we've had around here for much of September.
A bit more significant trough will approach for the end of the
week into the weekend. The European model (ecmwf) has backed off and now looks
much like the GFS with a flatter faster wave, and a return to
ridging by Sunday. The atmosphere will be dry so there doesn't
seem to be much of a chance for significant rain, just
scattered light showers. We will likely go on into at least 3
weeks without any widespread beneficial rain.
The biggest change will be that temps will drop off from our
streak of well above-normal levels back toward seasonal normals
Aviation /18z Monday through Saturday/...
widespread VFR conditions into tonight. No reason to deviate
from persistence with fog restrictions likely again after
midnight into early Tuesday morning.
Tue...am valley fog becoming VFR.
Wed...spotty PM shower possible. Mainly VFR.
Thu...no sig wx expected.
Fri-Sat...isold-sct showers possible. Mainly VFR.
record-challenging late-September heat through early week.
Daily high temperature records for 9/25 and 9/26:
Bradford: 83 in 2007, 79 in 1998
*williamsport: 89 in 1970, 92 in 1900
Harrisburg: 93 in 1970, 91 in 1970
Altoona: 90 in 1970, 88 in 1998
*williamsport maximum temperature records are under review for
Saturday and Sunday 9/23-9/24.