Monday, September 25, 2017, 5:53 AM EDT
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Area Forecast Discussion
Valid At
Wed, Dec 31, 7:00pm EST
FXUS61 KCTP 250951

Area Forecast Discussion
National Weather Service State College PA
551 AM EDT Mon Sep 25 2017

Unseasonable late-September heat will continue in central PA
through mid week. Mostly dry weather will also prevail with 
just an isolated shower possible in spots on Wednesday. A 
pattern change will bring cooler, fall-like weather back to 
the area for end of the week and into the upcoming weekend.


As with so many previous nights, valley fog is expanding over
central and northern areas. 

Areas of fog will give way to another very warm and muggy 
afternoon by late-September standards with max temperatures in 
the mid 80s to around 90F (15-20 degrees above normal). It will
feel even warmer with max HX values between 90 and 95 degrees.

Tonight will be another repeat of the last several, mild with 
mainly clear skies and valley fog after midnight. YAWN!


High heights and anomalous warmth, where have we heard that
before? Some of the deterministic models want to fire a shower
or two off over NW PA near the lake breeze, but we are dry and
stable and warm aloft so I stayed with the dry forecast.


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 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 
by Friday.


09Z TAFS sent.

Sunday was a dry and warm early fall day. The main feature
that was interesting was it was breezy. VAD winds around 
500 MB when I left yesterday morning were around 50 knots. 

Tue-Wed...Patchy AM valley fog possible. 

Thu...Mainly VFR conditions. Perhaps a few showers.

Thu-Fri...No sig wx expected.


Record-challenging late-September heat through early week. 
Daily high temperature records from 9/24 through 9/26: 

Bradford: 82 in 1961, 83 in 2007, 79 in 1998

Williamsport: 90 in 1961, 89 in 1970, 92 in 1900

Harrisburg: 97 in 1970, 93 in 1970, 91 in 1970

Altoona: 91 in 1970, 90 in 1970, 88 in 1998

The high of 86 in Bradford on Sunday was a new record high

The high of 92 in Williamsport on Sunday was a new record 
high temperature.




NEAR TERM...La Corte
LONG TERM...La Corte

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