textproduct: State College

WHAT HAS CHANGED

* A Dense Fog Advisory is in effect for much of the Alleghenies and northern mountains through 10AM/14Z.

KEY MESSAGES

1) Dense fog this morning, then sunny and warm

2) Fire weather concerns increasing by Friday

3) Rain-free and mild conditions into early November

DISCUSSION

KEY MESSAGE 1: Dense fog this morning, then sunny and warm

In the wake of yesterday's warm front, increasing dewpoints and clear skies have led to areas of dense fog this morning. Nighttime microphysics imagery vividly depicts fog-filled valleys across Central PA, prompting the issuance of a Dense Fog Advisory until 14Z/10AM. Meanwhile, an area of low clouds has developed in the Lower Susquehanna Valley extending along and just northwest of the I-95 corridor. The latest model guidance indicates that this cloud cover could be rather stubborn today, perhaps not fully eroding until early afternoon.

Once the fog mixes out and clouds lift, a mostly sunny afternoon is on tap. Temperatures will soar into the mid 60s to low 70s, which is anywhere from 10 to 20 degrees above normal for this time of year. It could be a good day to rake leaves, though many more leaves will fall tonight and tomorrow with windy conditions expected.

NOTE: October 29th is the anniversary of two historic weather events to impact central Pennsylvania in the past 15 years: Sandy in 2012 and the Snowstorm in 2011.

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KEY MESSAGE 2: Fire weather concerns increasing by Friday

It has been almost two weeks since we've received any measurable rainfall across Central PA. A cold front will sweep through the area from northwest to southeast overnight tonight into Friday morning. There could be a few light showers in northwest PA but dry conditions are expected for most. The cold front will bring gusty northwest winds and much lower dewpoints. The combination of drying fuels, increasing leaf litter, and low humidity air could result in an elevated risk of wildfire spread Friday and Saturday. Friday will be breezy in the wake of a cold front with marginally low afternoon RH values and max gusts forecast in the 20-25 mph range. That will result in an elevated risk of wildfire spread and plenty of falling leaves (and perhaps a rapid decline in fall color). PA Bureau of Forestry partners have indicated fuels are now sufficiently dry to support the issuance of a wildfire spread statement /if needed/ for Friday. Although relative humidity values will remain low through the weekend, lighter winds should limit the risk of rapid wildfire spread. Even still, individuals should limit activities that could start a fire. 99% of wildfires in Pennsylvania are caused by humans!

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KEY MESSAGE 3: Rain-free and mild conditions into early November

The latest model guidance indicates the lengthy dry spell will last through Halloween and probably into the first few days of November. There appears to be a modest multi-model/ensemble signal building toward the possibility of a frontal type heavy rain/wind event sometime during the second half of next week around the Nov. 5-7th timeframe. The Climate Prediction Center has highlighted all of Pennsylvania in a Slight Risk of High Winds for 11/5, noting the potential for a strong low pressure system to traverse the Great Lake region and bring gusty winds to the region. There is also a Slight Risk of Heavy Precipitation for southeast PA on 11/5. We'll need to monitor the potential for some rainfall, though hopefully most of it will be beneficial!

AVIATION /09Z THURSDAY THROUGH MONDAY/

Widespread fog is evident on nighttime microphysics imagery this morning, with VLIFR conditions prevailing at BFD, AOO, and UNV (as well as a handful of other secondary airports in the central ridge/valley region of PA) this morning. Meanwhile, low clouds are bringing restrictions to LNS and MDT. Restrictions will continue through daybreak, with gradual improvement expected later this morning. The lower almost-November sun angle will take a bit longer to mix out/erode the low cloud deck, so restrictions could linger until 14Z at several airfields. The latest model guidance also holds onto low clouds along and east of the Susquehanna River until early this afternoon (after 16Z). Restrictions could linger at MDT, LNS, and perhaps IPT until as late as 18Z. Thereafter, sunny skies and VFR conditions will prevail areawide.

Winds will be from the SW at 5-10 kts this afternoon. An approaching cold front will bring clouds and a few light rain showers across the NW after 00z Fri with restrictions possible in the north and west into early Fri morning. A period of LLWS is also possible between 00z and 09z Fri ahead of the cold front. Winds will ramp up along and behind the cold front as winds shift to the northwest. A period of MVFR ceilings are possible in the northwest (BFD & JST) in a classic northwest/upslope flow pattern.

Outlook...

Fri...A.M. IFR-MVFR ceilings mostly north/west; bcmg VFR.

Sat-Sun...VFR most likely prevailing with some A.M. low cloud or fog restrictions possible.

Mon...Slight chnc for rain and restrictions, mostly west; otherwise VFR.

CTP WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 10 AM EDT this morning for PAZ005-006- 010>012-017>019-024>028-033>035-041-045-046-049>052.