textproduct: State College

WHAT HAS CHANGED

* Dense Fog Advisory posted for the Lower and Mid Susquehanna Valley until 8 AM this morning. * Maintained lower temps Sat and slightly higher values Sat night due to cloud cover and wind.

KEY MESSAGES

1) Dense fog across the Susq Valley early today, otherwise unseasonably mild through today with 2.5 weeks-long dry spell now over.

2) Trending cooler this weekend with lake enhanced rain showers beneath upper level low, mixing with some wet snow showers early Sat across the NW Mtns and Laurel Highlands .

DISCUSSION

KEY MESSAGE 1: Dense fog across the Susq Valley early today, otherwise unseasonably mild through Friday with 2.5 weeks-long dry spell now over.

A slow moving and weak cold front over Eastern Pennsylvania will be the focus for some morning showers across the region to the East of the Route 15/Interstate 81 corridors. A secondary cold front will push through Northwestern PA later this morning and move across the rest of Central PA and the Susquehanna Valley this afternoon.

One more day of unseasonably warm temperatures across much of the CWA, though even highs in the mid to upper 50s across the NW Mtns is still quite mild for early Nov.

A dry slot with plenty of thin spots in the high clouds and near calm air in the weak P-gradient between the aforementioned cfronts was leading to areas of dense fog across the Lower and Middle Susq Valley early today.

The approach of the secondary front from the west will stir up a light SW to Westerly breeze within a few hours after sunrise and the fog should improve quickly during the second half of the morning commute.

KEY MESSAGE 2: Trending cooler this weekend with lake enhanced rain showers beneath upper level low

Update... 00Z guidance continues to highlight the trough of the upcoming cooldown occurring Sat morning when a pocket of -7 to -8C 850 mb temps pivots through NRN PA accompanied by deep moisture and some mesoscale focus for lift and occasional rain/wet snow showers along and in the wake of yet a 3rd cfrontal boundary with a boost of enhanced orographic lift.

Its not out of the question to see a light slushy coating of snow during the mid/late morning hours Sat at elevations above 2100 ft MSL across the NW and over 2600 MSL in the Laurel Highlands - the first of this mild/very pleasant fall season so far. GFS is by far the coldest of the model guidance but it should be highlighted than Lake Erie is still 60-62F (near or slightly over record warm water temps for this date). This will undoubtedly temper this cooler guidance.

Previous disc...

We have been constantly been pulling NBM (mean) temp guidance down closer to MOS blend for Sat, and we've now done it more so with continued support from many sources. We have also pulled temps up a few degs for Sat night due to the same clouds and also wind which should keep us more- mixed.

Seasonably cooler/breezy pattern to start the first full weekend of November. The passage of closed H5 low followed by mean cyclonic flow favors persistent clouds and periods of lake enhanced rain over the western and central Alleghenies on Saturday. We were keen to manually adjust max temps a few degrees lower on 11/7 to account for the cooler pattern shift which looks to continue into early next week. If the current forecast holds, it will be the first below average daytime high in three weeks!

AVIATION /09Z FRIDAY THROUGH TUESDAY/

Patchy MVFR ceilings (KMDT/KLNS) and localized fog (mainly KIPT, with patchy BR/FG around KMDT/KLNS as well) will persist over eastern Pennsylvania this morning as a cold front slowly presses eastward. A compact shortwave moving over the Great Lakes will reinvigorate convection ahead of the front this morning, mainly along the I-95 corridor, though a few showers may move across KLNS before drier air moves in for the afternoon. While thunder cannot be ruled out at KLNS (10% chance), MUCAPE trending towards 0 J/kg around the onset of these showers precludes thunder mentions at this time. For KMDT, drier air filtering in behind the front will limit shower activity, with PoPs of around 10-20%. Brief MVFR visibilities will be possible with these showers, primarily at KLNS, with restrictions otherwise unlikely.

Otherwise, surface winds today will continue to trend westerly behind the front, with cloud bases lowering as the shortwave approaches from the northwest. Ceiling restrictions will be most likely at KBFD/KJST within this common upslope/lake flow setup, primarily around and after 18Z Friday, with lower chances east of the Alleghenies. A few light showers will be possible as well, mainly over KBFD closer to the center of the shortwave. Additionally, brief periods of VFR may occur at KBFD/KJST between roughly 00Z and 06Z Saturday as a dry slot wraps around the center of the shortwave before low-level moisture flows back in.

Outlook...

Sat-Mon...Breezy with showers and sub-VFR ceilings possible over the NW 1/2 of the airspace. Max gusts 20-25kt.

Tue...Mainly VFR with westerly winds gusting up to around 20-25 kts during the daytime.

CLIMATE

1. Today marked the end of the following Consecutive Days streaks without measurable rain:

10/17 through 11/4 (19 days): Harrisburg, Williamsport, Altoona, State College

10/18 through 11/4 (18 days): Johnstown

2. Daily record highs for 11/4 and 11/5:

Harrisburg 78/1994 | 79/1975 Williamsport 75/2003 | 77/1994 Altoona 77/2003 | 77/2015 Bradford *TIED = 74/2015 | 76/2024 State College 78/2003 | 75/2015

3. The sun will set at 5PM on Saturday 11/7 in State College. This will mark the beginning of a 2 month period during which sunsets will occur before 5PM surrounding the Winter Solstice.

CTP WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 8 AM EST this morning for PAZ036-046- 049>053-056>059-063>066.