textproduct: State College

WHAT HAS CHANGED

* Added discussion of weak severe threat today

KEY MESSAGES

1) Weak cold front today, then a stronger system moves across PA on Thursday night and Friday

2) Windy and wet end to the week with first flakes in the higher terrain

3) Cold weather may end the growing season for many places Sat and Sun mornings.

DISCUSSION

KEY MESSAGE 1: Weak cold front today, then a stronger system moves across PA on Thursday night and Friday

Low pressure over NY this morning will move east and drag a cold front down from the north and across all of PA by 00Z. SHRA and TSRA are already over nrn OH and will reach the western counties in the next 3-4 hrs. The risk for thunder is there, but low, as the best low level jet winds are south of the state, and some CIN is expected to remain for much of the day. Thus, convection is more likely to be elevated (not rooted at the sfc). Bulk shear is progged >40kt at JST, but tops are only expected to be 20-25kft. Pretty rare that we get any severe gusts with CAPE only in the 200-500J/kg range and no favorable thermodynamic environment to allow winds to accelerate completely down to the sfc.

QPF for today is low with just 0.50" as the top end in the Laurels. Any TSRA should be moving along steadily. So, we should have no risk for flooding rains today.

The next storm system will be driven by a sharp upper trough with a strong sfc high behind it. PWAT does increase to 1.8" in the S. The showers and any storms will be moving very quickly Thursday night and Friday. 1hr FFG is currently 0.8" and higher - but could decrease very slightly due to any rain today. Storm total QPF in the 0.1-0.2" range in the SC-SE and near 0.75" in the NW (where FFG is higher) should not lead to flooding.

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KEY MESSAGE 2: Windy end to the week with first flakes in the higher terrain

Wind gusts 30-45 mph are forecast on the backside of the cold front and will deliver much colder air downwind of the Great Lakes this weekend. Latest NBM probs hold only 10pct chc for advy gusts - and only on the very highest elevations. JST BUFKIT profile from GFS does nudge 60KT winds down to 5kft AGL. So, it will be windy, and worth monitoring for an advy at some point - but only for the highest elevations - probably not for 90pct of the CWA.

The shot of colder air will allow for rain to mix or changeover to snow showers Friday night into Saturday morning across the higher terrain along the Allegheny Mtns. Any minor accum (<0.5") would have to occur overnight and be limited to non paved surfaces.

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KEY MESSAGE 3: Cold weather may end the growing season for many places Sun morning.

Big sfc high moves in for the weekend, supplying dry but cold weather for Sat and Sun. Sat will hold the coldest daytime temps with temps getting just above 40F in the NE. Sat AM could be sub-freezing for the nrn tier. So far, only McKean Co has been taken off the list of zones to need any further frost/freeze products. But, we could add to that list Sat AM - and especially on Sun AM. Sunday morning lows expected to be in the upper 20s to mid 30s may kill the growing season for a significant portion of the CWA. We'll be considering appropriate frost/freeze products, but it is still too early to be that confident on details. Pretty cold again Monday AM, but not quite as cold - and some of the area may not need any more frost/freeze products by then.

AVIATION /07Z WEDNESDAY THROUGH SUNDAY/

VFR conditions will continue at all Central PA airfields through the rest of the overnight and mid morning hours, with subtle features in the form of a lee trough down the Susq Valley and a weak surface ridge over the Alleghenies of Western PA.

A cold front extending from near KTOL to KBUF will drift south across the CWA during the late morning and afternoon hours preceded by a round of showers and maybe a few rumbles of thunder across the Western Mtns shortly after sunrise with just isolated to scattered light showers further east afterward.

LLWS will be the primary impactful factor during takeoff and FAP with a west to west-northwest low level jet of 35 to 40 kts affecting Central PA and Susq Valley airfields through the 12-14Z Wed period.

There will be a slight window at JST/AOO where there could be a couple hours of relatively dry conditions during the early to mid afternoon before another round of showers moves through late this afternoon/early this evening - along and just to the north of the slow moving cold front.

Elsewhere, expect VFR this afternoon/tonight at KIPT/KMDT and KLNS as winds veer to the northwest behind the aforementioned cold front with low end VFR- MVFR cigs across the Central and Western Mtns, trending down into the MVFR range late today and tonight.

Outlook...

Thu...Morning rain across S PA moves northward throughout the afternoon and evening hours. Restrictions possible.

Fri...Higher chances of SHRA with isolated TSRA. Restrictions increasingly likely.

Sat...Lingering SHRA across N/W PA with some -SHSN mixing in early Saturday morning. Restrictions likely at airfields that mix over to SHSN. Precipitation tapers off by sunrise, VFR prevails with gusty winds.

Sun...AM fog possible; otherwise, VFR conditions prevail.

CTP WATCHES/WARNINGS/ADVISORIES

None.