textproduct: State College

WHAT HAS CHANGED

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KEY MESSAGES

1) Seasonably pleasant start to the week with low humidity and no rainfall

2) Severe thunderstorm risk for Thursday 6/18

DISCUSSION

KEY MESSAGE 1: Seasonably pleasant start to the week with low humidity and no rainfall

Dry and sub-normal temperature airmass is sliding overhead. Dewpoint at BFD is already into the 40s. NW wind across all the CWA should help dewpoints lower everywhere, but there could be some fog around sunrise, especially in the more-clear spots (S/E). However, the expected wind could keep the fog at bay. Doesn't hurt to mention patchy fog at least. Really would be better for fog if the wind would slacken. The clouds will continue to decrease this morning, but diurnal heating and the passage of a weak shortwave trough aloft will help increase the clouds slightly for the aftn. Maxes will be 5F to 15F below normals today, barely getting into the 60s over the NW and the highest elevations of the Laurels. The SE will have subsidence to help them warm up slightly better w.r.t. the potential temps vs the rest of the CWA. Maxes there = M70s. Mins tonight will be pretty chilly for mid-June, 44-54F across the CWA and wind could go calm. That could make a little river valley fog in the N. Tonight, it will be the dryness of the airmass that could keep fog from forming (vs the wind this morning). Will hold off on mentioning fog for tonight. Later shifts can refine. Temps bounce up 5-10F on Tues, with sky cover similar to today. A couple of really nice days.

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KEY MESSAGE 2: Severe thunderstorm risk for Thursday 6/18

The nose of a very strong, 40+ KT swrly 850 mb jet 50+ KT at 700 mb (both being 3+ sigma on the standardized anomaly scale), the the right entrance region of a 100 KT 250 mb jet and PWATS around 1.5 inches (with the potential of a EML surging in from the west ahead of a strong sfc cold front) will bring the ideal synoptic setup for a severe weather outbreak here in the CWA. As always, even with the moisture and shear present, such strong forcing could produce plenty of clouds and early day convection. That would stabilize the atmos and decrease the potential for significant afternoon severe weather. It does look a little more possible that Wed night/Thurs morning convection could delay/impact the destabilization for Thurs. Without a strong trend, changes to Day4 are not necessary. We'll be monitoring this potential for severe weather closely.

AVIATION /12Z MONDAY THROUGH FRIDAY/

IFR conditions remain at JST as of 10Z Monday; however, expect rapid clearing of the low-level deck with high confidence in VFR conditions prevailing after 14Z based on a consensus of HREF/NBM model guidance. Elsewhere, VFR conditions are virtually certain (> 90% confidence) with low-level cloud decks generally around or above 4,000ft AGL. Main aviation concern throughout the entire TAF package will be breezy northwesterly winds that could allow for some crosswind component at AOO/UNV/IPT/LNS between 15Z-22Z Monday before winds begin to become lighter overnight. Current guidance outlines low (< 30%) potential for fog formation given low-level dry air filtering in with the passage of the cold front.

Outlook...

Tue...Mostly VFR with isolated -SHRA/-TSRA possible.

Wed...Higher chances for -SHRA/-TSRA, restrictions more likely.

Thu...Restrictions possible in -SHRA/-TSRA.

Fri...Showers ending.

CTP WATCHES/WARNINGS/ADVISORIES

None.