textproduct: State College

WHAT HAS CHANGED

* Added mentions of frost to next Tues AM. * Dried things out a little quicker Wed night.

KEY MESSAGES

1) Breezy with showers and thunderstorms moving through slowly from NW to SE tonight and Wed.

2) Stratiform rain expected across central PA on Wed.

3) Chillier to end the week with frost/freeze concerns returning Thursday night.

DISCUSSION

KEY MESSAGE 1: Breezy with showers and thunderstorms moving through slowly from NW to SE tonight and Wed.

A few taller SHRA did form on the old trough slipping into the central mountains now. Expect enough instability to help one or two to spark. More SHRA/TSRA are expected over the NWrn 5-6 counties this evening before stabilization makes it tougher to sustain deep convection. SPC did increase the risk of svr wind gusts to MRGL earlier today. The CAPE at/around BFD should be rather skinny despite 40+KT of deep-layer shear. So, MRGL is probably the right call. Plenty of boundaries to help kick off a TSRA or two. One boundary seems to be developing over far NWrn PA, but it is not likely a lake breeze as temps are just not that much higher than the lake because of clouds and patchy rain. Most of the showers will die down this evening before a more-stratiform area of rain slides in from the NW. It could still have some convective elements. If any heavier rain from storms drops earlier, that additional rain could make isolated minopr flooding. But, that risk is very low.

The wind is gusting into the 30s over the NW half and 20s SE, and will continue to do so into the evening. Again, stabilization should help stratify and decrease the gusts.

-------------------------------------------------

KEY MESSAGE 2: Widespread stratiform rain expected across central PA on Wed.

Wave of low pressure rides up the advancing cold front tonight and slows things down. A good feed of moisture will spread rain west to east across the CWA late tonight and Wed AM. The front should clear the eastern counties later in the aftn Wed. Before it does so, some convection may form ahead of it. But, a cap around 10kft will try to suppress storms in the SE. Do not expect the storms to become strong, moving east of the area in the middle of the aftn. Some lingering SHRA are possible in the late aftn/eve. Maxes will be 15F colder than today thanks to all the clouds and rain.

-------------------------------------------------

KEY MESSAGE 3: Chillier to end the week with frost/freeze concerns returning Thursday night

After the cold front pushes E and S of the CWA on Wed, the sky may clear out well enough in the nrn mtns to allow the temps to drop into the M30s. Some cloud cover is still possible, and the wind is not totally calm until later at night/early Thurs AM. Thus, there is the chc for frost there, but it's not a slam dunk. Thurs night/Fri AM looks better for frost. Most guidance puts mins into the 30s over the NW half or more of the CWA Fri AM, with less cloud cover than the night before. Not many pixels of 32F or lower on the MinT grid, but a small (20%) risk is there for someone to have a freeze across the NW. The risk for frost is much more - around 70% for the Allegheny Plateau and Laurel Highlands. So, we'll need to consider frost advy as we near that period. At this point, we're not quite confident enough for any frost/freeze products. We do have it mentioned in the HWO, but may need to expand mentions. After two more weak systems Fri - Sun, we get another cold night Mon night/Tues AM.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Scattered showers and thunderstorms will increase in coverage over northern PA through the rest of the afternoon, potentially bringing brief restrictions to BFD and IPT. Most guidance keeps these showers and storms away from any other airfields. Wind gusts of 25 to 35 knots will continue into the evening before tapering off overnight. LLWS will become a concern again at MDT and LNS as winds between 1500 and 2000 feet will still be in the 40 to 45 knot range for much of the night.

Expect ceilings to lower from northwest to southeast through the night and into Wednesday morning as rain expands southeastward along a cold front. IFR ceilings will first develop at BFD before expanding to JST and AOO by mid-morning. Both the LAMP and the NBM would indicate that IFR ceilings will develop across the rest of Central PA as well, but model RH profiles from both the RAP and HRRR suggest that MVFR ceilings are more likely. This is supported by the HREF as well, which only shows a 40 to 50 percent chance IFR ceilings impacting any other TAF sites. Visibility will likely drop to MVFR as rain moves in, with periods of IFR visibility possible. Scattered showers will linger into the afternoon with continued MVFR or IFR ceilings.

Outlook...

Thu-Fri...-SHRA possible, but trending drier.

Sat...Restrictions possible in rain.

Sun...Showers and thunderstorms in the afternoon with restrictions possible.

CTP WATCHES/WARNINGS/ADVISORIES

None.