textproduct: Gray - Portland

WHAT HAS CHANGED

The threat for severe thunderstorms has ended so the watch has been cancelled. Remaining showers are rapidly exiting the area so refined PoPs to reflect that at well. There still remains a chance for additional showers and thunderstorms this afternoon, but if thick smoke concentrations remain overhead we may see this stunted once again. The aviation section has also been updated for the 12Z TAFs.

KEY MESSAGES

1. Overnight instability and shear still support occasional instances of strong to severe thunderstorms through early this morning. These should be focused across far southern Maine and central to southern New Hampshire.

2. Additional cold fronts will approach today and again Thursday, bringing chances for showers and storms and a slight cooling trend into the weekend.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Overnight instability remains in place, albeit mostly elevated, through early morning. A 500mb jet exit region will nose into northern New England over the next few hours, providing lift and kinematic support for strong to severe thunderstorms.

Storm lifecycles have been fairly routine through last evening and into the overnight hours, but coverage has been very difficult to forecast and message. 00z GYX RAOB displayed a very stout cap aloft, but with an EML above. This setup is rare for the region, and while significant widespread severe has not come to fruition, it bears watching given the parameter space should a storm take advantage of it.

The approaching jet may provide that extra lift needed to bypass the cap's ability to wilt compromised updrafts. Thus think the ongoing Severe Thunderstorm Watch(es) is warranted considering upstream activity now passing through Upstate NY.

KEY MESSAGE 2 DESCRIPTION...

Troughing will deepen over the eastern U.S. today through the end of the week. Northwesterly winds behind a cold front will usher in a drier airmass later today despite warm high temperatures. One thing to watch will be lingering Canadian wildfire smoke, which had a significant impact on high temperatures yesterday. Should this remain, then high temperatures today will likely fall a couple degrees cooler. There is the potential a few showers and thunderstorms both this afternoon and again Thursday afternoon with perhaps some severe potential, although on a localized scale.

High pressure builds in Friday for fair weather. A short wave moving within the long wave trough over eastern North America will approach over the weekend. This will bring increasing chances for showers late Saturday into Sunday morning.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Through 12z Thursday...A cold front crossing this morning has bring an end to shower and thunderstorm chances, but will increase NW winds gusts to around 25 kt through the evening. Additional SHRA/TS chance this afternoon, but isolated. VFR continues into this evening and tonight with precip coverage decreasing.

Outlook:

Thursday-Saturday: Mainly VFR conditions with WNW flow prevailing. SHRA/TSRA Thursday afternoon/evening may bring TEMPO restrictions.

Saturday night-Sunday: Chances for rain may bring a period of at least MVFR.

MARINE

Another cold front crosses Thursday with SW winds increasing ahead of the front and then shifting offshore Friday morning. Winds and seas likely remain below SCA thresholds into the weekend.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...None