textproduct: Gray - Portland

WHAT HAS CHANGED

Confidence has increased for the severe potential across New Hampshire and western Maine this afternoon and evening.

KEY MESSAGES

1. A few strong to severe storms are possible through the evening hours across New Hampshire and western Maine today.

2. Another warm day with scattered showers and storms is expected on Wednesday.

3. Low pressure is likely to move across northern New England on Thursday and Friday, bringing more rain and storms to New Hampshire and Maine.

4. Above average temperatures start to subside and lead way to cooler temperatures through this weekend and early next week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

The forecast remains on track for the chance of some strong to severe thunderstorms this afternoon and evening, mainly across New Hampshire and western Maine. Overall temperatures have ended up warmer than forecasted today, adding confidence to the severe potential. Southwest New Hampshire has the greatest severe potential, with wind being the main concern. A non zero chance of a tornado, and some hail are also possible.

These storms move through during the evening hours, and gradually weaken as they move through the marine layer across Maine and the NH Seacoast. The remnant showers and storms push offshore by late evening, with a few scattered showers lingering into the overnight hours. Areas of fog and low clouds are likely along the coast tonight as the marine layer moves ashore.

KEY MESSAGE 2 DESCRIPTION...

Wednesday's weather looks somewhat similar to today's, but overall cooler across Maine and eastern New Hampshire with a cloudier start to the day. Temps likely warm into the mid to upper 70s across south central and western New Hampshire tomorrow afternoon. Another remnant MCS drifts eastward from the Midwest tomorrow afternoon, bringing another chance for showers during the afternoon hours. With enough daytime heating, thunderstorms are possible across southwest New Hampshire again tomorrow afternoon, but the severe potential looks to be much more limited.

Late Wednesday and Wednesday night, a back door front stalls near the Maine/NH border. Overall the progression of this front has been reduced since yesterday, and will be difficult to discern from an average sea breeze front going into Thursday. More fog and low marine clouds will be possible tomorrow night near and east of this boundary

KEY MESSAGE 3 DESCRIPTION...

Thursday morning, a warm front turns stationary over northern New England. With the frontal boundary stationary, persistent showers and maybe a thunderstorm looks to move in Thursday afternoon. Scattered to numerous showers and storms could continue through Thursday night and into Friday. A northward pivot of the front on Friday may allow for skies to clear in the south. If this is the case, convective initiation is likely Friday afternoon, with thunderstorms in the forecast again for southern New Hampshire. By the end of the evening, the low moves out of the area. A break in the unsettled weather looks likely on Saturday, though rain re- enters the picture on Sunday in the form of a cold front.

KEY MESSAGE 4 DESCRIPTION...

Temperature-wise, a strong mid-level ridge is keeping temperatures generally pretty warm for this time of year. Temperatures on Thursday will still vary greatly. Highs are forecast in the lower 70s across southern and central New Hampshire. A sea breeze and backdoor cold front both will likely keep coastal areas and Maine at least 10-15F cooler than New Hampshire on Thursday and Friday.

The first drop off in temperatures occurs on Saturday, as the aforementioned low on Friday ushers in cooler air and starts to flatten the mid-level ridge. Temperatures over the weekend look to be in the upper 50s and lower 60s. The second drop-off in temperatures occurs Sunday afternoon with the previously mentioned cold front. This front could have some more potent arctic air behind it and may bring high temperatures early next week into the upper 40s and lower 50s.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Mainly VFR prevails at LEB, MHT, and CON, except some brief restrictions in showers and possibly a thunderstorm this evening. Elsewhere, periods of MVFR due to ceilings and showers are likely by this evening, with IFR in low ceilings more likely at PSM, PWM, RKD, and AUG tonight. Improvement to MVFR and VFR is likely tomorrow, then MVFR and showers are possible again Wednesday afternoon. IFR with low ceilings is possible again along coastal terminals Wednesday night.

Outlook: Thursday-Friday: MVFR due to showers and thunderstorms.

Saturday: VFR expected.

Sunday-Monday: MVFR due to showers and thunderstorms.

MARINE

Generally fair winds and seas are expected through Wednesday night as a backdoor front stalls near the coast late Wednesday. Areas of fog will be possible each night.

Sub-SCA conditions are expected through the end of this weekend, with variable winds and seas of around 2-5ft.

GYX WATCHES/WARNINGS/ADVISORIES

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