Marine Weather and Tide Forecast for Thomaston, ME

NEAR TERM /THROUGH TONIGHT/
Quiet weather this evening with just a few high clouds encroaching into the west and winds generally going light an variable. Our focus is centered on a progressive shortwave and resulting MCS will ride the northern periphery of the upper level ridge overnight, following along a frontal boundary draped over New England. It still isn't locked in on exactly where the feature will track, but SPC has placed much of the northeast including GYX into a marginal risk. CAMs favor the system reaching our CWA, but as a weakening system as it dives southeast from Ontario. However, there remains low confidence in these nocturnal MCS', and if it maintains some strength then storms could easily pull some strong damaging winds to the surface. The 12 HRRR is the most bullish suggesting 30-40kts of 0-6km shear, and mid- level lapse rates above 7 degrees per km, resulting in storms with the potential for 50kt winds or greater between 5-8 AM, mainly in NH. Best case and most likely scenario is this feature weakens into scattered showers and thunderstorms with some pockets of heavy rain, but worst case could result in warning level conditions. Moisture pooling with this feature will also support some heavy rainfall, but due to the progressive nature of the feature there shouldn't be more than 1" for any given area, but repeat activity could quickly accumulate and become problematic. WPC has a marginal ERO for for most of NH and far w ME. Have added gusty winds and heavy rain for all but eastern zones given the lower confidence on the track being that far east.

SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/
The remnants of any early morning MCS should clear out fairly quickly, leaving some breezy conditions but generally clearing.
Humidity makes its return with dewpoints shooting up into the 60s and lower 70s in S NH. This is when the focus transitions to the much advertised heat that will linger through Tuesday.
Temperatures will climb into the upper 80s to mid 90s. Can't rule out a few showers popping up due to increasing instability, but don't see much of a trigger to overcome the building subsidence overhead.

LONG TERM /MONDAY THROUGH SATURDAY/
Pattern Overview: The focus of the long term will be anomalously high pressure allowing for dangerous heat and humidity to build into the region through Tuesday. It looks like the ridge begins to break down on Wednesday with a surface cold front bringing relief from the oppressive heat and humidity.
This will make for a more unsettled pattern late week as 500mb becomes more zonal with some hints at shortwave troughs as well.

Impacts and Key Messages: * Dangerous heat and humidity is expected Monday and Tuesday.
An Extreme Heat Watch has been issued for areas south of the mountains and away from the coast where heat indices have higher confidence to be around 105F.

Details: Monday: Monday will be the first of our very hot days as an anomalously high ridge allows 850mb temps to climb upwards of +22C. Current forecast soundings don't show mixing quite to that level, but it looks close so this would equate to actual temperatures in the upper 80s to mid 90s. Locally higher surface temperatures in the upper 90s look likely along the Connecticut River Valley. Of course with dewpoints in the upper 60s and low 70s, the bigger concern will be with apparent temperatures. It is worth noting that the higher dewpoints in the low 70s are more concentrated in New Hampshire Monday along with the higher temperatures in the mid to upper 90s in the southern half of the state. For this reason the Extreme Heat Watch remains over just the southern half of New Hampshire where heat index values of 105F are most confident. The other thing to mention is that we won't be seeing much in the way of relief overnight as temperatures remain in the 70s. Warm overnight temperatures can also contribute to heat related illness so the the Watch runs right through the night. It is recommended to make preparations/plans now for this extended duration heat.

Tuesday and Wednesday: Heat continues Tuesday with higher dewpoints shifting east as well as more efficient mixing up to 850mb which will bring Western Maine into the Extreme Heat threat, the areas south of the mountains and away from the coast anyway. Actual temperatures in the mid to upper 90s inland could feel more like 100- 105F+. Far southern New Hampshire, where actual temperatures may hit the triple digit mark, could even see heat indices approach 110F. For this reason the Extreme Heat Watch will remain extended into inland western Maine for Tuesday afternoon with southern New Hampshire also remaining unchanged through Tuesday. I want to emphasize that areas outside of the watches are expected to see heat indices of 90+ which are still dangerous. Relief will come first to northern zones as a cold front enters the area Tuesday evening. This will bring about lower dewpoints and temperatures along with a chance for some showers and thunderstorms. It is looking like areas south of the mountains wont be as lucky as the front takes its time sinking southward. Low temperatures in these locations likely remain in the upper 60s to around 70. The front looks to clear the area some time Wednesday morning bringing the relief of lower dewpoints area wide. While Wednesday will still be warm, in the 80s, it comparatively will feel like a pleasant summer day. Low temperature dip back into the 50s and low 60s Wednesday night, which will also be welcomed.

Thursday-Saturday: The pattern becomes more unsettled late week as our ridge breaks down and global models advertise a more troughy and relatively cooler trend. Based on NBM consensus we are looking at chances of showers each day with high temperatures in the 70s.

AVIATION /18Z SATURDAY THROUGH THURSDAY/
Short Term...VFR prevalent across the region under the influence of high pressure. An area of showers and thunderstorms will move into the region overnight and early Sunday, bringing periods of MVFR ceilings, and IFR in any thunderstorms. The main concern is LLWS with a decent low level jet around 40-50kt.
Only have TSRA mentioned for NH terminals given low confidence.
Weather will improve behind the shortwave, with VFR conditions.
LLWS will linger through late morning before mixing brings breezy conditions to the deck.

Long Term...VFR will be the prevailing condition through Thursday, with a slight chance for afternoon showers each day.

MARINE
Short Term...Winds will increase overnight out of the south as a wave of low pressure move by to our north. This will bring in small craft conditions with gusts around 25kt. High pressure building in behind this feature will quickly dampen winds and seas for Sunday night. A beach hazard statement is issued for paddle craft due to cold water temperatures.

Long Term...High pressure over the waters will keep wind gusts and seas well below SCA criteria through Thursday. Afternoon seabreezes are likely to develop each afternoon as well.

CLIMATE
Anomalously high pressure will allow for dangerous heat and humidity to build into the region. This heat could potentially be record breaking for Monday (6/23) and Tuesday (6/24). Below are the records for our climate sites

Site Record June 23rd Record June 24th

Portland Jetport 91 (1983) 93 (1976)
Augusta 89 (1999) 93 (1963)
Concord 94 (2020) 95 (1980)

GYX WATCHES/WARNINGS/ADVISORIES
ME...Extreme Heat Watch from Tuesday morning through Tuesday evening for MEZ012>014-018>022-033.
Heat Advisory from 11 AM to 8 PM EDT Sunday for MEZ018-023.
Beach Hazards Statement until 8 PM EDT this evening for MEZ024>028.
NH...Heat Advisory from 11 AM to 8 PM EDT Sunday for NHZ007-008- 010>015.
Extreme Heat Watch from Monday morning through Tuesday evening for NHZ005>013-015.
MARINE...Small Craft Advisory from 7 AM to 8 PM EDT Sunday for ANZ150- 152-154.