Marine Weather and Tide Forecast for Belfast, ME

NEAR TERM /UNTIL 7 AM TUESDAY MORNING/
8 PM Update...Latest radar shows a band of rain with embedded convection across south central NH into interior SW Maine. This area of convection will continue to slowly track SSE over the next couple of hours and weaken as it reaches the coast. Main concern will be torrential downpours within the heavier cells while the need for short fuse flood advisory products looks low.
Have mainly refined PoPs to reflect the latest observed trends with this update.

Previously...

Showers and thunderstorms continue to develop this afternoon.
Main concerns with these will be heavy rainfall and gusty winds.
Showers or storms will be capable of 1 to 2 inch per hour rainfall rates, with stronger storms moreso. Locations that see multiple rounds or training of storms will be prone to flash flooding through early evening.

Clouds have thinned through the morning and early afternoon, allowing insolation to continue building instability. Locked in a very moist airmass with a high freezing level, the combination points to great precipitation efficiency via warm rain processes.

The cold front that will eventually wick away much of this deep moisture is still draped across southern Quebec, thus expect scattered to widespread shower development for much of the CWA through the afternoon and early evening hours. More stable air is positioned along the Midcoast, and have left a good portion of this region with lower PoPs through the evening.

The front will take much of the evening to track through to the coast, and this may prolong shower activity through midnight via frontal forcing. Will lose a lot of the surface based instability, but elevated CAPE continues for much of the night.
Despite the current falloff in precip chances, could still see a couple clusters of showers sustaining for much of the night.

Because of the slow, weakening nature of the cold front, have kept some mild overnight lows in place for southern and central NH. Lows in the lower 70s and upper 60s will be a good jump on warming temperatures into Tuesday.

SHORT TERM /7 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/
Clearing skies across much of the CWA will be a welcome sight after days of stratus and mixed skies. While the passing front will help clearing deeper moisture, there remains a moist layer that will seed a population of cumulus once mixing and daytime heating takes hold. There will be the slight chance of a shower in southern NH, with CAMs depicting a few across southern NH.
Not certain on their longevity considering the dry air aloft, but taller clouds could mute afternoon temperatures.

Temperatures will warm into the 80s and close to 90 for some interior, southern locations. Remaining humidity across southern NH will push heat index values close to 95, and have issued a Heat Advisory for portions of Hillsborough and Rockingham counties. This heat will start a stretch of hot temperatures that expand in area and intensity into Wednesday and Thursday.

LONG TERM /WEDNESDAY THROUGH MONDAY/
Pattern Overview: Shortwave ridging peaks overhead on Wednesday allowing heat and humidity to peak as well. A shortwave trough crosses Thursday bringing a chance for showers and thunderstorms, but the better day looks like Friday as additional forcing comes in the form of a surface front. Zonal flow through the weekend will keep afternoon showers in the forecast with some suggestion that a sharper trough may approach early next week.

Impacts and Key Messages: * Heat and humidity peak midweek with heat indices reaching the mid to upper 90s in southeastern New Hampshire and southwestern Maine.

Details: Wednesday: Confidence is increasing in advisory level heat indices Wednesday as models trend warmer with 850 mb temps (now approaching 19C). Low level flow turns southwesterly as 500 mb heights peak overhead, driving dewpoints up around 70F.
These combined result in many locations with temperatures in the low 90s, feeling more like the mid to upper 90s. Dewpoints stay lower north of the mountains so heat indices will stay closer to the actual temperatures (in the upper 80s to around 90).
There also may be enough of a sea breeze to keep heat indices on the lower side along the coast. The main areas of concern are the inland areas south of the mountains, and Heat Advisories will likely have to be issues accordingly. Elevated dewpoints keep temperatures from dropping too much south of the mountains with fog and low stratus likely to develop as well. Low temperatures only bottom out around 70 in southern zones, and in the low to mid 60s to the north. An approaching shortwave trough also brings a low chance of showers, mainly to the mountains, overnight.

Thursday and Friday: Thursday sees increasing clouds and shower/thunderstorm chances as a shortwave trough crosses the area. CSU machine learning continues to show low probabilities that a few storms could be on the stronger side. Long range ensembles are showing another surge in moisture during this time frame with the continued southwesterly flow driving PWATs up across the area, so these probabilities are likely stemming from precip loaded storms. With that being said any storms would be capable of producing heavy rain which could lead to localized flooding. Dewpoints peak in the low to mid 70s on Thursday, but surface temperatures will be a degree or two cooler than the day before. Despite the cooler temperatures, higher dewpoints likely will necessitate Heat Advisories for Thursday as well.
Thursday remains a warm night with temperatures similar to Wednesday night. Friday looks very similar with the addition of a surface front that would provide further forcing potentially leading to more widespread showers/storms. Trends will have to be watched during this time period as timing of fronts is always tricky, but nonetheless CSU continues to show low probabilities of stronger storms and WPC has targeted these days with Marginal Risks for the heavy rain potential. Depending on the timing of the front there is likely going to be an interesting temperature gradient with locations behind the front dropping into the 70s with lower humidity and locations ahead of the front during peak heating in the mid to upper 80s with humidity holding strong. If the front does clear the area by nightfall, it would make for a cooler night as well.

Saturday-Monday: A drier airmass is ushered in behind the front for the weekend with temperatures feeling much more pleasant.
Zonal flow aloft, with some suggestion of brief shortwaves rotating through, keeps low chances of pop-up afternoon showers and storms in the forecast. Global models than suggest a sharper trough and surface low pressure develop early next week which may be the next best chance for widespread showers and storms, but this is still out in time and unsurprisingly models greatly vary in representation of this feature, so its only worth a mention for now.

AVIATION /00Z TUESDAY THROUGH SATURDAY/
Short Term...There remains scattered MVFR decks today as SHRA and TS develop. The trend will be for these to raise, with northern areas seeing thinning this evening. Another night of IFR to LIFR expected for the Midcoast up to perhaps AUG.
Elsewhere, thinning takes longer through midnight. SHRA and TS may contain heavy downpours, with gusty winds on the periphery of any downdrafts. VFR expected Tuesday, with a fog bank possibly remaining just off the coast. This may continue to march inland after sunset Tuesday evening. Cumulus develops through the day, with outside chance of a VCSH in southern NH.

Long Term...Low stratus and fog will be present Wednesday morning, overnight Wednesday, and Thursday morning bringing about IFR/LIFR restrictions. Ceilings during the day Wednesday should be VFR with more in the way of MVFR ceilings looking likely with widespread shower activity and a few afternoon thunderstorms Thursday and Friday.

MARINE
Short Term...Conditions remain below SCA with fog occasionally obscuring visibility. A cold front will approach and then stall over the waters late tonight/Tuesday morning.

Long Term...Wind gusts and seas remain below SCA criteria through Friday. Increasing southwesterly flow will continue areas of fog development through at least Friday morning.
Afternoon showers and thunderstorms may also move over the waters on Thursday and Friday.

GYX WATCHES/WARNINGS/ADVISORIES
ME...None.
NH...Heat Advisory from 11 AM to 8 PM EDT Tuesday for NHZ012-013.
MARINE...None.