Penobscot Bay Marine Forecast
|Overnight...W Winds Around 5 Kt, Becoming N Late. Seas 1 Foot Or Less.|
|Thu...E Winds 5 To 10 Kt, Becoming Se With Gusts Up To 20 Kt In The Afternoon. Seas 1 Foot Or Less.|
|Thu Night...E Winds 5 To 10 Kt, Increasing To 10 To 20 Kt With Gusts Up To 25 Kt After Midnight. Seas 1 Foot Or Less, Then 1 To 2 Ft After Midnight. A Chance Of Rain After Midnight.|
|Fri...Ne Winds 15 To 25 Kt With Gusts Up To 35 Kt. Seas 2 To 4 Ft. Snow, Rain.|
|Fri Night...Ne Winds 15 To 25 Kt With Gusts Up To 35 Kt. Seas 2 To 4 Ft. Rain In The Evening, Then Rain With Snow Likely After Midnight.|
|Sat...N Winds 10 To 20 Kt With Gusts Up To 25 Kt. Seas 2 To 4 Ft. Rain Likely In The Morning, Then A Chance Of Showers In The Afternoon.|
|Sat Night...N Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 2 To 3 Ft.|
|Sun...Nw Winds 5 To 10 Kt, Becoming W In The Afternoon. Seas Around 2 Ft.|
|Sun Night...Sw Winds Around 5 Kt. Seas 1 Foot Or Less.|
|Mon...Sw Winds 5 To 10 Kt. Seas 1 Foot Or Less, Then Around 2 Ft In The Afternoon.|
|Mon Night...W Winds 5 To 10 Kt. Seas Around 2 Ft.|
| Area Forecast Discussion|
National Weather Service Gray ME
936pm EDT Wednesday April 14 2021
Low pressure develops south of New England on Thursday and tracks into the Gulf of Maine Friday night. Rain will begin late Thursday and quickly change to snow Thursday night as colder air wraps into the system. Heaviest accumulations are likely in the higher terrain, but accumulations are possible all the way to the coast. Low pressure moves away on Saturday with dry and mild weather expected for the rest of the weekend and into next week.
Near Term - Until 6am Thursday Morning
9:40pm Made some minor adjustments to temperature and dew points based on surface observations and trends. Also tweaked cloud cover to better align with satellite imagery, which shows a band of high level cirrus clouds moving through central NH while the majority of western ME remains mostly clear. Radar shows a few light rain showers/sprinkles from roughly Plymouth, NH down to Concord, NH but dew point depressions remain large and the 00Z KGYX sounding shows a significant dry layer aloft. As a result, the majority of these returns are like virga but nonetheless, Probability of Precipitation was adjusted some to account for this activity. The rest of the forecast remains on track.
Previously... 6:00pm Made some minor adjustments to temperatures and dew points based on surface observations and trends. KGYX radar shows a well defined sea breeze continuing to advance inland with surface observations showing noticeably higher dew points and cooler temperatures behind this boundary. As of 21Z, KPWM was at 48 degrees whereas KIZG was sitting at 63 degrees. The only expected forecast challenges this evening will be sky cover and low temperatures. Areas that remain mostly clear will radiate quite well versus those that remain overcast. Some adjustments were made to account for this based on guidance but otherwise the forecast remains well on track.
Previously... Current GOES water vapor imagery shows an upper low spinning over the northern Great Lakes. This upper low will start to slide southeast tonight with moisture being drawn into New England. Mostly dry weather is expected tonight with a slight chance for showers over New Hampshire with increasing clouds toward daybreak. Northern and eastern zones will see mostly clear skies tonight allowing for good radiational cooling and lows dropping to near the freezing mark. Over southern and western zones clouds will keep lows in in the mid 30s to low 40s.
Short Term - 6am Thursday Morning Through Thursday Night
Thursday into Thursday night, the upper low will tracking towards Long Island, NY with cyclogenesis taking place off the Mid-Atlantic. The surface low will deepen as it tracks towards the 40/70 benchmark Thursday evening. This system will draw in moisture from the Atlantic during the day Thursday with chances for rain increasing across western New Hampshire late morning into the afternoon. Highs on Thursday will be in the mid 50s across northern and eastern zones where there will be more sun. Across southern and western New Hampshire temperatures will be cooler due to cloud cover and diabatic effects from the onset of rain.
Thursday night the upper low elongates in negative tilt fashion leading to further intensification of the surface low. A mix of rain and snow Thursday evening will quickly change to snow over elevations above 800 feet in SW New Hampshire. The surface low will track north over Cape Cod by Friday morning with precipitation spreading north and eastward over night.
The Monadnock Region into the White Mountains will see heavy precipitation Thursday night with snowfall rates around 1 inch per hour from around midnight towards day break. Given that we have a warm ground and it being April accumulations will be much lower than would be in winter, but 3-6 inches of heavy wet snow above 800 feet is looking like reasonable amount for hill towns across southwestern New Hampshire into the White Mountains by daybreak. Precipitation will continue into Friday with additional accumulation. There is concern that this heavy wet snow will load onto trees and snapping tree limbs causing scattered power outages by Friday morning. A Winter Storm Watch has been issued starting Thursday evening over portions of New Hampshire to highlight the potential for scattered power outages Thursday night into Friday.
The heavier precipitation will enter into Maine after midnight with rain likely near the coast with a rain snow mix along the interior changing heavy wet snow with elevation. Along the interior into the western Maine mountains things will be ramping up towards daybreak with a couple inches of snow possible. Coastal areas will likely experience a cold, wind driven rain and the morning commute here will likely not be impacted by snow. Winds will be ramping up Thursday night with gusts along the coast approaching 30 to 40 mph by morning. A Winter Storm Watch has been issue for mountain zones in Maine Starting after midnight with further details on the system Friday in the extended forecast discussion.
Long Term - Friday Through Wednesday
Models continue to be in good agreement for an ongoing duration of snow lingering into the overnight hours of Friday night. During the daytime on Friday it will be difficult to observe much in the way of snowfall accumulation outside of any heavy snowfall rates, but after dark on Friday the ability to accumulate will increase as the forcing for precipitation is waning across interior Maine, the Midcoast, and the White Mountains region of New Hampshire.
The expected evolution of the storm track remains consistent at this time, with a low deepening and occluding across southeastern New England by midday Friday, remaining nearly stationary for about 12- 18 hours, then exiting the Gulf of Maine toward the east-southeast. Global models are in agreement on this, and as the system continues to come into the high res guidence's view they are also showing this. The high res guidance also offers insigheights into where the more likely locations to experience banding are.
Much of the MidCoast and Central Maine appear to be the most likely locations to see a longer duration of moderate precipitation rates on Friday, as well as seeing the snow falling during the nighttime hours when it is easier to accumulate, but the forcing will be decreasing during this time period.
The snow is expected to be a heavy and wet snow, with a high degree of compaction limiting the amounts that will be observed on the ground by the end of the storm. Because of this, the impacts of snow loading on the trees may appear disproportionate to the amounts observed.
Precip is likely to lighten up late morning and early afternoon on Friday, and temperatures will warm enough to produce rain at times during the day when the precipitation is light enough. Much of southeastern and south central New Hampshire and the southwest coast of Maine appear they will be in the dry slot for much of the day on Friday, which would allow temps to creep into the mid to upper 30s with showers and drizzle. Southwestern NH appears to be the best place to see accumulating snow lasting into the morning hours, before precipitation gradually winds down in the afternoon.
Models are then showing an enhancement in precipitation intensity late in the day and into the evening Friday across Central Maine and the MidCoast, but just how much the precipitation is able to fill back in remains lower confidence at this time.
An additional feature of this system will be gusty northeast winds along the coastline, with wind gust up to 40mph likely. The wind direction with the system is also likely to lead to downsloping conditions to the southwest of the Whites, likely leading to lesser precipitation amounts through the Pemi River Valley.
Astronomical tides are near their lowest of the monthly cycle, so at this time some minor splashover Friday night appears to be the high end threat in terms of coastal flooding concerns.
The system will then pull away from the region early Saturday, with improving conditions during the day on Saturday. We'll return to a pattern of finding ourselves between several cut off low pressure systems positioned across eastern North America, with moderating temperatures into the first half of the work week. My midweek a frontal boundary is likely to cross New England, bringing temperatures closer to normal for the second half of the work week.
Low pressure approaches from the south Thursday into Thursday night. Winds and seas remain below SCA (Small Craft Advisory) through Thursday with northeast gusts ramping up Thursday night. Gusts will surpass 25 kts after midnight and will approach gale force by Friday morning with building seas.
Long Term... Low pressure will meander around Cape Cod Friday and Friday night, before departing the Gulf of Maine on Saturday. Gales are likely during the day on Friday and early Friday night, accompanied by seas building above 10ft. Winds will ease overnight Friday as the system weakens and pulls away, with seas lowering below SCA (Small Craft Advisory) criteria Sunday morning. Fair conditions will encompass the waters for Sunday and the first half of next week.
NOAA Gray/Portland ME Office - Watches - Warnings - Advisories
ME...Winter Storm Watch from late Thursday night through late Friday night for MEZ007-008-012-013-033. NH...Winter Storm Watch from Thursday evening through Friday evening for NHZ002>009-011-015. MARINE...Gale Watch from Friday morning through Friday evening for ANZ150>154.