Casco Bay Marine Forecast
| Tonight...Nw Winds 5 To 10 Kt. Seas 1 Foot Or Less. |
| Tue...Nw Winds 5 To 10 Kt, Becoming Sw In The Afternoon. Seas 1 Foot Or Less. |
| Tue Night...S Winds Around 5 Kt, Becoming E Around 5 Kt After Midnight. Seas 1 Foot Or Less. |
| Wed...Se Winds 5 To 10 Kt. Seas 1 Foot Or Less, Then Around 2 Ft In The Afternoon. |
| Wed Night...S Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 2 To 4 Ft. A Chance Of Showers In The Evening, Then Showers Likely After Midnight With Vsby 1 To 3 Nm. |
| Thu...Sw Winds 15 To 20 Kt, Diminishing To 10 To 15 Kt In The Afternoon. Seas 2 To 4 Ft. A Chance Of Showers In The Morning With Vsby 1 To 3 Nm. |
| Thu Night...W Winds 10 To 15 Kt With Gusts Up To 20 Kt, Becoming Nw 5 To 10 Kt After Midnight. Seas 2 To 4 Ft. |
| Fri...Nw Winds 5 To 10 Kt. Seas Around 2 Ft. |
| Fri Night...Nw Winds 5 To 10 Kt, Diminishing To Around 5 Kt After Midnight. Seas Around 2 Ft In The Evening, Then 1 Foot Or Less. |
| Sat...Ne Winds Around 5 Kt, Becoming S In The Afternoon. Seas 1 Foot Or Less, Then Around 2 Ft In The Afternoon. |
| Sat Night...S Winds 5 To 10 Kt. Seas Around 2 Ft. |
| Area Forecast Discussion National Weather Service Gray ME 802pm EDT Monday September 7 2026 .WHAT HAS CHANGED... Minor update to the Aviation section for the 00Z TAFs. .KEY MESSAGES... 1. A weak cold front will brush the area overnight with a chance of showers mainly for the northern half of the forecast area. 2. A seasonably strong low pressure system will drag a cold front across the area late Wednesday into Thursday with showers becoming likely late Wednesday and Wednesday night. 3. A period of gusty winds will be possible on Thursday behind the front with dry weather returning late week through at least Saturday. KEY MESSAGE 1 DESCRIPTION... Just a perfect early fall day out there today. Diurnal cumulus will dissipate after sunset and I expect mostly clear skies at least during the first half of the overnight. A backdoor cold front will be sagging towards the region late this evening, but I do not think that significant prevents radiational cooling early. As such I expect some valley fog to develop in the usual locations prior to the clouds invading the area. Showers will become more likely just before sunrise mainly across the northern half of NH and the western Maine mtns into the Kennebec River Valley. NBM Probability of Precipitation is pretty low given the CAM depiction of precipitation and Quantitative Precipitation Forecast, so I leaned on the HREF for timing and location and brought the values up to 30 or 40 percent. Briefly high pressure will drift across the region Tuesday afternoon thru the overnight. That should allow for good radiational cooling conditions again, despite return flow starting towards daybreak Wed. KEY MESSAGE 2 DESCRIPTION... High pressure slides east Wednesday as low pressure moves slowly east toward James Bay and sends a cold front toward New England. Increasing southerly flow will advect higher moisture into the region, potentially enough for some light showers across the north, but mainly it will begin to feel more humid out as dewpoints are forecast to climb into the upper 50s to lower 60s with skies becoming mostly cloudy. Temperatures may be limited to the 60s for northern areas due to more clouds while southern areas still reach the 70s. With the slower approach of the front, prospects for thunder have lowered. The better chances for showers arrive Wednesday evening and Wednesday night as the front enters the region and better support moves in aloft. PWATs (Precipitable Waters) increase to 1.70" to 2.00" which is well above the 90th percentile, meaning rain rates could be briefly heavy at times. But with the fast-moving nature of the system and drier antecedent conditions, not expecting any hydro issues. Models continue to favor the northern half of NH extending into the western ME mountains/foothills and Midcoast for the higher chances/more Quantitative Precipitation Forecast with ensemble means in pretty good agreement of 0.25-0.50" although there are some probabilities exceeding 0.50". Chances/amounts decrease with southern extent, and there are hints that southern NH sees less 0.10", which is certainly not ideal. KEY MESSAGE 3 DESCRIPTION... Any lingering showers will come to an end Thursday morning with much drier air moving in behind the initial front. West winds will also ramp up in the morning and afternoon as mixing brings down the higher winds from aloft and the surface low moves east toward the Maritimes. Based on forecast soundings, gusts of 25-35 mph appear likely, but there could be a few exceed 40 mph, per the top of the mixed layer. The cooler air doesn't move in until later in the day when a secondary front crosses, so it will be a pretty warm day with highs expected to be upper 70s to lower 80s south of the mountains. Temperatures cool back down closer to normal for Friday and Saturday with highs mostly in the 70s and plenty of dry air from high pressure building into New England to keep skies mostly sunny with low humidity. Friday night may bring excellent radiational cooling to bring widespread lows in the 40s and some 30s across northern valleys. The high shifts to the east by Sunday as another low pressure moves across the Hudson/James Bay region with its associated cold front approaching New England. This will bring another chance of showers either Sunday and/or Monday, which is supported by the 20-30% NBM Probability of Precipitation in this time window. Marine Winds and seas are expected to remain below SCA (Small Craft Advisory) thresholds thru Tuesday night. Then low pressure center moves east across Hudson Bay toward the Canadian Maritimes Wednesday into Thursday, which will send a cold front across the waters either late Wednesday night or early Thursday morning...and then a secondary front later in the day Thursday. Increasing south to southwest flow ahead of the fronts will likely reach SCA (Small Craft Advisory) levels from late Wednesday into the first part of Thursday, and then possibly for a period behind the second front Thursday night when winds turn west to northwesterly. Conditions improve Friday and Saturday as high pressure builds across the waters. The high shifts east Sunday into Monday as another front approaches from the west. NOAA Gray/Portland ME Office - Watches - Warnings - Advisories ME...None. NH...None. Marine None. |
Portland ME Radar
Northeast Radar