Casco Bay Marine Forecast
| Tonight...S Winds 10 To 15 Kt With Gusts Up To 20 Kt, Diminishing To 5 To 10 Kt After Midnight. Seas 2 To 4 Ft. Areas Of Fog Until Early Morning. Areas Of Fog Towards Daybreak. Showers With A Slight Chance Of Tstms After Midnight. Vsby 1 Nm Or Less Late This Evening And Early Morning, Increasing To 1 To 3 Nm. |
| Mon...S Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 2 To 4 Ft. Showers, Mainly In The Morning. Areas Of Fog. Vsby 1 To 3 Nm. |
| Mon Night...Sw Winds 15 To 20 Kt With Gusts Up To 30 Kt, Diminishing To 10 To 15 Kt With Gusts Up To 20 Kt After Midnight. Seas 2 To 4 Ft. Showers Likely In The Evening With Vsby 1 To 3 Nm. |
| Tue...W Winds Around 10 Kt. Seas 2 To 4 Ft. |
| Tue Night...Sw Winds 5 To 10 Kt, Becoming W After Midnight. Seas 2 To 3 Ft. |
| Wed...Sw Winds Around 5 Kt, Becoming S In The Afternoon. Seas Around 2 Ft. |
| Wed Night...S Winds 5 To 10 Kt, Becoming Sw After Midnight. Seas Around 2 Ft. |
| Thu...Sw Winds Around 5 Kt, Becoming S In The Afternoon. Seas Around 2 Ft. |
| Thu Night...S Winds 5 To 10 Kt, Becoming Sw After Midnight. Seas Around 2 Ft. |
| Fri...Sw Winds Around 5 Kt, Increasing To 5 To 10 Kt In The Afternoon. Seas Around 2 Ft. A Chance Of Showers In The Afternoon. |
| Fri Night...Sw Winds 5 To 10 Kt, Becoming W After Midnight. Seas Around 2 Ft. Winds And Seas Higher In And Near Tstms. |
| Area Forecast Discussion National Weather Service Gray ME 223pm EDT Sunday August 2 2026 .WHAT HAS CHANGED... Progression of the frontal passage has slowed for Monday. .KEY MESSAGES... 1.Showers and thunderstorms increase in coverage later tonight and persist into Monday as a cold front crosses the region. 2. Humid conditions persist through the remainder of the week with chances for scattered afternoon thunderstorms. KEY MESSAGE 1 DESCRIPTION... An upper-level trough over eastern Canada will deepen and carve south into New England tonight into Monday. Guidance continues to favor a slightly slower eastward progression, with the trough potentially closing off. Deep southerly to southwesterly flow will advect a plume of moisture rich air into the region, driving PWATs (Precipitable Waters) values around 2.0 inches, within an environment with deep warm-cloud depths (>13kft). The overnight timing will limit overall intensity, and should start Monday off with mostly cloudy conditions. The cloud cover will be a defining driver on intensity of any storms throughout Monday as upper levels become more favorable with ascent increasing throughout the day. Increasing large-scale ascent on Monday will interact with modest instability (CAPE 500-1000j/kg) will produce multiple rounds of heavy showers and thunderstorms. As things currently look, we can expect tall, skinny CAPE profiles, with a high moisture content, and efficient warm rain collision-coalescence processes. Translation, when it rains it will pour. The storms should be progressive, which should keep most storm total accumulations around 0.5-1”. However, the storm movements will be running parallel to the frontal boundary, increasing the potential for storm training and backbuilding with FROPA. Dry antecedent conditions with ample runoff storage reduces the widespread flood risk, however localized areas could quickly accumulate 3”+, so we can’t rule out an isolated risk of flash flooding. Higher terrain may experience localized upslope ascent, further elevating rainfall efficiency and flash flood threats. WPC has the region in a level 1 of 4, a marginal risk for localized flash flooding. At this time it is hard to pin point exactly where the highest risk for flooding would occur, and given dry antecedent conditions, have held off on a flood watch. In addition to the excessive rainfall threat, Storm Prediction Center maintains a Marginal Risk (Level 1/5) for severe weather for Monday afternoon; the primary hazard will be localized damaging wind gusts from water- loaded downbursts. CAMs continue to suggest that storms will develop along the cold front moving west to east across the area, strengthening in New Hampshire towards peak heating. As mentioned above, we will see some modest instability with MLCAPE in the 500 to 1000 J/kg range. The instability along the front will be collocated with 40 to 45 knots of effective layer shear. Thus, the more established updrafts will have the potential to produce some isolated damaging wind gusts. As is often the case around here, much of the severe potential will depend on how much New Hampshire can clear out after the morning convection moves through. If we get some more breaks, we could see pockets of MLCAPE closer to that 1000 J/kg value but if we remain socked in, instability will be more limited. KEY MESSAGE 2 DESCRIPTION... Tuesday through Friday... The frontal boundary will weaken south of the region on Tuesday, providing fair conditions and a brief reduction in the heat/humidity. By Wednesday through the weekend, the broad upper level trough shifts back over the Great Lakes, and with the Bermuda High offshore establishing deep southwesterly flow across the area. This will support warm and humid conditions, with shower and thunderstorm chances (25–35%) diurnally driven. Some guidance is showing embedded shortwave energy Thursday that could enhance coverage, so have highest probability of precipitation at that point in the extended period. While exact timing and intensity remain uncertain this far out, diurnal heating will favor the highest storm coverage during the afternoon and evening hours. Marine Winds and seas expected to remain below SCA (Small Craft Advisory) thresholds today. However, an increase in winds and seas will likely lead to SCA conditions developing by late Monday morning through Monday night. Areas of fog will develop again tonight, locally dense at times. Additionally, chances for widespread showers and storms increase overnight into Monday. After seas and wind relax Tuesday morning, we should remain below SCA (Small Craft Advisory) criteria through the extended. NOAA Gray/Portland ME Office - Watches - Warnings - Advisories ME...None. NH...None. Marine Small Craft Advisory from 10am Monday to 8am EDT Tuesday for ANZ150-152-154. Small Craft Advisory from 2pm Monday to 8am EDT Tuesday for ANZ151-153. |
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