Casco Bay Marine Forecast
|This Afternoon...Sw Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas 2 To 4 Ft. A Slight Chance Of Showers.|
|Tonight...Sw Winds 5 To 15 Kt With Gusts Up To 20 Kt, Becoming 5 To 10 Kt After Midnight. Seas 2 To 4 Ft. Showers Likely.|
|Tue...Sw Winds 5 To 10 Kt. Seas 2 To 3 Ft. A Chance Of Showers In The Afternoon.|
|Tue Night...Nw Winds 5 To 10 Kt. Seas 2 To 3 Ft.|
|Wed...Nw Winds 5 To 10 Kt, Becoming Sw In The Afternoon. Seas 2 To 3 Ft.|
|Wed Night...Sw Winds 5 To 10 Kt. Seas 2 To 3 Ft.|
|Thu...Sw Winds 5 To 15 Kt With Gusts Up To 30 Kt. Seas 2 To 4 Ft. A Chance Of Showers.|
|Thu Night...W Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 2 To 4 Ft.|
|Fri...W Winds 5 To 10 Kt. Seas 2 To 3 Ft.|
|Fri Night...Sw Winds Around 5 Kt. Seas 2 To 3 Ft.|
Area Forecast Discussion|
National Weather Service Gray ME
313pm EDT Monday September 23 2019
Low pressure will work into the region tonight before shifting east of the region on Tuesday. This will result in a trend to cooler temperatures with scattered to numerous rain showers and a possible thunderstorm. High pressure works back into the region on Wednesday with mild and dry conditions. Another round of showers is possible with an approaching cold front on Thursday and Thursday night before high pressure returns to end the work week on Friday.
Near Term - Until 6am Tuesday Morning
High Impact Weather Potential: Isolated thunderstorms tonight.
Pattern: Early afternoon water vapor imagery reveals a mobile shortwave over the Great Lakes region steadily marching towards New England with modest moisture plume to it/s east. Beneath this mid level feature...weak cyclogenesis has occurred north of upstate New York along a NE to SW oriented cold frontal boundary. In the broad warm advection region ahead of this front...there has been a region of scattered rain shower activity. Through the near term forecast period...our focus will turn from showers ahead of the front to the front itself...as arriving upstream shortwave will provide rather impressive dynamic forcing for ascent as it overspreads the area tonight.
Through this evening: A very summerlike airmass to begin fall out there this afternoon with temperatures in many portions of southern NH and southwestern ME reaching into the middle/upper 80s with dewpoints in the 60s. The Jetport/PWM has reached a new record high /88 as of 2pm/.
Tonight: Low pressure near Montreal this evening moves east southeast through tonight with associated cold front pushing through the forecast area. Dynamic forcing will increase markedly from this afternoon...as height falls associated with approaching upstream shortwave overspread the region concurrent with arriving poleward exit region of H2 jet max. Pattern recognition suggests...and recent mesoscale models confirm that this should result in a more robust region of showers that marches through the area overnight. Deepest moisture and best llevel convergence will be over our northern zones...with highest Quantitative Precipitation Forecast likely here. South of the mountains... expect the line of showers to potentially be more broken with Quantitative Precipitation Forecast amounts less. Lows will again be mild as the cold front doesn't really clear the region until daybreak. Expect values in the 50s in the mountains with 60-65 likely over the coastal plain and foothills.
Thunder: Deterministic and ensemble solutions favor 500-750 J/kg of SBCAPE across much of the region overnight which supports a continued thunder mention although skinny CAPE profiles indicate a rather limited severe weather threat. This is consistent with upstream regional radar trends which have shown some embedded thunderstorms over western New York.
Short Term - 6am Tuesday Morning Through Tuesday Night
High Impact Weather Potential: Isolated thunderstorms possible Tuesday.
Tuesday: Core of mid level low passes overhead with T5s just above -20C. At the surface...low pressure will be over eastern Maine at 12Z...moving east during the day. Thus...we/ll see a destabilizing airmass in the presence of ample boundary layer moisture and moist...cyclonic northwest flow. This should spell and abundance of shower activity especially 1) in the upslope areas and 2) in the afternoon given increased destabilization. There should be enough instability to support shower activity in the downslope areas as well /Froude number >0/...but expect potentially less coverage in this area. Model sounding profiles portray a few hundred J/kg of MLCAPE by afternoon which supports a mention of isolated thunder. Weak mid level flow and the lack of more significant instability precludes any severe weather threat. Despite the unsettled post- frontal airmass...we/ll still be relatively mild aloft /T8s +8-10C/ and therefore expect temperatures to again be at or above seasonal norms... particularly in the downslope areas south and east of the mountains. Here...highs in the lower/middle 70s look good with values in the 60s to the north.
Tuesday Night: Closed low at H5 pulls east of our longitude as a narrow high pressure ridge axis edges into the region from the west. This will weaken ongoing cyclonic flow as boundary layer moisture wanes. Therefore, expect evening shower activity to gradually wane through the overnight with a few mountain showers likely to persist after midnight with ample clouds north of the mountains...but partial clearing to the south. The overhead airmass will be cooler as the H5 wave pulls east...but with remaining cloud cover it will still be a relatively mild night with lows in the upper 40s north of the mountains through the lower 50s to the south.
Long Term - Wednesday Through Monday
Models continue to favor a building ridge across the eastern half of the CONUS, which should allow for above normal temps thru much of the long term. Several weak waves move thru , on Thu and Sat, but, but air behind these systems is still a little above normal, which lasts for a day before temps climb back up again.
Wednesday will be dry with temps warming as surface high passes to our south. Sea breeze will temps the warming somewhat in coastal areas, and highs range from the low-mid 60s in the mtns to the low to mid 70s in the south. Next front arrives on Thu with decent SW flow setting up ahead of it should see highs range from around 7o in the north to near 80 in the south. The cold front will set off some showers, especially in the mtns during the afternoon, but will still see a fair amount of sun through much of the day in the south.
Temps cool a bit for Fri with highs mid 60s to mid 70s again, but approaching cold front on Saturday will again help to channel the warm SW flow ahead of it and highs will rise to into the 70s most places to near 80 in the warmer spots of southern NH. There will be a threat for showers, in the afternoon in the N, but late in the day and Sat evening in the south. Temps cool a bit for Sunday and Monday, but still run above normal with generally dry conds.
Low pressure north of New England will pass into the Gulf of Maine overnight before gradually moving east into the Canadian maritimes Tuesday night. This will allow southwesterly winds and associated waves to subside with SCA (Small Craft Advisory) conditions coming to an end by Tuesday morning with headline-free conditions Tuesday and Tuesday night.
Long Term...Enhanced SW flow and swell associated with Karen could push seas 5 ft or so Thu into Thu night.
NOAA Gray/Portland ME Office - Watches - Warnings - Advisories
Small Craft Advisory until 6am EDT Tuesday for ANZ150-152-154.