Casco Bay Marine Forecast
|Today...N Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 2 To 3 Ft. A Chance Of Light Snow This Morning, Then A Slight Chance Of Snow This Afternoon. Vsby 1 To 3 Nm.|
|Tonight...Nw Winds 15 To 25 Kt With Gusts Up To 30 Kt. Seas 2 To 4 Ft. Moderate Freezing Spray. A Chance Of Snow After Midnight With Vsby 1 To 3 Nm.|
|Fri...N Winds 20 To 25 Kt With Gusts Up To 35 Kt. Seas 2 To 4 Ft. Snow. Moderate Freezing Spray. Vsby 1 To 3 Nm.|
|Fri Night...N Winds 15 To 20 Kt, Becoming Nw 10 To 15 Kt After Midnight. Gusts Up To 30 Kt. Seas 2 To 4 Ft. Moderate Freezing Spray.|
|Sat...Nw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas Around 2 Ft. Light Freezing Spray.|
|Sat Night...Nw Winds Around 10 Kt With Gusts Up To 20 Kt. Seas Around 2 Ft. Light Freezing Spray In The Evening.|
|Sun...Nw Winds 5 To 10 Kt. Seas 1 To 2 Ft In The Morning, Then 1 Foot Or Less.|
|Sun Night...N Winds 5 To 10 Kt. Seas 1 Foot Or Less.|
|Mon...Ne Winds 10 To 15 Kt. Seas 1 To 2 Ft.|
|Mon Night...Ne Winds 15 To 20 Kt. Seas 2 To 3 Ft. A Chance Of Snow. Vsby 1 To 3 Nm.|
| Area Forecast Discussion|
National Weather Service Gray ME
408am EST Thu Jan 28 2021
A strong upper level low will move southeastward into New England tonight, bringing down the coldest air so far this season. Scattered snow showers and potentially a heavier snow squall will be possible on Friday. High pressure will build to our northwest this weekend with mostly tranquil weather and gradually moderating temperatures expected. There is potential that low pressure passing offshore may bring more significant snow to the area early next week.
Near Term - Until 6pm This Evening
Isolated light snowfall remains across the area this morning. 00Z KGYX sounding showed saturated lower levels, and this in combination with a very weak short wave has generated some light snow. While a few flakes may continue over the next few hours most areas should be dry. Skies will remain cloudy throughout the day.
Temperatures will peak fairly early in the day and start to fall rapidly in the afternoon as arctic air moves into the region.
Short Term - 6pm This Evening Through 6pm Friday
Far to our south low pressure over the Carolinas is generating some snowfall. Large pressure falls just offshore indicate this system is rapidly deepening as it moves out to sea. Meanwhile along the northern QC/ON border arctic air is poised to move into the region. As this cold air moves in and the low intensifies to our south we'll see another strong pressure gradient develop across northern New England with the result being gusty northwesterly winds. Winds will pick up late this evening and intensify through the daylight hours tomorrow.
Overnight low temperatures will fall to just below zero across the north, with a steady wind keeping things well mixed. This drops windchill to 20 to 25 below and a wind chill advisory has been issued for western NH. Further east won't be quite as cold, although certainly still chilly.
As far as precipitation goes, the core effects of the ocean storm remain well outside our region, however Friday morning we'll see a long skinny inverted trough thrust back towards coastal Maine. This feature will bring snow to the midcoast for Friday. There are several factors to consider for this event. First of all with the parent low so far offshore, the best dynamics and convergence with this trough will also be offshore, and how far inland it can extend will be a key question. This is a scenario where the coast, and especially the offshore islands will likely see significantly more snowfall than the mainland. In addition to the inland extent the snowfall rates and ratios will be important. This trough will likely focus the best lift into a very narrow band, and within this band rates of up to 2"/hr, as indicated by the HREF, are possible. Now the band is likely to be transient but any stalling will result in snow building up fast. Additionally expect snow ratios to be quite high, 20:1 or better due to the cold temperatures and strong dynamics. Putting this all together results in an area, mostly Knox county, seeing around 4" of snow in a few hours Friday morning. That said, there is the potential for reaching warning level snowfall in Knox county with probabilities of over 6" of snow around 20% at Isle au Haut.
Long Term - Friday Night Through Wednesday
N Hemisphere 500 MB continues to retain small and transient blocks poleward of 50N, with a more mobile wave/trough pattern between 30 and 50N. This does not instill a lot of confidence in the timing and amplitude of individual waves, but it does give the potential for some higher amplitude troughs and opens the door for some colder or warmer temps working equatorward/poleward. High confidence that the extended does start out cold this weekend.
Fri night will be cold and breezy, which will prevent rad cooling, but will produce another night of low wind chills generally in the single digits and teens below zero. The weekend looks mainly dry and generally clear in the south and partly cloudy in the mtns. Highs Sat range from 10-15 in the mtns to 20-25 in the south. Sat night will likely be the coldest night as winds subside and rad cooling develops with lows from -5 to -15 in the N, and generally zero to 5 above in the south. Sunday will be warmer as highs top out in the 20-25 range in the mtns and in the upper 20s in the S.
Still watching potential coastal low that models track out of the Carolinas and move N along the coast which would bring snow, and maybe some wind in the Monday night to Tuesday night timeframe, although there still remains a lot of uncertainty as to timing, track and intensity with a fairly large ensemble spread of both EPS and GEFS.
Arctic air will begin to move over the waters this afternoon. As it does NWly winds will accelerate and the Gale Watch has been upgraded to a Gale warning for the western water with SCA (Small Craft Advisory) in the bays. The combination of cold air and strong winds will lead to moderate freezing spray. With the coldest air in the western portion of the area have opted to issue a Freezing spray advisory just through Port Clyde, but that may need to be expanded through to Stonington if the colder air is able to infiltrate. Light freezing spray is expected to the east.
Long Term...Gales are likely to persist, especially in the open waters thru much of Fri night, but could begins to subside on Saturday, with SCA (Small Craft Advisory) like needed through Saturday. Winds/seas should then stay below SCA (Small Craft Advisory) into Monday, although may begin to pick up again Monday afternoon.
NOAA Gray/Portland ME Office - Watches - Warnings - Advisories
Small Craft Advisory from noon Friday to 1am EST Saturday for ANZ151-153. Gale Watch from late tonight through Friday morning for ANZ150- 152-154. Gale Warning from noon Friday to 1am EST Saturday for ANZ150- 152-154.