Cape Cod Bay Marine Forecast
|Rest Of Tonight...Nw Winds Around 5 Kt. Seas 1 Foot Or Less. A Slight Chance Of Showers.|
|Sat...Nw Winds 5 To 10 Kt. Gusts Up To 20 Kt In The Afternoon. Seas Around 2 Ft.|
|Sat Night...Nw Winds 10 To 15 Kt, Becoming W 5 To 10 Kt After Midnight. Gusts Up To 20 Kt. Seas Around 2 Ft.|
|Sun...W Winds 5 To 10 Kt. Gusts Up To 20 Kt In The Morning. Seas Around 2 Ft.|
|Sun Night...S Winds 5 To 10 Kt. Gusts Up To 20 Kt In The Evening. Seas Around 2 Ft.|
|Mon...Se Winds 10 To 15 Kt With Gusts Up To 20 Kt, Increasing To 20 To 25 Kt With Gusts Up To 35 Kt In The Afternoon. Seas 2 To 4 Ft. Showers Likely. Vsby 1 To 3 Nm.|
|Mon Night...S Winds 20 To 25 Kt With Gusts Up To 40 Kt. Seas 3 To 5 Ft. Showers. Vsby 1 To 3 Nm.|
|Tue And Tue Night...Sw Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas 2 To 4 Ft. A Chance Of Showers.|
|Wed And Wed Night...Sw Winds 15 To 20 Kt, Becoming W 10 To 15 Kt. Gusts Up To 25 Kt. Seas 2 To 3 Ft. Seas Are Reported As Significant Wave Height, Which Is The Average Of The Highest Third Of The Waves. Individual Wave Heights May Be More Than Twice The Significant Wave Height.|
| Area Forecast Discussion|
National Weather Service Boston/Norton MA
1251am EST Sat Nov 28 2020
High pressure will bring mainly dry and quiet weather through Sunday. Strong low pressure lifts through New York State Monday. This will bring the potential for strong winds and heavy rain. Above normal temperatures early in the week trend seasonably cold midweek, then above normal again late week.
Near Term - Until 6am This Morning
While most of the region was dry very early this morning, there were a few brief passing sprinkles still showing up on radar. This activity will be ending shortly as shortwave departs with mainly just trace amounts. Otherwise, expect a fair amount of strato-cu to persist through daybreak given ample low level moisture. We do expect at least a few brief breaks although the extent of those remains uncertain. Low temps should bottom out in the 35 to 45 degree range by daybreak. Coolest readings should be across interior MA, especially if we can see enough breaks develop in the strato-cu. We also expect some patchy fog in the typical spots, but not nearly as widespread/dense as yesterday.
Short Term - 6am This Morning Through 6pm Sunday
Colder air continues to move across our region. Still looking at one more mid level shortwave to pass us by with the cold pool aloft. The humidity associated with this feature is limited, so just expecting mainly clouds. Trend in the guidance has been for less of a risk for showers, but it will not be zero. Expecting clearing to develop during the afternoon into the evening behind this shortwave. This clearing continues into Saturday night. High pressure becomes more of a factor Saturday night.
Above normal temperatures continue Saturday. how much above normal will depend upon how quickly the clouds break up. Thinking max temperatures about 5 degrees lower than today. Low temperatures Sunday morning should be near normal as colder air continues to overspread our region.
Long Term - Sunday Night Through Friday
Big Picture... Upper flow starts with separate northern and southern jet streams going into the weekend. Shortwaves, one in each stream, merge over the Mississippi Valley Sunday night and Monday. This creates a closed low over the Midwest Monday that ejects through NY into Canada Tuesday and Wednesday.
Upper contours are above normal values over the weekend and on Monday, then crash below normal Tuesday and Wednesday as the upper low passes to our west. Contours then build to normal Thursday and Friday. This suggests above normal temps early with a below normal period during midweek, then a return to normal late week.
Mass fields and thermal fields are similar among the models through midweek, then greatly diverge next Thursday and Friday. Forecast confidence is good through midweek, then turns poor late next week.
Details... Sunday and Monday... High pressure over the Eastern USA Sunday morning moves offshore by evening. This maintains subsidence over New England Sunday and resulting mostly sunny, fair weather. Warm advection aloft will limit the depth of mixing Sunday. Temperatures at 950-mb support max surface temps in the upper 40s and lower 50s. If mixing reaches to 925- mb, max temps would climb into the 50s.
Fair skies Sunday night, although expect increasing mid/high clouds especially late at night. With dew points in the 30s, expect min temps before the arrival of clouds will be in the 30s.
Southern stream shortwave directly supports a surface low over LA/MS, and the digging northern stream shortwave will turn the Eastern USA flow from the southwest and eventually from the south. This will draw the weather system and its moisture up the Appalachians and over the Northeast USA. This pulls the surface low up through PA/NY with a broad south flow over Srn New England. The south flow draws higher than normal PW values...1 inch to 1.3 inches...into our area for Monday, suggesting wet weather with occasional downpours. Increasing surface pressure gradient supports increasing wind on Monday with sustained winds 25-35 mph. Low level jet reaches 60-70 kt at 2000 feet above the surface, which suggests potential wind gusts reaching 40-45 kt especially along the coastal plain. Will continue with the rainy/windy forecast for Monday. With 950-mb temps around 10C, forecast has max surface temps in the 50s, possibly low 60s in a few spots.
Tuesday-Wednesday... Surface cold front sweeps east of Srn New England by Tuesday morning. The passage of the upper flow will bring cold advection aloft Tuesday, destabilizing the airmass and generating scattered showers. Cold advection extends to the surface Wednesday with mixing to 850-mb...that will only support max surface temps in the 40s. Mixing will draw southwest gusts of 30 kt to the surface.
Thursday-Friday... Upper trough pulls out through Eastern Canada. Global models show another trough sweeping east from the Plains, but with differences on its evolution. Offshore high pressure will provide dry weather Thursday and much of Friday, but with increasing potential of precipitation during Friday night.
Winds will briefly diminish tonight into Saturday, before picking up again late Saturday and Saturday night as colder air moves over the waters. Thinking gusts up to 20 kt, with seas approaching 5 ft across the outer coastal waters during that time. Later shifts may consider Small Craft Advisories if winds are forecast to be stronger.
Small Craft Advisories should be able to expire later this afternoon across the southern outer coastal waters, where rough seas continue to subside into this evening.
Outlook /Sunday Night through Wednesday/... Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.
Sunday Night: Winds less than 25 kt.
Monday: Low risk for gale force winds with gusts up to 40 kt. Local rough seas. Rain showers.
Monday Night: Moderate risk for gale force winds with local gusts up to 45 kt. Rough seas up to 16 ft. Rain showers.
Tuesday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 12 ft. Chance of rain showers.
Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 13 ft. Chance of rain showers.
Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 11 ft. Slight chance of rain showers.
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None. MARINE...None.