Massachusetts Bay and Ipswich Bay Marine Forecast
|Tonight...Sw Winds 10 To 15 Kt. Gusts Up To 20 Kt This Evening. Seas 1 Foot Or Less.|
|Fri...W Winds Around 10 Kt. Seas 1 Foot Or Less.|
|Fri Night...Nw Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 2 To 3 Ft.|
|Sat...Nw Winds 15 To 20 Kt With Gusts Up To 25 Kt, Increasing To 20 To 25 Kt With Gusts Up To 35 Kt In The Afternoon. Seas 2 To 3 Ft.|
|Sat Night Through Sun Night...Nw Winds 20 To 25 Kt With Gusts Up To 40 Kt. Seas 2 To 4 Ft.|
|Mon Through Tue Night...N Winds 10 To 15 Kt With Gusts Up To 20 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
349pm EST Thu Jan 21 2021
Mild afternoon tomorrow behind a warm front that moved through southern New England today will be followed by a strong cold frontal passage tomorrow night. This cold front will begin the transition to colder/blustery conditions for the weekend. Low pressure moving up from Texas will redevelop off the Mid- Atlantic coast early Tuesday. Much of the system should remain offshore, but it may bring some light snow to our area on Tuesday. Another weather system passes well south of the region Thursday.
Near Term - Until 6am Friday Morning
Light snow showers that developed late this morning ahead of a warm frontal boundary have since diminished leaving the region under overcast skies. A few observation stations are still reporting light snow, with light rain over P-Town. Not expecting this to last as the boundary layer remains very dry with dewpoint depressions generally ranging from 5-10 degrees.
West/southwest flow behind the warm front will persist through tomorrow morning before a cold front pushes through the region tomorrow night. The passing warm front and warm air advection aloft will support warmer overnight lows than this morning. Expecting temperatures to bottom out in the mid- upper 20s for most of southern New England tomorrow with slightly warmer temperatures (low 30s) along The Cape/Islands and slight colder temperatures north and west of I-90.
Short Term - 6am Friday Morning Through Friday Night
Conditions will be a bit on the mild side tomorrow afternoon in the wake of the warm front that pushed through the region today. Highs will be roughly 5 degrees above normal ranging from the upper 30s out west to the low 40s toward the east. A short-wave trough and associated cold-pool aloft will produce a slight chance for a few instability snow showers across the Berkshires and portions of northern MA during the mid-late afternoon hours.
As a cold front associated with the aforementioned short-wave pushes through the region tomorrow, strong Cold Air Advection aloft will begin the transition to west/northwesterly winds and colder temperatures for southern New England over the weekend. Lows Friday night bottom out in the upper-teens across the interior and low-mid 20s along the coastal areas.
Long Term - Saturday Through Thursday
Big Picture... Five-wave charts continue to show a broad trough over the Northeast USA and a ridge along the Pacific Coast. This continues into the weekend, then reverses to a ridge Northeast and trough West Coast early and mid next week. Shortwave scale shows a flatter flow through Tuesday, although with weak shortwaves moving through. After that... a sharper ridge in the Northeast Wednesday, and a trough ejecting from the Desert SW reaching the Mid-Atlantic Thursday.
Overall, a seasonably cold period. Model mass fields are similar through the weekend, then increasingly diverge through the early and mid week. Two systems of concern, one on Tuesday and the second on Thursday. The GFS carries the Tuesday system south of New England keeping us dry, while the ECMWF (European Centre for Medium-Range Weather Forecasts) and GGEM pass a little closer to the south and bring light snow to the region. The GFS and ECMWF keep the Thursday system well south of New England while the GGEM moves closer and brings us some light snow. Confidence is high through the weekend, diminishing to low by Thursday.
Details... Saturday - Sunday
Shortwave moves across Srn New England Saturday with meager cold pool. Limited moisture, and that will be focussed below 850 mb. Model blends show clear skies while individual models indicate partly cloudy skies during the morning and midday. Northwest winds will bring cold advection, with winds aloft supporting gusts of 30- 35 kt/35-40 mph. Temps aloft in the mixed layer support max surface temps in the 20s inland and low 30s along the coastal plain.
Continued pressure gradient Saturday night will maintain the strong gusty northwest winds. Dew points in the single numbers, and a few spots may have dews below 0. Overall, look for mins from 6 northwest to 20 southeast.
Sunday shows some cirrus moving in, but otherwise a fair day with lingering northwest gusts. Temps aloft support max surface temps in the 20s northwest and low 30s southeast.
Monday through Wednesday... Continued fair and cold Monday with high pressure overhead and temps in the mixed layer supporting max surface temps in the upper 20s and 30s.
Of concern is a weather system that moves down the West Coast late week, then ejects from the Desert SW Sunday. This approaches the Mid Atlantic Coast on Tuesday. As noted above, the GFS keeps the area dry, while the GGEM and ECMWF bring precipitation into Srn New England. The track even on the wet models suggests low pops, if any. Will maintain chance probability of precipitation for light snow mainly along and south of the Mass Pike, but with a slower onset...around 09Z-12Z/4-7 AM.
High pressure builds on Wednesday with clearing skies and seasonably cold temps.
Thursday... Another upper low ejects from the Southwest, approaching the East Coast Thursday. This combines with low pressure along the Gulf Coast. The GFS swings the two systems across the Carolina and Mid- Atlantic coasts, passing south of Srn New England. The ECMWF focuses on the southern system and takes it across the Carolinas and out to sea. This would keep our area dry. Will go with a dry forecast with continued seasonably cold temps.
Winds shift from southwest to northwest by tomorrow afternoon behind a weak cold front. Somewhat rough conditions expected for the outer waters through Saturday as wind gusts will increase to SCY level tomorrow afternoon behind the front. SCY remains in effect for outer waters due to wave heigheights > 5 feet. Conditions may improve for a few hours over night before deteriorating as the aforementioned cold front moves through the weekend.
Outlook /Saturday through Tuesday/... Saturday: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas.
Saturday Night: Moderate risk for gale force winds with gusts up to 40 kt. Areas of rough seas.
Sunday: Moderate risk for gale force winds with gusts up to 35 kt. Areas of rough seas.
Sunday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas.
Monday: Winds less than 25 kt. Seas locally approaching 5 ft.
Monday Night: Winds less than 25 kt. Slight chance of snow showers. Areas of visibility 1 to 3 nm.
Tuesday: Winds less than 25 kt. Chance of snow showers. Visibility 1 to 3 nm.
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.
Small Craft Advisory until 7pm EST this evening for ANZ232>234. Small Craft Advisory until 9pm EST this evening for ANZ235- 237. Small Craft Advisory until 7pm EST Friday for ANZ254>256.