Marine Weather and Tide Forecast for Plymouth, MA

NEAR TERM /UNTIL 6 PM THIS EVENING/

Key Messages...

* A few severe storms possible across western MA/CT after 4-5 pm today but greater areal coverage across northern New England

* Much of today may end up dry with partial clearing and highs well up into the 70s to near 80 with some humidity too

Details...

A complex forecast into this evening...which we will explain below. Low clouds covered much of region at mid-morning...but enough diurnal heating with the strong May sun angle should allow for partial sunshine to develop through the afternoon.
Highs should be well into the 70s to near 80 with modest humidity too.

The main concern revolves around the convective threat today.
The latest guidance is fairly limited with the threat of elevated activity through mid afternoon with better forcing and moisture to our northwest. While a few isolated showers and perhaps an isolated t-storm can not be ruled out...thinking dry weather may prevail across much of the region through mid afternoon.

We do expect a modest amount of instability to develop across the interior with MLCapes rising into the 1500-2000 J/KG range. There also will be a fair amount of effective shear on the order of 35 to 45 knots
At the same time
a relatively strong shortwave will be lifting into northern New England.
Although we expect a fair amount of instability/shear we will be on the edge of the stronger forcing. So that may keep any activity that develops across our region isolated to scattered with better coverage in northern New England
However
given the amount of instability and shear and storm that develops in western MA/northern CT will be capable of becoming severe with the main threats being localized damaging wind gusts and hail.
This also looks to be a rather late show...mainly after 4-5 pm across western MA/CT. This is supported by the CAMs and machine learning guidance tend do have some severe probs into this region...but hint at a better chance to our north.

What ever activity develops should weaken this evening...as it out runs better instability/forcing. So while a rumble or two of thunder may survive onto the I-95 corridor...the severe weather threat appears low in this region.

SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/
Key Messages:

* Drier and much less humid tonight, although still some cloud cover around.

* Partly to mostly cloudy Sunday, breezy with generally seasonable temps. Hit or miss shower possible north of the Mass Pike.
likely Details:

Our weather pattern for tonight into Sunday then becomes more strongly governed by the upper level low over Michigan. This looks to be accompanied by below-average 850 mb temps and still quite a bit of low to midlevel RH. So while we do clear out tonight and trend dry, there could still be at least partly cloudy skies tonight but not the low clouds we've had the last couple nights. The biggest change though is that dewpoints will plummet back into the 40s to low 50s, so a considerably less humid airmass.

Sunday is looking partly to mostly cloudy and rather breezy with WNW winds around 10-15 mph with gusts to 20 mph. Couldn't rule out a hit or miss shower north of the Mass Pike Sunday but probably not widespread or capable of washouts. It's possible that adiabatic downsloping could boost areas such as metrowest Boston to around 70 degrees, but highs could struggle to reach the low to mid 60s in interior Southern New England.

LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
Key Messages:

* Dry and seasonable Monday

* Cooling trend returns Tuesday through the rest of the week

* Another system may bring significant rain and gusty winds to southern New England midweek

Details...

An upper level low makes its exit offshore towards the Maritimes Monday night. Northwest flow kicks in in its place while the cooler temperatures aloft remain, which will help keep the region cooler and drier; highs Tuesday through Thursday will remain mostly in the 50s and low 60s.

Towards the second half of the week, another upper level low is expected to dig into the Great Lakes. An associated surface low is then expected to move up along the east coast towards southern New England. The late spring Nor'Easter would likely bring significant rainfall and gusty winds sometime Wednesday evening through Friday, however, timing still varies greatly in the guidance. Deterministic guidance also still varies significantly on the track of the low's center, and the GEM generally has the system approaching slightly later than the other models do and moves it further to the south of the region. This would keep most of the rain to the south and glance the south coast. Generally, though, the consensus is that the end of next week will be unsettled and cool with continued broad cyclonic flow and cooler temperatures aloft.

AVIATION /13Z SATURDAY THROUGH WEDNESDAY/
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

12Z TAF Update:

Today: Moderate confidence.

An active, complicated aviation forecast period, with continued stratus/fog and then two potential rounds of TS.

IFR-LIFR likely at most airports at onset of this period, and categories unlikely to change significantly thru the AM hrs.
First potential round of SHRA/TSRA looks to move in between 12-17z. This activity would be capable of downpours and lightning, although it is still uncertain on how widespread it may be, which lead to handling this first potential round with PROB30s until its areal coverage becomes more clear.

After ~17z, some improvement in most areas to something closer to a SCT-BKN VFR BDL-BAF-ORH with MVFR/perhaps still lingering IFR eastern airports (best chance IFR Cape and Islands). SCT TSRA, some of which could become strong to severe, then begins to develop or work in from eastern NY between 17-00z, likely as a broken line of storms. Better chc at strong t-storms for BAF and BDL and ORH, and opted to indicate 2-3 SM TSRA in PROB30s where the potential for stg/severe storms would lie. Unlikely storms would survive past BED/PVD but this will need to be monitored today.

Light south winds, which could become ESE near the eastern coast thru mid/late afternoon, then a windshift to SW very late in the day to around 10 kt.

Tonight: High confidence.

Any SHRA/TS threat should dissipate after 01z. Rapid improvement to SCT-interior BKN VFR clouds takes place tonight, along with a windshift to W/NW around 10-14 kt.

Sunday: High confidence.

VFR / VFR-MVFR ceilings interior airports (bases 020-040). Hit or miss SHRA mainly N and W of ORH. W/NW winds 10-15 kt with gusts to 20-25 kt.

KBOS TAF...Moderate confidence. Initial MVFR bases should go to IFR by 08z, then remain in IFR-MVFR range into most of the AM hrs. Possible SHRA/TS between 14-17z (indicated with PROB30s)
but it's unclear how widespread any TS may be. Gradual improvement to MVFR-VFR after 17z. Less of an afternoon TSRA risk but it is not zero and will need to be monitored. S winds 5 kt or less become SE by late morning, then flip to SW 23-00z.

KBDL TAF...Moderate confidence. IFR ceilings to begin. Initial round of SHRA/TS in the 12-15z timeframe, and while its coverage is still uncertain, it would not likely become strong.
Ceilings then lift to BKN VFR after 17z, with second risk for SCT TSRA 17-00z, and its these which could become strong to severe. S winds under 10 kt become briefly SE this aftn then flip to W around 10-12 kt late in the day.

Outlook /Sunday Night through Wednesday/...

Sunday Night: Mainly VFR, with local MVFR possible. Windy with local gusts up to 30 kt.

Monday: VFR. Windy with local gusts up to 30 kt.

Monday Night: VFR. Breezy.

Tuesday: Mainly VFR, with areas MVFR possible. Breezy.

Tuesday Night: Mainly VFR, with local IFR possible.

Wednesday: MVFR/IFR conditions possible. Chance SHRA.

MARINE
Forecaster Confidence Levels:

Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.

High confidence overall.

Winds and seas remain below SCA levels through tonight. However fog is a concern for boaters this morning, and there could be thunderstorms over the southern waters late this morning to early afternoon.

West to northwest winds increase tonight and especially on Sunday to around 20-25 kt, with seas increasing to 3 to 5 ft.
Small craft advisories have been hoisted for Sunday and into Sunday night for the southern waters. Conditions look borderline on the eastern waters for SCAs but could be considered in later updates.

Outlook /Sunday Night through Wednesday/...

Sunday Night through Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.

Monday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers.

Tuesday through Tuesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft.

Wednesday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 AM Sunday to 8 AM EDT Monday for ANZ232>235-237-254>256.