Marine Weather and Tide Forecast for Harwich Port, MA

KEY MESSAGES

- A frontal system moving in later this afternoon into tonight will bring breezy southwest winds today and a period of steady rain tonight into the overnight, clearing by early Saturday morning. Rainfall amounts are not expected to be significant.

- Drying out Saturday, but with breezy northwest winds and cooler temperatures.

- Breezy and unsettled Sunday through early next week. Steadier rain develops Sunday night with snow potentially mixing in at higher elevations by early Monday. After a brief dry period Tuesday, pattern trends unsettled mid-week.

DISCUSSION
Key Message 1...A frontal system moving in later this afternoon into tonight will bring breezy southwest winds today and a period of steady rain tonight into the overnight, clearing by early Saturday morning. Rainfall amounts are not expected to be significant.

Overcast which developed yesterday and had continued into the evening should give way to decreasing clouds and at least some sunshine early in the day. Will have some sun at least into the morning hours, but expect a canopy of at least midlevel cloud cover to increase across Southern New England during the afternoon. This is in advance of a frontal system that will be working its way into northern New England this afternoon, and begin to slowly trudge southeast into Southern New England late this afternoon and into the tonight/overnight hours.

The primary effects this frontal system will bring to our area is increasingly breezy to gusty southwest winds this afternoon ahead of the system's cold front, to go along with a period of steady rain primarily during the late afternoon to tonight/overnight. Other than a modest increase in the strength of the 925-850 mb jets this system will be working with (to around 45-55 kt), there really wasn't too much difference in the 00z guidance compared to previous forecasts regarding either the rain potential and the winds. Southwest winds by this afternoon should be on the increase, into the 10-15 mph range, and gusts in the 25 to 35 mph range, with the higher end of that range still over southeastern MA, eastern RI and the Cape Cod and the Islands. The Cape and Islands normally gust pretty well with southwest winds; a limiting factor to the gust speeds is the adjacent cooler waters which could reduce mixing to an extent. Highs should reach into the low to mid 50s in most areas, though upper 40s over the south coast, Cape and Islands due to persistent SW flow over the waters.

The cold front begins to move southeastward late this afternoon and with it, it will act on PWATs to around 0.75" per SREF guidance.
Expect a round of steady light rains to break out along the cold front tonight, a depiction shown well across the various higher resolution output. Thinking by midnight, most areas in interior Southern New England should trend dry. The front may be slower to clear into the eastern waters which could lead to continued light rains into the late-overnight to pre-dawn Saturday morning period, but we should be trending drier in all areas by sunrise on Saturday morning. Absent higher precipitable water values, forecast rainfall ranges from around a quarter to a third of an inch, perhaps slightly more over South Shore, Cape Cod and the Islands.

Key Message 2...Drying out Saturday, but with breezy northwest winds and cooler temperatures.

After the cold front moves offshore, pretty robust pressure rises take place to go along with increasing sun and strong cold advection. Saturday ends up being a sunny day, but BUFKIT profiles show good mixing potential which will support northwesterly wind gusts into the late-morning to sundown period. Northwest gusts could reach as high as 30 mph. Even though temperatures end up being a touch cooler than today, full sun should help to offset that. Highs on Saturday in the 40s to low 50s, which are around seasonable, but the northwesterly winds will make it feel a little cooler.

Key Message 3...Breezy and unsettled Sunday through early next week. Steadier rain develops Sunday night with snow potentially mixing in at higher elevations by early Monday. After a brief dry period Tuesday, pattern trends unsettled mid-week.

Generally unsettled day expected on Sunday with a plume of above normal moisture advecting in from the south out ahead of an incoming shortwave trough. Some guidance hints at some isolated showers Sunday before the more substantial wave of showers that arrive Sunday evening with the stronger synoptic support. If there are some AM showers around, snow may mix in at the higher elevations, mainly in northern MA. As mentioned, the more widespread showers arrive later Sunday. Milder temperatures supported by the WAA during the day Sunday will start things as rain. A colder airmass pushes into southerne New England on the backside of this system on Monday. If the cold air moves in early enough when there is still sufficient moisture/precipitation ongoing, we may see a window for snow to mix in or switch over to a wet light snow overnight/early Mon AM. This appears to be more likely for areas north of Route 2 (MA) and also the Berkshires and Worcester Hills. The main wave of precipitation pushes out Monday AM. Guidance hints at the potential for some lingering rain/snow showers Monday, but there is lacking agreement on the timing/coverage of showers. This is looking minor impact with regards to any snow accumulation. Ensemble probabilities are 20-40% for 1" or greater north of Route 2 in MA. Little to no accumulation elsewhere.

Drier air moves in later Monday into Tuesday as high pressure builds in. This will bring a brief period of dry weather Tuesday before it shifts offshore by mid-week. Confidence decreases in the details of the pattern around and after mid-week. Ensemble guidance shows potential for a disturbance or two moving through the flow mid to late week bringing chances for precipitation; however, there is uncertainty in the exact timing and available moisture. Slightly below normal temperatures expected early next week moderating toward late-week.

AVIATION /06Z FRIDAY THROUGH TUESDAY/
Forecaster Confidence Levels...

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

06z TAF Update:

Through 12z Friday: High confidence.

SCT-OVC VFR ceilings, tending to decrease into the early morning hours. SW winds under 10 kt

Friday: High confidence.

VFR; ceilings trend toward an OVC midlevel deck with some lower-end VFR underneath by 20-23z. Winds start off SW under 10 kt, then back to S (SE for BOS) around 10 kt by ~15-17z, then shift to SSW/SW around 21-23z and increasing to 10-15 kt with gusts 20-25 kt, and around 15-18 kt with gusts 25-30 kt for the Cape airports. Left LLWS mention in the TAF for the late afternoon period but surface gusts could be enough to mitigate the risk; if gusts are slow to develop, then LLWS risk increases. Finally, included VCSH mention in most airports during the 20-23z timeframe, but steadier rain not likely to arrive any sooner than 23z in NW MA.

Friday Night: Moderate confidence.

Ceilings deteriorate to MVFR-IFR with 5-6SM RA around 23-03z NW to SE. SW gusts easing some as rain moves in. Cold front should clear a BED- ORH- BDL line by ~05z with improving ceilings and drier conditions on WSW winds; the front could be slower to clear into the waters leading to a longer duration of MVFR-IFR ceilings and rain elsewhere.

KBOS Terminal...High confidence in TAF. OVC VFR ceilings tonight with SW winds. Possible period of SE winds ~15-17z Fri before turning SW 15kt, gusts 25 kt. Ceilings lower to MVFR-IFR in 5 SM rain after 00z Sat.

KBDL Terminal...High confidence in TAF. VFR ceilings today. Rain arrives around 23-00z Sat bringing MVFR/IFR ceilings.

Outlook /Saturday through Tuesday/...

Saturday: VFR. Breezy.

Saturday Night: VFR.

Sunday: Mainly VFR, with areas MVFR possible. Breezy. Chance RA, chance SN.

Sunday Night: Mainly MVFR, with areas IFR possible. Breezy. RA likely, chance SN.

Monday: Mainly VFR, with local IFR possible. Breezy. Chance RA, chance SN.

Monday Night through Tuesday: VFR.

MARINE
Forecaster Confidence Levels...

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

Small craft advisories are in effect for all waters for this afternoon into tonight, as southwesterly winds will be on the increase ahead of a cold frontal passage. SW winds should gust commonly into the 25 to 30 kt range. Gusts in nearshore waters adjacent to Cape Cod and the Islands could occasionally reach into near-gale-force range. Seas will be building to around 4-8 ft through tonight, highest over the outer waters. Expect a period of rain as the cold front moves in tonight on the waters, and rain could continue into early Saturday morning near the Cape and Islands.

Although SCAs continue on the outer waters into Saturday mainly to allow for residual 5+ ft seas to subside, a period of northwest breezes Saturday could warrant possible extension of the SCAs on most waters. Expect northwesterly gusts in the 20 to near 25 kt range for Saturday.

Outlook /Saturday through Tuesday/...

Saturday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft.

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

Sunday: Winds less than 25 kt. Chance of rain.

Sunday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Rain likely.

Monday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Chance of rain.

Monday Night: Winds less than 25 kt. Rough seas up to 8 ft.

Tuesday: Winds less than 25 kt. Local rough seas.

BOX WATCHES/WARNINGS/ADVISORIES
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 2 PM this afternoon to 2 AM EDT Saturday for ANZ230-236.
Small Craft Advisory from 2 PM this afternoon to 5 AM EDT Saturday for ANZ231>235-237-251.
Small Craft Advisory from 2 PM this afternoon to 8 PM EDT Saturday for ANZ250-254>256.