Marine Weather and Tide Forecast for Woods Hole, MA

KEY MESSAGES

- Rain showers/embedded thunderstorms end early this morning, then passage of a sharp cold front allows for breezy northwest winds and falling temperatures today.

- Light rains change to a mix of rain/sleet and then to wet snow this afternoon into early tonight. Reduced visibilities likely during the PM commute. Minor accumulation (up to 2", locally more possible) but pavement should be mostly wet.

- Scattered rain and elevation snow showers late Fri and Fri night, then drying out and becoming windy Sat.

- Widespread showers with locally heavy rainfall possible Sunday night into Monday night which may lead to minor river flooding. Strong winds possible late Monday and Monday evening.

- Dry and trending colder Tue into Wed.

DISCUSSION
Key Message 1...Rain showers/embedded thunderstorms end early this morning, then passage of a sharp cold front allows for breezy northwest winds and falling temperatures today.

Looking like we'll be experiencing two seasons today.

A strong cold front is working its way through central NY. Ahead of it is a moist and anomalously mild warm sector with temps in the 50s to near 60 and dew pts in the upper 40s to mid 50s in most of Southern New England. Areas of showers and even a few garden-variety thunderstorms are around early this morning due to elevated instability (MUCAPE values as high as 1000 J/kg per SPC's mesoanalysis). The shower and embedded thunderstorm activity should come to an end by the pre-dawn hours but could make for some difficult travel for morning commuters.

The cold front will then surge through Southern New England during the morning hours. Mainly light (if any) showers take place and some areas could end up dry for short intervals will accompany the front's passage. But this is a cold front that has quite a punch of shallow cold advection - temperatures then stand to fall beginning this morning and through the day, and will also be accompanied by northwesterly wind gusts 25-40 mph. More shallow mixing really will cap how strong the gusts will get. Gusts could punch as high as near- Advisory level for a couple hours in the Berkshires early this morning immediately after frontal passage.
But either way, expect a cloudy, breezy and raw day once the winds turn northwesterly, with highs occurring before the frontal passage and then steadily dropping into the 30s through the day.

This then leads in to what takes place this afternoon...

Key Message 2...Light rains change to a mix of rain/sleet and then to wet snow this afternoon into early tonight. Reduced visibilities likely during the PM commute. Minor accumulation (up to 2", locally more possible) but pavement should be mostly wet.

Although the cold front will have moved offshore by around noontime, a southern-stream trough over the lower MS Valley will help to draw another round of precipitation northeastward from the mid- Atlantic into the Northeast in an ana-frontal configuration, falling into the increasingly colder air. This should facilitate rain to change to wintry precipitation as soon as early afternoon before moving offshore early tonight. Precip falls as rain initially, but the strength of the shallow cold airmass suggests that as we move through the afternoon...rain ends up mixing with sleet/ice pellets as model soundings show temperatures aloft not cooling off as fast as the lowest 100 mb to surface do, but then eventually ending as a few-hour period of snow (or snow mixed with rain near the eastern coast).

There are a few moving parts here which cast some degree of uncertainty on how this scenario ultimately unfolds. One is when the precip begins to advance northeastward into the colder airmass; it doesn't look to be much QPF but when it begins will dictate how long changeovers occur, which of course also affects how much of what type of precip falls. Finally, it's important to recognize that early- March wintry accumulations on pavement tend to be governed by time of day and if rates become intense, and that's especially true as just two days ago, many areas saw temperatures in the 70s. Confidence in specific accumulations is not especially high and could be subject to adjustments given the above uncertainties and moving parts to the forecast, either up or down. We opted for coatings to an inch for most, but as much as 2 inches of snow/sleet in interior Southern New England. Pavement should be mostly wet vs wintry though. But with that said, I'd plan on the afternoon commute to be a pretty sloppy one due to wet roads and reduced visibilities...with precip ending by early tonight.

Even though low temperatures drop to around 25-30 degrees tonight, the risk for black ice looks minimized by strong drying/evaporation.

KEY MESSAGE 3...Scattered rain and elevation snow showers late Fri and Fri night, then drying ou totalt and becoming windy Sat.

Quick moving northern stream shortwave and clipper low pass to the north Fri night. Bulk of precip with this system will be focused across northern New Eng, but decent warm advection enhanced by a low level jet will support scattered rain or elevation snow showers late Fri and Fri night. Any snow accum will likely be focused across the Berkshires and Worcester Hills where up to an inch is possible. The low level jet will bring some gusty pre-frontal S-SW winds to the south coast Fri evening, then the low pres will push a cold front through SNE overnight with potential for strong post-frontal wind gusts Sat in the cold advection pattern. Forecast soundings show a well mixed boundary layer supportive of gusts to 35-45 mph with a few 50 mph gusts possible. Wind advisories may eventually be needed.

KEY MESSAGE 4...Widespread showers with locally heavy rainfall possible Sunday night into Monday night which may lead to minor river flooding. Strong winds possible late Monday and Monday evening.

High amplitude trough approaches from the Gt Lakes Mon before lifting across New Eng Tue. Strengthening low level jet ahead of the trough will bring anomalous moisture northward into SNE. PWAT and wind anomalies are favorable for a heavy rainfall event, which is likely to come in 2 waves. First late Sun night into Mon AM with the initial low level jet, then another period late Mon and Mon night with the main LLJ ahead of the cold front. Strong forcing for ascent along with elevated instability will support some heavy convective showers along with a few t-storms. Ensemble guidance suggests potential for 1-2 inches rainfall given high probs (70-90%) of greater than 1" rainfall focused across CT/RI and SE MA. 90th percentile of the ensemble distribution is showing 2-3 inches which would represent a localized worst case scenario. MMEFS ensemble guidance from the NAEFS continues to show moderate probs (50-70%)
for river levels reaching minor flood along the Pawtuxet, Pawcatuck and Wood Rivers in RI, and there are even some low probs for moderate flooding. Along the lower reaches of CT river from Hartford to Middle Haddam there are lower probs (35-45%) of reaching minor flood.

Strong wind across SE New Eng is the other concern with this event, especially late Mon and Mon night ahead of the cold front as LLJ lifts across the region. Details at this time range are uncertain as the strong wind will depend on the extent of mixing which is always a challenge with these southerly LLJ events. It will be mild Mon into Mon evening ahead of the cold front with temps possibly

KEY MESSAGE 5...Dry and trending colder Tue into Wed.

Cold front is forecast to be east of New Eng by 12z Tue with much drier air moving in from the west. Mainly dry conditions expected Tue but blustery and cooler weather in the cold advection pattern.
Coldest day will be Wed as the upper trough and core of the coldest air aloft settles over New Eng with expected temps several degrees below normal.

AVIATION /06Z THURSDAY THROUGH MONDAY/
Forecaster Confidence Levels...

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

06z TAF Update:

Today: Moderate confidence.

A pretty active, changeable aviation forecast period.

Mix of flight categories from VFR to LIFR, lowest along the south coast due to dense fog. Still have areas of showers/TS but this activity should be moving northeast through 08-10z.
Brief clearing from west to east between 08-12z with categories in the VFR-MVFR range for most airports by morning. Southerly winds around 10-15 kt with gusts 20-25 kt with continued low level wind shear.

A cold front will then be moving through SNE between 12-16z Thurs west to east, which will bring a gusty windshift to WNW around 15-18 kt with gusts 25-30 kt. Cooling temperatures will allow for initial rain, but rain should then mix with PL and then SN with MVFR visby/MVFR-IFR ceilings from ~18-00z. Up to an inch of snow accum possible on grassy surfaces although runways should be wet given preceding spell of warm temperatures.

Tonight: High confidence.

Rapid improvement to VFR early tonight. NW winds around 10 kt with occasional gusts to 20 kt. Even though temperatures will be subfreezing, rapid drying should limit any freeze-up on runways.

Friday: High confidence.

VFR, though with increasing midlevel clouds late in the day. NW winds become light and then shift to SW around 5-10 kt.

KBOS Terminal...Moderate confidence. SHRA thru 09z Thurs with period of brief dry weather but MVFR/VFR ceilings around. A gusty windshift to NW takes place 13-15z. Cooling temps after 18z then brings a risk for rain mixed with PL then brief SN.
Visbys 2-4 SM in wintry precip, although runways should be wet.
Rapid VFR improvement by early this evening.

KBDL Terminal...Moderate confidence. SHRA, embedded TS possible thru 08z. VFR/MVFR ceilings after 08z before cold front brings resuming risk for rain and a gusty NW windshift after 13z.
Cooling temps could support mixover to PL then SN after 17z Thurs, ending by 00z.

Outlook /Friday through Monday/...

Friday: VFR. Breezy.

Friday Night: Mainly VFR, with local MVFR possible. Breezy.
Slight chance RA.

Saturday: VFR. Strong winds with local gusts up to 40 kt.

Saturday Night: VFR. Windy with local gusts up to 30 kt.

Sunday: VFR. Breezy. Slight chance RA, slight chance FZRA.

Sunday Night: Mainly VFR, with local IFR possible. Windy with gusts up to 35 kt. Chance RA, slight chance FZRA.

Monday: Mainly MVFR, with areas IFR possible. Strong winds with local gusts up to 40 kt. RA.

MARINE
Forecaster Confidence Levels...

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

Rough seas linger across the outer coastal waters into Friday morning. A cold front moving across the waters Thursday will also generate gusty SW winds at times until it passes. Becoming clearer with gusty W to NW winds Thursday into Thursday night.

Outlook /Friday through Monday/...

Friday: Winds less than 25 kt. Seas up to 5 ft.

Friday Night: Strong winds with local gusts up to 30 kt. Areas of rough seas. Slight chance of rain.

Saturday: Moderate risk for gale force winds with gusts up to 35 kt. Rough seas up to 12 ft.

Saturday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas.

Sunday: Winds less than 25 kt.

Sunday Night: Strong winds with gusts up to 35 kt. Areas of rough seas. Chance of rain.

Monday: gale force winds with gusts up to 40 kt. Rough seas up to 17 ft. Rain.

BOX WATCHES/WARNINGS/ADVISORIES
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 PM EDT this evening for ANZ232- 233.
Small Craft Advisory until 1 PM EDT this afternoon for ANZ234.
Small Craft Advisory until 7 AM EDT Friday for ANZ235-237-250- 254>256.