textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes. Becoming more confident that any minor river flooding will not occur until Monday.

KEY MESSAGES

- Record warmth gives way to cooler weather by end of the week with rain/snow showers possible late Friday or Friday night.

- Potential for strong winds and heavy rain later Sunday and Monday which may lead to minor river flooding.

DISCUSSION

KEY MESSAGE 1...Record warmth gives way to cooler weather by end of the week with rain/snow showers possible late Friday or Friday night.

All good things must come to an end and that includes our taste of unseasonably warm weather, although temperatures should still average above normal Wednesday and Thursday. We're watching a backdoor cold front that will drop south through New England early Wednesday and exactly where it ends up will be the difference between cooler, damp weather and cloudy but somewhat milder conditions.

Latest high-res guidance brings front through central/eastern MA and northern RI where temperatures should drop into upper 30s and lower 40s along with drizzle and patchy fog from onshore flow, while to the south across much of CT, it should be cloudy but somewhat milder with temperatures in the 40s to around 50.

This front should advance back northward late in day Wednesday and Wednesday night, so in the cool sector temperatures should rise during night. Upper trough moving through eastern Great Lakes will bring a stronger cold front through region early Thursday morning, bringing with it a few showers and the arrival of colder air in its wake. A weak and fast moving low is expected to cross New England later Friday into early Saturday, accompanied by rain or snow showers, with any snow more favored in western/central MA, but with minimal accumulation.

KEY MESSAGE 2...Potential for strong winds and heavy rain later Sunday and Monday which may lead to minor river flooding.

Even though melting snow has brought increased river and stream flows, we don't see much of a flood concern until Monday with the arrival of potentially heavy rainfall and strong winds. Rises on mainstem Connecticut River this weekend should remain below flood stage.

Ensemble situational awareness tables indicate the potential for a highly anomalous event in terms of rainfall and strong winds, with several wind and moisture parameters above the 90th percentile and in some cases near the max of model climate. This is ahead of a more amplified upper trough which will bring strong southerly flow and deep moisture into southern New England resulting in a widespread and potentially heavy rainfall event along with a brief surge of warmth.

Probabilities for 1"+ of rain are currently centered more across CT, RI, and SE MA, and as a result ensemble river forecasts show the potential for minor flooding beginning Monday along the Pawtuxet, Pawcatuck, and Wood Rivers in RI and perhaps along the lower reaches of the mainstem Connecticut River from Hartford through Middle Haddam.

It's tough to mix down strong winds this time of year with southerly flow events, but areas that are usually favored are the immediate South Coast, Cape Cod, and the Islands. Assuming we have a strong inversion, which is typical in March, we can estimate gusts taking about 50% of 925 mb winds. GFS shows a peak of 70-75kt Mon morning which would yield 35-40kt gusts and Gales on the coastal waters.

Behind a strong cold front, we look to be in for another brief surge of cold with below average temperatures in the 30s Tuesday.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

00z TAF Update:

Tonight: High confidence.

LIFR-VLIFR fog continues for the Cape and Islands, and should generally continue while expanding slightly northward to PVD after 07z. Elsewhere VFR prevails through at least 08z, then a backdoor cold front beings a NE wind shift, IFR stratus and drizzle/mist to BOS/BED and perhaps as far south as ORH by 09-12z.

Wednesday: Moderate confidence.

IFR with NE winds, drizzle and mist for BOS-BED-ORH; LIFR fog/stratus Cape and Islands and generally BKN VFR for BDL. As backdoor front returns northward as a warm front, expect modest improvement to MVFR-IFR in most areas, timing approx 16-20z with winds becoming SE/S.

Wednesday Night: Moderate confidence.

MVFR/IFR ceilings ahead of approaching cold front. Isolated showers/possible thunder rumbles south of the Mass Pike before cold front comes in approx 03-07z and moves into central MA/CT by 12z. SW winds around 10-12 kt with low level wind shear likely.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Thursday through Sunday/...

Thursday: Mainly VFR, with local MVFR possible. Windy with areas of gusts up to 30 kt. Chance RA, chance SN.

Thursday Night through Friday: VFR. Breezy.

Friday Night: Mainly VFR, with local MVFR possible. Windy with local gusts up to 30 kt. Chance RA, chance SN.

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

Saturday Night: VFR. Breezy.

Sunday: Breezy. Slight chance RA, slight chance SN.

MARINE

Forecaster Confidence Levels...

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

High confidence through the weekend.

Main concern through Wed is dense fog during the nighttime and morning hours, especially on south coastal waters. Also need to be aware of the backdoor front dropping south Wed morning which will bring an abrupt wind shift to NE on E MA waters, if not into Narragansett Bay, with brief 20-25kt gusts possible.

Looking at a fairly active pattern starting Wed night with SCA winds and seas probable into Friday and then again over weekend. As mentioned in the discussion above, we're getting more confident in southerly Gales Monday with possible gusts up to 40kt.

Outlook /Thursday through Sunday/...

Thursday: Moderate risk for Small Craft Advisory winds with local gusts up to 30 kt. Areas of rough seas. Chance of rain.

Thursday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas.

Friday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft.

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

Saturday: Strong winds with gusts up to 30 kt. Areas of rough seas.

Saturday Night: Winds less than 25 kt. Seas locally approaching 5 ft.

Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...None.