Area Forecast Discussion

WHAT HAS CHANGED

Minor adjustments made to the aviation forecast, with respect to flight categories, otherwise the core forecast is on track.

KEY MESSAGES

- Isolated T-Showers and rain through this afternoon and then clearing tonight. Becoming chilly for Monday morning.

- Cool with shower chances on Patriot's Day. Overnight turning cold with subfreezing conditions across much of SNE.

- Cooler again for Tuesday before a return of seasonable temperatures Wednesday and the rest of the week

DISCUSSION

KEY MESSAGE 1...Isolated T-Showers and rain through this afternoon and then clearing tonight. Becoming chilly for Monday morning.

Ahead of an approaching cold front convective showers developing in eastern MA and RI. While not severe, these showers have a history of lightning and pea sized hail. Luckily, those weak thunder showers are short-lived with a more stratiform light rain associated with the cold front. The system is fairly progressive, anticipating the rain will end from west to east between 5pm and 8pm. As mentioned, cannot rule out a few wet snowflakes mixing in the highest elevation of northern and western MA. Otherwise, a brief period of gusty wind from the W-WNW 20 to 30 mph with the frontal passage. Tonight, clear skies and decreasing winds less than 10 mph. Chilly, lows fall into the lower to mid-30s, with northern Worcester County and the eastern slopes of the Berkshires in the upper 20s.

KEY MESSAGE 2...Cool with shower chances on Patriot's Day. Overnight turning cold with subfreezing conditions across much of SNE.

Patriot's Day is a chilly one, there is no doubt about that. Falling 500mb heights from a mid-level trough brings much colder air into southern New England. 925mb temperatures Monday afternoon are around 0C to -2C, thus afternoon temperatures range between the low-50s and the upper-40s. Looking back at the high temperature since 2020, the forecast high for tomorrow lines up, of the six years, four of those years have had temperatures in the low to mid-50s. For those curious minded people, the highest temperatures on Patriot's Day occurred in 2012 with a high of 87F and coldest high of 38F in 1925 and 1926.

Sensible weather, scattered showers from a weak low pressure passing south of New England's waters. However, would like to reiterate not every town will experience showers due to the scattered nature. Wind is from the W early in the morning, then NW early afternoon at 10-15 mph. There is some uncertainty, but wind could shift to the N by the evening which could drain colder air down from northern New England and any lingering rain showers could become a light snow shower. Have lower confidence in this happening, though it is an outlying, albeit lower chance.

Turning even colder Monday night into Tuesday with morning lows in the low-30s to upper-20s across the entire region. While early last week felt more like summer, it's not uncommon for subfreezing conditions during mid to late April. In fact, per climo, the average last freeze is at/or around May 1st for most of southern New England. This is why Frost or Freeze headlines have not been issued from our office, at this time. That said, if you have already place sensitive plants outside. It would be wise to cover or bring inside.

KEY MESSAGE 3...Cooler Tuesday before a return of seasonable temperatures Wednesday and the rest of the week.

Sharply colder Tuesday morning after a night of effective radiational cooling Monday night. Expecting lows in the lower to mid 20s across the interior and closer to freezing along the coast. A cool but otherwise pleasant day Tuesday. 925mb temps struggle to warm above -5C, so highs will struggle to warm much above 50 degrees for most locations. Some showers are possible Wednesday morning as a weak boundary moves through the region. Expecting mainly rain showers, but a few wet snowflakes are possible across the interior. More seasonal temperatures make a return Wednesday afternoon as the core of the upper trough moves offshore. 925 mb temperatures recover to around 5C, supporting more seasonable highs in the upper 50s/low 60s. NW flow makes a return towards Thursday/Friday in the wake of another front passing through sometime late Wednesday, and high pressure builds back in as ridging approaches, which should keep the region dry. Still seeing some disagreement with the west/east positioning of a cutoff upper level trough over the Canadian Maritimes Thursday and Friday. The placement of this feature will strongly influence weather later this week. A closer position brings much cooler and unsettled weather with a chance for showers Thurs/Friday. Believe the NBM has a fairly good handle and splits the difference with mostly cloudy skies and highs in the lower to mid 60s. Next chance for rain arrives Saturday with an approaching frontal system.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Forecaster Confidence Levels...

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

18z TAF Update:

Through 00z: Moderate Confidence.

Convective showers have developed ahead of the cold front and has produced isolated lightning, opt'd to include TSRA for terminals along this line of showers through 18-19z. Continue to anticipate poor flight categories, IFR-LIFR with pockets of MVFR through 21z. There after, MVFR conditions through 00z. Clearing to VFR shortly after 00z with the departure of RA and the cold front. As for wind, those are increasing as of 18z with gusts 20-30 kts from the W-WNW.

Tonight...High confidence.

VFR. Diminishing wind gusts. W wind 5-10 kts.

Monday...Moderate confidence.

Low-end VFR ceilings (040 to 060) along with sct'd showers. Cannot rule out wet snow flakes mixing in after sunset. WNW to NW wind at 10-15 kts.

Monday Night...High confidence.

VFR. Skies becoming clear, NW wind becomes NNW to N 5-10 kts.

KBOS Terminal... Moderate Confidence in TAF.

Sct'd convective showers could produce an isolated lightning strike near KBOS over the next 90 minutes, ending around 1830z. Gusty W-WNW winds increase as well, gusting 25-30 knots through 00-02z. There after becoming VFR with a W wind around 8-10 kts.

KBDL Terminal... High Confidence in TAF.

Outlook /Monday Night through Friday/...

Tuesday: VFR.

Tuesday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA.

Wednesday: Mainly VFR, with local IFR possible.

Wednesday Night through Friday: VFR.

MARINE

Forecaster Confidence Levels...

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

Tonight through Monday Night: High Confidence.

Strong cold front brings SCA conditions and rain, seas 3-5 feet, and W-NW gust up to 30 knots for all of the waters this evening and ending by early Monday morning. Winds shift NW and ease following this frontal passage late tonight. Winds shift W over the southern waters and more S over the E/NE waters Monday, falling between 10-15 kts, eventually winds shift to the NNW/N by Monday night. Lastly, seas settle to 2-3 ft.

Outlook /Monday Night through Friday/...

Tuesday: Winds less than 25 kt.

Tuesday Night: Winds less than 25 kt. Slight chance of rain showers.

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

Wednesday Night through Friday: Winds less than 25 kt.

BOX WATCHES / WARNINGS / ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ230>234-236-250-251. Small Craft Advisory until 8 PM EDT this evening for ANZ235- 237. Small Craft Advisory until 11 PM EDT this evening for ANZ254>256.