textproduct: Boston / Norton

WHAT HAS CHANGED

No changes with the latest forecast update.

KEY MESSAGES

- Breezy, warm, and dry day with elevated fire weather potential this afternoon.

- Warmer on Tuesday with a chance for showers and thunderstorms across far northwestern Massachusetts.

- Unsettled for the midweek timeframe with multiple chances for showers and embedded thunderstorms.

- Turning sharply cooler late in the week and into the weekend.

DISCUSSION

KEY MESSAGE 1... Breezy, warm, and dry day with elevated fire weather potential this afternoon.

Cold start this morning for many of us as a few additional hours of radiational cooling took place with less cloud cover than high-res guidance initially advertised. Coldest spots this morning are interior valleys with lows in the lower 30s. Quick warm up this morning as 850mb temps soar from 0C to +6C by this afternoon. Given the expected well mixed boundary layer up to 800mb with full sun, expecting high temperatures in the upper 60s to low 70s in the CT and Merrimack River Valleys. Coolest temps will be found along the immediate south coast will be coolest in the low to mid 60s. Good mixing also leads to a gusty day; with a 25-35kt 850mb jet overhead, expecting to mix down gusts of 25 to 35 mph. This, combined with the drier air (RH values down to 25-30 percent) has led us to issue a Special Weather Statement for elevated fire weather potential covering all of southern New England with the exception of Cape Cod and the islands.

KEY MESSAGE 2... Warmer on Tuesday with a chance for showers and thunderstorms across far northwestern Massachusetts.

Cold front slowly advances toward our CWA through the day on Tuesday. At the same time, high pressure continues to build over the Atlantic. The result will be a gusty SW winds and even warmer temperatures away from the marine modified airmass towards the south coast. 925T on the order of +17C/+18C should allow highs to reach near 80 in the lower elevations northwest of I-95. The gusty southwest winds will hold highs in the 60s near the south coast, Cape and Islands. It is possible that Nantucket does not even break 60 degrees! Bufkit soundings support southwest wind gusts of 25 to 35 mph with a few gusts of 40-45 mph possible towards the upper Cape.

Mainly dry weather prevails Tue as most of the synoptic scale forcing will remain well to our west in the vicinity of the cold front. Still see at least a low risk for a thunderstorm or two across western Massachusetts with CAPE values increasing to around 1000 J/kg Tuesday afternoon.

KEY MESSAGE 3...Unsettled for the midweek timeframe with multiple chances for showers and embedded thunderstorms.

A slow moving cold front approaches the region from the west on Wed. Still some timing differences...But we do expect a band of showers to overspread the region from west to east as the day wears along. This may take until mid-late afternoon to reach the I-95 corridor...but again the timing still needs to be worked out. There might be an embedded t-storm or two as well...But instability does not look to be high enough for any severe weather.

This cold front slowly sags south of our region Wed night into Thu bringing cooler temps. In terms of the potential for a secondary area of low pressure, the trend amongst guidance has been for a solution further to the south of the CWA and thus more of a glancing blow. The exact track of this low will have a significant impact on temperatures during the day Thu depending on if we see rain or end up mainly dry.

KEY MESSAGE 4...Turning sharply cooler late in the week and into the weekend.

The long range ensembles are in good agreement in an upper trough with below normal height fields re-establishing itself Fri into the weekend. Modest westerly flow this time of year coupled with the strong May sun angle should keep high temps near or just slightly below normal though. Highs should still mainly be in the 60s. The night/s will be potentially cool though with lows in the 40s and potentially some 30s along with a frost risk if we have enough clearing.

As for precipitation chances...some shortwave energy with the associated upper trough/cold pool aloft may bring the potential for a few showers at times. However...not expecting a washout with plenty of dry weather expected as well over this time.

AVIATION /06Z MONDAY THROUGH FRIDAY/

Forecaster Confidence Levels...

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

12z TAF Update...No changes.

VFR conditions continue through Tue. SW winds increase later this morning and especially in the afternoon with gusts on the order of 25 to 35 knots with perhaps a few gusts near 40 knots towards the typically prone locations near KFMH. The gusts gradually diminish this evening...but still expect sustained S-SW winds of 5 to 15 knots overnight with a few gusts up to 20 knots persisting. Areas of LLWS this evening and overnight associated with a modest LLJ. SW gusts to 25-35 kt redevelop Tue.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday Night through Friday/...

Tuesday Night: VFR. Breezy. Slight chance SHRA.

Wednesday through Wednesday Night: Mainly VFR, with local IFR possible. Breezy. Chance SHRA.

Thursday: VFR. Chance SHRA.

Thursday Night: Mainly VFR, with local IFR possible. Breezy. Chance SHRA.

Friday: VFR. Breezy. Slight chance SHRA.

MARINE

Forecaster Confidence Levels...

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

High confidence.

7 AM update...

We upgraded to a Gale Warning for the nearshore waters adjacent to Cape cod for a period of 35+ kt wind gusts this afternoon as a modest low level jet develops.

Through Tuesday...

Southwest winds today gusting 25-30 kts. Will also see seas build to 4-6 feet across the outer waters . Given these conditions, the Small Craft Advisory has been extended into Tuesday for the outer waters and expanded into the inner waters this afternoon. There is also a chance for near-gale force winds across Buzzard's Bay as well as Nantucket Sound this afternoon. Additional SCAs will likely be needed Tuesday.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Moderate risk for Small Craft Advisory winds with local gusts up to 30 kt. Rough seas up to 9 ft.

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

Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Chance of rain showers, slight chance of thunderstorms.

Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers.

Thursday Night: Winds less than 25 kt. Areas of rough seas. Chance of rain showers.

Friday: Winds less than 25 kt. Local rough seas. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ230- 235>237-251. Gale Warning from noon today to 7 PM EDT this evening for ANZ231>234. Small Craft Advisory until 8 AM EDT Tuesday for ANZ250-254>256.