textproduct: Boston / Norton

WHAT HAS CHANGED

No significant forecast changes.

KEY MESSAGES

- Another hot, summerlike day with increasing humidity. Thunderstorms arrive late this afternoon into tonight, a few of which could become strong to severe. Sunday turns cooler with scattered showers, but not a washout.

- Seasonable temperatures Monday, followed by another stretch of summerlike heat and building humidity. No notable storms next week, though a front may bring a period of showers and thunderstorms mid to late week.

DISCUSSION

KEY MESSAGE 1...Another hot, summerlike day with increasing humidity. Thunderstorms arrive late this afternoon into tonight, a few of which could become strong to severe. Sunday turns cooler with scattered showers, but not a washout.

There were no notable changes to the near and short-term forecast. Given a well-mixed boundary layer reaching 850-800 mb, highs should climb well into the upper 80s to lower 90s, remaining well above normal for early June, when average highs are typically in the lower 70s. Dewpoints rise into the upper 50s to lower 60s today, leading to a somewhat muggier feel, though conditions should not feel excessively humid. For those heading to the beaches, there is a moderate risk for rip currents Saturday along east-facing beaches of Cape Cod, ocean-facing beaches of Nantucket and Marthas Vineyard, and south-facing beaches from Point Judith, RI to Westport, MA. Always check with lifeguards regarding local rip current conditions.

Confidence remains consistent that most, if not all, daylight hours remain dry, though a brief afternoon shower cannot be ruled out north and west of the I-495 corridor, likely associated with a prefrontal trough. Increasing heat and humidity will lead to a moderately unstable atmosphere, with CAPE values between 500-1000 J/kg, though some guidance suggests locally higher values approaching 1500 J/kg. This should support convective initiation by late afternoon, roughly 5-6PM. Activity may persist after sunset, supported by frontal forcing, modest mid-level lapse rates near 6.5 C/km, and increasing deep-layer shear, before weakening and shifting offshore by around midnight. DCAPE values are modest as well, approaching 800 J/kg, while 0-6 km bulk shear increases to around 30- 40 kt. Given this setup, a Slight Risk for severe thunderstorms continues for much of interior southern New England, with the primary threats being strong to damaging straight-line winds and locally heavy downpours as PWAT values climb to around 1.8 inches.

Sunday morning, subsidence behind the front allows for drier, albeit humid, conditions with a mix of clouds and sunshine. By afternoon, a more defined mid-level trough and associated shortwave energy move across southern New England, though recent guidance has trended the surface low farther north into the Gulf of Maine. As a result, rainfall appears more showery and less widespread, with the greatest concentration of showers, general thunder, and perhaps small hail mainly across eastern portions of southern New England, though the overall severe threat appears limited. Cooler air arrives more gradually, which may allow highs to still reach the upper 70s to lower 80s before northeast flow develops later in the evening.

KEY MESSAGE 2...Seasonable temperatures Monday, followed by another stretch of summerlike heat and building humidity. No notable storms next week, though a front may bring a period of showers and thunderstorms mid to late week.

Sundays mid-level trough exits east of New England by early Monday morning as an amplified ridge shifts toward the eastern third of the CONUS. The trough eventually evolves into a cutoff mid-level low over the Canadian Maritimes, helping to slow eastward progression of the ridge and supporting another stretch of summerlike temperatures across southern New England. Monday will likely be the coolest day of next week due to north-northeast flow aloft draining a cooler airmass southward into the region. Forecast soundings Monday afternoon depict a well-mixed atmosphere with the boundary layer extending to around 850 mb and temperatures at that level ranging from +8C to +12C. Naturally, the farther east, the cooler temperatures will be, with Cape Cod, the Islands, Boston, and the eastern coastal plain largely remaining in the 70s, while the Connecticut River Valley reaches the lower to middle 80s. Through much of next week, an anomalous ridge extending north toward Hudson Bay in Canada favors mainly dry and increasingly hot conditions. 850 mb temperatures rise to around +15C Tuesday, then increase to around +18C Wednesday through Friday. This should support highs in the middle 80s to near 90 Tuesday, followed by upper 80s to lower 90s through much of the remainder of the week. The first half of next week should feature relatively comfortable dewpoints in the 50s. However, by late week, dewpoints rise into the 60s, leading to a more humid airmass. While outside the forecast period, there is a signal for heat to continue into next weekend, reflected in CPC outlooks depicting a Slight Risk (20 to 40% probability) for extreme heat across portions of the Northeast. In terms of precipitation, there does not appear to be anything appreciable on the horizon through much of next week. However, a frontal passage late in the week may bring a period of showers and thunderstorms as heat and humidity continue to build.

AVIATION /07Z SATURDAY THROUGH WEDNESDAY/

Forecaster Confidence Levels...

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

06Z TAF Update:

Today...High confidence.

VFR, though the risk for isolated to scattered TSRA increases after 20Z from KORH westward. A few storms may become strong, with gusty winds and localized turbulence the primary aviation hazards. Greater storm coverage becomes more likely after 00Z farther east. Winds become SW and increase to around 10-12 kt with gusts of 20-25 kt.

Tonight...Moderate confidence.

VFR outside of scattered thunderstorms, which may briefly reduce flight categories to IFR in heavy rainfall and lower visibility. Initially scattered convection may consolidate into a broken line of storms moving eastward into the ORH/BED/BOS/PVD corridor between 00- 03Z before shifting offshore. A few storms could remain strong early with localized gusty winds, though general weakening trends are favored overnight. Brief clearing develops between 04-08Z from north to south as the front moves offshore. SW winds around 10 kt shift to W/WNW at 5-10 kt.

Sunday...Moderate confidence.

VFR, though SHRA/TS develops as early as 16Z Sunday across the MA/VT/NH border region and progresses south/southeast through the afternoon. Best chances appear from ORH eastward to the Cape and Islands, with lower coverage farther west. Coverage should diminishes roughly after 21Z. Winds become NW around 10-13 kt before turning NE late in the day.

KBOS...High confidence in TAF, though moderate confidence in wind timing.

VFR through 00Z Sunday. ENE winds become SW around 16-17Z. TSRA possible after 23Z.

KBDL...High confidence in TAF.

VFR, with SW winds gusting to 20-25 kt after 17Z. TSRA possible after 22Z.

Outlook /Sunday Night through Wednesday/...

Sunday Night: VFR. Breezy. Slight chance SHRA.

Monday: VFR. Breezy.

Monday Night: VFR.

Tuesday: VFR. Breezy.

Tuesday Night: VFR.

Wednesday: VFR. Breezy. Slight chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Saturday and Sunday...High confidence.

Small Craft Advisories have been expanded for Saturday afternoon through Saturday night across the southern waters, eastern waters, and Cape Cod Bay for a combination of SW wind gusts up to 25 kt and building seas of 4-6 ft.

There is also a risk for thunderstorms capable of frequent lightning, heavy downpours, and localized strong wind gusts, mainly after 7 PM across both the southern and eastern waters.

Another round of scattered showers and thunderstorms develops Sunday afternoon. There could be a period Sunday late afternoon into the evening where portions of the eastern waters experience northerly to northeast wind gusts approaching 25 kt, which may prompt an extension of Small Craft Advisories into Sunday night. For now, advisories remain in effect through Sunday afternoon.

Outlook /Sunday Night through Wednesday/...

Sunday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers.

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

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

Tuesday through Wednesday: Winds less than 25 kt.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...Air Quality Alert from 11 AM this morning to 11 PM EDT this evening for MAZ013-016>024. RI...Air Quality Alert from 11 AM this morning to 11 PM EDT this evening for RIZ001>008. MARINE...Small Craft Advisory from 2 PM this afternoon to 11 PM EDT this evening for ANZ231-250. Small Craft Advisory from 2 PM this afternoon to 8 AM EDT Sunday for ANZ232>235-237. Small Craft Advisory from 2 PM this afternoon to 2 AM EDT Monday for ANZ254>256.