Boston, MA 02116 Weather

What has changed

Gusty northwest winds and the recent spell of dry weather could elevate the risk for fire weather concerns for Friday. Otherwise, no significant changes.

Key messages

- Dry cold front moves in tonight to early Friday morning, with breezy, cooler and dry weather for Friday.

- High pressure maintains quiet weather, potentially through late next week with warmer than average highs in the 60s by Monday.

Discussion

KEY MESSAGE 1: Dry cold front moves in tonight to early Friday morning, with breezy, cooler and dry weather for Friday.

High pressure still remains in control of our weather, supplying continued sunny and dry weather. Temperatures have warmed back up into the 60s with a few spot 70s popping up, aided by SWly breezes. However a dry cold frontal boundary is analyzed from central Quebec through MI as of early Thursday afternoon, and this feature will be crossing through Southern New England overnight into early Friday morning. This frontal feature has limited moisture to work with and is moving into an airmass that hasn't seen a drop of rain in quite a while. Really could only see some enhanced cloud cover overnight tonight from it, with at worst some sprinkles. Although the past couple nights have been pretty chilly, SW winds around 10 mph for most of the overnight will keep temperatures quite a bit milder than they've been - in the mid 40s to mid 50s.

Cold front should be moving offshore early Friday morning, but with it brings strong cold/dry advection and breezy conditions through much of Friday. With the protracted spell of dry weather and NWly wind gusts to around 25 to 30 mph picking up in the late morning hours, it could elevate the risk for fire weather given some leaf- drop but the bigger question is that RHs don't look critically low at around 40 percent. We'll be coordinating with our state forestry and fire weather partners on the state of the fuels but fire weather headlines/SPS could be forthcoming for Friday pending that input. 925 mb temps tumble to around +2 to +4C by sundown Friday, then falling further into the 0 to -4C range by 12z Saturday. Downsloping should still support highs into the upper 50s to mid 60s (some upper 60s SE MA). Although typically gusty conditions ease by sundown, a sustained pretty tight pressure gradient continues into Friday evening, which casts some uncertainty on low temperatures. We opted to keep temps from the mid 30s to the low/mid 40s, highest towards the RI/eastern MA coasts where winds will take longer to slacken off, and coolest readings inland.

KEY MESSAGE 2: High pressure maintains quiet weather, potentially through late next week with warmer than average highs in the 60s by Monday.

A series of high pressures will dominate the weather pattern over southern New England this weekend clear through much of next week. The post frontal airmass kicks off the weekend much cooler as 925 mb temps drop from 12-15C Friday to 0-3C Saturday. Under dry NW flow beneath a high building in from New York we'll see high temperatures climb just into the mid to upper 50s on Halloween with evening temps in the 40s. Fortunately, by then the pressure gradient should have lessened enough that winds will be light. Similar forecast for Sunday but with highs a few degrees warmer, touching the low 60s in the warmest spots like the CT and Merrimack valleys.

A mid-level trough looks to pass well to our northeast around Tuesday but lack of moisture and the transient nature of the feature will likely keep rain away before another high pressure takes hold Wednesday into Thursday keeping dry and warmer than average weather in place until the pattern may break down moving into next weekend.

Aviation

Forecaster Confidence Levels:

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

18z TAF Update:

Through Tonight: High confidence.

VFR, though we will see some SCT-BKN VFR cloud decks after 06z Friday as a dry cold front approaches Southern New England. This cold front will still be moving through Southern New England airspace by 12z Friday. SW winds around 10-13 kt with gusts 22-27 kt through sundown, then easing to around 8-12 kt into the evening/overnight, with a windshift to W at BDL and ORH by 09-12z Friday.

Friday and Friday Night: High confidence overall, though it is uncertain if gusty NW winds ease into the evening.

VFR. Gusty windshift to NW 14-18 kt with gusts 25-30 kt during at least the daytime hours; it is more uncertain how long winds stay up for and it is possible they may continue to be breezy into a good part of the overnight.

KBOS Terminal: High confidence in TAF.

KBDL Terminal: High confidence in TAF.

Outlook /Friday Night through Tuesday/:

Saturday: VFR. Breezy.

Saturday Night through Sunday Night: VFR.

Monday: VFR. Breezy.

Monday Night through Tuesday: VFR.

Marine

Forecaster Confidence Levels:

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

Through Friday Night: High confidence.

SCAs were issued through 03z Friday in the nearshore waters around Cape Cod where SW winds have been gusting to around 25-28 kt. SW winds should turn less gusty tonight, as a cold front begins to approach the waters. Waves 2-3 ft.

This cold front then brings a gusty windshift to NW around 25-30 kt on Friday, and possibly linger into Friday afternoon. Will let the existing SCA expire and then will need to issue SCAs for at least Friday afternoon, but possibly linger into Friday night for the eastern waters. Seas around 2-3 ft, but build to around 3-5 ft through Friday afternoon and night, highest offshore/ocean waters.

Outlook /Friday Night through Tuesday/:

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

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

Sunday through Monday Night: Winds less than 25 kt.

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

Watches, warnings and advisories

CT: None. MA: None. RI: None. MARINE: Small Craft Advisory until 11 PM EDT this evening for ANZ231>235.