textproduct: Boston / Norton

WHAT HAS CHANGED

Winter Weather Advisory has ended early as temperatures have risen above freezing, ending the freezing rain threat. A potent shortwave passage this afternoon could lead to a snow squall or two, then west winds become breezy to strong overnight. A Wind Advisory has been issued for the Berkshires for gusts up to 50 mph.

KEY MESSAGES

- Freezing rain threat ends with rain showers this morning. Additional rain this afternoon for the Islands and far southeast Massachusetts.

- Snow squall possible late afternoon, followed by strong wind gust early this evening into early Monday morning across the Berkshires.

- Mainly dry conditions early next week, trending more unsettled by mid-week with periodic showers. Monitoring a potential coastal system late next week.

DISCUSSION

KEY MESSAGE 1...Freezing rain threat ends with rain showers this morning. Additional rain this afternoon for the Islands and far southeast Massachusetts.

Widespread precipitation trending more scattered with the arrival of the dry slot. Temperatures across all of southern New England are hovering above freezing, mid to upper-30s, freezing rain threat has passed. Rest of the rain through early morning is concentrated to the south coast of RI and MA, Cape Cod, Martha's Vineyard, and Nantucket. There is a brief lull mid-morning, a resurgence of rain develops off the coast due to a strong baroclinic zone. Off shore a moisture plum from the Gulf coast follows the Gulf Stream, pumping in high PWATs. Light rain is anticipated through this afternoon with low clouds across most of southeastern New England, steadier rain is most likely for Nantucket through the afternoon. High-res guidance captures this well, derived POPs from a blend of the CAMs. Our winds begin to ramp up this afternoon ahead of a shortwave trough. More on this and the potential for CAA snow showers or a snow squall in the next section.

KEY MESSAGE 2...Snow squall possible late afternoon, followed by strong wind gust early this evening into early Monday morning across the Berkshires.

Shortwave trough pushes through the northeast late this afternoon, and brings a treat of a snow squall or two. Don't believe this will reach the level experienced on New Year's Day, but never the less, after a period of moderate rainfall, treatment probably washed off the roads, and any quick hitting snow could lead to poor visibility and a fast accumulation of snow. The shortwave will not have a lot of moisture to work with, PWATs less than 0.25". However, there is good 850mb temperature falls, increasing lapse rates, leading to a little instability. Viewing the CAMs to get a sense for the timing it would appear this line arrives to western MA/CT around 5 PM and crosses southern New England, reaching the I-95 corridor by 9 PM. Do think this line of snow showers will lose some steam as it traverses from west to east. Nevertheless, if you are traveling this afternoon or early evening, be aware of this potential threat. Snowfall is minimal, not widespread, where his squall occurs a quick coating to as much as an inch is probable, in 20-40 minutes window.

It will get windy behind this line of snow showers as well. As we have been advertising, modest CAA will allow for a period of strong wind gusts overnight into Monday morning. Highest confidence for gusts to reach up to 50 mph are in the Berkshires, this is where a Wind Advisory has been issued, 9 PM Sunday to 9 AM Monday. Reasoning is a modest low-level jet, winds range of 45 to 55 knots. Don't think will be able to tap into all this wind, mixing is intermittent while the strongest gusts across the Berkshires near 50 mph, elsewhere gusts of 30 to 40 are likely. Will need to review the 12z set of guidance for northern Worcester County, as of now gusts are marginal, decided to hold off on the advisory here. But a few gusts of 40 to 45 mph are possible. Timing this out, winds are noticeably stronger 8 PM to midnight, with the strongest gusts between midnight and 6 AM. Will still have breezy conditions through the morning hours of Monday, but not to the same extent, something like 20 to 30 mph.

KEY MESSAGE 3...Mainly dry conditions early next week, trending more unsettled by mid-week with periodic showers. Monitoring a potential coastal system late next week.

Early Week:

Conditions are expected to remain primarily dry through the early part of next week. After seasonable temperatures Monday, temperatures trend warmer for Tuesday and Wednesday with highs in the 40s by mid-week. A weak shortwave moving through the flow Tuesday night into Wednesday may trigger scattered light rain or snow showers.

Late Week:

There is general agreement among ensemble guidance for the upper- level pattern to shift toward a more amplified trough pattern across the east by late week. This transition brings a return to colder temperatures near to slightly below normal. We continue to monitor the potential for development of a coastal low near/offshore sometime Thursday into Friday. While a favorable track could bring widespread precipitation to southern New England, significant uncertainty remains. Model guidance has been showing plenty of spread in solutions and lacking run to run consistency especially with regard to the track, timing, strength of the surface low. Low tracks range from direct track across southeast MA to a complete miss offshore east or southeast of southern New England. The evolution of the mid-level trough and potential closing of the 500mb low remain unclear as well. Given these variables, the potential for a coastal low to impact the region is low confidence. Will continue to monitor trends as the details come into better agreement among guidance.

AVIATION /07Z SUNDAY THROUGH THURSDAY/

Forecaster Confidence Levels...

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

TAF Update: 06z

Through 12z... Moderate confidence.

IFR/LIFR, showers lingering into this morning. Significant LLWS concerns for the Cape and Islands tonight as 2kft winds approach 60 to 70 knots from the SW while a steep low level inversion could keep surface winds under 20 knots from the SE.

Today... High confidence in trends, moderate confidence in timing.

Winds turn WNW this morning, CIGS are slow to improve until this afternoon when drier low level air begins to work in behind the low. Rain showers and low CIGS will linger for the Cape and the Islands for much of the day. A snow shower or a brief snow squall late this afternoon, mainly 22z-02z, have moderate confidence (40%) in this occurring. Have opt'd to include PROB30 in TAF.

Tonight... High confidence in trends, moderate in timing.

VFR. Gusty W to WNW wind, 15-20 knots, gusts 35 to 45 knots.

KBOS Terminal... Moderate Confidence.

IFR/LIFR through mid-morning with lingering showers and drizzle. Only moderate confidence on when CIGS improve on Sunday. Current expectation is CIGS wont improve until late Sunday morning to early afternoon. A snow shower or a brief snow squall late this afternoon, mainly 22z-02z, have moderate confidence (40%) in this occurring. Have opt'd to include PROB30 in TAF.

KBDL Terminal... Moderate Confidence.

IFR CIGS, showers linger until day break. CIGS improve to VFR after 19z. A snow shower or a brief snow squall late this afternoon, mainly 22z-02z, have moderate confidence (40%) in this occurring. Have opt'd to include PROB30 in TAF.

Outlook /Monday through Thursday/...

Monday: VFR. Strong winds with local gusts up to 40 kt.

Monday Night: VFR. Breezy.

Tuesday: VFR.

Tuesday Night: VFR. Breezy.

Wednesday: VFR. Breezy. Slight chance RA.

Wednesday Night: Mainly VFR, with local MVFR possible. Chance RA.

Thursday: VFR. Chance RA, chance SN.

MARINE

Forecaster Confidence Levels...

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

Today through Sunday Night... High confidence.

Rain showers today as a front pushes off shore and stalls southeast of Nantucket. This front will be a source of continued rain for today. E wind becomes W mid-morning, with speeds increasing afternoon, gusting 25 to 30 knots. Early evening westerly gale force winds are expected along with seas on the outer waters building to 8 to 11 feet. Near shore waters are 4 to 7 feet. These rough conditions continue through the night and first half of Monday.

Outlook /Monday through Thursday/...

Monday: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas.

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

Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.

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

Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Slight chance of rain.

Wednesday Night: Winds less than 25 kt. Local rough seas. Chance of rain.

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

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...Winter Weather Advisory until 10 AM EST this morning for MAZ002-008-009. Wind Advisory from 9 PM this evening to 9 AM EST Monday for MAZ002-008-009. RI...None. MARINE...Gale Warning from 7 PM this evening to 7 AM EST Monday for ANZ230>237-251. Gale Warning from 7 PM this evening to 10 AM EST Monday for ANZ250-254>256.