textproduct: Boston / Norton

WHAT HAS CHANGED

No major changes, though temperatures have trended cooler for next week.

KEY MESSAGES

- Cooler today with continued dry conditions.

- Some snow showers remain possible Sunday night into Monday morning. Minor accumulations with little to no impacts expected.

- An active, low-predictability pattern will bring milder temperatures with periodic rain/snow showers and breaks of dry weather Wednesday through the upcoming weekend.

DISCUSSION

KEY MESSAGE 1...Cooler today with continued dry conditions.

A weak cold front is expected to push southward across the region early this morning resulting in cooler temperatures. 925mb temperatures drop 2-4 degrees from yesterday yielding high temperatures in the 30s. Despite a frontal passage, there won't be a strong pressure gradient to support gusty winds. Light N winds may lighten further and transition NNE to E later in the afternoon. If there is more of an onshore component, temperatures may end up cooler on the eastern coast(low 30s) relative to more inland (mid 30s).

KEY MESSAGE 2...Some snow showers remain possible Sunday night into Monday morning. Minor accumulations with little to no impacts expected.

Model guidance continues to keep the coastal storm to our south Sunday night into Monday. This has lowered the risk for higher impact winter weather. However, a period of light snow showers remains possible the south coast and portions of CT and west MA.

Deterministic and ensemble guidance continues to show the tracking of two separate waves. A southern stream wave tracks across the southeast U.S. with a surface low developing and tracking off of the coastal Carolinas into the outer mid-atlantic waters late Sun-Mon. In a similar timeframe, a northern stream shortwave trough tracks east across the Great Lakes toward southern New England. What has remained consistent from previous model runs is that these features don't phase in a timely manner. As a result, the surface low is suppressed and tracks well offshore. This has reduced the risk of a impactful winter storm for southern New England. However, this doesn't mean all snow potential is gone. The waves will help bring a plume of slightly above normal moisture with the highest moisture just offshore combined with with broad ascent. This would support light snow showers from the north wave, mainly in western/central MA and a potential "graze" impact from the offshore low with light snow for the south coast.

Any accumulations will be low, which is reflected well among ensemble guidance. Could see a dusting to a few tenths around the south coast and west interior MA/CT. 75th percentiles show around 0.5-1.0" possible for south coast and near Nantucket. However, it is also worth noting that the 25th percentiles of ensemble guidance also shows little to no accumulation, so this is a potential scenario as well. Overall, this at most would result in very minor impacts (if any) to areas Sunday night into early Monday morning.

Key Message 3...An active, low-predictability pattern will bring milder temperatures with periodic rain/snow showers and breaks of dry weather Wednesday through the upcoming weekend.

No major changes are expected to the forecast from Tuesday through Saturday. The overall synoptic pattern features a subtropical ridge building over the Gulf and Central America, which displaces the subtropical jet northward and results in generally zonal flow across the southern tier of the CONUS. This pattern supports an active regime with somewhat milder temperatures for southern New England.

Late Monday night into Tuesday, a weak northern-stream shortwave traverses the Northeast. With modest PWATs in place, scattered light snow showers are possible, mainly across interior portions of southern New England, with only minor accumulations expected.

From Wednesday through the upcoming weekend, unsettled conditions persist as multiple shortwave impulses eject from the Pacific and track across the CONUS. As noted by the previous forecaster, this pattern carries low-predictability regarding finer details such as timing and precipitation type. As warmer air advects into the region, thermal profiles will support a rain/snow mix at times, with the greatest potential for snow confined to the higher terrain of western and northern Massachusetts. It is worth emphasizing the precipitation is not expected to be continuous from Wednesday through Saturday, periods of dry weather are likely between system. However, confidence remains low in pinpointing the exact timing of these breaks at this range.

Temperature trend milder overall, though not the extent of feeling spring-like. Expect a return to near-seasonable or slightly above- normal temperatures, with daytime highs generally in the low to mid 40s and overnight lows in the upper 20s to lower 30s.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Forecaster Confidence Levels...

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

12z TAF Update:

Today: High confidence.

VFR. NW to N winds 6-12 kts, decreasing slightly in the afternoon and shifting more NE 5-10 kts. Winds may go VRB for period in afternoon at inland terminals.

Tonight: High confidence overall, though moderate for PVD, Cape and Islands.

Mainly VFR ceilings. Winds easterly at 5-10 kts. Dry weather for most terminals. Low chance for a snow shower mainly at PVD and Cape/Islands. Few snow showers possible in far west Massachusetts. Too low probability to include in TAF at this time. Main window would be 05-12Z. Brief MVFR possible in any showers.

Monday: High confidence.

VFR ceilings. Light NE/E winds 5-10 kts.

KBOS Terminal...High confidence in TAF. VFR. NW winds this morning turning N at 8-10 kts. Winds potentially wavering toward NE/E late afternoon/early evening as winds become light (and possibly VRB at times).

KBDL Terminal...High confidence in TAF.

VFR. Light winds N/NNE less than 10 kts today. Low chance for an isolated snow shower after 03Z tonight. Not high enough probability to include in TAF. Brief MVFR possible in showers.

Outlook /Monday Night through Thursday/...

Monday Night: Mainly VFR, with local MVFR possible. Isolated SHSN.

Tuesday: Mainly VFR, with local IFR possible.

Tuesday Night: VFR.

Wednesday: Mainly VFR, with local MVFR possible. Chance RA, slight chance FZRA.

Wednesday Night: MVFR/IFR conditions possible. SN likely, RA likely.

Thursday: Mainly VFR, with local IFR possible. Chance SN, slight chance RA.

MARINE

Forecaster Confidence Levels...

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

Today through Monday... High Confidence.

A cold front moving over the waters early this morning brings a period of slightly elevated NW winds over the northeastern waters. Occasional gusts to 25 kt are possible, but are not expected to be widespread. Seas 2-3 ft are still expected with the outermost areas of the northern waters seeing some pockets of 4 ft seas as that front pushes through. Some light freezing spray is possible for the northeastern waters as well.

High pressure takes control once more for the rest of the weekend, keeping seas and winds calmer for Sunday. A deepening low pressure system moves off the Mid-Atlantic coast Sunday night into early Monday morning, this will result in build seas for the southern outer waters, possibly reaching 3-5 ft. This may result in marginal small craft conditions Monday.

Outlook /Monday Night through Thursday/...

Monday Night: Winds less than 25 kt. Local rough seas.

Tuesday through Tuesday Night: Winds less than 25 kt. Areas of rough seas.

Wednesday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain.

Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Rain likely, chance of snow. Local visibility 1 to 3 nm.

Thursday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of snow, slight chance of rain.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...None.