textproduct: Boston / Norton

SYNOPSIS

Dry and cold today. An arctic front moves through overnight tonight into Monday morning with a low chance for brief scattered snow showers, primarily for northern MA. Well below normal temperatures Monday with an arctic airmass overhead. More unsettled overall next week with a few systems moving through the region. This will bring periodic chances for rain/snow showers starting Tuesday night, continuing into Saturday. Very gradual warming trend into Tuesday with highs around normal Wednesday/Thursday.

NEAR TERM /UNTIL 6 PM THIS EVENING/

Key Message:

* Mix of sun and clouds through the day

High pressure builds in for the start of the day ahead of a weak mid-level shortwave moving in from the west. Light winds prevail for much of the day with high pressure overhead, coming from mainly the NW for the first half of the day. Some brief clearing is expected in the mid morning hours before filling in through the afternoon ahead of the shortwave. Highs supported by 925 mb temperatures around -5C will likely be in the mid 30s for most, with low 40s for Cape Cod and the Islands.

SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/

Key Messages:

* Low chance for scattered snow showers tonight

* Arctic air returns for Monday

Associated with the shortwave moving across the region late Sunday is a moisture-starved cold front. This will usher in another arctic airmass to start the week, with 925 mb temperatures tanking to between -11C and -15C late tonight into Monday morning. Lows tonight will dip back into the mid to upper teens for most and into the low 20s for Cape Cod and the Islands.

Latest guidance has trended precipitation chances over southern New England down a bit and drier air aloft will aid in decreasing chances for spot snow shower or two. At most, a low chance for some snow showers lingers for northern MA.

NW winds pick up Sunday night into Monday post-front with good mixing, so gusts between 20-30 MPH are possible through much of Monday. The arctic airmass aloft remains over the region and high pressure builds back in briefly post-front. So, not much improvement from overnight temperatures is expected; 925 mb temperatures remain around -11C through the day, so highs in the 20s and 30s can be expected.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/

Key Messages:

* Periodic chances for precipitation next week starting Tuesday night, continuing through Saturday.

* Uncertainty in pattern details (timing, amounts, precip type), especially Wednesday onward.

Details...

Surface high pressure shifts into the region Monday night helping relax the pressure gradient. This will support decreasing winds; however, elevated winds may linger a bit longer over the waters overnight. Clear skies, light wind, and a well below normal airmass aloft will support temperatures dropping into the single digits and teens Monday night. Can't rule out a few higher elevation spots dropping a little below zero.

There is a consensus among ensemble guidance for shift to an active pattern starting later Tuesday, continuing through next weekend. The pattern features the passage of several embedded disturbances in the flow aloft bringing periodic chances of rain/snow showers through the week. However, there is still uncertainty in the details including timing of showers and expected amounts, especially mid- week onward.

The first shot at showers comes Tuesday night. Ensembles show light amounts with scattered snow showers bringing mainly a trace to an inch, with the greatest chance at an inch or greater for the higher elevations of interior MA. For the south coast and Cape/Islands, rain/snow showers are possible. Another round or two of showers is likely sometime Wednesday into Thursday. Precip type will become more clear as we gain more details about the system track and timing. Temperatures lean warmer for Wednesday during the day. This would favor rain or rain/snow showers higher up. The cold front swings through Weds nigh which may bring another round of rain/snow showers with it.

Some cold advection showers are possible later in the week. There is potential for yet another wave to move through Friday-Saturday. There is still plenty of uncertainty in the timing and track of the wave and low pressure which will influence the precipitation chances. Things will become more clear as we get closer. Something that is higher confidence is the arrival of colder air by the end of the weekend with below normal temperatures returning to the region.

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 winds 5-10 kts. After 18z, winds briefly may go VRB before shifting to the S and SE/ESE for BOS. Other terminals may see a similar pattern. Winds continue to shift toward the W/WSW after 00Z. Mid-level ceilings move in during the afternoon.

Tonight...High Confidence.

VFR. Mid-level ceilings early tonight. Winds shifting toward WSW after 00z 5-10 kts. Frontal passage overnight between 05-09Z. Gusts start to pick up after 06z at around 20 kts. Low chance of -SN for northern terminals. Probabilities too low to include in TAF.

Monday...High Confidence.

VFR. Gusty NW winds with gusts 20-30 kts. Winds gradually decreasing after 18Z.

KBOS Terminal...High Confidence in TAF.

KBDL Terminal...High Confidence in TAF.

Outlook /Monday Night through Thursday/...

Monday Night through Tuesday: VFR. Breezy.

Tuesday Night: Mainly VFR, with local MVFR possible. Windy with local gusts up to 30 kt. Slight chance RA, slight chance SN.

Wednesday: Mainly VFR, with local MVFR possible. Windy with local gusts up to 30 kt. Chance RA, chance SN.

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

Thursday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

Today through Monday...High confidence.

Tranquil boating conditions expected through today, with winds and seas below small craft advisory thresholds. Light S winds continue into most of today, then become NW tonight around 10-15 kt. Seas 3 ft or less all waters thru Sun.

Winds pick up post-front tonight into Mon and seas build to 5-7 ft over the outer waters through Mon. Gusts between 20-30 kt are possible across all waters Mon morning, with occasional gusts to 35 kt possible for the northern outer waters. Small Craft Advisories have been issued for the waters starting at 06z tonight, continuing through 06z Tue for the outer waters and ending at 21z today for the coastal waters.

Outlook /Monday Night through Thursday/...

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

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

Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Slight chance of rain.

Wednesday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Chance of rain.

Wednesday Night: Strong winds with gusts up to 35 kt. Areas of rough seas. Chance of rain.

Thursday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Slight chance of rain.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 1 AM to 4 PM EST Monday for ANZ231>235-237-251. Small Craft Advisory from 1 AM Monday to 1 AM EST Tuesday for ANZ250-254>256.