textproduct: Boston / Norton

SYNOPSIS

An arctic front moves through overnight 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 /THROUGH MONDAY/

Key Messages...

* A mostly dry arctic front drops through overnight bringing in a period of below normal temperatures.

Quiet end to the weekend in progress; main changes this afternoon are in influx of mid/high clouds ahead of a weak mid level shortwave that crosses northern New England overnight. At the surface a moisture starved arctic front drops through between 8pm and 3am. Again, moisture is so limited that it will more than likely be a dry frontal passage; worst case is some light snow showers in northern MA amounting to a coating of snow. A much colder airmass moves overhead with 850 mb temps dropping from -7C Sunday to -17C Monday. As the surface low deepens over the Gulf of Maine Monday the pressure gradient increases so breezy winds will make highs in the 20s feel like the teens.

SHORT TERM /MONDAY NIGHT/

Key Messages...

* Well below normal temperatures.

High pressure builds overhead Monday night and the boundary layer decouples; this allows the already cold airmass to cool even more. Expect lows in the single digits (inland) and low/mid teens (along the coast).

LONG TERM /TUESDAY THROUGH SUNDAY/

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.

Rather good overall agreement with the synoptic pattern through Tuesday. After then, the timing and amplitude differences continue to grow into next weekend. The overall pattern suggests a deepening mid level trough over the eastern USA for the second half of this upcoming week. The largest detail differences involve the evolution of a mid level cutoff somewhere between Hudson Bay and Quebec. Our proximity to this particular feature will play a role in how much lift can be used to generate cold advection showers across our region.

Surface high pressure should move offshore Tuesday, permitting a low pressure moving into the Great Lakes to push its associated fronts across southern New England Tuesday night into Wednesday. Not expecting a lot of precipitation during this time, but some light snow will be possible at night, and especially across the higher terrain. Anticipating more rain than snow Wednesday as temperatures rise to near normal levels.

Late next week could feature some cold advection showers, but there are no strong lifting mechanisms anticipated at this time. There are also questions about the amount of moisture which could be available. While there is a prolonged period where these showers are possible, there should be many dry hours late next week. There is higher confidence in the arrival of colder air by the end of next weekend with below normal temperatures returning to our region.

AVIATION /00Z MONDAY THROUGH FRIDAY/

Forecaster Confidence Levels...

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

00Z TAF Update:

Tonight...High Confidence.

Radar as of 645 PM shows some light echoes on radar across central MA. So far, no observations have reported snow. This will push westward and given recent obs, would bring a light flurry at most.

VFR conditions. Light and variable winds increase out of the SW early this evening, eventually becoming NW 06-12Z with cold frontal passage, gusting 15 to 22 kts. Low chance for an isolated snow shower with the frontal passage.

Monday...High Confidence.

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

Monday night...High Confidence.

VFR. Winds light and variable.

KBOS Terminal...High Confidence in TAF.

KBDL Terminal...High Confidence in TAF.

Outlook /Tuesday through Friday/...

Tuesday: VFR. Breezy.

Tuesday Night: Mainly VFR, with local MVFR possible. Breezy. Chance SN, slight chance RA.

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

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

Thursday: VFR. Breezy.

Thursday Night: VFR. Breezy. Slight chance SN.

Friday: VFR. Chance SN, chance RA.

MARINE

Forecaster Confidence Levels...

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

Today through Monday night...High confidence.

Light S winds become NW tonight around 10-15 kt. Seas 2-3 ft.

Winds increase with a cold front Sunday night/Monday morning with seas building to 5-7 ft over the outer waters through Mon. Gusts between 20-30 kt possible across all waters Mon morning, with occasional gusts to 35 kt possible for the northern outer waters. Small Craft Advisories in effect for the waters starting at 06z tonight, continuing through 06z Tue for the outer waters and ending at 21z today for the coastal waters.

Monday night...High confidence.

N winds 10-15 kts gusting 15-20 kts early, diminishing through the night. Seas decreasing to 2-4 ft after midnight.

Outlook /Tuesday through Friday/...

Tuesday: Winds less than 25 kt.

Tuesday Night through 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.

Thursday Night: Winds less than 25 kt. Local rough seas. Slight chance of rain, slight chance of snow.

Friday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain, chance of snow.

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.