textproduct: Boston / Norton

SYNOPSIS

A cold front should bring some showers tonight into Saturday, followed by dry and mild weather Saturday afternoon. Another low pressure and cold front brings another round of rain Sunday into early Monday with breezy southerly winds. Trending cooler Monday, and especially by Tuesday, with below normal temperatures with gusty winds making it feel even chillier Tuesday. Temperatures slightly moderate Wednesday before a reinforcing trough arrives bringing back chillier temperatures for late week. Some flurries/sprinkles possible near the Berkshires and some ocean effect showers possible towards the middle of next week.

NEAR TERM /UNTIL 6 AM SATURDAY MORNING/

Key Messages:

* Overcast with frontal rain showers between 7 PM to 4 AM for areas north/west of I-95. Rainfall less than a quarter inch, before drying out late tonight.

* Showers, with a low risk for thunderstorms overnight for coastal RI and SE MA, Cape and Islands and nearby waters after midnight.

Low pressure moving across southeast Canada will swing its associated fronts across southern New England tonight. This should generate some rain showers across southern New England tonight. There is a low risk for thunderstorms late tonight as a SW low level jet moves past the Cape and Islands. This forcing could be enough to maximize the 100-200 J/kg CAPE values. Not expecting anything especially strong, but cannot dismiss the idea.

Mainly S to SW winds should keep temperatures much higher than what we saw this morning. Expecting low temperatures tonight to be just below our normal high temperatures for early November.

SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/

Key Messages:

* Off-and-on rain showers could linger into Sat morning for the Cape, but drying out by late morning/noontime.

* Mild conditions for November, but with more seasonable lows for Saturday night.

Forecast challenge for Saturday remains the timing of showers ending over southeast New England. The steadiest rains will have ended, but could see clouds and off-and-on showers continuing into a good part of the morning before trudging eastward/offshore and drying out.

Modest cold advection takes place Saturday evening with a light W to NW wind, which eventually turns more onshore/NEly in response to the next wave of low pressure moving through the OH Valley.

LONG TERM /SUNDAY THROUGH FRIDAY/

Key Messages:

* System brings a period of rain and breezy winds Sunday into Monday.

* Trending cooler early next week, with below normal temperatures.

* Gusty winds Tuesday. 30-35 mph, locally up to 40 mph.

* Isolated shower/sprinkle or flurry over the higher terrain and some ocean effect showers for Cape/Islands. Round of showers possible later Wednesday.

Details...

Sunday - Monday:

Unsettled to start the period as a low pressure system moves across the region Sunday into Monday with a surface low tracking over NY and a weak secondary low tracking through or just offshore of southern New England. Sunday, a weak warm front shifts northward into southern New England with higher moisture advecting into the region within the southerly flow aloft. Weak lift ahead of the incoming cold front will be enough to support showers. There are still differences among model guidance on the timing of the showers as models differ on the speed and exact track of the surface features. Overall, showers should arrive sometime in the late afternoon-evening timeframe lifting out early Monday morning. They should be on the lighter side with ensemble means ranging 0.25-0.50" for totals.

A deep upper level low and trough moves across the Great Lakes toward the region Monday, eventually pushing in a cool airmass into southern New England. For the day Monday, may see a few remnant showers in the AM. Models indicate potential for another offshore low passing well offshore, but may track close enough west to bring showers for mainly the Cape later in the day. High temperatures should be similar to Sunday, but will depend on how far north the warm front makes it. Some colder air may seep far enough south to keep it in the upper 40s across the higher terrain of the interior while the warm front keeps temperatures in the upper 50s for the Cape and south coast.

Tuesday-Friday:

Strong cold air advection into Tuesday as the deep upper trough shifts eastward bringing the core of the coldest air into the region. This will likely bring in the coldest air of the season so far with 850mb temperatures anomalies showing well below normal temperatures (-7 to -10C). This will support chilly temperatures with upper 30s for the higher terrain and 40s elsewhere. NW flow aloft with 850mb winds 40-50 kts. With CAA and ample mixing, higher winds should be able transfer down to the surface with gusts 30-35 mph possible, potentially up to 40 mph. This will make it feel even chillier, with it feeling like upper 20s across the higher terrain and 30s elsewhere. Can't rule out a few lake effect showers to survive the trek over the Berkshires which would bring sprinkles, perhaps a flurry for the higher spots. Ocean effect showers will be possible with some potentially brushing the Cape and Islands in the WNW flow.

Temperatures moderate slightly Wednesday as the core of the coldest air shifts eastward with the upper trough. It will still be on the cooler side with highs in the 40s for the higher terrain and low 50s elsewhere. A weak shortwave trough moves through later Wednesday, which will bring showers across the region. Can't rule out a lake effect shower earlier in the day to again make it to the east slope of the Berkshires, potentially as a flurry or very light shower. Colder airmass works back in for the end of the week with below normal temperatures returning to the forecast and chances for some ocean-effect showers and a isolated remnant lake-effect shower out west.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

Forecaster Confidence Levels...

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

Tonight: Moderate confidence.

VFR CIGS gradually decrease to MVFR as a frontal system approaches. A quick round of light to moderate rain is anticipated to move from west to east from 03-06z tonight, ending between 08-11z tomorrow morning. CIGS behind the front will drop to low end MVFR to IFR. Winds overnight stay southerly gusting up to 20 knots, but a low level jet aloft will bring wind shear concerns as 2-5kft winds increase to 45-55 knots.

Saturday: Moderate confidence.

CIGS gradually improve to VFR by mid morning, but could hang around the 030 to 040 level through the afternoon. There could be some post frontal showers moving west to east mid morning. Winds turn westerly and remain breezy around 10-15 knots.

Saturday Night: High confidence.

VFR. Easing WNW winds, then shift to light NE by 12z Sun.

KBOS Terminal...Moderate confidence in TAF.

VFR this afternoon and evening. Increasing winds aloft will lead to wind shear concerns with 40-50 knot winds at 2kft. Rain moves in around midnight along with CIGS gradually falling to MVFR levels with IFR CIGS possible. Better chance for IFR cigs behind the front, but confidence is moderate at this time.

KBDL Terminal...Moderate confidence in TAF.

VFR this afternoon. Rain moves in around 03z tonight. CIGS gradually drop to MVFR with the rain. There could be some period of IFR CIGS behind the rain, but confidence was not high enough to include in TAF at this time

Outlook /Sunday through Wednesday/...

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

Sunday Night: MVFR/IFR conditions possible. Breezy. RA.

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

Monday Night: Breezy. Slight chance RA.

Veterans Day: Windy with gusts up to 30 kt. Slight chance RA.

Tuesday Night: Windy with gusts up to 30 kt.

Wednesday: Windy with gusts up to 35 kt. Slight chance RA.

MARINE

Forecaster Confidence Levels...

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

Low pressure well north of the waters will push a cold front across the waters late tonight into Saturday. SW winds prevail tonight, and are expected to become gusty ahead of this front. Could see a few gusts up to gale force, but still thinking a Gale Warning would be overkill. Thus, Small Craft Advisories extended into Saturday night for some waters. Winds become W during Saturday afternoon, then NW and diminish Saturday night.

Rain develops tonight on most waters, with a possibility of thunder/lightning over the waters near/south of the Islands after midnight. Rain should come to an end by Saturday afternoon, then persist into Saturday night.

Outlook /Sunday through Wednesday/...

Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Rain likely.

Sunday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Rain, isolated thunderstorms.

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

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

Veterans Day: Strong winds with gusts up to 40 kt. Rough seas up to 15 ft. Chance of rain.

Tuesday Night: Strong winds with gusts up to 40 kt. Rough seas up to 16 ft. Slight chance of rain.

Wednesday: Strong winds with gusts up to 35 kt. Rough seas up to 14 ft. Slight chance of rain.

TIDES/COASTAL FLOODING

Breezy S/SE flow in combination with lingering higher astronomical tides will bring a risk for some minor coastal flooding over the coming days. This will depend on the track of a surface low, as it will influence wind direction/speed fields. These details remain lower confidence at this time. Guidance keeps most locations below minor flood stage. However, locations like Nantucket Harbor will need to be monitored as reasonable worst- case solutions hover near minor flooding.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 AM EST Saturday for ANZ230-236. Small Craft Advisory until 10 AM EST Saturday for ANZ231>234- 250-251. Small Craft Advisory until 7 PM EST Saturday for ANZ235-237. Small Craft Advisory until 10 PM EST Saturday for ANZ254. Small Craft Advisory until 4 AM EST Sunday for ANZ255-256.