textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes to the forecast. We did issue a coastal flood statement for the Friday afternoon high tide along north facing beaches of Cape Cod Bay and Nantucket sound for some splashover/very minor coastal flooding possible.

KEY MESSAGES

- Widespread rain overspreads the region this evening and changes to a period of wet snow in the high terrain before tapering off early Fri. Any snow accumulations very minor with the greatest risk across the northern ORH Hills/Berks. Lingering rain Fri afternoon will mainly be across RI/SE MA and especially near the south coast.

- Cooler, cloudy weather with northwest breezes this weekend. Mainly dry weather, but hit or miss scattered showers possible Saturday afternoon.

- Prolonged stretch of dry weather early to mid next week, with a warming trend to temperatures.

DISCUSSION

KEY MESSAGE 1...Widespread rain overspreads the region this evening and changes to a period of wet snow in the high terrain before tapering off early Fri. Any snow accumulations very minor with the greatest risk across the northern ORH Hills/Berks. Lingering rain Fri afternoon will mainly be across RI/SE MA and especially near the south coast.

Outside of a few spot showers across southern New England this afternoon mainly across the interior...dry weather dominated. Despite a developing ESE low level jet...the model cross sections indicated a lot of low level dry air in the soundings which was resulting in mainly dry weather. However...as low pressure emerges off the mid-Atlantic coast a stronger LLJ/forcing will move into the region. As a result...we expect widespread rain to overspread the region this evening.

Thermal profiles do indicate that the atmosphere will become cold enough for a changeover to wet snow in the high terrain of the Berks and Worcester Hills overnight. The problem is that the overall duration/intensity of the wet snow looks to be limited. This a result of shortwave energy over southern Quebec which compresses the system to the south. You can see that by looking at the mid level centers/surface low pressure contours. It takes on more of an oval instead of spherical shape which indicates the storm being suppressed further south by northern stream shortwave energy. Therefore...the bulk of the precipitation will be ending early-mid morning Fri especially north of I-90. This should result in any snow accumulations being very minor across the high terrain of just a coating to perhaps an inch or two...generally at or above 1000 feet. Little if any travel impacts are expected other than perhaps brief slushy secondary roadways above 1000 feet with the greatest risk near 1500 feet along the east slopes of the Berks.

As we mentioned...the low pressure being suppressed to the south will result in the leftover rain Friday afternoon mainly confined to parts of RI/SE MA and especially near the south coast. There is a low risk that if the precipitation falls heavy enough a few brief snowflakes may even mix in for a time...but no accumulations/impacts expected. Otherwise...a raw chilly day with a gusty N wind and Fri afternoon temperatures mainly in the upper 30s to the lower 40s.

Otherwise...an abundance of clouds may linger Fri night given cyclonic flow but nothing more than a few spot showers across the far southeast New England coast. Otherwise...low temps should be held mainly in the 30s given lingering clouds and many places not decoupling.

Lastly...gusty northerly winds coupled with astronomical high tides may result in splashover/very minor coastal flooding along north facing beaches across Cape Cod Bay and Nantucket sound. No significant impacts are expected and any splashover/very minor coastal flooding will be quite short-lived, no more than an hour on either side of high tide.

KEY MESSAGE 2...Cooler, cloudy with northwest breezes this weekend. Mainly dry weather, but hit or miss scattered showers possible Saturday afternoon.

In the wake of the Friday storm system, we'll be left in a cool and moist cyclonic flow aloft as we move into the weekend. This will keep our weather pattern unsettled with more clouds than sun with northwesterly breezes. Amid the broader cyclonic flow aloft, models depict a pretty strong shortwave disturbance aloft rotating southward through New England Saturday afternoon into early evening. This will at least increase RH through the column with dynamic support associated with the shortwave could yield some scattered, hit-or-mostly-miss showers as the shortwave digs southward. Went ahead and added a mention of scattered showers for Saturday afternoon over the dry NBM, although limited to nil impacts with these showers.

With the cool cyclonic flow (925 mb temps around 0 to -2C) and mostly cloudy/overcast conditions, highs on Saturday could end up rather chilly in the low to mid 40s lower elevations and upper 30s/near 40 in the Berkshires and Worcester and Tolland hills. Slightly milder conditions in the mid/upper 40s lower elevations and low to mid 40s higher elevations for Sunday.

KEY MESSAGE 3...Prolonged stretch of dry weather early to mid next week, with a warming trend to temperatures.

Strong multi-ensemble support for a modifying weather pattern as 500 mb heights rise significantly, moving into early to midweek. This implies a steady warming trend to temperatures Monday through Wednesday (and potentially longer), but also supports several days of dry weather as surface ridging takes hold. Highs should rebound back into the upper 50s to mid 60s by Wed, which are about 5-10 degrees above normal, and there is potential for those highs to be a couple degrees warmer as we get entrenched into the drier weather pattern.

AVIATION /19Z THURSDAY THROUGH TUESDAY/

Forecaster Confidence Levels...

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

18z TAF Update:

Through 00z Friday: High confidence.

Mainly OVC VFR (FEW-SCT MVFR decks but VFR should predominate), more persistent MVFR-IFR ceilings at ORH with intermittent showers. Rain begins to develop south coast around 21-23z and into the rest of SNE 23-00z. NE winds increasing to 10-15 kt with gusts 20-25 kt.

Tonight: Moderate confidence.

Conditions deteriorate to widespread MVFR ceilings/visbys with intervals IFR ceilings/visbys, as rain intensities becoming steady light to moderate tonight and continues into overnight. Rain may begin to mix with wet snowflakes at ORH around 09-10z but accum on runways minimal. NE/NNE winds 13-18 kt with gusts 25-30 kt, strongest gusts southeast New England.

Friday: Moderate confidence.

MVFR-IFR rains and ORH rain/snow showers continue; although improving visbys as rain intensity begins to taper off by 13-15z northern MA, around 15-18z for the interior, then improving by 19- 22z for southeast New England and Cape Cod/Islands. Ceilings may only improve to MVFR levels during the daytime hours. NE/N winds around 12-16 kt with gusts 25-28 kt.

Friday Night: High confidence in TAF/trends but moderate on timing.

Should be starting with widespread MVFR ceilings; the trend should be toward BKN/OVC VFR, but the exact timing isn't certain. Looks like more substantial improvement takes place after 06z Sat. North to northwest winds 8-12 kt with gusts to 20 kt.

KBOS Terminal...Moderate confidence in TAF. OVC VFR should deteriorate to widespread MVFR in RA and lowering ceilings after 23- 00z. Period IFR visbys in RA possible overnight but difficult to time.

KBDL Terminal...Moderate confidence in TAF. OVC VFR should deteriorate to widespread MVFR in RA and lowering ceilings after 22- 23z. Period IFR visbys in RA possible overnight but difficult to time.

Outlook /Saturday through Tuesday/...

Saturday: Mainly VFR, with local MVFR possible. Chance FZRA, isolated SHRA.

Saturday Night through Sunday Night: VFR. Breezy.

Monday through Tuesday: VFR.

MARINE

Forecaster Confidence Levels...

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

Tonight through Friday night...High confidence.

* Gale Warnings posted tonight into Friday

Low pressure emerges off the mid Atlantic coast tonight and tracks near the Benchmark Fri. The pressure gradient will be strong enough to generate N-NE wind gusts of 35 knots across our open waters tonight into Fri along with 5 to 10 foot seas. Gale Warnings continue for our open waters tonight into Friday. The low moves east of the the Benchmark Fri night and pressure gradient weakens enough for winds to diminish to small craft advisory levels.

Outlook /Saturday through Tuesday/...

Saturday: Winds less than 25 kt. Areas of rough seas. Isolated rain showers.

Saturday Night through Sunday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain.

Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain.

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

Monday Night through Tuesday: Winds less than 25 kt.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 6 PM this evening to 7 PM EST Friday for ANZ230-236. Gale Warning from 1 AM to 7 PM EST Friday for ANZ231>235-237- 255-256-282-283. Gale Warning from 6 PM this evening to 7 PM EST Friday for ANZ250-251-254-280-281.