textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes to the forecast.

KEY MESSAGES

- Considerable clouds, gusty SW winds, but nothing more than a few brief spot showers today. Highs mainly in the 70s, but cooler upper 50s/60s towards the south coast.

- Unseasonable summerlike warmth Tue & Wed with highs mainly in the upper 70s and 80s but cooler on the coast at times especially across northeast MA. Scattered diurnally driven showers and a few t-storms possible with even a low risk for isolated severe weather.

- Summerlike warmth may persist Thu/Fri/Sat across parts of the region with highs in the U70s & 80s...But a backdoor cold front may bring much cooler temps at times especially across eastern & northeast MA. A few showers possible at times...but dry weather dominates.

- A cold front crosses the region Sun/Sun night with some showers... bringing an end to the summerlike warmth by the start of the next work week with much cooler temps.

DISCUSSION

KEY MESSAGE 1...Considerable clouds, gusty SW winds, but nothing more than a few brief spot showers today. Highs mainly in the 70s, but cooler upper 50s/60s towards the south coast.

A shortwave and associated warm front crosses the region today. The associated southwest 50+ knot low level jet in the warm advection pattern will result in considerable cloudiness...but nothing more than a few spot showers. Nonetheless...even with just a few peeks of sunshine highs should reach into the 70s for much of the region with upper 50s/60s near the south coast, Cape and Islands. Dewpoints rising above 50 will make it feel quite mild compared to this weekend. We also expect gusty southwest winds on the order of 25 to 35 mph and perhaps a few gusts near 40 mph near the climo favored areas in the vicinity of the upper Cape.

KEY MESSAGE 2...Unseasonable summerlike warmth Tue & Wed with highs mainly in the upper 70s and 80s but cooler on the coast at times especially across northeast MA. Scattered diurnally driven showers and a few t-storms possible with even a low risk for isolated severe weather.

High confidence in summerlike warmth for much of the region...at least away from the immediate coast Tue and Wed. An upper level ridge of high pressure over the Gulf will result in westerly flow aloft with well above normal height fields. High temperatures should be in the upper 70s and 80s in most locations...at least away from the immediate coast. Marine influences near the immediate south coast, Cape and Islands will likely hold high temps in the 60s across those locales. In addition...a backdoor cold front lurking in the vicinity of eastern MA may bring localized cooler temps at times along the immediate coast. This is especially true across northeast MA...where temps could fall into the upper 40s and 50s if the high resolution NAM model is correct by Wed.

We also should mention that given the anomalous warm airmass in place and westerly flow aloft...we will need to watch for scattered diurnally driven showers and a few thunderstorms Tue and Wed. In fact...the CSU machine learning probs even indicating some low probs of severe weather. And the HREF also does have some 2-5 KM Updraft helicity swaths across western and northern MA on Tue. So there is a low risk for isolated severe weather Tue and Wed afternoon/evenings. If it were to happen...western MA would be favored and particularly west of I-91 given main axis of instability west of our region.

So in a nutshell...high confidence in summerlike warmth in the upper 70s and 80s Tue and Wed inland from the coast. However...along the coast especially northeast MA there is a large range in possible outcomes from temps in the 40s/50s vs 70s/80s depending on the location of the backdoor cold front. We will have a better idea as we get further into the high resolution model data...but across northeast MA and especially eastern Essex county it may end up much cooler at times than the rest of our region.

KEY MESSAGE 3...Summerlike warmth may persist Thu/Fri/Sat across parts of the region with highs in the U70s & 80s...But a backdoor cold front may bring much cooler temps at times especially across eastern MA. A few showers possible at times, but mainly dry weather is expected.

Forecast uncertainty increases during the latter half of the week. The upper level atmosphere remains similar with westerly flow aloft and well above normal height fields. However...a couple waves of low pressure tracking across northern New England may force the backdoor cold front that has been lurking across northeast MA further southwest at times. The question is how far southwest and when exactly. The further back into the interior you get will bring the greatest potential for summerlike warmth in the upper 70s and 80s continuing. The greatest risk for the cooler temps will be across eastern MA and especially northeast MA. We will need to get into the high resolution model time window to have a better idea on this potential.

A few showers are possible at times...but dry weather should dominate the vast majority of the time.

KEY MESSAGE 4...A cold front crosses the region Sun/Sun night with some showers...bringing an end to the summerlike warmth by the start of the next work week.

A cold front will finally cross the region sometime Sun into Sun night...probably with a period of showers. While timing of this front remains uncertain...this should finally bring an end to the unseasonable summerlike warmth with much cooler temps by the start of the next work week.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Forecaster Confidence Levels...

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

12z TAF Update...Moderate confidence

VFR conditions likely dominate through Tuesday. However MVFR- IFR cigs/vsbys to develop towards the south coast, Cape, Islands this morning and persist into tonight. This a result of that high dewpoint air advecting over the relatively cold ocean. Across the rest of the region...VFR conditions dominate but a period of MVFR ceilings are possible this morning. A few brief spot showers possible at times today...but dry weather dominates. Otherwise...SW wind gusts of 20 to 30 knots develop this morning with a few gusts near 35 knots towards the upper Cape. LLWS will also be a concern especially into mid-morning before the stronger gusts develop. Winds diminish tonight but remain from a SW-WSW direction but generally 10 knots or less during the overnight hours.

VFR conditions dominate Tue...but scattered showers and a few t- storms will be possible late Tue into Tue evening with the greatest risk across interior southern New England. This may bring briefly localized lower cigs/vsbys. S-SW winds 7 to 15 knots but with sea breezes for a time along parts of the immediate eastern MA coast

KBOS Terminal... Moderate confidence in TAF.

KBDL Terminal... Moderate confidence in TAF.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday: VFR. Breezy. Chance SHRA, isolated TSRA.

Wednesday Night: VFR. Chance SHRA, isolated TSRA.

Thursday: Mainly VFR, with local MVFR possible. Chance SHRA.

Thursday Night: VFR. Chance SHRA.

Friday: VFR. Chance SHRA, slight chance TSRA.

MARINE

Forecaster Confidence Levels...

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

Today through Tuesday...High confidence.

A modest southwest LLJ will bring small craft wind gusts of 30+ knots and choppy seas to all waters today. We do expect some 35 knot wind gusts in the climo favored areas near Buzzards/Cape Cod Bays and BID/ACK sounds where we have gale warnings posted. Core of LLJ shifts east of the region tonight allowing winds to drop below small craft thresholds tonight and remain below criteria on Tue. Seas will also gradually subside...but will take until Tue afternoon for small craft seas to diminish below criteria across our southern outer- waters.

The other concern for mariners will be for areas of fog developing today and persisting into tonight across the southern waters as high dewpoint air advects in over the relatively cold ocean.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers.

Wednesday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers.

Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers.

Thursday through Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers.

Friday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ230- 236. Gale Warning until 6 PM EDT this evening for ANZ231>234. Small Craft Advisory until 5 AM EDT Tuesday for ANZ235-237. Small Craft Advisory until 2 AM EDT Tuesday for ANZ250-251. Small Craft Advisory until noon EDT Tuesday for ANZ254>256.