textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes to the forecast. We now have high confidence in springtime warmth for much of this week, especially Tuesday, along with the potential for minor river flooding within the next 7 days.

KEY MESSAGES

- Any lingering scattered showers depart by mid-morning with partial clearing this afternoon northwest of I-95...but low clouds, drizzle, and fog persist toward the Cape & Islands Otherwise...a significant warming trend today into Mon. Highs in the 50s to near 60 today & into the 60s Mon.

- Above normal temperatures next week. Trending more unsettled mid to late week with a round or two of precipitation possible.

- Expecting significant snowmelt over the coming week. Minor river flooding possible.

DISCUSSION

KEY MESSAGE 1...Any lingering scattered showers depart by mid- morning with partial clearing this afternoon northwest of I-95...but low clouds, drizzle and fog persist toward the Cape & Islands Otherwise...a significant warming trend today into Mon. Highs in the 50s to near 60 today & into the 60s Mon.

Any lingering scattered showers should come to an end by mid-morning as a shortwave/core of the low level jet departs. Otherwise...moist S-SW flow turns gradually turns to a more W direction during the afternoon. This should gradually allow partial clearing during the afternoon at least to the northwest of I-95. Further southeast... especially towards the south coast, Cape and Islands the southwest flow off the ocean will hold low clouds, drizzle and fog for a good portion of the day. High temps today are dependent on how quick the low clouds scour out. If they are slower to scour out...highs probably will be mainly in the middle 50s. However...partial clearing occurring on the earlier side may yield 60+ degree highs for a good portion of the region. Coolest readings today will be found near the south coast, Cape and Islands given the marine influence, low clouds and fog.

A drier airmass in place tonight with light/calm winds and mainly clear skies will allow low temps to drop into the 20s and 30s...to near 40 in the urban heat island of Boston and also parts of the Worcester Hills given the unseasonably mild temps aloft. This will set the stage for an unseasonably mild day across the region and temps we have not experienced since last fall. Given 925T near +10C and model cross sections indicating plenty of sunshine...expect high temps to reach into the 60s in many locations! Needless to say...the remaining snowpack will be melting away very quickly.

KEY MESSAGE 2...Above normal temperatures next week. Trending more unsettled mid to late week with a round or two of precipitation possible.

High pressure centered over the western Atlantic will continue to funnel warm, southwest flow into the region through Wednesday pushing 925 mb temps as high as 13-15C on Tuesday. This will likely be the pick of the week temperature-wise with highs reaching well into the 60s and even touching 70s in spots; the EPS ensemble guidance has trended up to a 50-60% chance of reaching 70F in parts of the CT valley so it's in the realm of possibility. There are two asterisks to the warmth: First, both Tue and Wed southerly flow off the water will keep the immediate south coast in the 50s. Second, guidance is less aggressive than it was, but continues to indicate the possibility for a back door cold front on Wednesday to keep temps in northeast MA well below the rest of the region. Confidence is low as to how extensive that impact may be.

Our next low pressure system approaches the Great Lakes by Wednesday which pulls a plume of moisture/cloudcover overhead for mid week which will help to put a damper on temperatures a bit, only in the upper 50s and low 60s. This, ahead of a deep trough for Thursday. Ahead of the main trough a weak shortwave moves through the flow north of SNE Wednesday which may produce some scattered rain showers in the interior, but the more robust precipitation accompanies the cold front on Thursday. This likely falls as rain for most, changing to snow in the high terrain as colder air is pulled in on the back end. There is less certainty with regard to a weaker disturbance passing to our north late Friday into Saturday.

KEY MESSAGE 3...Expecting significant snowmelt over the coming week. Minor river flooding possible.

Elevated temperatures and dewpoints this week will lead to rapid melting of what's left of our snowpack which eventually leads to rises on rivers and streams. Guidance continues to indicate a likelihood of reaching minor flood stage in the CT river valley late next week, and can't rule out several other rivers as well.

AVIATION /10Z 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 in trends with moderate confidence in timing.

Any lingering scattered showers should come to an end by early-mid morning. Otherwise...widespread IFR/LIFR conditions very early this morning will gradually improve today...but this will be a slow process. We do expect most locations northwest of I-95 to improve to VFR by mid afternoon as drier air works into the region. Meanwhile...IFR-LIFR conditions will persist near the south coast and especially the Cape & Islands where fog and areas of drizzle may linger into the afternoon. SW winds will shift to the W and diminish to 6-12 knots later this morning and afternoon. LLWS should also subside this morning as the core of the LLJ departs...but it will still flirt with the Cape and Islands into the afternoon.

Tonight and Monday...High confidence.

Any lingering IFR/LIFR conditions near the Cape/Islands this evening should scour out toward or shortly after after midnight. Otherwise...mainly VFR tonight and Monday. Calm/light SW winds tonight. Winds on Mon will be from the S-SW at 7 to 15 knots.

KBOS Terminal...High confidence in trends and moderate confidence in timing.

KBDL Terminal...High confidence in trends and moderate confidence in timing.

Outlook /Monday through Thursday/...

Monday: VFR. Breezy.

Monday Night through Tuesday Night: VFR.

Wednesday: Mainly VFR, with local IFR possible. Breezy. Slight chance RA.

Wednesday Night: Windy with gusts up to 35 kt. Chance RA.

Thursday: Strong winds with local gusts up to 40 kt. RA likely.

MARINE

Forecaster Confidence Levels...

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

Today through Monday...High confidence.

Lingering SW wind gusts of 20 to 30 knots should diminish this morning as the core of the LLJ departs. However...lingering small craft swell will be slower to diminish but should finally depart all our waters by mid-morning Monday. Will gradually be dropping small craft headlines through that time. Lastly...areas of fog which will be dense at times will be a concern for mariners especially across the southern waters into this evening. Drier air finally works into the entire region after that time bringing an end to the fog.

Outlook /Monday through Thursday/...

Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Patchy fog. Local visibility 1 nm or less.

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

Tuesday through Tuesday Night: Winds less than 25 kt.

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

Wednesday Night: Strong winds with gusts up to 40 kt. Areas of rough seas. Chance of rain.

Thursday: Strong winds with gusts up to 40 kt. Rough seas up to 12 ft. Rain likely.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 10 AM EDT this morning for ANZ231- 234. Small Craft Advisory until 7 PM EDT this evening for ANZ232- 233. Small Craft Advisory until 11 PM EDT this evening for ANZ235- 237. Small Craft Advisory until 10 PM EDT this evening for ANZ250. Small Craft Advisory until 1 PM EDT this afternoon for ANZ251. Small Craft Advisory until 7 AM EDT Monday for ANZ254>256.