textproduct: Boston / Norton

WHAT HAS CHANGED

No signficant changes.

KEY MESSAGES

- Widespread rainfall Thu into Fri, cooling down Friday before the weekend's warm-up.

- Dry with well above normal temperatures Saturday through the middle of next week.

DISCUSSION

KEY MESSAGE 1...Widespread rainfall Thu into Fri, cooling down Friday before the weekend's warm-up.

Southern New England is situated between high pressure over the western Atlantic and a 1004mb low pressure center over the great Lakes. The warm front extending from that low is making its way north through New England this afternoon and led to light showers out ahead earlier this afternoon. These have cleared and we expect that to remain the case the rest of the day as some marginally drier air moves in in the 850-600mb layer and a lack of much forcing behind the front. Otherwise, breezy conditions the rest of the day as the well mixed BL taps into a 35-40 kt 850mb jet overhead.

As the upper level low digs into the southeast it sets us up for a cool and wet Thursday (lingering into Friday thanks to the amplified, slowly evolving pattern). This places SNE beneath a plume of anomolous moisture (PWATs over 1" are in the 99th percentile of climatology). Together with strong synoptic forcing from strong PVA, favorable placement beneath a 300mb jet, and convergence in the mid levels most locations in the region can expect 1 to 2 inches of rain before all is said and done. Rain arrives in western SNE Thursday morning, overspreading the region through the day and ending in the early overnight hours. There may be two bullseyes of highest rain totals, one over the western MA/CT high terrain thanks to upslope flow, and another over eastern MA associated with a secondary low that looks to form between the parent low to our NW and another disturbance passing by over the Atlantic. Fortunately, given the prolonged nature of the rain, not expecting flooding to be a concern. Finally, dewpoints may reach the low to mid 50s Thursday afternoon contributing to several hundred J/kg of elevated CAPE, so may have some embedded thunderstorms as well.

Friday will be drier as the surface low slowly moves east but the upper low lingers overhead. This turns winds out of the northeast while low level moisture remains locked in. So, expect a cool, cloudy, day with off and on light rain/drizzle; more likely to remain dry the further west you go. The upper level airmass doesn't change much, so expecting high temperatures for the western half of the region to be similar to Thursday, in the upper 50s (high elevation) to low 60s (CT Valley). The difference will be felt in eastern MA and RI where that onshore flow will drop high temperatures from the low/mid 60s Thursday to the upper 50s on Friday. This is approaching 10 degrees cooler than normal.

KEY MESSAGE 2...Dry with well above normal temperatures Saturday through the middle of next week.

A persistent ridge sets up over the east CONUS on Saturday and remains quasi-stationary through the middle of next week. This will support a persistent area of high pressure off the southeast that will advect warm, moist air into southern New England for several days. Expect several consecutive days with high temperatures in the 70s for much of southern New England, with low to mid 80s possible on Tuesday and Wednesday. Low temps forecast to be mainly in the 50s during this stretch. Overall a warm,dry, and quiet stretch of weather between Saturday and the middle of next week.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Forecaster Confidence Levels...

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

00Z TAF Update:

Tonight...High confidence.

VFR cigs to start then becoming MVFR/IFR after 08Z from west to east. Few showers are possible in west/central southern new england after 06Z. As surface winds slacken after 00Z, marginal LLWS possible given modest low level SW jet of 35-40 kt.

Thursday...High confidence on trends but some uncertainty on exact timing of details.

MVFR/IFR with periods of rain, moderate to heavy at times. 20-25% probability of -TSRA in embedded heavier showers. ESE winds at 8-12 kts with a occasional gust up to 20 kts.

Thursday night...High confidence.

IFR/LIFR cigs. Widespread moderate to heavy rain ends but light rain/drizzle continues. Winds light NE.

KBOS...High confidence.

KBDL...High confidence.

Outlook /Friday through Monday/...

Friday: Mainly VFR, with areas IFR possible. SHRA likely.

Friday Night: VFR.

Saturday through Sunday: VFR. Breezy.

Sunday Night through Monday: VFR.

MARINE

Forecaster Confidence Levels...

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

2 AM update...

Today through Thursday...High confidence.

Strengthening low level SW jet moves across SNE today, with light SW early this morning, becoming south and increasing to 20-25 kt this afternoon, except 25-30 kt in gusts near shore. Hence, SCA remains posted. Other than a spot morning shower across northern MA waters, dry weather and good vsby prevail today. South winds slacken tonight with mainly dry weather. Rough conditions Thu, with S-SE winds 20-25 kt in the morning, then slacken in the afternoon and become east as low pressure tracks south of New England. This low will bring widespread rain to region Thu, moderate to heavy at times with reduced vsby.

Outlook /Friday through Monday/...

Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers.

Friday Night: Winds less than 25 kt. Seas up to 5 ft.

Saturday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft.

Saturday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft.

Sunday through Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ230>237-250-251-254>256.