textproduct: Boston / Norton

WHAT HAS CHANGED

Sped up exit of rain this morning. Increased rain chances and winds for the late week/weekend storm as confidence increases.

KEY MESSAGES

- After a dry, warmer, and increasingly sunny Monday low clouds and rain showers return Tuesday/Tuesday night with a rumble of thunder possible.

- Drying out Wednesday and especially Thursday under high pressure.

- Next, stronger storm system arrives Friday into Saturday.

DISCUSSION

KEY MESSAGE 1...After a dry and increasingly sunny Monday low clouds and rain showers return Tuesday/Tuesday night with a rumble of thunder possible.

Satellite shows the primary low impacting southern New England spinning south of the islands this morning as it makes its way east. Rain has already come to an end in parts of western MA as the mid level dry slot moves in and this will continue to spread east, shutting off precipitation from west to east by sunrise. A drier atmospheric column makes a brief appearance overhead today as a transient mid level ridge moves through. Thus, can expect clearing skies today with plenty of sun, especially in the afternoon. This ridging also brings a push of warmer air; 925 mb temps rising into the 14-16C range together with full sun should make for high temperatures 10-15 degrees warmer than Sunday, in the low 70s.

Monday night things change as a low center over the Great Lakes approaches while high pressure sits over Nova Scotia. This initially turns surface flow out of the northeast advecting cooler, saturated air onshore making for low clouds with patchy drizzle to start Tuesday. This brings highs back into the 60s. The warm front lifts north Tuesday afternoon bringing scattered rain showers which continue until the cold front drops through sometime Wednesday. SNE will be socked in with clouds all of Tuesday and Tuesday night as moisture remains trapped under a strong inversion. Could even see some rumbles of thunder given some weak elevated instability above that inversion. Elevated dewpoints will also lead to mild lows, in the upper 50s and low 60s.

KEY MESSAGE 2...Drying out Wednesday and especially Thursday under high pressure.

Wednesday things begin to dry out behind the cold front and the inversion mixes out allowing for a mix of clouds and sun. However, a stronger reinforcing cold front brings a much cooler and drier airmass for Thursday as high pressure arrives. 925mb temps drop to near 6C leading to highs only in the low 60s under mostly sunny skies.

KEY MESSAGE 3...Next storm system arrives Friday into Saturday.

Our next storm, this one likely stronger than the mid week system, originates out west Thursday. A low forms in the lee of the Rockies, phasing with another low over the Great Lakes as it is swept east by a northern stream trough. It then strengthens as it moves over or near New England Friday into Saturday. This pulls a lot of moisture into the region and with good dynamics including potential for a strong 45-55kt LLJ and favorable placement beneath the RRQ of a 160kt upper jet, we should see a windy and very rainy Friday- Saturday. Timing and other details are uncertain at this time, but confidence in at least a decently strong weather system is increasing.

AVIATION /06Z MONDAY THROUGH FRIDAY/

Forecaster Confidence Levels...

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

06Z update...

Through 12Z: High confidence.

RA comes to an end by 12Z.

Monday: High confidence.

N winds 5-10 kts. IFR cigs to start, lifting to VFR from west to east after 12Z (western MA/CT) to 19Z (Cape Cod and Islands).

Monday night: High confidence.

Light winds increasing and becoming NE 5-10 kts toward 12Z. Scattered SHRA/DZ moves in with IFR/MVFR.

Tuesday: High confidence.

IFR/MVFR. E winds becoming S 5-10kts in scattered SHRA.

KBOS Terminal...High confidence in trends, moderate confidence in timing. Biggest question will be how quickly RA ends and cigs lift..most likely rain ending by 11Z and VFR by 15z.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Mainly VFR, with local IFR possible. Breezy. Chance SHRA, slight chance TSRA.

Wednesday through Thursday: VFR. Breezy.

Thursday Night: VFR. Chance SHRA.

Friday: VFR. Windy with local gusts up to 30 kt. SHRA.

MARINE

Forecaster Confidence Levels...

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

Through Monday: High confidence.

The remnants of Hurricane Isaias are currently working their way across the southern waters. Seas 5 to 10 ft and wind gusts 20 to 25 knots. SCAs are in effect for the southern waters, 15-20 kts with gusts to 25kt possible, especially on the southern outer waters. Seas 6-9 ft on southern waters, 3-6 ft on the eastern waters.

Monday night: High confidence.

NE winds 10-15 kts with gusts 20-25 kts on the eastern waters. Seas 3-5 ft.

Tuesday: High confidence.

SE winds 10-15 kts with increasing gusts to 20 kts. Seas 3-5 ft. RA over the eastern waters.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers, slight chance of thunderstorms.

Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas.

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

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

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

Friday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Rain showers likely, slight chance of thunderstorms.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ235- 237. Small Craft Advisory from 8 PM this evening to 2 AM EDT Wednesday for ANZ250. Small Craft Advisory until 8 PM EDT Wednesday for ANZ254. Small Craft Advisory until 8 AM EDT Tuesday for ANZ255-256.