textproduct: Boston / Norton

WHAT HAS CHANGED

Coastal Flood Warning issued for the east coast of Massachusetts for minor coastal flooding with pockets of moderate flooding possible along with prolonged beach erosion. A Coastal Flood Advisory was issued for the south coast of Rhode Island and Massachusetts for minor coastal flooding and splashover.

KEY MESSAGES

- A strong Nor'easter will bring a prolonged period of rain, rough seas, strong winds, and coastal flooding/beach erosion starting today and continuing through the weekend.

- High pressure returns toward the middle of next week.

DISCUSSION

KEY MESSAGE 1...A strong Nor'easter will bring a prolonged period of rain, rough seas, strong winds, and coastal flooding/beach erosion starting today and continuing through the weekend.

Our much anticipated nor'easter is on our doorstep this morning, expected to bring increasingly gusty winds through the day ahead of a prolonged stretch of wet and windy conditions through the weekend. Nighttime microphysics satellite imagery early this morning shows the disturbance sitting off the coast of the Carolinas and sending moisture out ahead of it which will lead to increasingly cloudy skies as clouds thicken and lower today. The combination of this very moist airmass (PWATs 1.5"+), strong dynamics associated with the deepening surface low pressure moving up the east coast, and our placement between it and a strong high pressure to our north will be the ingredients for an early season nor'easter. This will be exacerbated by the duration of the storm as it struggles to escape, being pulled back west toward New Jersey Saturday into Sunday.

The first concern is for strong to damaging northeast winds as the pressure gradient tightens and a 55-65 kt LLJ shifts overhead NW of the low center. Despite a westward shift in the track over the last few days, the strongest winds are still expected to be experienced along the coast, especially Cape Cod and the islands. Here, maximum wind gusts will be in the 45 to 55 mph range with 60 mph gusts possible at times, especially Friday night through Saturday morning. Further inland, 30-45 mph gusts are more likely. Regardless, the timing of this storm before trees have lost their leaves will exacerbate impact from broken limbs and increase the potential for power outages. Strong winds will continue through Sunday but won't be as strong as the storm weakens.

As for coastal flooding, the greatest concern is for the east coast of MA (especially south of Boston) where a few factors are at play. First, we've already dealt with days of gusty NE winds and this will continue through Sunday, increasing in magnitude shortly. This has steadily increased nearshore wave heights which will help contribute to beach erosion. Finally, astronomical tides are increasing each day, so it will take less and less to see minor flooding impacts. This being a long duration event (spanning several high tide cycles Friday night-Sunday) will not do us any favors either; in these situations water often has trouble evacuating fully at low tide, further contributing to high water levels. A Coastal Flood Warning has been issued for the east coast of MA for a combination of minor flooding with pockets of moderate, as well as expected widespread beach erosion. Additionally, a Coastal Flood Advisory has been issued for the south coast of Massachusetts and Rhode Island where minor coastal flooding is possible due to high seas just offshore and increasing swell.

Finally, this system will dump a lot of rain over the next 72 hours, on the order of 3-5 inches thanks to the impressive moisture and dynamics given those previously mentioned PWATs and 925mb jet along with convergence at the surface as winds turn from the SE to E to NE around the low. Latest ensemble probabilities continue to indicate the heaviest rainfall over eastern MA and RI. Flooding concerns will be mitigated by the long duration of the event, though pockets of urban and poor drainage flooding are possible.

KEY MESSAGE 2...High pressure returns toward the middle of next week.

When will we finally get a break from the unsettled weather? It looks like it may be a slow improvement as the upper cutoff low isn't pulled into the steering flow and out of New England until closer to Tuesday. Thus, while we won't see the wind and rain that we saw over the weekend to start the work week, it will still be wet and unsettled. By Tuesday into mid week signs point to the return of mid level ridging and surface high pressure for a time.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

Forecaster Confidence Levels...

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

06z TAF Update...

Through 12Z...High confidence.

VFR, outside of some areas of MVFR cigs over portions of southeast MA, especially towards ACK and the Cape tonight. Cigs there may periodically break to VFR, though the lingering low clouds may stick around through the early morning hours. NE winds of 10 to 20 kt with gusts of 20 to 30 kt, strongest towards the southeast New England coast. Gusts as high as 35 kt for Nantucket.

Friday...High confidence.

VFR most of the day, with MVFR cigs moving in from the southeast, impacting ACK as early as 17z and FMH/HYA by 20z. Lowered cigs come following -RA/RA moving in throughout the day from SE to NW. Strong NE winds, 15-25 kts with gusts 30-45 kts, strongest over southeast MA terminals.

Friday Night...High confidence in trends. Moderate confidence in timing.

MVFR further overspreads the region from SE to NW. Local IFR possible towards the Cape and Islands late. Strong NE winds continue and increase in intensity, generally sustained between 10-20 kt inland and 25-35 kt towards SE MA, Cape Cod, and the Islands. Gusts to 55 kt are possible for this area as well, with gusts to 35-40 kt possible over the interior.

Saturday...Moderate confidence in trends and timing.

MVFR at most terminals lowering to lower end MVFR or IFR near or shortly before 12Z for Cape Cod and island terminals, spreading NW through the day in widespread RA. Strong NE winds continue, generally sustained between 10-20 kt inland and 25-30 kt towards SE MA, Cape Cod, and the Islands. Gusts to 55 kt are possible for this area as well, with gusts to 35-40 kt possible over the interior.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Saturday Night through Tuesday/...

Saturday Night: MVFR/IFR conditions possible. Strong winds with gusts up to 50 kt. RA.

Sunday: MVFR/IFR conditions possible. Strong winds with gusts up to 45 kt. RA, slight chance TSRA.

Sunday Night: MVFR/IFR conditions possible. Windy with gusts up to 35 kt. RA, slight chance TSRA.

Monday: MVFR/IFR conditions possible. Windy with local gusts up to 30 kt. SHRA likely, RA likely, slight chance TSRA.

Monday Night: Mainly VFR, with local IFR possible. Breezy. Chance SHRA.

Tuesday: VFR. Slight chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Tonight through the Weekend...High confidence.

* Dangerous conditions for Mariners Fri into the weekend with NE wind gusts of 45 to 60 knots and seas offshore of 15-25 feet.

An early season Nor'easter will combined with high pressure over Quebec to result in strong NE wind gusts of 45-60 knots and seas offshore building to between 15 and 25 feet late Fri into the weekend. Storm Warnings have been issued for all waters. This is a dangerous storm for mariners with the worst conditions later Fri into Sun. Mariners should consider returning to port as soon as possible. NE winds will persist Mon too...so although conditions will improve this process will be quite slow.

Outlook /Saturday Night through Tuesday/...

Saturday Night: Low risk for storm force winds with gusts up to 50 kt. Rough seas up to 16 ft. Rain, slight chance of thunderstorms. Local visibility 1 to 3 nm.

Sunday: Moderate risk for gale force winds with gusts up to 45 kt. Rough seas up to 12 ft. Rain, slight chance of thunderstorms.

Sunday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 10 ft. Rain, slight chance of thunderstorms.

Monday: Low risk for Small Craft Advisory winds with local gusts up to 30 kt. Rough seas up to 9 ft. Chance of rain showers, chance of rain, slight chance of thunderstorms.

Monday Night: Winds less than 25 kt. Areas of rough seas. Chance of rain showers, slight chance of thunderstorms.

Tuesday: Winds less than 25 kt. Areas of rough seas. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...Wind Advisory from noon today to 2 AM EDT Sunday for CTZ002>004. MA...Wind Advisory from noon today to 2 AM EDT Sunday for MAZ004- 011-026. Wind Advisory from 8 AM this morning to 2 AM EDT Sunday for MAZ005-006-012>014-017-018. High Surf Advisory until 8 PM EDT Sunday for MAZ007-015-016- 019-022>024. High Wind Warning from 8 AM this morning to 2 AM EDT Sunday for MAZ007-015-016-019>024. Coastal Flood Warning from 5 PM this afternoon to 8 PM EDT Sunday for MAZ007-015-016-019-022>024. Coastal Flood Advisory from 5 PM this afternoon to 8 PM EDT Sunday for MAZ020-021. RI...Wind Advisory from 8 AM this morning to 2 AM EDT Sunday for RIZ001. High Wind Warning from 8 AM this morning to 2 AM EDT Sunday for RIZ002>008. Coastal Flood Advisory from 5 PM this afternoon to 8 PM EDT Sunday for RIZ006>008. MARINE...Storm Warning from 2 PM this afternoon to 8 PM EDT Saturday for ANZ230-236. Storm Warning from 8 AM this morning to 8 PM EDT Saturday for ANZ231-254-281. Storm Warning until 8 PM EDT Saturday for ANZ232>235-237-255- 256-282-283. Storm Warning from 11 AM this morning to 8 PM EDT Saturday for ANZ250-251-280.