textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes in the forecast for the ongoing Nor'easter.

KEY MESSAGES

- Strong/long duration Nor'easter will continue to bring damaging wind gusts, coastal flooding/beach erosion, and periods of heavy rain through the weekend. Rain and gusty winds persist into Monday. - One final day of wet and unsettled weather Tuesday before a warming and drying trend arrives next week.

DISCUSSION

KEY MESSAGE 1...Strong/long duration Nor'easter will continue to bring damaging wind gusts, coastal flooding/beach erosion, and periods of heavy rain through the weekend. Rain and gusty winds persist into Monday.

What's there to be said about the ongoing early season nor'easter that hasn't been said already...not much! Things are playing out largely as expected so far...OPC surface analysis indicates the 996mb surface low spinning well to our south. It's on its way north, slowly, before it makes a sharp westward turn into New Jersey tonight/tomorrow. So far we've already seen some minor coastal flooding on Nantucket where ~2 feet of storm surge pushed water levels into minor flood stage during the overnight high tide. The area of most concern continues to be the east coast of MA, especially south of Boston, where a several factors are at play. These include the long duration of the winds and long NE fetch, inability for water to fully recede between high tides, and the steadily rising astronomical tides. A Coastal Flood Warning remains in effect for these east facing locations where the greatest concern will be the Saturday afternoon and overnight high tides, though we'll be flirting with minor flooding through Sunday. A Coastal Flood Advisory is in effect for the south coast of Massachusetts and Rhode Island where more sporadic minor coastal flooding is possible due to high surf just offshore and increasing swells.

Winds have increased as expected, with widespread gusts of 45 to 55 mph observed from Cape Cod and the islands to coastal Rhode Island while several coastal stations have reported gusts 60+ mph. This occurred as the core of a 65kt LLJ moved overhead tonight and this continues to lift north and west (weakening) through Saturday and Sunday. That is why timing of the strongest wind gusts won't be identical for everyone...more likely later Saturday into Sunday for northeast MA for example. Regardless, northeast winds will be relentlessly gusty through Sunday, gusting 35-45 mph for most inland locations and as high as 45-55 mph along the coast at times. The timing of this storm before trees have lost their leaves will exacerbate impacts 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. Even so, even Monday will be breezy and wet.

This system will dump a lot of rain over the next 72 hours thanks to the impressive moisture and dynamics...anomalous PWATs and the previously mentioned 925mb jet along with orographic lift into the higher terrain. Rainfall totals of 3-5" are expected. The best chance at these higher amounts is along the coasts and the east slopes of the CT hills, Worcester hills. Flood risk will be mitigated by the long duration of the event, though pockets of urban and poor drainage flooding are possible.

KEY MESSAGE 2...One final day of wet and unsettled weather Tuesday before a warming and drying trend arrives next week.

The first part of the extended forecast features lingering effects from our decaying nor'easter as the upper level low will be slow to exit. 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 afternoon guidance shows gradual clearing from SW to NE with even some breaks of sunshine possible later in the afternoon! By Wednesday, the upper air pattern begins to change as a ridge builds over the eastern CONUS. By Thursday, 500mb heights build to 582dm and seems to persist through at least the end of the week across ensemble guidance. Closer to the surface, 850 mb temperature anomalies soar to +6-10C above climo through late week. At the surface this translates to a period of late-summer like warmth with highs in the upper 70s to perhaps low 80s inland. Outside of Tuesday, the only chance for any precipitation arrives later Thursday into Friday as a weakening shortwave approaches the region from the west.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

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 in trends. Moderate confidence in timing.

VFR for most terminals early, then MVFR further overspreads the region from SE to NW. MVFR reaches Boston around 10z. Local IFR possible toward the Cape and Islands after 09z. Strong NE winds continue and increase in intensity, generally sustained at 10-20 kt inland and 25-35 kt toward SE MA, Cape Cod, and the Islands. Gusts to 50 kt are possible in these areas, with gusts of 35-40 kt possible over the interior.

Saturday...Moderate confidence in trends and timing.

MVFR at most terminals, lowering to low-end MVFR or IFR near or shortly before 12Z at Cape Cod and Island terminals, then spreading NW through the day with widespread RA. Strong NE winds continue, generally sustained at 10-20 kt inland and 25-30 kt toward SE MA, Cape Cod, and the Islands. Gusts to 50 kt are possible in these areas, with gusts of 35-40 kt possible over the interior.

Saturday Night...Moderate confidence in trends and timing.

MVFR possible at BDL but elsewhere expect IFR in widespread RA. Localized LIFR possible at ORH, HYA, FMH, and ACK. Strong NE winds at 15-25 kt with gusts of 30-40 kt. Localized higher gusts to 45 kt are possible near the coast.

Sunday...Moderate confidence.

MVFR possible at BDL but IFR likely elsewhere in widespread RA. Localized LIFR possible especially at OHR, HYA, FMH, and ACK.

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

VFR, becoming MVFR after 11Z. Widespread rain continues off and on through the TAF period. Persistent NNE to NE winds at 20-25 kt with gusts of 30-45 kt at times.

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

Outlook /Sunday Night through Wednesday/...

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

Monday: MVFR/IFR conditions possible. Windy with local gusts up to 30 kt. SHRA.

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

Tuesday: Mainly VFR, with local IFR possible.

Tuesday Night through Wednesday: VFR.

MARINE

Forecaster Confidence Levels...

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

Through the Weekend...

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

The strengthening early season Nor'easter will bring strong NE wind gusts of 45-60 knots and seas offshore building to between 15 and 25 feet. The strongest of the winds/seas will be early this morning and peak Sat into Sat night...but seas will remain quite high Sun into Mon along with NE wind gusts of 25 to 40 knots persisting. Storm Warnings continue for all the waters.

Outlook /Sunday Night through Wednesday/...

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

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

Monday Night: Winds less than 25 kt. Rough seas up to 8 ft. Chance of rain showers.

Tuesday: Winds less than 25 kt. Areas of rough seas.

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

Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft.

BOX WATCHES/WARNINGS/ADVISORIES

CT...Wind Advisory until 8 AM EDT Sunday for CTZ002>004. MA...Wind Advisory until 8 AM EDT Sunday for MAZ004>006-011>014-017- 018-026. High Wind Warning until 8 AM EDT Sunday for MAZ007-015-016- 019>024. High Surf Advisory until 8 PM EDT Sunday for MAZ007-015-016- 019-022>024. Coastal Flood Warning until 8 PM EDT Sunday for MAZ007-015-016- 019-022>024. Coastal Flood Advisory until 8 PM EDT Sunday for MAZ020-021. RI...Wind Advisory until 8 AM EDT Sunday for RIZ001. High Wind Warning until 8 AM EDT Sunday for RIZ002>008. Coastal Flood Advisory until 8 PM EDT Sunday for RIZ002- 004>008. MARINE...Storm Warning until 8 PM EDT this evening for ANZ230>234-236- 250-251-254-255-280>282. Storm Warning until 2 AM EDT Sunday for ANZ235-237-256-283.