textproduct: Boston / Norton

WHAT HAS CHANGED

No changes to the snowfall forecast this morning. Guidance continues to trend the coastal low Thursday night further offshore.

KEY MESSAGES

- A quick burst of snow this morning will bring 1-3 inches of snow

- Near normal temperatures Thursday and Friday with a weak coastal storm continuing to trend further offshore.

- Potential for another Arctic outbreak late in the weekend into early next week

DISCUSSION

Key Message 1...A quick burst of snow this morning will bring 1-3 inches of snow

A weak shortwave and clipper low-pressure system moves through the region this morning, bringing a quick burst of snow. A southerly LLJ will bring modest WAA and lift into the snow growth region this morning. Moisture, however, is limited, with PWATS only around 0.4 to 0.5 inches, leading to QPF under a quarter of an inch across the region. The area that could see higher QPF is along the immediate south coast, where southward winds may advect higher moisture content onshore. Guidance remained consistent overnight, bringing a fairly widespread 1-3 inches of snow across the region, except for the Cape and Islands, where temperatures will likely turn snow to rain later this morning. Snow will fall over a relatively short period, likely in a 3-hour or less period, which will lead to some more intense snow rates in the 0.5 to 1 inch per hour range. These rates are high enough to make travel conditions hazardous this morning. Snow will move in from west to east this morning between 5 am and 8 am, and move out to sea between 11 am and 2 pm. Clouds are unlikely to clear after the snow moves offshore, but southerly winds and WAA will help temperatures rebound into the mid to upper 30s after a chilly start to the day. There could be a round of widely scattered rain/snow showers this evening as a secondary shortwave and subtle cold front moves through.

Key Message 2...Near normal temperatures Thursday and Friday with a weak coastal storm continuing to trend further offshore.

The Northeast remains in a general troughing pattern through the end of the week, which will keep temperatures near normal for this time of year, near 40F. Less windy and fewer clouds both Thursday and Friday with partial sunshine. Guidance continues to trend the coastal storm offshore on Thursday night, but a coating to 2 inches remains possible for the Cape and Islands. A moisture-starved warm front arrives early Saturday morning, bringing temperatures into the mid to upper 40s away from the high terrain and coasts.

Key Message 3...Potential for another Arctic outbreak late in the weekend into early next week

Some early indications that the polar vortex makes another trip down into the eastern Great Lakes and Northeast by the end of the weekend and into early next week. Temperatures will likely be well below normal with highs in the 20s and lows in the single digits to low teens. The one factor that will keep this arctic outbreak from becoming dangerously cold is that we are only about a month away from the spring equinox, meaning the sun angle will help keep temps warmer then previous arctic outbreaks in January. Precipitation remains highly uncertain at this range with enormous spread in both deterministic and ensemble guidance.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

Today: High Confidence on snow, Moderate Confidence on CIGS

Snow will move in from west to east this morning, brining a brief 3-4 hour period of light, possibly moderate snow between 12-18z. low end MVFR/IFR CIGS will lag the snow by about 30 to 60 mins as the boundary layer gradually saturates. Visibility in snow should be in the 1-2SM range. Cape and Island terminals likely remain rain with rain lasting later into the afternoon.

Southerly LLJ moves in from west to east with the snow which will bring LLWS concerns with 35-40 knots at 2kft from the S while surface winds across the region remain S around 10 knots.

Snow and wind shear concerns end early this afternoon, but IFR/MVFR CIGS likely linger until low-mid level westerlies can clear out some of the clouds and low level moisture.

Tonight: Moderate Confidence

CIGS gradually improve to VFR tonight, but before then, there could widley scattered rain/snow showers from roughly 00z-08z. Winds aloft increase from the WSW at 35-45 knots, but the nocturnal inversion will leave surface winds under 10 knots leading to continued wind shear concerns.

Tomorrow: High Confidence

VFR. Light westerly winds.

KBOS Terminal...Moderate confidence in TAF.

Snow reaches the terminal around 14z with low end MVFR/IFR CIGS following shortly after. Gusty southerly winds expected later this morning into the afternoon with gusts up to 25 knots.

KBDL Terminal...Moderate confidence in TAF.

Snow reaches the terminal around 12z with low end MVFR CIGS following shortly behind. Light southerly winds with LLWS today.

Outlook /Thursday through Sunday/...

Thursday: VFR. Breezy. Slight chance FZRA, slight chance SN.

Thursday Night: VFR. Slight chance FZRA, slight chance SN.

Friday: VFR.

Friday Night through Saturday: VFR. Breezy.

Saturday Night: VFR.

Sunday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

Small Craft Advisories have been issued for all waters this morning for a period of SW gusts to 25-30 kt as a low level jet moves across the waters. Winds will diminish Wed evening but 5-8 ft seas will linger over southern waters through Wed night. Vsbys lower this morning in a period of snow and rain.

Outlook /Thursday through Sunday/...

Thursday: Winds less than 25 kt. Local rough seas. Slight chance of rain, slight chance of freezing rain, slight chance of snow.

Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of snow.

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

Saturday through Sunday: Winds less than 25 kt.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 4 PM EST this afternoon for ANZ230. Small Craft Advisory until 7 PM EST this evening for ANZ231- 236-251. Small Craft Advisory until 1 AM EST Thursday for ANZ232>234. Small Craft Advisory until 7 PM EST Thursday for ANZ235-237- 254>256. Small Craft Advisory until 10 PM EST this evening for ANZ250.