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 /18Z WEDNESDAY THROUGH MONDAY/

Forecaster Confidence Levels...

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

18z TAF Update...

This afternoon through Thursday night...High confidence in trends with moderate confidence in timing.

MVFR ceilings may linger into the late afternoon hours...But most locations improve to VFR conditions this evening outside of any brief precipitation in the 02z to 08z window with a cold frontal passage. A line of snow showers with a few heavier snow squalls possible will drop into northwest MA after 02z. If the activity survives it may approach the I-95 corridor in the 05z to 07z window and quickly exit the coast. This activity will result in briefly lower cigs/vsbys. Otherwise...VFR conditions behind this activity right through Thu night. Southwest wind gusts of 15 to 25 knots diminish early this evening but expect a period of LLWS ahead of an approaching cold front. Otherwise...west winds 7 to 13 knots on Thu. Winds then become light NW Thu night and should decouple in the typical spots.

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

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

Outlook /Friday through Sunday/...

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.