textproduct: Caribou

WHAT HAS CHANGED

- Winter Storm Warning been cancelled, Winter Weather Advisories cancelled with precipitation tapering to snow showers.

- Raised winds and gusts for Thursday afternoon and added patchy blowing snow for the open agricultural areas in Northern Maine and lakes/ponds CWA wide due to recreational purposes.

- It appears there could be multiple rounds of snow showers from late Friday night into Saturday night, vice just a single round.

- It looks like the system for Monday night/Tuesday should most likely impact only eastern areas - with the best chance over eastern Downeast Maine.

KEY MESSAGES

1) Light snow will impact travel into the evening, especially areas closer to New Brunswick border. Gusty winds on Thursday will lead to patchy blowing and drifting of the new snow.

2) Heavy snow showers possible across mostly northern areas From late Friday night through Saturday night which could create sudden drops in visibility.

3) There is the potential for a coastal low to bring snow mainly to Eastern Maine Monday night and Tuesday. This could impact the morning commute there.

4) Widespread snow across the North and rain and/or snow elsewhere is possible Wednesday. This could impact the afternoon commute.

DISCUSSION

KEY MESSAGE 1... Light snow will impact travel into the evening, especially areas closer to New Brunswick border. Gusty winds on Thursday will lead to patchy blowing and drifting of the new snow.

KEY MESSAGE 1 DESCRIPTION... Area of light snow extends over the eastern half of the CWA closer to the New Brunswick border, cannot rule out briefly moderate snow. Elsewhere, generally scattered snow showers within an area of drier air trapped with the 500mb low drifting east-southeast. This afternoon into the evening expecting the surface low to extend back an semi-inverted trof over the Downeast into portions of Aroostook County associated with 500mb shortwave energy. Will continue periods of light snow across portions of the CWA into the evening. Have adjusted the winter weather headlines based on the trends where snow will continue to fall and cause slippery travel. Additional snowfall of 1-3 inches with locally higher amounts are possible. Tonight expecting steady precip to taper to isolated/scattered snow showers with potential of an additional dusting.

Tomorrow the surface low deepens in the Maritimes with a 1028mb surface high pushing over Lake Superior. The pressure gradient will tighten and winds 1-2kft AGL increase to 20-30kt and the boundary layer will mix up to about 2kft. Expecting NW winds to increase with daytime heating so expecting gusts 20-30mph during the day. This will lead to patchy blowing snow across the open fields of Northern Maine and on the lakes/ponds for those heading out to ice fish or snowmobile.

KEY MESSAGE 2... Heavy snow showers possible across mostly northern areas from late Friday night through Saturday night which could create sudden drops in visibility.

KEY MESSAGE 2 DESCRIPTION... Models still differ on how they handle a closed 850-500mb low that starts out E to NE of James Bay at 12z Friday, remains nearly stationary there during the day on Friday, then dives ESE to SE (depending on model) Friday night, then either continues SE or turns E on Saturday and Saturday night, then exits into the Maritimes on Sunday. The high resolution NAM and CMC-Reg, along with the CMC-Global take a more southern track with this system and bring the closed low over Maine Saturday night, while the GFS and ECMWF keep the center of the closed low north of Maine. Given the good track record of the CMC with similar systems, leaned toward it with this system, blending in CMC Pops and QPF, along with ConsRaw, with the NBM. For now given the uncertainty, did limit pops to at most chance. The results are fairly consistent with DESI showing generally a 50 percent chance or more of at least 0.1" of snow across most of the North from 7am Saturday-7am Sunday.

It appears mid level lapse rates should be fairly unstable around 7-7.5C/km, this coupled with strong differential positive vorticity advection, should support some stronger convection. Areas under any stronger snow showers could receive a quick inch or so, otherwise any accumulation should be less than an inch from any given snow shower. Areas receiving multiple snow showers could see a few inches of snow, but likely less than advisory levels.

Another concern is the potential for gusty winds, but for now there is quite a bit of uncertainty if they could be strong enough to reach snow squall criteria (more likely to be less than 30 mph than above 30 mph).

Note, if the more northern track of the closed low in the GFS/ECMWF and some ensemble members is correct - then there likely will not be sufficient forcing and instability for anything other than light snow showers, assuming there is even enough lift to over come the limited moisture that will be available with this system. So little or no snowfall remains a possibility, though for now there seems to be less of a chance for that to occur, especially across the North.

KEY MESSAGE 3... There is the potential for a coastal low to bring snow mainly to Eastern Maine Monday night and Tuesday. This could impact the morning commute there.

KEY MESSAGE 3 DESCRIPTION... Solutions for the system for early next week have shifted south and east, in response to ridging in the wake of the system exiting into the Maritimes this weekend limiting the northern extent of this system. So the extent of snow showers this weekend, will have a bearing on how far north the next system gets. The more extensive the coverage of snow showers, the farther south this second system will go.

Based on this, there is the chance for snow across mainly Eastern Maine from late Monday through Tuesday, and possibly lingering into Tuesday night over far SE Maine. Given that more guidance than not is suggesting the storm either misses completely or only brings snow just to the immediate coast, this is not considered to be a likely threat at this time.

KEY MESSAGE 4... Widespread snow across the North and rain and/or snow elsewhere is possible Wednesday. This could impact the afternoon commute.

KEY MESSAGE 4 DESCRIPTION... There are model differences on the exact timing and strength of the closed, strong upper low progged to pass to the North. Some solutions are slower to bring in the storm, and a few shunting it to the south. The largest cluster of solutions though brings a widespread snow across the North with Rain and/or snow farther south by Wednesday afternoon. This system should be fairly quick moving, limiting any total accumulations.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Rest of Today...IFR north, MVFR/IFR south. -SN north and VCSH/-SHSN south. Light and variable winds generally less than 10kt.

Tonight...IFR north and MVFR south. -SN possible becoming VCSH/-SHSN. Cigs turning MVFR areawide. Light and variable winds.

Thursday...MVFR early becoming low end VFR. NW winds 10-15kt gusting 20-30kt.

Thursday night: VFR. NW winds 10-15kt gusting 20-30kt.

Friday-Friday evening: VFR. NW winds G15-20KT possible Friday/Friday evening.

Late Friday night-Saturday night: Most likely VFR at southern terminals. MVFR or lower possible at northern terminals in any stronger snow showers. Some northern terminals could experience multiple rounds of snow showers during this time frame. NW winds G15-20KT possible late Saturday

Sunday-Sunday night: VFR, except for MVFR possible early at northern terminals.

Monday: VFR, with possible exception of low chance of MVFR or lower late at southern terminals.

MARINE

Small Craft Advisory has been hoisted for the Coastal Waters from 4PM this afternoon to 7AM Friday. N winds 15-25kt gusting up to 30kt. Seas 3-5ft. For the Intra-Coastal Waters a Small Craft Advisory has been hoisted from 1AM Thursday till 7AM Friday. NW winds 10-20kt with gusts up to 25kt expected.

The SCA could need to be extended on all waters through Friday, with SCA conditions possibly lingering on the coastal ocean waters Friday night. For now it appears that all waters should see sub-SCA conditions from Saturday-Sunday night. SCA conditions are possible on the coastal ocean waters on Monday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory until 7 AM EST Friday for ANZ050-051. Small Craft Advisory from 1 AM Thursday to 7 AM EST Friday for ANZ052.