textproduct: Caribou

SYNOPSIS

Low pressure off the coast will pull away to the southeast today as high pressure builds over the region. A small area of low pressure will cross the north Christmas morning followed by high pressure building in Thursday night into Friday. High pressure will remain over the area Saturday into Sunday followed by low pressure on Monday.

NEAR TERM /THROUGH THURSDAY/

The low off the coast which has produced a concentrated area of moderate to heavy snow in an inverted trough over the Midcoast region will pull away to the southeast today as the trough drops to the south. This will allow any lingering snow to taper off this morning followed by partial clearing late today as high pressure builds over.

High pressure will remain over the area tonight. The evening will begin partly cloudy then clouds will then increase late tonight ahead of a shortwave trough dropping down from the northwest. This trough will support a small low tracking across the northern parts of our region Christmas morning and continuing down to the southeast during the afternoon. This will bring some light snow over the north through the morning with up to 2 inches possible over much of the region and slightly less to the west. Christmas afternoon will remain mostly cloudy with some snow showers across the north. A northwest wind will increase late Thursday as the gradient tightens behind departing low pressure and ahead of high pressure building in from the west. This may produce some patchy blowing snow over open areas late in the day.

SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/

Key Message... 1) Strong northwest winds will produce wind chill temps down around 20 below zero across the north Friday morning 2) Temps on Friday night to drop below zero across the north

Key Message 1... Cold arctic air will plunge into the area in the wake of a cold frontal passage on Thursday. Min temps will drop to near zero acrs the north, with below zero temps over the North Woods. H9 temps toward -22C in this area by Friday morning. H9 winds between 30-40kts throughout the overnight and with subsidence inversion setting up, the top of the mixed layer tops out right around 900mb. NBM was too low with sustained winds over land Thursday night and had to blend in the 90th percentile for winds, which look to be much more reasonable. This gives wind gusts anywhere between 30 to 40 mph and will likely result in patchy blowing and drifting snow.

Wind chill temps likely to drop to around minus 20 acrs the north. Cannot rule out the need for a Cold Weather Advisory if the sustained wind is stronger than presently forecast and if temps are several degrees colder. Either way, it will be a pretty raw night to be outside if not bundled up.

Key Message 2... Surface high pressure will be cresting over the area on Friday night. Winds will be fairly light, decoupling over the valleys. Mins are forecast to drop below zero over the north and in the single digits elsewhere. Sky cover remains in question as system drops thru the OH Valley and moves off of the mid-Atlantic coast late Friday night. Mostly clear skies are expected Friday evening before high cirrus moves in from the west over western areas. How quickly this moves in will determine how low temps can drop. Gut feeling is that temps can be knocked down by a few more degrees with radn/l cooling conditions expected under a 2-3 inch snowpack established on Christmas Day.

LONG TERM /SATURDAY THROUGH TUESDAY/

Key Messages... 1) Potential significant winter storm early next week

Key Message 1... The big story in the long term is another winter storm moving in early next week. Deterministic and ensemble guidance has been very consistent on advertising a significant storm in the week between Christmas and New Years. Medium range guidance shows H5 trof moving onto the west coast by the end of this week and amplifying as it crosses the Rockies over the weekend. Differences remain in how quickly it closes off in the Great Lakes and how deep it becomes as it heads into northeast U.S. This ultimately will determine the track and timing of sfc low approaching the CWA and if secondary cyclogenesis can occur over the Gulf of Maine, as most guidance is alluding to. 00z guidance has trended slower by about 6 hours with bulk of the snow not starting until late Sunday evening.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

NEAR TERM: IFR to MVFR conditions over the south and MVFR to VFR conditions over the north will improve to VFR, around midday north and late today over the south. VFR conditions tonight will lower to MVFR to IFR conditions Christmas morning. Conditions will improve to VFR south but may remain MVFR over the north Christmas afternoon. Light north winds today becoming light and variable tonight then increasing out of the northwest on Christmas day.

SHORT TERM: Thursday night-Friday...VFR. NW 10-20kts with gusts to 30-35 kts into Friday morning.

Friday night-Sunday...VFR. NNW 5kts.

MARINE

NEAR TERM: A gale warning will be up today for east winds gusting up to 35 kt. Winds will drop below gale this afternoon then drop below SCA tonight. Winds will increase from the northwest Christmas day reaching gale late in the day. Seas up to 8 ft today then 5 ft tonight and Christmas day.

SHORT TERM: Gale conditions over all waters Thursday night with northwest winds gusting to around 45kts. Gales drop off over the intracoastal zone Friday morning and over the outer waters late Friday morning. Expect winds aoa 25kts through Friday evening before diminishing under high pressure through the end of the weekend.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory until noon EST today for MEZ003>005- 010-011-015-016-029-031. MARINE...Gale Warning until 1 PM EST this afternoon for ANZ050>052.