textproduct: Caribou

SYNOPSIS

A coastal low exits into the southern Canadian Maritimes today. An Arctic cold front crosses the region on Thursday with high pressure building in for Friday. Another cold front approaches from the northwest on Saturday into Sunday.

NEAR TERM /THROUGH THURSDAY/

Main Points: * Today: Low pressure continues to shift eastward, with snow exiting the area this morning. * Thursday: Arctic front crossing the area will bring a threat for snow squalls to the CWA, which could lead to hazardous travel conditions for the Thursday evening commute.

630 AM Update: The Winter Weather Advisories and Warnings have been cancelled as accumulating snow has exited the region.

Discussion: Low pressure is currently found moving well south of Nova Scotia, with a well defined cirrus shield seen on current IR satellite imagery moving eastward and out of the region. Snow is also exiting the area, with moderate snowfall slowly tapering off Downeast and light snowfall tapering off across eastern Aroostook county. Winds will peak this morning as the low pressure exits the region, and begin to taper off through the rest of the day as a narrow ridge of high pressure moves into the area.

More mild conditions are in store for later this afternoon into tonight, with highs in the upper 20s to lower 30s today, and lows in the upper teens to around 20 tonight.

For Thursday, an arctic front will approach from the west and cross during peak diurnal heating on Thursday. Forecast steep low level lapse rates of 7 to 8 C/km and weak but non-zero CAPE will help support convective snow shower development, particularly along the boundary. Winds will quickly increase aloft behind the front due to the tightened pressure gradient, and should the mixed layer reach up to around 850 mb, over 30 kt winds become accessible and could cause surface gusts strong enough to pick up freshly fallen snow and further limit visibility. Additionally, strong cold air advection with the establishing arctic air mass may result in a flash freeze with temperatures quickly falling from the mid 30s down into the single digits over a few hours. All of these ingredients could lead to hazardous travel conditions, with visibility rapidly dropping to near zero, sudden strong wind gusts, and suddenly slick surfaces. NAM and GFS forecast snow squall parameter both exceed 1 and there is a risk for snow squalls in the most intense heavy snow showers.

SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/

Key Messages -Strong winds expected Thursday night -Low temperatures Thursday night with wind chills as low as 25 to 30 below zero over the north and 15 to 20 below zero north of the coast -Patchy blowing snow expected in open areas Thursday night

Cold air will push into the area Thursday evening in the wake of an Arctic cold front moving through. NW winds sustained between 15- 25 mph during the overnight. Low pressure will be deepening over the Canadian Maritimes with high pressure building into the northeast, leading to tightening pressure gradient. Winds will frequently gust to 35-45 mph and possibly as high as 50-55 mph over the higher terrain. Low temperatures are expected to drop below zero to the north of the Central Highlands into southern Aroostook County. This will lead to winds chills as low as 25 to 30 degrees below zero over portions of the North Woods and Central Highlands, and as low as 15 to 25 degrees below zero north of the coast.

In addition to the wind chills and strong winds, blowing snow will likely be a factor over the open areas Thursday night. Given the cold air blowing over the open waters of the St. Lawrence and favorable low-level flow, cannot rule out a brief laurentian plume of snow showers over northern Aroostook Thursday evening. This may put down minor snow accumulations from the North Woods over towards the Mars Hill area.

Friday will see high temperatures well below normal, though not quite into min maximum temperatures for the day. All but coastal areas will remain in the teens. Skies will be mostly sunny over most areas with partly cloudy conditions moving into the west with subtle s/wv approaching in zonal flow. Wind chill temperatures acrs the north will remain right around zero degrees throughout the day on Friday.

Brief s/wv ridging aloft expected on Friday night acrs the area with lows "warming" into the single digits north of the coast.

LONG TERM /SATURDAY THROUGH TUESDAY/

Key Messages -High pressure early in the weekend -Cold front moves through Saturday night and Sunday

High pressure over the area on Saturday with another cold front approaching from the west Saturday evening. Cannot rule out brief snow showers Saturday night into Sunday morning. Temperatures drop back into the single digits Sunday night. High pressure begins to build in from the west on Monday. 00z guidance begins to diverge after Monday with GFS bringing zonal flow Monday night, EC hinting at a developing trof while CMC brings upr ridge toward the region.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

NEAR TERM: IFR conditions will quickly improve to MVFR/VFR this morning as low cigs and snow exit to the east. VFR conditions continue through the rest of the day and into the night tonight with winds becoming light and variable.

Cigs diminish to MVFR by Thursday morning with TEMPO LIFR in snow showers and squalls. Squalls are most likely across northern terminals. S winds around 5 kts shifting NW and increasing to 10 to 20 kts with gusts 25 to 30 kts, and higher in any squalls.

SHORT TERM: Thursday night...VFR Downeast terminals with MVFR cigs north. NWS 10- 20kts, gusting to 30-35kts.

Friday...VFR. W 5-15ts.

Friday night...Mainly VFR. Light SSW winds.

Saturday-Saturday night...VFR/MVFR cigs with possible IFR in -shsn. SSW 5kts.

Sunday...Mainly VFR, though MVFR possible north. WNW 5-10kts.

MARINE

NEAR TERM: Gale conditions continue over the waters this morning, improving through the day today as high pressure returns to the area. Seas will return to 4 to 6 ft after the first round of gales. Gales will likely return to all waters on Thursday as a strong cold front moves through the area. Sea surface temperatures of 47 to 49 may be too warm for this cold front to result in any freezing spray, but if enough upwelling occur to quickly drop these temperatures, light freezing spray could develop.

SHORT TERM: Gale force winds expected into Friday morning before diminishing to small craft levels through Friday afternoon. Freezing spray may be able to occur if sea surface temperatures can drop to 45 degrees, but not confident that this much upwelling will be realized. Winds look to remain below small craft advisory levels through Sunday. Seas between 3-6 feet through Thursday morning before climbing to 5 to 9 feet Thursday night, then decreasing below small craft levels Friday afternoon. Seas remain below SCA levels through the end of the weekend.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Gale Warning until 10 AM EST this morning for ANZ050-051. Small Craft Advisory until 10 AM EST this morning for ANZ052.