textproduct: Caribou

WHAT HAS CHANGED

-introduced slight chance of snow showers/snow squall late Saturday afternoon or Saturday evening.

KEY MESSAGES

1) A cold front will approach on Saturday bringing strong south winds ahead of it and some rain and snow showers. There will be a chance for additional snow showers and isolated snow squalls as a secondary Arctic front pushes in late Saturday afternoon or Saturday evening. This could result in poor visibility and slippery conditions.

2) Bitter cold Arctic air will surge into the region Saturday night into Sunday bringing frigid temperatures and wind chills to begin the week next week. The coldest weather will be Sunday night bringing a risk of hypothermia and frostbite.

DISCUSSION

KEY MESSAGE 1...A cold front will approach on Saturday bringing strong south winds ahead of it and some rain and snow showers. There will be a chance for additional snow showers and isolated snow squalls as a secondary Arctic front pushes in late Saturday afternoon or Saturday evening. This could result in poor visibility and slippery conditions.

KEY MESSAGE 1 DESCRIPTION... As a strong cold front approaches on Saturday, the gradient between the front and high pressure off to the east will bring a strong south wind across the region. South winds up to 25 mph with gusts to 40 mph are possible. The south winds will advect warmer air into the region with highs near 40 across much of the area. Rain and snow showers will push across the area ahead of the front early Saturday afternoon.

The cold front may come through in two parts with the initial front coming through early Saturday afternoon followed by a secondary Arctic cold front coming through late Saturday afternoon or Saturday evening. Soundings are showing steep lapse rates and even some narrow CAPE up to 7K ft. The combination of instability and frontal convergence will bring a chance for snow showers and possibly isolated snow squalls late Saturday or Saturday evening. Strong gusty winds mixing down followed by abruptly falling temperatures behind the Arctic front will introduce the risk that any squalls may produce poor visibility in blowing snow followed by wet surfaces freezing as much colder air surges in. Forecast models are not agreeing on the timing of the front, late afternoon or evening, but they are agreeing that there will be a period of instability as the front pushes in.

KEY MESSAGE 2...Bitter cold Arctic air will surge into the region Saturday night into Sunday bringing frigid temperatures and wind chills to begin the week next week. The coldest weather will be Sunday night bringing a risk of hypothermia and frostbite.

KEY MESSAGE 2 DESCRIPTION... Colder Arctic air will overspread the region overnight Saturday night into Sunday. There is a chance that a shallow and fast moving wave of low pressure could bring a period of light snow on Sunday with the best chances across the south. Otherwise, Sunday will be much colder with highs from the low teens north to the upper 20s Downeast which will result in highs being around 15 degrees colder than normal north and 10 degrees colder than normal Downeast. Wind chills midday Sunday will range from around zero north to the upper teens Downeast.

The coldest temperatures will likely come Sunday night as Arctic high pressure presses in from the west. Lows by Monday morning will range from the mid teens below northwest to near zero over interior Downeast. There is some uncertainty whether the high will build over enough to allow winds to calm and the air to decouple. The GFS suggests this is a possibility while the ECMWF maintains a bit of a northwesterly gradient overnight. If the air does decouple, we can't rule out a few northern valleys getting close to 20 below by dawn on Monday. Wind chills early Monday morning are expected to range from the mid 20s below north to the low teens below interior Downeast. Monday will be bitter cold with highs from near 10 over the far north to around 20 Downeast and wind chills from around zero north to the upper single digits Downeast.

AVIATION /12Z THURSDAY THROUGH MONDAY/

Today...VFR at BHB next 24 hours. Remainder of terminals will see MVFR/IFR in low cigs and -shsn this morning. Improvement to VFR this afternoon, though may see FVE experience MVFR restrictions in -shsn between 18-21z. Light south winds become southwesterly 5-15kts this afternoon.

Friday...VFR. SW wind around 5 kt.

Friday night...VFR lowering to IFR over the south during the evening and IFR over the north late. S wind increasing to around 10 kt.

Saturday...IFR. S wind around 15 kt gusting up to 30 kt. SW wind shear around 2K ft.

Saturday night...IFR improving to MVFR. winds becoming NW 5 to 10 kt.

Sunday...MVFR south, VFR to MVFR north. NW wind around 10 kt.

Sunday night...VFR. NW wind around 5 kt.

Monday...VFR. W wind 5 to 10 kt.

MARINE

SCA conditions continue over the outer waters today with winds gusting to near 30kts this afternoon following frontal passage. Seas will remain above 5ft throughout the day before diminishing this evening. Winds and seas look to remain small craft levels through the day on Friday. Light freezing spray develops over the waters on Friday morning.

A SCA will be needed late Friday night through Saturday for S winds gusting up to 30 kt. A few gusts to 35 kt will be possible Saturday morning. Another SCA and possibly a gale will be needed Sunday into Monday for N winds gusting 30 kt or higher. Moderate freezing spray is likely Sunday night into Monday morning. Seas will build up to 6 ft Friday night then 7 ft Saturday in response to the southerly. Seas will drop back to 4 ft Saturday night and remain below 4 ft into early next week.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ050- 051.