textproduct: Caribou

WHAT HAS CHANGED

-Updated aviation discussion.

-New uncertainty for snow squalls Friday.

-Extreme Cold Watch upgraded to Extreme Cold Warning. Extreme Cold Warning expanded to southern Piscataquis, central Penobscot, and Northern Washington counties.

-Cold Weather Advisory issued for Downeast Maine and the Bangor region.

-Heavy Freezing Spray Warning issued for the waters.

-Increasing confidence in a winter storm Sunday night through Monday.

KEY MESSAGES

- A couple rounds of heavy snow showers or squalls may cause brief whiteouts and result in slick travel Friday.

- Frigid arctic air with extremely dangerous wind chills this weekend.

- Increasing chance of a winter storm Sunday night into Monday.

DISCUSSION

KEY MESSAGE 1...A couple rounds of heavy snow showers or squalls may cause brief whiteouts and result in slick travel Friday.

KEY MESSAGE 1 DESCRIPTION... Friday the threat of snow squalls is a little more uncertain today compared to last forecast package. An arctic cold front will be approaching from the northwest in Quebec in the afternoon. Timing remains relatively on track but seeing some hi-res model timing differences between RRFS/HRRR/NAM3km and the global models. Expecting mostly sunny morning and midday that will allow for some surface CAPE reaching 30-60j/kg. Very favorable 925-850mb lapse rates at 9-9.5C/km with 850-700mb very favorable at 8-8.5C/km. In the afternoon solid agreement of negative Theta E profiles showing significantly steep low level lapse rates. Lastly, seeing modeled total surface wind divergence mainly positive with some pockets of negative in the Central Highlands to Downeast coast. Negative would indicate surface wind convergence which is favorable for snow squalls. When you put all these parameters together we are seeing elevated BTV snow squall parameter values from NAM/GFS/ECMWF of 1-3 in the southern half of the CWA but some differences with GFS being more widespread. Lastly, modeled soundings show uncertainty of how strong the winds will be aloft in the mixed layer. For now will continue the threat of heavy snow showers and squalls into Friday. However, having to significantly overhaul the POPs since NBM struggles with winter convection in Maine.

KEY MESSAGE 2...Frigid arctic air with extremely dangerous wind chills this weekend.

KEY MESSAGE 2 DESCRIPTION... The pressure gradient between the exiting low to our northeast and the high building in from the west persists through Saturday resulting in winds remaining elevated throughout the day. This will contribute to the continuation of very cold wind chills with the worst conditions right around daybreak where the wind will make the air feel like -30 to -40 degrees in the north and -20 to -30 over southern and coastal areas. Wind chills will improve slightly throughout the day as temperatures warm but will stay well below 0.

Saturday night will feature the coldest temperatures of the weekend but wind chills should be slightly better as winds will be lighter. Some uncertainty still remains as to whether or not the high will move in quick enough for the winds to become nearly calm and to allow some decoupling, sending low temperatures plummeting. Model soundings do not show a strong decoupling signal but clear skies mean that any localized areas that are more sheltered from the wind may see temperatures go below guidance.

KEY MESSAGE 3...Increasing chance of a winter storm Sunday night into Monday.

KEY MESSAGE 3 DESCRIPTION... Models are continuing to converge on a winter storm that will redevelop off the Mid-Atlantic coast before moving northeastward. Many ensemble members show the storm making it into the Gulf of Maine where it will strengthen and bring snowfall to much of the area. Some other ensemble solutions want to track the storm more easterly off the southern New England coast where our area would receive only a few inches at most. The track of the storm will depend heavily on the evolution of the high over our north during the day on Sunday. A weaker high will allow the storm to move up along our coast while a stronger high will keep it further south. Regardless, the greatest totals from this storm are likely to be found in the Downeast and Bangor regions.

AVIATION /01Z FRIDAY THROUGH TUESDAY/

Variable conditions with any snow showers through early morning. Otherwise, VFR/MVFR tonight. Variable conditions with snow showers, possible snow squalls, Friday. Otherwise, VFR/MVFR Friday. West/southwest winds 10 to 15 knots with gusts up to 20 knots tonight. West/southwest winds 10 to 15 knots with gusts up to 20 to 25 knots, becoming west/northwest Friday.

Friday Night...VFR. Wind Shift in the evening. NW winds 10-20kt with gusts up to 30kt possible.

Saturday through Sunday...VFR. W/NW winds 10 to 15 kts with gusts 25 to 30 kts Saturday, diminishing to 5 to 10 kts Saturday night and around 5 kts Sunday.

Sunday night through Monday...Becoming MVFR and likely IFR at southern terminals with light snow. VFR/MVFR and possibly IFR Monday at northern terminals with light snow. N/NE winds increasing to 5 to 10 kts.

Monday night through Tuesday...IFR/MVFR conditions improve to VFR/MVFR. N/NW winds 5 to 10 kts Monday night becoming 10 to 15 kts Tuesday.

MARINE

A Gale Warning is in effect through 1PM Saturday for the Coastal Waters out 25nm. Westerly winds through Friday evening shifting Northwest Friday evening lasting into Saturday. 25-35kt with gusts up to 45kt and seas 6-9ft. A Gale Warning is in effect from 6PM Friday till 7AM Saturday for the Intra-Coastal Waters. Here we expect NW winds 15-25kt with gusts up to 35kt and seas 3-5ft. For all the waters a Heavy Freezing Spray Advisory in effect from 10PM Friday till 10AM Sunday. Heavy freezing spray at a rate of 2 cm per hour or greater expected, and may rapidly accumulate on vessels. Rapid ice accretion on decks and superstructures may result in a catastrophic loss of stability.

Gales decrease to SCA conditions Saturday night with below SCA conditions for both winds and seas Sunday morning. Winds increase to gales Sunday night and may not decrease to SCA criteria until Tuesday but even then there will be borderline gale wind gusts. Seas 6 to 10 ft early Saturday will decrease to 1 to 2 ft Sunday before increasing to 6 to 10 ft Monday night. Heavy freezing spray Saturday morning with moderate freezing spray through Monday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Extreme Cold Warning from 1 AM to 10 AM EST Saturday for MEZ001>006-010-011-031-032. Cold Weather Advisory from 1 AM to 10 AM EST Saturday for MEZ015>017-029-030. MARINE...Gale Warning until 1 PM EST Saturday for ANZ050-051. Heavy Freezing Spray Warning from 10 PM Friday to 10 AM EST Sunday for ANZ050>052. Gale Warning from 6 PM Friday to 7 AM EST Saturday for ANZ052.