textproduct: Caribou

SYNOPSIS

Low pressure exits the area to the southeast this evening. High pressure will build in from the northwest tonight into Friday and be to our north over the weekend. Low pressure will approach on Monday and exit to the northeast Tuesday.

NEAR TERM /THROUGH FRIDAY NIGHT/

630 PM Update (MS): Re-issued SPS through 6z for blowing and drifting snow, but expanded the area given reports, observations, and webcams showing blowing snow in other parts of the forecast area.

Key Messages... 1) Gusty Winds to lead to Blowing Snow 2) Frigid Temperatures Tonight into Tomorrow

Discussion...

Key Message 1... The weak low pressure system that provided light snow this morning is tracking SE of Nova Scotia tonight. Associated 500mb trof pushes east over the Maritimes tonight. Surface high pressure is arriving over Central Quebec which will tighten the pressure gradient this evening. Hi-res models show an area of increasing winds of 30-40kt developing at 2-3kft and expecting the boundary layer to increasingly mix to that height tonight. NW winds at the surface will be increasing over the next 1-3hrs and begin gusting 30-35mph across much of the CWA with isolated gusts up to 45mph especially in higher terrain and wider open areas. Given the recent snows being light and fluffy we do expect blowing and drifting of the snow in open areas of the CWA. The potentially worst areas of the blowing snow will be in the agricultural areas of Northern Maine which will create localized near zero visibility at times especially on north to south oriented roadways. In anticipation have issued a heads up SPS through 6PM EST for Northern Penobscot and all of Aroostook County given any holiday travel expected tonight.

Key Message 2... Strong cold air advection will take place tonight as the arctic high dives southeast in Quebec towards Maine. 925mb temperatures will be falling to the -20C to -18C range. Using the NOAA Hysplit backward trajectory model this airmass originated from far Northern Nunavut Canada near the Northwestern Passages. Air temperatures will fall back into the single digits below zero to near 0F across northern Maine. Air temperatures 0F to +5F for the Bangor Region, Interior Downeast to the coastline with 5-10F on the islands. As you combined gusty NW winds expecting wind chills -20F to -15F across much of Northern Maine and isolated areas as cold as -25F tonight. Across the Central Highlands to Bangor Region expecting wind chills of -15F to -10F, Downeast coast -12F to -8F for wind chills tonight. Tomorrow as the high pressure settles overhead expect winds to relax but even under sunny skies it will be cold. High temperatures 6-10F over the North Woods and St. John Valley, 9-12F across the rest of The County and Northern Maine. Expecting 8-11F for Moosehead Region, 12-15F for the Bangor Region eastward along the Airline to Calais and north to Danforth. Lastly expecting the warmest spots of 15-20F for the Downeast coastline. Air temperatures will be 15-20 degrees below seasonable normals. North winds 5-15mph will still result in single digits below zero wind chills in Northern Maine and around 0F for Bangor Region to the coast.

SHORT TERM /SATURDAY THROUGH SUNDAY/

Key Message... 1) Anomalously cold temperatures Saturday and Saturday night

Key Message 1... Northwest flow induced by a high positioned just to our north will result in cold air continuing to be funneled down from Canada keeping our temperatures 10 to 15 degrees below normal on Saturday and 5 to 10 degrees below normal Saturday night. Clear skies and a cold snowpack should aid in cooling overnight but enough of a pressure gradient over us is likely to result in a light breeze, preventing us from becoming fully decoupled. The best chance for strong radiational cooling will be in the North Woods where winds will be lighter.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Key Messages... 1) Potential significant winter storm Monday through early Tuesday. Likely snow north of the Katahdin region and mostly rain along the coast with a mix in between.

Key Message 1... Model guidance is in good agreement that a winter storm will impact the region early next week but uncertainty remains regarding its evolution. Given the upper-level energy associated with the system has just entered Alaska it will now be better sampled by the upper-air network in that region. This should help models begin to converge on a solution over the next day or so.

Guidance suggests the storm will be arriving to the region generally in the Monday morning through early Tuesday timeframe but some timing differences still exist and thus timing may have to be adjusted several hours forward or backwards depending on model trends.

The greatest uncertainty remains in precipitation types. Model ensemble guidance is expressing some modest agreement that areas north of the Katahdin region will be mostly snow while areas along the immediate coast will see a transition to rain at some point. But two key questions remain...How far north does the rain/snow line advance north and will there be any freezing rain or sleet. Ensembles show a wide array of solutions with mixed precip up through northern Maine on one extreme end and all snow for the Downeast area on the other extreme end. The reasoning behind these differences is in where, when, and if secondary low development occurs along the coast. If it develops later and further north, a mixed bag of precip is expected north of Bangor with cold rain along the coast. Contrarily, if it develops earlier and further south, snow is more likely over the Bangor/Interior Downeast region. For this forecast, kept a mix of rain and snow up through the Upper Penobscot Valley as a middle ground between the solutions.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

NEAR TERM: VFR with tempo MVFR possible in BLSN, -SN, and marginal ceilings early...mainly before 4z. NW winds 10-15G25 kt, decreasing quickly to around 5kt after sunset/21z Fri. LLWS likely tonight with an inversion around 900-925mb, along with DRSN.

SHORT TERM: Saturday-Sunday...VFR. NNW winds around 5 to 10 kts.

Sunday night...Diminishing to MVFR late. Light WNW becoming light S late.

Monday...IFR/LIFR in light snow north and mixed precip south. SSE 5 to 10kts.

Monday night...IFR/LIFR early, especially for northern terminals becoming IFR/MVFR late. W winds 5 to 10 kts.

Tuesday...VFR/MVFR. W winds 10 to 20 kts.

MARINE

NEAR TERM: Gale Warning in effect from 4PM this afternoon through 10AM Friday. N-NNW winds 25-35kt with gusts up to 45kt and seas 4-7ft. Freezing Spray Advisory in effect from 10PM tonight through 10AM Friday. Moderate accumulations of freezing spray expected. Expect winds to relax Friday morning to SCA levels through sunset with seas subsiding to 2-5ft by late day. Tomorrow night expect winds/seas below SCA levels. Sea surface water temperatures from the Downeast coast out 25nm range from 43-45F including Penobscot and Passamaquoddy Bays.

SHORT TERM: Winds increase to above small craft advisory criteria Saturday evening and decrease below criteria Sunday evening. Winds increase to gales Monday evening with a slight chance of storm conditions Tuesday. Seas may exceed 10 ft Tuesday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Gale Warning until 10 AM EST Friday for ANZ050>052. Freezing Spray Advisory from 10 PM this evening to 10 AM EST Friday for ANZ050>052.