textproduct: Caribou

WHAT HAS CHANGED

- Lowered snowfall chances for Saturday with increasing model confidence.

- Increased wind gusts Saturday night into Sunday with increasing probabilities of stronger winds. This in turn is increasing the likelihood for cold weather headlines.

KEY MESSAGES

1) Arctic blast brings gusty winds, patchy blowing snow, and bitter cold wind chills expected over the weekend.

2) Weak weather disturbances crossing the area today, Thursday and again on Saturday may give some patchy light snow to parts of the region.

DISCUSSION

KEY MESSAGE 1 Arctic blast brings gusty winds, patchy blowing snow, and bitter cold wind chills expected over the weekend.

KEY MESSAGE 2 DESCRIPTION... Saturday afternoon an occluded front will cross the CWA from NW to SE bringing a return to frigid arctic air. 500mb trof with heights randing from 510-514dam dips SE from Ontario/Quebec. This is key since it will be bringing cold air to the region it is diving south to our west. This is typical of the deeply negative AO at around -3SD with approx -1SD NAO (blocking in North Atlantic) and the positive PNA pattern (+1SD). As the front crosses the region expect temperatures to rapidly fall with FROPA in the afternoon before sunset. An idea of where this air mass is arriving from can be seen using the NOAA Hysplit Backward Trajectory model. This airmass originated on January 29th from the Arctic Ocean, approx 950 miles N of Alaska, around the 85N latitude. It traveled SE from the Arctic Ocean to Hudson Bay and will be knocking on our door Saturday as the front approaches.

As FROPA takes place, mentioned below in Key Message 2, temperatures will fall in the afternoon. Since the 500mb trof is to our west expecting the pressure gradient to tighten over the CWA with rapidly increasing winds heading into Saturday night. Have opted to mix in NBM90th percentile for winds as operational NBM is struggling with the concept of the increasing 950mb winds. Modeled soundings and ensembles do show a mixed boundary layer up to 950mb (approx 2kft) Saturday night into Sunday where the winds at the top of the mixed layer are 25-35kt which will sufficiently mix to the surface. Expecting the strongest winds along the terrain of the Longfellow Mtns resulting in strongest gusts in Greenville region, but cannot rule out Millinocket, due to downslope off Katahdin which is typical in NW flow.

Saturday night into Sunday AM with winds gusting 20-35mph across the area, temperatures will be crashing deeply below zero for most. Sun AM lows of -15F to -10F in the North Woods and Moosehead Region, -10F to -5F across the rest of the Crown and Northern Maine along with the rest of the Upper Penobscot Valley. -5F to 0F for Bangor Region east along the Airline to Calais and down to the Downeast Coast with 0-5F on the islands. When you combine the frigid temperatures (5-10deg below norm) with gusty winds expect frigid wind chills. Probabilities of Cold Weather Advisory criteria being met (wind chill -20F) for the Bangor Region and Downeast has increased to 25-45% with the best chances around 50% in the Dexter Region. North of there into Northern Maine where the criteria is -25F the North Woods and Moosehead Region probabilities have increased to 50-65% with eastern Aroostook region increasing to 30-40%. Lastly, given the gusts cannot rule out patchy blowing snow across the open fields of Northern Maine and Downeast Maine, and importantly for recreation out on the lakes/ponds.

Sunday remains cold with highs 5-10F across the north and 10-15F for the southern half of the CWA. The increasing sun angle which peaks at 27 degrees at solar noon will help some but not enough to keep things frigid. Additionally winds gusting 15-30mph will keep wind chills -15F to -10F across the north, -10F to 0F elsewhere. Patchy blowing snow will continue in areas seeing gusts >20mph.

KEY MESSAGE 2 Weak weather disturbances crossing the area today, Thursday and again on Saturday may give some patchy light snow to parts of the region.

KEY MESSAGE 2 DESCRIPTION... A small upper low crossing from Northern New York State into Western New england this morning will track across Southern Maine around midday today. This may bring some light snow showers to the Western Highlands late this morning then a period of light snow Downeast giving up to an inch over coastal locations, mainly Washington County, early this afternoon.

A weak upper trough crossing the north on Thursday may bring a brief period of light snow across the north, mainly over the St. John Valley. Any snow will easily accumulate on roads and walkways due to the very cold ground temperatures.

On Saturday a deep 500mb trof will approach from the west along the Ontario/Quebec border. At the surface an occluded front with surface low pressure developing at a triple point will track SE through New England. Weak surface low will track into the Gulf of Maine south of the CWA. Expecting mainly a chance of snow showers across the northern 1/2 of the CWA with a chance of light snow for the southern 1/2 of the CWA. Models continue to come into agreement with operational and ensembles showing less and less QPF for this event. Best chance of accumulating snow will be the islands of Hancock County in Penobscot Bay and points southwestward into GYX CWA. Latest NBM probabilities of >1 inch of snow have dropped to 20% in Bangor, 35% on Deer Isle, and around 35% for Newport area. North and east of these locations the probabilities are <20%. These numbers have dropped between 10-20% since yesterday's 19z NBM. Overall, most locations see just perhaps snowflakes in the air with the far SW zones near the CAR/GYX CWA border seeing up to a 0.5 inch but most likely just a trace dusting. Not expecting much in the way of impacts.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

Today...MVFR north and VFR south with the exception of a brief period of MVFR over interior sections during the midday today. Wind NW under 5 kt all sites except up to 10 kt near the coast.

Tonight...VFR all sites. Wind NW less than 5 kt.

Thursday...VFR to MVFR over the north. VFR south. Wind NW 5 to 10 kt.

Friday...VFR with high cigs. Winds light and variable.

Saturday...VFR. Low probabilities of MVFR cigs at BGR and BHB due to -SN. Elsewhere, generally just VCSH/-SHSN. Light and variable winds till the late afternoon with FROPA winds shift N-NW 10-15kt gusting 20-25kt.

Saturday night...VFR, possible MVFR cigs north. NW winds 10-15kt gusting 20-30kt.

Sunday...VFR. NW winds 10-15kt gusting 20-30kt.

MARINE

A few northwesterly wind gusts may reach 25 kt today over the offshore waters today. Otherwise, wind and seas should be below SCA today, tonight and Thursday.

Looking ahead...Winds/seas to be below SCA through early Saturday morning. Winds less than 20kt and seas 1-2ft. N-NE winds rapidly increase to SCA levels early Saturday afternoon gusting up to 30kt. Seas will build Saturday afternoon to 2-5ft. N-NW Gales are likely Saturday afternoon into Sunday afternoon with gusts up to 45kt. Seas will be 2-5ft on the intra-coastal waters and 6-9ft on the coastal waters. Sunday night winds fall to SCA conditions and expecting those to last into Tuesday afternoon.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...None.