textproduct: Caribou

WHAT HAS CHANGED

- Tonights lows were lowered in the normally colder valleys of the north where a clear sky and calm conditions will allow for a low level inversion to form.

- Have hoisted a Extreme Cold Watch for the Moosehead Region and portions of the North Woods for Saturday night into Sunday AM.

- Have hoisted a Gale Watch for Saturday PM into Sunday PM for the Coastal Waters.

KEY MESSAGES

1) Arctic front crosses the region Saturday with dangerous wind chills Saturday night into Sunday. Below normal level temperatures persist into Monday.

2) Snow showers are possible across the north today as a weak trough crosses the region.

3) A clear sky and calm air tonight will result in frigid low temperatures across the north.

DISCUSSION

KEY MESSAGE 1... Arctic front crosses the region Saturday with dangerous wind chills Saturday night into Sunday. Below normal level temperatures persist into Monday.

KEY MESSAGE 1 DESCRIPTION... Overall operational modeling and ensemble members have slowed the timing of the arctic front by 1-2hrs across the state. It is very moisture starved in our area as the weak surface low tracks deeply SE of southern New England with rapid development expected. The 500mb trof digs deeply to our south on Saturday with a 504dam low up over northern Quebec and a 513dam low diving south of Long Island. The cold front will provide some isolated to scattered snow showers ahead of the front but very little accumulations. Temperatures will rapidly fall behind FROPA as this airmass is purely arctic.

Running the NOAA Hysplit Backward Trajectory model this airmass arriving at CAR & BGR originated from Siberia Russia on Jan 28th and stayed around the North Pole between Jan 29-31st. The cold air broke off and pushed south to Hudson Bay Canada then will be arriving into Maine Saturday night. This is very textbook with a strong negative AO (-3.5SD), positive PNA (+1SD) and weak negative neutral NAO. The weak negative neutral NAO gives confidence this arctic blast will be short lived at only 48-72hrs and we will return to seasonable conditions.

Saturday night temperatures will fall back into the -5F to +5F range from Eastern Aroostook to Penobscot Valley including Baxter SP area south to the Downeast Coast with the Downeast the best locations to remain on the positive side of 0F. For the Moosehead Region into the North Woods modeling remains consistent in sending air temperatures into the -12F to -7F range with NBM 4.3 and 5.0 probabilities increasing indicating better likelihood of reaching at least -10F air temps. As low pressure deepens well south of Maine and high pressure in Quebec pushes in with the 500mb trof to our west gives us the best chance of a windy night. Modeled soundings continue to indicate a well mixed boundary layer up 2kft to 950mb where winds are expected to be in the 25-35kt range. NBM operational winds/gusts continues to be low so opted to add in NBM90th for wind speeds and increased wind gusts especially along the Longfellow Mtns. This remains consistent with NBM 4.3 and 5.0 QMD wind gusts probabilities of >25mph gusts in the 70-90% range in the CWA with probs of >30mph in the 65-85% range along the Longfellows. The combination of gusty winds and cold temperatures will send wind chills pretty widespread -25F to -15F for the CWA. Wind chills ranging -35 to -30F across the North Woods and Moosehead Region will be the coldest spots. Given this increased confidence have opted to hoist an Extreme Cold Watch for Northern and Central Piscataquis and Northern Somerset counties from 7PM Saturday through 10AM Sunday. Outside of the water area there may need to be a Cold Weather Advisory if wind chills reach -25F north and then -20F in southern zones which is criteria.

Sunday will remain cold as the trof remains over the region and conditions remain breezy. The afternoon sun angle now peaks at 27 degrees off the horizon which is now helping modify the airmass a little bit. Highs into the single digits above zero north and 10-15F for the rest of the CWA. Breezy NW winds 10-20mph with higher gusts will keep wind chills mainly below zero for most and around 0F at the coast. Sunday night yet another cold night with air temperatures pretty much CWA wide below zero with the coldest in the North Woods and St. John Valley. Sunday night into Monday there is a greater chance of Cold Weather Headlines with 70-90% probabilities of reaching advisory level criteria in the northern 1/2 to 2/3rd of the CWA.

KEY MESSAGE 2...Snow showers are possible across the north today as a weak trough crosses the region.

KEY MESSAGE 2 DESCRIPTION... An upper level trough and weak surface cold front will cross the area today. Steep lapse rates up to 6K ft with some CAPE up to 25 J/KG may combine with some surface convergence downstream from the Laurentian Mountains to produce a few bands of snow showers from the north central highlands southeast across Southeastern Aroostook County. Any accumulation should be less than a half inch.

KEY MESSAGE 3... A clear sky and calm air tonight will result in frigid low temperatures across the north.

KEY MESSAGE 3 DESCRIPTION... High pressure will crest over the area tonight allowing the air to become calm and form a low level inversion under a clear sky. This will result in frigid low temperatures in the normally colder valleys with lows down to 20 below in some of the normally colder valleys. The lowest readings may occur at the Presque Isle airport and in parts of the north woods. Rivers have a thick layer of ice now, and snow on the ice, which will allow river valleys to become very cold with little modification form the water beneath.

AVIATION /08Z THURSDAY THROUGH MONDAY/

Today...VFR to occasionally MVFR across the north and VFR over the south. NW wind 5 to 10 kt.

Tonight...VFR. NW wind less than 5 kt.

Friday...VFR. Light and variable wind.

Saturday...VFR. Low probability of BKN MVFR cigs with VCSH/-SHSN in the afternoon. NE winds around 5kt in the AM shift N 5-15kt in the afternoon.

Saturday Night...VFR. Low probability of BKN MVFR cigs at northern terms. NW winds 10-15kt gusting 20-30kt.

Sunday...VFR. Low probability of SCT MVFR cigs at northern terms. NW winds 10-15kt gusting 20-30kt.

Monday...VFR. NW winds 10-15kt with gusts 20-25kt.

MARINE

A few gusts from the northwest may approach 25 kt early this evening. Otherwise, wind and seas are expected to remain below SCA Today, tonight and Friday.

Winds will rapidly increase to SCA conditions Saturday midday then approach Gales in the afternoon. A Gale Watch has been hoisted for all the Coastal Waters from 4PM EST Saturday through 1PM EST Sunday. N-NNW Gales are likely during this timeframe. N-NNW winds 20-30kt with gusts up to 40kt and seas 4-7ft. In addition to the Gales moderate freezing spray is expected from Saturday evening to Monday early afternoon. There remains the potential for heavy freezing spray Saturday night into Sunday morning. The Coastal Waters will be experiencing a prolonged period of hazardous conditions. Winds will relax back to SCA conditions later Sunday afternoon and expected to last through early Wednesday AM. Light to moderate freezing spray expected Monday through early Wednesday AM. Seas will generally be 2-4ft Monday through Wednesday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Extreme Cold Watch from Saturday evening through Sunday morning for MEZ003-004-010. MARINE...Gale Watch from Saturday afternoon through Sunday afternoon for ANZ050>052.