textproduct: Caribou

WHAT HAS CHANGED

- Updated aviation section to reflect 12z TAFs

- Added mention of freezing rain in the forecast for Friday night into early Saturday morning due to increasing agreement across guidance and cold air damming signature on forecast soundings

KEY MESSAGES

1) Light snow likely across far northern Maine tonight followed by sharply colder temperatures Thursday.

2) Wintry mix possible Friday night into Saturday, which could create slick travel conditions by early Saturday morning.

3) Warming trend with above normal temperatures, leading to melting snow pack into the middle of next week.

DISCUSSION

KEY MESSAGE 1... Light snow likely across far northern Maine tonight followed by sharply colder temperatures Thursday.

KEY MESSAGE 1 DESCRIPTION... A sharp cold front will sink south across northern Maine this evening and then across the remainder of the forecast area overnight. As it does so, expect a period of light snow, mainly north of the Katahdin region. Accumulations will generally be an inch or less, but some locally slick travel is possible overnight, especially the St. John valley region in far northern Maine. It will also turn sharply colder with the passage of the front, with temperatures falling into the single digits above zero across far northern areas. Thursday will be a much colder day than today, with highs only in the lower to mid teens across the north mid 20s for the Bangor region and Downeast.

KEY MESSAGE 2... Wintry mix possible Friday night into Saturday, which could create slick travel conditions by early Saturday morning.

KEY MESSAGE 2 DESCRIPTION... A low pressure system will approach from the west Friday night into this weekend. A warm front should lift north through the CWA sometime Friday night through Saturday, followed by a cold front late Saturday into Saturday night.

A complicating factor with this low pressure system will be the temperature profile. After several nights of temperatures slightly below average throughout the forecast area, a warm front will lift northwards over the area ushering in much warmer air, where surface temperatures will eventually surge towards 50 degrees later in the day on Saturday. As this happens, there is increasing likelihood that a warm nose will develop around 900mb, making way for the generation of wintry mixed precip of either freezing rain and/or sleet late Friday night into early Saturday morning. There remain several questions with this forecast:

A: Will cold air damming be as significant as it appears at first glance? - The NBM suggests a chance for freezing rain across the entire CWA all night. Given the blended nature of this guidance, this solution is likely overdone for ice amounts. That said, after inspecting guidance not included in the national blend, such as the ICON and UKMET models, which also bring in freezing rain through the night, there is increased confidence in the existence of a wintry mix. Forecast profiles bring SE winds at the surface and SW winds aloft, which is akin to previous freezing rain events such as the December 11, 2024 event which featured a similar wind profile in a strong CAD setup. Contrary to the previous statement, it has also been found that SSE/NNW isobar orientation is preferred for CAD in this FA, with SSW/NNE isobar orientation less favorable. The GFS holds the favorable orientation briefly, but the chance for CAD appears more marginal using the isobar orientation method.

B: Even if cold air damming exists, will there be enough moisture for precip to fall as a wintry mix? - Here there lies even less certainty than the existence of CAD. In events past, this is often where our area struggles to receive much in the way of wintry mix. Indeed, guidance shows potentially some prefrontal precip followed by precip along the warm front. For the prefrontal precip, this is most likely if the previous coastal low pressure on Friday tracks closer to the CWA, feeding moisture into our region. If it remains on a track south of Nova Scotia, it is unlikely there will be enough precip falling into any lingering dry air in our FA to saturate the profile and for precip to make it all the way to the surface before warm air makes it all the way to the surface. But, should there be enough precip along the warm front itself, the dry air may very well be overcome and a brief period of freezing rain and/or sleet could develop early Saturday morning before the CAD setup erodes into the day.

No matter the solution, warm air advection should increase into the day on Saturday as the pressure gradient tightens and southerly winds increase, lifting surface temperatures well into the 40s and leading to stratiform warm rain that lasts through the rest of the day. Behind the cold front into the day on Sunday, temperatures will fall some, but a more mild air mass will remain in place, keeping temperatures above normal through the end of the weekend.

KEY MESSAGE 3... Warming trend with above normal temperatures, leading to melting snow pack into the middle of next week.

KEY MESSAGE 3 DESCRIPTION... A split stream flow may develop into the next work week, with the subtropical jet to our south and polar jet to our north, ushering future low pressure systems south and north of our forecast area respectively through the first half of the next week. With a more mild air mass in place and no change in air mass through the beginning of the week, temperatures could gradually climb each day, with daily high temperatures lifting into the upper 40s to mid 50s through the forecast area each day. For lows, temperatures could fall into the mid 20s to around 30 each night.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

KFVE/KCAR/KPQI/KHUL...VFR through much of this afternoon, then MVFR or lower possible in -SN this evening into tonight, especially N of KHUL. VFR returns Thursday. W wind 10 to 15 kt today, becoming N 5 to 10 kt tonight through Thursday.

KBGR/KBHB...VFR through Thursday. SW to W wind 10 to 15 kt today, then light W becoming N after midnight, then N 10 to 15 kt on Thursday.

Thurs night - Fri...VFR/MVFR. Light E winds become SE at 5 to 10 kts.

Fri night - Sat...MVFR/IFR. Wintry mix possible overnight through early Saturday morning, becoming rain through the day on Saturday. SSE winds 5 to 10 kts overnight becoming S at 10 to 15 kts gusting to 25 kts on Saturday.

Sat night - Sun...VFR across all terminals. Winds shift W winds 5 to 10 kts.

MARINE

Winds/seas will remain below SCA levels today through tonight. Winds/seas could then approach SCA levels again by Thursday afternoon.

Small craft advisory criteria will likely be met Thursday night through the day on Friday with WNW winds gusting 25 to 30 kts, especially over the coastal waters. Warming temperatures through this time will limit the threat for freezing spray. Snow could move in over the waters on Friday, likely switching to rain Friday night into Saturday and potentially limiting visibility over this time. Gale conditions are possible late Saturday into Saturday night behind a cold front. Temperatures will remain mild enough through the weekend for no freezing spray threat at that time.

CAR WATCHES/WARNINGS/ADVISORIES

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