textproduct: Caribou

WHAT HAS CHANGED

- 7 AM UPdate: Updated aviation section to reflect the 12z TAFs. Raised temperatures slightly based on current observations and trends.

- Confidence increasing in significant mixed wintry precipitation in Northern Maine late Thursday through Friday.

KEY MESSAGES

1) Wintry mix develops late today through tonight, with a threat for slick surfaces and travel difficulties into the Wednesday morning commute.

2) Chance for significant wintry precipitation late Thursday through Friday night, which could greatly impact Thursday evening, Friday morning, and Friday evening commutes.

3) Pressure system moves through region this weekend, bringing potential for another round of snow/rain/freezing rain, that could impact travel.

DISCUSSION

KEY MESSAGE 1... Wintry mix develops late today through tonight, with a threat for slick surfaces and travel difficulties into the Wednesday morning commute.

KEY MESSAGE 1 DESCRIPTION... The winter storm beginning today will come in three parts. First, a coastal low this morning, with impacts mainly to the Downeast region. Second, a warm front lifts through the area through the night, bringing the bulk of the mixed precipitation to the area. And finally, a cold front comes crashing through the CWA, ending precip for the forecast area.

* 1. Coastal Low: A quick moving shortwave will cross the Gulf of Maine through the day today. This small low may have a region of enhanced precip on its north edge, with a chance for banding across the Bangor and Interior Downeast regions. Temperatures may only be a few degrees above freezing through the day today in this area, leading to a chance for snow early on followed by a mix of ice pellets transitioning to warm rain. There is a chance for some freezing rain on the far northern edge of this heavier precip. A couple of inches of snow are possible across the Central Highlands through Southern Aroostook as well. The low will exit over Nova Scotia into this evening, leaving the forecast are in a precip lull early this evening.

* 2. Warm Front: A pause in precip will not last long as the next feature, a warm front, lifts northwards through the area, and the approaching surface low helps advect moisture into the region. With a pronounced warm nose inversion seen on forecast soundings, this setup has all the markings for a sleet maker. Freezing rain is also expected, and with the slow northern progression of the warm front, conditions prime for freezing rain and sleet respectively will remain over the same region for an extended period of time. This could result in around a half inch of sleet across the Central Highlands through southern Aroostook county, and the potential of a tenth to a quarter inch of ice accretion just south of the band of sleet. North of this mixed precip will likely remain all snow, though a brief period of a few ice pellets or freezing drizzle is possible towards the end of this portion of the storm. All warm rain is expected in the Downeast and Bangor regions and through the coast. This portion of the storm will last through the night tonight, and slick surfaces may remain early Wednesday morning and could have impacts to travel conditions Wednesday morning.

* 3. Cold Front: Finally, a cold front will clear through the area later Wednesday morning into Wednesday afternoon, clearing precipitation out of the forecast area. Temperatures above freezing through the forecast area will come crashing down behind this frontal passage as lows drop into the teens in the north and low 20s Downeast. Any surfaces which remain wet as temperatures plummet could quickly freeze into a glaze, and slick conditions may return for the Wednesday evening commute.

KEY MESSAGE 2...Chance for significant wintry precipitation late Thursday through Friday night, which could greatly impact Thursday evening, Friday morning, and Friday evening commutes.

KEY MESSAGE 2 DESCRIPTION... High pressure on Tuesday shifts eastward and settles to our north, as another low pressure system approaches from the southwest. Mid-level warm front associated with aforementioned low pressure system lifts over the region Thursday into Friday, bringing warmer temperatures into the region. With this system, precipitation begins to fill in from southwest to northeast. Colder air ahead of the warm front allows for mostly snow showers Thursday into Thursday night, before warm mid-layer air moves in, potentially transitioning snow over to freezing rain. Highest chances of freezing rain are in interior Downeast, Central Highlands, and portions of Aroostook county. Majority of this ice is expected to fall Thursday night into Friday morning, causing a potential for significant travel impacts for Friday morning commute. Roughly around 0.1 to 0.2 inches of ice accretion is possible. Actual snowfall accumulation are anticipated to be the highest in the north, between 1-4 inches.

Precipitation types are going to heavily depend on the track of the low pressure system. Northerly track will bring would bring period of freezing rain farther north in the state, while a southerly track would bring more snow to the north. Despite decreasing precipitation trending models currently, there is still a decent moisture column and PWATS around 0.75 to 1 inch with this system. Temperatures rise above freezing on Friday and all precipitation should transition over to rain during the day. Precipitation intensity starts to diminish overnight on Friday, but rain/snow showers persist through the upcoming weekend.

KEY MESSAGE 3...Pressure system moves through region this weekend, bringing potential for another round of snow/rain/freezing rain, that could impact travel.

KEY MESSAGE 3 DESCRIPTION... Yet another low pressure system moves through the area Friday night through Sunday. Daytime highs generally in the 40s in the north and 50s Downeast. Mostly a chance for rain Downeast into the Central Highlands, with a chance for a rain snow mix in central and southern Aroostook, and snow in the far north, on Saturday into Saturday evening. A chance for impactful freezing rain in northern and central Maine Saturday night, before switching over to all rain Sunday. ECMWF and GFS are consistent in both anticipating a round of precipitation to occur in the north Saturday night into Sunday, and another round of precipitation throughout the state Sunday into Sunday night. Continue to monitor the forecast for updates, as the precipitation types of these storms will heavily depend on pressure system tracks.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Today...At northern terminals, VFR conditions continue. N winds 5 to 10 kts. At southern terminals, cigs fall to MVFR/IFR in snow changing over to rain. Brief ice pellets possible. NE winds 5 to 10 kts. Small improvement to conditions and lessening of precip likely around 18z this afternoon.

Tonight...At northern terminals, cigs falling to MVFR or potentially IFR in snow. At southern terminals, MVFR/IFR continues with rain. KGNR through KHUL could see ice pellets and freezing rain. E winds 5 to 10 kts.

Wednesday...All terminals will quickly improve to VFR behind a cold front. Winds shift N 5 to 10 kts with gusts to 20 kts.

Wednesday night...Generally VFR. Potential for MVFR with lingering rain/snow showers at southern terminals. N/NE winds at 5 to 10 kts.

Thursday...VFR early, with cigs falling towards MVFR/IFR depending on storm onset timing. E winds around 5 kts.

Thursday night - Friday night...Decreasing conditions to IFR/LIFR in mixed precip types, and staying IFR/LIFR into Fri night. Potential for freezing rain is highest at northern terminals, with sleet/snow possible at KBGR, and a rain/snow mix possible at KBHB. Generally transitions to rain during the day on Friday. E/SE winds 10 to 15 kts, becoming NW Friday night. Gusts 20-25 kts possible Friday.

Saturday...Generally VFR early. Possible MVFR with snow in the north and rain Downeast. NE wind 5-10 kts.

MARINE

Small craft advisory conditions continue today through Wednesday, with seas 3 to 7 ft. There may be a brief pause in advisory conditions this afternoon before swell returns tonight with a passing low pressure, and seas return to 5 to 9 ft. Wind gusts will begin to increase towards 25 kts late on Wednesday.

Seas gradually retreat to 5ft and below, and winds slowly diminish below SCA criteria below through Wednesday night. Winds and seas approach SCA criteria again by Friday, with these conditions lingering through the weekend. Chance for rain Wednesday, switching to a chance for snow Thursday into Friday morning. Chance of rain Friday through Sunday. NE winds Wednesday night, shifting to the SE Friday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory from 6 PM this evening to 11 AM EDT Wednesday for MEZ001>006-010-011-015>017-031-032. MARINE...Small Craft Advisory until 6 PM EDT Wednesday for ANZ050-051.