textproduct: Caribou

WHAT HAS CHANGED

- Slightly increased the chance for snow showers today, mainly to the north of the Katahdin region

- Increasing confidence on the track of the mid-week low pressure system, and placement of best chances for mixed precip types

KEY MESSAGES

1) A brief period of light snow across the north Monday morning could result in minor travel impacts, then turning unseasonably warm by afternoon.

2) Wintry mix of sleet and freezing rain across the north Tuesday night, which could create slick surfaces leading to travel hazards, particularly for the Wednesday morning commute.

3) Rapidly dropping temperatures may quickly freeze wet surfaces late Wednesday, with possible travel hazards for the Wednesday evening commute.

4) A chance for another round of accumulating snow at the end of this week as the active weather pattern continues.

DISCUSSION

KEY MESSAGE 1... A brief period of light snow across the north Monday morning could result in minor travel impacts, then turning unseasonably warm by afternoon.

KEY MESSAGE 1 DESCRIPTION... After one more unseasonably cool day today, it turns unseasonably warm Monday, as a southwest flow develops in the wake of warm frontal passage.

Low pressure will track east through Quebec province Monday with a warm front crossing the region early. A brief period of light snow is expected early Monday morning, mainly to the north of the Katahdin region, as the warm front lift to the north. Although any accumulation with this feature is expected to not be much more than an inch or so, the snow will be falling right around the commute time Monday morning. Thus, it may pose some minor travel difficulties, especially across far northern Maine and the Saint John valley.

The good news is that any snow that does fall early Monday morning will quickly melt as temperatures are expected to rise well above freezing during the afternoon ahead of an approaching cold front.

KEY MESSAGE 2... Wintry mix of sleet and freezing rain across the north Tuesday night, which could create slick surfaces leading to travel hazards, particularly for the Wednesday morning commute.

KEY MESSAGE 2 DESCRIPTION... An open wave low pressure system will approach from the west on Tuesday, with a warm front lifting northwards through the CWA Tuesday night and the trailing cold front surging through the area during the day on Wednesday. With the nocturnal warm front passage, temperatures may remain steady or could even rise through the night.

There is increasing consensus on the exact track for this low, but which path it takes could greatly influence precip types and amounts in the forecast area.

- Solution A is a low track across the center, or just north of center, of the state. This track lifts the warm front into the northern half of the CWA, then the trough orientation pivots slightly so the low moves along this stalling warm front. The result is an extended period of time with a warm nose inversion across the north, persisting the threat for freezing rain and/or sleet in this area. This is the solution most guidance has been trending towards, as seen across the GEFS, and deterministic GFS and ECMWF. The EPS members also agree with this solution, and some members even suggest the low could pass north of our forecast area entirely, which could result in all rain across the forecast area! The NBM also reflects Solution A, and was thus used as the basis for the current forecast.

- Solution B is the low sticking closer to the coast, and passing south of most of our CWA. This solution is much colder for the forecast area and would be more of a snow solution in the north, and a wintry mix for the Downeast region. That said, this solution is the least favored one, only really being seen on both the global and regional deterministic Canadian guidance. That said, the Canadian ensemble spread, though clustering along the coast, also has a secondary cluster of members that follow the same track as reflected in other guidance across the center of the state.

With consensus pointing the forecast towards Solution A, the northern half of the forecast area could see at least a glaze of ice on elevated surfaces by early Wednesday morning, with one to two tenths of an inch of ice accumulation in the realm of possibilities at this point. Sleet probabilities are low, but high enough that there could be a period of ice pellets that would reduce how much ice will accrete on elevated surfaces. This wintry mix may have significant impacts to the Wednesday morning commute in the north. Temperatures will continue to climb Wednesday morning, with most of the north changing over to warm rain through the morning. For the Bangor region and Downeast, precip type should be all rain.

KEY MESSAGE 3... Rapidly dropping temperatures may quickly freeze wet surfaces late Wednesday, with possible travel hazards for the Wednesday evening commute.

KEY MESSAGE 3 DESCRIPTION... The cold front behind the open wave mentioned above will lead to a rapid drop in temperatures Wednesday afternoon through Wednesday night. A LLJ may develop ahead of this could front, which could lead to a brief period of gusty winds Wednesday before the FROPA. If the winds are strong enough for long enough behind the stratiform rain, wet surface will have a chance to dry before temperatures crash. However, any surface which remains wet behind the FROPA could rapidly freeze, and this creates the chance for slick surfaces Wednesday evening.

KEY MESSAGE 4... A chance for another round of accumulating snow at the end of this week as the active weather pattern continues.

KEY MESSAGE 4 DESCRIPTION... Another low pressure system will approach from the southwest through the end of this week. At this time, the timing and track of this low remain quite uncertain, with guidance timing alone spreading the low arrival anywhere from Thursday afternoon to Friday night. This storm is the next chance for accumulating snowfall across the forecast area.

AVIATION /06Z SUNDAY THROUGH THURSDAY/

VFR conditions are expected today into early this evening. MVFR conditions are possible toward daybreak Monday at the Aroostook terminals in a brief period of light snow 10z to 14z timeframe. Otherwise on Monday, generally expect VFR/MVFR conditions at all terminals. SW wind 5 to 10 kt through tonight, then increasing to 10 to 15 kt with G15 kt.

Mon night...MVFR/IFR cigs at northern terminals, VFR trending towards MVFR at southern terminals. Winds light and variable.

Tues...IFR/LIFR. Rain at southern terminals, snow at northern terminals. E/NE winds 5 to 10 kts.

Tues night...IFR/LIFR. Rain at southern terminals, FZRA/PL at northern terminals. E winds 5 to 10 kts at northern terminals, SE winds 5 to 10 kts at southern terminals. Gusts to 20 kts.

Wed...IFR/LIFR with rain early, with quick drop in temperature with cold front late and rapid improvement to VFR. Southern winds with rapid shift NE with afternoon cold front 10 to 15 kts gusting 20 to 25 kts.

Wed night...VFR across all terminals. NW winds 5 to 10 kts.

Thurs...VFR early, with cigs falling towards MVFR/IFR depending on storm timing. N winds 5 to 10 kts.

MARINE

A Small Craft Advisory remains in place for the water later this morning right the day on Monday. Expect gusts up to 30 kt with seas 4 to 7 ft

Conditions will trend upwards towards gales through the day on Tuesday, becoming gales over all waters by Tuesday night. Winds will finally decrease once more Wednesday night behind a cold front. Seas 4 to 7 ft to increase towards 10 to 15 ft Tuesday night, then gradually improve through the second half of the week.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory from 11 AM this morning to 6 PM EDT Monday for ANZ050>052.