textproduct: Caribou

SYNOPSIS

High pressure will build across the region today through Sun. Low pressure then lifts through the region Mon through Wed.

NEAR TERM /THROUGH SUNDAY/

6 AM Update: Cold temperatures continue across the forecast area, particularly where upper level cloud cover remains thin, as many sites across the north have dropped to below 10 below zero this morning. Upper level cloud cover will continue to thicken over the next couple of hours, and limit surface heating today, leading to cool temperatures.

Main Point: * Cold air continues to hold onto the forecast area through the weekend

A ridge of high pressure continues to shift eastward today, while an inverted trough crosses the state into this afternoon, bringing an increase in mid to upper level cloud cover over most of the forecast area, though no precipitation is expected with this trough. With this persistent cloud cover through peak heating hours, temperatures will fail to warm much, with highs only lifting into the lower teens in the north and upper teens Downeast. Tonight, skies will clear as another high pressure enters the northern New England region, and a deep nocturnal inversion is expected to setup which will allow for efficient radiational cooling and temperatures dropping into the lower single digits above zero Downeast and potentially below zero across the north.

Complicating the temperature forecast tonight will be a deepening low pressure centered over Labrador, and the gradient between this and the high pressure centered to our west increases. This will lead to the development of an LLJ. Current forecast profiles suggest that the nocturnal inversion will be deep enough that even though winds will begin to increase late in the night, efficient radiational cooling will still allow for temperatures to quickly drop. However if this inversion fails to hold, the return of mixing will keep temperatures on the warmer side, albeit still below average for this time of the year with lows above zero but still in the single digits to lower teens. As winds increase near sunrise Sunday morning, wind chills may drop into the teens below zero across the north, and approach ten below zero Downeast.

Increased mixing heights on Sunday and a shift in air mass will allow for high temperatures to lift into the 20s to around 30 across the forecast area. Breezy winds will continue however, with wind chills remaining below 20 through the day, and leading to another cold winter day.

SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/

Key Message... 1) Significant winter storm to bring mixed precipitation, including sleet and freezing rain, Monday and Monday night.

Key Message 1... Models have trended warmer for the significant weather system Monday/Monday night, and we are looking at a very messy system with all precipitation types in play. The primary surface low pressure will be passing well north of us, but a very important secondary surface low will be tracking from west to east through our area. Models are in decent agreement on the timing and amount of precipitation now, but there is still some uncertainty on the track of this secondary low. It could track from west to east as far north as Caribou, or it could be as far south as Downeast. A more southerly track would keep the north mostly snow, while a more northerly track would bring sleet and freezing rain to the St John Valley. Going with a middle-of-the- road approach for now, with broadbrushed mixed precipitation over about the middle 3/4 of the area, with mostly rain along the coast and mostly snow in the extreme north. This could change obviously.

The onset of the precipitation from west to east should occur Monday morning into early afternoon. The warm layer aloft comes into play with or within a couple hours after the onset of precipitation, and this means the likelihood of sleet or freezing rain. With low-level winds likely to remain from the east/northeast through Monday evening, with probably some degree of cold air damming, this means that most areas W/NW/N of Bangor and Lincoln will stay below freezing and be very slow to warm while the warm air aloft moves in. Concerned enough about the threat of sleet and freezing rain that we went unusually bold for the likelihood of sleet/freezing rain this far out. One item of good news is that this is a pretty quick-hitting system, with about 12 hours of moderate precipitation of a half to three quarters of an inch for most places. This means that while there will probably be some decent sleet and freezing rain amounts somewhere in the forecast area, it's unlikely (but not impossible) there will be enough ice to lead to tree damage. While we can't rule out over 6 inches of snow for some areas, if this occurs, it would be in the far north, most likely north of Presque Isle. As we head into Monday night, many areas especially in the north will see a brief changeover back to snow before the precipitation tapers off from west to east.

LONG TERM /TUESDAY THROUGH FRIDAY/

Key Messages... 1) Below average temperatures, potentially bitterly cold, Tuesday night to Saturday. 2) Potential for more snowstorms mid to late week, but high uncertainty

Key Message 1... Colder air works in behind the Monday/Monday night storm, and arrives in earnest Tuesday night. Below average temperatures are very likely to continue into Saturday. Because of uncertainty in timing/amplitude/strength of weather systems, there is considerable uncertainty is temperatures from day to day mid to late week. The cold end of model guidance is quite cold, though (10th percentile of NBM MaxTs are around 0F in the north and around 10F Downeast, and 10th percentile of NBM MinTs are around -10F to -20F). Stayed with the deterministic NBM for temperatures, which is still plenty cold with highs 10-15F in the north and around 20F Downeast, and around 0F for lows in the north and around 5 above Downeast.

Key Message 2... Models are in poor agreement in the extended, but some models/ensembles have one or possibly two systems Wednesday night through Friday. If we do get any storms, they would be all snow and on the light to moderate side rather than heavy.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

NEAR TERM: VFR conditions will continue through today through Sunday across all terminals. N to NW light winds around 5 to 10 kts today through tonight, increasing to 10 to 15 kts on Sunday with gusts to 20 kts. NW LLWS around 40 kts likely to develop around 00z tonight from KHUL northwards, and could spread across the rest of the forecast area through the night tonight.

SHORT TERM: Sunday night...Generally VFR. Occasional MVFR possible late. A wintry mix possible late at KBGR/KBHB. Variable winds 5 to 10 knots.

Monday...VFR/MVFR early, lowering to IFR/LIFR through the afternoon. Snow transitioning to a wintry mix north, with a wintry mix transitioning to rain Downeast. Variable winds 5 to 10 knots, becoming east/southeast 10 to 15 knots with gusts up to around 20 knots.

Monday night...IFR/LIFR. Snow, or a wintry mix transitioning to snow, north. Rain transitioning to snow Downeast. East/southeast winds 10 to 15 knots with gusts up to around 20 knots, becoming west/southwest.

Tuesday...MVFR/IFR north with a chance of snow showers. VFR/MVFR Downeast with a slight chance of snow showers. West/southwest winds 10 to 15 knots with gusts up to 20 to 25 knots.

Tuesday night through Wednesday...VFR/MVFR with a slight chance of snow showers north. VFR Downeast. Southwest winds 10 to 15 knots with gusts up to 20 to 25 knots.

MARINE

NEAR TERM: Light N winds this morning will increase through the day and shift NW, with gusts building to 25 to 30 kts this afternoon. A small craft advisory is in place beginning at 4 PM this afternoon. Seas will only build to 2 to 4 ft through this time. SCA conditions will last into the day on Sunday, tapering Sunday afternoon below advisory criteria. Light freezing spray today through tonight, decreasing during the day on Sunday.

SHORT TERM: Westerly gales are very likely late Monday night into Tuesday with seas to around 12 ft. The gales and high seas could continue into Wednesday morning.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory from 4 PM this afternoon to 2 PM EST Sunday for ANZ050-051.