textproduct: Caribou

SYNOPSIS

High pressure over Quebec will build south across the region today. Low pressure crosses the region Monday then lifts north of the region Monday night into Tuesday, remaining north of the region Wednesday through Friday.

NEAR TERM /THROUGH MONDAY/

12:26PM UPDATE...Aviation update only. See below.

Previous Discussion... Key Messages: * Wintry mix on Monday to create dangerous travel conditions * Uncertainty still remains on location and amounts for greatest ice amounts

Discussion: An occluded low will approach from the west Sunday night, pulling through our forecast area Monday through Monday night. As this system crosses the CWA, a triple point low will develop and bisect our region, tracking along a line roughly from Greenville through Houlton. The development of a triple point low will aid in maintaining CAD across the north, and lifting a warm front through the area such that all wintry precipitation types will be possible. Low SLRs, combined with sleet, freezing rain, and plain rain will create a heavy layer of wintry accumulation. Ice, sleet, and slush from melting snow will create slick surfaces and lead to dangerous travel conditions, particularly across the northern half of the CWA.

There still remains uncertainty in amounts of each precip type as well as locations, as slight shifts in the temperature profile could spell a completely different story for impacts. Ice accumulation will likely remain below a quarter inch over most of the area, but there could be a tenth of an inch of accumulation along a band somewhere across the north, depending on the exact track and speed of the triple point low. Based on forecast profiles and the height of the warm nose (around 850 mb), sleet may end up being a greater threat in the north, with pure sleet amounts approaching at least one inch. With how far north the warm air is intruding, snow amounts will be on the lighter side, generally less than 4 inches. Coastal Downeast has the greatest chance of remaining all rain, though it is possible a dry slot stemming from the triple point low could create a pause in rain through Monday afternoon that may cut current rain amount projections in half should this dry slot come to fruition.

There is also question as to how long a low level dry layer will linger at storm onset through the area. If this dry layer takes longer to saturate than guidance currently suggests (and is often the case in patterns such as this one with very cold air prior to the storm) then precip start times will be later, potentially not starting until Monday afternoon. A stronger dry layer would also introduce additional evaporational cooling that currently is not captured by guidance, and may shift precip types colder at onset, leading to more snow and sleet than freezing rain and plain rain. Downeast, terrain allows for warmer, moisture air to more quickly rush into the region, however a snow pack currently lingers in this area and may help keep the near surface layer cold enough to support more freezing rain than is currently in the forecast.

SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/

Key Messages: *Wintry mix continues Monday night, ending on Tuesday *Gusty winds Tuesday into Tuesday night

Key Message 1... Triple point low pressure system continues to swing through New England, with snow prominent in the far north, a wintry mix prominent from Van Buren to just south of Houlton, and rain prominent in the interior Downeast and coastal regions. As the associated front passes through Maine and colder air begins to work in behind the frontal system, wintry mix transitions over to snow in the north, and rain is confined to the immediate Downeast coastline. Overnight, potential for 4 inches of additional snowfall in the Crown of Maine, and roughly 1 to 3 inches in northern Maine and portions of the central Highlands. North and Crown of Maine could see a quarter to half an inch of sleet overnight. Highest totals for ice accumulation are anticipated in northeast Maine overnight, around 0.1 to 0.2 inches of accumulation. The rest of northern Maine could see a trace to 0.1 inches of ice. Precipitation chances decrease of front moves into New Brunswick. Temperatures quickly drop into the lower 20s in the north, and mid-20s Downeast. This could cause any residual moisture from recent rainfall to freeze over, causing some slick spots, so exercise caution when traveling. Exact snow/sleet/ice totals with this system are subject to change based on the storm track, as a northerly track will result in more sleet in the north, while a southerly track will wrap in more cold air, leading to larger snow totals. So continue to monitor the forecast for updates.

Key Message 2... Pressure gradient force associated with passing low pressure system resulting in wind gusts 25-30 mph possible Tuesday into Tuesday night. Winds generally from the west. Gusts stay elevated until gradient relaxes on Wednesday.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

Key Messages... *Cold temperatures through the weekend *Potential for system late next week

Key Messages 1... Behind the aforementioned frontal system Monday into Tuesday, a few shortwave disturbances could move through Maine, bringing a slight chance for some light snow showers in the north. Cold temperatures linger Wednesday through the weekend, with daytime highs staying in the low teens in the north, and the teens to 20s Downeast. Overnight lows around or below zero in the north, and generally in the low teens Downeast. Wind chills in the negative teens overnight could be possible late this week in the north.

Key Message 2... Next chance for some significant precipitation will be early this upcoming weekend, as a low pressure system from Central Canada moves south closer to western Maine. The EURO model shows the primary low swing just north of Maine, with little to no precipitation, but the GFS has a coastal low develop off of the parent low in Canada, bringing a chance for precipitation throughout the state. Kept precipitation chances around a slight chance to chance, until models get in better agreement.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

NEAR TERM: 18z TAF UPDATE...VFR this afternoon with SCT high cigs working into the area. NW winds 5-15kt with gusts up 20kt especially northern terms. Winds go light and variable tonight. VFR this evening with increasing high cigs and slowly lowering. By early Monday AM most sites falling to MVFR cigs and then IFR cigs by daybreak. -SN developing S to N tomorrow with sites turning IFR/LIFR with -SN. -SN will transition to SNPL north and quickly SN to RASN and then RA south. SE winds 10-15kt with gusts up to 20kt. LLWS likely southern terms. Tomorrow will be SNPL and FZRA north terms and SN going to RA southern terms.

SHORT TERM: Monday night...IFR/LIFR. Snow, or a wintry mix transitioning to snow, north. Rain transitioning to snow Downeast. E/SE winds 10 to 15 knots with gusts up to around 20 knots, becoming W/SW.

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

Wednesday night through Thursday...VFR/MVFR, occasional IFR. A chance of light snow or snow showers. S/SW winds 5 to 10 knots, becoming W/SW Wednesday night. W/SW winds 5 to 10 knots, becoming variable Thursday.

MARINE

NEAR TERM: Gusts 25 to 30 kts continue over the coastal waters this morning, gradually tapering off through the day today. Seas that are topping out at around 5 ft will also decrease today as well, and conditions should fall below SCA levels this afternoon. Light freezing spray will continue through this morning as well, before temperatures warm enough to reduce this threat this afternoon. Light winds return tonight before SE winds increase through the day on Monday with a low pressure system moving through the area, approaching gale strength towards the end of the day on Monday. The low pressure system will likely bring all rain over the waters on Monday and rain could limit visibility.

SHORT TERM: Gale Watch in effect for late Monday night into Tuesday night. Light freezing rain Tuesday through Tuesday night. Rain over the waters on Monday night, and snow on Tuesday. Seas gradually rise up to 12 ft by Tuesday. Winds from the S/SE on Monday night, shifting to the W by Tuesday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Winter Storm Watch from Monday morning through late Monday night for MEZ001-002. Winter Storm Watch from Monday morning through late Monday night for MEZ003>006-010-011-031-032. MARINE...Gale Watch from late Monday night through Wednesday morning for ANZ050>052.