textproduct: Caribou

SYNOPSIS

High pressure builds into the area through Monday. The high exits east Monday night, followed by a weak low passing to the south on Tuesday. Another low approaches from the west Tuesday night, moves near the Maine coast on Wednesday, then exits over the Maritimes through Thursday. Another low approaches from the west on Friday.

NEAR TERM /THROUGH MONDAY NIGHT/

930pm Update... As mentioned in the previous update, clouds are hanging around for many places and making the temperatures slow to drop. Warmed overnight low temperatures for hills/slightly higher terrain, but kept the valleys how they were, thinking we should still clear out late tonight. Also slowed the fall of temperatures in the hourly forecast. Additionally, put in flurries for the next couple hours in the north, as we are seeing a few flakes flying at the office. No accumulation expected as these flurries are really light.

620pm Update... Actually an extraordinarily difficult forecast tonight for sky cover and temperatures. We have a strong inversion aloft from about 850mb to 725mb that is capping the altostratus clouds and locking them in place. Models are virtually all doing terribly at capturing the inversion and thus the clouds, and most models have us clear/mostly clear when in fact it's cloudy north of Bangor with clouds spreading south and probably getting into more areas this evening. The question is whether or not these clouds can dissipate and allow us to cool off, or will they persist all night and make for a much less cold night than anticipated. Think that clouds will persist at least through midnight, and raised temperatures/sky cover especially over the north to about 2am. However, still banking on some clearing late in the night that will allow temperatures to plummet, and left temps/sky alone after 2am. Another factor is a bit of a NW wind just off the surface (more than was present this morning) that will allow hilltops to not cool off too readily anyway, and that should limit any frigid 20 below or colder temperatures to valleys.

Key Message: * Very cold temperatures tonight falling to 20 to 30 below zero across the north, and to around 10 below zero in the Bangor and Downeast regions.

Discussion: High pressure gradually shifts eastward through the night tonight, relaxing the pressure gradient aloft and allowing for surface decoupling overnight. Clear skies will allow for effective radiational cooling as temperatures plummet at least as cold as the previous night, with lows at least to 20 below over most of the North Woods up through the St John Valley, and potentially making a run for 30 below zero, especially in protected river valleys which may decouple earlier.

High pressure will slowly shift eastward through the day on Monday, though arctic air will remain in the area with highs only in the single digits above zero in the north and lower teens Downeast. Monday night a low pressure system will begin to approach the area, with a tightening of the pressure gradient for a slight increase in winds as well as cloud cover, limiting surface decoupling threat and allowing for temperatures to be a little warmer, around 10 below in the north and single digits above zero Downeast.

SHORT TERM /TUESDAY THROUGH WEDNESDAY/

Key Messages -Warmer temperatures move in Tuesday and Wednesday -Low pressure system moves across the south Tuesday night and Wednesday

For Tuesday, the upper level trof moving out of the region should allow the warmer airmass from the south to move in. Increasing clouds and warmer air should push temps into the mid to upper teens in the north and 20s in the south. The main concern will be the system moving into New England Tuesday night through Wednesday.

For the ensemble models, this looks to be another day of inconsistent runs. So far, there has been a trend of a further south track over the waters for the European ensemble models with some members more aggressive with the south track. In addition, the European ensembles develop the center of the low faster and have it exiting the waters by Wednesday afternoon.

However, the GFS, ECMWF, and CmC ensembles have a slower track with the center of the low moving across the Downeast. Also, a much slower exit of the low by Wednesday night.

The NBM seems to be a fairly good blend of the ensembles with more snow in the north and rain in the south. As of this update, the NBM shows very little mixed precip with the transition line due to the slower warm air advection in the mid levels. However, cannot rule out some sleet and/or freezing rain as the warmer airmass moves northward with very little accumulation.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

Key Messages -Warming trend through the rest of the week -Possible large low pressure system by the weekend

A large surface ridge should move into the region by Thursday, bringing in the warmer airmass from the tropics and boosting temps to above normal for the rest of the week. By Friday, extended models show a large cold front moving through the region. As of this update, models show the cold front attached to the warm front of the next low pressure system moving across the plains. This should keep temps above normal through the weekend. This large low pressure system is shown to track NE across the Great Lakes as an occlusion with a triple point over New England. The ensembles show more agreement with a system moving in, but the track and timing are very inconsistent.

AVIATION /02Z MONDAY THROUGH FRIDAY/

NEAR TERM: Mainly VFR conditions continue tonight through the day on Monday and into Monday night. Some BKN-OVC ceilings tonight at times, but these are generally around 5K AGL which puts them in the VFR category. Can't rule out a brief period of MVFR cigs Monday evening mainly BHB/BGR. Light NW winds less than 10 kts.

SHORT TERM: Tuesday-Tue night...VFR north, VFR/MVFR south in snow showers. Light and variable winds.

Wednesday...MVFR/IFR in snow north and rain south. Variable winds 5-10 kt.

Wed night-Thu night...VFR. WNW winds 5-10 kt. Then light S winds Thu night.

Friday...MVFR/IFR in rain/snow. SSW winds 5-10 kts.

MARINE

NEAR TERM: Winds may increase slightly overnight with wind gusts to 25 kts on the coastal waters, and a small craft advisory is in place through the night. Very cold air over the waters combined with these winds will result in the threat for moderate freezing spray as well. Winds diminish again Monday morning with seas 1 to 2 ft Monday through Monday night.

SHORT TERM: Winds and seas should remain below SCA levels Tue through Wed. Wed night could see SCA winds in the outer waters, then decreasing Thu morning. Sea should remain SCA levels through Thu. SCA winds return Fri afternoon.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Cold Weather Advisory until 9 AM EST Monday for MEZ001>004-010. MARINE...Small Craft Advisory until 10 AM EST Monday for ANZ050-051. Freezing Spray Advisory until 10 AM EST Monday for ANZ050>052.