textproduct: Caribou

WHAT HAS CHANGED

-Increased confidence in dangerously cold wind chills this weekend

-Increased confidence in a significant winter storm Sunday night through Monday night. There has generally been a northern trend in the storm track, which brings more snow to Eastern Maine. A winter storm watch has been issued from Houlton, Patten, and Greenville south to the coast.

KEY MESSAGES

1) Heavy snow showers and snow squalls possible this afternoon across much of Maine.

2) Frigid arctic air moves in tonight and persists through the weekend bringing dangerous wind chills.

3) Increased confidence in a significant winter storm to impact the area Sunday night through Monday night, with the higher snow totals over southern portions of the area.

4) Remaining colder than average through late in the week.

DISCUSSION

KEY MESSAGE 1...Heavy snow showers and snow squalls possible this afternoon across much of Maine.

KEY MESSAGE 1 DESCRIPTION... Current radar shows snow showers already developing across northern and central Maine in association with an arctic cold front. These are expected to continue through the afternoon before drier, colder air moves in behind the front. Expect snow showers over much of Maine, steadily progressing east through late afternoon. The environment is conducive for any snow showers to hit snow squall criteria of a quarter mile visibility and 30 mph winds. Ample surface heating this morning has destabilized the low levels and contributed to the development of up to 50 J/kg of CAPE and a deep mixed layer up to 700mb. Within the mixed layer, strong winds in excess of 30 mph are evident on analysis soundings which can easily be mixed down to the surface. The gusty winds in combination with heavy snow may lead to rapidly changing driving conditions including whiteouts and slick roads.

KEY MESSAGE 2...Frigid arctic air moves in tonight and persists through the weekend bringing dangerous wind chills.

KEY MESSAGE 2 DESCRIPTION... Behind the arctic front exiting to our east this evening very cold air will surge into the area resulting in well below normal temperatures through the weekend. A pressure gradient between low pressure moving off to the northeast and high pressure building in from the west will contribute to gusty winds through Saturday, contributing to dangerous wind chills. The coldest wind chills are expected late tonight into Saturday morning as low as -30 to -40 in the north and -20 to -30 further south. Temperatures warm slightly during the day on Saturday but may not get above 0 over northern Maine. Since winds will remain elevated throughout the day, expect a very cold day with wind chills not making it above -10 areawide.

Winds relax Saturday night to a light breeze which should contribute to slightly improved wind chills but temperatures will be a few degrees colder than tonight due to the reduced mixing. Still, some uncertainty regarding how light the winds Saturday night will be which will depend on how quickly the high moves in overhead. Current thinking is that most areas will not full decouple but places where there is sheltering from the wind and skies remain clear, such as river valleys, may see temperatures dip below guidance.

KEY MESSAGE 3...Increased confidence in a significant winter storm to impact the area Sunday night through Monday night, with the higher snow totals over southern portions of the area.

KEY MESSAGE 3 DESCRIPTION... We have enough confidence to go ahead and issue a winter storm watch for southern portions of the area from Sunday night to Monday night, which covers areas along and south of a Houlton/Patten/Greenville line. The general model trend had been shifting the track of the system northward with more snow making it as far north of our area. Within the last 12-24 hours, model trend has slowed and seem to be settling into this further north track. This looks like a prolonged storm, with an elongated surface low/trough moving east near the southern end of the Gulf of Maine, and moist upper level southwest flow. We should easily be far enough north for precipitation type to be all snow, and the snow will be on the fluffy/low density side, with snow ratios 15-20:1. Winds will be from the northeast most of the storm, shifting to the northwest at the end Monday night. It will be breezy with winds generally 10-15 mph, but not windy, and think winds will be enough for some patchy blowing snow but nothing too bad and not approaching blizzard conditions. Temperatures will be cold through the event, with readings 0-10 above in the north and 5-15 above Downeast.

Confidence overall is fairly high for the storm still being so far out. In particular, confidence is high for heavy snow Downeast, with a very high probability of getting at least 6 inches, and even around a 50 percent chance of getting a foot. Further north, that's a tougher call, as any north or south wobble to the storm track will impact totals for Northern Maine. While far Northern Maine is likely to see at least an inch, it's tougher to say how much more than that there will be. For the far north, there's still a possibility of as much as a foot, but also a good possibility of just 1-3 inches. Please keep in touch with the latest forecasts.

KEY MESSAGE 4...Remaining colder than average through late in the week.

KEY MESSAGE 4 DESCRIPTION...Temperatures are very likely to remain well below average through at least Thursday, with highs somewhere between 5 and 15 above in the north and 10 and 20 above further south. Low temperatures generally 0 to 15 below. Generally dry Tuesday through Thursday other than perhaps a few snow showers. More uncertainty toward Friday though, as some models have a Nor'easter potentially impacting us. Roughly 75 percent of solutions have this system staying out to sea with little/no snow, but a few do have impacts. Some other models have some light snow moving in from the northeast along with slightly less cold air from the Canadian maritimes. Something to watch.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

This afternoon...Mainly VFR with some occasional IFR due to snow showers. BLSN also possible but not expecting significant reductions in visibility. W winds 10 to 15 kts with gusts 20 to 25 kts.

Tonight...VFR. LLWS possible. N/NW winds 10 to 15 kts with gusts up to 25 kts.

Saturday through Saturday Night...VFR. W/NW winds 10 to 15 kts with gusts up to 25 kts decreasing to 5 to 10 kts overnight.

Sunday...VFR with light winds.

Sunday Night through Monday Night...Deteriorating to IFR or worse from SW to NE Sunday night to Monday morning, with snow. Some question as to whether the IFR can make it to PQI and points north based on uncertainty in the track of the weather system. Conditions improve back to MVFR/VFR from W to E late Monday night. Winds NE 10-15 kts, switching to the NW late Monday night.

Tuesday through Wednesday...MVFR/VFR with W/NW winds 5-15 kts, stronger during the daytime hours.

MARINE

Gales on all waters through tonight, decreasing to SCA conditions on the inner waters early Saturday then on the outer waters Saturday afternoon. Below SCA conditions on the inner waters Saturday night, remaining above SCA criteria on the outer waters through early Sunday. A period of heavy freezing spray from around midnight tonight through early Saturday afternoon.

NE to NW gales very likely late Sunday night to Monday night, eventually decreasing to small craft probably Tuesday afternoon. Small craft NW winds likely to persist through Wednesday. Light to moderate freezing spray all the way through Wednesday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Extreme Cold Warning from 1 AM to 10 AM EST Saturday for MEZ001>006-010-011-031-032. Winter Storm Watch from Sunday evening through late Monday night for MEZ005-006-010-011-015>017-029>032. Cold Weather Advisory from 1 AM to 10 AM EST Saturday for MEZ015>017-029-030. MARINE...Gale Warning until 1 PM EST Saturday for ANZ050-051. Heavy Freezing Spray Warning from 11 PM this evening to 1 PM EST Saturday for ANZ050>052. Gale Warning from 7 PM this evening to 7 AM EST Saturday for ANZ052.