textproduct: Caribou

WHAT HAS CHANGED

With This Update: Increased cloud cover based on satellite trends showing clouds remaining in place longer than models indicated. A corresponding increase in low temperatures was made, especially over northwestern areas.

With the PM Forecast Package Earlier Today: Added chance of freezing drizzle to the forecast for Friday morning. Issued a special weather statement highlighting the potential for icy travel late tonight into Friday.

Confidence increasing in main storm track shifting south with Winter Storm from Saturday night through Sunday night. Increasing confidence in moderate snowfall across the North, and in any wintry mix being confined to Downeast Maine.

KEY MESSAGES

1) Freezing fog tonight with possible freezing drizzle Friday morning, becoming all rain from south to north midday Friday to early Friday evening. Travel impacts possible.

2) Potential for strong gusty winds Friday afternoon into early Saturday morning. This could bring down some larger tree limbs and branches.

3) Winter Storm Saturday Night through Sunday night could make travel difficult, especially across the North.

DISCUSSION

KEY MESSAGE 1... Freezing fog tonight with possible freezing drizzle Friday morning, becoming all rain from south to north midday Friday to early Friday evening. Travel impacts possible.

KEY MESSAGE 1 DESCRIPTION... High pressure overhead this evening should allow patchy fog to form mainly after midnight. Anywhere this fog forms could be subject to icy roads. Southerly flow develops late tonight into Friday morning ahead of the next system, and as the low cloud layer thickens, there's a time window from about 6am-10am when we could see some freezing drizzle. Not confident enough in the freezing drizzle occurring to issue a winter weather advisory, but opted to issue a special weather statement instead to highlight the threat of freezing fog and freezing drizzle. Really anywhere in the area is susceptible to the freezing fog and freezing drizzle.

Temperatures first creep above freezing along the coast around mid-morning Friday, get above freezing near Bangor around midday, then near or just above freezing in far northern Maine late afternoon/early evening. However, steadier precipitation will be moving in during the afternoon, and while the precipitation will be light (about a quarter inch expected most places Friday afternoon/evening), it could be impactful to travel conditions even after temperatures have risen above freezing. Since it has been so cold, many roads, especially side roads will take time for road temperatures to rise above freezing and we will likely see regular rain with temperatures in the mid 30s acting like freezing rain on some surfaces. In the north, the PM precipitation will be a smorgasbord, with all types in play: snow, sleet, freezing rain, rain. We don't expect much of any one type, with snow less than one half inch, sleet a tenth or two of an inch at best, and freezing rain less than 0.05. That said, it doesn't take much to cause travel issues. Side roads could stay treacherous into Friday evening even with temperatures above freezing areawide. There will be a significant slip and fall hazard on driveways and sidewalks.

The precipitation tapers off from west to east Friday night behind a cold front. Air behind the cold front isn't that cold though, and only expect temperatures dropping back to around freezing late Friday night.

Winds from the south increase late Friday afternoon and evening to around 15-20 mph with gusts 25-30 mph. We don't expect significant impacts from these winds. The cold front passes Friday night and winds switch to the west. Winds behind the front look a bit stronger than before the front, and we should be seeing gusts 30-35 mph with a few gusts to 45 mph possible mainly for hilltops.

KEY MESSAGE 2... Potential for strong gusty winds Friday afternoon into early Saturday morning. This could bring down some larger tree limbs and branches.

KEY MESSAGE 2 DESCRIPTION... Winds from the south increase late Friday afternoon and evening to around 15-20 mph with gusts 25-30 mph. We don't expect significant impacts from these winds. One wildcard is the removal of ice and snow on branches, which is bending over branches in many places presently mainly in the north. As the winds pick up and temperatures rise, snow/ice will melt off branches, the branches could spring upward and potentially cause very localized issues.

A cold front moves through around or a little after midnight Friday night. Winds then shift to the W-WNW behind the cold front for Saturday morning. Low level winds range from 30 kt at 950 to 60 kt at 850 mb. With low level lapse rates 7-8 degrees C/km, there is the potential for wind gusts to near advisory level around/just after 12z Saturday, especially over higher terrain across the North.

KEY MESSAGE 3... Winter Storm Saturday Night through Sunday night could make travel difficult, especially across the North.

KEY MESSAGE 3 DESCRIPTION... Confidence is increasing in the track of the coastal low being solidly to the south with this system.

A positively tilted cutoff low tracks across the Great Lakes Saturday night, with a combination of low level warm air advection and a 700 mb shortwave passing off the mid Atlantic coast, helping to develop a coastal low south of Long Island Saturday evening, that tracks to ENE of Cape Cod by Sunday morning. This cutoff low tracks to just west of Montreal by Sunday evening, with the surface low tracking to western Nova Scotia. This cutoff low then tracks across Maine Sunday night, and into Eastern New Brunswick/SW Gulf of Saint Lawrence by Monday morning, as it develops a more neutral tilt.

Based on this track, coupled with some cold air damming ahead of the surface low, expect precipitation to develop from SW to NE, from mainly after midnight Saturday night into early Sunday morning. This should be in the form of snow, except near the immediate Downeast Maine coast, where a wintry mix is expected. During the day on Sunday, the wintry mix expands to cover all of coastal Downeast Maine and possibly into central Hancock and south central Washington County, with a slight chance of moving into Bangor by late Sunday afternoon. The wintry mix then changes to all snow, even at the coast Sunday evening as cold air is advected in on the backside of the low. The snow then tapers off from W to E Sunday night as the surface and upper low exit to the ENE.

At this time, there is increasing confidence in moderate snowfall across at least portions of the North, though the northern extent of this is uncertain, especially if the storm track continues to adjust to the south) from late Saturday night through Sunday night. There is also some potential for moderate snowfall across the Bangor/Penobscot Region and interior Downeast Maine depending on exactly how far north any wintry mix ends up getting. If the storm track remains about this far south or even more to the south, the confidence in moderate snow in this region will increase. At this time, it appears most likely that only a few inches of snow will fall across coastal Downeast Maine.

Even with a persistent shore parallel to slightly onshore flow, Saturday night into Sunday evening of around 15-20kt with gusts 25-30kt, tidal departures of only a foot, coupled with tidal ranges heading to a minimum for the month should preclude any coastal flood threat or risk of beach erosion. Winds shift offshore later Sunday evening.

Lows Saturday night should be around 15 degrees above normal, highs on Sunday around 5 degrees above normal and lows Sunday night around 10-15 degrees above normal.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Tonight...Generally MVFR tonight initially, with KBGR and KBHB on the edge of the low cloud deck. Then we could see an IFR or possible LIFR ceiling develop with -FZDZ or FZFG. Due to MVFR cigs persisting longer than model projections, confidence is low in when, or even if, this low ceiling develops. The timing will most likely be after 6z given current trends, and it was addressed via a PROB30 for most TAF sites. Light winds tonight.

Friday...Mostly IFR with pockets of MVFR. -FZDZ or FZFG possible in the morning (roughly 30 to 40 percent chance). Any PM precipitation at southern terminals like BGR/BHB will be rain, but northern terminals could be any precipitation type including rain, freezing rain, sleet, or snow. Precipitation will be fairly light however. Light S winds in the morning increasing in the afternoon to around 10 kts with gusts to 20 kts. LLWS developing after 18z.

Friday Night...IFR/LIFR to start out, improving to MVFR/VFR mainly after 6z. South winds around 15 kts with gusts 20-30 kts in the evening, shifting to the west after 6z and remaining gusty. LLWS Friday evening.

Saturday-Saturday evening: VFR. NW winds G25-30KT probable in the morning, NW winds G15-25KT Saturday afternoon.

Late Saturday night-Sunday night: IFR or lower becoming likely late Saturday night/early Sunday morning. Mainly snow along/N of a Bangor to Calais line, with a wintry mix south of there. ENE winds 15-25KT possible Sunday. NW winds G15-30KT possible Sunday night.

Monday: Becoming VFR throughout. WNW winds G15-25KT possible.

Monday night-Tuesday: Chance of MVFR. WSW winds G15-20KT possible Tuesday.

MARINE

Tonight through Friday night: Conditions below small craft levels through Friday morning. However, south winds increase Friday afternoon and are likely (75 percent chance) to be around gale force Friday night. Have issued a gale watch for Friday night. The south winds switch to the west late Friday night but remain gusty. Seas will peak as high as 9 ft late Friday night.

Saturday through Tuesday: Gust to gale force are possible on the coastal ocean waters Saturday morning, but confidence is not high enough to have this time frame in a gale watch at this time, SCA conditions likely on the intra-coastal waters. Conditions improve to sub-SCA on all waters Saturday afternoon. SCA conditions should return on the coastal ocean waters Saturday night and continue into Sunday, with conditions just below SCA levels on the intra-coastal waters. SCA conditions on all waters Sunday evening, then gales probable on the coastal ocean waters and possible on the intra coastal waters late Sunday night and Monday. Conditions should become SCA throughout Monday evening, with SCA conditions probably lingering through Tuesday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Gale Watch from Friday evening through Saturday morning for ANZ050>052.