textproduct: Caribou

WHAT HAS CHANGED

-Updated aviation section to reflect 0Z TAFs

-Lowered snow amounts slightly for the storm late tonight and Saturday.

-Confidence continues to increase in a moderate to potentially high impact event Late Sunday night into Tuesday.

KEY MESSAGES

1) A moderate snowfall of 3 to 6 inches for all of the area will occur late tonight through Saturday, impacting travel, especially Saturday morning.

2) Multiple hazards are possible due to a complex storm system impacting the area from Sunday night into Tuesday. These include winter driving hazards Monday morning across the North. The following impacts are possible Monday into Tuesday: possible isolated to maybe scattered power outages, possible flooding area wide Monday, and possible high surf/erosion/coastal flooding.

DISCUSSION

KEY MESSAGE 1... A moderate snowfall of 3 to 6 inches for all of the area will occur late tonight through Saturday, impacting travel, especially Saturday morning.

KEY MESSAGE 1 DESCRIPTION... An upper level shortwave trough will move east through the area, along with a surface low tracking east through Downeast Maine. This will bring a fairly brief period of snow, 3 to 6 inches worth, mainly late tonight to mid-morning Saturday Downeast, and persisting into roughly early/mid Saturday afternoon in the north. This will be a particularly quick- hitting storm Downeast, with only six hours or so of snow just ahead of the surface low pressure tracking through the area. That said, snow rates look more impressive Downeast than the rest of the area and could near 1 inch per hour around dawn Saturday. From mid-morning onward, warmer air and lighter precipitation should work into Downeast, with temperatures in the mid to upper 30s. The best shot of snowfall reaching the higher end of the 3 to 6 inch range is over central portions of the area just north of the probable low pressure track, likely from Houlton to Millinocket to Dover- Foxcroft. That said, amounts over the whole area look relatively uniform and confidence is fairly high in totals. It should stay all snow over central and northern portions of the area, though temperatures rise to around 30 by about midday, so even though snow will still be falling, roads may not be too bad. Snow will be a bit on the wetter/denser side Downeast, and about an average density in the north or perhaps slightly on the wetter side. Little blowing snow is expected, though can't rule out some very localized light blowing in agricultural areas of the north. No freezing rain or sleet expected. The storm generally kicks out Saturday night, though some snow showers could persist in the north with perhaps a little more light accumulation.

KEY MESSAGE 2...Multiple hazards are possible from Sunday night into Tuesday. These include winter driving hazards Monday morning across the North. The following impacts are possible Monday into Tuesday: Possible flooding for all but the North Woods, possible isolated to maybe scattered power outages - best chance Downeast, and possible high surf/beach erosion/ coastal flooding. Heavy snow showers are also possible Tuesday afternoon.

KEY MESSAGE 2 DESCRIPTION... Deep layered ridging over the area Sunday night gives way to an approaching cutoff low over the Great Lakes Monday, this system tracks to east of Hudson Bay on Tuesday as it weakens. At the surface low pressure tracks across the Great Lakes Sunday night with its surface warm front approaching, the low progresses into southwest Quebec Monday, with its warm front lifting to the north. The low lifts into Central Quebec Monday night, then into Labrador on Tuesday, bringing its associated potent cold front across the region.

Precipitation starts off as snow mainly after midnight Sunday night, then changes to a wintry mix to rain from south to north into Monday morning. Before it does so, there is the chance this wintry mix could impact the Monday morning commute across the North.

A combination of diffluent flow aloft from late Sunday night into Tuesday morning, coupled with the slow passage of a 65-80kt 950-850 mb low level jet during most of this time frame, will produce a prolonged period of heavy rainfall across the region. Currently there is at least a 50 percent chance of over 1" of rainfall from Monday morning through Tuesday night along and south of a Mars Hill to Moosehead Lake line and a 20-40% chance of over 2" of rain across most of Downeast Maine. This coupled with snow melt, and possible ice jams over Downeast Maine and possibly the Bangor/Penobscot Region, could bring the risk of the flooding of small streams and creeks and known poor drainage areas for all but the North Woods, with the highest threat over Downeast Maine. In alignment with this, the Weather Prediction Center has placed areas south of a line from Van Buren to Clayton Lake in a marginal risk for excessive rainfall, with at least a 5 to less than 15 percent chance of rainfall exceeding flash flood guidance.

The prolong duration 950-850 mb jet could bring strong wind gusts to most of the region, with most of the area having at least a 40% chance of wind gusts over 45 mph, the possibility for damaging wind gusts has gone down over the past 24 hours with the chance for wind gusts over 55 mph down to 20-30 percent over the islands on the Downeast Coast. As a result have the potential for widespread isolated power outages, with a low end chance for scattered power outages over the coastal Downeast Maine.

Last but not least, prolonged period of strong S-SE winds of 30-40 mph sustained along the coast could bring high surf and possible beach erosion from Monday into Tuesday morning, as well as an increasing chance of minor coastal flooding over successive high tide cycles from Monday morning through Tuesday morning.

Finally, there is the potential for strong convection both immediately ahead of the cold front on Tuesday and behind it Tuesday afternoon/early Tuesday evening. The former could locally enhance rainfall and bring the strongest local wind gusts and the latter could end up being in the form of locally heavy snow showers depending on how fast low level cold air moves in behind the system.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

Tonight: VFR early, deteriorating to MVFR/IFR aft 06z in developing snow. Light E wind increasing to 5 to 10 kt.

Saturday: Widespread MVFR/IFR in snow. E to NE wind around 10 kt becoming NW late afternoon.

Saturday Night: MVFR possible early in -SN, otherwise trending to VFR. N to NW wind 5 to 10 kt.

Sunday-Sunday evening: VFR.

Late Sunday night: IFR/LIFR developing. Snow to a wintry mix northern terminals, snow to rain southern terminals. SE winds G15-25KT possible. LLWS likely southern terminals.

Monday-Tuesday morning: IFR/LIFR, possible VLIFR. Locally heavy rain probable. LLWS likely. SE winds G20-30KT possible, with gusts 40+KT possible in any stronger convection Tuesday morning.

Tuesday afternoon: Becoming VFR. Chance for locally heavy snow showers. WSW-W winds G15-30KT possible.

Tuesday night-Wednesday: VFR. W winds G20-30KT probable.

MARINE

Winds this evening increase to small craft levels from the south. Late tonight, there could be a brief period of southeast gales, but opted for a small craft advisory instead for now. Winds switch to the west on Saturday and remain small craft, then become northwest Saturday night. Seas 3 to 6 feet building to 5 to 9 feet Saturday afternoon and only slightly diminishing Saturday night.

SCA conditions likely on the waters Sunday and again late Sunday night, with a possible lull Sunday evening. Gales develop on all waters Monday, with Storm Force winds gusts probable on the coastal ocean waters and possible on the intra- coastal waters Monday night, with the Storm Force winds possible lingering into Tuesday on the coastal ocean waters. Conditions then subside to Gales over the coastal ocean waters and SCA levels on the intra-coastal waters by Tuesday night. Sub-SCA conditions forecast for Wednesday on the intra-coastal waters, with SCA level seas likely lingering through Wednesday on the coastal ocean waters.

Seas build from late Sunday night into Tuesday to near 20 ft on the coastal ocean waters and around 10 ft on the intra- coastal waters, then gradually subside through Wednesday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory from 6 AM to 7 PM EDT Saturday for MEZ001>006. Winter Weather Advisory from 2 AM to 2 PM EDT Saturday for MEZ010-011-015>017-029>032. MARINE...Small Craft Advisory until 8 AM EDT Sunday for ANZ050>052.