textproduct: Caribou

WHAT HAS CHANGED

Have cancelled the winter weather advisory for Central and Southern Piscatiquis County as the area of freezing rain has shifted south.

For Friday morning, we have introduced a chance of freezing drizzle to the forecast for most areas.

For Saturday night and Sunday, confidence is increasing on a fairly significant weather system.

KEY MESSAGES

1) Light snow across the North, with a wintry mix across Downeast Maine and the Bangor/Penobscot Region from late tonight into Wednesday Evening

2) Light Rain with Possible Freezing Drizzle Friday

3) Potential Winter Storm Saturday Night and Sunday

DISCUSSION

KEY MESSAGE 1...

Light snow across the North, with a wintry mix across Downeast Maine and the Bangor/Penobscot Region from late tonight into Wednesday Evening...

A northern stream shortwave tracks from the eastern Great Lakes to eastern upstate New York tonight, moves across the Gulf of Maine Wednesday, then exits into the southern Maritimes Wednesday night. This upper system supports the development of a secondary low over the southwestern Gulf of Maine by Wednesday morning, which as it continues to deepen, tracks to eastern Nova Scotia by Wednesday evening, then continues to slowly tack into the southeastern Maritimes Wednesday night.

This track as a bit farther south than previous forecasts, as a result, there is less precipitation forecast over the area and the northern extent of any wintry mix has shifted to the south as well. Based on this, now only expect 1-3" of snow over zone 10, and no freezing rain, so have cancelled the winter weather advisory for Central Piscatiquis County with this issuance.

Precipitation will develop from SW to NE starting late this evening through early Wednesday morning. Initially the entire column will support snow over all but coastal Downeast Maine, where precipitation should start as a wintry mix. The wintry mix should push north into Northern Hancock/Central Washington County and far SE Penobscot county Wednesday morning, as coastal Downeast changes to all rain. The wintry mix area then expands slightly to the north/west to near a Bangor to Topsfield line by midday Wednesday, with a wintry mix continuing in this area into Wednesday evening, before tapering off. To the north of this area, only a light snow is expected from late tonight into Wednesday evening (should only last into the evening along the US 1 corridor near the eastern border with Canada). Generally 1-2" of snow is expected in this area, with up to 3" possible in the Central Highlands. In the wintry mix area, up to 2" of snow is possible (less than 1" across most of Downeast Maine) with up to 1/10th of an inch of ice accumulation. In areas where the winter weather advisory was issued for the wintry mix, no change in headlines is needed.

Little in the way of wind is expected with this system, so the winds should not exacerbate the impacts of any freezing rain.

As noted above, with the reduced snow totals expected, did cancel the winter weather advisory for zone 10. Noting that a slight wobble of the track to the north could result in more snow than currently forecast, especially over zone 31, have left the advisory up for southern Piscatiquis County for now. If confidence in this more southern track increases further, this headline may be dropped in future updates.

Lows tonight will be near normal (mid to upper single digits to mid 20s), but occur mainly in the evening (South)/early overnight hours (elsewhere) before holding steady, then slowly rising. Highs Wednesday should be 5-10 degrees above normal (upper 20s to upper 30s) - did blend in NBM50 with NBM temperatures to reduce highs with precipitation and offshore flow. Lows Wednesday night should be 10-15 degrees above normal (mid teens to mid 20s).

KEY MESSAGE 2... Light Rain with Possible Freezing Drizzle Friday...

Much warmer weather is on the way Friday, but before it gets above freezing, we do have a concern for freezing drizzle. This most likely would occur late Thursday night into Friday morning, with temperatures eventually getting above freezing from south to north as the day goes on. Model soundings indicate sufficient low-level moisture for at least low clouds, which if thick enough could lead to the freezing drizzle. At the least, many road surfaces could become icy with the warmer southerly flow, as typically happens with a quick warmup at the end of a long Arctic cold spell.

Once temperatures top freezing by midday Downeast, we may be looking some steadier light rain late morning into afternoon/early evening. Some surfaces could stay icy even after it gets above freezing. Over the north, any snow with Friday's event would be very brief any likely of little consequence, as freezing drizzle is the bigger concern. Like Downeast, over the north, any light rain in the afternoon could still make for icy surfaces even with temperatures topping freezing by day's end, as it's been so cold for so long. Rain totals with this system look light, on the tune of a quarter inch or less. No river breakup or flooding expected. Can't rule out total snowpack loss for a few thinner spots over southern portions of the area, but think that most areas will retain some snowpack.

All areas will see a south wind with Friday's system, with perhaps some gusts to around 30 mph. Do not expect winds to be strong enough to lead to any tree or power impacts. Do expect enough of a south wind and favorable orientation of the pressure gradient to allow south winds to penetrate inland easily, with temperatures rising readily on Friday.

Behind the system there isn't much cold air, so although it could barely drop below freezing Friday night after the system exits, not expecting much of a flash freeze of roads/sidewalks.

KEY MESSAGE 3... Potential Winter Storm Saturday Night and Sunday...

Confidence is increasing in a fairly significant weather system for Saturday night and Sunday. There isn't a whole lot of cold air to work with for this system, which means precipitation type (rain vs snow) is very much in question. That said, there is a lot of moisture to work with, and if it falls as snow, it could be significant (more than 6 inches). The better chance for significant snow is in the north, where snow is favored over rain 2 to 1. Downeast, rain is favored 2 to 1. This system appears to be a primary low pressure approaching from the west, with the primary low weakening and a triple point low forming and passing either over our area or to our south. The further south that triple point low passes, the cooler than system and better chance of more snow. There is a bit of a model trend toward a cooler/snowier solution, but that could change. If and where snow does occur, blowing snow could be an issue after it ends for Sunday night and Monday.

AVIATION /02Z WEDNESDAY THROUGH SUNDAY/

00Z Update: Growing confidence in the chance for FZRA at BGR. Though it could remain all snow there, forecast soundings across the board show a warm nose occurring sometime between 06 and 12z, and potentially lasting longer into Wednesday morning, with some back and forth between SN and FZRA possible.

Wednesday: VFR with patchy MVFR to get started becomes MVFR throughout this evening, then LIFR at southern terminals late tonight and IFR at northern terminals Wednesday morning. Light and variable winds becoming N to NE at around 5 kts Wednesday morning. Winds shifting NW through the day on Wednesday.

Wednesday night: KBGR/KGNR/KBHB trending towards VFR, while N terminals cigs stay IFR/becoming MVFR late. NW winds 5 to 10 kts.

Thursday: MVFR possible early at northern terminals then VFR. W/NW winds 5 to 10 kts.

Thursday night: VFR, with local IFR late in the night toward 12z. Winds light and variable.

Friday: IFR or lower. Freezing drizzle possible in the morning. Otherwise light rain. S winds 10 kts with gusts 15-25 kts. LLWS possible.

Friday night: Becoming MVFR/VFR throughout after midnight. SW winds early becoming W around 10 kts.

Saturday: Mainly VFR. Light winds.

Saturday night and Sunday: MVFR with IFR or lower also possible, with rain and snow. E winds switching to the W 10-15 kts.

MARINE

Tonight-Wednesday night: Sub-SCA conditions on all waters tonight. There is a chance that gusts could reach 25 kt on the coastal ocean waters Wednesday/Wednesday evening, but confidence is not high enough to issue an SCA at this time. The intra-coastal waters should experience sub-SCA conditions Wednesday- Wednesday night.

Thursday-Sunday: Winds generally below small craft Thursday to early Friday, though seas could still be around 5 ft Thursday. 40 percent chance of south gales late Friday, then sub-small craft winds Saturday, then 75 percent chance of gales Sunday to early Monday, with winds from the south, switching to the west. Seas peak around 8 ft Friday night with a south swell, with a possibility of seas back up to around 8 ft Sunday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory until 3 PM EST Wednesday for MEZ011- 015>017-032. Winter Weather Advisory until 8 AM EST Wednesday for MEZ029- 030. MARINE...None.