textproduct: Caribou

WHAT HAS CHANGED

- Decreased snow amounts in Northern Maine, but kept the amount of snow that comes as sleet about the same. - Increased freezing rain totals a bit in the corridor from Houlton to Millinocket to Greenville. - Slightly delayed onset of wintry precipitation in the north this morning. - Updated aviation discussion for 6z TAFs.

KEY MESSAGES

1) Significant winter storm today through early Thursday bringing multiple precipitation types and treacherous travel north of Bangor/Downeast.

2) A fast moving low will bring some snow Friday night into Saturday with the potential for a few inches, especially over central and northern areas. This could cause messy and slippery conditions for Saturday morning travel.

3) A large storm system developing in the Upper Midwest on Sunday will spread snow into the area Sunday evening, changing to rain from south to north across the region overnight Sunday night. Strong south winds are possible with the system on Monday. This could result in messy travel, mainly north, Monday morning, and some isolated power outages on Monday.

DISCUSSION

KEY MESSAGE 1...Significant winter storm today through early Thursday bringing multiple precipitation types and treacherous travel north of Bangor/Downeast.

KEY MESSAGE 1 DESCRIPTION... No significant changes to our thinking for the storm. Kept headlines as is. Refined the forecast a bit thanks to increasing model agreement, by decreasing snow amounts a bit in the north and increasing freezing rain amounts a bit from Houlton to Millinocket to Greenville. Also delayed the onset this morning just a bit this morning in the north thanks to recent trends in guidance.

As of 230am, backdoor cold front has surged south through the entire area. Freezing line has reached Houlton and Greenville and will continue to progress south. No precipitation as we await the system to arrive.

As mentioned above, the start of the system is delayed just a bit from what we were thinking. We are looking at wintry precipitation to start closer to 10am today rather than 7-8am. With less time for the airmass to be cold enough for all snow in the north, decreased snow totals in the north but kept sleet amounts close to the same. In fact, wouldn't be surprised if areas from Mars Hill and Clayton Lake south don't get any snow at all and it begins as sleet (by the way, sleet does technically count as snowfall too for our record-keeping). One area we are watching closely this morning is from Bangor east to Princeton. Currently these areas are not under a winter weather advisory. Thinking is that there won't be much precipitation this morning for areas this far south, plus temperatures from Bangor to Princeton won't quite get down to freezing, and by the time the more significant precip arrives later today, the atmosphere would just support rain or perhaps rain and sleet. That said, will be watching closely.

Precipitation begins somewhat light today but increases in intensity as we head through the day. Generally snow in the St John Valley today, but areas a bit further south will go over to sleet pretty fast. That's not to diminish the impact. In fact, sleet, though not accumulating nearly as readily as snow does, has a big impact on travel and is extremely difficult to shovel and plow. Heading south toward the Greenville to Millinocket to Houlton region, look for sleet and freezing rain today, transitioning to mostly freezing rain this evening. Did raise freezing rain totals some for this central corridor. Don't think there will be enough ice for more than isolated power outages, but will need to keep a close eye as in a worst case scenario, flat-ice amounts could get up around a half inch which is when outages start ramping up.

Tonight, the precipitation will gradually transition from sleet to freezing rain over the far north, and from freezing rain to rain for central areas. The tricky part later tonight is how far north the freezing line makes it. Some CAMs, specifically the REFS members, keep the freezing line near or just south of Presque Isle until after about 9am Thursday (at which point most precip is done anyway). This is colder than the thinking before. This doesn't seem implausible given some CAMs don't have any low-level southerly push in the wind field through mid- morning. Did trend forecast a little colder a little longer in the north late Wednesday night to mid-morning Thursday, which did raise the freezing rain totals just a bit in the far north.

During the day Thursday, precipitation moves out from west to east. Some uncertainty on exact ending time and can't rule out a quick transition to snow at the end, but more likely, the event will just end as a light rain mid-late morning Thursday. Warmer Thursday afternoon with mid 30s far north, around 40 central areas, and upper 40s Downeast. However, colder air starts working in late Thursday and after dark Thursday any remaining sleet/ice will harden into concrete and be nearly impossible to remove.

KEY MESSAGE 2...A fast moving low will bring some snow Friday night into Saturday with the potential for a few inches, especially over central and northern areas. This could cause messy and slippery conditions for Saturday morning travel.

KEY MESSAGE 2 DESCRIPTION...

A small clipper type low will cross the Great lakes on Friday then spread snow into our area Friday night as it rapidly approaches. Models differ on the track of this low with some, like the GFS, tacking the low across the southern part of region while others, like the NAM and ECMWF, tracking the low across the north central part of our region. The southern track would give a longer steadier moderate snowfall amounting to perhaps 4 to 6 inches inland while the northern track would bring a quicker snow followed by a dry intrusion giving around 2 to 4 inches central and north. A change to rain is likely along the coast in both cases. Confidence is high that some snow and messy travel will at least effect central and northern areas early Saturday while impacts Downeast and in the lower Penobscot Valley are less certain and will depend on the eventual track. The low quickly moves east and away on Saturday as temperatures rise to near freezing over the far north and well into the 30s elsewhere. Roads will likely just be wet by late morning. Some snow showers may linger over the far north in the wrap around into Saturday afternoon.

KEY MESSAGE 3...A large storm system developing in the Upper Midwest on Sunday will spread snow into the area Sunday evening, changing to rain from south to north across the region overnight Sunday night. Strong south winds are possible with the system on Monday. This could result in messy travel, mainly north, Monday morning, and some isolated power outages on Monday.

KEY MESSAGE 3 DESCRIPTION...

A large trough digging into the Plains on Sunday will support intensifying low pressure in the Upper Ohio Valley on Sunday. Snow ahead of an advancing warm front will spread into the area Sunday evening. An increasing southerly wind will advect warmer air in from the south overnight Sunday night changing snow to rain from south to north. Occasional rain and strong south winds will continue into Monday. The strongest winds will likely be Downeast associated with a low level jet. Some isolated power outages will be possible. The low will pull a strong cold front into the area Monday afternoon as the low center lifts to our north. SSW winds will be very strong aloft as this front moves in and any mixing that pulls down the higher winds from aloft could result in strong and possibly damaging winds gusts as the front moves through. Drier and moderately cooler air will surge into the region Monday night with gusty west winds as more mixing occurs.

Impacts from this system include some messy roads over the north early Monday morning with roads just becoming wet by late morning. Also, possible isolated power outages, mainly Downeast and Lower Penobscot Valley on Monday with a chance for some additional outages in any strong gusts associated with the cold front later Monday afternoon.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

Today...Wintry precipitation developing over northern TAF sites by 16z. BGR should be just rain, or perhaps rain mixed with sleet. BHB should be all rain. For northern TAF sites today, look for mostly snow and sleet PQI north, and freezing rain or sleet for HUL. Ceilings falling to IFR at all sites by 0z Thursday. E/NE wind 10 kts with some higher gusts.

Tonight...Rain Downeast (BHB/BGR) and wintry precipitation further north, falling as sleet or freezing rain, generally transitioning to freezing rain and rain later tonight. Mainly IFR/LIFR. LLWS could be quite significant BGR/BHB tonight, especially from about 3-10z.

Thursday...Starting out IFR/LIFR, but improving to VFR most places in the afternoon. SW wind 10 kts becoming W 10-15 kts with gusts to 25 kts.

Thursday night...IFR to MVFR becoming VFR W winds around 10 kt and gusty.

Friday...VFR. SW winds 5 to 10 kt.

Friday night...VFR, dropping to MVFR then IFR Friday evening and remaining IFR overnight. SE winds 5 to 10 kt.

Saturday...IFR, possibly improving to MVFR south. W winds 10 to 15 kt south and NW winds around 10 kt north.

Saturday night...MVFR south improving to VFR. IFR north, improving to MVFR then VFR late. W wind around 10 kt.

Sunday...VFR, possibly lowering to MVFR south late. W wind around 5 kt becoming S.

Sunday night...IFR. SE wind 10 to 15 kt. Significant SSW wind shear developing.

MARINE

E/NE small craft winds today becoming S today and probably will increase to gale levels at least in the outer waters. Issued gale watch. Winds then shift to W Thu afternoon and drop back down to small craft. Seas building from 2-4 ft early today to 6-10 ft Thu afternoon.

A gale will be needed Thursday night, dropping to SCA Friday then back to gale Friday night into most of Saturday night. Winds will drop below gale and SCA Sunday then increase to a strong gale and possibly a storm Sunday night through Monday night in south winds. Seas up to 7 ft Thursday night, 6 ft Friday, building up to 10 ft late Friday night into Saturday. Seas will drop to 4 ft Sunday then potentially up to 12 ft late Sunday night and 16 ft on Monday in response to the southerly.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Winter Storm Warning from 8 AM this morning to 8 AM EDT Thursday for MEZ001-002. Winter Storm Warning from 8 AM this morning to 2 AM EDT Thursday for MEZ003>006. Winter Weather Advisory from 8 AM this morning to 11 PM EDT this evening for MEZ010-011-031-032. MARINE...Small Craft Advisory until 1 AM EDT Thursday for ANZ050-051. Gale Watch from late tonight through Thursday morning for ANZ050-051. Small Craft Advisory from 6 AM this morning to noon EDT Thursday for ANZ052.