textproduct: Caribou

WHAT HAS CHANGED

* The track of low pressure lifting north across the area on Thursday has trended further west. This places most of our region on the warm eastern side of the storm which favors rain in most areas on Thursday.

* Significant differences in ensemble guidance for the Saturday night into Sunday timeframe. Significantly lowered precipitation probabilities.

KEY MESSAGES

1) Low pressure approaching Wednesday night and tracking up along our western border on Thursday will bring some snow to northwestern areas and rain and fog elsewhere late Wednesday night into Thursday.

2) Modified arctic air will press into the area Thursday night into Friday bringing abruptly colder temperatures and causing any water and slush to freeze into ice. Moisture on roads combined with light snow may make travel very icy.

3) Active weather pattern from this weekend into next week but significant uncertainty on system tracks and precipitation types.

DISCUSSION

KEY MESSAGE 1... Low pressure approaching Wednesday night and tracking up along our western border on Thursday will bring some snow to northwestern areas and rain and fog elsewhere late Wednesday night into Thursday.

KEY MESSAGE 1 DESCRIPTION... Low pressure will develop over New York State Wednesday night in response to a trough of low pressure digging into the Great Lakes. This low will track north along the edge of an approaching cold front Wednesday night tracking across Western New England by early Thursday morning then north along our western border on Thursday. This places us on the warm side of the storm. Some snow may spread into northwestern areas Wednesday night with rain elsewhere. The rain will continue into Thursday with some snow hanging on over far northwestern areas. The relatively warmer and moist air over snow covered ground will result in some fog Wednesday night into Thursday. Rain amounts will generally range from around a quarter inch Downeast to a half inch over the far north with snow amounts from 3 to 4 inches over the far northwest to a half inch over the northeast and none across the south.

KEY MESSAGE 2...Modified arctic air will press into the area Thursday night into Friday bringing abruptly colder temperatures and causing any water and slush to freeze into ice. Moisture on roads combined with light snow may make travel very icy.

KEY MESSAGE 2 DESCRIPTION... Challenging forecast on tap for Thursday night into Friday as a strong cold front slides southeast through the CWA. FROPA is expected Thursday evening and much of the guidance remains on track clearing the front in the CWA by 00-03z Thursday evening. Strong 500mb shortwave energy will remain hanging back over Vermont in the evening with a weak surface trof sliding southeast into the state. Air temperatures will be crashing behind the front with conditions becoming slippery as any melt and water on untreated surfaces becoming icy. Uncertainty exists on the potential of snowfall and how widespread it may be which has implications to make things even more slippery.

Given the position of the 500mb potent shortwave to our west, increased upper level divergence will exist over much of Northern Maine and increased surface convergence with moisture leftover. This leads to strong confidence in expecting some light snow in northern areas. Increasing confidence in 1-2 inches of fluffy snow in Northern Maine especially from Baxter Region northward. This will increase the likelihood of slippery travel conditions overnight into the early Friday AM commute. Air temperatures will fall to around 5-10F north by daybreak and 10-15F for the Central Highlands and Bangor Region with 15-20F along the coast. Outside of the light snow expect some snow showers.

Cold temperatures and snow showers extend into Friday with air temperatures struggling unlikely to gain much more than 1-3 degrees with the diurnal swing. Highs topping out in the low to mid teens north and Moosehead Region, upper teens to low 20s for the Central Highlands southward to Downeast coast. Westerly winds 10-20mph will result in single digits below zero wind chills north and single digits above zero south. Lastly, patchy blowing snow is possible in northern areas thanks to any light fluffy snow that falls.

KEY MESSAGE 3...Active weather pattern from this weekend into next week but significant uncertainty on system tracks and precipitation types.

KEY MESSAGE 3 DESCRIPTION... Global ensembles continue to show signs of the near neutral AO shifting negative into the weekend then next week. This combined with the much of the ensembles showing positive PNA as a strong ridge builds across the Northwestern United States resulting in 500mb trofing in the east. NAO looks to remain neutral generally less than +0.5SD and this will allow for systems to develop along a stronger northern jet diving around the long wave trofing. The uncertainty in near neutral NAO is how developed can a system be or if we are more +NAO leading to faster more zonal jet stream winds. It is this uncertainty that has led to significant changes with any potential system this weekend. Have lowered POPs significantly Saturday into Sunday with very few members of the GFS, ECMWF or Canadian producing an organized low pressure system. However, given the increased confidence in long wave trofing means any precipitation is more likely to be snow than rain with cooler temperatures. Models are struggling with how to handle jet streak coming around the long wave trof into next week. There is the potential to develop some type of a coastal system but significant differences exist with the GFS, Canadian and ECMWF ensembles placing lows in many locations with many completely missing us or just grazing the CWA. Will need to monitor the trends but a trend towards colder temperatures is likely with the increasingly negative AO pattern setting up.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

MVFR to IFR conditions across the north and VFR to MVFR conditions over the south are expected today. South winds. Conditions will lower to IFR tonight, possibly becoming LIFR across the area by Thursday morning. South winds with some SSW LLWS at 2K ft late tonight into Thursday. LIFR on Thursday improving to IFR, and possibly MVFR over the south late Thursday. Light and variable winds becoming W over the north and SW over the south late.

Friday...intially MVFR/IFR with -SN at northern terms, VFR south. Expecting VCSH/-SHSN but mainly trending to VFR conditions. Cannot rule out SCT MVFR cigs at northern terms. W winds 5-15kt with gusts up to 25kt. DRSN possible at northern terms for the afternoon hours.

Fri Night...BKN VFR cigs all terms. Winds shifting S 5-10kt.

Saturday...BKN VFR cigs. SW winds 5-15kt.

Sat Night...VFR/MVFR cigs. Possible IFR vsby. -SN possible but confidence is low. Winds light and variable.

Sunday...VFR/MVFR cigs. Possible IFR vsby. -SN possible but confidence is low. Winds W-SW 5-10kt.

MARINE

A SCA will be up today into this evening for S winds gusting up to 30 kt. Winds will drop below SCA tonight then increase back to SCA on Thursday with SW winds gusting up to 30 kt. Seas up to 9 ft today subsiding to 5 ft tonight then up to 8 ft Thursday. Moist air over the waters may result in some fog or mist tonight into Thursday.

Thursday night into Friday westerly winds at SCA conditions expected across the waters with gusts up to 30kt. Cannot rule out some gusts up to 35kt and potential for Gale Conditions especially from 15 to 25nm offshore. Seas during this time 3-5ft for the Intra-Coastal Waters and 5-9ft for the Coastal Waters. Light freezing spray is expected on all the waters late Thursday night into Friday evening.

Winds shift SW late Friday afternoon and remain at SCA levels through Saturday. Seas remain similar at 3-5ft for the Intra- Coastal Waters and 5-9ft for the Coastal Waters. Winds will relax to 20kt gusts into Sunday but seas remain at SCA criteria especially on the Coastal Waters. Potential for rain to reduce vsby at times Saturday into Sunday.

Significant uncertainty in the forecast exists into early next week with the potential of a storm system near the Gulf of Maine that may produce another round of SCAs or potential Gales.

Sea surface water temperatures range from 38-42F from the Downeast Coast out 25nm and east to the Hague Line including Penobscot and Passamaquoddy Bays.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory until 1 AM EST Thursday for ANZ050-051. Small Craft Advisory until 2 PM EST this afternoon for ANZ052.