textproduct: Caribou

WHAT HAS CHANGED

- Increased chances of precipitation for tomorrow across Northern Maine associated with powerful vorticity max.

- Increased confidence on a early week warming trend into the upper 30s and low 40s by Tuesday.

KEY MESSAGES

- Scattered moderate to heavy snow showers on Saturday, which may result in rapid drops in visibility and sudden deterioration in travel conditions. - Warming trend early next week which will bring temperatures into the upper 30s and low 40s by Tuesday.

- A low chance of a winter storm Wednesday into early Thursday.

DISCUSSION

KEY MESSAGE 1...Scattered moderate to heavy snow showers on Saturday, which may result in rapid drops in visibility and sudden deterioration in travel conditions.

KEY MESSAGE 1 DESCRIPTION... Setup...A very strong 500mb vorticity max tomorrow will be pivoting down from Northern Quebec associated with a 506dam low. This upper level energy is off the charts with cyclonic relative vorticity values up to 45. Very good agreement between NAM 3km, GFS, ECMWF and Canadian operationals along with the AI models. At the surface a cold front will be dipping SE through the state reaching the Quebec/Maine border near Estcourt Station to Nine Mile between 7-9AM EST. Through the day the 500mb low and powerful vort max will dip SE through the CWA. Models remain consistent with the center of the vort max traveling from Estcourt to Houlton area. This will keep the strongest energy north while the 500mb jet max increases over Southern & Central Maine with an 80-90kt 500mb streak.

Expecting increased boundary layer moisture and with strong upper level forcing/dynamics expecting snow showers to develop in the AM and will be likely in Northern Maine with isolated to scattered snow showers from the Bangor area northward. Much of the 925mb increased winds beneath the 500mb jet streak will be diving south of the CWA. Although heavy snow showers are expected with robust upper level dynamics the potential for snow squalls is low. Hi-Res modeled soundings show very little wind to mix down generally 15-20kt so although the squall potential is low it also isnt zero. Either way be prepared for rapidly changing conditions tomorrow across much of the North generally along and north of a line from Greenville to Millinocket to Danforth and points northward. If traveling tomorrow in Northern Areas expect rapid drops in visibility and sudden deterioration in road conditions. The cold front will exit the CWA to the SE by late afternoon into the early evening.

In terms of accumulations it will be dependent on snow shower coverage and intensity. Blending with latest hi-res guidance we see probabilities of >0.5 inch at 50-85 percent along the Route 1, 1A, 11 and 161 corridors in Northern Maine. There is 50 percent probabilities of >1 inch in the St. John Valley down to the Caribou area. Given these numbers and strong signals of numerous snow shower coverage opted to go with 0.5 to 1.5 inch of snow tomorrow but isolated higher totals possible.

KEY MESSAGE 2...Warming trend early next week which will bring temperatures into the upper 30s and low 40s by Tuesday.

KEY MESSAGE 2 DESCRIPTION... A warming trend is expected to begin Monday as southerly flow develops ahead of an approaching low pressure system. Ample warm air advection is expected to persist through Tuesday as the low passes to our north. Temperatures should peak in the upper 30s over the north and low 40s over the Downeast and Bangor regions. Warm southerly flow over a cold snowpack may result in the development of some patchy fog. Model soundings do not show a clear signal for fog but cannot rule it out. Will have to watch the wind speeds carefully as too strong of winds will promote mixing that will limit the fog threat.

KEY MESSAGE 3...A low chance of a winter storm Wednesday into early Thursday.

KEY MESSAGE 3 DESCRIPTION... Behind a cold front passing through Tuesday night that will break the warm spell there is a low potential for a system passing to the south to bring some snow to the area Wednesday into early Thursday. Substantial model disagreement exists with the Euro ensemble members showing a weaker, more southerly system while the GFS ensembles show a stronger, more northerly system. As the upper-level energy remains well off the west coast currently, we may not have a better idea of how the system will evolve until early next week when it can be better sampled by the upper air network. There is more confidence that any precipitation is likely to be mostly snow as high pressure off to the northwest will be funneling in ample cold air. Models are also suggesting that if any snow does reach us, it will likely be the southern areas that receive the most.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

18z TAF UPDATE...Rest of Today FEW150-250. NW winds 10-15kt gusting up to 20kt.

Tonight, SKC/FEW cigs becoming BKN VFR tonight. Light and variable winds.

Tomorrow VFR south with BKN cigs. Across the Northern terms expecting VFR or high end MVFR cigs. PROB30 for -SHSN that may cause significant vsby drops to IFR in the afternoon.

Saturday night: MVFR at northern terminals as snow showers taper off. Generally VFR southern terminals. NW winds at 5-15 kts. Slight chance for LLWS late Saturday night/early Sunday morning.

Sunday - Monday: Becoming VFR throughout Sunday morning. NW winds 5 to 10 kts with gusts 15 to 20 kts possible Sunday, decreasing throughout the day. Winds shift to the S Monday at 5-10 kts.

Monday night - Tuesday: MVFR or lower possible at northern terminals due to snow showers. VFR with a chance of MVFR in rain and snow showers at southern terminals. S winds becoming SW Tuesday at 5-10 kts.

Tuesday night - MVFR northern terminals with snow showers. VFR southern terminals. W winds around 5 kts.

Wednesday - Chance of MVFR with IFR also possible, especially for southern terminals. Snow showers with some rain showers possible south. NW winds 5 to 10 kts.

MARINE

Winds/seas below SCA conditions through Saturday evening. NW winds will increase Saturday night into SCA criteria with light to moderate freezing spray developing.

A 20% chance of gales early Sunday morning on the outer waters with SCA conditions elsewhere, eventually decreasing to below SCA conditions by the evening. Below SCA conditions through Tuesday with a 20% chance of SCA gusts on the outer waters early Wednesday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...None.