textproduct: Caribou

WHAT HAS CHANGED

- Fire weather concerns mid-week with the greatest risk Wednesday

KEY MESSAGES

1) Heavy snow showers possible late tonight through Monday evening, mainly in northern Maine. This may create slippery road conditions.

2) Unseasonably cold temperatures expected Monday night and Tuesday night

3) Low RHs expected Tuesday and Wednesday which may lead to increased fire weather concerns

DISCUSSION

KEY MESSAGE 1...Heavy snow showers possible late tonight through Monday evening, mainly in northern Maine. This may create slippery road conditions.

KEY MESSAGE 1 DESCRIPTION... Weak surface trough will be moving through late tonight. bringing snow showers to northern areas. Soundings indicating fairly steep lapse rates tonight and again during the day Monday with CAPE values around 30 J/kg. Have confined isolated to sctd snow showers to northern and central areas but cannot rule out a flurry or two Downeast tomorrow afternoon. West winds will increase during the day but not too concerned about snow squall potential, as there will not be a well-defined boundary.

Cannot rule out a Laurentian plume in the wake of fropa over favored areas of the North, specifically the North Woods down toward Mars Hill. Boundary layer flow of around 300 to 310 degrees would bring band of snow showers to these areas with snow accums of up to one half inch. By midnight dry air works in to end snow showers.

KEY MESSAGE 2...Unseasonably cold temperatures expected Monday night and Tuesday night.

KEY MESSAGE 2 DESCRIPTION... A cold airmass will begin filling in behind the departing cold front as high pressure builds in from the west. Temperatures are currently expected to be about 10 to 15 degrees below normal. The coldest night will be Tuesday night with some areas in the North Woods region approaching 0 degrees. A weak pressure gradient should prevent extreme radiational cooling but valleys could see temperatures dip below guidance. The light winds will also favor wind chills in the single digits over the north and teens further south.

KEY MESSAGE 3...Low RHs expected Tuesday and Wednesday which may lead to increased fire weather concerns

KEY MESSAGE 3 DESCRIPTION... Low RHs, breezy winds, and mostly sunny skies may lead to some increased fire weather concerns Tuesday and Wednesday with the greatest risk Wednesday.

On Tuesday, high pressure building in from the west will result in subsidence across the area with a mix of sun and clouds allowing for mixing up to 800mb. With ample dry air aloft, this is likely to result in dry conditions near the surface with RH around 30%, especially in the Bangor region and Upper Penobscot Valley. Questions still remain as to just how low RHs will drop depending on if a weak clipper moving just offshore brings any precipitation to southern areas. In this case, light snow and clouds may prevent significant fire weather concerns.

High pressure slides to the south of Maine Wednesday resulting in W/SW flow across the area under a strong subsidence inversion with ample dry air aloft. Deep mixing up to 800mb combined with mostly sunny skies, especially further south, should contribute to very low RHs, likely below 30%. Winds will not be near Red Flag criteria but will still be breezy with gusts up to 15 to 20 mph.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

IFR cigs this afternoon will improve to MVFR this evening over all terminals. Light rain will gradually come to an end. Downeast terminals should improve to VFR after midnight tonight with HUL holding onto MVFR cigs thru 12z Monday. Remainder of Aroostook terminals should see MVFR cigs with snow showers at times during the morning hours into the afternoon. SW 5-15kts tonight, becoming W 10- 20kts, gusting to 25kts in the afternoon.

Monday night...MVFR cigs over Aroostook terminals with improvement to VFR after midnight. VFR Downeast terminals. NW 5-10kts.

Tuesday to Tuesday night: Periods of MVFR or IFR possible Downeast terminals with possible -SN, but low confidence. VFR at northern terminals. NW winds 5 to 10 kts with gusts to 15 kts.

Wednesday: VFR strongly favored. W winds around 10 kts with gusts to 20 kts, shifting to SW late.

Wednesday night: VFR. S winds 5 to 10 kts.

Thursday: VFR with a slight chance of MVFR at northern terminals late. S winds 10 to 20 kts with gusts to 25 kts.

Thursday night...VFR south, MVFR likely north late. S winds 10 to 15 kts.

Friday...MVFR likely north with a chance of MVFR south. S winds around 10 kts.

MARINE

Seas will remain elevated above small craft levels tonight. As cold front moves through late this evening expect west winds increase aoa 25kts by morning. SCA for all waters thru 18z Monday before conditions drop below small craft levels through the remainder of the period.

Below SCA conditions through Tuesday, then winds above SCA criteria Tuesday night. Below SCA conditions Wednesday and Wednesday night with SCA winds and seas returning Thursday and continuing through Friday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory until 2 PM EDT Monday for ANZ050>052.