textproduct: Caribou

WHAT HAS CHANGED

- 6:57AM UPDATE...Have downgraded the Winter Storm Warning to a Winter Weather Advisory for Southern Penobscot County. All other headlines remain as is with this update. There is a dry slot this morning that will taper precipitation in much of the southern 1/2 of the CWA for a couple hours. Expecting precipitation to refill back into the area with an inverted trof developing later this morning.

KEY MESSAGES

1) Snow will impact travel today, especially Downeast areas where heavier snow banding is expected into this evening.

2) Heavy snow showers possible across mostly northern areas Saturday which could create sudden drops in visibility.

3) Significant uncertainty remains regarding possible low pressure system early next week.

DISCUSSION

KEY MESSAGE 1... Snow will impact travel today, especially Downeast areas where heavier snow banding is expected into this evening.

KEY MESSAGE 1 DESCRIPTION... Warm advection snow continues to spread across the forecast area early this morning. Snow covered roads will likley result in some travel impacts for the morning commute.

Low pressure will continue to move southeast out of Quebec province and off the Maine coast today. The low will then continue to track to the south of Nova Scotia and out into the Western Atlantic tonight. As the low continues to move away from the region later this morning, expect the warm advection snowfall to diminish with dry slot pushing in toward the Bangor region by around, or shortly after daybreak. Latest guidance appears to be focusing the heavier snow banding associated with the inverted trough across Downeast areas today, especially Washington County. This resulted in lowering snow totals for the immediate Bangor region a bit.

Despite this, have continued the Winter Storm Warning through 7 PM this evening for the Bangor region, but feeling is we may be able to drop it earlier than that if the heavier snow banding does stay to the east of there this afternoon as anticipated.

Have decided to extend the Winter Storm Warning through 10 PM tonight for the Downeast region, as latest guidance is showing snow associated with the inverted trough persisting, especially across Central and Coastal Washington county. Thus, continued travel impacts can be expected.

Have continued the Winter Weather Advisory for northern areas through 7 PM this evening.

KEY MESSAGE 2... Heavy snow showers possible across mostly northern areas Saturday which could create sudden drops in visibility.

KEY MESSAGE 2 DESCRIPTION... A strong 500 mb vorticity max originating over Newfoundland today is expected to retrograde through the end of the week, then begin to dive back south into northern New England this weekend. This pattern could lead to enough instability for snow showers across the forecast area, with the greatest likelihood for snow showers being across the northern half of the CWA. The limiting factor for this trough of low pressure will be amount of moisture available, since the trough will have origins and connections to a more northern continental air mass instead of moisture driven in by the Gulf Stream. Despite this shortcoming, steep low level lapse rates (GFS forecast soundings suggest 7 to 7.5 C/km) could help support convective snow shower development capable of limiting visibility and impacting travel during the day on Saturday. Depending on how the synoptic pattern evolves, a tighter pressure gradient aloft could also complicate these showers, leading to the potential for gusty winds being brought down in these showers as well. Though widespread heavy snowfall accumulations are not expected, scattered snow showers could be briefly intense with brief moderate to heavy snowfall rates.

There remains some model uncertainty in how the surface feature below the vort max will evolve, particularly in the way of timing, and there is a chance that this feature will slow enough that snow showers will develop Saturday night into early in the day on Sunday. Should this feature move through overnight, the lack of diurnal heating support will limit the impact of these snow showers.

A warming trend is in store for behind this low pressure system, with temperatures lifting well above average for this time of the year, even lifting above freezing over much of the forecast area by early next week.

KEY MESSAGE 3... Significant uncertainty remains regarding possible low pressure system early next week.

KEY MESSAGE 3 DESCRIPTION... A strong low pressure system may develop over southeastern CONUS late this weekend and then track off the coast of the Carolinas into early next week. There remains great uncertainty in the future track of this system. The 12z run of the deterministic ECMWF is most impressive with respect to our forecast area, though even this single model has trended further south, with little to no impact to our area early next week. Other guidance continues to keep the system well offshore and away from our forecast area. The NBM continues to bring slight chance to chance PoPs through Monday due to this uncertainty, and this is what the forecast reflects for the time being as the system continues to be closely monitored.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

MVFR/IFR conditions are expected at all the terminals today in snow. MVFR/IFR will continue through early this evening with conditions expected to improve to VFR/MVFR after midnight. VFR is expected at all the terminals on Thursday. E to NE wind 5 to 10 kt today, becoming N tonight. NW wind 10 to 20 kt with gusts up to 25 kt on Thursday.

Thursday night: VFR under SKC across all terminals. NW winds 10 to 15 kts with a gusts 20 kts.

Friday - Friday night: VFR across all terminals. NW winds 5 to 10 kts with gusts to 20 kts early. Winds becoming light and variable overnight.

Saturday - Saturday night: VFR with possible trend to MVFR/IFR in snow showers, with deteriorating conditions most likely across northern terminals. NW winds 5 to 10 kts.

Sunday: Conditions dependent on timing of the northern low pressure system. Lingering MVFR/IFR most likely with possible light snow showers remaining through the morning. Return to VFR possible if system clears through quick enough. NW winds 5 to 10 kts, becoming light and variable late.

MARINE

Wind and seas are expected to remain below SCA levels today. A few gusts to 25 kt are possible early this morning and again tonight. Winds are then expected to increase to SCA levels later Thursday.

Wind gusts 25 to 30 kts over all waters Thursday night into Friday. These strong small craft advisory conditions will begin to taper off late Friday, settling below small craft advisory criteria Friday night and through the weekend. Seas will generally remain at or below 4 ft through this time, with light freezing spray possible each morning.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory until 7 PM EST this evening for MEZ001>006-010-011-015-031-032. Winter Storm Warning until 10 PM EST this evening for MEZ016- 017-029-030. MARINE...None.