textproduct: Caribou

WHAT HAS CHANGED

-Added in some light snow to the northeast based on reflectivity

-Increased confidence in occluded front and inverted trough placement for Tuesday night into Wednesday

KEY MESSAGES

1) Light to moderate snow likely early Wednesday morning, with the best chance for snow Downeast. Snow could impact the Wednesday morning commute.

2) Another round of snow possible Saturday across the north, accompanied by warming temperatures lifting to at or above freezing through the forecast area.

DISCUSSION

KEY MESSAGE 1...Light to moderate snow likely early Wednesday morning, with the best chance for snow Downeast. Snow could impact the Wednesday morning commute.

KEY MESSAGE 1 DESCRIPTION...

Occluding Alberta Clipper system moves into the region from the west Tuesday evening. Guidance is in agreement about a general start time around Tuesday evening, with the heavier precipitation starting early Wednesday. Another mid-level low pressure to the north does interact with this clipper system, slowing it down Tuesday night. Some moisture moves in with this system Tuesday evening, but PWATS generally stay at or around 0.5 inches. There is model disagreement with the strength of the low pressure system, as the GFS has a rapidly deepening low moving over the region late Tuesday night, but the ECWMF is being more conservative, with a weaker low pressure moving over the region Tuesday night, and thus a more southerly track. Winter Weather Advisory has been issued for portions of the Bangor and Downeast region.

For Wednesday, the ensemble models show two very different stories. The American models indicate that once the low moves over the waters, it intensifies and stays further to the north. This would cause the center of the storm to move across the Downeast coast, bringing more snow. However, the European ensembles show that once the low moves over the waters, it weakens and moves further south. This set up would give less snow. As of this update, the NBM seems to favor the European ensembles with less snow and a drier set up.

KEY MESSAGE 2...Another round of snow possible Saturday across the north, accompanied by warming temperatures lifting to at or above freezing through the forecast area.

KEY MESSAGE 2 DESCRIPTION... Per the previous discussion: A very strong 500 mb vorticity max originating over Newfoundland through the middle of the week may retrograde through the end of the week and dive back south over the forecast area this weekend. This pattern could lead to enough instability for snow showers, particularly across the northern half of the forecast area. For the time being, it appears the limiting factor for this system will be moisture availability, and current global guidance suggests light QPF with this event, leading to light snow totals. This low pressure system will have arctic connections instead of tapping into the Gulf Stream, so this will not help support stratiform moderate to heavy snowfall. That said, steep low level lapse rates could combine with a tighter pressure gradient aloft to generate convective snow showers that may limit visibility or impact travel during the day on Saturday. A warming trend is in store for behind this low, with temperatures lifting above normal, and potentially above freezing, across the entire forecast area.

AVIATION /18Z MONDAY THROUGH SATURDAY/

This afternoon - Tonight: VFR tonight at all terminals. A few low end VFR clouds moving through northern terminals this afternoon into evening. Potential for some light vicinity showers at far northern terminals this afternoon. Potential for some LLWS tonight at southern terminals. Winds from the NW, 10-15 kts, with gusts up to 25-30kts possible.

Tuesday - Tuesday night: VFR tomorrow. Winds NW at 5-10 kts, becoming light and variable Tuesday night. Conditions begin to deteriorate to MVFR/IFR with snow moving in from west to east Tuesday evening into night.

Wednesday: VFR early, tending towards MVFR/IFR cigs from south to north in snow. Winds light and variable overnight, becoming N at 5 to 10 kts Wednesday afternoon.

Wednesday night - Thursday night: Northern terminals will quickly improve to VFR, while BGR/BHB may linger in MVFR/IFR in lingering snow through Wednesday night before improving to VFR/MVFR during the day on Thursday. NW winds 5 to 10 kts with a few gusts to 20 kts possible.

Friday - Friday night: VFR across all terminals. NW winds 5 to 10 kts.

MARINE

Small Craft Advisory criteria winds and seas over the intra-coastals tonight, and until Tuesday morning over the outer waters. Light freezing spray tonight into Tuesday. N/NW winds tonight through Tuesday. Shifting counter clockwise throughout the night Tuesday into Wednesday morning.

Wind gusts will increase towards 25 kts on the coastal waters Wednesday night as a low pressure system deepens south of the waters. These wind gusts could persist through the end of the week. Seas will generally remain at or below 4 ft through the rest of the week. Light freezing spray is possible early Thursday morning on the intracoastal waters and then again Friday morning across all waters.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory from 7 PM Tuesday to 7 PM EST Wednesday for MEZ015>017-029-030. MARINE...Small Craft Advisory until 7 AM EST Tuesday for ANZ050-051. Small Craft Advisory until 1 AM EST Tuesday for ANZ052.