textproduct: Caribou

WHAT HAS CHANGED

- Added patchy to areas of fog Friday night into Saturday AM.

- Increasing probability of rain changing to snow Sunday night into Monday AM across Northern Maine.

KEY MESSAGES

1) Rain is expected from late this afternoon into late tonight with a third to a half inch. This will contribute to continued rises on the rivers.

2) Areawide rain Sunday changes to snow Sunday night into Monday morning across Northern Maine leading to the potential of slick Monday AM commute.

DISCUSSION

KEY MESSAGE 1...Rain is expected from late this afternoon into late tonight with a third to a half inch. This will contribute to continued rises on the rivers.

KEY MESSAGE 1 DESCRIPTION... Spotty showers and patchy drizzle will be possible anytime today. A small wave of low pressure will then approach from the Great Lakes later today spreading steadier rain across the area late this afternoon and continuing tonight. Amounts around a third of an inch are likely across the north and Downeast with a band of just over a half inch possible across central areas through tonight.

The rain, combined with some additional snowmelt from the headwaters of the northern rivers, will contribute to additional rises on the rivers. However, most of the ice has washed out of these rivers and flooding is not anticipated. The rain may result in some ponding in low lying areas and rises of small streams. Rain should end late tonight over the north and early Friday morning Downeast.

KEY MESSAGE 2...Areawide rain Sunday changes to snow Sunday night into Monday morning across portions of the area leading to the potential of slick Monday AM commute.

KEY MESSAGE 2 DESCRIPTION... During the day Sunday a potent parent storm system will lift north out of the Great Lakes into Ontario then Quebec dragging an occluded front into New England. A strong 500mb shortwave will dig south dragging significantly colder air in its wake with large scale upper level divergence overhead leading to surface convergence. As the front pushes towards Maine during the morning hours rain will develop across the area Sunday AM and last throughout the day. Expecting generally 0.3-0.7 inch of rain during the day Sunday into early Sunday evening but cannot rule out higher amounts up to 1 inch. This will allow for continued slow rise of area rivers/streams but flooding is not expected.

Sunday night significant agreement in global model guidance of a surface low developing on a triple point across the Gulf of Maine waters near the Maine coast. As this happens and the occluded front slides through expecting Sunday night a significant surge of colder air with a moist DGZ. As the boundary layer cools to near freezing precipitation will change from rain to snow across Northern Maine especially in the North Woods to St. John Valley first then eventually reaching much of the CWA. The uncertainty lies in how much precipitation will be available behind FROPA and how quick the cold air works into the region. GFS is slower on the cold air while ECMWF/Canadian is much faster but the GFS has more QPF available with the ECMWF/Canadian with less. The potential exists for accumulating snow especially in Northern Maine with rain mixing with snow as far south as the Bangor Region to Interior Downeast. NBM probabilities of accumulating snow are increasing but with the numerous uncertainties still on the low side. Will continue to monitor the trends as we get closer to this event. Temperatures will be falling below freezing for most areas from Bangor to Calais along The Airline northward to the St. John Valley which may lead to black ice simply from refreezing wet roadways. This could lead to a slick Monday AM commute even if there is no snowfall.

AVIATION /04Z THURSDAY THROUGH MONDAY/

Today...LIFR all sites in very low clouds and fog. Winds SE around 5 kt.

Tonight...LIFR in low clouds and fog. Light and variable wind.

Friday...LIFR, improving to IFR around midday, then MVFR during mid afternoon and finally VFR by late afternoon from north to south. Winds N 5 to 10 kt.

Saturday...MVFR cigs in the AM at southern terms. AM IFR/LIFR vsby with FG possible at BGR and BHB. Otherwise VFR the rest of the day for all terms. S-SE winds 5-15kt.

Saturday night...MVFR/IFR with LIFR possible. RA BR/FG possible. S winds 5-15kt with gusts up to 20kt possible at northern terms.

Sunday...MVFR/IFR likely with RA. S winds 5-15kt shifting W late day.

Sunday night...MVFR/IFR likely. RA changes to SN at northern terms. RASN mix for BGR and RA at BHB. Winds shift NW 5-15kt. Monday...MVFR becoming VFR. SHSN possible. NW winds 10-15kt with gusts up to 25kt possible.

MARINE

Winds will be below SCA today, tonight and Friday and seas around 3 ft. Fog will likely limit vsby at times today and tonight with vsby improving on Friday. Winds/seas below SCA conditions through Sunday afternoon. Sunday night winds increase and gust >25kt with seas building to 4-6ft. Winds/seas fall back below SCA conditions by Monday night. Fog may reduce vsby Sat AM, then rain/fog will reduce vsby Sat night into Mon AM.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Dense Fog Advisory until 8 AM EDT this morning for MEZ001>006. MARINE...None.