Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 181058 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 558 AM EST Sat Nov 18 2017 .SYNOPSIS... A weak area of high pressure across the region this morning will move east. A strong area of low pressure will pass west of the area Sunday afternoon, and will be followed by a colder air mass Sunday night and Monday. && .NEAR TERM /THROUGH TONIGHT/... 555 AM update...Forecast remains on track this morning. Skies are mostly clear everywhere except extreme northeastern Aroostook County, where a pesky stratocumulus deck remains. Have made some adjustments to the sky cover accordingly. No other changes were needed. Previous discussion...Another round of wintry weather is expected to move in this evening and overnight. Today starts out tranquil as high pressure crosses the region. The ridge axis moves to our east this afternoon, making way for low pressure pushing across the Great Lakes. Expect increasing mid and high clouds this afternoon ahead of the approaching low, along with winds turning to the southeast. Western areas could see a few sprinkles or snow flurries late this afternoon, but most locations will be dry through the day. Highs will range from the lower and mid 30s north to around 40 Downeast. Warm air advection begins in earnest tonight as the low begins to lift into the Saint Lawrence River Valley, allowing a swath of precipitation to spread from west to east overnight. The warm air will initially spread northward by lifting over the colder air at low levels, resulting in a mix of snow, sleet, and freezing rain, mainly along and north of a Dover-Foxcroft to Danforth line. Temperatures will fall a bit early this evening, but then they will rise overnight as the warm air is able to replace the cold air at the surface. As such, the wintry mix will gradually change to just plain rain from south to north, with all but the upper St John Valley seeing all rain by daybreak. Both snow and ice accumulations will be light, less than 1 inch and less than 1 tenth of an inch, respectively. Therefore, only minor travel impacts are expected. However, if the cold air sticks around longer than currently anticipated, the ice and snow accumulations could increase. Will allow later shifts take a look at the incoming hi-res near term models before making any decisions on headlines. && .SHORT TERM /SUNDAY THROUGH MONDAY/... A strong area of low pressure near Montreal Sunday morning is expected to track to the north of the Gaspe Peninsula by 00z Monday. The CWA will be in the warm sector Sunday morning and into the first part of the afternoon with periods of rain. Colder air begins to sweep in from the west mid to late afternoon as the rain ends from the south. Much colder air pours into the region Sunday night on a gusty west wind. Isolated snow showers are possible to the north and west of the Katahdin Region. Any areas of standing water will freeze Sun night, and temperatures Monday afternoon will only recover to the mid 20s north to the low 30s in the Greater Bangor Region. There will be a gusty west wind that will add to the chill. It will likely remain mostly cloudy in the north with a few flurries and partly sunny toward the coast. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Overall fairly quiet weather for Thanksgiving week. A weak frontal boundary could produce a rain or snow shower late Tue night or Wednesday morning, but there will not be much moisture with this front. There remains uncertainty as to whether a wave develops along the front to the south of the area and clips the region with another period of rain or rain changing to snow Wednesday night. Much of the guidance keeps this feature offshore, but it bears watching. The 00Z ECWMF now brings precipitation to nearly all of the CWA (mostly rain, ending perhaps as a period of snow), and the GFS keeps all of the precipitation well south and east of the region, and the Canadian just grazes the coast. The 00z ECMWF has little support from its ensembles members. Any potential system bears watching, but until there is better agreement will stick with a model consensus and nothing higher than chance PoPs. Colder air filters into the region behind the front, and Thanksgiving should be a dry day with some breaks of sunshine and highs from the upper 20s in the Saint John Valley to the mid to upper 30s Downeast. A tough and developing surface low may bring a chance of snow to mainly northern areas Friday, but there is not great model agreement, and some models would keep the area mainly dry. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... NEAR TERM: VFR conditions will prevail through much of the daylight hours, with increasing mid and high clouds through the afternoon. Conditions will then deteriorate overnight as a mix of snow, sleet, freezing rain, and rain spread from west to east 00z-12z Sun. Expect all terminals to be IFR by 06z or shortly thereafter. BGR and BHB will remain plain rain through the period, while the other terminals will see snow mixing with sleet and freezing rain, then change over to plain rain from south to north 06z-12z. SHORT TERM: LIFR to IFR in rain Sunday will improve to MVFR and eventually VFR at the Downeast terminals by late Sunday. Improvement to MVFR expected at the northern terminals toward evening. Predominately MVFR Sun night at the northern terminals with brief IFR in any snow showers. VFR expected Downeast Sun night. Predominately VFR Mon and Tue, but patchy MVFR ceilings possible at times in the north. VFR expected Wed, although conditions may lower to MVFR late in the day at the Downeast terminals. && .MARINE... NEAR TERM: The Small Craft Advisory has been cancelled. A few gusts to 25 kt are possible through early this morning, but a downward trend is expected through the day as high pressure builds over the waters. Winds will then turn to the south and increase tonight ahead of low pressure lifting well to the northwest of the region. SCA conditions are likely by late tonight, with gales possible early Sunday morning. SHORT TERM: Gales likely on the waters Sunday and have issued a gale watch. Gales possible into monday with small craft advisory conditions likely to persist into Tuesday. && .CLIMATE... The first measurable snowfall (0.8") of the season was observed at Caribou Friday, 11/17. It was the 4th latest measurable snowfall on record behind only 1994, 2010, and 2016. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Gale Watch from Sunday morning through Sunday evening for ANZ050>052. && $$ Near Term...Hastings Short Term...CB Long Term...CB Aviation...Hastings/CB Marine...Hastings/CB Climate... is the U.S. government's official web portal to all federal, state and local government web resources and services.