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Area Forecast Discussion (AFD)

Issued by Caribou, ME (CAR)

FXUS61 KCAR 211150

Area Forecast Discussion
National Weather Service Caribou ME
650 AM EST Thu Feb 21 2019

Low pressure will cross northern Maine today. High pressure 
will build in from the west tonight then cross the region 
later Friday through Saturday.

645am update...Most of the snow for this event has now fallen
towards Bangor and Ellsworth as the dry slot has arrived and
additional amounts will be an inch or less. The band continues
to progress northeastward, exiting the area towards midday.
There won't be much additional snowfall in the
afternoon...except perhaps an inch in northern Aroostook as the
low crosses. The cold front moves south this evening and have
tried to add pops in line with the expected progression.
Guidance continues to show up to 50 J/kg of SBCAPE and good low
level lapse rates.

Previous discussion
The warm occlusion will bring a quick punch of nearly 3 to 4 
inches of snow to Dover-Foxcroft, Bangor and Ellsworth by 7 am 
today and impact the morning commute. In those areas, snowfall 
rates could hit an inch/hour for an hour or two before sunrise. 
There's a decent H850 jet transporting Atlantic moisture inland 
along the occlusion towards a vertically stacked low in western 
Quebec early this morning, but as a secondary triple pt low 
deepens south of Cape Cod early this morning, the H850 jet 
weakens and moisture transport will be shunted south with the 
secondary low. This secondary low will speed eastward into the 
open Atlantic. As a result, the heavier snowfall rates will 
quickly end as the occlusion progresses northeastward in the 
forecast area this morning. Significant snowfall will be done at
Bangor by early this morning, but could linger towards NE 
Aroostook County until just after midday when the dry slot 
overspreads the entire area. Lighter snow will continue in 
northern zones this afternoon as the filling surface low 
meanders from Quebec over the Crown of Maine, along with the 
decaying upper level low. Overall snowfall will range from 3 to 
6 inches. The lightest amounts will be in NW Aroostook while 
parts of Washington County seem most likely to approach 6 
inches. The occlusion will finally push out the Arctic air mass 
that has been in place since last Saturday. Temperatures behind 
the occlusion will rise to mid to upper 30s at Bangor and along 
the coast and even reach the upper 20s as far north as Madawaska
this afternoon. As the surface low moves into New Brunswick 
this evening, it will drag a cold front through the area this 
evening. This cold front could generate some snow squalls. Low 
level lapse rates look good and there's moisture to over H800. 
Potential wind gusts over 40 kts could be realized. At this 
point, will not paint any pops for this threat, but seems most 
likely in a corridor from the Moosehead Lake region towards 
Millinocket and Washington County this evening. The snow squall 
parameter is indicating the potential.

High pressure will build toward the region Friday, cross the 
region Friday night through Saturday, then exit across the 
Maritimes Saturday night while intensifying low pressure tracks 
across the Great Lakes. Expect partly cloudy skies north, mostly
clear skies Downeast, Friday. Mostly clear skies are expected 
across the entire region Friday night through early Saturday, 
with partly cloudy skies Saturday afternoon. Clouds will 
increase early Saturday night, with a chance of snow late across
mostly western portions of the forecast area. Near normal level
temperatures are expected Friday/Saturday.

The Great Lakes low will approach Sunday, while a secondary low
develops across Maine. However, the timing and location of the 
secondary development remains uncertain. Accumulating snow is 
expected Sunday. However, warmer being drawn north in advance of
the primary low from the Great Lakes should allow a transition 
to a wintry mix across much of the region later Sunday. Enough 
warm air could reach the Downeast coast for an eventual 
transition to all rain there. The development of the secondary 
low should help diminish the warm advection and allow a 
transition back to mostly snow later Sunday night into Monday. 
Precipitation types and snow amounts with this storm remain 
uncertain. The lows will exit across the Maritimes Monday with 
snow tapering to snow showers. High pressure should build across
the region early Tuesday. Uncertainty then exists regarding 
another possible low which could begin to approach later 
Tuesday into Wednesday or track south of the region. Near normal
level temperatures are expected Sunday/Monday. Below normal
level temperatures are expected Tuesday/Wednesday.

NEAR TERM: LIFR to IFR vis in snow will affect all sites this 
morning. Snow intensity will let up midday such that no worse 
than IFR vis will occur and that will be mostly north of GNR and
HUL. IFR cigs will be possible at BHB until later this 
afternoon. All sites will become VFR this evening. There is a 
slight risk of snow showers with a trough this evening, but will
not include in TAFs as timing, placement and intensity remain 
in question.

SHORT TERM: Occasional MVFR conditions are possible across 
the north and mountains Friday, with VFR conditions Downeast. 
VFR conditions are expected across the entire region through
much of Saturday, though MVFR conditions could begin to develop
later Saturday night. Conditions will lower to IFR/LIFR levels 
Sunday with snow and a wintry mix, with similar conditions 
persisting early Monday. VFR/MVFR conditions are expected later 

NEAR TERM: The Small Craft Advisory will remain in place. Winds
will be marginal today with gusts reaching 25 kts only at the
outer edges of the marine zones. When NW winds kick in tonight,
sustained wind gusts up to 30 kts are expected for all of the
marine zones through the night.

SHORT TERM: Small craft advisory conditions are expected Friday
into Friday night. Conditions are expected to be below small 
craft advisory levels Saturday. Small craft advisory conditions
are expected later Saturday night. Gale force winds are expected
to develop Sunday then persist Monday. Visibilities will be
reduced in a wintry mix and rain Sunday.

A high astronomical tide will occur around noon today. 16.92 ft
MLLW at Cutler and 22.46 ft MLLW at Eastport will combine with 
southerly flow and about a half foot of storm surge to result in
minor splashover along the Washington County coast. A coastal 
flood statement has been issued from 16z-18z. Lower water levels
expected along the Hancock County coast given the timing of the
low pressure system.

ME...Winter Weather Advisory until 5 PM EST this afternoon for 
     Winter Weather Advisory until 1 PM EST this afternoon for 
MARINE...Small Craft Advisory from 10 AM this morning to 1 PM EST 
     Friday for ANZ050>052.

Near Term...MCW
Short Term...Norcross
Long Term...Norcross
Tides/Coastal Flooding...