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Area Forecast Discussion (AFD)

Issued by Caribou, ME (CAR)

FXUS61 KCAR 230221

Area Forecast Discussion
National Weather Service Caribou ME
921 PM EST Fri Feb 22 2019

High pressure will move across the region tonight and then move
east on Saturday. Low pressure will approach from the west 
Saturday night and cross the region Sunday through Monday.


9:22 pm update: High pressure centered across the eastern Great
Lakes will build toward southern New England through Saturday 
afternoon. Satellite pictures and observations show that most of
the clouds that were across the FA at 6 pm have dissipated. The
combination of a clear sky and deep snow pack in the north has 
allowed temps to drop to near zero in the colder valleys in the 
north. Made a few minor tweaks to the temperatures and sky grids
based on the latest observations and expected trends, but 
nothing significant. 

Previous discussion:
High pressure will build toward the region tonight. Mainly clear
skies, light winds, and deep snow pack will allow for good
radiational cooling conditions overnight. Have gone a bit colder
than guidance as we should see lows once again falling below
zero in the colder valleys of the north, where lows of 5 below
to 10 below zero should be common. Across the central highlands
and downeast areas, expect lows to generally range from the
upper single digits above zero to the low and mid teens.
Saturday is a dry day as the high moves off to our east. Highs
on Saturday will be near normal for this time of year with highs
ranging from the mid to upper 20s north and low to mid 30s 


Strong high pressure will be exiting the east coast Saturday
night, with NW flow over much of Maine. This will provide a 
widespread cool night for the region ahead of approaching 
overrunning storm event Sunday. 

NAEFS Mean MSLP highlights a strong low pressure area north of 
the Great Lakes Sunday morning through the afternoon. This will 
be the parent low to bring north a surge of warm moist air. With
cold air in place over the region, this moisture will overrun 
cold air, producing a widespread precip event across New England
Sunday. As mid-level jet dynamics become favorable, a secondary
surface low will develop off the New England coast, tracking 
north along the Maine coast. The track of the low and resultant 
winds will determine how far inland warm air in the low levels 
will overcome freezing conditions. Per current thoughts, this is
anticipated to occur along coastal Downeast relatively quickly,
by early Sun afternoon. A light accumulation of snow will occur
before the transition. As the warm layer aloft makes its way 
over interior Downeast, there is a chance snow will mix with 
sleet before a transition to rain, particularly over the 
Penobscot and Bangor Region. North of a Dover-Foxcroft to 
Danforth line, CAD and positioning of the low will help keep 
cooler temperatures in place, resulting in precip remaining 
snow. While the initial wave of precip is quite progressive, 
some convergence existing between parent low and coastal low 
will prolong the event in the north. Although, extent of dry air
pushing into the region will need to be monitored. With QPF 
amounts and snow ratios capped at 13:1 for beginning of event, 
decided to hoist a Winter Storm Watch beginning Sunday 12z in 
areas expected to stay mostly frozen precip. 

Winds will be the other concern with this system. As mid-level
jet noses in along the Gulf of Maine coast, a 925mb LLJ will 
develop along the coast of 50-70kts supporting forecast surface 
gusts of 40kts Sunday evening. These gusty winds translate 
inland, albeit lighter, 20-25mph during the day. As center of 
coastal low traverses Downeast/ME coast Sunday night, winds 
slacken into Monday morning. Wind shift will occur as the two 
lows begin to vertically stack over the Gulf of St. Lawrence. 
Winds will again ramp up Monday afternoon into the evening and 
overnight hours, this time from the NW, gusting 30-45mph. Higher
terrain stands to see higher gusts. The strong winds will 
promote ample cold air advection for single digits lows across 
much of the area Monday night.


System will exit to NE, with cold air making a return across the
state all the way to the coast. Next weather maker will be some
moisture associated with a clipper, passing nearby to the 
south. However, southern zones see a chance at light snow 
showers Wednesday night into Thursday morning. Dry conditions
for the north and east.

The end of the week will be dominated by high pressure over the
Northeast. This will result in cold and dry conditions.
High and low temps will run below normal across the FA.


NEAR TERM: VFR conditions expected all TAF sites through

SHORT TERM: VFR conditions expected Saturday and early Saturday
night. Low pressure intensifying over the Great Lakes will bring
snow to the north and snow transitioning to rain Downeast. As a
result, sites will go IFR/LIFR Sunday through Monday. Conditions
improve Monday night, except in the north with lingering snow
possible. Conditions will improve to MVFR Tuesday and VFR


NEAR TERM: The wind and seas are expected to remain below SCA 
levels through Saturday. Light freezing spray is expected late 

SHORT TERM: Gale Watch in effect for Sunday through Monday
night for winds reaching 40kts briefly Sunday afternoon. A 
significant southeasterly fetch is expected to develop across 
the Gulf of Maine and continue into Sunday evening until broken
up by a wind shift later Sunday evening. Winds remain elevated
through Sunday night, strengthening Mon afternoon as storm 
system departs to NE. Wind gusts will approach 50kts, slowly 
slackening Tuesday morning and through the day. Waves will grow
8-10 ft Sunday, to 10-12ft Monday.


ME...Winter Storm Watch from Sunday morning through Monday morning 
     for MEZ001>006-010-011-031-032.
MARINE...Gale Watch from Sunday morning through Tuesday morning for 



Near Term...CB/Duda
Short Term...Cornwell
Long Term...Hewitt