Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 260402
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
1102 PM EST Sat Jan 25 2020

.SYNOPSIS...
Low pressure has developed south of the region and will track
into southern Maine tonight and through the state tomorrow
afternoon. The low pulls away Monday with high pressure slowly
building toward the area from the northwest through the end of
the week.

&&

.NEAR TERM /THROUGH SUNDAY/...
1045 PM Update...
Latest NAM soundings showed large layer of dry air above 850
mbs w/the layer below that level saturated. Obs and reports
showed sleet across portions of Aroostook County into
Piscataquis County during the last hr. Temps slowly warming
across the southern areas from Bangor to the coast. Any
frozen/freezing precip should be brief with a changeover to
rain as temps continue to warm. Further n, temps have cooled a
bit back allowing for light snow or sleet for a time before the
transition to freezing rain. 00Z UA showed 50+ kt jet across
southern New Eng this evening. This jet is forecast to lift
northward overnight and coinciding w/some increasing WAA will
aid in some heavier precip, especially across the southern
Piscataquis and Bangor region to the coast. Decided to included
a mention of heavy rainfall overnight across the aforementioned
areas given this jet. QPF was adjusted taking into account the
latest obs. Rest of the forecast looks ok attm.

Previous Discussion...
Sfc low currently located near Philly with fire hose aimed up
acrs Long Island into Upstate NY courtesy of 50-60kt LLJ in
conjunction with RFQ of upper level jet. Sfc low wl track up
along the coast tonight with upr level features mvg thru the
area late tonight into the mrng hrs.

As sfc low tracks along the coast pcpn wl spread into wrn areas
after 00z tonight in the form of rain along the coast with sleet and
freezing rain north of interior Downeast. GFS is the only model now
indicating pcpn wl start off as snow but it has had a cold bias this
winter, likely due to the new core. Hv sided closer to the NAM and
it indicates the dreaded warm nose will be located thru almost the
entire CWA at onset of pcpn.

Sfc temps wl drop acrs srn areas until about 00z bfr beginning to
rise as warm advection kicks in. Nrn areas wl see temps drop until
about midnight bfr rising into the aftn tomorrow. Temps wl lkly bcm
nearly steady fm about daybreak into early afternoon in the lwr 30s
acrs the Crown which wl be a challenge btwn pin-pointing areas for
frzg rain and rain.

As of now temps are blw frzg north of a Moosehead to Houlton line
with temps abv frzg over interior Downeast areas. Temps lkly wl
have a hard time dropping over Downeast tonight with the
exception of most of Washington County as they tend to hold onto
cold air the longest. Hv dropped srn Penobscot and interior
Hancock out of the winter wx advisory for tonight as the only
locations that look to see any frzg rain wl be the very far
northern reaches of the area.

Sfc low still expected to track through the state drg the aftn
hrs with dry slot working into srn areas in the mrng and heading
east by late morning with pcpn quickly winding down bfr wrap-
around gets going ovr the northwest as cold air filters in fm
Canada at the same time.

Locally hvy rain likely to occur acrs the coast tomorrow morning
with total rainfall amounts around 1 inch. This may result in
ponding of water on roadways in the morning. Ellsworth has
reported a snow depth of 6" with Dedham having 5 inches.
Snowpack in that area should be able to absorb some of the rain
with the frost layer right near the surface therefore not
expecting any flash flooding.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
There are still significant discrepancies among guidance
regarding the evolution of the upper level low and its surface
reflection Sunday night. The 12z and 18z runs of the NAM remain
outliers from the rest of guidance in showing a 500mb vorticity
maximum pivoting northeastward over Maine faster from 0-6z
Monday. Went with a non-NAM consensus to close out the storm and
favored the regional GEM and ECMWF, which show a slower
progression of the negatively tilted vort max and deepening of
its surface reflection into the 990mb range over Aroostook
County. This low will continue to deepen and is forecast to move
over or near Presque Isle and Caribou before exiting
northeastward into New Brunswick around 6z. Near the center and
southeast of the low, rain is expected, while snow is favored
along a deformation axis to the north and west over the North
Woods and Saint John Valley, where the winter weather advisory
holds on the longest. Favorable snow crystal growth is expected
with forecast soundings showing at least a few hour period of
strongly negative omega over the DGZ, which will become
saturated. Most snow accumulations are sub-advisory, but will
approach the 4 inch threshold along our western border with
Quebec.

Precipitation will taper to snow showers during the day Monday,
before tapering further to flurries Monday night into Tuesday
morning. A subsidence inversion will lock in low stratus through
Tuesday morning, with gradual clearing later in the day as drier
low to mid level air pushes in from the north. A shortwave
trough will approach the region late Tuesday night into
Wednesday morning. There is still considerable disagreement on
how far into Maine this will go. Even if it impacts the area,
limited moisture should limit precipitation to flurries and
perhaps some snow showers where orographic enhancement occurs.
Increased PoPs to near 10 percent, but did not go high enough to
trigger slight chance wording or put flurries in at this time.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
A weak cold front is expected by early Wednesday evening behind
the departing shortwave. Overall, quiet conditions are expected
Wednesday night through Saturday morning with a ridge of high
pressure in control. Tweaked NBM lows downward on Wednesday and
Thursday nights given that mostly clear skies are expected and
NBM guidance was above the 50th to 75th percentiles. A major
winter storm is possible Saturday night into Sunday, but this is
at the end of the forecast period and may still change
substantially.

&&

.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
NEAR TERM: Low MVFR/IFR cigs acrs the north this afternoon
before dropping to IFR overnight at all terminals. Light rain wl
affect Downeast terminals after 06z tonight through end of TAF
valid time. Further north, mixed precip will move from south
through north tonight into tomorrow.

LLWS likely at all terminals late tonight into tomorrow morning.

SHORT TERM: Sunday night to Monday: IFR to LIFR across
Aroostook County terminals. MVFR Downeast with isolated rain and
snow showers.

Mon night to Tuesday afternoon: MVFR with low ceilings and
scattered snow showers/flurries across Aroostook County
terminals. VFR with ceilings marginally above 3kft AGL
Downeast.

Tuesday evening through Thursday: Mainly VFR. MVFR occasionally
possible across Aroostook County terminals with a slight chance
of flurries or a brief snow shower Wednesday morning.

&&

.MARINE...
NEAR TERM: Winds increase to gales tonight and rmn high through
the morning hours. Seas remain above 5 feet through the end of
the period with small craft conditions likely needed for all
waters through the day Sunday.

SHORT TERM: Winds and waves subside to SCA over the outer waters
and below SCA for the intra coastal waters Sunday night. Winds
and waves subside below SCA Monday night into Tuesday, then
continue below SCA through Thursday.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory until noon EST Sunday for MEZ002-005-
     006-010.
     Winter Weather Advisory until midnight EST Sunday night for
     MEZ001-003-004.
     Winter Weather Advisory until 7 AM EST Sunday for MEZ011-017-
     031-032.
MARINE...Small Craft Advisory until 8 AM EST Sunday for ANZ052.
     Gale Warning until 8 AM EST Sunday for ANZ050-051.

&&

$$

Near Term...Hewitt


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