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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCAR 131357
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
957 AM EDT Thu May 13 2021

.SYNOPSIS...
A cold front will cross the region today. High pressure will
move south of the region Friday through Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
952 AM Update: Tmg of shwrs was advcd a little quicker thru our
FA durg the aftn and erly eve hrs based on consensus model tmg
of best dynamics ahead of the cold front and upper lvl s/wv.
Otherwise, fcst hrly cld cvr, temps, and dwpts were adjusted
thru the day based on latest sat imagery and sfc obs trends with
fcst aftn hi temps adjusted upwards a deg or two F.

Prev Disc: A cold front behind the exiting low will move across
the region today starting in the St John Valley and moving
south. The day will begin with mostly sunny skies, allowing for
surface heating and creating convective clouds across the north.
As the front moves through, the convective clouds are expected
to produce scattered showers. As the day continues into the
afternoon, surface and elevated CAPE values increase into
hundreds J/kg across the region, 300+ J/kg from Southern
Aroostook northward, busting through the decreasing CIN. In
addition, very steep lapse rates, wind sheer, and strong upper
level divergence create the prefect environment for
thunderstorms. Upper air sounding also shows a low freezing
level with Hail CAPE in the hundreds J/kg for the same area,
thus small hail is forecasted for the afternoon. Cant rule
out the possibility of max hail size up to 0.75 for the above
mentioned northern areas. The inverted V sounding and current
high-res models point to the possibility of gusty NW winds for
the region. Areas with thunderstorm threat could see much higher
wind gusts up to 40 mph.

High temperatures will be around average across the north,
reaching into the lower 60s before the cold front moves through.
Temperatures will rise a little more Downeast, reaching into the
mid-60s. By tonight, the cold front should move out to the Gulf
of Maine, bring cooler and drier air into the region. Expect
clearing skies and below normal temperatures.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
A very dry post-frontal air mass will set up across northern and
eastern Maine on Friday with highs ranging from the low 60s
across the north to low 70s Downeast. Temperatures overnight
Friday night will cool into the 30s to low 40s with generally
favorable radiational cooling conditions, although cloud cover
will begin to build in across western parts of the forecast area
after midnight. Frost is likely across northern Maine.

By Saturday a 500 mb shortwave trough moving across Quebec will
help transport a more moisture-rich air mass across the area
from the southwest, leading to the return of diurnal convection
Saturday afternoon. The degree of moisture return remains
uncertain, but enough instability should develop regardless for
a chance of thunder. It will be nearly the warmest day so far
this year with highs around 70 across a majority of the area. By
Saturday night a weakening cold front associated with the
departing shortwave trough will clip northern Maine, causing
showers to linger into the evening. Cloud cover and greater low
level moisture will keep lows from falling below the 40s. While
not mentioned in the forecast currently, areas that receive rain
during the day Saturday will be subject to patchy fog
development overnight.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Seasonable temperatures and chances for diurnal convection will
continue Sunday into next week as a 500mb ridge builds across
eastern Canada and Maine. Sunday looks particularly active with
showers and thunderstorms as a weak upper level low undercuts
the building ridge and enhances mid-level lapse rates. Activity
on Monday will be more scattered without any significant
forcing mechanisms in the area. A 500 mb shortwave trough and
surface cold front will approach the area Monday night into
Tuesday. There are significant discrepancies among guidance regarding
timing and trajectory of this feature. However, regardless of
the outcome the feature will help maintain chances for showers
and possibly thunderstorms until it passes. Overnight lows
during the period from Sunday to Wednesday are expected to
remain in the 40s with limited potential for frost.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
NEAR TERM: Generally expect VFR conditions Thursday, though
local MVFR conditions are possible during the afternoon with any
showers. An isolated thunderstorm with small hail is also
possible across northern/central portions of the forecast area
Thursday afternoon. NW winds will increase to 10-15 kts with
gusts up to 20 kts for all terminals. Gusts could be much higher
in thunderstorms near 40 kts. Returning to VFR by tonight with
decreasing winds and drier conditions.


SHORT TERM: Friday to Friday night...VFR with NW wind gusts to
20 kts during the afternoon.

Saturday...VFR except tempo MVFR/IFR in thunderstorms. Light SSW
winds outside of showers and thunderstorms.

Saturday night...VFR. Lower visibility possible in patchy fog.

Sunday...VFR except tempo MVFR/IFR in thunderstorms. Light winds
outside of showers and thunderstorms.

Sunday night...VFR.

Monday...VFR except tempo MVFR/IFR in thunderstorms. South winds
gusting to around 15 kts.

&&

.MARINE...
NEAR TERM: Winds and seas will remain below SCA for today and
tonight. Wind gusts will increase this afternoon to around 20
kts as a cold front crosses the waters. Waves between 1-3 ft.


SHORT TERM: Winds and seas will remain below SCA criteria
throughout the period.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.

&&

$$

Near Term...VJN
Short Term...MStrauser
Long Term...MStrauser
Aviation...VJN/MStrauser
Marine...VJN/MStrauser