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000
FXUS61 KCAR 270108
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
908 PM EDT Mon Jul 26 2021

.SYNOPSIS...
A cold front will pass through the region overnight and
Tuesday. High pressure builds down from Canada from Wednesday
night, then slides offshore on Thursday. A low pressure system
approaches from the west late Thursday, then crosses the area on
Friday. This low then slowly lifts northeast through the
Canadian Maritimes as high pressure builds in from the west to
close the week.

&&

.NEAR TERM /THROUGH TUESDAY/...
9:08 PM Update: The 00z Caribou sounding showed a small cap at
around 600 millibars, and that was likely what caused convection
to have a tough time developing this afternoon.

A cold front is now approaching the FA from Quebec. The front
has a broken line of showers and thunderstorms that stretch
from north of the Saint John Valley back across the Saint
Lawrence River Valley in Quebec.

Elsewhere, there is just one lone thunderstorm that developed
in northern Penobscot County and is now approaching the route 1
corridor between Bridgewater and Monticello. There will be some
cloud to ground lightning and brief heavy downpours with this
storm. Potential for some small hail and a brief gust of wind.

The best chance of showers with embedded isolated convection
late this evening and into the overnight will be across the
northern half of the FA. Loaded the past few hours of observed
data and made some minor tweaks based on the current and
expected conditions for the remainder of tonight.


Previous discussion:
There is a front just arriving at the St Lawrence River in
Quebec. A line of storms can be noted with this front, and have
opted to keep the mention of storms into the evening, with more
emphasis across the north as NAMnest, RAP, HRRR suggest.

Fog is expected to push back into the coastal communities and
Downeast tonight, locally dense.

Decided to remove the chance of rain for Tuesday given the deep
dry layer moving in. There are good lapse rates through the
mid/low levels, so clouds should develop. The good mixing
conditions will also make it a tad breezy, but nothing too
strong.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
A shortwave rotates around the base of the cutoff low over SE
Quebec Tuesday night and Wednesday. The shortwave should cause
an area of low pressure to develop along a cold front offshore
late Tuesday night, that then passes just to the S/E of the area
early Wednesday morning. Based on this it should be dry Tuesday
night and Wednesday, except for possibly some light rain or
showers along the Downeast coast late Tuesday night/Wednesday
morning, depending on the exact track and strength of the
coastal low. Lows Tuesday night should be around 5-10 degrees
above normal across the North (mainly mid-upper 40s) and near to
slightly below normal elsewhere (mainly around 50 to mid 50s).
Highs Wednesday should be around 5 degrees below normal, mainly
from around 70 to the mid 70s.

Weak northern stream shortwave ridging builds in Wednesday
night, then passes to the east on Thursday. It should be dry
Wednesday night and at least Thursday morning as a result. An
approaching shortwave could bring some showers and possibly a
rumble of thunder to mainly western zones by late Thursday
afternoon. However, there is quite a bit of uncertainty with
respect to the timing of this shortwave, with some indication
this precipitation could ultimately end of holding off until
Thursday night. Lows Wednesday night should be around 5 degrees
below normal and highs on Thursday slightly below normal.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Noting that the GFS is more aggressive than most other models
with the timing of the shortwave for Thursday night/Friday,
opted for a non-GFS solution during this time frame. As a
result, expect a northern stream shortwave to approach Thursday
night, then lift across Maine on Friday. Have likely pops for
showers everywhere Thursday night and then likely pops mainly
across the North and chance pops elsewhere on Friday. Given the
forecast cool temperatures aloft, also have a slight chance of
thunder in everywhere as well Thursday night and Friday.

The region remains under the influence of a cutoff low over
far SE Quebec Friday night and Saturday. So given the proximity
of the cold pool aloft, have chance pops across the North,
slight chance pops elsewhere, tapering of from S to N during the
day on Saturday.

A northern stream shortwave ridge is progged to cross the region
Saturday night. Still some uncertainty on this so did maintain
slight chance to chance pops across mainly the NW 3/4 of the
CWA.

A northern stream shortwave trough crosses the area on Sunday,
warranting chance pops.

Another closed low tracks into eastern Quebec Sunday night and
Monday (once again model differences on the timing - but given
the blocky nature of the pattern, generally leaned towards
slower solutions), warranting continued chance pops for showers.

It should be noted, that with the two cutoff/closed lows for
late this week/early next week, that in general from Friday
night on, the precipitation will be of a hit and miss nature,
with it more likely to miss than hit at any given location at
any given time.

Lows Thursday night should be near normal, followed by below
normal temperatures Friday-Monday.

&&

.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: Hazy skies, otherwise VFR for Aroostook terminals.
Isolated showers and thunderstorms through early Tuesday
morning. IFR to LIFR possible with fog developing Downeast,
namely BHB late this evening and overnight. BGR may also see
IFR vis late in BCFG. Light and variable wind, except brief
gusty wind in/near any thunderstorms.

VFR w/ breezy WNW afternoon winds 10 to 15 knots Tuesday as
remaining fog lifts in AM.


SHORT TERM:
Tuesday night...VFR, except MVFR or lower possible at Downeast
terminals.

Wednesday-Thursday morning...VFR.

Thursday afternoon-Friday...Variable conditions with showers
and thunderstorms.

Friday night-Saturday...VFR at southern terminals, with MVFR or
lower possible at northern terminals. NW winds G15-20KT possible
Saturday.

&&

.MARINE...
NEAR TERM: Below SCA conditions. Main item will be dense fog
again over the waters tonight, lifting Tuesday AM. SW winds
Tuesday gusting around 15 kts.

SHORT TERM: Sub-SCA conditions are expected on all waters
Wednesday night-Saturday. Some wind gusts to around 20 kt are
possible on the coastal waters mainly Thursday and Thursday
night.

&&

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

&&

$$

Near Term...CB/Cornwell
Short Term...Maloit
Long Term...Maloit
Aviation...CB/Cornwell/Maloit
Marine...CB/Cornwell/Maloit