Friday, November 17, 2023

Mid-November Subtropical Storm Update Two

































000
FXUS61 KCAR 180210
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
910 PM EST Fri Nov 17 2023

.SYNOPSIS...
A cold front crosses the area tonight and Saturday as a coastal
low passes well to the south then southeast. Weak high pressure
builds in Saturday night, followed by a secondary cold front
crossing the area on Sunday. High pressure then builds in Sunday
night through Monday night, then slides to the east on Tuesday.
A storm system approaches from the west Tuesday night, then
crosses the area on Wednesday.

&&

.NEAR TERM /THROUGH SATURDAY/...
9:10 PM Update: A band of pre-frontal rain extends from
northeast Aroostook County southwest into Piscataquis County.
A cold front is currently across the Saint Lawrence River
Valley of Quebec. The front will cross into western Maine around
midnight, and should be down along the coast by 12Z Saturday.
Rain will continue to overspread most areas during the next few
to several hours as rain is falling upstream of the area in
northern NY and VT. The rain may not make it to the Washington
County coast until around or even after daybreak. Have made some
adjustments to the PoPs based on the latest radar trends.
The rain will change to a period of snow across the north
overnight. Drier air filters in across the northwest zones late
tonight, and the best chance of picking up a quick inch of snow
will likely be across northeast Aroostook County early Saturday
morning.

Previous discussion:
The region remains under SW flow aloft tonight. Increasing low
level frontogenesis along with a passing shortwave at 700mb will
bring rain to the region from NW to SE tonight. The rain should
mix with or change to all snow over far NW zones as it tapers
off there late tonight. Temperatures across the North should
fall off late tonight with the passage of a cold front, while
temperatures elsewhere should not fall off much, if at all from
current levels. So lows will have a broad range from the lower
30s across far NW Maine to the lower 50s near the immediate
coast. trough of low pressure

A northern stream shortwave trough builds into the area
Saturday. The main forecast question is how quickly does
precipitation tapper off from NW to SE as the main frontogenetic
forcing exits to the SE. High resolution models are faster than
the global models, but still show a bit of a range. NW areas
should dry out during the morning and possible NE Aroostook and
portions of the Central Highlands as well. The remainder of the
area should see rain continue into the afternoon, with far E
Washington County seeing rain linger the longest, possibly into
the evening. Across the north there is a 1-2 hour window where
the rain could mix with or change to all snow before the
precipitation tapers off. At this time any accumulation should
be very spotty, with less than 1/2 an inch likely at any given
location, mainly on grassy surfaces. Highs on Saturday will
occur in the morning across the North with gradually falling
temperatures through the day, but should see some early
afternoon highs elsewhere, depending on the exact timing of the
front. Highs on Saturday should range from the mid 30s to the
lower 50s.

As the colder air builds in behind the front, any wet
untreated surfaces could form black ice, mainly across the North
late Saturday afternoon. This threat is mentioned in the HWO.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
Lingering snow showers, and rain showers near the coast, will
quickly push off to the east. Breezy northwest winds will linger
through the night, advecting cold air into the area and
lowering temperatures down to the low to mid 20s overnight.

Sunday into Sunday night a weak shortwave will provide some
instability to the area, that combined with northwest winds off
the St. Lawrence river could lead to scattered snow showers
through the day. A small but non-zero amount of CAPE is seen on
forecast soundings, along with steep lapse rates across the
North Woods and into the Central Highlands. The threat for these
snow showers will decrease into the overnight hours as the
shortwave moves east and any diurnally driven instability is
lost.

Skies will begin to clear into the day on Monday as high
pressure returns to the area. High temperatures will be cooler
with highs around freezing across the north and into the mid 30s
closer to the coast.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Clear skies Monday night will lead to prime radiational cooling
conditions, especially should any snow cover linger across the
north from the previous systems. What could limit cooling Monday
night would be if cloud cover lingers across the northwest or if
winds hang longer than expected. West to northwest winds may
advect low level moisture into the area just above the
inversion, which would be the most likely cause for temperatures
not falling into the teens. Current forecast is for enough
clearing such that full radiational cooling does occur. High
pressure will linger through the day on Tuesday, with high
temperatures slightly below average for this time of the year.

For Wednesday, recent runs of the GFS have brought in a less
amplified ridge across the Mid-Atlantic through the early week,
placing the left exit region of the mid-week jet streak over the
Gulf of Maine. Meanwhile, the 00z run of the ECMWF maintains
the high amplitude ridge, which puts the left exit region of the
jet streak over the Downeast region. This is part of the cause
for whether a triple point low develops over our area and later
in the evolution of the occluded low to the north, or whether a
coastal low develops and rides up into Nova Scotia. With all
that said, there remains substantial run to run variation in all
models with this system. The GFS has trended further and further
south with the development of the coastal low, while the
Canadian progresses the system more quickly, and the ECMWF
maintains a steady track with the triple point low moving
through the state of Maine. Leaned towards the NBM solution for
this forecast with this uncertainty, backing off slightly from
PoPs given timing and placement questions. The positioning of
the low pressure will also have significant impacts to how
strong winds will be, though some solutions, such as the 06z
GFS, suggest strong, potentially damaging winds for Wednesday
night into early Thursday morning, and this storm will continue
to be closely tracked due to these chances.

A ridge of high pressure will return behind the trough through
the day on Thursday, lasting through the end of the week.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
NEAR TERM: Ceilings are variable as of 02Z ranging from MVFR to
VFR. The trend will be for the ceilings to lower to IFR
overnight. Conditions will improve to MVFR at the Aroostook
terminals by Sat PM and to VFR at KBGR and KBHB by late in the
day.

S wind 10 to 15 knots and gusty through late this evening,
shifting NW 5 to 10 knots with the passage of a cold front. N
wind increasing to 10 to 15 knots and gusty by late in the day
Sat.

LLWS into tonight at all terminals, ending from NW to SE
overnight.

At northern terminals there could be a 1-3 hour window of
rain/snow mix if not all snow before the precipitation ends late
tonight/Saturday morning with the best chance from KPQI to KFVE.

SHORT TERM:
Saturday night...Improving to VFR late. NW 10 to 15 kts with
gusts 20 to 25 kts early before diminishing.

Sunday-Monday...Mainly VFR with MVFR cigs with light -shsn from
GNR/HUL and north. W 5 to 10 kts becoming NW 10 to 15 kts on
Monday.

Monday night-Tuesday...VFR. W 5 to 10 kts becoming S Tue.

Wednesday...Approaching storm leading to cigs falling to MVFR,
likely IFR across northern terminals with snow. SW winds
increasing to 10 to 20 kts with gusts increasing to 25 to 30
kts.

&&

.MARINE...
NEAR TERM: SCA conditions on all waters through Saturday. There
could be a brief lull at some point during the day on Saturday,
but with the gale risk looking more likely Saturday night than
late Saturday afternoon, have opted to extended the SCA through
the day on Saturday on all waters.

SHORT TERM: Winds increase toward gale force Saturday night
with seas building toward 10 ft into Sunday morning. NW winds
gusting to around 35 kts over the outer waters before dropping
to below 20 kts on Sunday. SCA likely needed through Monday.
Winds and seas drop below SCA levels Monday night and Tuesday.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory until 6 PM EST Saturday for ANZ050>052.
     Gale Watch from Saturday evening through late Saturday night
     for ANZ050>052.

&&

$$

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


Hazardous Weather Outlook...CORRECTED
National Weather Service Caribou ME
258 PM EST Fri Nov 17 2023

MEZ001>006-010-011-015>017-029>032-182000-
Northwest Aroostook-Northeast Aroostook-Northern Somerset-
Northern Piscataquis-Northern Penobscot-Southeast Aroostook-
Central Piscataquis-Central Penobscot-Southern Penobscot-
Interior Hancock-Central Washington-Coastal Hancock-
Coastal Washington-Southern Piscataquis-Northern Washington-
258 PM EST Fri Nov 17 2023

This Hazardous Weather Outlook is for Central Highlands Maine,
Coastal DownEast Maine, Far Eastern Maine, Far Northern Maine,
Interior DownEast Maine, North Woods Maine and Penobscot Valley
Maine.

.DAY ONE...This afternoon and tonight.

Hazardous weather is not expected at this time.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.
Black ice could form on untreated wet surfaces late Saturday
afternoon and night as temperatures fall below freezing.

Wintry precipitation is possible toward the middle of next week.
Strong southerly winds appear possible with this system. People with
travel interests are encouraged to check the forecast as the time
approaches.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.

$$


9:50 PM AST Friday 17 November 2023
Maximum wind gusts: possibly reaching 90 km/h.

Location: most of the Island.

Time span: overnight Saturday.

Remarks: Strong northwest winds are forecast in the wake of a low pressure system later Saturday night.

Please continue to monitor alerts and forecasts issued by Environment Canada. To report severe weather, send an email to PEstorm@ec.gc.ca or tweet reports using #PEStorm.


9:48 PM AST Friday 17 November 2023
Strong winds that may cause damage are expected or occurring.

Maximum wind gusts: 90 to 100 km/h.

Locations: Guysborough and Antigonish counties, as well as Cape Breton.

Time span: beginning Saturday evening, ending overnight.

Utility outages may occur.

Wind warnings are issued when there is a significant risk of damaging winds.

Please continue to monitor alerts and forecasts issued by Environment Canada. To report severe weather, send an email to NSstorm@ec.gc.ca or tweet reports using #NSStorm.


9:45 PM AST Friday 17 November 2023
Rain, at times heavy, is expected.

Total rainfall: near 50 mm.

Location: Queens and Kings counties.

Time span: Saturday night.

Remarks: Periods of rain will develop Saturday morning and will become heavy in the evening before tapering to scattered showers near midnight.

Localized flooding in low-lying areas is possible.

Rainfall warnings are issued when significant rainfall is expected.

Please continue to monitor alerts and forecasts issued by Environment Canada. To report severe weather, send an email to PEstorm@ec.gc.ca or tweet reports using #PEStorm.


9:44 PM AST Friday 17 November 2023
Rain, at times heavy, is expected.

Total rainfall: 50 to 70 mm, with locally up to 100 mm possible.

Location: most of Nova Scotia.

Time span: beginning Saturday, ending Saturday night.

Remarks: Heavy rain will spread from west to east across Nova Scotia as a low pressure system approaches. The heaviest rainfall rates are expected later in the afternoon and into the evening as the center of low pressure tracks across the province Saturday night.

In addition, there is the possibility of elevated water levels near high tide late Saturday night or early Sunday morning for Atlantic coastal communities in eastern Nova Scotia. 

Similar storms in the past have caused hazardous driving conditions from water pooling on roadways and localized flooding, especially in poor drainage areas.

Heavy downpours can cause flash floods and water pooling on roads. Localized flooding in low-lying areas is possible.

Watch for possible washouts near rivers, creeks and culverts.

Rainfall warnings are issued when significant rainfall is expected.

Please continue to monitor alerts and forecasts issued by Environment Canada. To report severe weather, send an email to NSstorm@ec.gc.ca or tweet reports using #NSStorm.

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