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.