Winter Storm Orlena Update One

000

FXUS61 KCAR 310510

AFDCAR

Area Forecast Discussion

National Weather Service Caribou ME

1210 AM EST Sun Jan 31 2021

.SYNOPSIS...

High pressure will build toward the region overnight, then

cross the region through Monday morning. Low pressure will

approach from the south Monday, and track northeast into the

Maritimes by Wednesday. High pressure will build in on Thursday.

&&

.NEAR TERM /THROUGH SUNDAY/...

12:10 AM Update: A three dog night across the FA as temperatures

tumble under a clear sky. Some clouds may try to back into far

northeast Maine toward daybreak, but this will be too late for

any impact on our low temperatures. The temperature is down to

16 below at Estcourt Station and Big Black River as of midnight.

Made some tweaks to lower the hourly temperatures and overnight

lows. The broad northwest valleys will likely drop into the 20

to 25 below range overnight with the potential that some spot in

the FA ends up with the contiguous U.S. cold spot.

Previous Discussion... High pressure will continue to ridge

down across the area from the north on Sunday with partly/mostly

sunny skies across the region. Afternoon high temperatures will

range from around 20 degrees across the north and low to mid

20s central and Downeast.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...

High pres will drift across eastern Canada Sunday night into Monday

w/cold air damming setting up. Low pres moving across the Ohio River

Valley will weaken during the day on Monday w/energy in the upper

levels being transferred to the Delmarva. This in turn will allow

for secondary development as the energy diving down the backside of

the upper trof will lead to rapid intensification as the low

lifts ne. In the meantime, Sunday night looks to be chilly night

w/some areas seeing temps below zero w/that high to the n

keeping thicker clouds at bay. Some areas such as the Allagash

and North Woods, could be seeing readings apchg -5F or perhaps

even colder. Light winds, mostly clear skies and snow cover will

be a good setup for it. Monday will see increasing clouds which

will aid in halting temps back a biT, but still above normal

for the beginning of February.

Monday night into Tuesday will feature clouds continuing to thicken

with snow lifting into the srn areas later at night, and then

gradually lift up across central and then into northern areas

on Tuesday. The latest runs of the model guidance including the

GFS/NAM and ECMWF appear to have shifted the low further e,

which in turn keep colder temps in, allowing for more snow as

far s as the coast. There are some timing and placement

differences, but a good swath of the individual ensemble members

of the GFS and ECMWF point to the potential for a sanguined, if

not major storm. Negatively tilted trof, upper difluence and

strong upper level jet leading to strong intensification.

Tapping of Gulf and Atlantic moisture being pulled into the NErn

US. There is potential for some heavy snowfall rates on Tuesday

w/strong deformation possibly setting up, especially later in

the day continuing into Tuesday night. More on that below. There

is still some risk of snow going to rain especially for the

coast and extreme eastern Washington County as some warmer air

gets pulled into coast. Despite the latest shift in the track by

the model guidance, preferred to stay w/consistency and kept

the threat for a changeover to rain later in the day on

Tuesday/Tuesday evening. If the trend continues for a track

over the Gulf of Maine waters, then the rain-snow line may need

to be shifted further s. Sleet is also concern as GYX pointed

out the warm layer at 850- 700mbs coming w/this strengthening

system, which the ECMWF shows being prolonged. This would lead

to a significant accumulation of sleet. After coordinating

w/GYX, decided to keep the mention of sleet out of the forecast

for now given it is 5-6th period. As if to add to the mix, winds

are also a concern especially across the Downeast region w/llvl

jet of 50+ kt from the ENE. This could only hamper things

especially if heavy snow sets up w/whiteout conditions a

possibility if this setup is realized.

One last item is the potential for some splashover at the time

of high tide given the prolonged ENE wind into Tuesday night.

Seas building to 10-12 ft w/in the 20 foot zone could allow

large breakers leading to the splashover.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...

Snow, heavy at times w/some sleet Tuesday night w/some high

snowfall rates(possibly 1-2"/hr), especially across the Maine

Central Highlands into Northern Maine. The intensifying low

looks like it through the Bay of Fundy which is a good marker

for heavy snowfall across the region especially northern areas.

The snow is expected to gradually wind down on Wednesday from s

to n, w/far northern areas seeing snow continuing into the early

afternoon, before winding down. A foot or more snow is possible

across Northern and portions of the Maine Central Highlands.

Remaining unsettled into Thursday as the upper trof swings

across the region leading to clouds and flurries. A break early

Friday w/some weak ridging and partial clearing. This will

short-lived as a weak system lifting across the region could

bring some light precip in the form of snow to the region, w/the

highest percentages across Downeast areas. The beginning to the

weekend looks to be rather dry per the ECMWF guidance, while

the GFS is more aggressive w/the next system and threatens to

bring snow/rain to the region. Attm, it does not look like

anything too heavy. High confidence that temps will average

above normal during this stretch.

&&....