Intensifying low pressure slowly tracked northeast across the region from late on the 21st into the 22nd before exiting across the Maritimes. Enough cold air existed north and west of the low track to support snow across northern Maine.
Every event with a place to put it; 7 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS CAR wrote it up.
Intensifying low pressure slowly tracked northeast across the region from late on the 21st into the 22nd before exiting across the Maritimes. Enough cold air existed north and west of the low track to support snow across northern Maine. Snow developed during the morning of the 21st. The snow diminished and transitioned to rain across northeast areas through the morning into the afternoon of the 21st. However, colder air persisted across northwest areas through the 22nd into the early morning hours of the 23rd allowing for an extended snow event with the upper low. Storm total snow accumulations across northeast areas generally ranged from 2 to 6 inches...with 6 to 10 inches across northwest areas. The greatest totals generally occurred across the higher terrain of the Saint John Valley and along the northwest Aroostook county border with Quebec province.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Caribou, ME wrote its last area forecast discussion before the first event at Apr 21, 5:30 AM EST, 30 minutes earlier.
Area Forecast Discussion
National Weather Service Caribou ME
630 AM EDT Wed Apr 21 2021
.SYNOPSIS...
Low pressure will approach this afternoon. A strong cold front
moves through the area on Thursday with an upper level
disturbance remaining through the end of the week. High pressure
builds into the region Saturday, quickly followed by low
pressure passing south of the area late Sunday.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
6:30AM Update: SPC has updated their thunderstorm maps to
include Downeast. Updated the weather to show a slight chance
of thunderstorms this afternoon. Radar and obs show the rain has
started on the south, but the system is quickly moving
northward. Updated the current obs for temp and winds. The rest
of the forecast looks good.
Previous Discussion...
The warm front associated with low pressure centered over
Pennsylvania has begun to push into the region, bringing rain
into southwestern Maine and Downeast. As the warm front advances
NE into the Central Highlands, the warm air advection south of
the boundary will follow along. Recent 1000-850mb thickness
model runs show the cold air sticking around the St John Valley,
North Woods and possibly Central Aroostook for the rest of the
day. These temperature differences will be a key factor in the
rain/snow line across the region.
By the afternoon, the front will stall over the northern region,
causing steady precip for the rest of the day. Recent QPF model
runs and WPC guidance show large amounts of moisture linked
with this system. With colder temps and higher snow ratio,
there’s a possibility for large snow amounts in the North
Woods, especially for this time of year. A Winter Weather
Advisory has been issued for the North Woods and St John Valley
starting this afternoon. Temperatures north of the boundary are
expected to be in the upper 30s while below the boundary should
range from the low 40s to the low 50s. Areas to the south of the
boundary will also see significantly less rain than the rest of
the region due to the N movement of the front.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
A significant Spring storm will impact the area with gusty
winds, rain, and even snow across northern areas through the
period. Pressure falls are noted this morning across
Pennsylvania and New York as an upper level trough approaches
the area. An embedded shortwave will rotate around the trough
later today into tonight, leading to a rapidly deepening area of
low pressure that will then move across central New England and
into central and southern Maine by tonight. The low has
developed slightly southeast of where guidance had it the last
couple cycles and an adjustment in low track to the southeast
has occurred with the low now expected to track across Downeast
Maine and northeast to around Houlton by 6z Thursday. This
slight shift to the southeast will enable colder air to remain
over a larger swath of the North Woods, leading to a period of
moderate to locally heavy snow tonight as a deformation zone
forms northwest of the low track. A Winter Weather Advisory has
been issued over the North Woods, where significant
accumulations are expected near the Quebec border. Snow will
accumulate heaviest this evening across the advisory area, but
otherwise the event should be spread out over 24 to 48 hours.
Both the 12 and 24 hour warning criteria amounts will be
approached and are forecast to be exceeded over a small part of
zones 1 and 3 near the Quebec border. However, upgrades to
warnings may be necessary if a persistent band sets up over a
majority of one or more of the aforementioned zones.
Colder air will work eastward during the day Thursday as the
surface low pulls northeastward into the Canadian Maritimes,
changing precipitation over to snow across much of Aroostook
County. Despite the April sun angle and temperatures around or
slightly above freezing, snowfall rates will be sufficient for
accumulation, especially across northern Aroostook County where
a couples inches are expected east of the advisory area.
Depending how banding evolves Thursday, the advisory may need to
be expanded and/or extended in time to include northeast
Aroostook County. The steep pressure gradient from the departing
low will also result in strengthening wind gusts. Winds may also
approach advisory criteria across the entire area and lead to
patchy blowing snow by Thursday night as temperatures drop into
the 20s and snow showers/bands persist. Strong winds will also
cause damage to trees and possibly power lines where moderate to
heavy snow accumulation occurs.
Lingering showers will retreat northward during the day Friday,
becoming confined to the Saint John Valley and eventually
tapering off by the afternoon. Temperatures will be near to
slightly below normal with highs ranging from the mid 40s across
the north to mid 50s Downeast. The main story will be winds as
the departing low continues to produce a steep pressure gradient
with gusts of 35 to 45 mph. Winds will finally diminish Friday
evening, though most areas will maintain enough of a breeze to
limit decoupling and keep lows from falling below the 30s in all
but the most sheltered valleys.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
High pressure will build in for the day Saturday with partly to
mostly sunny skies and temperatures in the 50s and 60s. A
coastal low will approach the area Sunday as a southern stream
shortwave interacts and tries to phase with the northern stream
trough. The antecedent air mass should be warm enough to support
a mainly rain event, though a stronger and slightly northwest
track associated with earlier phasing of the two aforementioned
features could result in some mixing with wet snow across far
northwestern areas as shown on the 0z Euro. The low will be slow
to depart the area as a negative NAO and upstream blocking
develops over Greenland. Lingering showers are possible into
Monday evening, but quieter weather should eventually win for
Tuesday with slightly warmer temperatures.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: VFR for early morning with LLWS at all terminals
until sunrise. MVFR with possible IFR/LIFR clgs and vsby once
the rain/snow begins in the early morning. WSW winds should
switch to S winds for southern terminals and NE winds for
northern terminals 5-10 kts
SHORT TERM:
Tonight-Thu...IFR/LIFR cigs and vsby with snow for N terminals
and rain Downeast tonight. LLWS possible tonight. Across
northern areas, generally IFR conditions with snow Thursday.
Across Downeast areas, generally VFR/MVFR with occasional IFR
with any snow showers Thursday. E winds 5-10 kts tonight,
becoming WNW 15 to 25 kt with gusts up to 40 kts Thursday.
Thu night-Fri...MVFR cigs across the north with light snow. VFR
Downeast terminals. Winds W 10-20kts with gusts up to 40kts.
Fri night-Sat night...VFR. Winds W 10kts becoming light S Sat
night.
Sun- Sun night...Becoming MVFR/IFR in the afternoon in rain.
Winds S 5-15kts.
&&
.MARINE...
NEAR TERM: Winds are expected to increase to SCA levels late
this afternoon into tonight. Seas generally 1 to 3 ft through
this afternoon increasing to 3 to 6 ft late.
SHORT TERM: A Gale Warning is in effect Thu morning, with seas
4-7 ft, increasing to 10-12 feet on the outer waters Thu evening
before gradually diminishing Friday morning. Gale force winds
are expected on the outer waters Fri morning through the
afternoon. SCA conditions will then continue into Sat morning.
Seas and winds expected diminish below SCA levels Sat afternoon
to Sun morning before SCA and possibly gale conditions return
later Sun into Sun night.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory from 2 PM this afternoon to 4 PM EDT
Thursday for MEZ003-004.
Winter Weather Advisory from 2 PM this afternoon to 4 AM EDT
Friday for MEZ001.
MARINE...Gale Warning from 8 AM Thursday to 4 PM EDT Friday for
ANZ050>052.
&&
Near Term...LaFlash
Short Term...MStrauser
Long Term...MStrauser
Aviation...LaFlash/MStrauser
Marine...LaFlash/MStrauserHazardous Weather Outlook...CORRECTED National Weather Service Caribou ME 545 AM EDT Wed Apr 21 2021 MEZ002-005-010-220945- Northeast Aroostook-Northern Penobscot-Central Piscataquis- 545 AM EDT Wed Apr 21 2021 This Hazardous Weather Outlook is for Central Highlands Maine and Far Northern Maine. .DAY ONE...Today and Tonight. Hazardous weather is not expected at this time. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. A mix of rain and snow will transition to all snow Thursday. A light to locally moderate accumulation is possible. Strong wind gusts are also possible late Thursday through Friday. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to Standard Operating Procedures. MEZ003-004-220945- Northern Somerset-Northern Piscataquis- 545 AM EDT Wed Apr 21 2021 ...WINTER WEATHER ADVISORY IN EFFECT FROM 2 PM THIS AFTERNOON TO 4 PM EDT THURSDAY... This Hazardous Weather Outlook is for North Woods Maine. .DAY ONE...Today and Tonight. Please listen to NOAA Weather Radio or go to weather.gov on the Internet for more information about the following hazards. Winter Weather Advisory. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Please listen to NOAA Weather Radio or go to weather.gov on the Internet for more information about the following hazards. Winter Weather Advisory. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to Standard Operating Procedures. MEZ001-220945- Northwest Aroostook- 545 AM EDT Wed Apr 21 2021 ...WINTER WEATHER ADVISORY IN EFFECT FROM 2 PM THIS AFTERNOON TO 4 AM EDT FRIDAY... This Hazardous Weather Outlook is for Far Northern Maine. .DAY ONE...Today and Tonight. Please listen to NOAA Weather Radio or go to weather.gov on the Internet for more information about the following hazards. Winter Weather Advisory. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Please listen to NOAA Weather Radio or go to weather.gov on the Internet for more information about the following hazards. Winter Weather Advisory. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to Standard Operating Procedures. MEZ006-011-015>017-029>032-220945- Southeast Aroostook-Central Penobscot-Southern Penobscot- Interior Hancock-Central Washington-Coastal Hancock- Coastal Washington-Southern Piscataquis-Northern Washington- 545 AM EDT Wed Apr 21 2021 This Hazardous Weather Outlook is for Central Highlands Maine, Coastal DownEast Maine, Far Eastern Maine, Interior DownEast Maine and Penobscot Valley Maine. .DAY ONE...Today and Tonight. Hazardous weather is not expected at this time. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Strong wind gusts are possible Thursday afternoon through Friday. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to Standard Operating Procedures. ANZ050>052-220945- Coastal Waters from Eastport, ME to Schoodic Point, ME out 25 NM- Coastal Waters from Schoodic Point, ME to Stonington, ME out 25 NM- Intra Coastal Waters from Schoodic Point, ME to Stonington, ME- 545 AM EDT Wed Apr 21 2021 ...GALE WARNING IN EFFECT FROM 8 AM THURSDAY TO 4 PM EDT FRIDAY... This Hazardous Weather Outlook is for Atlantic Coastal Waters. .DAY ONE...Today and Tonight. Hazardous weather is not expected at this time. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Please listen to NOAA Weather Radio or go to weather.gov on the Internet for more information about the following hazards. Gale Warning. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to Standard Operating Procedures.
The national radar mosaic for the moment the first event began.
7 winter weather. Local standard time, as filed.
Storm total snow accumulations ranged from 3 to 6 inches.
Storm total snow accumulations ranged from 3 to 6 inches.
Storm total snow accumulations ranged from 2 to 4 inches.
Storm total snow accumulations ranged from 3 to 6 inches.
Storm total snow accumulations ranged from 5 to 8 inches.
Storm total snow accumulations ranged from 6 to 10 inches.
Storm total snow accumulations generally ranged from 6 to 10 inches...with locally greater accumulations along the northwest border with Quebec province.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maine in 2021Every state in 2021This day in weather historyWarnings in Maine, April 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 955922, 955923, 955924, 955925, 955926, 955927, 955928.