Winter Storm in Maine, April 9 to 10, 2020

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1113 AM EDT Thu Apr 9 2020

.SYNOPSIS...
Weather will turn nasty today as a strong coastal storm develops
in the western Gulf of Maine. There will be heavy rain, heavy
snow, and along the coast even some strong wind gusts. The storm
will move quickly out of the area tonight leaving behind cooler
temperatures and snow showers in the mountains. High pressure
returns on Saturday with temperatures running above normal this
weekend. The next system arrives Monday with heavy rainfall
possible.

&&

.NEAR TERM /THROUGH TONIGHT/...
11 AM Update...
Have made a few changes to the forecast database based on latest
CAM model runs which brings more snow to northern Grafton, N.
Carroll, the fishtail of Cumberland, and Androscoggin Counties
as well as the Mid Coast. All these areas have been upgraded to
either warnings or advisories based on the heavy snow expected
later this evening.

Steady rain as arrived over much of southern and central NH and
is currently pushing into western Maine. This trend will
continue as well as an increase in intensity over the next
several hours. Rain will gradually change over to moderate to
heavy snow as lifting for ascent increases and omega coincides
with the DGZ...resulting in snowfall amounts more than 3" an
hour for a short while. Thundersnow is likely over the mainly
southern NH and along portions of the Maine coast as the lapse
rates really steepen.

Update...Minor changes to reflect latest observational trends.

***SIGNIFICANT LATE SEASON SNOWFALL LIKELY BEGINNING THIS
 AFTERNOON***

A very dynamic late season winter storm will develop along the
Wrn ME coastline this afternoon. Low pressure is forecast to
drop into the low 970s in the vicinity of Penobscot Bay.

Key to the forecast is rapid deepening of mid level
centers...nearly overhead parts of the Wrn ME forecast area.
This will help drive temps aloft down to at or below zero.
Additional melting of snow aloft will also help to cool the
column. I favored hi-res guidance that dynamically cooled much
of Wrn ME into the 33 to 35 degree range during the afternoon.
The HRRR and nested NAM had very reasonable temp patterns given
the expected precip rates and associated cooling. That being
said...highs will be early today...with readings falling in the
afternoon as precip moves in.

With environmental soundings nearly isothermal the rain/snow
line will be prone to significant variability...perhaps even
being driven by precip rates alone at times. Overall I have
cooled the forecast from the previous...with more snow and snow
accumulation across parts of Wrn ME. Forecast soundings show a
rain to heavy snow flip occurring mid to late afternoon across
much of the area N of PWM...save for the immediate coast.
Generally speaking I preferred a snow ratio at or below
10:1...with a nod towards snow amounts using the max temp in the
profile and compaction factored in. I have expanded winter storm
warnings and added winter wx advisories to the S of those. That
still leaves quite a bit of bust potential across Wrn ME on the
Srn edge of headlines and even within the advisory area. Bufkit
soundings around the GYX area suggest 2 to 6 inches possible...5
to 10 inches around AUG...and even 4 to 8 inches around RKD. A
lot of this will depend on exactly where low pressure develops
along the occlusion and where cold air will be locked in aloft.
I believe this forecast provides a good balance between
increased snow and leaving room for additional expansion or
contraction of snow amounts as things develop today.

It is worth mentioning some additional impacts in snow today.
One will be max wet bulb temps around +1C...which is favorable
for wet/heavy snow. This will likely lead to some downed limbs
and power outages. Another will be convectively enhanced
snowfall rates. The intense deepening of the storm coupled with
approaching dry slot will increase instability over some of if
not all of the area. In addition to lightning...and perhaps even
straight thunderstorms over parts of Srn NH...hi-res guidance
shows that snowfall rates this afternoon and evening may
approach 2 to 3 inches per hour. No matter what your temp
is...snow will accumulate on all surface at those rates.

&&

.SHORT TERM /FRIDAY/...
With upper level cyclonic flow remaining overhead and plenty of
low level moisture in place upslope snow and rain showers will
continue into Fri. With flow more Wly than NWly...this will
favor the NH terrain more for appreciable accumulations. Light
to moderate amounts are possible for parts of the Whites N thru
Pittsburg.

Temps will be cool in the wake of the storm...with gusty winds
Fri. Deep mixing in CAA could bring gusts into the 35 to 40 mph
range.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Overview: Northwest flow Friday night continues into Saturday with
lingering snow showers in the northern mountains. High pressure
briefly noses into New England Saturday night before moving off to
the southeast with warm southerly flow developing on Sunday. A large
low pressure system looks to bring significant rainfall to our
region on Monday into Monday night. Drier conditions return for the
rest of the period.

Impacts: Forecast rainfall Monday into Monday night could cause some
localized flooding, particularly when combined with possible
snowmelt from the previous snowfall event and already saturated
soils.

Forecast Details: The low pressure system affecting our region
Thursday and Friday will still be spinning over the Canadian
Maritimes Friday evening, leaving our region on the backside of the
system in northwest flow. As it slowly moves northeast, any
lingering showers will gradually come to an end Friday night, even
in the mountains. Saturday looks dry though a few afternoon snow
showers in the mountains cannot be ruled out and skies will be
partly to mostly cloudy. High pressure nudges into New England late
Saturday and Saturday night and clears out the skies; low
temperatures drop into the mid 20s north and near 30 south for what
looks to be the coolest night of the long term period. Southerly
flow develops on Sunday as the high pressure slides off to the east,
bringing warmer temperatures and increasing clouds during the day.

A potent low pressure system will also begin to take shape over the
Ohio Valley by Sunday evening, and it is expected to be centered
over the Great Lakes by Monday morning. The large system will push
an area of precipitation into our region by Monday morning. The warm
temperatures already in place means that this will be a rainfall
event, even in the mountains. The rain should be coming to an end in
southern areas Monday evening and in northern areas by midnight.
Much like the previous forecast, a widespread 0.75 to 1.5 inches
looks likely for much of the region over the 12-18 hour period.
Probably not out of the question that some isolated areal flooding
occurs with saturated soils and melting snow from the previous
system combining to create additional runoff along with some
area river possibly rising above minor flood stage...so will
continue to monitor QPF trends with this system through the
upcoming weekend.

Warm southwesterly flow dries out the region on Tuesday. Could see
the return of precipitation on Wednesday, but the global
deterministic models are not in solid agreement on that possibility;
went with lower-end chance PoPs as a result.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
Short Term...Mostly VFR conditions this morning...though patches
of IFR CIGs are already developing in onshore flow N of the warm
front. Overall conditions will quickly drop to IFR or lower as
precip moves in from SW to NE around midday. Periods of +RA are
likely at most of the terminals...and across Srn NH especially
there may be some TSRA. Confidence is too low for
prevailing...but I did add PROB30 groups to PSM and MHT. Farther
N AUG will likely see a period of +SN when the heaviest precip
arrives late afternoon. RKD may see surface wind gusts approach
35kt this evening...but it should be a short window for
strongest winds. Dry slot quickly moves in this
evening...bringing an end to heavy precip...but lingering MVFR
CIGs stick around into Fri. Significant upslope SHSN are
expected...with local IFR conditions possible in the vicinity of
HIE.

Long Term...VFR conditions expected through Sunday as high pressure
noses into New England this weekend. Gusty northwest winds on
Saturday will diminish by late Saturday evening with winds
turning southerly on Sunday. Widespread rainfall expected Monday
into Monday evening; clouds move in late Sunday and MVFR/IFR
conditions expected until the precipitation comes to an end from
south to north late Monday.

&&

.MARINE...
Short Term...Coastal storm will rapidly develop in the Gulf of
ME today with conditions deteriorating on the coastal waters.
Gale warnings remain in effect thru Fri. Will have to watch the
CAA behind the deepening low early Fri...where gusts may
approach storm force well outside the bays.

Long Term...Marginal SCA conditions over the outer waters expected
Friday night with winds and seas diminishing on Saturday. Over
the outer waters, southerly flow Sunday night into Monday will
cause seas to build to near 10 ft on Monday before gradually
diminishing through Tuesday and into Wednesday.

&&

.HYDROLOGY...
A period of heavy rain and possibly thunder is likely along the
Maine coast this evening...transitioning to snow over for areas
just inland in some cases. Given snow in the mountains and
foothills and a rain/snow mix just south...I do not expect
significant river flood issues. May have some short-fused
issues at the coast especially with water levels rising towards
the 1 AM Friday high tide which may prevent efficient drainage.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides are near peak for the month and already near
flood stage without wind and wave forcing. With a strong coastal
storm developing today and winds increasing that will lead to
some areas of minor flooding and additional splashover and beach
erosion. Storm surge values should max out around 2 ft...but
crucially the timing will miss high tide by several hours. Coastal
flood advisory remains in effect for the next two tide cycles.

&&

.EQUIPMENT...
The last GYX upper air observation was March 25 at 12Z.
Unfortunately, a disruption in gas supply has temporarily halted
observations from GYX. At this time it is unknown when
observations will resume.

The Sugarloaf NWR transmitter remains off the air with an
unknown restoration time.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Storm Warning from 2 PM this afternoon to 8 AM EDT
     Friday for MEZ012>014-020>022-033.
     Winter Storm Warning until 2 PM EDT Friday for MEZ007>009.
     Winter Weather Advisory from 2 PM this afternoon to 8 AM EDT
     Friday for MEZ019-025>028.
     Coastal Flood Advisory until 3 AM EDT Friday for MEZ023>028.
     Wind Advisory from 4 PM this afternoon to 11 PM EDT this
     evening for MEZ027-028.
NH...Winter Storm Warning until 2 PM EDT Friday for NHZ001>004.
     Coastal Flood Advisory until 3 AM EDT Friday for NHZ014.
MARINE...Gale Warning from 2 PM this afternoon to 11 AM EDT Friday for
     ANZ150>154.

&&

NEAR TERM...Hanes
SHORT TERM...Legro
LONG TERM...Watson

Hazardous Weather Outlook
National Weather Service Gray ME
1053 AM EDT Thu Apr 9 2020

MEZ012>014-020>022-033-101500-
Southern Oxford-Southern Franklin-Southern Somerset-Androscoggin-
Kennebec-Interior Waldo-Interior Cumberland Highlands-
1053 AM EDT Thu Apr 9 2020

...WINTER STORM WARNING IN EFFECT FROM 2 PM THIS AFTERNOON TO 8 AM
EDT FRIDAY...

This Hazardous Weather Outlook is for south central Maine,
southwest Maine and western 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 Storm Warning.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Storm Warning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

MEZ007>009-NHZ001-002-101500-
Northern Oxford-Northern Franklin-Central Somerset-Northern Coos-
Southern Coos-
1053 AM EDT Thu Apr 9 2020

...WINTER STORM WARNING IN EFFECT UNTIL 2 PM EDT FRIDAY...

This Hazardous Weather Outlook is for west central Maine, western
Maine and northern New Hampshire.

.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 Storm Warning.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Winter Storm Warning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

MEZ019-NHZ003-004-101500-
Central Interior Cumberland-Northern Grafton-Northern Carroll-
1053 AM EDT Thu Apr 9 2020

...WINTER WEATHER ADVISORY IN EFFECT FROM 2 PM THIS AFTERNOON TO
8 AM EDT FRIDAY...

This Hazardous Weather Outlook is for Maine and northern New
Hampshire.

.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...Friday through Wednesday.

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...

Spotter activation is not expected at this time.

MEZ028-101500-
Coastal Waldo-
1053 AM EDT Thu Apr 9 2020

...COASTAL FLOOD ADVISORY IN EFFECT UNTIL 3 AM EDT FRIDAY...
...WINTER WEATHER ADVISORY IN EFFECT FROM 2 PM THIS AFTERNOON TO
8 AM EDT FRIDAY...
...WIND ADVISORY IN EFFECT FROM 4 PM THIS AFTERNOON TO 11 PM EDT
THIS EVENING...

This Hazardous Weather Outlook is for south central 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.

   Coastal Flood Advisory.
   Winter Weather Advisory.
   Wind Advisory.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

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...

Spotter activation is not expected at this time.

MEZ025-026-101500-
Sagadahoc-Lincoln-
1053 AM EDT Thu Apr 9 2020

...COASTAL FLOOD ADVISORY IN EFFECT UNTIL 3 AM EDT FRIDAY...
...WINTER WEATHER ADVISORY IN EFFECT FROM 2 PM THIS AFTERNOON TO
8 AM EDT FRIDAY...

This Hazardous Weather Outlook is for south central 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.

   Coastal Flood Advisory.
   Winter Weather Advisory.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

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...

Spotter activation is not expected at this time.

MEZ027-101500-
Knox-
1053 AM EDT Thu Apr 9 2020

...COASTAL FLOOD ADVISORY IN EFFECT UNTIL 3 AM EDT FRIDAY...
...WINTER WEATHER ADVISORY IN EFFECT FROM 2 PM THIS AFTERNOON TO
8 AM EDT FRIDAY...
...WIND ADVISORY IN EFFECT FROM 4 PM THIS AFTERNOON TO 11 PM EDT
THIS EVENING...

This Hazardous Weather Outlook is for south central 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.

   Coastal Flood Advisory.
   Winter Weather Advisory.
   Wind Advisory.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

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...

Spotter activation is not expected at this time.

MEZ023-024-NHZ014-101500-
Coastal York-Coastal Cumberland-Coastal Rockingham-
1053 AM EDT Thu Apr 9 2020

...COASTAL FLOOD ADVISORY IN EFFECT UNTIL 3 AM EDT FRIDAY...

This Hazardous Weather Outlook is for southwest Maine and southern
New Hampshire.

.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.

   Coastal Flood Advisory.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

ANZ150>154-101500-
Coastal Waters from Stonington, ME to Port Clyde, ME out 25 NM-
Penobscot Bay-
Coastal Waters from Port Clyde, ME to Cape Elizabeth, ME out 25 NM-
Casco Bay-
Coastal Waters from Cape Elizabeth, ME to Merrimack River, MA out
25 NM-
1053 AM EDT Thu Apr 9 2020

...GALE WARNING IN EFFECT FROM 2 PM THIS AFTERNOON TO 11 AM EDT
FRIDAY...

This Hazardous Weather Outlook is for Atlantic coastal waters.

.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.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

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...

Spotter activation is not expected at this time.

MEZ018-NHZ005>013-015-101500-
Interior York-Southern Grafton-Southern Carroll-Sullivan-Merrimack-
Belknap-Strafford-Cheshire-Eastern Hillsborough-Interior Rockingham-
Western And Central Hillsborough-
1053 AM EDT Thu Apr 9 2020

This Hazardous Weather Outlook is for southwest Maine, New
Hampshire, central New Hampshire, northern New Hampshire and
southern New Hampshire.

.DAY ONE...Today and Tonight.

This afternoon and into the early evening, heavy rainfall could
result in ponding of water on roadways.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.