Flash Flooding in Maine, September 26, 2021

Area Forecast Discussion
National Weather Service Caribou ME
1039 AM EDT Sun Sep 26 2021

.SYNOPSIS...
Low pressure will move across the area this morning and exit
into the Maritimes later this afternoon. A cold front will
cross the region Monday evening then exit across the Gulf of
Maine Monday night and Tuesday. A cold upper level low will
remain across the region Wednesday into Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
1037 AM Update... Latest radar reflectivity imagery shows
locally heavy rainfall moving north across the forecast area at
this hour. The first area was crossing the Greater Bangor
region. The second area of heavy rain was lifting north across
Aroostook county. The rain will begin to taper off from
Southwest to Northeast across the region this afternoon. The
rain should end in the Bangor region around midday and late this
afternoon across the far north.

Other than some minor adjustments to hourly temps and dew
points, no other changes needed at time.

previous discussion
Strong left front upper jet axis upper lvl dvrg and 850-700mb
frontogenetical forcing will combine with a surge of llvl moist
sub-tropical air ahead of an apchg mid lvl s/wv to result in
cont'd banding of hvy rn with embedded MBEs that will result in
intermittent rnfl rates of 1 to 2 inches per hour and ocnl
rumbles of thunder. The best rn banding will initially set up
ovr W Cntrl ptns of the FA from about Dixmont to Fort Kent and
remain quasi-stationary for a few hrs, then the band will pivot
ENE msly ovr NE and E Cntrl ptns of the FA this aftn and then
exit via Nrn NB prov this eve. Will be monitoring for the
potential of flooding, at least in the flood adv category, but
cannot rule out lclzd flash flooding if hvy cnvctv elements
within the band keep training ovr the same lctn(s).

Following the passage of the s/wv across the area by erly eve,
skies will msly clr across the FA ovrngt from WSW to ENE with
enough advcn of llvl drier air and blyr wind flow to prevent fog
formation.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Monday starts off with sunshine behind the frontal system. This
will produce mixing to a sufficient depth to generate the
warmest day of the upcoming week. Readings will reach the mid to
upper 60s. The deep mixing will also produce southwesterly wind
gusts up to 25 mph by afternoon. A shortwave and associated cold
front approaches late in the day and will cross the area Monday
night. Rainfall amounts will be modest with less than a tenth of
an inch expected. There's modest instabilty to 700mb and little
moisture above. The front will tend to fall apart as it moves
south later in the night with little precip in the southern half
of the forecast area. The front will introduce the coldest air
of the season for Tuesday and have continued the trend of
nudging down highs based on forecast 850mb temps dropping
towards 0C or less. MOS and bias-corrected guidance continues to
look very optimistic. The next challenge will be lows for
Tuesday night. With the cold airmass in place, there's potential
for frost across the much of the area. High pressure ridging
into the area presents some promise of clearing and light winds.
There's potential for readings in the 20s if the clearing
develops. The existence of 925/850 moisture and a NWerly flow
casts some doubt on the clearing and have taken a conservative
approach with lows in the 30s to lower 40s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
A blocking cold upper low will be the story for the long term
with no significant precipitation and cooler than normal
temperatures. Once again, have continued the trend of lowering
highs through the period as MOS and BC guidance won't catch on
to this major seasonal shift for awhile. Am leaning on raw model
guidance and 925/850mb temps. On Wednesday, it appears the cold
upper low will descend southward over the area with more clouds
and a few sprinkles. The question for Wednesday night into
Thursday will be how much deeper moisture backs into the area
from the east and how far westward it reaches. This moisture
would be from a strong low in the Canadian Maritimes. Thursday
will feature the highest PoPs of the upcoming week...with a
possibility of steadier light precip. A moist/cloudy north to
northeast flow combined with the cold air air mass will
certainly ensure the briskest day of the season to date and
can't rule out highs in the 40s. On the other hand, the frost
risk may be reduced Wednesday and Thursday nights...even with a
lot of low temp readings in the upper 30s. PoPs decrease
Thursday night into Friday as the upper low moves away and temps
will slowly increase Friday into Saturday. Stratocu may be
persistent Friday and Saturday with some warming aloft, NW flow
and residual low level moisture.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
NEAR TERM: Tdy...all TAF sites IFR/LIFR clgs/vsbys in rn hvy
attms, with Downeast sites improving to MVFR clgs in sct shwrs
by the mid to late aftn. Lgt sfc winds with LLWS possible til
late morn.

Tngt...Nrn TAF sites improving to MVFR clgs in sct shwrs by
erly eve, then VFR ovrngt while Downeast sites remain VFR from
the start. Lgt sfc winds.

SHORT TERM: Monday...VFR with gusty SW winds up to 20kt.

Monday night...MVFR tempo IFR cigs possible with a cold front
moving south across the area. Highest probability of reduced
cigs will be north of GNR and HUL.

Tuesday into Wednesday night...Predominately VFR outside of a
chance of MVFR cigs north of GNR and HUL.

Thursday...Risk of widespread MVFR cigs.

&&

.MARINE...
NEAR TERM: No chgs to current SCA for outer waters due to seas.
Kept close to blended model wv guidance for fcst wv hts with wvs
composed msly of a semi-swell spectral group of 7 to 9 sec
propagating from the SSE.

SHORT TERM: An SCA is possible late Monday into Monday night
with wind gusts approaching 25 kt. An SCA is more likely towards
Wednesday night into Thursday. This will be the first time this
season when the air moving over the waters will be cooler than
water temps...and allow mixing of stronger winds aloft to the
surface.

&&

.HYDROLOGY...
After Friday night's widespread rainfall of one to two inches,
more rain is expected today. Additional rainfall amounts of one
two inches are expected today. No flooding is expected on
mainstem rivers per RFC guidance. However, the additional
rainfall will likley result in some localized ponding of water
on roads and some rises on smaller streams and rivers.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory until 5 PM EDT this afternoon for ANZ050-
     051.

&&

Near Term...TWD/VJN
Short Term...MCW
Long Term...MCW
Aviation...TWD/VJN/MCW
Marine...TWD/VJN/MCW
Hydrology...

Hazardous Weather Outlook...CORRECTED
National Weather Service Caribou ME
410 AM EDT Sun Sep 26 2021

MEZ001>006-010-011-015>017-029>032-271000-
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-
410 AM EDT Sun Sep 26 2021

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...Today and tonight.

Locally heavy rainfall today will likely cause significant rises on
area streams and creeks, and ponding of water on roads. River
flooding is not expected.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

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

ANZ050>052-271000-
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-
410 AM EDT Sun Sep 26 2021

This Hazardous Weather Outlook is for Atlantic Coastal Waters.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

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

VJN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CARIBOU ME
1021 AM EDT SUN SEP 26 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1010 AM     FLOOD            NEWPORT                 44.84N 69.27W
09/26/2021                   PENOBSCOT          ME   LAW ENFORCEMENT

            LAW ENFORCEMENT REPORTS THAT THE COUNTY
            WOODS ROAD IS STARTING TO EXPERIENCE
            FLOODING.

&&

TWD

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CARIBOU ME
1022 AM EDT SUN SEP 26 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1010 AM     FLOOD            HAMPDEN                 44.75N 68.84W
09/26/2021                   PENOBSCOT          ME   LAW ENFORCEMENT

            LAW ENFORCEMENT REPORTS THAT MAINE ROAD
            SOUTH IS STARTING TO EXPERIENCE FLOODING.

&&

TWD