Flash Flood Warning 65, NWS Gray, ME

Area Forecast Discussion
National Weather Service Gray ME
306 PM EDT Tue Jul 25 2023

.SYNOPSIS...
Scattered showers and thunderstorms will be possible again this
evening as an upper level trough moves towards New England.
There will be a brief dry period on Wednesday as high pressure
builds in. It will then become very warm and uncomfortably
humid for much of the remainder of the work week, with a return
of showers and thunderstorms.

&&

.NEAR TERM /THROUGH TONIGHT/...
Water vapor imagery shows a compact short wave over PA/NY that will
trek across the forecast area through this evening. This wave will
continue to trigger thunderstorms through this evening with a few
storms capable of strong winds and isolated instances of flash
flooding. Similar to yesterday, there isn't much of a front for
storms to organize along. This is creating some variance amongst the
12Z CAM suite as to where storms will initiate as well as how strong
storms will become. A broad consensus focuses storms along the
western Maine foothills towards the Maine coastline with a
secondary area of focus across southern New Hampshire into far
SW Maine later this evening.

The convective parameter spaces is currently characterized by 1000
to 1500 J/kg of ML CAPE and 25 to 30 kts of effective shear. This
will be sufficient enough for a few strong updrafts that could lead
to some gusty outflow winds or potentially a strong to severe
downburst if any storms collapse. Modest mid level lapse rates
around 6C/km could also lead to some hail, and there is a non zero
risk for some marginal severe hail.

What is more of a concern is the increase in PWATs to around 1.5
inches and the potential for slow moving storms along a convergence
zone near the Maine foothills and another convergence zone across MA
that could shift into southern NH later this evening. Storms
have already developed over east-central Oxford County in line
with most runs of the HRRR since early this morning. Similar to
yesrday's storm that produced flash flooding, the HRRR suggest
these storms will be slow moving. The 12Z HREF 3-hour max QPF
shows isolated pockets of up to 3-4 inches suggesting this is
the high end of heavy rainfall potential. Looking at the 12Z
HREF 3-hour ensemble mean only tops out around 0.5 inches
indicating the isolated nature of heaviest rainfall. Thus, the
greatest threat appears to be isolated instances of flash
flooding followed by strong winds and possibly some small to
near severe hail stones.

Convection wanes between 8 and 10 PM this evening with clearing
skies overnight. Fog will be likely across areas that do see
rainfall and along sheltered valleys with patchy fog elsewhere.
Lows will range from the upper 50s north to mid 60s south.

&&

.SHORT TERM /WEDNESDAY/...
Fair weather looks to be in store for Wednesday as high pressure
builds in from the southwest. SW flow will allow for temperatures to
climb into the mid to upper 80s, while some onshore wind component
will keep the beaches several degrees cooler than the interior.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
The big picture in the long term will be the potential for an
organized convective/MCS on Thursday with heavy rain/severe
storms accompanied and followed by sultry heat that will
increase into Friday. This will be followed by a welcome cool
down Sunday into next week.

Wednesday night will be quiet across the area in the wake of the
passing ridge. Meanwhile a pair of shortwave troughs and
associated frontal system will be progressing eastward out of
NY. Concern is growing for strong/severe storms and torrential
rainfall with this system. The LLJ around 40-50kt will be
paralleling the warm front as it noses into New England late
Thursday morning. PWATs are projected to surge over 2" with warm
cloud depths >12kft. The trends have favored a track from NY
and into NH/ME by midday Thursday, however a lot of uncertainty
remains with this exact location/track which could have great
impacts on our forecast. For now, have added the pops/clouds
expected with the convection, which will have the effect of
limiting our potential heating for the day. If not for the
convection, temperatures would shoot up into the upper 80s to
low/mid 90s as 850H temps climb to 17-19C. SPC Day 3 outlook has
the southern half of the forecast area in a slight risk, and a
marginal risk elsewhere. The WPC Excessive Rainfall Outlook
(ERO) has the area in a marginally risk for flash flooding.
Confidence in the track could lead to adjustments in these
categories. Something to closely monitor with future forecast
packages.

Showers and thunderstorms could linger Thursday evening, but as
the best jet dynamics weaken and push east with the wave expect
coverage to lessen. It will be a warm and muggy night with
dewpoints in the 70s. This will support a rapid warm up on
Friday, with heat inidices near to just below headline
criteria in southern areas. Some scattered convection is
possible, but not widespread enough to limit heat with cloud
coverage. Once again there will be concerns for heavy rainfall.
Attention then turns to an approaching cold front Friday Night
into Saturday morning, continuing rain chances. Looking at a
notable cool down Sunday

This front will also bring a significant cool down to the
region. While 850H temps +8C-10C. This will translate to high
temperatures in the mid 70s, with the higher terrain areas
possibly seeing highs only in the upper 60s. This cooler weather
will continue into Monday as the upper level trough lingers
over Quebec.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Short Term... Scattered thunderstorms will develop through this
evening and will likely bring periods of restrictions if they
track over a TAF site. KHIE, KLEB, and KRKD look to be the
most likely sites to miss a passing TS while TS cannot be ruled
out at other TAF sites. Valley and coastal fog will likely bring
LIFR conditions to KLEB, KHIE, and KRKD tonight and there is
potential for IFR to LIFR at KAUG. Patchy fog may impact
remaining TAF sites although confidence is lower. VFR prevails
under high pressure Wednesday.

Long Term...The ridge will break down on Wednesday night
allowing a shortwave into New England, which will bring sct to
numerous TSRA to the terminals from west to east. Mainly VFR
conditions expected Friday apart from fog possible.

&&

.MARINE...
Short Term...Thunderstorms that form over the land may track
out into the near shore waters through this evening. SW flow
prevails tonight through Wednesday with winds and seas
remaining below SCA thresholds. High pressure builds into the
waters late tonight into WEdnesday.

Long Term...The Bermuda High builds offshore late
Wednesday through the latter half of the week bringing
predominately S to SW winds around 10 to 15 kt, then
veers to the NW Saturday evening after a cold front pushes
offshore. Seas will be around 2-3 ft.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

SYNOPSIS...Jamison
NEAR TERM...Schroeter
SHORT TERM...Schroeter
LONG TERM...Jamison
AVIATION...Schroeter

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Special Weather Statement
National Weather Service Gray ME
321 PM EDT Tue Jul 25 2023

MEZ020-021-252000-
Androscoggin ME-Kennebec ME-
321 PM EDT Tue Jul 25 2023

...A strong thunderstorm will impact portions of west central
Kennebec and north central Androscoggin Counties through 400 PM
EDT...

At 320 PM EDT, Doppler radar was tracking a strong thunderstorm near
Canton, or 11 miles north of Turner, moving east at 25 mph.

HAZARD...Wind gusts up to 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Jay, Livermore Falls, Leeds, Livermore, Chesterville, Fayette and
Wayne.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4437 7002 4436 7026 4441 7027 4442 7026
      4444 7027 4448 7020 4449 7014 4449 7005
TIME...MOT...LOC 1920Z 258DEG 21KT 4443 7026

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

MSC

Special Weather Statement
National Weather Service Gray ME
400 PM EDT Tue Jul 25 2023

MEZ021-252030-
Kennebec ME-
400 PM EDT Tue Jul 25 2023

...A strong thunderstorm will impact portions of northwestern
Kennebec County through 430 PM EDT...

At 358 PM EDT, Doppler radar was tracking a strong thunderstorm 7
miles east of Livermore Falls, or 15 miles southwest of Oakland,
moving east at 30 mph.

HAZARD...Wind gusts up to 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Waterville, Fairfield, Oakland, Belgrade, Manchester, Chesterville,
Fayette, Sidney, Rome, Mount Vernon, Vassalboro, Vienna, Readfield,
Wayne, Smithfield and Winslow.

This includes Interstate 95 between mile markers 117 and 128.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

If on or near Great Pong and nearby lakes, get out of the water and
move indoors or inside a vehicle. Remember, lightning can strike out
to 10 miles from the parent thunderstorm. If you can hear thunder,
you are close enough to be struck by lightning. Move to safe shelter
now! Do not be caught on the water in a thunderstorm.

&&

LAT...LON 4437 7007 4449 7012 4449 7004 4451 7003
      4453 7007 4454 7006 4461 6983 4458 6982
      4458 6980 4461 6978 4461 6976 4459 6968
      4454 6965 4442 6963
TIME...MOT...LOC 1958Z 256DEG 27KT 4446 7000

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

MSC

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