Severe Thunderstorm Warning 18, NWS Gray, ME

Area Forecast Discussion
National Weather Service Gray ME
925 AM EDT Sat Jun 6 2020

.SYNOPSIS...
A warm and humid southerly breeze will be replaced by a cooler
and less humid northwest wind by tonight behind a cold front.
Showers and storms are expected to fire ahead of the front with
gusty winds and small hail possible. A mix of clouds and
sunshine with widely scattered showers on Sunday as an upper
trough crosses the area. High pressure builds east into the
region through the first half of the new work week along with a
gradual warming trend. Precipitation chances return during the
second half of the week.

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...

925 AM...At 13z a 1006 millibar low was vicinity of Penobscot
bay with a wavy frontal boundary extending through southern
Maine and central New Hampshire to a 1006 millibar low vicinity
of the Vermont-Quebec border. The trailing cold front extended
through eastern New York with a prefrontal trough through
western New England. For today...modified soundings show CAPES
at or above 1500 j/kg today over much of New Hampshire and
southwest Maine ahead of the cold front. Expect convection to
increase in coverage next several hours as heating and
strengthening wind field ahead of shortwave impulse and
approaching surface front. The biggest threat today will
continue to be a few cells capable of producing damaging wind
gusts. In the vicinity of the warm frontal boundary that
stretches from central New Hampshire through southwest
Maine...there may be sufficient shear for an isolated spin up.
For this ESTF update...adjustments of near term grids to reflect
the mesonet as well as radar and satellite trends.

Prev disc...
700 AM Update... Made a few minor tweaks to temperatures and dew
points through according to latest observations and model
trends. At this hour, an area of moderate rainfall is moving
across Maine. It had contained thunder but that has since
decreased. Attention turns to upstream development along the
cold front; as of this hour RAP13 analysis places the cold
front along a line extending from the low pressure center south
of Montreal southwestward through New York to near Pittsburg PA.

Previously...
Today, showers and storms are expected with a crossing frontal
system and forcing shortwave trough. The compact shortwave digs
down from Ontario through the Great Lakes region and into New
England today, meanwhile the surface low skirts across the
southern Canadian border, strengthening as it crosses into Maine
by mid-day. The first order of business is a prefrontal wave
and associated shower/elevated convection activity which will
track into northern NH around dawn, into western Maine by about
12Z with a weakening trend. The main show will be the crossing
cold front. High dew points well into the 60s plus increasing
shear and steepening lapse rates with the shortwave trough will
create a favorable environment for thunderstorms today as the
cold front crosses.

As temperatures climb with the diurnal trend today, into the 70s and
80s over the coastal plain (limited along the Mid-Coast with a cool
marine layer near the surface), instability grows to around 1500-
2000 MUCAPE/1000-1500 MLCAPE...caveats here are that convection from
this morning may work over the atmosphere to a certain degree over
the north and the marine layer over the MidCoast will take more
forcing to overcome. Nonetheless, hires models suggest the cold
front provides enough forcing to produce a line or two of
organized storms this afternoon. The greatest chances for
damaging wind gusts and hail exists over the lowlands and
foothills, where the crossing cold front has more CAPE to work
with during the day today. This aligns well with a marginal risk
outlined by the Storm Prediction Center. Behind the cold front,
a northwest breeze occasionally gust to around 20-25 kts takes
over with steep low-level lapse rates keeping shower chances
going until sundown.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Long after the cold front exits to the east over the waters,
the main trough axis aloft swings through tonight with an uptick
in light rain showers, mainly over the mountains. Temperatures
will steadily cool into the 50s and 40s, a few degrees below
normal for this time of year. Northwest flow continues into
Sunday as the trough pulls away with clouds lingering in the
mountains keeping temperatures cooler. Highs will be in the 60s
north to 70s south, with the NW flow keeping the seabreeze at
bay. Light, scattered to isolated showers taper down through the
day with dry air pouring in from the north.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
We begin this forecast cycle with an upper level pattern of a
trough over the northeast and northwest CONUS with a strong
ridge built between over the Great Lakes. Undercutting that
ridge is tropical storm Cristobal.

Sunday will bring NWly flow, with some clouds lingering in the
mountains keeping temperatures cooler. Highs will be in the 60s
north to 70s south, with the NW flow keeping the seabreeze at
bay.

High pressure builds in for the start of next week. As it does we'll
see increasing temperatures through the week. Initially offshore
flow will keep the seabreeze confined to the coast, thus have
increased temps on Monday slightly.

While the high builds into our region, well to our west
tropical storm Cristobal is moving up the west edge of the
ridge, bringing moisture to join with the northern stream short
wave over Ontario. Some of this moisture looks to make it over
the top of the ridge in at least the form of increasing clouds
for our area on Tuesday. Still a large spread from ensembles
with only around 40% producing any precipitation Tuesday night,
still will put a slight chance in the mountains for Tuesday
night where it's most likely to see any precip.

Wednesday when the high shifts to the east, we'll see a
stronger seabreeze develop, thus have lowered coastal
temperatures a bit for this period.

For the end of the week the extra tropical low which absorbed
the remnants of Cristobal will move across southern Canada,
dragging a cold front and showers across our region. The trend
has been slower with this system, which is consistent with the
fact that the initial flow is highly blocked. While the end of
the week will likely see some showers, the timing is still very
uncertain and have stuck close to the consensus for this update.

&&

.AVIATION /13Z SATURDAY THROUGH WEDNESDAY/...
Short Term...Light SSWerly winds this morning bring humid conditions
with patchy fog and low ceilings leading to localized MVFR to
IFR restrictions to some portions of the area. Along the coast,
low ceilings and more dense fog is likely to impact RKD (LIFR),
and to a lesser extent PSM/PWM. Restrictions lift after sunrise.
A cold front and associated SHRA and TSRA activity crosses today
with localized IFR possible. Storms approach the Connecticut
River by around dawn, then re-fire along the front with
temporary restrictions during the afternoon, most likely for
Maine terminals. VFR returns behind the front with northwesterly
flow, except for over HIE where MVFR ceilings may linger into
Sunday.

Long Term... After the cold front moves through we'll see NWly
flow through the day on Sunday. High pressure moves in for the
first half of next week with VFR continuing. While there may be
some clouds on Tuesday, still expect VFR through the middle of
the week.

&&

.MARINE...
Short Term...Southerly winds this morning ahead of a cold front
push seas to near 5 ft with SCA conditions most likely over the
Mid-Coast of Maine. Winds stay below 25 kts into the afternoon,
except locally in storms this afternoon as the cold front
crosses. Offshore winds take over after the front this evening
and overnight with winds gusts approaching 25 kts.

Long Term...NWly flow behind the cold front my approach SCA in
the eastern zones before beginning to subside on Sunday. High
pressure builds across the waters through the first half of next
week.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Beach Hazards Statement until 8 PM EDT this evening for MEZ023-
     024.
NH...Beach Hazards Statement until 8 PM EDT this evening for NHZ014.
MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ150.

&&

ES

Hazardous Weather Outlook
National Weather Service Gray ME
1229 PM EDT Sat Jun 6 2020

MEZ023-024-NHZ014-071630-
Coastal York-Coastal Cumberland-Coastal Rockingham-
1229 PM EDT Sat Jun 6 2020

...BEACH HAZARDS STATEMENT IN EFFECT UNTIL 8 PM EDT THIS EVENING...
...SEVERE THUNDERSTORM WATCH 261 IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

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

.DAY ONE...This Afternoon and Tonight.

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

   Beach Hazards Statement.
   Severe Thunderstorm Watch.

Scattered thunderstorms this afternoon will produce strong damaging
winds and hail.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

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.

MEZ012-018>021-025>027-033-NHZ006-008>013-015-071630-
Southern Oxford-Interior York-Central Interior Cumberland-
Androscoggin-Kennebec-Sagadahoc-Lincoln-Knox-
Interior Cumberland Highlands-Southern Carroll-Merrimack-Belknap-
Strafford-Cheshire-Eastern Hillsborough-Interior Rockingham-
Western And Central Hillsborough-
1229 PM EDT Sat Jun 6 2020

...SEVERE THUNDERSTORM WATCH 261 IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

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

.DAY ONE...This Afternoon and Tonight.

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

   Severe Thunderstorm Watch.

Scattered thunderstorms this afternoon will produce strong damaging
winds and hail.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

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.

MEZ013-014-022-028-071630-
Southern Franklin-Southern Somerset-Interior Waldo-Coastal Waldo-
1229 PM EDT Sat Jun 6 2020

This Hazardous Weather Outlook is for south central Maine and
western Maine.

.DAY ONE...This Afternoon and Tonight.

Scattered thunderstorms this afternoon will produce gusty winds and
small hail.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

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.

MEZ007-NHZ001>005-007-071630-
Northern Oxford-Northern Coos-Southern Coos-Northern Grafton-
Northern Carroll-Southern Grafton-Sullivan-
1229 PM EDT Sat Jun 6 2020

...SEVERE THUNDERSTORM WATCH 261 IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

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

.DAY ONE...This Afternoon and Tonight.

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

   Severe Thunderstorm Watch.

Scattered thunderstorms this afternoon will produce strong damaging
winds and hail.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

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.

MEZ008-009-071630-
Northern Franklin-Central Somerset-
1229 PM EDT Sat Jun 6 2020

This Hazardous Weather Outlook is for west central Maine and
western Maine.

.DAY ONE...This Afternoon and Tonight.

Scattered thunderstorms this afternoon will produce gusty winds and
small hail.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

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.

ANZ150>154-071630-
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-
1229 PM EDT Sat Jun 6 2020

...SEVERE THUNDERSTORM WATCH 261 IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

This Hazardous Weather Outlook is for Atlantic coastal waters.

.DAY ONE...This Afternoon and Tonight.

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

   Severe Thunderstorm Watch.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

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.

ES

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