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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KGYX 261526
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1126 AM EDT Sun May 26 2019

.SYNOPSIS...
A cold front will move through the region today with a chance of
thunderstorms, mainly across northern and eastern portions of
the forecast area. A secondary cold front will drop south
through the region on Monday. High pressure will build in from
the west Monday night. A warm front will approach from the
southwest Tuesday night and will move north into the region on
Wednesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
1100 AM Update...
Showers beginning to redevelop across southern Quebec and these
will become more widespread in coverage as they move into the
mountains over the next several hours. 1KM HRRR Intensifies
this activity as it heads southeast through the afternoon with
some thunderstorms forecast for our eastern zones where better
instability is lingering. One inhibiting factor will be the
persistence of stratus over midcoast and central interior Maine
through late morning which has held down heating. So any
stronger convection in doubt at this point but with the strong
shear over the area would still expect gusty winds and perhaps
some small hail in any storms which do develop. Have adjusted
pops/wx grids based on latest radar trends and tweaked area
temps/tds. Will also be dropping SCA`s for the outer waters and
bays. No other changes planned attm.

Prev Disc...
710 AM Update...Didn`t change much with this forecast update.
Just a few minor adjustments to temperatures, PoPs, and winds
for the next few hours. Have seen a couple of thunderstorms
develop west of BTV VT as of 11z. This activity is likely on the
very leading edge of the ascent associated with an approaching
short wave trough. There is also likely some WAA induced by the
advection of the leading edge of the steep lapse rates aloft.
Near-term CAM output haven`t really handled this well thus far.
However, the thinking is that the current activity near BTV will
weaken over the next hour or so and not likely make it to
western NH. However, there is a low prob of this happening so
added slt chance to low chance PoPs in the CT River Valley this
morning.

The development of additional storms (possibly strong)
in the mountains southeastward to the Midcoast southward to
perhaps Cumberland County will be tied to the degree of
surface-based instability that develops due to insolation. The
other factor is short wave trough timing which currently seems
to be a bit faster than previously modeled. This could cross the
area before peak heating and may limit convective coverage. Will
watch this over the course of the AM, but will keep gusty winds
and small hail wording in the forecast for central Maine and
Midcoast zones for this afternoon (mainly between 1 and 4 PM).

Previously...

Plenty of rain and showers present across the forecast area
early this morning, mainly across central and northern zones.
Much of this activity will move offshore by 12z this morning
allowing for at least some partial clearing except perhaps the
Midcoast region of Maine. A prefrontal trough will move from
west to east across much of the forecast area by midday today
allowing for westerly winds and warming temperatures. Highs are
likely to be in the 80s across southern NH, with 70s most
elsewhere.

A short wave trough will approach from the northwest today. The
leading edge of this short wave trough is located near the
southern Quebec/Ontario line as of 07z this morning and is
already associated with thunderstorms as per latest lightning
imagery.

As this short wave trough continues to move toward New
England, convective showers and isolated thunderstorms will
likely develop over northern VT and southernmost Quebec.
Convection-allowing mesoscale models are in good agreement that
upscale growth of the area of showers and thunderstorms will
occur as they move southeastward from northernmost NH and the
western ME mountains, peaking in intensity across central and
Midcoast ME between 1 and 4 pm before moving offshore. This
region will have the best surface convergence, deeper low level
moisture, and best mid and upper level support for thunderstorms.
If ample sunshine can develop across central and Midcoast ME
before storms approach, then one or two storms may become strong
to marginally severe as deep layer shear will be strengthening
in the presence of several hundred J/KG SBCAPE. Remnant
elevated mixed layer will provide for somewhat steeper than
normal mid-level lapse rates which may aid in stronger upward
parcel accelerations. Main threat would be strong gusty winds.

More isolated activity is possible further south to Cumberland
County ME. If a storm or two can develop that far south it
could be strong with strong gusty winds being the main threat.


Can`t rule out an isolated storm or a couple of showers
elsewhere today, but with prefrontal trough expected to have
moved all the way to the coast across southern zones early on,
surface convergence will be unfavorable for development. A dry
or mostly dry day is expected across southern zones as a result.

A cold water beach hazards statement has been issued for
coastal zones.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Fair weather is expected tonight before a secondary cold front
moves into the region Monday afternoon. The air mass will be
quite dry in advance of this front, so only widely scattered
showers are expected at best. The vast majority of the day will
be dry.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
High pressure rolls into the area from the northwest Monday
night. This will bring a clear and calm night with good
radiational cooling conditions. Low level dewpoints in the upper
30s to low 40s suggest that lows will be mostly in the 40s with
some 30s likely in the sheltered valleys. Could even make a run
at the freezing mark in the coldest spots up north, but for now
it looks like a good frost potential in northern valleys.

The Tuesday through Thursday period will see several waves
tracking east through the westerly flow aloft each bringing
another chance of showers as warm, moist air tries to push its
way northward into New England. With an onshore low level flow
expected it may be difficult for this warm air to make much
progress at ground level.

The first wave arrives Tuesday afternoon as high pressure shifts
into the Gulf of Maine and clouds increase from the west.
Temperatures will be a bit cooler than normal with highs only in
the 60s, coolest in the south where clouds will arrive earlier.
There`s still a fair amount of disagreement among the models on
when and where this wave tracks, but there seems to be an
emerging consensus that weak low pressure tracks by to our south
with the frontal zone remaining to our south as well. The best
chance of rain will be in southern areas Tuesday afternoon and
Tuesday night.

Wednesday looks like we will be mostly in between waves, so we
may squeeze out a mostly dry day in the midst of an otherwise
wet period. The warm front aloft may push all the way into
northern Maine, but southerly low level winds will keep cooler
air in place at ground level. Western Maine stays in the 50s
while southern New Hampshire warms into the 60s to perhaps 70
degrees with plenty of clouds.

The next wave tracks quickly eastward along the mid level
frontal zone Wednesday night spreading another round of warm
advection showers through the area. Cannot rule out some rumbles
of thunder as well as the warm/moist advection may generate a
bit of elevated instability.

The third wave will send a cold front through the area late
Thursday or Thursday night. Before it does so, expect the low
level inversion to break and the warmer air will be felt area
wide on Thursday. Expect widespread temperatures in the 70s with
some near 80 in southern areas. Although there are still a lot
of moving pieces still yet to find their place, the warm and
humid air mass should be enough to generate a few thunderstorms
as the cold front arrives. This would be particularly true if it
crosses through the area during the day on Thursday.

High pressure builds in behind the front for Friday finally
bringing a dry day. Temperatures warm into the upper 60s to mid
70s in a northwest flow. The high shifts east on Saturday with a
southerly flow developing and a cold front dropping south out
of Canada.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
Short Term...Cigs and vsbys will improve to VFR this morning
except perhaps the Midcoast of ME where MVFR may last through
late morning. Local MVFR to IFR in sct showers and thunderstorms
from 1-5 pm across central and Midcoast ME. VFR tonight and
Monday. West winds gust around 20 kt today.

Long Term...VFR through Tuesday morning. Expect increasing
clouds and lowering ceilings from southwest to northeast during
the day Tuesday. Showers are likely in southern parts of the
area with IFR conditions possible. Although we may get a break
from the showers on Wednesday MVFR to IFR conditions may persist
especially across western Maine. More rain moves through
Wednesday night. There could be some improvement to VFR at times
on Thursday with a chance of showers and thunderstorms as a cold
front arrives.

&&

.MARINE...
Short Term...SCA conditions this morning will subside this
afternoon. Conditions will remain below SCA thresholds tonight
and Monday. Thunderstorms may move off the Maine Midcoast
(possibly as far south as Cumberland County ME coast) between 1
and 5 PM and may contain gusty surface winds to 35 kt.

Long Term...High pressure builds into the Gulf of Maine Tuesday
and then shifts eastward. A warm front tries to lift north
Tuesday night but will likely stall through Wednesday before
finally shifting north early Thursday. A cold front moves in
from the northwest Thursday night.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
ME...Beach Hazards Statement until 8 PM EDT this evening for
     MEZ023>028.
NH...Beach Hazards Statement until 8 PM EDT this evening for NHZ014.
MARINE...None.
-- End Changed Discussion --

&&

$$