821
FXUS61 KGYX 060220 AAB
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1020 PM EDT Wed Jun 5 2024

.SYNOPSIS...
A trough approaches from the west Thursday bringing periods of
widespread rainfall which also pose an isolated flood risk.
Unsettled conditions persist through the weekend with daily
chances of showers and an afternoon thunderstorms.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
10PM Update...Showers and isolated storms continue to develop
across Northern NH and the Western Maine mountains as mid-level
instability continues. Increased pops in these areas with this
forecast update a bit to account for current radar trends. Also
increased the patchy fog across the interior. It should mostly
be shallow based low-lying fog development tonight.

7PM Update...Quick update this evening with no significant
changes in the forecast. Overall things are trending as planned
with a few showers and a isolated thunderstorm or two across the
region this evening. Daytime instability will continue to trend
down with limited available CAPE remaining for any strong storms
to redevelop. A few showers can`t be ruled out through midnight
as instability aloft associated with a departing trough. Low
level moisture will be on the increase tonight as southerly flow
increases ahead of the next shortwave. Higher dewpoints and
rainfall today in some areas will lead to fog development after
midnight.

Showers and thunderstorms continue into late afternoon. What
CAPE had built through the morning and afternoon is now awash
amid flattened cells and spreading anvils. So, additional
convection will be limited to areas that did not see heavy rain
up to this point. Current radar has strongest convection from a
KLEB to KPSM line where heavy rain and accumulating small hail
is bring reported towards Dover and Portsmouth.

Elevated instability continues into the evening, so showers
will continue to propagate through the area. The concern here is
ongoing training that could track over areas that saw heavy
downpours during the afternoon and cause minor flooding amid
slow mean winds. These too should be on the downtrend after
midnight.

Fog development is likely for the 2nd half of tonight,
especially for areas that received rainfall today. HREF vis
probabilities also hint at fog and low clouds moving into the
coastal locations tonight which may also be drizzle based on
model soundings.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...
Marginal excessive rainfall threat continues Thursday, but so
too does uncertainty on coverage and intensity.

Forcing will be arriving from the south in at least two
waves...one in the morning and another later in the evening.
These should move south to north during the day. Initial onset
may develop showers with some stronger cores to bring mod to
heavy rainfall rates. These appear more likely in southern NH
(not fully saturated from Wed events) and into the Lakes Region
of ME (some paths of heavy rainfall from Wed). So, the risk for
some excessive runoff will be possible if soils are still damp
from Wed activity, but many areas are still plenty dry from
prior conditions.

How this develops as it tracks over Maine is a bit more
conditional. The low levels will have plenty of moisture, but
mid level RH is more questionable. Tomorrow may end up more of a
soggy and foggy day vs. a complete washout. This may be
translated to rain in the foothills and mountains where low
level flow will be lifted and develop more substantial
reflectivity.

This will continue for much of the day before another round of
forcing arrives from the SW to NH. After built daytime heating,
a few rumbles of thunder will be possible which could again have
enhanced rainfall rates. Fog will again be likely Thursday night
as damp air mass remains over the area.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Overview: The 500 mb pattern continues to show a ridge blocking
the upper low over the Great Lakes through the weekend. The
block looks to break heading into next week, allowing the closed
low to move out of the region, however the pattern converts to
a parade of deep troughs swinging across the CONUS that will
continue our wetter stretch of weather.

Impacts:
*  No significant weather impacts expected

Details: Surface low pressure continues to slowly move over the
area Friday. Therefore we likely still have a frontal boundary
draped over the area. This front would continue to provide
enough forcing to keep a chance of showers across the area,
however it will be low with the loss of upper level forcing. The
higher chances look to be in the mountains as upper level
forcing remains closer there. With daytime heating and upper
level forcing inching closer shower chances will increase for
the entire area with lower chances remaining along the coastal
plain as onshore flow advects more stable air inland. These
would be isolated to scattered convectively driven showers.
Otherwise, Friday will be pleasant with high temperatures in the
70s. In the eastern parts of our CWA highs may only reach the
upper 60s as lingering thicker clouds hinder efficient heating.
Low temperatures look to bottom out in the 50s across the area.

Surface low pressure continues to meander overhead Saturday as
a shortwave 500 mb trough also swings through. Would expect this
to be a wetter day with the added upper level forcing, but
again with not a great amount of synoptic forcing, would expect
storm mode to continue to be scattered, just more widespread,
convectively driven showers and maybe a thunderstorm. Highs and
lows will be similar to Friday, albeit a couple degrees cooler
as 850 temperatures are on a slight downward trend. The upper
low looks to be directly overhead on Sunday so, similar to
Saturday, there will be enough forcing for scattered showers and
a thunderstorm or two to develop in the afternoon.

The upper low departs overnight Sunday, but a well defined
trough will be hot on its heels for Monday. Depending on the
location of a cold front modeled to be in the area, showers
could be a lot more scattered to isolated on Monday, but with
the vorticity maxima rounding that trough being right overhead
we will have to watch trends in this time period closely as
changes in positions of frontal boundaries could make things
more interesting. The 500 mb pattern looks to become more zonal
for Tuesday, but again if we have a cold front near by as some
models suggest, scattered showers and an afternoon thunderstorm
or two remain in the table. As expected global models begin to
diverge greatly on timing of troughs going forward so for
Wednesday and beyond we will have to just continue to watch
trends. For now will be leaving in chances of showers as that
seems reasonable.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Short Term...After SHRA and some TS this afternoon, lowered
ceilings advance northward later tonight with some patchy fog
in the interior and areas of fog along coastal terminals.
Ceilings should fall to IFR, with some LIFR vis possible. These
lowered conditions are expected to continue for much of the day
Thursday but HIE which could just have these in vicinity. Rounds
of SHRA possible through Thursday, with more fog expected
Thursday night.

Long Term...Outside of scattered showers and an isolated
thunderstorm, or two, ceilings will be mainly VFR through
Monday. Winds also remain on the lighter side 5-10 kts with
gusts of 10- 15 kts.

&&

.MARINE...
Short Term...Below SCA conditions. Expect marine fog and stratus
to be developing over the next 12 to 24 hours that will reduce
visibility. This may linger through much of Thursday and
Thursday night.

Long Term...Conditions hazardous to small craft are not
expected through Monday. Seas will generally be 3-4 ft with
winds 10-15 kts with gusts to 20kts. Winds will be shifting
southwesterly on Saturday.

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...Dumont
SHORT TERM...Cornwell
LONG TERM...Baron
AVIATION...
MARINE...