944
FXUS61 KGYX 111906
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
306 PM EDT Thu Jul 11 2024

.SYNOPSIS...
Hot and humid conditions linger this evening as a slow moving
cold front stalls near the coastline by tonight. Scattered
showers and a few thunderstorms are possible again Friday as the
front lingers near the region. A few more scattered showers and
storms are expected late Friday night into Saturday mainly over
southern sections with continued hazy, very warm and humid
conditions. Drier conditions can be expected Sunday with a weak
area of high pressure cresting over the region.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Very warm and humid questions will continue this evening with
Heat Advisories remaining in effect for some southern portions
of the forecast area until 00Z. This heat and humid, as well as
and old and weak frontal boundary over the region will keep the
instability over the region with scattered showers and
thunderstorms mainly being the focus over northern areas. This
convection will begin to fade after sunset.

Plenty of low level moisture remains across the region. Patchy
fog will form especially over the interior valleys and along and
near the coastal waters. Temperatures will slowly drop into the
upper 60s to lower 70s for overnight lows again as our
persistent warmth continues.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
The weak frontal system will finally drop south of our region on
Friday. This will do two things. First, the chance for
precipitation, in this case the coverage for any showers or
thunderstorms will be minimal across the region. Second, dew
points will shift downwards slightly, but alas it will remain
very warm and humid.

Apparent temperatures will be slightly lower on Friday than
Thursday. However, heat indices will still reach the lower 90s
in many areas and even mid 90s in a could locations. Therefore,
the conditions will still be borderline near Heat Advisory
levels despite a slight lowering in surface dew points.

Models have been hinting at a weak subtropical wave moving up
the Eastern Seaboard Friday night along and near an axis of high
PWATs over southern portions of our forecast area. The system
interacts somewhat with an approaching trough aloft and the old,
previously mentioned frontal system located over central
portions of New England. This shifts the highest pops to the
southern third of our forecast area which will be a different
trend than the last conditions from this past workweek. Have
gone above most guidance in terms of pops for late Friday night
which blends well as we lead into the long range portion of the
forecast.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...

High Impact Weather Potential: Locally heavy rainfall potential for
southern NH/ME on Saturday.  Beyond this...confidence is too low to
determine a particular day for a high impact weather threat.
However...a strong cold frontal passage is possible by
Wednesday/Thursday which would likely be the next potential for more
than isolated convection/heavy rainfall.  Heat will continue
throughout the period with the greatest potential for advisory level
heat indices being Monday/Tuesday over southern NH and far SW ME.

--Pattern and Summary--

Impressive 600 dam H5 ridge centered over the northwest Atlantic
which has been a driver for the extended period of heat /some spots
now reaching one week of days with highs at or above 90F/.  A
shortwave moves across the region to open the period Saturday...
flattening the ridge somewhat.  Next week...a longwave trough will
make it/s way across central NOAM...eventually arriving in our area
by the end of the week.  The flow ahead of this feature will allow a
continuation of hot/humid conditions as the flow turns WSW. The
trough pushes slowly towards the region by the end of the forecast
period...which should usher in drier/cooler conditions by the end of
next week.  There are differences between the various global
deterministic/ensemble solutions at this range particularly on the
timing of this feature. In terms of impactful weather...a coastal
wave combined with the northern stream shortwave mentioned above
will bring precipitation chances to open the period Saturday...with
additional precipitation likely by the middle/latter portions of
next week ahead of the arriving trough.

--Daily Details--

Saturday: A unique scenario to open the period as well advertised
oceanic upper low brushes by the area as shortwave in the northern
stream flow moves just north of the region.  2" PWAT airmass will be
available for these two waves to work with and there are substantial
probabilities for at least some precipitation south of the mountains
and will follow NBM consensus blend which includes likely PoPs.
Heavy rainfall potential is there given the deep moisture as well as
unidirectional wind profiles with both shortwaves moving generally
parallel to the orientation of any bands of showers.  Certainly
worth watching this period for excessive rainfall potential.

Sunday - Tuesday: Back to the hot temperatures for Sunday through
Tuesday humidity first decreasing some on Sunday...then returning to
the area on Monday/Tuesday. Sunday should be storm-free with weak
shortwave ridging...but shower/storm chances return for Monday and
Tuesday as weak waves in the westerly flow aloft move through the
region. With temps aloft and boundary layer moisture building...
heat headlines look likely for Monday and Tuesday...especially
for southeast NH and far southwest ME.

Wednesday - Thursday:  A more substantial cold front crosses the
region to end the long term forecast period with differences in
timing requiring chance PoPs for both days.  Depending on this
timing...may need heat headlines again on Wednesday...with robust
flow aloft suggesting a severe threat if we align the timing of the
frontal passage with daytime heating.  In all likelihood...
temperatures will cool by Thursday dropping close to seasonal norms
/70s north...80s south/.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Short Term...Areas of low clouds and patchy fog develop tonight
across the region once again tonight, leading to areas of IFR
and LIFR conditions. Lowered conditions expected this evening in
any precipitation over northern areas.

Isolated showers and storms expected on Friday with only a few
pockets of IFR conditions. More patchy fog and lowered ceilings
expected Friday night. Showers may move into southern areas late
making for more widespread LIFR and IFR conditions.

Long Term...A period of rainfall with embedded thunderstorms is
possible Saturday...especially for southern NH and coastal ME
with restrictions likely in low clouds/fog. VFR conditions
return for Sunday. Shower/storm chances increase for Monday-
Tuesday afternoons with will likely bring scattered
restrictions as well as overnight valley haze/fog development.

&&

.MARINE...
Short Term...A persistent southerly flow will continue over the
region. Continued wind gusts to 25 kt and building seas will
allow for SCA conditions over the outer waters to continue
through Friday night across the region. Patchy fog may be
persistent, especially at night over the waters.

Long Term...Winds and waves are expected to remain below SCA
thresholds in the Saturday-Tuesday period. Low level moisture
may allow for the development of fog on Saturday...and again
Monday-Tuesday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Heat Advisory until 8 PM EDT this evening for MEZ018.
NH...Heat Advisory until 8 PM EDT this evening for NHZ010-012>014.
MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ150-152-
     154.

&&

$$
NEAR/SHORT TERM...Cannon
LONG TERM...Arnott