Biddeford, Maine 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

581
FXUS61 KGYX 212306
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
606 PM EST Thu Nov 21 2024

.SYNOPSIS...
Low pressure will track north tonight, bringing rain to the
area overnight. The broad system will be slow to exit, with
chances for precipitation continuing through Saturday.
Conditions will start to dry out Sunday into Monday as the low
pressure lifts into the Canadian Maritimes.

&&

.NEAR TERM /THROUGH FRIDAY/...
600 PM Update... Made some minor adjustments to PoPs based on
latest radar trends and sfc observations. This generally delayed
them some over much of western ME where weak forcing for ascent
is still present but did introduce drizzle to the forecast based
on observations. Otherwise, the inherited forecast remains
largely unchanged at this time.

Previously...
Surface circulation continues to organize south of Long Island
this afternoon as cyclogenesis takes place. This area of low
pressure will give the final nudge north for rain that has
mainly been focused in SW NH today. Showers begin, then become
more steady overnight as this low wraps inland over central New
England.

Accompanying this low will be a brief but potent low level jet
developing off the NH/southern ME coast overnight. Daytime
deterministic solutions have this as a 40-60kt jet through
925/850mb, thus have increase surface gusts for much of tonight.
HREF min gusts do push 30-40 mph along the immediate coast and
southern NH tonight. Another zone of enhanced winds may be the
downslope locations NW of the Whites and western ME mountains
where gusts to 40 mph can`t be ruled out for a 4 or 5 hour
window after midnight.

As these winds move north through the area overnight, so too
will more steady rainfall. Rain rates will be heaviest after
midnight for the southern CWA, and after daybreak for western ME
and the Midcoast. No flooding is expected with very dry
antecedent conditions.

&&

.SHORT TERM /FRIDAY NIGHT/...
A dry slot moves northward through NH and southern ME Friday
morning and early afternoon. This should offer a quick shutoff
of both precipitation and the aforementioned gusts from
overnight, but only up to the Kennebec Valley/western ME
mountains.

There was still a lot of discrepancy between guidance solutions
heading into Friday night. This revolves around how resilient
the dry slot will be as well as general progression of the low
consolidation to the west. Additional onshore flow from the SE
will advect moisture in later Fri afternoon to begin another
period of stratiform precipitation across the area overnight.

Rain is expected for the lowlands, but snow will feature more
widely at greater elevations in the Whites, western ME
mountains, and western NH Greenway, especially overnight. In
general, accumulating snow may be hard to come by outside of the
elevated Whites, but flakes will be about.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Broad upper low will be centered near Cape Cod Saturday
morning, and waves of energy rotating to the north and west over
the area will prolong cloudy and rainy conditions for at least
the morning hours with snow toward the north and higher
elevations (although a few flakes may mix in early farther to
the south). The upper low will gradually move off to the
northeast through the day and into Saturday night, and there`s
still come uncertainty among the models on how quickly this
occurs, but the general trend will be decreasing precip chances
south of the mountains going into the afternoon and evening,
although could be more Saturday night per the ECMWF. A surface
low will also be deepening as it lifts northward into Nova
Scotia, and with the tightening gradient expected breezy
conditions to develop by the afternoon with gusts of 20 to 30
mph possible.

Once precip tapers off, skies are expected to remain partly-
mostly cloudy south of the mountains through Saturday night
while the mountains stay cloudy with scattered upslope snow
showers.

Stacked low pressure will remain near the Canadian Maritimes on
Sunday leaving northern New England in a northwest flow, which
will be on the breezy side with a tight pressure gradient. Based
on latest forecast soundings, we`re looking like upwards of
25-30mph. Rain and snow showers will likely continue across the
north and mountains, and a few of these may occur downwind of
the mountains if we can get enough daytime instability and
Froude numbers are high enough (the NAM is more supportive of
this) as there will be an upper trough nearby.

The upslope precip in the mountains will wind down either
Sunday night or early Monday as high pressure briefly builds
into the region bringing a dry day with seasonable temperatures
mainly in the 40s. As quickly as the high moves in, it will
quickly give way to an upper trough and surface low moving
across the Great Lakes that bringS the next shot at widespread
precipitation Monday night and into Tuesday. Temperature profiles
may be cold enough to support some snow or even a mix Monday
night or Tuesday morning, but confidence is low and would probably
be across northern areas if anywhere.

After this system passes, there is a good support among the GFS
and ECWMF ensembles members with dry conditions on Wednesday
(other than mountain upslope snow showers). Going into next
Thursday/Thanksgiving, the operational GFS is hinting at low
pressure potentially bringing some snow to the area, but this is
the faster solution with many of its ensemble members (as well
as the ECWMF) keeping conditions mostly dry. The NBM PoPs of
slight chance across southern areas capture this well.

Lastly, there is pretty high confidence in a cooler airmass
arriving toward the end of next week, and even though this is
just beyond the extended forecast, there is a signal for what
could be the first measurable snowfall of the season for many
areas. This would potentially be in the day 8 or 9 time period,
and as always this far out, details (such as amounts and timing)
are uncertain.

&&

.AVIATION /23Z THURSDAY THROUGH TUESDAY/...
Short Term...MVFR and IFR cigs are expected overnight tonight
along with increasing east winds and RA. Winds may gust 20 to 30
kts tonight as low pressure drifts into central New England.
Winds slacken Friday morning as well as some improvement in
restrictions with IFR becoming MVFR and perhaps VFR later in the
afternoon. Another round of lowered ceilings arrives Friday
night with RA. More in the way of SN may be possible along the
western ME mountains and the Whites Friday night.

Long Term...Rain along with IFR to MVFR ceilings expected at
most TAF sites on Saturday, but conditions look to improve to
VFR late in the day into Saturday night with the exception of
HIE and LEB, where MVFR ceilings and possibly rain and snow
showers continue through Sunday or even Sunday night. .
Elsewhere, mostly VFR expected Sunday and Monday with northwest
wind gusts 25-30 kt possible on Sunday. A few rain or snow
showers may also develop Sunday afternoon. Another low pressure
system looks to bring increasing precipitation chances Monday
night and Tuesday along with flight restrictions.

&&

.MARINE...
Short Term...A period of Gales as well as increased wave
heights is expected tonight. Low pressure strengthening south of
Long Island will track north, with a strong jet moving along
the coastal waters tonight. A window of 35 to 40 kt gusts will
be possible overnight, before subsiding Friday morning. However,
this will be part of a broadening area of low pressure across
the Northeast. Another round of increased winds and building
waves is likely into Friday night.

Long Term...SCA conditions expected on Saturday as low pressure
lifts northward toward Nova Scotia but remaining mostly east of
the waters. With more of an eastward forecast, the potential
for Gales during the day Saturday has lowered but will still be
possible Saturday night and Sunday as offshore flow increases
with a tightening gradient. Conditions may be able to fall below
SCA levels late Monday or Monday night as high pressure briefly
builds in before winds increase ahead of and also behind a low
pressure and front that look to cross around Tuesday. Another
area of low pressure may approach the waters toward the end of
next week, but confidence is low on timing and potential track
of the low.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Gale Warning until 6 AM EST Friday for ANZ150-152>154.
     Small Craft Advisory until 6 AM EST Friday for ANZ151.

&&

$$

NEAR TERM...Tubbs
SHORT TERM...Cornwell
LONG TERM...Combs