Windham, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

301
FXUS61 KGYX 221138
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
638 AM EST Sun Dec 22 2024

.SYNOPSIS...
An Arctic airmass will persist through today with well below
average temperatures and potentially dangerous windchills. After
a dry Monday, light snow arrives Monday night into early
Tuesday with a passing clipper system. High pressure will then
build over the region Wednesday through the end of the week with
a gradual moderating trend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
630 AM Update... Minor changes to reflect latest observational
trends.

Previously...
430 AM Update... Surface observations across northwestern ME
continue to show windchill values between 20-25 below zero and
therefore went ahead and issued a cold weather advisory for
these areas, which will run through 10 AM.

Previously...
Nighttime microphysics satellite imagery early this Sunday
morning shows mainly clear skies south of the mountains with
strato-cu lingering upwind of the mountains themselves. Webcams
indicate that a few light flurries are falling over the higher
terrain and towards the Canadian border but otherwise dry and
blustery conditions prevail. Current temperatures range from the
single digits either side of zero north with teens south but
northwesterly winds of up to 25 mph or so is resulting in
windchills of around 20 below across the north to 5-10 below
zero south. These potentially dangerous windchills will persist
through at least early this afternoon.

Surface high pressure will build over the eastern Great Lakes
region today with our region nestled between this high and the
departing low pressure over Newfoundland. This will result in a
lingering PGF with gusty northwesterly winds prevailing
(although likely not quite as strong as Saturday). Temperatures
will remain well below average with H8 temperatures around
-17C, which despite ample sunshine will limit highs to the
 single digits across the north with teens elsewhere. The
 current forecast high for Portland is 19 degrees, which would
 be in the top 10 lowest maximum temperatures for this date
 (period of record began in 1940). The forecast high for Concord
 is 16 degrees, which would also be in the top 10 coldest for
 this date (period of record began in 1868). Northwesterly wind
 gusts up to 25-30 mph will send windchills to within a few
 degrees either side of zero through the day.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Skies will remain clear through tonight as the surface high
arrives from the west. The latest RAP13 shows 1000mb geostrophic
winds diminishing below 15 kts in most locations after midnight,
which should result in most locations to decouple overnight.
This combined with the low dew points and clear skies will allow
for strong radiational cooling to occur. The only fly in the
ointment is a lack in snow cover south of the mountains but
otherwise conditions should allow for the coldest night of the
season so far in many locations. Forecast lows range from
around 10 below in the sheltered valleys with single digits
either side of zero elsewhere.

High pressure will begin to retreat to our east on Monday ahead
of a frontal system to our west. Clouds will gradually increase
from west to east with perhaps a stray snow shower towards the
CT River Valley by early evening. Highs will be a little warmer
with teens and 20s from north to south.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Update...01z NBM guidance is in reasonable agreement with other
latest guidance in a light snow event for Monday night into
early Tuesday. Forecast has this well in hand as a 1 to 4 inch
snow event so no significant changes have been made.

Previously...

Overview...

The trough bringing the cold conditions moves east through
midweek as a ridge builds across eastern North America. A weak
shortwave crosses northern New England, likely bringing a light
snowfall for Christmas Eve to most of the area.

Details...

Snow will overspread the region from west to east on Monday
night with generally 1-4" likely by Tuesday morning before it
ends later Tuesday. For those that missed out on last night`s
snow, this system brings the best chance for a white Christmas.
At this point snowfall amounts look light, with a broad and
general 1-4 inches across most of the area. The track of the low
will be important, with less forcing and less snowfall south of
the track. There is also the chance for some slightly higher
amounts through the higher terrain, and toward the MidCoast.
Across the higher terrain and north of the track, high snow to
liquid ratios should help to support slightly higher snowfall
amounts, but exactly where remains in question. Towards the
MidCoast, more moisture is likely drawn in off the ocean as the
low begins to slowly strengthen, also helping to increase the
chance of slightly higher totals here. Parts of southern Maine
and southern New Hampshire are likely to be on the lower end for
this event, with the bulk of the forcing missing to the north,
so this area remains the most in question as to whether or not
enough snow will fall to stick around until Christmas morning,
but it still looks like a decent chance at this point.

The low moves eastward Tuesday night, with some light snow
showers possibly lingering across eastern areas into Christmas
Day, but will be higher dependent on the strength of a lingering
weak inverted trough. Temperatures continue their gradual
warming trend, with highs along the coast starting to warm above
freezing, and mid 20s across the north.

The highly amplified ridge builds across central and eastern
North America through the end of the week, bringing a slow
moderating trend. Temperatures don`t actually rise all that much
considering how amplified the ridge is, and with it spreading
above freezing air across Hudson Bay. Instead, high pressure at
the surface remains centered across and just north of New
England, helping to filter in some relatively cooler air in an
otherwise very warm pattern. So while it`s not a snow lover`s
dream, it`s not a nightmare either. Highs warm to near 40 along
the coast by the end of the week, with mid 30s across the
interior. And with high pressure in place, lows continue to drop
into the teens and 20s each night.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Short Term...VFR conditions will prevail today through Monday.
Northwesterly wind gusts up to around 25 kts will persist
through 00Z Monday before diminishing to 5-10 kts tonight. Winds
will then become southwesterly on Monday but largely remaining
below 20 kts. No LLWS is anticipated.

Long Term...Light snow brings restrictions on Tuesday with MVFR
to IFR conditions likely. VFR conditions then return by
Wednesday, and likely continue through the remainder of the
week.

&&

.MARINE...
Short Term...SCA level northwesterly winds along with seas
will continue through today before diminishing early this
evening, although elevated seas will persist a few more hours
across the outer waters. High pressure then builds tonight into
Monday with lighter winds and seas. Light freezing spray
remains possible through this evening.


Long Term...A weak low pressure system crosses the waters Monday
night into early Tuesday with snow, but conditions remain below
SCA levels. Fair conditions return and continue from Wednesday
through the end of the week.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Cold Weather Advisory until 10 AM EST this morning for
     MEZ007>009.
NH...None.
MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ150-
     152-154.
     Small Craft Advisory until 4 PM EST this afternoon for ANZ151-
     153.

&&

$$

NEAR TERM...Tubbs
SHORT TERM...Tubbs
LONG TERM...Clair/Ekster