Keene, New Hampshire 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

212
FXUS61 KGYX 240405
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1105 PM EST Sat Nov 23 2024

.SYNOPSIS...
Low pressure will slowly move NE through the Canadian Maritimes
through Sunday night. High pressure briefly builds in for
Monday. A quick hitting system crosses Tuesday bringing wintry
precipitation across the north and mainly rain south of the
foothills. Brief high pressure crosses southern New England late
Wednesday into Thursday. The next low pressure system tracks
from the Ohio Valley towards New England late Thursday into
Friday.

&&

.NEAR TERM /THROUGH SUNDAY/...

11:00pm Update... Tweaked POPs a bit for tonight and tomorrow,
generally increasing POPs across northern areas. Upslope snow
and snow showers continue across the north, with ample moisture
upstream through Quebec. Otherwise, the forecast remains on
track with no other notable changes.

7:00pm Update... No notable changes with this update as the
forecast remains on track. Upslope snow showers continue north
of the mountains, while brief isolated sprinkles and flurries
continue south of the mountains. Winds remain gusty, and will
only ease slightly through the overnight hours.

Previous...

Moist easterly flow has largely been confined to the upper
levels across the forecast area. Closer to the surface winds
have turned northwesterly and downsloping is already occurring
southeast of the White Mtns. Overcast is breaking up across
NH...and that will slowly creep northeast into ME this evening.
Rain will be most likely near Penobscot Bay...closer to the main
forcing from the low pressure over Nova Scotia. Upslope showers
will also be likely along the northwest facing slopes of the
higher terrain. Otherwise I do not anticipate much more than a
sprinkle or flurry downwind of the mtns thru the overnight.
Winds remain breezy to occasionally gusty overnight so I have
blended in raw 2 m temps to keep min temps up slightly.

&&

.SHORT TERM /SUNDAY NIGHT/...
The region will remain under the influence of Maritime low
pressure Sun. Forecast winds at 925 mb are fairly similar to
today...but perhaps we get a little deeper mixing Sun. The
result will be more widespread and more consistent gusts up to
30 or 35 mph. The deeper mixing will also allow inversion to
lift above the ridgeline and Froude numbers are forecast to
approach at least 2. I expect some upslope precip to hold
together downwind of the mtns. However I do not expect it to be
very heavy...so I have mainly added sprinkles/flurries. The low
levels are fairly dry so wet bulb temps will be pretty close to
freezing. I suspect more flurry than sprinkle out of any upslope
precip.

CAA will continue on the backside of low pressure. A steadily
falling temp is expected Sun night. Once again I blended raw 2 m
temp guidance into the min temp forecast to prevent any
radiative effect from showing up.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...

Long Term Update...

Brought in some freezing rain chances for Tuesday morning
across parts of the interior, and especially through the
northern valleys. The window for this would be brief before
changing to either rain or snow, but even light amounts on
untreated roads could be enough to bring some slick travel
across northern valleys. Should the precip move in a little
later in the morning, the concern would be lower with the
daytime insolation warming the low levels. But if the precip
arrives a little earlier, which often happens with WAA systems,
the chances for this period of light freezing rain would be
greater. Either way, by midday the secondary low pressure is
expected to organize, drawing in cooler air through the
atmosphere and allowing for just rain or snow.

The next system for late Thursday through Friday looks to be
coming into better focus, with the GFS and its ensembles coming
more in line with the Euro. The latest Euro run was also a
little less amplified and cooler than the 12z run, but it`s
still too early to draw any conclusions on a rain/snow line
placement trend from just this one run. Either way, confidence
is relatively high and increasing for a system during this
timeframe, with precip type and placement remaining the biggest
uncertainty factors.

Full Discussion...

Overview:
Confidence is increasing in the development of an upper level
flow pattern that will deliver cold air into the central and
eastern CONUS starting around the middle of next week. Recent
runs of global ensembles have been showing strong ridging
building from eastern Siberia across Alaska into western Canada
associated with a -WPO and -EPO. Meanwhile, the NAO is projected
to turn more negative the second half of the week favoring a
storm track along the East Coast. Before the aforementioned
pattern comes to fruition, northern New England will be poised
to receive widespread precipitation from a short wave swinging
across the region Tuesday. Colder air will move in behind this
system with global models suggesting a more robust system
tracking near the Northeast coast around Friday. This late week
system will involve the phasing or non phasing of northern
stream and southern stream energy leading to large variance and
uncertainty in model solutions.

Impacts:
*Wintry precipitation in the foothills to points north could
 bring slick travel Tuesday.

*Low pressure tracking near the Northeast late Thursday and
 Friday could bring wintry precipitation to the region. Large
 variance and uncertainty with this system will likely continue
 for several days, but there is potential for impacts to travel
 during a time of high travel volume.

Details:
Low pressure in the Canadian Maritimes lifts northeastward
Monday morning with a short wave ridge moving into New England
Monday evening. This will allow for fair weather with decreasing
winds. Highs on Monday will range from the mid 30s north to
upper 40s south.

A short wave trough swinging through the Great Lakes Monday
night will spawn a surface low that tracks towards the St
Lawrence Valley Tuesday. Several models solutions within the 12Z
suite suggest a secondary coastal low will spin up in the Gulf
of Maine Tuesday. Overall, this looks to be a quick hitting
system with QPF around 0.5 inches. On the other hand,
precipitation types are tricky depending on how cold the area
can get Monday night and the timing of precipitation onset
Tuesday morning. Model soundings suggest that areas from the
foothills northward could see a period of wintry mix Tuesday
morning around the time of the morning commute with mainly rain
along the coastal plain. Depending on the strength of the
coastal low, temperatures will rise above freezing south of the
mountains Tuesday morning with rain becoming the dominant
precipitation type. This system exits Tuesday night with upslope
snow showers continuing in the mountains into Wednesday
morning.

High pressure slides across southern New England late Wednesday
and Thursday morning for mostly dry conditions. Global models
and their ensembles suggest a robust area of low pressure will
track from the Ohio Valley to the East Coast late Thursday and
Friday. One of the sources of this system is currently offshore
the Pacific NW and the other can be traced back to the Bearing
Sea. The phasing or non phasing of these features has produced
run to run and model to model variance in this system. Ensembles
loosely cluster a track along the southern New England
coastline that would favor widespread wintry precipitation
across the area centered on Thursday night into Friday. It will
likely take several days to iron out the evolution of this
system, but it will be one worth watching giving the elevated
travel around the holiday.

&&

.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
Short Term...CIGs continue to improve for most areas as winds
become northwesterly. There remain areas of MVFR CIGs...but
these are largely expected to lift or scatter out this evening.
The one exception will be northwest of the mtns into the Upper
Valley...where upsloping winds will keep MVFR CIG possibly thru
Sun. SHRA/SHSN are most likely around HIE thru the
overnight...and local IFR is possible if ptype is mostly SN.
Surface gusts around 25 kt are expected at all terminals thru
Sun...except at HIE where cloud deck will limit mixing.

Long Term...Mainly VFR Monday into Monday night. Cigs thicken
and lower early Tuesday morning with a brief wintry mix possible
from KLEB to KAUG and points northward before changing to rain
with all rain across the south. This will likely result in MVFR
to IFR Tuesday. Conditions improve Tuesday night into Wednesday
with VFR likely into Thursday.

&&

.MARINE...
Short Term...Gusty winds continue over the coastal waters thru
most of the evening Sun. Low end gale force gusts over most
waters will continue into Sun. The exception will be Casco Bay
where fetch is just not long enough and winds not strong enough
to generate consistent gale force gusts. Winds begin to diminish
later Sun...but SCA conditions linger over all waters into Mon
morning.

Long Term...NW winds likely continue SCA conditions Monday
morning with winds and seas dropping below SCA thresholds Monday
afternoon into Tuesday morning. Low pressure tracking west to
east across New England into the Gulf of Maine will bring a
return of SCA conditions Tuesday into Thursday morning.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Gale Warning until 6 PM EST Sunday for ANZ150>152-154.
     Small Craft Advisory until 6 PM EST Sunday for ANZ153.

&&

$$


NEAR TERM...Clair
SHORT TERM...Legro
LONG TERM...Schroeter