BOX issues Area Forecast Discussion (AFD) at Nov 22, 1:14 AM EST538
FXUS61 KBOX 220614
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
114 AM EST Fri Nov 22 2024
.SYNOPSIS...
Strong low pressure near western CT early this morning will
continue to move westward today into southern NY, then meanders
east and northeast into the Canadian Maritimes through the
weekend. Rains gradually decrease early this morning, with a
lull in the rain for most of today, but rain chances increase
again late this afternoon and tonight before pulling away into
early Saturday. Considerable cloudiness for this weekend with
gusty northwest winds. Brief dry weather returns on Monday. The
rest of the week looks active, with one storm system around
Tuesday spreading rain showers. Blustery, cooler and dry for
Wednesday, then monitoring for additional storminess around
Thanksgiving or Black Friday.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
7 PM Update...
Moist conveyor belt/firehose of Atlantic moisture with a very
large fetch from Georges Bank pivoting westward into SNE, is
providing a steady stream of light to moderate rain across the
area this evening. This will continue much of the night, with
steady rain tapering off toward morning, as the dry slot
overspreads the area. As the closed upper low over PA drifts
eastward overnight, associated cold pool aloft will begin to
cool the column over western MA/CT, resulting in rain mixing
with and changing over to snow at elevations AOA 1,500 ft.
Otherwise, a chilly/raw windswept rain continues tonight. Previous
forecast verifying nicely at 7 PM and captures the details
above. Therefore, no changes with this update. Earlier
discussion below.
-------------------------------------------------------------------------
* Periods of rain and fog tonight with gusty NE winds
* Any very minor wet snow accums confined to east slopes of Berks
Surface low pressure south of Long Island will gradually retrograde
northwest tonight in response the the deep closed upper level low
across PA. This will allow the easterly 850 mb LLJ to strengthen
between 45 and 55 knots tonight. In response...a band of good mid
level frontogenesis to lift northward across the region. The result
will be periods of rain and fog persisting tonight. It will also be
quite breezy with ENE wind gusts of 25 to 35 mph at times with the
strongest of those winds along the coast.
As the closed upper level low approaches from the west...some
cooling aloft will begin to work in from the southwest later
tonight. It may be just cold enough for rain to mix with or change
to wet snow in the highest terrain along the east slopes of the
Berks. Perhaps a coating to 1 inch of wet snow would be possible at
elevations near 1500 feet with a low risk of up to 2" late tonight
into Friday morning. Not much of an impact...but some very minor wet
snow accums are possible in the highest terrain late tonight into
Fri morning. Low temps should mainly be in the upper 30s to the
lower 40s...but a few degrees lower in the highest terrain.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/...
Key Points...
* Lull in most of the rain Friday morning into early afternoon
* Highs Fri mainly in the upper 40s to the middle 50s
* Next round of rain later Fri/Fri night eastern/northern MA
* Wet snow may mix in across highest terrain of Berks/N. Orh Hills
Details...
Friday and Friday night...
As the closed upper level low continues to lift northward to our
west...a dryslot should overspread much of the region Friday morning
into mid afternoon. So much of this time period will be dry except
for a few lingering showers mainly across western MA/western CT
closer to the upper level low. We may even see a peeks of sunshine
briefly with the best chance across eastern MA with the dryslot.
This should result in high temps recovering into the upper 40s to
the middle 50s on Fri.
The closed upper level low to our west will result in another piece
of shortwave energy approaching from the south. The track of this
piece of energy and how far west the main rain shield gets...but
appears eastern MA and northern MA stand the best chance for a
period of widespread rain later Fri into Fri night. Temps maybe
marginally cold enough for some wet snow in the highest terrain of
the Berks and northern Worcester Hills...but no real impacts
anticipated. Low temps should bottom out in the 30s to the lower 40s.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Highlights:
* Gradually drying out this weekend with seasonably cool temps, but
with NW gusts 25-40 mph Sat night into Sun early PM.
* Tranquil and seasonable Mon.
* Frontal system for Tue spreads lighter showers early on Tue, then
dry and blustery for Wed.
* Monitoring more active weather around the Thanksgiving holiday or
Black Friday, some of which could be wintry, but uncertainty is
very large.
Details:
Saturday Night and Sunday:
Strong low pressure over the Canadian Maritimes will continue to
slowly move ENE through the rest of the weekend. Tight NW pressure
gradient will continue to drive blustery NW winds. Approach of
secondary shortwave disturbance moving through Ontario SE into New
England late Sat night into early on Sun will increase a NWly low-
level jet, which global models indicate ~40-45 kt at 850 mb. Expect
a cloudy and blustery night Sat night with gusts 25-35 mph, on the
higher end of that range over the higher terrain. As mixing depth
increases with a bit more in the way of sun on Sunday, we could see
gusts punch into the 30-40 mph range into the early afternoon, near
Advisory levels, then decreasing into the midafternoon as the low
level jet weakens. The gusty conditions will make it feel much
cooler than forecast temps; lows Sat night in the mid to upper 30s
may feel more like the upper 20s to near freezing with the NW
breeze, and highs 45-50 on Sunday. Clearing skies will lead to a
chilly Sun night with lows in the upper 20s to the lower to mid 30s,
but will feel cooler with a continued NW wind around 10-15 mph.
Monday:
Monday likely to be the pick of the forecast with high pressure
ridging in, offering full sun and a slackening wind. Modest warm
advection with 925 mb temps up to around +4 to +6C brings highs into
the low to mid 50s.
Monday Night thru Tuesday Night:
The 500 mb pattern becomes more active starting in this period,
continuing into the workweek, as spokes of shortwave trough energy
from the West Coast move across the CONUS. A lead shortwave moves
into the Gt Lakes and Northeast region into Tue, bringing a risk for
showers. However models vary on the strength of this wave with the
ECMWF on the weaker side, while the GFS and Canadian are a little
stronger and would offer a little more QPF. Highs around the 50s.
Wednesday:
Low pressure will have moved into the Maritimes early on Wed, and
other than northwest breezes, early look at conditions for the
biggest holiday travel day seem favorable with partly to mostly
sunny conditions and highs in the 40s to near 50.
Thursday/Friday:
Pacific frontal system moves across the central US, leading to a
developing storm system in the central Plains around Thurs. Quite a
bit of uncertainty exists in the details, though there appears
to be enough colder air in place to allow for some wintry
weather possibilities Thurs and/or Fri, provided there is a
favorable storm track. Kept PoP on the higher end of Chance but
will be monitoring model developments very closely.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06z TAF Update:
Through 12z Friday: High confidence in trends, though moderate
on the exact timing.
IFR ceilings with MVFR/IFR visbys in RA/FG with E/ENE winds
around 15-25 kt with gusts 25-30 kt, will continue at least for
a couple hours. As low pressure now over southern CT moves
westward into eastern NY between 07-12z, expect a rapid
decrease in rain and improving visbys from south to north, along
with winds shifting from SE to S with a decrease in speed to
around 10-15 kt with gusts 20-25 kt. The southerly windshift
will also lead to improvement in ceilings toward BKN/OVC MVFR,
with VFR over southeast MA. See TAFs for timing, though these
could slip by an hour or two.
Today: Moderate confidence.
Intermittent light rains with MVFR clouds for the interior, but
for RI and eastern MA, a lull in rains are expected for part of
the day with SCT-BKN VFR bases and southerly gusts around 20-25
kt.
Late in the day (thinking after 20z, although exact timing is
still a bit uncertain), another round of steadier rains develops
over the southeast waters and rotates NNW into at least eastern
MA and RI by 00z. As this rain moves in, expect ceilings
lowering to MVFR levels, S winds shifing to SE/E around 10-12
kt and visbys around 4-6 SM in -RA/RA.
Tonight: Moderate confidence.
VFR/MVFR deteriorates to MVFR/IFR ceilings at most airports,
with steadier RA at 4-6 SM vsby for at least eastern MA and RI,
possibly as far west as BAF/BDL but the western extent is still
uncertain. Rain should pull away toward the NE after 06z. SE/E
winds become NE around 10 kt thru midnight, and then NW around
5-10 kt overnight before increasing in speed to 10-15 kt by
daybreak Sat.
Saturday: Moderate to high confidence.
BKN/OVC MVFR/VFR ceilings with slow improvement trends. Gusty
NW winds around 15 kt with gusts 25-35 kt.
KBOS Terminal...Moderate confidence in TAF. IFR, wind-swept
rains on ENE winds gusting to 35 kt for another couple hours.
Windshift to SE/S around ~08-09z with rapid improvement in
cigs/vsbys toward MVFR-VFR. Otherwise, VFR with S around 10-15
kt/gusts to 25 kt most of the day. Another round of rain
develops after 19z with developing SE/E winds and deteriorating
cigs.
KBDL Terminal...Moderate confidence in TAF. IFR/MVFR ceilings
with MVFR rains on N winds initially. Abrupt windshift to SE/S
08-10z with categories trending MVFR. Otherwise, MVFR with more
intermittent -RA today on S winds around 10 kt.
Outlook /Saturday Night through Tuesday/...
Saturday Night: Mainly VFR, with local MVFR possible. Windy
with gusts up to 35 kt. Slight chance RA.
Sunday: VFR. Windy with gusts up to 35 kt.
Sunday Night through Monday: VFR. Breezy.
Monday Night: Mainly VFR, with local MVFR possible. Chance RA.
Tuesday: Mainly VFR, with local IFR possible. Breezy. Chance
RA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Friday night...
* Gale Warnings posted for tonight
Tonight...
Low pressure south of Long Island will gradually lift
northwest tonight. This will induce an easterly low level jet of 45
to 55 knots. Based on that...we opted to upgrade to Gale Warnings
tonight for most open waters with gusts to 35 knots expected. Seas
will build 7 to 11 feet across most open waters given the long
fetch. Areas of fog will also reduce visibility for mariners.
Friday and Friday night...
As the low pressure lifts northwest into eastern NY...the surface
winds will shift to the south by early Fri morning and turn more E
during the afternoon. Gusts will diminish...but seas will be on the
downturn but will still be above small craft levels.
Therefore...will need to replace the Gales with small craft
headlines.
Outlook /Saturday Night through Tuesday/...
Saturday Night: Strong winds with gusts up to 35 kt. Rough seas
up to 11 ft. Chance of rain.
Sunday: Low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 10 ft.
Sunday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.
Monday: Winds less than 25 kt. Seas locally approaching 5 ft.
Monday Night: Winds less than 25 kt. Chance of rain.
Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 4 AM EST early this morning for
ANZ230-236.
Gale Warning until 4 AM EST early this morning for ANZ231>235-
237-250-251-254>256.
&&
$$
SYNOPSIS...Loconto/RM
NEAR TERM...Frank/Nocera
SHORT TERM...Frank
LONG TERM...Loconto
AVIATION...Loconto/RM
MARINE...Loconto/RM
Source:
BOX issues Area Forecast Discussion (AFD) at Nov 22, 1:14 AM EST----------------
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