BOX issues Area Forecast Discussion (AFD) at Jan 15, 8:55 PM EST306
FXUS61 KBOX 160155
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
855 PM EST Wed Jan 15 2025
.SYNOPSIS...
Quiet weather overnight and Thursday. A weak low pressure system may
produce some flurries or light snow showers Thursday night.
Temperatures modify to near to above normal levels by late in
the week into the weekend. A passing frontal system will bring
light amounts of rain and higher elevation snow showers
Saturday. Monitoring potential storminess late Sunday night or
Monday but uncertainty remains large. Below normal temperatures
and potentially low wind chills then set in by early to middle
of next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Key Messages...
* Mostly clear tonight with diminishing wind, lows in the teens
Previous forecast is on track. A ridge of high pressure building
to our south will allow winds to continue to diminish overnight.
Skies should be mostly clear except for some ocean effect clouds
across the outer-Cape. Overnight low temps will mainly be in the
teens...but a few high single digit readings are possible in the
normally coldest outlying locations of western MA.
Meanwhile...ocean effect clouds may hold overnight low
temperatures in the lower 20s across the outer-Cape and perhaps
Nantucket.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
335 pm update
Key Messages:
* Perhaps flurries/light snow showers along the south coast
Thursday night.
Again, no significant changes to prior forecasts. Expect a fairly
quiet weather day on Thursday. Still a chilly airmass in place, with
925mb temperatures around -10C. This supports high temperatures in
the upper 20s to lower 30s across the region. A fast moving
shortwave will be approaching the region later in the day, so expect
increasing mid-level clouds as the day goes on. The trough passes
through Thursday night, but with a very dry airmass (precip water
values less than 0.3") and no real strong dynamics, any
precipitation will be light. Hi-res guidance suggests perhaps a
little bit of light snow, especially closer to the south coast, but
no robust signal. Kept the PoPs to the 30% range for that area.
Nothing more than a dusting of snow is expected. Could be flurries
elsewhere across southern New England, but given it's mid-winter,
that really isn't anything noteworthy.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
335 pm update
Key Messages:
* Warming trend to temps Fri-Sun, with passing rain and higher
elevation snow showers for Sat.
* Light-accumulating fluffy snow possible Sun night into early Mon,
although still too uncertain for accumulations at this time.
* Below normal temps and low wind chills for early to mid next week
associated with coldest airmass to this point in winter. Highs may
struggle to reach the mid teens in interior CT and MA.
Details:
Friday Through Sunday:
Warming trend takes place in this timeframe as high pressure moves
offshore and ushers in an increasing southerly flow. High temps are
expected to rise into the mid 30s to lower to mid 40s by Sat into
Sun. Despite the
Although Fri looks dry, a weak frontal system spreads a round of
precipitation into Southern New England for Sat. Temps look to be
warm enough for rain in most locations, with snow mixing in across
the higher elevations in the Berkshires. Total QPF related to this
system looks low, with most ensembles indicating QPF amts of a
quarter-inch or less. Overall impacts look minimal to minor with
regard to this system. PoPs then decrease briefly into Sun, with dry
but cloudy weather.
Sunday Night / Early Monday:
We continue to monitor developments regarding the potential for low
pressure development around late Sunday night into early on Monday
timeframe. This is associated with a shortwave disturbance at 500 mb
rotating around a deep longwave trough that is forecast to usher in
the coldest airmass to this point in winter 2024-2025. This forecast
setup is one where sfc low pressure may develop along a strong
frontal boundary with related precip falling on the cold side of the
frontal zone, in an anafrontal-wave low configuration.
Exactly where and if this development occurs varies across the
global NWP, which contributes much uncertainty in the forecast.
Cluster analyses of the various global ensemble members, in
particular, key on details regarding the strength of the initiating
shortwave as it digs into the Four Corners region late Fri night/Sat
will greatly shape where and how strong this low pressure may
become. The international suite of guidance is a bit more bullish on
QPF related to this wave, while the GFS is further offshore but
would still bring a more limited degree of QPF to eastern portions
of SNE.
The potential exists for at least a light/minor accumulation of snow
during the overnight hours into early Monday. With few exceptions,
past anafrontal-wave type lows are not typically substantial precip-
makers and the fast 500 mb WSWly belt of flow could favor a more
progressive/faster-moving wave. Depending on how quickly the colder
air filters in, any snow which develops could have a more
fluffy/powdery character. But given the above uncertainties in large-
scale fields, it is still too early to provide specifics on
accumulations at this time.
Early to Mid Next Week:
Although it looks dry, the main story in this period is well below
normal temperatures and low wind chills associated with what is
easily the coldest airmass to this point in winter 2024-2025.
Coldest air settles in on Tue and Wed with 925 mb temps falling to
around -17 to as low as -20C! Note that MEX MOS forecast lows are
some 10-15 degrees below late Jan climatology highs, and since MEX
MOS forecasts tends to lean closer to climo in later forecast
timeframes, these anomalies compared to MOS are a pretty telling
signal about the potential for below normal temps.
Highs in some interior locations may struggle to reach the mid
teens, with upper teens to mid 20s for the coastal plain/larger
cities. Although there are solid probs of sub-zero windchills, how
low wind chills may get is still unclear as this will obviously
depend on wind speeds. Pending those values, it is not out of the
realm of possibility that cold hazard headlines could be needed in
some locations in this timeframe.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update:
Tonight: High confidence.
VFR. NW gusts to 25 kt should dissipate by 00-03z, then become
around 5-8 kt into the overnight. Will see increasing high
clouds approach BAF/BDL toward early Thu.
Thursday and Thursday Night: High confidence, but becomes
moderate to high late Thursday/Thursday night.
VFR, although with increasing canopy of mid/high clouds during
the day. Winds to become WSW around 5 kt. Late Thurs and Thurs
night, layer of BKN/OVC VFR-MVFR low clouds advect northward as
weak low pressure moves across Southern New England. Possible
there could be some unresticted-visby flurries or at worst
MVFR-visby light snow showers but shouldn't be anything more
than that. SW winds around 5 kt Thurs night.
KBOS TAF...High confidence in TAF. Mainly VFR with decreasing NW
winds, which become light SW early Thurs. Late Thu/Thurs night,
may see OVC 030-040 bases with outside chance at flurries but
not much worse.
KBDL TAF...High confidence in TAF.
Outlook /Friday through Monday/...
Friday: VFR.
Friday Night: VFR. Breezy.
Saturday: Mainly VFR, with local MVFR possible. Breezy. Chance
RA.
Saturday Night: Mainly VFR, with local IFR possible. Breezy.
Chance RA.
Sunday: VFR. Slight chance RA, slight chance SN.
Sunday Night: VFR. Breezy. Chance SN.
Martin Luther King Jr Day: VFR. Breezy. Slight chance SN.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High- greater than 60 percent.
335 pm update
High confidence.
Winds will be diminishing overnight, so the current projection that
small craft advisories will be able to be discontinued look to be on
track. Generally light winds (15kt and less) are expected Thursday
night through Friday.
Outlook /Friday through Monday/...
Friday through Friday Night: Winds less than 25 kt.
Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. Chance of rain.
Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Rain
likely.
Sunday: Winds less than 25 kt. Local rough seas. Chance of
rain.
Sunday Night: Winds less than 25 kt. Areas of rough seas.
Chance of rain, chance of snow.
Martin Luther King Jr Day: Low risk for Small Craft Advisory
winds with gusts up to 25 kt. Areas of rough seas. Chance of
snow, chance of freezing spray.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until midnight EST tonight for ANZ230>237.
Small Craft Advisory until 6 AM EST Thursday for ANZ250-251-
254>256.
&&
$$
SYNOPSIS...Loconto/Nash
NEAR TERM...Frank
SHORT TERM...Nash
LONG TERM...Nash
AVIATION...Loconto/Nash
MARINE...Loconto/Nash
Source:
BOX issues Area Forecast Discussion (AFD) at Jan 15, 8:55 PM EST----------------
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