BOX issues Area Forecast Discussion (AFD) at Feb 18, 6:20 AM EST159
FXUS61 KBOX 181120
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
620 AM EST Tue Feb 18 2025
.SYNOPSIS...
Very cold temperatures along with strong winds continue today. It
still will be cold on Wednesday but with much less wind. A coastal
storm may brush the far southeast New England coast with some
accumulating snow Thursday into Thursday night. Trending milder
and drier Friday into the upcoming weekend.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Key Messages...
* Bitter Cold Wind Chills of 0 to 15 below into mid-morning
* Windy & very cold today...High Mainly lower-middle 20s
* A brief spot snow shower possible in western MA/CT
Details...
Strong sub 970 mb low pressure system across the Canadian Maritimes
will continue to result in unseasonably cold and windy weather
across southern New England today. The windy conditions will result
in Wind Chills of 0 to 15 below zero into mid morning with the
coldest readings in the highest terrain. A Cold Weather Advisory
remains in effect for the high terrain of the Berks and Worcester
Hills. Despite partly sunny skies...850T near -20C will result in
high temps close to 15 degrees below normal for this time of year.
Highs should mainly be in the lower to middle 20s today with some
upper teens across the highest terrain. Wind Chills this afternoon
will only be in the single digits and lower teens.
The strong low pressure system in the Maritimes will bring a WNW low
level jet on the order of 45-55 knots. The very cold temps aloft
will result in steep low level lapse rates and excellent mixing of
the low level jet. While winds will not be quite as strong as
yesterday...it will still be quite windy. Diurnal heating will allow
westerly wind gusts of 40 to 55 mph across much of the region with
perhaps a few brief gusts near 60 mph in the high terrain. We will
continue the Wind Advisory for most locations with the High Wind
Warning for the high terrain of the Berks and Worcester Hills.
Lastly...strong/very cold westerly flow may allow a long lake effect
streamer to survive for a time into portions of western MA/CT today.
If this occurs...will be very localized but is a possibility.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Key Messages...
* Blustery and very cold tonight with lows between 5 and 15 above
* Wind Chills Dropping to between 0 to 10 below overnight
* Plenty of sunshine Wed...but with much less wind & highs 25-30
Details...
Tonight...
Low pressure will lift well north of the Canadian Maritimes tonight.
This weakens the pressure gradient enough to allow winds to diminish
a bit...but it still will remain breezy overnight. The atmosphere
will still not be able to decouple though which should keep temps
from completely bottoming out. Nonetheless...lows to drop to between
5 and 10 above across the high terrain to between 10 and 15
elsewhere. Enough wind will result in Wind chills dropping to
between 0 and 10 below zero overnight...but should remain above the
thresholds for any additional Cold Weather Advisories.
Wednesday...
A shortwave dropping southeast into the northern plains will result
in heights rising a bit across southern New England Wed. While temps
will still be unseasonably cold...we do expect afternoon highs to
recover a bit into the 25 to 30 degree range along with plenty of
sunshine and a lot less wind. Still a bit of a breeze...but much
less than what we will see today.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Key Messages:
* Very cold Wednesday night, followed by below normal temperatures
through the end of the workweek, then temperatures moderate into
this coming weekend.
* Snow is possible for the south coast, Cape Cod, and the islands
from Thursday into Friday, with the passage of a coastal system.
* Less active period of weather Friday night into this upcoming
weekend, lesser confidence into early next week.
Wednesday Night: Expecting a fairly cold night with temperatures
dipping into the single digits across the region with "warm" areas
along the immediate coast, Cape Cod, and the islands, it is here the
lows dip into the teens and low 20s. Not much wind to knock down
temperatures any further, though there may be enough wind in the
Berkshire and northern Worcester Hills to make it feel between 0F
and -10F, shy of the criteria for cold weather advisories.
Thursday and Thursday Night: We continue to monitor the potential
for a coastal low pressure system to develop off the southeast coast
of the CONUS and then travel NNE, passing off shore during the day
through Thursday night. Should have enough cold air locked in place
to limit PType to snow, thanks to strong high pressure to our
north/west. Highs range from the upper 20s to low 30s. At current,
the 00z set of guidance continues to indicate a close brush, with
the greatest chance for accumulation of snow along the immediate
south coast of Rhode Island and Massachusetts, which includes, the
islands and Cape Cod. The outlier is the NAM12km, this would bring
the system closer to shore and more QPF. Worth a mention, but not a
likely outcome at this point. FWIW, across Cape Cod and the islands
the DESI probability of 3" or more of snow during a 24 hour period
are between 40 to 50 percent. Further inland, areas along the I-95
corridor between Boston and Providence, there are low probabilities,
less than 30 percent for 1" or greater of snow during a 24 hour
period.
As the low lifts away from the region, draws in colder air and
temperatures fall back into the teens, along with gusty northwest
winds.
Friday through Sunday: Surface low pressure system exits early
Friday morning, outside of a lingering snow showers across eastern
Massachusetts, there is a drying trend through the weekend. Mid-
level ridging develops along with surface high pressure, this helps
to moderate temperatures into the upper 30s. Will watch a trailing
trough and shortwave late on Sunday, while there is little moisture
associated, can not rule out a passing rain/snow showers. Early next
week there are signs of continued moderation in temperatures with
highs reaching the low 40s. As for the next impactful weather, there
remains too much spread in the guidance at this time, leaned on the
NBM for POPs, which has chance rain/snow showers possibly late
Monday into Tuesday.
&&
.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF Update...
Today...High Confidence
VFR outside of perhaps a brief localized flurry/snow shower in
western MA/CT. Westerly wind gusts between 35 and 45 knots.
Tonight...High Confidence.
VFR. W wind gusts diminish but still expect gusts to persist
in the 15 to 30 knot range well into the overnight hours.
Wednesday:
VFR. NW winds diminishing throughout the day, gusts earlier on
20 to 25 knots, but subside to less than 15 knots late
afternoon.
KBOS TAF...High Confidence in TAF.
KBDL TAF...High confidence in TAF.
Outlook /Wednesday Night through Saturday/...
Wednesday Night: VFR. Breezy.
Thursday through Thursday Night: Mainly VFR, with local MVFR
possible. Breezy. Slight chance SN.
Friday through Friday Night: VFR. Breezy.
Saturday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
High Confidence...
* Gale Warnings continue through tonight
* Freezing Spray Advisories continue into mid morning Wed
Today into Wednesday...High Confidence.
Strong low pressure lifting north of the Canadian Maritimes will
continue to result in strong cold advection with W wind gusts of 35
to 45 knots into tonight. While the stronger of these winds will be
today...still expect Gale force gusts to persist into tonight. The
pressure gradient should drop enough on Wed...so that small craft
headlines will be able to replace the current Gale Warnings.
In addition...given the very cold airmass moving across the waters
expect areas of moderate freezing spray into mid morning Wed.
Freezing Spray Advisories remain in effect.
Outlook /Wednesday Night through Saturday/...
Wednesday Night: Winds less than 25 kt.
Thursday: Winds less than 25 kt. Chance of snow.
Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Chance of
snow, chance of freezing spray. Local visibility 1 nm or less.
Friday through Friday Night: Low risk for Small Craft Advisory
winds with gusts up to 25 kt. Seas up to 5 ft. Chance of
freezing spray.
Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory until 5 PM EST this afternoon for CTZ002>004.
MA...Wind Advisory until 5 PM EST this afternoon for MAZ003-005>007-
010>024.
High Wind Warning until 5 PM EST this afternoon for MAZ002-004-
008-009-026.
Cold Weather Advisory until 10 AM EST this morning for MAZ002-
004-008-009-026.
RI...Wind Advisory until 5 PM EST this afternoon for RIZ001>008.
MARINE...Gale Warning until 10 PM EST this evening for ANZ230-236.
Freezing Spray Advisory until 10 AM EST Wednesday for
ANZ230>237-250-251-254>256.
Gale Warning until 5 AM EST Wednesday for ANZ231-250-251-254.
Gale Warning until 1 AM EST Wednesday for ANZ232>235-237.
Gale Warning until 4 AM EST Wednesday for ANZ255-256.
&&
$$
SYNOPSIS...Frank/Dooley
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...Dooley
AVIATION...Frank/Dooley
MARINE...Frank/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Feb 18, 6:20 AM EST----------------
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