BOX issues Area Forecast Discussion (AFD) at Feb 19, 4:11 AM EST527
FXUS61 KBOX 190911
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
411 AM EST Wed Feb 19 2025
.SYNOPSIS...
Partly sunny and still cold today...but with much less wind than the
past two days. A distant ocean storm will brush the far southeast
New England coast with some accumulating snow Thursday into Thursday
night. Breezy and cold for Friday with the departure of a coastal low and
the building high pressure system to the west. Drier conditions as
well continues into this weekend with near normal temperatures.
Early next week signs of some unsettled conditions and slightly above
normal temperatures.
&&
.NEAR TERM /THROUGH TONIGHT/...
Key Messages...
* Partly Sunny & still cold today but with less wind
* Highs today mainly in the upper 20s/near 30
* Dry but cold tonight with lows mainly in the single digits & teens
Details...
Today...
The pressure gradient relaxes today as a ridge of high pressure
noses in from the west. There still will be a breeze from the
northwest at speeds of 20-25 mph...but quite a bit less wind
compared to the last two days. 925T are still quite cold in the -10C
to -12C range...so highs will just be a few degrees higher than
yesterday. Under partly sunny skies...highs should mainly be in the
upper 20s to near 30...but with much less wind than the last two
days it will feel more comfortable.
Tonight...
A ridge of high pressure continuing to nose in from the west will
result in light/calm winds and a good night of radiational cooling
tonight. Overnight low temps will mainly be in the single digits to
the lower to middle teens in the urban centers. We may even see a
few below zero readings in the typical coldest low-lying locations
in western MA.
&&
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
Key Messages...
* Snow grazes the far southeast New England coast Thu/Thu night
* Most likely snow accums...1-3" for the Cape/MVY & 2-5" for ACK
* Northwest extent of snow shield and accums may need to be refined
Details...
Thursday and Thursday night...
The main forecast challenge Thu into Thu night revolves around the
northwest extent of a snow shield from a distant ocean storm. This
low pressure system will be passing well southeast of the Benchmark.
Shortwave energy to the west coupled with subtle hints of an
inverted trough will attempt to push the snow shield towards the far
southeast New England coast. The question becomes just how far
northwest does this snow shield reach? The guidance remains split
with the NAM continuing to be the most robust and the UKMET/HRRR
indicating very little snow even for the Cape and Islands.
In a nutshell...do not think the main snow shield makes it much
further northwest than the Cape Cod Canal outside of very immediate
south coast and portions of Plymouth county. The main threat of
accumulating snow appears to be across the Cape and
Islands...especially Nantucket. The one thing that may be a bit of a
bonus for them is the cold/moist northerly flow as a result of the
distant ocean storm. This will result in the potential of ocean
enhancement with a delta T close to 15C from the top of the mixed
layer to the SST. We expect snow to develop during the daylight
hours of Thu and continue at times through Thu night.
Our best snowfall estimate at this time is for 1-3" across the
Cape/Marthas Vineyard and 2-5" across Nantucket. We went ahead and
issued a Winter Weather Advisory for Nantucket. If the storm system
trends further northwest...later shifts may have to consider
expanding the advisory onto the Cape/Marthas Vineyard and even a
marginal warning scenario would arise for Nantucket. However...if
the storm were to shift further southeast...snowfall accumulations
would be limited to a coating to 2" across the Cape/Nantucket. Later
shifts may certainly need to refine the forecast based on later
model runs.
Meanwhile...across the rest of the region expect generally dry
weather to persist with just increasing clouds during the day
Thu and persisting into Thu night. High temps should mainly be
in the upper 20s to near 30. Lows Thu night will mainly be in
the teens to the middle 20s.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
Key Messages:
* A lingering snow shower through Friday morning across far eastern
Massachusetts, otherwise dry, cold, and breezy.
* Fairly quiet weather this weekend and early next week. Will watch
a weaker shortwave slides through late Saturday night into early
Sunday, and then a potential clipper system for early next week.
* Temperatures moderate this weekend into early next week.
Friday: The low pressure system exits east of New England with high
pressure, 1035+ mb, building over the central CONUS, resulting in a
gusty period of weather due to the increased pressure gradient. At
this time, gusts remain below advisory criteria, though it is breezy
with gusts 20 to 30 MPH. Earlier in the morning, wind direction is
from the north, this may lead to a few ocean enhanced snow showers
across eastern coastal Massachusetts. As the wind direction becomes
more northwest to west/northwest these snow showers should subside.
Still a fairly cold day, considering average highs are between the
mid-30s and 40F. With 925mb temperatures between -8C and -10C, this
yields highs from the upper 20s to mid-30s. Dry conditions continue
into the overnight as the column dries out with surface high moving
east. Another chilly night ahead with lows in the single digits and
teens, compared to the average low of the low and middle 20s. If the
winds were to subside quicker, the forecast temperatures could be
too "warm", resulting in better radiational cooling, thus would need
to trend temperatures colder.
Saturday and Sunday: High pressure breakdown over the course of the
weekend, though should have fairly quiet weather during this period.
A subtle mid-level trough and associated weak shortwave crosses the
region sometime overnight Saturday into Sunday morning. Feel this
results in added cloud cover with a low chance for an isolated snow
shower. Temperatures trend slightly "warmer" with highs between the
middle and upper 30s, and overnight lows from the mid teens to the
mid-20s.
Monday through Wednesday: Mid-level features a few subtle troughs
and progressive shortwaves for the first-half of next week. While it
isn't an overly active week, there could be a few nuisance features
to keep us on our toes. Looking at ensemble guidance, there is some
agreement that a clipper system may sweep across New England late on
Monday night, perhaps early Tuesday, timing will be important if you
were to want one PType. Daytime highs are trending slightly above
normal Monday, Tuesday, and Wednesday with highs in the lower to
middle 40s. Nightly lows are near normal in the mid-20s.
&&
.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
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. W wind gusts diminish but still expect gusts to persist in
the 15 to 30 knot range.
Wednesday and Wednesday Night...High Confidence.
VFR. NW winds diminishing throughout the day, gusts earlier on
20 to 25 kts, but subside to less than 15 kts late afternoon.
KBOS TAF...High Confidence in TAF.
KBDL TAF...High confidence in TAF.
Outlook /Friday through Sunday/...
Friday through Friday Night: VFR. Breezy.
Saturday through Sunday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today through Thursday...High Confidence.
The pressure gradient will continue to gradually relax today...but
still expect northwest small craft wind gusts into the afternoon for
most of our waters. Winds and seas should lower later this afternoon
and drop below small craft thresholds across all our waters by early
evening. High pressure then noses in from the west keeping winds
below small craft thresholds tonight into Thu.
Thursday night...High Confidence.
A distant ocean storm will intensify and allow the pressure gradient
to increase. This will allow NW wind gusts of 20-30 knots to develop
and small craft headlines will likely be needed for most of our
waters.
Outlook /Friday through Sunday/...
Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Seas up to 5 ft. Chance of freezing spray.
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 through Sunday: Winds less than 25 kt. Seas locally
approaching 5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Winter Weather Advisory from 9 AM Thursday to 7 AM EST Friday
for MAZ024.
RI...None.
MARINE...Small Craft Advisory until 1 PM EST this afternoon for ANZ230-
232>237.
Freezing Spray Advisory until 10 AM EST this morning for
ANZ230>237-250-251-254>256.
Small Craft Advisory until 4 PM EST this afternoon for ANZ231-
250-251-254.
Small Craft Advisory until 7 PM EST this evening for ANZ255-
256.
&&
$$
SYNOPSIS...Frank/Dooley
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...Dooley
AVIATION...Dooley
MARINE...Frank/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Feb 19, 4:11 AM EST----------------
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