BOX issues Area Forecast Discussion (AFD) at Jan 20, 3:44 AM EST166
FXUS61 KBOX 200844
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
344 AM EST Mon Jan 20 2025
.SYNOPSIS...
The last of the snow will be exiting the region by daybreak.
Otherwise...an arctic airmass will bring frigid conditions with
minimum wind chills on the order of 0 to 15 below zero at times
through Wednesday morning. Temperatures moderate a bit Thursday and
Friday, but they will remain below normal. Dry weather will
generally prevail the rest of this week...but will need to watch a
couple distant waves of low pressure in case they trend further
northwest.
&&
.NEAR TERM /THROUGH TODAY/...
Key Points...
* Last batch of showers moves across early this morning with
snow ending in the 4am-7am timeframe from west to east.
* Below normal temperatures with a few pockets of flurries in
afternoon.
Radar early this morning displays one last batch of snow push
across southern New England. This batch has a mix of light and
moderate snow. Radar QPE estimates rates in the more enhanced
band to be around .06/.07" which should translate to more
moderate snow rates. Surface stations have reported visbilities
around 3/4 mile during this band. This band should push across
the eastern MA over the next few hours. Behind this band, there
are lighter snow showers that move across the region. This still
puts us on track for snowfall ending between 4am-7am. For those
commuting this AM, the main concern will be slick and snow
covered roads, especially if untreated.
Cold will be the main story for the weather today. A well below
normal airmass advects into the region starting today. 850mb
temperatures fall to This will keep highs in the low to mid 20s
for most areas and upper 20s for the Cape and islands. As a
sidenote, even colder air moves in by tomorrow, so be prepared
for that. As more enhanced pressure gradient this morning will
keep elevated NW winds with periods of gusts up to 25 mph. This
wind will also unfortunately make it feel even colder with wind
chills in the single digits today. Please dress in layers and
cover any exposed skin if planning to be outside today. As weak
high pressure builds in this afternoon, winds weaken and turn
westerly in most spots. Higher elevation spots may take a bit
longer to decouple (this evening). Expect mainly dry conditions
today; however, can't rule out a low chance (< 10%) for a pocket
or two of flurries/showers across the interior this afternoon
with some residual moisture around.
&&
.SHORT TERM /TONIGHT/...
Key Points
* Very cold with lows in the single digits and wind chills in
negative single digits.
The arctic airmass settles further over the region tonight.
850mb temperatures plummet to -20 to -22C overnight. The
combination of weakening winds, clear skies, and recent snowfall
ontop of the artic airmass will support low temperatures in the
single digits with some spots nearing zero. Even with a lighter
wind, wind chills get into the negative single digits overnight
for much of southern New England.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Key Messages...
* Bitterly Cold Wind Chills 0 to 15 Below Zero Tue AM/Wed AM
* Highs Tue & Wed mainly in the upper teens to the lower 20s
* Low Temps Tue night/Wed night single digits with some below zero
* Temps gradually moderate Thu/Fri...but still below normal
* Mainly dry this week...but watching distant system Thu night/Fri
Details...
Tuesday and Wednesday...
An arctic airmass will be entrenched in the area Tue and Wed. 850T
near -21C/-22C on westerly flow will result in well below normal
temps. Highs will be mainly in the upper teens to the lower 20s Tue
and Wed. Low temps Tue night will generally be mainly in the single
digits with some spots likely dropping below zero.
While this will be an arctic airmass...its delivery is from the west
as opposed to the north northwest when we often get our most extreme
cold temperatures. Nonetheless Wind Chills Tue AM and Wed AM will be
between 0 and 15 below zero. We will be close to the criteria for
Cold Weather Advisories...but because its right on the cusp we will
defer that decision to the next shift.
We will need to watch a weak wave of low pressure passing well
southeast of the Benchmark Tue night into Wed am. The vast majority
of the region will remain dry. Worst case scenario would brief
period of ocean enhanced light snow showers for mainly the Cape and
Islands. Either way no real impact expected.
Thursday/Friday...
A ridge of high pressure shifts east of the region by Thu. This
allows a southwest flow of slightly milder air to work into the
region. Highs Thu/Fri will mainly be in the upper 20s to the lower
30s...so still below normal albeit an improvement from what we will
see the next few days.
We also will need to keep an eye on a southern stream shortwave that
is going to bring snow/ice right down to the Gulf Coast early this
week. However...the upper level pattern does not appear to be
amplified enough to bring the system close enough for much of an
impact for us Thu night/Fri. However...there are a few individual
ensemble members that have the storm close enough to us for a period
of snow. Thinking this is a low probability at this point given the
upper level pattern...but given it is a day 4/5 forecast we still
will need to watch it.
Next Weekend...
It appears that a deep upper trough forming over the southwest U.S.
will pump up height fields across the mid-Atlantic and especially
the southeast. This should result in a more of a west southwest flow
of air across the region next weekend. Highs probably well into the
30s Sat and perhaps even some 40+ readings by Sun. Not looking at
any significant storms at this time...but perhaps we see a few warm
advection snow showers sometime Sun.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Today...High Confidence.
IFR in -SN with periods of LIFR possible in any heavier snow
bands that develop early this morning. One last round of light
snow moves across from 06-10z. Conditions will improve to VFR by
daybreak Monday. Total snow accumulations of 3-6"(south and
east)/4-8"(north and west) will be common for much of the region
northwest of the Cape Cod Canal.
NW winds with gusts of 20-25 kts possible today. Brief gusts to
30 kt possible across the Cape and at ORH. Winds decrease in the
afternoon to early evening.
Tonight...High Confidence.
VFR conditions with light west winds less than 10 kts.
KBOS TAF...High Confidence in TAF.
KBDL TAF...High Confidence in TAF.
Outlook /Tuesday through Friday/...
Tuesday through Wednesday: VFR. Breezy.
Wednesday Night: VFR.
Thursday: VFR. Breezy.
Thursday Night: VFR. Slight chance SHSN.
Friday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High- greater than 60 percent.
09Z Update...
High confidence...
Winds in the northern outer waters are expected to decrease
below Gale thresholds early this morning. Will let the Gale
Warning expire at 12z and re-issue as a SCA through 12z Tuesday.
Otherwise, expect SCAs generally through 12z Tuesday. Seas 4-9
ft.
Outlook /Tuesday through Friday/...
Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Freezing spray.
Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Freezing spray, slight chance of snow showers.
Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft. Freezing spray.
Wednesday Night: Winds less than 25 kt.
Thursday: Winds less than 25 kt. Slight chance of snow showers.
Thursday Night: Winds less than 25 kt. Chance of snow showers.
Friday: Winds less than 25 kt. Local rough seas. Slight chance
of snow showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Storm Warning until 7 AM EST this morning for
CTZ002>004.
MA...Winter Storm Warning until 7 AM EST this morning for
MAZ002>016-026.
Winter Weather Advisory until 7 AM EST this morning for
MAZ017>021.
RI...Winter Storm Warning until 7 AM EST this morning for RIZ001-
002.
Winter Weather Advisory until 7 AM EST this morning for
RIZ003>007.
MARINE...Small Craft Advisory until 7 PM EST this evening for
ANZ230>234-236.
Small Craft Advisory until 4 AM EST Tuesday for ANZ235-237.
Gale Warning until 7 AM EST this morning for ANZ250.
Small Craft Advisory until 1 AM EST Tuesday for ANZ251.
Small Craft Advisory until 3 PM EST Tuesday for ANZ254>256.
&&
$$
SYNOPSIS...Frank/Mensch
NEAR TERM...Mensch
SHORT TERM...Mensch
LONG TERM...Frank
AVIATION...Frank/Mensch
MARINE...Frank/Mensch
Source:
BOX issues Area Forecast Discussion (AFD) at Jan 20, 3:44 AM EST----------------
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