BOX issues Area Forecast Discussion (AFD) at Mar 1, 6:56 AM EST298
FXUS61 KBOX 011156
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
656 AM EST Sat Mar 1 2025
.SYNOPSIS...
Brief unseasonably mild temperatures today ahead of a strong cold
front will give way to sharply falling temperatures and strong
northwest winds later today and this evening behind the cold front.
The front may be accompanied by a few brief rain showers, possibly
snow showers across the high terrain. Windy and much colder weather
tonight with winds easing Sunday into Monday but remaining rather
cold. A warming trend starts Tuesday with a return to mild and
spring-like temperatures Wednesday and Thursday, but a frontal
system approaching from the west will bring widespread showers. A
cold front will cross the region late Thursday and return
temperatures to near seasonable highs by the end of next week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Key Messages:
* Breezy and unseasonably mild with early afternoon highs well into
the 50s. Southerly wind gusts 25-35 mph developing across
eastern New Eng with strongest gusts SE MA and Cape/Islands
* Arctic front passage this afternoon and evening will be followed
by rapidly falling temps and strong WNW winds with gusts to 35-45
mph possible
* A few spot showers possible, organizing along the front with snow
showers possible higher elevations
Strong low pres tracks across Quebec today with arctic front
approaching from the west. Pre-frontal low level jet ahead of the
front will bring gusty S-SW winds this morning into early afternoon.
The strongest gusts will be across SE MA and Cape/Islands where
gusts up to 35 mph are possible. A few spot showers are possible
this morning as area of enhanced moisture moves through, otherwise
expect partial sunshine developing. The southerly low level jet will
bring unseasonably mild airmass into SNE ahead of the front as 925
mb temps increase to near 6C. Highs will reach the mid-upper 50s
across much of the region, except 40s interior MA high terrain.
These temps will be realized by early afternoon before the frontal
passage.
The arctic front is expected to move through western New Eng 1-3 pm
and eastern New Eng 3-5 pm and will be followed by rapidly falling
temps and strong WNW wind gusts as very impressive cold advection
develops. In fact 925 mb temps fall 10-15C in 6 hours between 18-
00z. This will result in free falling temps into the 20s and 30s by
early evening and perhaps some teens in the Berkshires. Strong
shortwave passage with strong forcing along the front combined with
some instability should result in a few convective showers
accompanying the front. Boundary layer too warm for snow for most
areas, although could see brief snow showers develop in the
Berkshires and possibly northern Worcester hills as the cold air
pours in.
Strong wind gusts are the other feature with this frontal passage,
although an inversion below 850 mb at the time of the fropa may
prevent the gusts from being stronger than they otherwise would be
with a deeper mixed layer. Still, strong cold advection and pressure
rises should result in gusts 35-45 mph along and just behind the
front, strongest over the higher elevations where a brief 50 mph
gust can't be ruled out. The stronger gusts in eastern New Eng will
likely be delayed toward evening.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Key Messages:
* Very cold and blustery tonight with late night wind chills
dropping to zero to 5 above in the coastal plain and -5 to -10
over the higher elevations
Tonight...
The front will be offshore with strong cold advection resulting in
gusty WNW wind gusts to 35-45 mph in the evening before the
gustiness eases somewhat overnight. Clearing skies tonight as very
dry air moves into the region with PWATs dropping below 0.10" and
dewpoints falling through the single numbers to near or below zero
by morning. 925 mb temps bottom out at -16 to -18C around 12z Sun.
Lows will drop into the teens with single numbers higher elevations.
Wind chills late tonight and early Sunday will range from +5F to -10F
across the region.
Sunday...
Subsidence and very dry airmass will lead to abundant sunshine but
it will be cold and blustery. 925 mb temps recover to -12 to -14C so
highs will only be in the mid-upper 20s, with upper teens in the
higher elevations. NW winds gusting to 25 mph will add to the chill
with afternoon wind chills only recovering into the single numbers
and teens.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Key Messages:
* Brief return to a winter chill on Sunday, followed by a warming
trend with the warmest days Tuesday into possibly Thursday. Will
have cooling temperatures behind a midweek system, which may bring
widespread rain and gusty winds. Though, exact details are still
uncertain.
Big Picture:
An amplified mid-level trough is located across the eastern CONUS by
Sunday, which brings another burst of winter cold to the northeast
CONUS. This set up will be short-lived with the trough shifting east
and mid-level ridging builds in from the west, expect the northwest
flow to return to southwest, leading to a resurgence of mild air for
Tuesday through Thursday, and then trending cooler late next week.
Will have quiet conditions through Tuesday, come Wednesday and
Thursday we will watch the potential of widespread rain and gusty
winds.
Temperatures:
Sunday night into Monday morning still cold, lows in the single
digits and teens. Monday isn't too much warmer, perhaps by a
few degrees, upper 20s in the interior and low to middle 30s
near the coast. This will be followed by another chilly night in
the teens to low 20s.
Will have much warmer conditions Tuesday through Thursday, WAA
allows for 925mb temperatures to jump to near 0C on Tuesday, +8C to
+10C for both Wednesday and Thursday. Will say, Thursday could be a
wild card depending if the cold front arrives after max daytime
heating. As of now, the cold front passage looks to be later in the
day. This boils down to highs in the low to middle 40s on Tuesday,
then middle and upper 50s on Wednesday and Thursday. While a low
probability, 60F is not out of the question for eastern MA away from
the influence of the ocean and northern RI. In terms of nightly lows
those are on track to be above normal Tuesday and Wednesday night
with a return to colder temperatures Thursday night, following the
cold frontal passage.
Precipitation:
Dry weather prevails Sunday into Tuesday, next round of appreciable
precipitation is slated for Wednesday/Thursday. A bit of uncertainty
with the exact timing, stay tuned for those details, but this is a
large system, with a strong low pressure centered across the central
CONUS, out ahead there is a strong LLJ and will transport high PWATs
from the Gulf to the northeast. Forecast PWATs nearing 1.2" to 1.5"
which are 2-4 standard deviations above climatology. Viewing this on
the ensemble situational awareness table, between 12z Wed to 18z Thu
the PWATs are 97 to 99.5 percent of climatology. As this is 5-6 days
it is good to look at this through a probabilistically through DESI,
for 0.5" or greater from Wed to Fri morning are between 70 to 80
percent. When you increases to 1.0" or greater, drops 25 to 50
percent. Additionally, we can look at the 25th and 75th percentile
to give us a range of possibilities and shows where there is
uncertainty if the spread between the two is large. DESI 25th
percentile range is 0.4" to 0.6", while the 75th percentile ranges
1.0" to 1.3". As for any flooding concerns, the Ensemble River
Forecasts doesn't show any areas rivers reaching flood stage, though
will monitor this piece of guidance as we near the event.
Wind:
Fast forward to our next system, another aspect is the
potential for stronger gusts, as models show a robust LLJ with
the max of the jet around 850mb arriving late Wednesday evening
into early Thursday morning. Some agreement amongst guidance
winds aloft are 60 to 80 knots out of the south. Tough to say at
this point how much mixes down to the surface, but a good rule
of thumb during a strong low level inversion is we'd mix down
50% of the 925mb winds. Winds at 925mb across the interior range
30 to 50 knots, while along and east of the I-95 corridor are
50 to 70 knots. Could assume gusts up to 25 knots in the
interior and 35 knots by the coast is a good first assumption,
but given there are 5-6 days out there is pounds of time for
things to change.
&&
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF Update...
Today...High Confidence.
Mainly VFR with a few spot showers in the morning, then brief
showers this afternoon assocd with a strong cold front moving
into the region. May be cold enough for a few snow showers in
the Berkshires after the fropa. Gusty S-SW winds this morning,
up to 30 kt SE MA and Cape/Islands with LLWS, then wind shift
to WNW with fropa, 18-20z western half New Eng and 20-23z
eastern half. Wind gusts to 40 kt possible with the fropa
especially higher elevations, and 30-35 kt elsewhere.
Tonight...High confidence.
VFR. NW wind gusts 25-35 kt in the evening, possibly up to 40 kt
higher elevations, slowly diminishing after midnight.
Sunday...High confidence.
VFR. NW gusts to 25 kt in the morning, diminishing later in the
afternoon.
KBOS TAF...High confidence. Could be a few hours of marginal
LLWS conditions around 14z. S-SW gusts to 25 kt this morning
with wind shift to WNW around 22z with gusts to 30-35 kt.
KBDL TAF...High confidence. Gusty S winds this morning. Wind
shift to NW around 20z with gusts to 30 kt.
Outlook /Sunday Night through Wednesday/...
Sunday Night: VFR. Breezy.
Monday through Monday Night: VFR.
Tuesday: VFR. Breezy.
Tuesday Night: VFR. Breezy. Chance RA.
Wednesday: Windy with gusts up to 30 kt. RA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today through Sunday...High Confidence.
Increasing S winds this morning with gusts to 30 kt developing, then
a strong cold front will bring a wind shift to WNW later today and
this evening with near gale force gusts to 35 kt. Winds slowly
diminish Sun. Seas build to 8 ft over southern waters today with
rough seas over the waters into Sunday. The cold air moving over the
waters with strong winds and wave action will result in freezing
spray developing late tonight into Sunday. A freezing spray
advisory was issued for NE MA waters where areas of moderate
freezing spray is possible.
Outlook /Sunday Night through Wednesday/...
Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Freezing spray.
Monday through Monday Night: Winds less than 25 kt.
Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
Tuesday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain.
Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas. Chance of rain.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Gale Warning from 5 PM this afternoon to 1 AM EST Sunday for
ANZ230-250-251-254>256.
Small Craft Advisory until 1 PM EST Sunday for ANZ231>237.
Freezing Spray Advisory from 1 AM to 1 PM EST Sunday for
ANZ250-251.
&&
$$
SYNOPSIS...KJC
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...Dooley
AVIATION...KJC/Dooley
MARINE...KJC/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Mar 1, 6:56 AM EST----------------
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