Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 302352
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
652 PM EST Mon Jan 30 2023

.SYNOPSIS...
A weak cold front moves across the region tonight, accompanied by
scattered showers of rain and snow. Behind the front, mainly dry and
seasonably cold Tuesday through Thursday. Dangerously
cold airmass arrives late Friday into Saturday, with widespread
below zero temperatures expected by Saturday morning. Some ocean-
effect snow showers are possible across Cape Cod. Temperatures
rebound quickly Sunday.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
650 PM update...

Cold front moving into the Berkshires with area of post-frontal
snow showers focused across central and eastern NY. As the front
pushes E across SNE tonight, expect a few rain/snow showers
developing across the interior. Initially, ptype may be rain but
as the column cools rain showers will transition to snow
showers. Not expecting any snow accums given short duration of
snow showers and precip/qpf too light to overcome warm ground.
Low temps in the mid to upper 20s northwest of I-95, low to mid
30s elsewhere. Could be some slick spots late tonight into
Tuesday morning, NW of I-95 if any residual road moisture
lingers. SW winds this evening become NW overnight in the post
frontal airmass.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
4 PM update...

Tuesday...

Dry, post frontal airmass overspreads the region. Any leftover
morning clouds, gives way to partly to mostly sunny conditions
from late morning into the afternoon. Seasonably cold with highs
in the 30s. Chilly NNW wind 10-15 mph, but not too harsh by
late Jan standards.

Tuesday night...

1030 mb high advects into SNE. Thus, dry weather with
diminishing NNW wind. Very dry airmass, so potential for cold
temps, given light winds. However, models differ on cloud cover.
Therefore, did a 50/50 blend between NBM and colder MOS guidance
to derive mins. This yields lows in the teens for much of the
region.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Highlights...

* Seasonably cold and dry Wed into Thu
* High confidence in dangerously cold airmass late Fri into Sat
* Temperatures moderate quickly Sunday

Wednesday into Thursday...

Broad trough across the Gt Lakes and NE during this period. With low
amplitude pattern in place, coastal low expected to remain well
south of New Eng with as it tracks eastward from NC coast, so not
expecting any precip from this system. Generally cold and dry
conditions Wed as high pres builds in from the west. 850 mb temps
will be -13 to 15C Wed moderating to -6 to -8C Thu. Below normal
temps Wed with highs upper 20s to lower 30s moderating to upper 30s
Thu. Cold night Wed night as good radiational cooling conditions
develop with lows in the teens.

Friday into Saturday...

Polar vortex drops SE from Hudson Bay region and moves into the
Maritimes Fri night and will deliver pure arctic airmass to SNE.
Fortunately, with lack of high latitude downstream blocking it`s a
quick shot of arctic air, focused in the late Fri through Sat period
as heights will already start rising on Sat.

Timing of arctic front is somewhat uncertain as ECMWF about 6 hr
quicker than GFS/GGEM but this only impacts Thu night/Fri morning
temps regarding how quick the arctic air moves in. Even using the
somewhat slower timing, temps will be falling through the teens and
into single numbers Fri afternoon. It will be rather windy as well
Fri into Fri night in strong cold advection pattern with potential
for 35-45 mph gusts, peaking Fri afternoon/evening. Wind chills by
late Fri will already be down to zero to -20F. While winds diminish
somewhat late Fri night it will still be windy through the night
into Sat morning.

850 mb temps are forecast to drop to -30 to -35F which has multi
model and ensemble agreement. These 850 mb temps are about as
cold as you will ever see in SNE. In fact, these temps are
outside the model climatology for this time of year. ECMWF a bit
colder than GFS but the uncertainty lies in the timing of the
coldest air which may impact Sat temps. Regarding actual low
temps, we expect mins -5 to -15F across SNE with potential for
a few -20 readings over northern MA high terrain. These will be
the coldest air temps since Feb 14, 2016 when BOS and PVD
dropped to -9, ORH -16 and BDL -12. However, the bigger concern
will be the dangerously cold wind chills which are expected to
bottom out at -20 to -40 late Fri night into Sat morning, with
potential for wind chills as low as -45 in the Berkshires.
While we don`t have records of wind chills, discussion within
the office suggest these wind chills may be the coldest we`ve
seen here in 15-20 years!

Sat high temps will depend on how quickly the core of coldest air
moves out. We followed the NBM which has highs single numbers and
teens. It could be milder if the core of coldest air is quicker to
depart, and colder if it`s slower. Either way, still bitter cold Sat
afternoon with wind chills remaining below zero through the day.
Temps likely rise Sat night.

In addition, a period of ocean effect snow showers are possible over
portions of Cape Cod Fri night into Sat morning, but NW trajectory
should keep steadier snow offshore. Widespread moderate to heavy
freezing spray is expected over the waters.

Sunday into Monday...

Quick moderation is expected with temps Sun reaching mid 30s to
lower 40s. The warming trend may be accompanied by some rain/snow
showers Sun afternoon/night but this is uncertain given the model
spread. Mon looks dry and seasonable.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels:

Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.

00z update....

After 00z: high confidence.

VFR cloud bases with a period of MVFR cigs in scattered light
rain/snow showers from NW to SE overnight. SW winds this evening
shift to the NW overnight.

Tuesday: High confidence.

Any early MVFR cigs improve to VFR cloud bases late morning into
the afternoon. Dry weather with NNW winds 10-15 kt.

Tuesday night: High Confidence.

VFR cloud bases with diminishing NNW winds. Dry runways.

KBOS Terminal...High confidence in TAF. VFR cloud bases this
evening, then MVFR in scattered light rain/snow showers 05z-11z.
East wind late this afternoon, slowly shifting to SE, S and then
SW, NW after 06z.

KBDL Terminal...High confidence in TAF.

Outlook /Wednesday through Saturday/...

Wednesday through Wednesday Night: VFR.

Thursday: VFR. Breezy.

Thursday Night: VFR. Windy with local gusts up to 30 kt.

Friday: VFR. Strong winds with local gusts up to 40 kt.

Friday Night: VFR. Strong winds with gusts up to 40 kt.

Saturday: VFR. Windy with gusts up to 35 kt.

&&

.MARINE...
Forecaster Confidence Levels:

Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.

4 PM update...

Thru Tue night...

Tranquil weather by late Jan standards. SW winds this evening,
then a cold front sweeps across the waters overnight with a wind
shift to the NW. Scattered showers of rain and snow accompany
the front. Front moves offshore Tue, with NNW winds 10-15 kt
behind the front. Winds diminish Tue night as 1030 mb high
advects into New England.

Outlook /Wednesday through Saturday/...

Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft.

Wednesday Night: Winds less than 25 kt.

Thursday: Low risk for Small Craft Advisory winds with local
gusts up to 30 kt. Seas locally approaching 5 ft.

Thursday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Seas up to 5 ft.

Friday: Moderate risk for gale force winds with gusts up to
40 kt. Rough seas up to 10 ft. Freezing spray.

Friday Night: Moderate risk for gale force winds with gusts up
to 40 kt. Rough seas up to 10 ft. Freezing spray, chance of
snow showers.

Saturday: Low risk for gale force winds with gusts up to 40 kt.
Areas of rough seas. Freezing spray, slight chance of snow
showers.

&&

.CLIMATE...
Record Low Temps Sat Feb 4...

Boston-2 in 1886
Hartford    -8 in 1965
Providence  -2 in 1918
Worcester   -4 in 1934

Record Low Maximum Temps Sat Feb 4...

Boston      11 in 1886
Hartford    12 in 1996
Providence  13 in 1996
Worcester    8 in 1908

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...KJC/Nocera
NEAR TERM...KJC/Nocera
SHORT TERM...Nocera
LONG TERM...KJC
AVIATION...KJC/Nocera
MARINE...KJC/Nocera
CLIMATE...


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