NWS Boston/Norton, MA wrote its last area forecast discussion before the first event at Jan 23, 1:31 AM EST, 1 hour 29 minutes earlier.
Area forecast discussion, Jan 23, 1:31 AM EST, 1 hour 29 minutes before
Area Forecast Discussion
National Weather Service Boston/Norton MA
131 AM EST Mon Jan 23 2023
.SYNOPSIS...
A strong coastal storm impacts the region overnight through
Monday, with heavy rain, gusty winds, coastal flooding and
accumulating snow for northern Massachusetts, heaviest snow over
the high terrain of the Berkshires and northern Worcester
Hills. Drier Tuesday, but the active pattern continues as
another system moves in for late Wednesday into Thursday, with
more accumulating snow and mixed precipitation changing to rain.
Mainly dry and seasonably cold conditions follow for Friday
into next Saturday.
&&
.NEAR TERM /THROUGH TODAY/...
1:30 AM update...
Thru 12z/7 AM...
At 06z snow confined to northern MA along the VT/NH border,
with freezing rain south of this region into the I-90 corridor
and west of I-495. All rain across CT/RI and eastern MA.
Expecting the rain/snow/mixed precip line to remain nearly
unchanged thru 12z. Concern is across northwest MA into northern
Worcester county, where trees have snow and ice from previous
event, and reports of up to 3 inches of new wet snow as of 06z.
This combined with additional wet snow/freezing rain thru 12z,
will increase the risk of snow load issues (tree damage/power
outages). Thus, winter storm warnings will remain posted for
this area.
For the remainder of northern MA and west of I-495, freezing
rain with surface temps around freezing should minimize impacts
vs if temps were in the 20s. Nonetheless, untreated
roads/surfaces will be slick. Hence, winter weather advisories
remain posted for this region.
Farther southeast, across CT/RI and eastern MA, rain heavy at
times may yield minor poor drainage flooding, impacting the
morning commute. Large temp range at 06z, with coastal front
established across RI and southeast MA. Northerly winds and
temps in the 30s into the I-95 corridor and points northwest.
Southeast of I-95, warm sector with ESE winds and temps in the
40s.
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Previous discussion...
The mid level ridge axis has shifted east over Nova Scotia this
afternoon with heights beginning to fall and anomalous moisture
streaming northeast into southern New England. PWAT values, while
currently <0.5" will quickly increase to 0.75-1.00" by midnight.
This amount of moisture is in the 99th percentile of climatology for
late January and will be key in brining the soaking rains and
accumulating snows we expect over the next 24-30 hours. This plume
of moisture is stretching north ahead of a deep upper trough over
the MS Valley which has generated a surface low that will deepen off
the mid-Atlantic coast this evening and pass over Nantucket on
Monday morning. The track of this surface low and its reflection at
850 mb directly over southern New England will spell a mixed
precipitation event for us as a warm nose moves overhead on mild
southerly flow in the low levels. Thus, while we've got some light
snow showers over eastern MA at this hour, surface temperatures are
in the mid to upper 30s so no accumulation is expected before we
flip to rain toward 7 or 8 pm. This rain scenario will be the story
for everyone outside of the high elevations of the Berkshires and
Worcester hills, at least through mid morning on Monday. Best
chances of snow tonight forced by strong mid level WAA are in those
high elevations where marginal surface temperatures and isothermal
profiles will make for low snow-to-liquid ratios and a heavy, wet
snow. Thus, snow loading may be a bit of an issue for some trees.
Monday morning, though, the story changes with regard to that heavy,
wet snow as the snow ratios will rapidly increase from northwest to
southwest as much colder air surges in behind the exiting low on NW
flow. The arrival of this colder air means that 1)the character of
the snow will become drier and lighter and 2)rain will begin to
change over to snow for all of southern New England from NW to SE.
Timing of the changeover would be before noon generally NW of I-95
and from noon onward SE of I-95. Snowfall amounts have been
increased a bit since the overnight forecast package, especially for
the more southern and eastern areas where snow on the back end of
the system is looking more robust. Though temperatures will be
dropping into the 33-34F range in eastern MA initially, guidance
indicates the chance for some more moderate to heavy snowfall
potential with rates of 0.5-0.75"/hour possible which would help to
dynamically cool the column and allow for accumulation. Generally
thinking 5 to 9 inches in the northern Berkshires and northern
Worcester Hills with 2-4 inches in northern CT through northern RI
and northeast MA, and a few inches for southeast MA. However, we
can't rule out some isolated higher amounts; the HREFv3 indicates
decent potential for banded snowfall which if it sets up could cause
a localized bullseye. Snow tapers off from west to east from 5-9 pm.
The other facet of this system will be the breezy winds. However,
we're not expecting these winds to be of the magnitude that they
would be damaging given the displacement of the low level jet well
offshore and an initially inverted profile. The better chance for
gusty winds will be later Monday night in the cold advection pattern
when wind gusts of 25 to 35 mph will mix down. The N/NE winds early
in the day will also, together with very high astronomical tides,
contribute to widespread minor coastal flooding for northeast MA.
See the coastal flooding section for more details.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/...
The low lifts northeast into Nova Scotia overnight taking the
moisture and snow with it. By 9 pm all showers should have moved
offshore. Northwest winds will continue to be gusty but not
damaging. Beneath the colder post frontal airmass low temps will be
around 10 degrees colder than Sunday night, in the 20s.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
930 PM update...
Highlights...
* Dry and blustery Tue
* Another storm brings accumulating snow and mixed precip, changing
to rain late Wed into early Thu, along with the potential for
strong winds near the coast
* Mainly dry and seasonable Fri through next weekend
Tuesday...
Low amplitude trough swings through New Eng and will be accompanied
by some diurnal cloud cover assocd with the cold pool aloft. Other
than a few flurries or brief snow shower in the Berkshires, mainly
dry weather is expected. Highs will range from the mid 30s higher
terrain to lower 40s near the coast, but will feel cooler given
blustery west winds, gusting 25-35 mph at times and possibly up to
40 mph over the higher elevations.
Wednesday into Thursday...
Next southern stream system lifting NE from the southern Plains will
bring another precip event to SNE Wed afternoon into Wed night. High
pres to the north as initial surge of moisture moves in will provide
enough cold air at the onset for precip to begin as a period of
accumulating snow across much of the region. 850 mb temps -4 to -6C
Wed afternoon supports snow to start, even near the coast. However,
700 mb and 850 mb low track well to the west across the Lakes, which
will limit banding potential and result in warm nose advancing
northward across all SNE Wed night, along with a dry slot moving in
overnight. Rain-Snow line will advance north across the region Wed
night with an eventual changeover to rain from south to north.
Highest snow totals will be limited to interior northern MA and
probably under 6 inches, with minor accum possible in the coastal
plain from initial thump of snow before getting washed away. Precip
may linger into Thu morning as occlusion moves through, but trend
will be for drier conditions Thu afternoon as storm lifts to the
north and drier westerly flow develops.
The potential for strong winds will be a concern late Wed night into
early Thu as robust southerly low level jet develops across SE New
Eng. Guidance is indicating 70+ kt LLJ which is 3-4SD above normal
so potential exists for a period of strong to possibly damaging
winds across SE New Eng.
Friday into Sunday...
Looks mainly dry, blustery and seasonably cold Fri behind the
departing storm. Temps moderate Sat ahead of a cold front with low
risk for a few snow/rain showers in the interior. High pres builds
to the north Sunday but guidance is indicating potential for
overrunning precip ahead of a warm front sometime late Sun/Sun
night. Timing this far out is very uncertain so we followed NBM.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
0630z update...
Thru 12z...high confidence in trends, lower on exact timing of
details.
Widespread IFR/LIFR along with NNE winds 5-10 kt, except over
southeast MA where winds will be ESE. Rain for CT/RI and eastern
MA, freezing rain for northern MA, except snow along/near the
MA/VT/NH border.
After 12z...high confidence in trends, lower on exact timing of
details.
Rain/snow line at 12z located across northwest MA and the
MA/VT/NH border. Freezing rain possible across remainder of
western-central MA, with rain elsewhere. This rain/snow begins
to slide ESE to roughly BDL-ORH-LWM 15Z-16Z, then 17z-19z BOS-
PVD, then Cape & Islands 20z-22z. Roughly a 3 hour wind of
moderate to heavy snow will accompany the changeover from rain
to snow from west to east, with hourly snowfall rates up to an
inch per hour. NNE winds at 12z, shifting to NNW this afternoon
and becoming gusty. IFR/LIFR, then improving to MVFR across CT
into western-central MA around 21z and thereafter.
Monday night...high confidence on trends, lower on exact timing
of details.
Lingering SN over eastern MA, including Cape Cod and Islands at
00z, exits offshore around 03z. Trending upward to VFR. NW winds
15-25 kt, becoming west late.
Tuesday...high confidence.
VFR with west winds 15-25 kt. Possible MVFR cigs across the high
terrain of western MA.
KBOS TAF...High confidence in TAF.
KBDL TAF...High confidence in TAF.
Outlook /Tuesday Night through Friday/...
Tuesday Night: VFR. Windy with local gusts up to 30 kt.
Wednesday: Mainly VFR, with local MVFR possible. Breezy. Chance
SN.
Wednesday Night: Mainly IFR, with local MVFR possible. Strong
winds with gusts up to 45 kt. RA, SN, chance FZRA.
Thursday: Mainly VFR, with local IFR possible. Strong winds
with gusts up to 45 kt. Chance RA.
Thursday Night: Mainly VFR, with local MVFR possible. Windy
with gusts up to 35 kt.
Friday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High confidence.
A coastal low deepens as it lifts into southern waters late.
Rain across the region with increasing wind speeds/gusts. Winds
N/NE across portions of the S and E water at 20-30 kts. SE
waters are somewhat variable late as the low tracks over the
waters. Gusts increasing 20-35 kts late. Seas 2-4 ft for the
eastern waters and building 4-8 ft across the southern. Have
hoisted Gale Watches and Small Craft Advisories.
Monday...Moderate confidence.
Rain continues as the deep low lifts into the Gulf of Maine and
Nova Scotia. May see some snow spreading into western portions
of the waters late in the day as colder air filters in. Winds
shift to the N/NW at 15-30 kts. Winds gusting 25-40 kts. Seas
building 5-10 ft.
Monday night...High confidence.
Rain showers come to an end before midnight. NW winds 20-30 kt
gusting 25 to 35 kt. Seas 6-10 ft.
Outlook /Tuesday Night through Friday/...
Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.
Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas.
Wednesday: Winds less than 25 kt. Chance of rain, chance of
snow.
Wednesday Night: Moderate risk for gale force winds with gusts
up to 45 kt. Areas of rough seas. Rain. Areas of visibility
1 to 3 nm.
Thursday: Moderate risk for gale force winds with gusts up to
45 kt. Rough seas up to 13 ft. Chance of rain.
Thursday Night: Moderate risk for gale force winds with gusts
up to 40 kt. Rough seas up to 13 ft.
Friday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Areas of rough seas.
&&
.TIDES/COASTAL FLOODING...
* Minor coastal flooding possible midday Monday High Tide
We are watching the late Monday morning/early afternoon high
tide for widespread minor coastal flooding along the eastern MA
coast, Cape, and Nantucket. Astro tides are very high, only about 1
ft below flood stage for many locations. Surge guidance, including
Steven's institute indicates storm surge of up to 1 ft. Given
storm track is over/near Nantucket, best surge will be northward
from Plymouth county to the MA/NH border. Thus, will confine
coastal flood advisory to this region. Later shifts can adjust
southward if needed. Not expecting moderate flooding, as best
pressure falls and associated surge occur closer to 12z,
followed by pressure rises toward high tide at 17z. As for
coastal erosion, should be minor given wave action is only 4-7
ft and limited to one tide cycle.
Wed night/Thu morning...Coastal flood threat is marginal at this
time. The high tide of concern will be the early Thu morning (225
AM) tide which is 10.33 ft at Boston which is fairly low. Would need
about a 2 ft surge for minor flooding and this will depend on
getting a period of strong E/SE winds at high tide which is highly
uncertain. Winds will be shifting to S/SW by Thu morning.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory until 1 AM EST Tuesday for CTZ003-004.
MA...Winter Weather Advisory until 1 AM EST Tuesday for MAZ005>007-
009>016.
Winter Storm Warning until 1 AM EST Tuesday for MAZ002>004-008-
026.
Coastal Flood Advisory from 10 AM this morning to 2 PM EST
this afternoon for MAZ007-015-016-019.
RI...Winter Weather Advisory until 1 AM EST Tuesday for RIZ001.
MARINE...Small Craft Advisory from 4 AM early this morning to 7 AM EST
Tuesday for ANZ230>234-236.
Small Craft Advisory until 7 AM EST Tuesday for ANZ235-237-256.
Gale Warning from 4 AM early this morning to 7 AM EST Tuesday
for ANZ250-251-254-255.
&&
SYNOPSIS...KJC/BW
NEAR TERM...Nocera/BW
SHORT TERM...BW
LONG TERM...KJC
AVIATION...KJC/Nocera
MARINE...KJC/BW
TIDES/COASTAL FLOODING...Staff