NWS Boston/Norton, MA wrote its last area forecast discussion before the first event at Feb 7, 10:17 AM EST, 1 hour 52 minutes earlier.
Area forecast discussion, Feb 7, 10:17 AM EST, 1 hour 52 minutes before
Area Forecast Discussion
National Weather Service Boston/Norton MA
1017 AM EST Fri Feb 7 2020
.SYNOPSIS...
Low pressure will intensify into a strong storm as it tracks
across New England today. This will bring another round of
mainly rain, changing to snow across interior Massachusetts
before ending later this evening. This storm will also result
in strong to damaging wind gusts this afternoon and evening.
Expecting dry and cold conditions to prevail Saturday as high
pressure builds across. Quick moving weather systems may bring
periods of light rain and/or snow at times from Sunday through
Thursday.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
10am update...
The surface low that will bring us strong winds later today is
currently centered over eastern PA at 978 mb. Thinking this
morning continues to be that it will track over CT and central
MA, placing southeast MA especially in position for very strong
winds. Hi-res guidance is holding steady with no major changes
in the placement of the highest winds. This morning's update did
drop temperatures several degrees as cold air has been slower to
scour out in northern MA and even further south. Hi-res
guidance has captured these cooler temps, though, and still
brings temps up into the low to mid 50s briefly this afternoon,
so don't think we'll have an issues tapping into the LLJ.
Previous Discussion...
Highlights...
* Period of strong to damaging wind gusts mid/late afternoon,
strongest near the south coast
* Rain changing to a period of snow mid/late afternoon in western
and interior northern MA before ending
Latest guidance continued to support the idea of a rapidly
strengthening low pressure move across interior southern New
England towards downeast Maine today. This track will be a
critical component to the forecast, as it exposes most of
southern New England to a very strong low level jet, some 3-4
standard deviations above climatology. Peak wind speeds in the
core of this low level jet are expected between 75-85 kt (85-95
mph) at 925 mb. So, how much of this wind will reach the
surface will all depend how efficient the mixing process within
the boundary layer can get, and how deep it will reach.
This is where some of the guidance is struggling a bit. Colder
air lingered across northern MA overnight. This colder air was
best represented within the near term high resolution guidance,
such as the 3 km NAM. This colder air near the surface will
delay the mixing process. Not quite convinced it will be enough
to prevent it completely. Given the strength of the low level
jet, it will not take much to tap into the stronger wind speeds.
Model soundings from the NAM, which tends to handle low level
cold air better, shows temperatures rising to near 50 degrees.
That might be a bit of a stretch, meaning a bit more of an
inversion lingers across northeast MA. Thinking a Wind Advisory
is pretty much a lock, but have some concerns about stronger
winds across Cape Ann this afternoon. Will need to monitor this
potential closely this morning. Should temperatures get higher
than current expectations, there could be significantly stronger
winds farther north along the east coast of MA. Did expand a
High Wind Warning into Plymouth County, where confidence is
higher. Also expanded a Wind Advisory into western Hampden
County.
Steadier precipitation will continue into this afternoon,
particularly across northern MA. As this low pressure deepens,
drier air should be pulled across much of CT and RI. Thus, most
of the precipitation there should be this morning. Based on
temperatures, cannot dismiss the possibility of some freezing
rain/drizzle this morning. Once this low pressure passes by,
temperatures should fall quickly, which opens the door for some
snow to develop across northwest MA late today. Thinking the
precipitation will be done farther southeast, before the colder
air can arrive.
With the threat of freezing rain continuing into this afternoon,
and some snow to boot, extended the Winter Weather Advisory
across portions of northern MA.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
As the powerful low pressure moves farther away from our region
tonight into Saturday, winds will diminish and drier conditions
will prevail, especially after midnight. Much colder air
overspreads southern New England tonight. Any untreated wet
surfaces will freeze with low temperatures in the teens and 20s.
A few spots could reach the single digits across the higher
terrain of NW MA.
Cold and dry conditions continue into Saturday as a high
pressure moves east across southern Canada. Below normal
temperatures expected, which has not been all that common this
winter.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Highlights...
* High pressure brings mainly dry but cold conditions Saturday
night into early Sunday
* Another fast moving low approaches Sunday night bringing
light snow that will change to rain Monday. The front will
stall south of the region Monday evening
* A few more weather systems will pass near or south of the
region Monday night through Tuesday night with a wintry mix or
snow inland changing to rain during the daylight hours
* May see a brief break on Wednesday with mainly dry
conditions, but it will become unsettled again Wed night into
Thu
Details...
With a continued nearly zonal, fast mid level steering flow
across the northern tier states through a good portion of the
long term, will see changeable conditions through this period.
Saturday night and Sunday...
Conditions will be mainly dry across the region Saturday night
into Sunday as a cold pool of air moves across. Light N-NW winds
will become light and variable Saturday night. While some high
clouds may linger across southern areas, skies should be mostly
clear mainly N of the Mass Pike. H85 temps will be coldest
across northern New England, on the order of -16C to -19C across
S NH and S VT, but it will still be chilly across our region
with readings from -11C to - 14C. So, temps will tumble Sat
night as they bottom out from the single digits to around 10
across the Route 2 area of N Mass to between 20 and 25 along the
S coast. Readings will run around 5 degrees below normal across
the interior, and closer to normal along the S coast.
As the high crosses northern New England early Sunday, another
weak low approaches from NE PA and SE NY. Clouds will increase
as light E- SE winds veer to S during the day. Rather dry
airmass across the region, but may see some spotty light snow
and/or rain move across most areas from around mid morning
through the afternoon. Have only carried slight chance POPs with
this weak feature. However, for now, have kept dry conditions
across most of eastern Mass into RI. Highs will only reach the
mid 20s to lower 30s well inland, ranging to the mid 30s to near
40 along the S coast.
Sunday night through Monday night...
Most of the 00Z model members continue to signal another low
moving across the Great Lakes with its associated front shifting
eastward out of the Ohio valley. Will see light snow develop
from NW-SE Sunday night, with the best chance occurring across N
central and W Mass where the QPF amounts reach 0.1 to 0.2
inches. It will remain somewhat drier further S and E, but will
still see some patchy light snow. Temps will fall back to the
mid 20s to around 30, except the lower 30s along the S coast.
A warm front lifts NE by Monday morning, as S winds increase to
10-15 mph during Monday, temps will rise with the light snow to
change over to rain by midday. Temps will rise to the 40s
regionwide.
Precip will taper off as the cold front moves across the region
Monday evening before stalling to the S. As the front stalls,
the northern edge of the precip may also remain across southern
areas. The temps will start to fall as colder air works in, so
could see a wintry mix mainly after midnight across portions of
N CT/RI into interior SE Mass with some patchy lingering light
snow further N. Expect lows in the mid 20s to mid 30s from N-S.
Tuesday through Thursday...
Models in pretty good agreement on Tuesday as low pressure
passes along the stalled front S of New England, so will see
mainly light rain away from the S coast, with QPF values from
0.1 to 0.2 inches, but could receive a bit more across portions
of Cape Cod and Nantucket. Cooler air may linger across the
higher terrain, so there could be a mix of light rain and/or
snow there.
Beyond Tuesday, model solutions diverge quite a bit through mid
week. Still noting a fast nearly zonal steering flow, so have
lowered confidence on the timing and track of individual weather
systems. At this point, may see precip linger into Tuesday
night before ending. On Wednesday, may be mainly dry, but can
not rule out spotty light rain and/or snow showers from time to
time. Big questions come into play with yet another possible
system affecting the region Wednesday night and Thursday.
Temperatures should be close to or a bit above normal levels
with the zonal flow in place during this timeframe.
&&
.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Today...High confidence in trends. Moderate confidence in timing
of precipitation type changes.
IFR-LIFR conditions this morning in areas of rain, drizzle and
fog which should improve to MVFR-VFR during the afternoon as
winds shift to W. Rain with pockets of freezing rain across
northern MA should change to a period of snow across western MA
this afternoon before ending. The main issue for this afternoon
will be very strong west wind gusts developing behind a
departing strong low pressure. Wind gusts of 40-50 kt will
develop after 20Z, especially south of the Pike. Gusts may
exceed 50 kt late today over Cape/Islands. LLWS is likely
across much of southern New England.
Tonight...Mainly VFR, with local MVFR possible early. Strong
gusty winds before midnight. Gusts up to 40 kt across the
interior, and up to 50 kt towards the Cape and islands.
Saturday...VFR. Gusty west winds up to 25 kt.
KBOS Terminal...High confidence overall. Lower confidence in
exact timing and details today. High confidence for Saturday.
KBDL Terminal...High confidence overall. Lower confidence in
exact timing and details today. High confidence for Saturday.
Outlook /Saturday Night through Tuesday/...
Saturday Night: VFR. Breezy.
Sunday: Mainly VFR, with areas MVFR possible. Slight chance SN.
Sunday Night: Mainly MVFR, with local IFR possible. Breezy.
Chance SN, chance RA.
Monday: Mainly MVFR, with local IFR possible. Breezy. Chance
RA.
Monday Night: Mainly MVFR, with areas VFR possible. Chance SN,
slight chance RA.
Tuesday: Mainly MVFR, with local IFR possible. Chance RA.
&&
.MARINE...
Short Term /through Saturday/...High confidence.
Expanded Storm Warnings across the outer coastal waters east of
Boston. Other Storm Warnings continue, except for a Gale
Warning in Boston Harbor. Expecting a surge to 45-55 kt westerly
wind gusts this afternoon and early evening as a strong low
pressure moves by. Seas building to 15-20 ft over southern
waters.
Gale force winds likely tonight into Saturday across the eastern
outer coastal waters of MA. Winds expected to diminish to Small
Craft Advisory levels Saturday elsewhere on the southern New
England coastal waters. Rough seas linger across the outer
coastal waters through Saturday.
Outlook /Saturday Night through Tuesday/...
Saturday Night: Winds less than 25 kt. Areas of rough seas.
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain.
Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Chance of rain.
Monday Night: Winds less than 25 kt. Areas of rough seas.
Chance of rain.
Tuesday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain.
&&
.EQUIPMENT...
KBOX WSR-88D radar had a transmitter failure early Thursday
morning. It will remain offline until further notice. It is
currently expected to be fixed later this afternoon or evening.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory until 10 PM EST this evening for CTZ002>004.
MA...High Wind Warning until 10 PM EST this evening for MAZ022>024.
High Wind Warning until 8 PM EST this evening for MAZ018>021.
Wind Advisory until 10 PM EST this evening for MAZ005>007-009-
011>017.
Winter Weather Advisory until 5 PM EST this afternoon for
MAZ002-008-026.
Winter Weather Advisory until 1 PM EST this afternoon for
MAZ003-004-009.
RI...High Wind Warning until 10 PM EST this evening for RIZ008.
High Wind Warning until 8 PM EST this evening for RIZ006-007.
Wind Advisory until 10 PM EST this evening for RIZ001>005.
MARINE...Storm Warning until 10 PM EST this evening for ANZ231-232-250-
251-254>256.
Storm Warning until 8 PM EST this evening for ANZ233>237.
Gale Warning until 1 AM EST Saturday for ANZ230.
&&
SYNOPSIS...Belk/EVT
NEAR TERM...Belk/BW
SHORT TERM...Belk
LONG TERM...EVT
AVIATION...Belk/EVT
MARINE...Belk/EVT
EQUIPMENT...