Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 271752
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1252 PM EST Thu Feb 27 2020

.SYNOPSIS...
A low pressure system tracks through northern New England this
afternoon, bringing strong wind gusts and mainly dry conditions
to our area this afternoon. As low pressure lifts north into
eastern Canada, expect dry but cold and blustery conditions
tonight and through the weekend. Lake effect snow showers may
move across the northern Berkshires at times into the weekend.
Large high pressure will build across late Sunday into early
Monday, with temperatures moderating close to normal. Unsettled
conditions move in from later Monday through mid week with
milder temperatures.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

1250 PM Update...

A mix of clouds and sun this afternoon as low level
moisture/stratocumulus deck interacts with W/SW downslope wind.
A thin band of light showers passing thru RI/SE MA expected to
move offshore in the next hour or so. In far western
Franklin/Hampshire Counties have a low chance to slight chance
POP for some -SHSN making it into the east slopes of the
Berkshires. Otherwise dry conditions for the remainder of this
afternoon.

Strong 987 mb low center has tracked NE to south coastal Maine,
leaving our area in a tight pressure gradient and corresponding
strong W/SW flow. Surface winds have increased quite a bit over
the past hour or so, with highest wind gusts including 49 mph at
FMH and BED, 48 mph at MQE, 46 mph at BOS, and 56 mph at LWM.
Wind Advisory continues across all of SNE thru at least 8 pm.
The Wind Advisory for Nantucket, the Vineyard and Block Island
continues until 6 am Fri.


Early morning Discussion...

Rather potent mid level shortwave with negative tilt is lifting
NE from the mid Atlc coast. Strong forcing for ascent within
diffluent upper flow combined with low level convergence at the
nose of the low level jet is producing area of moderate to heavy
rain. Some convective elements noted given elevated instability
above the inversion and can`t rule out an isolated t-storm
through daybreak. This is a progressive system with cold front
already moving into NJ. Rain will exit between 7 am and 10 am
from SW to NE as the front sweeps through followed by wind shift
to SW. Rain ends in N central CT first, with Cape Ann to Cape
Cod the last to see the rain end. Total rainfall of 0.50 to 1
inch expected with locally higher amounts along favored upslope
areas along the east slopes of Berkshires and Worcester hills.

As low level jet lifts to the north, it strengthens into the
Gulf of Maine and clips Cape Ann around daybreak when a brief
surge of 40-50 mph easterly wind gusts are possible. Wind
advisory issued for Cape Ann until 9 am.

After the frontal passage and wind shift to SW/W, gusty winds
will develop within deepening and well mixed boundary layer.
Gusts 30-40 mph expected, but soundings support 40-50 mph gusts
over the Cape and especially the Islands. Will continue the wind
advisory there.

Expect partly sunny skies to develop this afternoon although
there will be BKN CU developing as cold pool aloft acts on low
level moisture. A few lake effect snow showers may spill into
the Berkshires. High temps will occur this morning, with temps
briefly reaching the lower 50s in eastern MA and 40s elsewhere
before falling temps this afternoon.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Tonight into Friday...

Low pressure in eastern Canada with strong pressure gradient
will maintain gusty west winds tonight which will slowly
diminish during Fri as gradient relaxes. We extended the wind
advisory through tonight for the Islands where gusts 40-50 mph
expected to continue. Elsewhere 25-35 mph gusts. Still gusty Fri
but diminishing by late in the day.

Expect partly cloudy skies tonight and partly to mostly sunny
Friday. Most cloud cover will be over the Berkshires where a few
lake effect snow showers are possible at times. In addition,
steep low level lapse rates over the ocean with W/SW trajectory
may lead to extra clouds and possibly a few flurries/snow
showers over Nantucket late tonight into early Fri. Ocean
induced Capes around 300 J/kg with delta T approaching 20C so
plenty of instability developing over the ocean.

Low temps tonight mostly in the 20s, with highs Fri in the 30s
to near 40 in the coastal plain.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Highlights...

* Expect dry conditions but cold temperatures lingering through
  this weekend as low pressure slowly exits eastern Canada

* Large high pressure builds slowly east Sunday night into
  early Monday as temperatures return to near normal levels

* Conditions will become unsettled starting late Monday through
  mid week as weather systems shift across the region in a
  developing west to southwest mid level steering flow

Details...

Friday night through Sunday...

While the low pressure center across eastern Quebec and the St
Lawrence Seaway, continue to see a dry but cold westerly flow in
place across the region as H85 temps at -15C to -20C linger.
West winds will remain gusty Friday night along the coast and
across the higher terrain, though should diminish somewhat
toward daybreak Saturday.

H5 cutoff low pres across eastern Canada will shift slowly E
through Saturday as winds shift to NW, keeping the cold temps
in place through the weekend. Expect highs to remain well below
normal, by as much as 10 to 15 degrees across the interior on
Saturday. Clouds will also linger across central and western
areas on Saturday, but should see more sunshine across the
region during Sunday as high pressure starts to slowly approach
from the W. Will also see winds diminish to around 5 to 10 mph.

Will see quite a bit of sunshine on Sunday as the large high
pressure ridge at the surface and aloft moves across NY state
and Quebec during the day. High temps will be a few degrees
milder, but will still run several degrees below normal. Expect
readings to range from the upper 20s to mid 30s across the
higher terrain to the mid and upper 30s along the coast.

Monday through Wednesday...

Noting a changing mid level steering flow across the lower 48
taking shape starting early next week. While broad ridging
crosses the northeast early Monday, a nearly zonal flow sets up
from the Appalachians to the central U.S., while a cutoff mid
level low digs off the southern CA coast. As the steering flow
evolves through mid week, noting steadily increasing H5 heights
across the region, another broad trough digs across the Great
Lakes which lingers SW to the cutoff low across NM and W TX late
Tue/Tue night.

The northern stream flow remains progressive, so will see
another short wave push across the region later Monday through
Tuesday. This will bring another shot of moisture across, so
will see periods of rain or showers for most areas as
temperatures increase to 5 to 10 degrees above normal by around
Tuesday. However, the moisture will linger each night, so could
see temps fall close to freezing across N central and W Mass.
May see some rain and/or snow as this system moves across Mon
night, but temps will recover on Tuesday so the precip should
change back to rain.

The region remains in the W-SW flow aloft, so may see another
system move along toward the northeast late Tuesday or
Wednesday. Confidence is rather low, however, as there is quite
a bit of model solution spread amongst the 00Z members. At this
point, have kept CHC POPs going with mild temperatures for
Wednesday.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

This afternoon...High confidence. Strong W/SW winds persist thru
this afternoon, with gusts 35 to 40 kts, locally higher gusts
possible. Winds should diminish somewhat towards 00Z. SCT-BKN
low VFR CIGs this afternoon.

Tonight...High confidence. VFR. W/SW gusts 25-35 kt with G40 kt
over MVY-ACK.

Friday...High confidence. VFR. W gusts 25-30 kt with 35 kt at
ACK, diminishing late.

KBOS Terminal...High confidence. VFR with brief BKN035 CIGs possible.
Strong WSW winds gusting to 40 kts, diminishing towards 00Z.
Gusts around 30 kts then continue through the overnight.

KBDL Terminal...High confidence. VFR with CIGs BKN035, becoming
SCT towards 00Z. Strong W winds gusting to 35-40 kt, diminishing
towards 00Z.

Outlook /Friday Night through Monday/...

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

Saturday through Sunday: VFR. Breezy.

Sunday Night: VFR.

Monday: Mainly VFR, with local MVFR possible. Slight chance RA.

&&

.MARINE...
This afternoon...Gale Warnings for all waters. SW/W winds
gusting 35-45 kt over the waters. Rough seas.

Tonight into Friday...
Gale force westerly winds continue with 35-40 kt gusts on the
open waters. Winds gradually diminish during Fri. Rough seas
continue.

Outlook /Friday Night through Monday/...

Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.

Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas.

Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft.

Sunday through Sunday Night: Winds less than 25 kt. Areas of
seas approaching 5 ft.

Monday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory until 8 PM EST this evening for CTZ002>004.
MA...Wind Advisory until 6 AM EST Friday for MAZ023-024.
     Wind Advisory until 8 PM EST this evening for MAZ002>022-026.
RI...Wind Advisory until 6 AM EST Friday for RIZ008.
     Wind Advisory until 8 PM EST this evening for RIZ001>007.
MARINE...Gale Warning until 7 PM EST Friday for ANZ232>235-237-254>256.
     Gale Warning until 1 AM EST Friday for ANZ230-236.
     Gale Warning until 10 AM EST Friday for ANZ231-250-251.

&&

$$
SYNOPSIS...KJC/EVT
NEAR TERM...KJC/EVT/NMB
SHORT TERM...KJC
LONG TERM...EVT
AVIATION...KJC/EVT/NMB
MARINE...KJC/EVT/NMB


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