Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 220611
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
211 AM EDT Fri Mar 22 2019

.SYNOPSIS...
Intensifying low pressure off the New Jersey coast will bring a
steady rain to the region early this morning then becoming more
showery later this morning into the afternoon and windy late in the
day. Scattered showers will change to a period of snow tonight with
some accumulations expected in the high terrain along with winds
increasing and turning colder. The strong winds will continue into
Saturday, but it will be dry. It turns milder Sunday and Monday,
then a return to colder than normal conditions is expected Tuesday
into mid next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...

2 AM Update...

*** Periods of Moderate/Heavy Rain into Predawn Hours ***

Rain finally overspreading the region from south to north with
embedded moderate to heavy rain bands as low pres over southern
NJ continues to intensify. Approaching low level easterly jet
will result in a windswept rain overnight into predawn hours
along and near the coast. Previous forecast verifying nicely so
no major changes with this update. Earlier discussion below.

=================================================================

Potent storm system taking shape this evening over DE/NJ and
coastal waters with negative tilt closed mid level low inducing
cyclogenesis. Satellite imagery indicating an abundance of
lightning within the warm conveyor belt off DE/NJ coast with a
firehose of moisture off the Atlantic as PWATs increasing above
an inch, +2 standard deviations from climo. Dry air over
MA/RI/CT eventually erodes and gives way to rain overspreading
the region mainly after 11 pm. Initial rain band approaching
the south coast may erode as it encounters dry air over
CT/RI/MA, so expecting steady rains to arrive after 11 pm from
south to north.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/...

* Accumulating snow expected Friday night in the high terrain
* Windy later Friday and especially Friday night in all locales

Friday...

While the steady/heavy rain will be over by early Friday morning,
scattered showers are expected at times through the afternoon along
with rather cloudy skies. This a result of cyclonic flow around the
mid level closed low.  High temperatures should be in the 40s, so
ptype will mainly be in the form of rain showers.  However, it is
possible that it becomes marginally cold enough for some wet snow in
the high terrain along the east slopes of the Berks especially by
late in the day.

Friday night...

A second piece of vigorous shortwave energy will drop south of New
England Friday night.  The result will be an increase in areal
coverage/intensity of the precipitation.  Thermal profiles will be
cooling...so any rain will quickly flip to snow in the high terrain
and eventually even the lower elevations. In addition...strong winds
will develop as low pressure lifts into eastern Maine. Some
locations may be near wind advisory criteria, but given this is a
3rd and 4th period marginal event, opted to hold off on any wind
headlines at this point.

With that said though, the westerly flow coupled with deep
moisture/forcing will result in some enhanced upslope snowfall in
the Berkshires.  A few inches of snow seem likely in northwest MA,
but the highest terrain may see a swath of 4 to 8" above 1500 feet.
Will have to watch this region for a few power outages given the
snow coupled with gusty winds.  We may also see an area of 1 to 3
inches of snow across the higher terrain of the Worcester/CT Hills,
especially in the western Hills where upslope flow will result in
some enhancement. Elsewhere in the lower elevations...a dusting
to 1 inch of snow is certainly possible, but we can not rule
out the low risk of some location seeing 2 inches. Overall
though the main impacts appear to be in the high terrain and
especially in the Berkshires. Given that we have issued a Winter
Weather Advisory for western Franklin/western Hampshire county.
Snow amounts may vary quite a bit in this region too, highly
dependent on elevation.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...

Highlights...

 * Windy Saturday, then milder Sunday.
 * Cold front brings rain showers Monday, possibly starting as snow
   showers inland.
 * Colder weather follows through midweek.

Closed low exits New England this weekend as it heads into
Maritimes. Colder air aloft coupled with steep lapse rates will
promote diurnal clouds and gusty NW winds of 35-45 mph Saturday,
before skies clear and winds diminish Saturday night.

Milder weather arrives Sunday as upper flow becomes more zonal and
high pressure off Carolinas results in SW flow across region.
Blended guidance yields highs well into 50s away from colder ocean
influence (South Coast, Cape, and Islands) but with plenty of sun
it`s possible we reach lower 60s in some interior locations.

Ensembles in good agreement on timing of cold front through SNE
Monday which should reach South Coast around 18z before slowing down
a bit, as weak wave of low pressure may form along it as mid level
short wave approaches. Most of forcing and deeper moisture should be
located along and south of boundary, so while most of rainfall
(light) will be focused south of Mass Pike, we can`t rule out some
showers farther north as well. Should they occur it`s possible to
see some wet snow at start across NW MA where temperature profiles
support snow at least initially. Not looking for any real
accumulation at this point however.

Beyond Monday, broad upper trough remains in place for much of week
which will result in below average temperatures, at least through
Wednesday. High pressure will dominate with dry weather before
heading offshore later next week, so warmup appears more likely by
then.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

Short Term /through Saturday/...

06z update ...

Thru 12z ...

Conditions lowering to IFR/LIFR in periods of moderate to heavy
rain. Gusty ENE winds up to 30 kt along and near the coast.
Marginal LLWS 06z-09z with easterly low level jet moving across
RI and eastern MA.

After 12z ...

Steady rain transitions to showers. IFR/LIFR lifts to MVFR
during the afternoon. NE winds become NW in the afternoon.

Tonight ...

MVFR in rain showers changing to snow showers all terminals.
Snow accumulations ranging from a coating to an inch or two
possible, but 2-4 inches possible Worcester Hills into northeast
CT but potentially up to 4-8 inches east slopes of the
Berkshires. NW winds up to 40 kt, strongest wind across western
MA/CT.

KBOS terminal...Moderate to high confidence in TAF.

KBDL terminal...Moderate to high confidence in TAF.

Outlook /Saturday through Tuesday/...

Saturday: Mainly VFR, with local MVFR possible. Strong winds
with gusts up to 40 kt.

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

Sunday: VFR. Breezy.

Sunday Night: VFR. Slight chance SHRA, slight chance FZRA.

Monday: VFR. Chance SHRA.

Monday Night: VFR. Breezy. Slight chance SHRA, slight chance
SHSN.

Tuesday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance SHSN.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Saturday/...

Tonight...High confidence.
Intensifying easterly low level jet will bring a period of
easterly wind gusts of 25 to 35 knots from south to north. Seas
will build to between 5 and 9 feet across the open waters by
daybreak Friday with the long easterly fetch. Rain overspreads
the region and will be heavy at times overnight, reducing vsbys
for mariners at times.

Friday and Friday night...High confidence.
Winds will slacken for a time Friday morning as low pressure
tracks across the region. However, as the strong low lifts to
the northeast of our area the pressure gradient will increase.
Westerly winds will increase to between 35 and 45 knots later
Friday and especially Friday night. Gale Warnings are posted for
all coastal waters.

Outlook /Saturday Night through Tuesday/...

Saturday: Moderate risk for gale force winds with gusts up to
45 kt. Rough seas up to 15 ft.

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

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

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

Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Chance of rain showers.

Monday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.

Tuesday: Winds less than 25 kt. Areas of rough seas. Slight
chance of rain showers, slight chance of snow showers.

&&

.TIDES/COASTAL FLOODING...
The strongest winds/seas will arrive after the overnight high
tide. Therefore, worst case scenario appears to be some very
minor splash over during the 1 AM high tide.

The next high tide occurs early Friday afternoon, but by that
time winds will have diminished. Nonetheless, enough pressure
falls, lingering seas and relatively high astro tide will
likely result in pockets of splash over and minor coastal
flooding in the typically most vulnerable areas along the
eastern MA coast. We hoisted the Coastal Flood Advisory for the
eastern MA coast with the greatest risk along the north shore,
where winds will be slowest to slacken. Nonetheless, not
expecting any property damage or significant impacts anywhere
in our region.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Coastal Flood Advisory from 11 AM this morning to 3 PM EDT
     this afternoon for MAZ007-015-016-019.
     Winter Weather Advisory until 8 AM EDT Saturday for MAZ002-008.
RI...None.
MARINE...Gale Warning from 2 PM this afternoon to 4 PM EDT Saturday for
     ANZ232>235-237-254>256.
     Gale Warning from midnight tonight to 4 PM EDT Saturday for
     ANZ230-236.
     Gale Warning from 8 PM this evening to 4 PM EDT Saturday for
     ANZ231-250-251.

&&

$$
SYNOPSIS...Frank/JWD
NEAR TERM...Nocera
SHORT TERM...Frank
LONG TERM...JWD
AVIATION...Nocera/EVT/JWD
MARINE...Frank/JWD
TIDES/COASTAL FLOODING...



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