NWS Forecast Area Discussion - New England Area

000
FXUS61 KBOX 200157
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
957 PM EDT Fri Apr 19 2019

.SYNOPSIS...
A slow moving low pressure systems approaching from the west
will bring numerous showers with locally heavy rainfall later
tonight into Saturday night. The low pressure moves slowly
across New England into early next week. Off and on rain chances
through Wednesday, perhaps a drying trend for late week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
955 PM update ...

Scattered showers with brief downpours lifting north across SNE
this evening, but organized axis of heavy rainfall remains well
to the north and west along the boundary. Showers will increase
in coverage overnight across western MA and the CT valley as
convection along the mid Atlc coast lifts northward along the
axis of the increasing 850 mb jet. Given anomalous PWATs,
locally heavy rainfall is likely and can`t rule out a rumble of
thunder. Across eastern New Eng, just a few showers are possible
but much of the night will likely remain dry, especially SE New
Eng which remains on the periphery of the subtropical ridge.

Areas of fog developing along the south coast which should
become more widespread overnight near the coast. It will be a
warm and humid night for mid April with low temps 60-65, except
50s along the south coast.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Saturday...

Showers continue thru Saturday, as the very high precipitable water
plume 3-4 SD from normal continues to feed into our area thanks to a
deep and strong southerly flow. High amplitude trough containing
vertically stacked/closed low to our southwest, positioned over the
central Appalachians/lower Ohio Valley thru the day.

The axis of heavy rainfall will gradually shift from W to E
across our area over the course of the day. Including the
rainfall from Friday night, rainfall amounts of 1-2 inches with
locally higher amounts are expected in western to central MA
and northern CT, where a Flood Watch continues from late tonight
thru Saturday evening. To the east of the Flood Watch area,
somewhat less rain is expected, with 0.75 to 1.5 inches from Fri
night thru Sat.

Highs Sat 65-70, but a bit cooler immediate south coast.
Dewpoints will remain around 60 so continued humid feel for mid
April. South winds gusting 25 to 30 mph expected during the day.

Areas of fog, locally dense may linger into Saturday especially
along the south coast.

Saturday night...

The bands of rain shift towards the eastern half of the CWA as
the night wears on. Rainfall totals diminish, expecting a half
inch to inch over the Cape and Islands, and less to the west.
Rainfall should be more light over western MA/CT.

With the exiting jet, wind gusts will decrease quickly, leaving
light winds by daybreak Sunday. Temps fall into the low to mid
50s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
*/ Highlights ...

 - Sunday soaker E but seemingly pleasant W
 - Monday showers, potentially instability driven and heavy
 - Tuesday could be fairly warm, close to 80 for some
 - Remainder of the week appears seasonable and dry

*/ Overview ...

Rainy, cool pattern. Brief NW Atlantic rex-block will put the brakes
on the upstream pattern. Slowing our present storm system up against
a progressive N Pacific flow, onshore mild flow invokes increasing
heights across the CONUS, subsequently the present storm system cuts
off from the maritime flow, lingering into early next week. Moist
sub-tropical moisture neighboring, wrapping into the cut off closed
low, some initial breaks Sunday, especially W with a steady rain E,
evolves into a swirl of showers and winds, broken cloud decks, cool
conditions for Monday. Tuesday could turn out nice before additional
Pacific energy and continental-tropical airmass stretches out over
the NE CONUS along a weak cold front. Parallel wind fields to the
front, less frontogenetical lift / ascent, outcomes could be fairly
light, mainly confined to the high terrain. The remainder of the
week, seemingly on the W-cusp of a broader H5 trof over SE Canada
with indications of the maritime pattern being nudged N with the
Spring-time pattern, perhaps falling into a more seasonable and
dry pattern with prevailing W/NW flow.

*/ Details ...

Sunday ...

Soaker E as the W remains dry. Occluding front meandering E slowly
with accompanying sub-tropical precipitable water axis. Dry slot
wrapping it, the continued frontogenetical forcing E poses soaking
rains early for far E New England, especially SE MA, whereas cloud
decks becoming broken, perhaps scattered allowing abundant sunshine
and temperatures to warm up to around 70, more so if winds remain
light. Into evening and overnight, a renewed low pressure emerges
along the front, backing and stacking beneath the cut-off low which
is the main weather story for Monday.

Monday ...

Expect swirling light showers and winds beneath the cut off low from
the steering flow. Accompanying cooler mid-level temperatures aloft,
prefer the lower end of forecast guidance with 2m temperatures given
anticipated broken cloud decks. However this will invoke steep lapse
rates throughout the column. Potential breaks of sunshine, warming
up accordingly, could get instability-driven activity. 19.12z NAM
hints at the potential for soaking rains around peak heating midday
Monday. Thunder certainly possible. Keep with chance PoPs with a
slight chance of thunder mention.

Tuesday onward ...

Optimistic we`ll over-achieve on Tuesday to the point that we could
see some locations close to 80 degrees. This prior to a sweeping
weak cold front, some light showers mainly along the high terrain as
moisture is somewhat limited as is the forcing and ascent. Slight
chance PoPs. The remainder of the week seemingly is dry, seasonable
with cooler air holding firm aloft ushered by W/NW winds beneath the
W-periphery of a broader H5 trof over SE Canada.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

Short Term /through Saturday Night/...Moderate confidence.

Tonight and Saturday...
Mainly MVFR/IFR conditions with areas of LIFR fog along the
immediate S-coast tonight. -RA becoming widespread overnight
with embedded RA/+RA, mainly in western MA/CT overnight with
axis of showers shifting east across eastern half of SNE during
Saturday. Isolated TSRA also possible. Confidence with CIGs,
continued LLWS especially for the south coast and Cape/Islands,
but likely VSBYs will waver, intermittent at times.

Saturday night...
IFR/MVFR CIGS/VSBYS in patchy fog and showers. CIGS/VSBYS
gradually improve and showers become scattered as the night
progresses.

KBOS terminal...
SW winds subtly subsiding as IFR conditions work in the evening
hours. Expect -RA to move into the area into early morning prior
to which VCSH/DZ prevail.

KBDL terminal...
SW winds subtly subsiding as IFR conditions work in the evening
hours. Expect -RA to move into the area towards midnight prior
to which VCSH/DZ prevail.

Outlook /Sunday through Wednesday/...

Sunday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA.

Sunday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.

Monday: Mainly VFR, with areas MVFR possible. Chance SHRA,
slight chance TSRA.

Monday Night: VFR. Breezy. Chance SHRA.

Tuesday: Mainly VFR, with local MVFR possible. Chance SHRA.

Tuesday Night: Mainly VFR, with local MVFR possible. Breezy.
Chance SHRA.

Wednesday: Mainly VFR, with local MVFR possible. Breezy.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Saturday Night/...High confidence.

Tonight...

Persistent low level jet remains across the waters through Sat.
Gusts up to 35 knots nearshore until 10 pm, followed by gusts
up to 30 kt overnight and through Sat. After Gale Warnings
expire, Small craft Advisory conditions will prevail. Reduced
vsbys tonight in areas of fog which may be locally dense.
Showers developing overnight, with more showers and locally
heavy rain developing during Sat.

Saturday Night...winds diminish but rough seas continue,
especially on the outer coastal waters. Small Craft Advisory
conditions continue for most of the waters. Rain showers,
patchy fog. Visibility 1 to 3 nm.

Outlook /Sunday through Wednesday/...

Sunday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Rough seas up to 12 ft. Chance of rain showers.

Sunday Night: Winds less than 25 kt. Rough seas up to 10 ft.
Chance of rain showers.

Monday: Winds less than 25 kt. Rough seas up to 9 ft. Chance of
rain showers.

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

Tuesday through Tuesday Night: Winds less than 25 kt. Seas up
to 5 ft. Slight chance of rain showers.

Wednesday: Winds less than 25 kt. Seas up to 5 ft.

&&

.TIDES/COASTAL FLOODING...
A tidal departure up to 1 ft is expected along the south coast
through Sat. This evening`s high tide tonight is the higher
astronomical tide and areas of minor splashover will be possible
this evening along portions of the south coast, especially
Narragansett Bay and Buzzards Bay. Another round of minor
splashover is possible Saturday evening.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch from 2 AM EDT Saturday through Saturday evening
     for CTZ002>004.
MA...Flood Watch from 2 AM EDT Saturday through Saturday evening
     for MAZ002>004-008>012.
RI...None.
MARINE...Small Craft Advisory until 6 AM EDT Sunday for ANZ231-232-235-
     237-250-254>256.
     Small Craft Advisory until 2 AM EDT Sunday for ANZ233-234.
     Small Craft Advisory until 10 PM EDT Saturday for ANZ230-236-
     251.

&&

$$
SYNOPSIS...Sipprell/NMB
NEAR TERM...KJC/Sipprell/NMB
SHORT TERM...NMB
LONG TERM...Sipprell
AVIATION...Sipprell/NMB
MARINE...Sipprell/NMB
TIDES/COASTAL FLOODING...

NWS BOX Office Area Forecast Discussion