Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 260242
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1042 PM EDT Wed Apr 25 2018

.SYNOPSIS...
Low pressure will push northeast from the mid Atlantic coast,
crossing the region overnight. This will bring locally heavy
downpours may result in some brief poor drainage street flooding
and possibly an isolated thunderstorm or two. Seasonably mild
temperatures will follow for the remainder of the week with
mainly dry weather other than a period of showers Friday. A cool
down will occur Saturday night and Sunday, but this will be
short lived as unseasonably warm temperatures are in store for
the region by the middle of next week.

&&

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

1015 PM Update...

Area of SHRA/+SHRA moving across central and northern areas this
evening. May see an embedded brief thunderstorm as it moves N-NE
across NE and N central Mass through around midnight or so.
Noting another area of showers E of the central NJ coast on
latest NE regional 88D radar imagery. Spotty C/G lightning seen
with this areas, so could see isold thunder with this. As the
heavier showers shift NE, may see leftover light showers or even
drizzle with low level moisture in place.

Still noting some patchy dense fog along the RI S coast, though
visibilities have been between 1/4 and 1/2 mile. Also starting
to lower across S coastal Mass, will monitor this for possible
Dense Fog Advisories there.

S-SE winds have been diminishing, but still noting some gusts up
to 20-25 kt. Will continue to see downward trend as the low
level jet moves offshore.

Previous Discussion...

Convective showers with locally heavy rain continue to lift
north across eastern half of New England. Activity is located
along the nose of the low level jet. As the axis of the low
level jet shifts to the east, main focus for heavy rain will
gradually shift offshore after midnight. Main impact will be
localized nuisance poor drainage street flooding in areas of
heavy rain.

Another concern for tonight is dense fog as some mid level
drying moves in tonight while low levels remain saturated. Low
vsbys have developed over southern RI where we will issue a
dense fog advisory through tonight. Plenty of low level moisture
present and advisory may need to be expanded along the rest of
the south coast.

As the upper level low rotates through, the mid and upper
levels begin to saturated and there could be a redevelopment in
strong showers moving through SNE. Best timing is between 03Z
and 09Z as strong mid-level omega pushes through. The east
coast of MA has the best shot of seeing the strong downpours.
Still cannot rule out the thunder potential as RAP data has
several hundred joules of MUCape and Showalters dropping below
0C. Heavy rainfall will be the main threat as well as gusty
winds, especially along the passing cold front.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
Thursday...

Upper level low will begin to pivot out of the region during the day
on Thursday. Still some lingering moisture in the mid-levels with
steep lapse rates which will yield to sct showers in the morning.
Deep layer moisture will push northward towards Maine resulting in
low precip chances by the afternoon hours. Still expect sct to
broken clouds but overall trend will be dry by sunset.

Gusty WNW flow expected along as the mid level shortwave passes
through. Steep lapse rates and downsloping flow will result in good
mixing to near 850mb. Expect wind gusts to near 25-30 MPH by the
afternoon as highs reach into the mid to upper 60s. Overall a
pleasant Spring day.

&&

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

* A period of showers Fri afternoon/evening
* Scattered showers Sat, mainly interior
* Dry and cooler Sun then seasonably mild Mon
* Dry with a significant warming trend Tue/Wed

Friday...

Southern stream shortwave will be lifting northward into SNE during
the afternoon/evening. Shortwave is deamplifying but modest low
level jet and PWAT plume will bring a period of showers to much of
SNE, especially afternoon into early evening. There may be a focus
for brief heavy showers and an isold t-storm across RI and SE MA
where some elevated instability is present along the nose of the low
level jet. Highs will range from the upper 50s to lower 60s.

Saturday...

Next mid level shortwave and cold front approaches from the west.
This will lead to an increasing risk of sct showers, mainly across
central/western MA and northern CT during the afternoon. Otherwise,
expect pt-mosunny skies in the coastal plain with increasing
afternoon clouds in western New Eng. There is a low risk a few
showers could move into eastern New Eng Sat night as the front moves
through. With pre-frontal SW flow, milder temps expected Sat,
reaching mid 60s to near 70, except cooler along the south coast.

Sunday...

Cooler post-frontal airmass as deep trough settles over the
northeast and 850 mb temps cool to around -4C. Temps will remain
mostly in the 50s, with a few locations topping out near 60 in RI
and eastern MA. Chilly night Sun night with lows in the 30s but
close to 30 across the typical colder locations.  Frost headlines
may be needed where growing season has started, with greatest risk
across northern CT.

Monday through Wednesday...

A pattern change will occur next week as deep trough lifts out Mon
and is replaced by building heights and mid level ridging through
the middle of the week. Monday will be the transition day with
seasonably mild temps after a cold start to the day. Then warming
mid level temps will result in temps reaching into the 70s Tue with
potential for some lower 80s Wed. But SW flow will result in cooler
temps along the south coast.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...

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

Short Term /through Thursday/...Moderate to High confidence.

Overnight...IFR-LIFR conditions. Showers with locally heavy
rain through this evening and can`t rule out an isold t-storm
through 05Z across E Mass/RI/NE CT terminals. Low CIGS and
areas of fog will linger across the terminals much of the night.

Thursday...Improving conditions to VFR with mix of MVFR north of
the Pike during the day. Gusty westerly winds between 20-30 kts
by the afternoon.

KBOS Terminal...Moderate confidence in TAF. IFR conditions in
rain and lower ceilings through the evening push. Low risk for
TSRA through 05Z.

KBDL Terminal...Moderate confidence in TAF. IFR conditions in
rain and lower ceilings through the evening push. Dense fog is
possible during the overnight.

Outlook /Thursday Night through Monday/...Moderate to High

Thursday Night: VFR. Breezy.

Friday: MVFR/IFR conditions possible. Breezy. SHRA likely.

Friday Night: MVFR/IFR conditions possible. Breezy. Chance
SHRA.

Saturday: Mainly VFR, with local MVFR possible. Slight chance
SHRA.

Saturday Night: Mainly VFR, with local MVFR possible.

Sunday through Sunday Night: VFR. Breezy.

Monday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Thursday/...

Overnight...Moderate confidence. Small Craft Advisories for all
waters except Boston Harbor. Expect E-SE winds gusting up to 30
kt. Low risk for a few 35 knot gusts early in the evening
across the southeast waters. Rough seas up to 10 to 12 ft. Rain
showers, heavy at times along with areas of fog and isolated
thunderstorms. Visibility locally below 1 nm at times across the
southern waters.

Thursday...Moderate to high confidence.
Small craft conditions continue as winds shift to W, though
winds diminish during the day. May see gusts up to 25-30 kt
through midday. Seas remain at 5 feet or greater through the
day across the open waters as well as the south bays and sounds.

Outlook /Thursday Night through Monday/...Moderate to High

Thursday Night: Winds less than 25 kt. Rough seas up to 9 ft.

Friday: Winds less than 25 kt. Seas up to 5 ft. Rain showers
likely.

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

Saturday through Sunday Night: Winds less than 25 kt. Seas up
to 5 ft.

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

&&

.EQUIPMENT...
The NOAA Weather Radio transmitter serving Providence is out of
service due to phone line problems. The phone company has
prioritized the issues and is working to get the weather
broadcast back on the air as soon as possible. The transmitter
serving Hyannis is back in service.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...Dense Fog Advisory until 8 AM EDT Thursday for RIZ006>008.
MARINE...Small Craft Advisory until 8 PM EDT Thursday for ANZ232>234-
     251.
     Small Craft Advisory until 3 AM EDT Thursday for ANZ231.
     Small Craft Advisory until 11 AM EDT Thursday for ANZ236.
     Small Craft Advisory until 8 AM EDT Friday for ANZ235-237-250-
     254>256.

&&

$$
SYNOPSIS...KJC/Dunten
NEAR TERM...KJC/EVT
SHORT TERM...Dunten
LONG TERM...KJC
AVIATION...KJC/Dunten/EVT
MARINE...KJC/Dunten/EVT
EQUIPMENT...Staff


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