NWS Forecast Discussion - Boston Area

Forecast Discussion for BOX NWS Office
FXUS61 KBOX 250908

Area Forecast Discussion
National Weather Service Boston/Norton MA
508 AM EDT Wed Apr 25 2018


Low pressure will push northeast from the mid Atlantic coast,
crossing the region today. 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 brief period of rain showers
likely Friday. A cool down will occur Saturday night and Sunday,
but this will be short lived as unseasonably warm temperatures
appear to be in store for the region by the middle of next week.



*** Locally heavy rainfall and isolated thunderstorms possible
 this afternoon and evening ***

Band of rainfall moving in across SW RI into CT and W Mass as
seen on NE regional 88D radar imagery at 08Z. Light rain
reported from KAQW-KIJD-KGON, with both legacy and dual pol
precip products reporting less than 0.1 inches. 08Z METARs
reporting T amounts in SW Mass and N CT, and up to 0.05 inches
at KPSF and 0.03 inches at KAQW.

Heavier bands of rain noted on radar across W NJ and just off
the Delmarva peninsula, heading N-NE. PWAT values of 1.2 to 1.3
inches will move across the region, which will produce bands of
heavy rainfall. Most model output, especially the high res ARW
and NMM guidance, all signaled locally heavy rain bands
developing by around 17Z-18Z mainly across E Mass into RI,
possibly as far W as Worcester county and NE CT. Could see some
heavier rain across N CT through midday, then pushing E during
the afternoon. The strong E-SE winds will also help feeding low
level moisture across the region.

Some locally heavy rainfall is possible across portions of
central and E Mass into RI and NE CT this afternoon and evening.
With the brief, heavy downpours, may see some street and poor
drainage flooding occurring. Will monitor this aspect very
closely. Noted that WPC has issued a marginal risk for local
flooding in any downpours. Will issue a Special Weather
Statement on this.

E-SE winds may briefly gust up to 30-35 kt especially across S
coastal Mass and RI this afternoon. Very strong low level jet,
on the order of 55-60 kt, passing across the region. However,
rather low lapse rates holds back the mixing from aloft. There
is a low risk for isolated thunderstorms in place with decent
instability in place. Noting LIs from zero to -1, K indices in
the lower 30s and TTs in the lower 50s. So, if any thunder does
occur, could see some gusty winds mix down in the convection.



Tonight and Thursday...

Low pressure will push across the region, heading to northern
New England by around 12Z-14Z Thursday. Will still see some
heavy rainfall across E Mass into E RI this evening, then will
push offshore by around midnight.

With a lot of low level moisture in place, along with SE winds
shifting to SW, will see low clouds and areas of fog lingering
through the night. The fog may reduce visibilities below 1/2
miles especially along S coastal areas. May see improving
conditions move into western areas around 09Z or so even with
lingering showers.

Drier air will start working across the region during Thursday.
A few showers may linger across N central and W Mass, mainly
across the E slopes of the Berkshires. Skies will become partly
to mostly sunny across most areas by midday or early afternoon
as winds shift to W. Temperatures should rebound to near normal
levels for late April.



* A 1-3 hour period of rain showers likely Fri

* Milder Sat with just a few brief afternoon/evening showers possible

* Dry and noticeably cooler Sun with frost potential late Sun night

* Dry weather Mon/Tue/Wed with a significant warming trend and the
  potential for 80+ in some locations by the middle of next week


Thursday night...

A ridge of high pressure will result in a dry/tranquil night.  Low
temperatures should bottom out in the upper 30s to the middle 40s in
most locales.


Shortwave trough remains to our west and it will eject a piece of
energy into our region on southwest flow aloft.  Appears there will
be enough forcing for a 1 to 3 hour period of rain showers sometime
Friday into early Friday evening.  Certainly not looking at a lot of
rain...but appears the likelihood that most locations do see a
brief period of rain showers.  Clouds and the likelihood of a brief
period of wet weather should hold high temps mainly in the
lower 60s.

Saturday and Saturday night...

A milder day is on tap for Saturday ahead of an approaching cold
front.  Southwest flow and partial sunshine should allow high
temperatures to recover well into the 60s to possible around 70 in a
few locales.  While dry weather should dominate...an approaching
cold front may trigger a few brief showers during the
afternoon/evening.  Greatest risk will be across western MA...where
forcing/moisture will be a bit deeper.  Turns cooler Sat night
behind the cold front.  Low temps by daybreak Sun should be down
into the upper 30s and lower 40s.

Sunday and Sunday night...

Deep trough sets up across the Northeast with anomalously low height
fields.  It will be noticeably cooler...but highs should still top
out well into the 50s with good mixing in northwest flow along with
the benefit of the increasing spring sun angle.  The dry airmass in
place will allow for chilly temps late Sun night into early Mon am.
Lows should bottom out in the upper 20s to the middle 30s in many
locations.  Frost headlines may eventually need to be considered
where the growing season has officially started.

Monday through Wednesday...

The northeast trough quickly moves east of the region Monday and
will be replaced by strong upper level ridging by the middle of next
week.  The result should be dry weather with a significant warmup.
High temps should recover into the lower to middle 60s
Mon...probably well into the 70s by Tue...and the potential for some
80 plus degree readings on Wed.  A weak pressure gradient will
likely allow for sea breezes and cooler conditions along the coast
at times.  Nonetheless...at least a taste of summer afternoon warmth
appears to be in the cards for much of the region.


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.

Through 12Z...Mainly VFR conditions, with some MVFR CIGS moving
into N CT and S RI by 11Z-12Z, along with patchy -RA.

Today...Conditions lowering to MVFR-IFR from SW-NE during the
morning. Rain will become steady with E-SE wind flow in place.
Areas of LIFR CIGS will push into NE CT/RI/SE Mass around
midday, and may reach further inland during the afternoon. Bands
of +RA developing across central and eastern areas this
afternoon. Isolated thunder late. Low risk for 35 kt gusts
across the south coastal terminals. Otherwise strong LLWS
through much of the day.

Tonight...IFR-LIFR conditions. Areas of +RA with heavy downpours
across E Mass/RI and isolated TSRA through around midnight, then
moving offshore. Low CIGS and areas of fog will linger across
the coastal plain much of the night.

Thursday...IFR CIGS/VSBYS early, then should improve to VFR
from SW-NE as winds shift to SW and diminish. May see gusts up
to 25 kt through midday. Rain showers end, though may linger
across N central and W Mass through the day.

KBOS Terminal...High confidence in TAF. Should remain VFR for
most of the morning push, then MVFR CIGS and -RA/RA should move
in by mid to late morning. Occasional +RA and IFR conditions by
the afternoon/evening push and E-SE wind will keep CIGS through
tonight. Low risk for TSRA from 21Z-04Z.

KBDL Terminal...High confidence in TAF. Morning push could be
impacted with brief +RA. IFR-LIFR conditions from mid morning
through tonight, and may linger into the early portion of the
Thursday morning push.

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

Thursday Night: VFR.

Friday and Friday night: A period of MVFR to localized IFR
conditions likely in a round of rain showers sometime Friday
into early Friday evening.

Saturday through Saturday Night: VFR. Breezy. Slight chance

Sunday: VFR. Breezy.


Forecaster Confidence Levels...

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

Short Term /through Thursday/...

Today through Tonight...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
1 to 3 nm today, locally below 1 nm at times across the southern
waters tonight.

Thursday...Moderate to high confidence.
Small craft conditions continue as winds shift to SW, though
winds diminish during the day. May see gusts up to 25 kt
through midday. Rain showers and visibility improves by around
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 Sunday/...Moderate to High

Thursday Night: Winds less than 25 kt. Areas of rough seas.

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

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

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

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

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


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.


MARINE...Small Craft Advisory from 2 PM this afternoon to 6 PM EDT
     Thursday for ANZ232.
     Small Craft Advisory from 11 AM this morning to 6 PM EDT
     Thursday for ANZ233-234-250.
     Small Craft Advisory from 4 PM this afternoon to 1 AM EDT
     Thursday for ANZ231.
     Small Craft Advisory from 2 PM this afternoon to 11 AM EDT
     Thursday for ANZ236.
     Small Craft Advisory until 6 PM EDT Thursday for ANZ235-237-
     Small Craft Advisory from 3 PM this afternoon to 6 PM EDT
     Thursday for ANZ251.
     Small Craft Advisory until 6 PM EDT Thursday for ANZ255-256.



NWS BOX Office Area Forecast Discussion