NWS Forecast Discussion - Boston Area

Forecast Discussion for BOX NWS Office
000
FXUS61 KBOX 241108
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
708 AM EDT Wed Apr 24 2019

.SYNOPSIS...
Exiting cold front with low clouds and fog this morning
followed by mainly dry weather courtesy of high pressure through
Thursday. Showery and cooler weather returns Friday as low
pressure develops on an approaching frontal boundary. Periods of
heavy rain are possible late Friday into Friday night. Dry and
windy conditions develop Saturday behind the departing storm
system. A weak trough of low pressure may result in a few
showers Sunday into Sunday night but by no means a washout. Dry,
seasonable weather should return early next week

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...

7 AM update ...

As of 7 am showers exiting eastern Cape and Nantucket with
clouds already giving way to breaks of sunshine from coastal CT
into RI and southeast MA. Frontal boundary crossing the region
this morning with a wind shift to the WNW which will help erode
low clouds over northeast CT into the NW RI, the Worcester Hills
and northeast MA. Thus decreasing clouds/increasing sunshine as
the morning progresses.

Then some diurnal clouds expected with cold pool aloft along
with cyclonic flow. However more sun than clouds especially
across CT/RI and eastern MA.

Mild start to the day with temps already around 50 at sunrise.
Cooler post frontal airmass lags well behind the front so
expecting highs well into the 60s this afternoon to near 70
across RI and southeast MA. Gusty WNW winds of 15-25 mph will
even warm Cape Cod and the Islands given land trajectory wind.
Previous forecast handles this well so no major changes with
this update.


&&

.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM THURSDAY/...

Tonight ...

Chilly. With mostly clear conditions and light winds, anticipating
radiational cooling with temperatures falling close to dewpoints
that are observed during max-heating earlier in the day, in and
around 40 degrees (a blend of consensus and min-of-all forecast
guidance).

Thursday ...

Near-repeat of today. Renewed boundary layer mixing, mix-down of
drier air and westerly winds, albeit lighter. Highs around the
mid 60s with upper 60s possible over the CT River Valley. Warmer
interior conditions and light winds, forecasting a sea-breeze
during the latter-half of the day along the coast. Dewpoints
down into the upper 30s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...

Highlights...

* Fri/Fri night - threat for more heavy rain late Fri/Fri night
* Weekend - dry Saturday, few showers possible Sunday/Sun night
* Early Next Week - trends suggest dry/seasonable Monday

Thursday night ...

NAM only model offering a lead short wave with abundant moisture
moving across CT/RI and southeast MA Thu evening. All other guidance
including HREF at 48 hrs/00z Fri supports a dry forecast. So will
keep it dry most of the night and then introduce a low risk of
showers for western CT/MA as deeper moisture and lift from upstream
trough arrives.

Friday/Friday night ...

Forecast theme remains unchanged, potent northern stream trough
digging southeast thru the Great Lakes. Meanwhile moist southern
stream trough currently over the southern Plains becomes
captured/merges with upstream northern stream short wave to carve
out a negative tilt upper trough over New England Fri night. Timing
& phasing differences still exist but trough amplification combined
with PWATs up to 1.5 inches will result in a risk of heavy rain
possible late Fri into Fri night. Both NAM and GFS suggest over an
inch of qpf possible in 3 hrs in banded precip. ECMWF not as robust
but near an inch of qpf in 6 hrs. Showers will overspread the area
Fri however given trough amplification widespread rain may be
delayed until later in the day especially for RI and eastern MA.
Cooler Fri with developing ESE flow off the chilly ocean waters
ahead of approaching warm front.

Saturday ...

Depending on exact timing could be leftover showers early Sat
morning across RI and eastern MA as frontal boundary and wave exits
this region. Could be some embedded heavy showers in eastern MA
given negative tilt trough, anomalous deep layer moisture and
elevated instability. Post frontal airmass overspreads the region
later Sat morning and giving way to a dry afternoon although will
become breezy/windy as frontal wave deepens/intensifies as it moves
northeast away from the region. Seasonable with afternoon highs in
the upper 50s and lower 60s but will feel cooler given gusty NW
winds and dew pts falling thru the 30s and 20s.

Sunday ...

Low amplitude short wave trough moves across the region. By no means
a washout but there will be the risk for a few showers sometime
Sunday/Sun night. Seasonable temps before showers arrive with highs
in the upper 50s and lower 60s. Less wind than Saturday as well.

Early Next Week ...

Mixed signals here given time range but should see a period of dry
weather Monday behind departing short wave Sunday/Sun night.
Seasonable temps should continue with highs ranging from the upper
50s to lower 60s.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...

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

Short Term /through Thursday/...

11z update ...

Upward trend continues this morning with wind shift to the WNW.
Earlier discussion below. IFR/LIFR from northeast CT, northern
RI into central/eastern MA will lift/exit the area by 14z-15z
from west to east. Earlier discussion below.

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


Today through Thursday ...

SCT-BKN low-end VFR CIGs 3-4 kft with 2 kft MVFR possible over the
high terrain. Blustery W winds today 10 to 15 kts with gusts up
to 25 kts, diminishing overnight and continuing through Thursday
which will allow for sea-breezes during the latter-half of the day.

KBOS Terminal...High confidence.

KBDL Terminal...High confidence.

Outlook /Thursday Night through Sunday/...

Thursday Night: VFR. Chance SHRA.

Friday: MVFR/IFR conditions possible. Breezy. SHRA likely,
patchy BR.

Friday Night: Mainly MVFR, with local IFR possible. Breezy.
SHRA likely.

Saturday: Mainly VFR, with local MVFR possible. Windy with
gusts up to 30 kt. Chance SHRA.

Saturday Night: VFR. Breezy.

Sunday: Mainly VFR, with areas MVFR possible. Breezy. SHRA
likely.

&&

.MARINE...
Forecaster Confidence Levels...

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

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

Cold front sweeping the waters this morning behind which W winds
will be blustery with the threat of winds close to 25 kts
resulting in the continuation of Small Craft Advisory headlines,
especially over the S/SE outer waters with lingering S/SE swell.

High pressure building in, winds and seas diminishing beginning
tonight, headlines conclude towards midnight.

Outlook /Thursday Night through Sunday/...

Thursday Night: Winds less than 25 kt. Slight chance of rain
showers.

Friday: Winds less than 25 kt. Seas up to 5 ft. Rain showers
likely, patchy fog. Local visibility 1 to 3 nm.

Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas. Rain showers likely.
Local visibility 1 nm or less.

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

Saturday Night: Winds less than 25 kt. Local rough seas.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 2 AM EDT Thursday for ANZ254>256.

&&

$$
SYNOPSIS...Nocera/Sipprell
NEAR TERM...Nocera/Sipprell
SHORT TERM...Sipprell
LONG TERM...Nocera
AVIATION...Nocera/Sipprell
MARINE...Nocera/Sipprell

NWS BOX Office Area Forecast Discussion