NWS Forecast Discussion
000
FXUS61 KBOX 191932
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
332 PM EDT Fri Apr 19 2024
.SYNOPSIS...
An approaching cold front will bring a period of showers and a
few downpours very late tonight into Saturday morning. Gradual
partial clearing and pleasant temperatures are in store for
later Saturday. Mostly clear skies and dry weather prevails
Sunday and Monday, although both days could feature low relative
humidities. Increasing clouds on Tuesday and Tuesday night
heralds a frontal passage and rain chances for Wednesday.
Conditions trend drier for late next week. Temperatures should
be around seasonable much of next week.
&&
.NEAR TERM /UNTIL MIDNIGHT TONIGHT/...
330PM UPDATE:
Ending the work week with enjoyable conditions, temperatures are in
the upper 50s and low 60s under a blend of sun and clouds. Clouds
thicken with additional mid and high clouds moving in from the west,
ahead of our next weather maker. Radar trends over the past hour
show a line of rain moving through New York, associated with an
approaching weak shortwave. As the rain moves east, it is running
into a drier airmass, high pressure over the Gulf of Maine. Should
see these radar trend weaken over the next couple of hours. Think
this evening is largely dry, but can not rule out a brief shower
reaching northern Connecticut or western Massachusetts.
Temperatures this evening gradually fall into the low 50s and upper
40s. Winds becoming more southerly around 10 MPH.
&&
.SHORT TERM /MIDNIGHT TONIGHT THROUGH SATURDAY NIGHT/...
330PM UPDATE:
During the overnight hours we continue to see increasing cloud cover
and dry conditions. The added cloud cover and wind direction more or
less out of the south keep temperatures a few degrees above normal,
in the middle 40s. Rain showers moving into the region well into the
overnight hours, do think these showers which are associated with a
cold front enter northern Connecticut/western Massachusetts between
3AM and 5AM, then eastern Massachusetts/Rhode Island between 6AM and
8AM. Should have improving conditions from northwest to southeast
from mid-morning to early-afternoon. QPF is in the neighborhood of a
quarter and third of an inch, enough to provide the region with a
wetting rain. The second-half of the day features mid-level dry air
mass, should reduce the cloud cover, giving us a mix of sun and
clouds. This should lead to a nice afternoon with highs in the low
and middle 60s. Low clouds will be stubborn for the Cape and Island,
but should clear our late afternoon, perhaps in time for sunset.
Here the highs are slightly cooler in the middle and upper 50s.
Guidance this afternoon does show the a trailing mid-level shortwave
that reaches southern New England mid to later afternoon. With this
passage, a couple of rouge showers are possible, but should come to
an end by sunset.
Overnight skies area clearing and despite s northwest wind at 10 to
15 mph, temperatures fall into the 30s. While much of the area
remains above freezing, northern Worcester County and the east
slopes of the Berkshires could see morning lows 30-34 degrees. May
want to keep that in mind if you bought any potted outdoor
plants.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
330PM UPDATE:
Highlights:
* Clear and dry weather Sun and Mon with seasonable temps. Possible
elevated fire weather concerns for both days, but especially Mon
as NW winds increase.
* Continued dry, but with SW breezes along with more cloud cover.
* Although not a soaking rain, a frontal system around Wed or Wed
night brings our next chance for rains.
* More uncertainty in the late-week pattern, but favoring dry
weather.
Details:
Sunday through Tuesday:
Cyclonic flow aloft begins this period, associated with a potent
shortwave disturbance which passes over northern New England into
Mon. System`s passing cold front moves through Mon too, but it will
be a dry frontal passage with a windshift to NW and cooler
temperatures being the only things really noticeable about the
frontal passage. Pattern starts to flatten Mon night into Tue with a
broad 1020+ mb high pressure cell ridging into Southern New England.
Dry weather to prevail in this period, even with the frontal passage
passing to the north on Mon. Much of this period features mostly
clear skies and though it will be a bit breezy from the northwest on
Monday, it should be a stretch of pretty nice weather on the whole.
But as is typically the case in the early-spring/pre-greenup period
with clear skies and good mixing leading to lower dewpoints, both
Sun and Mon could feature elevated fire weather concerns. Of the two
days, Mon looks to feature the lowest relative humidities and period
of stronger NW winds (gusts 25-30 mph). Highs Sun and Mon look
similar each day, in the 50s (upper 50s/near 60 in eastern MA). Lows
in the mid/upper 30s Sunday night and in the low to mid 30s Mon
night.
For Tue, high pressure shifts offshore early in the day, allowing
for returning SW flow bringing modest SW breezes, but also
increasing cloud cover (greatest late-day). RHs are a touch higher
(35-50 percent) Tuesday so not thinking period of fire weather for
Tue. Highs Tue should get to around 60 degrees. Turning mostly
cloudy on Tue night ahead of a frontal system for Wed, and the
increase in clouds brings milder nighttime lows in the 40s.
Wednesday:
12z ensembles and most deterministic models show a progressive
frontal system moving across Southern New England in this period.
There is some timing differences that still need to be sorted out,
with the ECMWF camp being slower with the progression (Wed late day
into early-overnight Thurs); those differences led to PoP being no
higher than Likely. A few days of dry weather preceding this frontal
passage could favor a slower timing (e.g. some of the modeled QPF
lost to evaporation through dry air layers) but won`t deviate
farther from NBM output to let the timing uncertainties iron
themselves out. This doesn`t look to be anything close to the
soaking rains that plagued us in March but we should be able to see
a period of wetting rains over a quarter-inch or so but not much
more.
Late Week:
A bit of uncertainty here with differences in mass field evolution
between the drier ECMWF/Canadian GEM and the GFS, which deepens an
upper trough which closes off into a closed low near or west of
Southern New England. That would bring unsettled weather and
cloudier conditions to the area. This solution doesn`t seem to have
much support from its ensemble; official forecast will keep close to
NBM for this period, but with a tilt towards the international
guidance favoring drier conditions.
&&
.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High- greater than 60 percent.
18z TAF Update...
Rest of Today...High confidence.
VFR. Increasing mid & high clouds this afternoon ahead of an
approaching front. East to southeast wind 10 to 15 knots,
occasional gusts to 20 knots. Wind direction does shift more to
the south later today and into the overnight hours.
Tonight...High confidence in trends, moderate confidence in the
exact timing.
VFR during the first-half of the night, but CIGs fall to MVFR
and localized IFR between 06z and 10z as -SHRA moves into the
region from west to east. In addition, visibilities are reduced
during the early morning hours with areas of rain 2 to 5 SM. It
is possible brief LIFR develops, though confidence is low at
this point and did leave that out of the 18z TAF. Later forecast
may want to include this if confidence increases. Veering
south/southeast winds becomes south/southwest and eventually
west across western terminals between 10z and 12z with the
passage of the front, winds are less than 10 knots.
Saturday...High confidence in trends, moderate confidence in the
exact timing.
IFR/MVFR to start, -SHRA continues for terminals in Rhode
Island and eastern Massachusetts through 15z/17z. May linger a
bit longer for the outer Cape and Islands. Winds are 8 to 12
knots and are generally from the west, though eastern
Massachusetts winds may remain out of the west/southwest.
Lastly, there is a low chance of a late afternoon pop-up shower
due to a trailing shortwave, this could produce widely
scattered rain.
Saturday Night...High confidence.
VFR, any lingering MVFR over the Cape and Islands become VFR
between 02z and 04z. Otherwise a dry night. Winds are 10 to 15
knots from the west/northwest. Perhaps some gusts for the Cape
and Island to 20 to 25 knots.
KBOS TAF...High Confidence in TAF.
KBDL TAF...High Confidence in TAF.
Outlook /Sunday through Wednesday/...
Sunday through Tuesday: VFR. Breezy.
Tuesday Night: VFR. Breezy. Slight chance SHRA.
Wednesday: Mainly VFR, with local IFR possible. Breezy. Chance
RA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
330PM UPDATE:
Today through Saturday Night...High Confidence.
Quiet conditions for the rest of Friday and tonight with seas
and winds below advisory criteria. An approaching front does
bring showers and perhaps a rumble of thunder Saturday morning
with a wind shift from ESE/WSW. Showers linger into late
Saturday morning/early afternoon. Drying out Saturday evening
into the overnight hours. Winds may briefly reach advisory
criteria late Saturday night 25 to 28 knots over the waters
south of Rhode Island and Block Island. Given how marginal this
is, held off on issuing a Small Craft Advisory. Later forecast
may want to include if confidence increases.
Outlook /Sunday through Wednesday/...
Sunday through Sunday Night: Winds less than 25 kt. Seas
locally approaching 5 ft.
Monday through Tuesday: Winds less than 25 kt.
Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas locally approaching 5 ft.
Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Chance of
rain.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Loconto/Dooley
NEAR TERM...Dooley
SHORT TERM...Dooley
LONG TERM...Loconto
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley
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