Area Forecast Discussion Issued by NWS Boston, MA
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000
FXUS61 KBOX 141734
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
134 PM EDT Thu Mar 14 2024
.SYNOPSIS...
Plenty of sunshine today with unseasonably mild highs in the 60s to
around 70 across much of the region...but it will be much cooler
along the immediate coast with onshore winds. Clouds increase this
evening with a period of rain showers after midnight into early
Friday morning along with much cooler high temperatures Friday.
&&
.NEAR TERM /UNTIL 11 PM THIS EVENING/...
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130 PM Update
Forecast remains on track this afternoon. No updates needed.
315 AM Update...
* Plenty of sun today with highs 60s to near 70...much cooler coast
Lingering sprinkles across the Cape/Islands exit the region before
daybreak. Otherwise...upper level ridge axis moves across our region
today. This will result in plenty of sunshine and unseasonably mild
temperatures away from the immediate coast. 925T moderate to between
+9C and +12C this afternoon...coupled with a rather dry airmass in
place in pre-greenup should allow temps to overachieve. Highs should
reach well into the 60s inland from the coast to near 70 in portions
of the Lower CT River Valley. However...weak pressure gradient will
allow for sea breezes and much cooler temperatures along the
immediate coast. Highs along the immediate coast will be held in the
upper 40s to the lower 50s.-- End Changed Discussion --
&&
.SHORT TERM /11 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Key Points...
* Period of showers overnight into early Fri AM
* Much cooler Fri with perhaps some drizzle and patchy fog
Details...
Tonight...
A shortwave and associated wave of low pressure approaches the
region from the west tonight. In response...clouds will increase
this evening. As the forcing for ascent increases...a period of rain
showers should overspread the region from the west generally after
midnight. The 850 mb low will be tracking across northern New
England. This will keep the heaviest rain to the north of our region
where better over running will setup. That being said...we do expect
a period of showers overnight into early Friday morning across most
of the region...especially north of the CT/MA border where better
forcing resides. Overnight low temps will be in the upper 30s to the
middle 40s.
Friday...
Surface wave of low pressure exits the region early Friday
morning...bringing an end to the bulk of the showers. However...this
will generate NNE winds and keep the region entrenched in a lot of
clouds. We may also see some patchy fog/drizzle especially across
eastern New England along with perhaps a few left over spot showers.
Temps on Friday will be quite a bit cooler than today! Pattern
recognition would suggest that the high resolution/cooler guidance
is the way to go with clouds and NNE winds. Highs probably remain in
the 40s across much of the region with perhaps lower to middle 50s
in parts of the Lower CT River Valley.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Highlights
* Spotty showers taper off late Fri into early Sat. Dry and quiet
weather on Sat with a mix of sun and clouds.
* A frontal system swings through Sun bringing scattered showers.
* Still may be unsettled on Mon and Tue, but with spotty activity.
Temps near to below normal.
* Drier weather returns midweek.
Friday Night into Saturday...
Stuck in cyclonic flow through this period. A shortwave trough will
lift from the central Great Lakes Fri Night into the Gulf of Maine
by early Sat. A shortwave ridge builds into the eastern Great
Lakes/western New England behind the trough. The ridge builds into
New England on Sat and offshore by late Sat. A frontal boundary
will initially be nearby/just south of southern New England Fri
Night. This slides further offshore, while high pressure begins
nudging in into early Sat. The high continues to nudge in on Sat.
There still may be spotty rain shower activity Fri Night into early
Sat, especially along/south of the south coast. Should be mostly dry
by early Sat and through the day Sat as high pressure nudges in.
Though given the cyclonic flow we will have a fair amount of
cloudiness. Should see warm air advecting into the region as flow
shifts from the NW to the SW as the day progresses. Will see 925 hPa
temps warm to 4-8 degrees Celsius. This will result in high temps
generally in the 50s, but the Cape/Islands will stay in the 40s.
Sunday...
Cyclonic flow persists through this timeframe. A trough lifts
into/through from the Great Lakes on Sun. A frontal system moves
through bringing scattered rain showers.
Will be our next opportunity after Fri for more shower activity. At
this point appears that this system will be pretty progressive and
we actually could see some breaks of sun late in the day. Really do
not have a whole lot of moisture to work with as PWATs range from
0.3-0.5 inches. This is roughly the 25th percentile to avg for this
time of year. Dialed back our precip chances a bit from the NBM as
it appears to be scattered activity quickly pushing through.
Only other potential impacts for Sun is that there is potential for
gusty winds. Though confidence is a bit lower here as guidance is
all over the place on the timing, intensity and exact placement of
the LLJ. Think that the risk is highest across the coastal plain
based on the current suite of guidance, but would like more of a
consensus. For now am advertising gusts of 20-30 mph through the day.
Monday through Wednesday...
Well as was the case for prior periods we will be caught under
cyclonic flow. A deeper trough digs into the eastern Great Lakes/Mid
Atlantic/Carolinas on Mon and through by Tue. May have a shortwave
ridge build into the Great Lakes for Wed. Still appears it could be
a bit unsettled through this timeframe.
Anticipate a fair amount of cloudiness through this period given 500
hPa temps cool to -25 to -40 degrees Celsius. This in combination
with diurnal heating should result in an ample amount of cloud
cover, especially during the day. The big question will be how much
moisture will we have available given the dry W to NW flow through
this timeframe. At this point PWATs are roughly -0.5 to -1.0 STD
below the typical values for this time of year per the NAEFS/EPS
situational awareness table. Given the setup have kept the NBM
slight chances as think isolated shower activity cannot be ruled
out. Temperatures trending near to below normal with the colder air
advecting in. Highs top out in the 40s.
&&
.AVIATION /18Z THURSDAY THROUGH MONDAY/...
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Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18Z TAF Update
Through 00Z...High Confidence
VFR. Light onshore winds near the coast and light/variable
across the interior.
Tonight...High Confidence in trends, moderate confidence in
timing.
VFR persists through about 03Z at most of the terminals. Conditions
then deteriorate overnight as an area of low-pressure
approaches from the west. Ceilings falling to MVFR levels across
the interior, except BAF/BDL may remain above MVFR with cigs
around 060 feet. Terminals near the coast likely to fall to
IFR/LIFR as southeast flow advects low/marine stratus over the
terminals. Low pressure system will be accompanied by -RA
beginning around 06Z at BAF/BDL and eventually reaching BOS by
08-09Z. Modest 5 to 10 knot southeast winds.
Tomorrow...Moderate Confidence
Surface low-pressure circulation exits to the east with -RA by
about 15Z. Low-level clouds continue to linger, but we should
see any LIFR ceilings improve to at least IFR by mid-morning.
Gradual improvements to MVFR by 18-21Z and eventually back to
VFR by 00Z. Not expecting any steady periods of precipitation
after 15Z tomorrow, but there may be a few spotty showers or
intermittent periods of light drizzle. Winds shift to the
northwest after 15Z once the surface low exits east. Speeds will
be modest topping out in the 10-15 knot range.
Tomorrow Night...High Confidence.
VFR. Steady northwest winds 5 to 10 knots. Possibly some MVFR
ceilings with cloud bases from 020 to 040 over The Cape/Islands
terminals.
KBOS TAF...Moderate confidence in TAF.
Conditions begin to deteriorate around 06Z. Only moderate
confidence in ceilings falling to LIFR levels with higher
confidence of at least IFR. Low ceilings likely to persist
through the morning push before some improvements after 15Z.
Could be back to MVFR levels by early afternoon, but likely
closer to 18Z. Improvements to VFR between 21-00Z tomorrow.
KBDL TAF...High confidence in TAF.
Outlook /Friday Night through Monday/...
Friday Night: Mainly VFR, with areas IFR possible.
Saturday: Mainly VFR, with local IFR possible.
Saturday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA.
Sunday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA.
Sunday Night through Monday: VFR. Breezy. Slight chance SHRA.-- End Changed Discussion --
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today and tonight...High Confidence.
A ridge of high pressure in control of our weather today will shift
east of the region tonight. This will keep winds/seas below small
craft thresholds through tonight. Showers will arrive after midnight
Friday...High Confidence.
Winds shift to the NNE across our northern waters Fri morning and
later across the southern waters. Speeds of 10 to 15 knots with a
few gusts into the lower 20 knots are expected. Kept things just
below small craft advisory thresholds for now.
Outlook /Friday Night through Monday/...
Friday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.
Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Chance of
rain showers.
Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas up to 5 ft. Chance of rain showers.
Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.
Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft. Slight chance of rain
showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Frank/BL
NEAR TERM...Frank/RM
SHORT TERM...Frank
LONG TERM...BL
AVIATION...Belk/RM
MARINE...Frank/BL