Area Forecast Discussion Issued by NWS Boston, MA
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000
FXUS61 KBOX 131710
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
110 PM EDT Wed Mar 13 2024
.SYNOPSIS...
Dry weather persists today and Thursday with unseasonably mild
temperatures, but sea breezes on the immediate coast will keep
it much cooler in those locations. A more unsettled weather
pattern develops Friday into the weekend, with rainy conditions
for Fri and again on Sunday. Temperatures trend above normal
through this weekend, with a cooling trend toward more
seasonable temperatures by early next week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
10 AM Update...
After a cold start this morning with lows below freezing, sunny
skies and the mid march sun angle have allowed temperatures to
rebound nicely into the mid 40s already. Still expecting high
temps to top out in the mid to upper 50s this afternoon with a
solid chance at 60F for our typical warm sports in Hartford and
Bradley, and a low chance in Taunton and Norwood. With ocean
temps still in the 40s, A sea breeze will keep coastal
communities colder today in the upper 40s. The question is how
far inland will the sea breeze reach with very weak synoptic
flow.
310 AM Update...
* Plenty of sunshine today with some clouds arriving in the afternoon
* Highs mainly upper 50s/lower 60s but cooler immediate coast
The closed upper level low east of the Canadian Maritimes will
continue to move further east and away from the region today. This
will result in rising height fields as a mid level warm front
approaches. We still expect plenty of sunshine today...but do expect
an increase in mid/high level cloudiness by late in the day. Low
risk for a few brief sprinkles by evening...but boundary layer
is quite dry so do not expect much more than that.
850T warming to between +4C and +6C coupled with a relatively
dry airmass in pre-greenup should allow temps to overachieve a
bit. Thinking highs inland from the coast will be mainly in the
upper 50s to the lower 60s with perhaps even a few middle 60s in
the lower CT River Valley. Winds will be rather light too...so
quite a comfortable afternoon for mid March standards.
Meanwhile...weak pressure gradient will allow for sea breeze
development along the immediate coast. This should keep
afternoon temps in the upper 40s to the lower 50s in this
region.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Key Points...
* Light/Calm Winds tonight with lows mainly in the 30s
* Plenty of sun Thu with highs 60s to near 70...cooler coast
Details...
Tonight...
Some mid/high level cloudiness this evening in association with the
mid level warm front. We may even see a few brief
sprinkles...but given the dry boundary layer do not expect much
more than that. Otherwise...expect at least partial clearing
overnight with a ridge of high pressure taking control. Light to
calm winds will allow for overnight low temps mainly in the
30s...but a few upper 20s are possible in the normally coldest
outlying locations.
Thursday...
Upper level ridge axis approaches from the west. This will set the
stage for a beautiful Thursday across most of the region. Plenty of
sunshine expected with 925T climbing to between +9C and +12C inland
from the coast. Thinking temps likely overachieve a bit in pre-
greenup with highs mainly in the 60s inland from the coast. In
fact...a few locations in the Lower CT River Valley may hit 70. Weak
gradient though will allow for sea breezes along much of the
immediate coast...which will hold highs in the 50s in most of those
locales.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Highlights
* Unsettled Thu Night through Fri with rain showers. A few rumbles
of thunder cannot be ruled out along with embedded downpours.
* Dry on Sat with a mix of sun and clouds.
* Another frontal system swings through Sun bringing more showers.
Remains unsettled early next week, but shower activity may be more
spotty with more seasonable temps.
Thursday Night through Friday...
Stuck in quasi-zonal southwesterly flow during this timeframe. A
shortwave ridge over our region Thu Night will flatten out with a
shortwave trough lifting into New England from the central Great
Lakes into early Fri. Another trough digs into the Great Lakes/New
England late on Fri. A frontal boundary will be situated over our
region late Thu through Fri. An area of low pressure will ride along
this front pushing it through and bringing us rain showers.
Somewhat of an impressive shift in guidance from 24 hours ago with
this late week system. Latest suite trending further north with a
much more progressive system sliding through. Confidence still not
as high as would like it to be given this big shift over the last 12-
24 hrs, so have generally stuck with the NBM for now. However, did
dial back to slight chance/chance for now given there are still a
lot of differences in the timing, intensity and track of the low
riding along the front.
Does appear that there is potential for heavy rainfall, especially
with a frontal boundary parked over our area. The NAEFS/EPS
situational awareness tables still indicating PWATs of 2-2.5 STD
above model climatology, but still may generally be located more to
our SW. This is also indicated by the latest suite of deterministic
guidance and have decent agreement of a PWAT surge of roughly 0.75-1
inch. On top of this surge we have decent warm cloud layer depths of
2-2.5 km and perhaps up to 100 J/kg of MUCAPE. Given the environment
there could be some heavy downpours, especially with a perhaps a
SSW/SW 20-40 kt 925 hPa LLJ impinging on the region. Though will
note this is much different a solution, and further north, than
advertised than 24 hours ago. This shift can also be seen in the QPF
with now low to mod (10-40%) probs of 24 QPF AOA 0.5 inches with the
EPS/GEFS and GEPS guidance. The best shot for our CWA appears to be
along/north of the Route 2 corridor. Highest risk is across northern
New England with mod to high probs. At this point now essentially
have nil probs of 1+ inches of rainfall. Stay tuned as would like a
bit more run to run and model to model consistency before locking in
on how things evolve.
Still have signals that the stronger LLJ slides through and could
bring gusty winds. The NBM at this point appears reasonable, but
will be something else to keep an eye on as we get closer to Fri.
Nudged our temps down slightly on Fri from the NBM as it appears the
front may slide through as a backdoor cold front. For now am
advertising highs in the mid/upper 40s across northern and eastern
MA and the 50s elsewhere.
Saturday...
Stuck in cyclonic flow, but will have a shortwave ridge initially
over the central/eastern Great Lakes early on Sat. The ridge builds
into New England late on Sat, but flattens out a bit as it digs into
the Great Lakes region late in the day. High pressure nudges into
our region during this period.
Dry and quiet weather anticipated. However, given the trough digging
into Great Lakes will have a fair amount of cloudiness, especially
during the second half of the day. High temps range from the 40s to
the mid 50s.
Sunday into Tuesday...
Cyclonic flow persists through this period with a couple of troughs
sliding through. Really not certain on exactly how things will
evolve as guidance is a bit all over the place. Best shot for
showers comes on Sun as a frontal system pushes through. At this
point deterministic guidance painting Mon/Tue as dry, but given the
cyclonic flow think there could be some spotty shower activity.
Temperatures trending near to above normal.
&&
.AVIATION /18Z WEDNESDAY THROUGH SUNDAY/...
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Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Rest of Today...High Confidence.
VFR. Light and variable winds switching from northerly to
southerly. Sea breezes kick back out between 21-23z this
afternoon
Tonight...High Confidence.
VFR with light and variable winds.
Thursday...High Confidence.
Light NW winds across the interior with sea breezes developing
along the coast around 13-15Z.
KBOS TAF...High confidence in TAF.
Sea breeze kicks out between 21-23z and winds could turn SSW
briefly before turning light SSE overnight. Sea breeze develops
again tomorrow morning by 14z, but winds will already be SE.
KBDL TAF...High confidence in TAF.
VFR with light and variable winds.
Outlook /Thursday Night through Sunday/...
Thursday Night: VFR. Chance SHRA.
Friday: Mainly VFR, with local IFR possible. Chance SHRA,
isolated TSRA.
Friday Night: Mainly VFR, with local IFR possible. Chance SHRA.
Saturday: Mainly VFR, with local MVFR possible. Slight chance
SHRA.
Saturday Night: VFR. Breezy. Slight chance SHRA.
Sunday: Mainly VFR, with local MVFR possible. Breezy. 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 through Thursday...High Confidence.
Any lingering marginal 5 foot small craft seas across our eastern
waters will subside by daybreak. Otherwise...a weak pressure
gradient will keep winds/seas below small craft advisory thresholds
today through Thursday with good vsbys.
Outlook /Thursday Night through Sunday/...
Thursday Night: Winds less than 25 kt. Chance of rain showers.
Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers, isolated thunderstorms.
Friday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.
Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.
Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas up to 5 ft. Chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Frank/BL
NEAR TERM...Frank/KP
SHORT TERM...Frank
LONG TERM...BL
AVIATION...KP
MARINE...Frank/BL