BOX issues Area Forecast Discussion (AFD) at Apr 14, 1:26 PM EDT877
FXUS61 KBOX 141726
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
126 PM EDT Mon Apr 14 2025
.SYNOPSIS...
High pressure builds over Southern New England today, bringing a
return to sunny weather and rather mild temperatures. A warm
front brings increased cloudiness and passing light showers
again for tonight. Then a rather strong upper level disturbance
brings unsettled conditions again for Tuesday afternoon.
Scattered pop- up showers likely for interior Southern New
England, some capable of lightning and perhaps some small hail
or graupel. Generally dry pattern by midweek with cool and
windy conditions Wednesday that slightly improve Thursday.
Temperatures continue to increase into Saturday. Rain chances
return Saturday with warm sector air settling over the region
before a cold front moves through Saturday night.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
330 AM Update:
Key Messages:
* Localized foggy areas in eastern MA disperses by sunrise.
* Sunny and warming up into the 60s, perhaps a few spot 70s?
* Cooler seabreezes near southern and eastern coasts.
Details:
The pesky, vertically-stacked circulation responsible for this
weekend's crummy and raw conditions is now finally escaping into
Georges Bank. Other than some straggling stratus over the Outer
Cape, most areas have gone mostly clear as weak sfc high
pressure ridge noses in. Good radiational cooling has developed
in most areas, which has done a couple things. First, it's led
to development of localized patches of fog, generally occurring
inside of eastern MA and portions of RI where temperature-
dewpoint spreads are the narrowest coming out of the weekend raw
conditions. Vsbys have been as low as a quarter mile in some
areas such as Bedford, but we felt the coverage was too sparse
to warrant any fog statements. Expect foggy areas to improve
shortly after sunrise. It's also partly contributed to a rather
wide range in temps, from the upper 20s in Orange MA to the low
to mid 40s Cape and Islands and most of the cities.
Shaping up to be a beautiful start to the workweek as ridging
both sfc and aloft crest over Southern New England. This will
supply us with plentiful sunshine and should favor quite a warm-
up to temps with good mixing and as winds turn toward the SW. A
stream of high clouds may arrive late in the day but the warm
frontal feature responsible for it won't arrive until later
tonight. The southern and eastern coasts do look like they will
develops seabreezes; although some of the latest high res
guidance, including the HRRR which often shows its development,
has started to back off on the eastern MA seabreeze. Highs
should soar into the 60s away from the coast and a few spot 70
degree readings are possible given mixing to 850 mb and 925 mb
temps warming to around +10 to +12C. Dewpoints should also mix
lower and support RHs in the mid 20s percent, but no fire
weather concerns are expected coming out of the damp weekend.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
330 AM Update:
Key Messages:
* Increasing clouds tonight, with light showers again possible after
midnight, but will be progressive.
* Early overcast Tue AM trends to partly/mostly cloudy conditions
Tue aftn. Afternoon hit-or-miss showers more likely west of I-495,
some could be capable of lightning and graupel/small hail?
* Highs mid 50s to lower-mid 60s Tue.
Details:
Tonight:
A warm front, which as of early Monday morning was located over
eastern OH and the western Appalachians will progress through
Southern New England tonight. This is associated with a rather
strong frontal system and upper trough over the upper Midwest.
Expect at least increased cloudiness to overcast again thru
midnight. There may be some showers associated with the warm front's
advance through Southern New England too, and offered Chance PoP for
those as guidance up until recently has been more bearish on the
coverage. Recent guidance has perked up some with respect to the
areal coverage, and later shifts may need to consider increasing
PoPs to reflect a better chance for rains pending trends in
guidance. Either way, it is progressive and not expected to be a
washout. Looking at a rather mild evening by early April measures
with lows falling only into the mid to upper 40s given overcast and
the warm sector moving in.
Tuesday:
The warm front from Mon night will be progressing offshore early
Tue. We'll likely start the day with overcast skies in most areas,
but we do expect some decrease in cloud cover to more of a partly
sunny to mostly cloudy look as we move into the afternoon. Highs in
the mid 50s to lower 60s.
The focus then turns to the afternoon, as the upper low now over the
Midwest moves to northwest NY by Tue aftn. This feature will bring a
combo of seasonably-strong mid to upper level winds/diffluence as
well as steep 850-500 mb lapse rates to around 7 to 8 C/km,
associated with a deep cold pool of air aloft. Majority of model
solutions show a rather generous coverage of at least scattered
convective showers, with convective-permitting NWP output showing
either individual cells or broken linear convective segments. Opted
for scattered aftn showers mainly for areas near and west of I-495,
but also made mention of isolated thunderstorms for that same area.
Will have to see if this activity makes it into eastern MA. BUFKIT
profiles show low-topped "cold-pool-aloft" type convective profiles
with equilibrium levels around 17k, well above the lightning
generation layer. A few strong cells could be capable of a few
lightning strikes as well as produce graupel or small sub-severe
hail given the lapse rates and strong mid/upper flow. The main
uncertainty that will dictate this potential is how much sfc heating
can we realize through continued partly/mostly cloudy skies; there
should some heating, but it doesn't seem like we'll fully clear. The
colder air aloft and diffluence aloft should offset that to an
extent, and there is some most-unstable CAPE (around 500 J/kg in
most bullish solutions, most are less than that). Activity should
dissipate shortly after sundown.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Key Messages:
* Cold front Tuesday night leaves cool and windy conditions in its
wake Wednesday
* Temperatures steadily increase heading into the weekend
* Precipitation chances return Saturday before possible clearing
Sunday
Details...
A cold front moves through the region Tuesday night going into
Wednesday, ushering in northwest flow and drier air. This is
expected to limit the chances for any precipitation for the week.
The cooler air aloft will mix down, along with gusty winds during
the day. Gusts to 30 mph could be possible in the afternoon hours
Highs Wednesday are only expected to be in the upper 40s to low 50s
across the region. Forecast soundings indicate a similar story for
Thursday, albeit a bit warmer due to less cloud cover and continued
diurnal mixing. Gusts of 25-30 mph will be possible Thursday as well.
Ridging builds in from the west as the trough responsible for the
unsettled weather earlier in the week (along with the colder
temperatures midweek) exits the region. As the ridge axis builds
over southern New England, temperatures will likely increase to the
low 60s. Winds will also diminish with the slackening of the
pressure gradient that will have been over the region since
Wednesday. With flow shifting more S to SW towards the afternoon
hours, it's possible some clouds may develop from moisture being
advected in.
A warm front moves over southern New England going into Saturday,
putting the warm sector over the region to start the weekend.
Guidance indicates Saturday being warmer than normal, with ensembles
having 925 hPa temperatures sitting around 15C for the mean; some of
the deterministic guidance has these values up to 20C. Aside from
the GEPS, which is running a bit warmer, other ensembles have around
a 50 percent probability of exceeding 15C at this level. Highs are
currently forecast at the mid to upper 60s with some spots around
70F. Cloudy and showery conditions throughout the day from continued
warm air and moisture advection may help limit temperatures from
getting much higher.
Following this airmass, a cold front is expected to move through
Saturday night into Sunday. A drier and colder airmass settles in
its wake. Clouds are cleared out of the region, winds shift
northwest, and temperatures aloft return to around 0C by Sunday
morning. Lows Saturday night sink back down to the low to mid
40s.
&&
.AVIATION /17Z MONDAY THROUGH FRIDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update: High confidence, then moderate confidence Tue.
VFR through early tonight before cigs lower to MVFR/IFR in
scattered showers overnight into Tue morning. Gradual
improvement back to VFR is expected Tue afternoon but with
continued risk of scattered showers. Still looking at potential
for some late afternoon thunderstorms with small hail,
especially in western/central MA and CT. Clearing Tue night.
Local sea breezes expected for a few hours late this afternoon,
otherwise winds back to S/SW through tonight with increasing SW
winds Tue gusting to 20-25kt at times. Winds shift to W/NW Tue
night with coastal airports gusting to 25-30kt toward daybreak
Wed.
KBOS TAF...High confidence, including sea breeze timing late
this afternoon. Expecting TS to remain west of airport late Tue
afternoon.
KBDL TAF...High confidence. Isolated TS possible 20z-23z Tue but
confidence is too low to include in TAF.
Outlook /Tuesday Night through Friday/...
Wednesday: VFR. Windy with gusts up to 30 kt.
Wednesday Night: VFR. Windy with areas of gusts up to 35 kt.
Thursday: VFR. Breezy.
Thursday Night: VFR.
Friday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Key Points:
* Period of W/NW Gales possible late Tue Night into Wed.
Strong cold advection behind next system later Tue night into
Wed most likely brings gusts of 25-30kt but possibly higher.
Issuing a Gale Watch for all waters for W/NW winds potentially
gusting to 35-40kt. Highest confidence is on waters around and
offshore of Cape Cod and the Islands but we cannot rule out 34kt
gusts elsewhere, including Boston Harbor and Narragansett Bay.
Outlook /Tuesday Night through Friday/...
Tuesday Night through Wednesday: Low risk for gale force winds
with gusts up to 35 kt. Areas of rough seas.
Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Local rough seas.
Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft.
Thursday Night through Friday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Gale Watch from late Tuesday night through Wednesday evening
for ANZ230>237-250-251-254>256.
Small Craft Advisory until 8 PM EDT this evening for ANZ250-
254.
&&
$$
SYNOPSIS...Loconto/Hrencecin
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Hrencecin
AVIATION...JWD
MARINE...JWD
Source:
BOX issues Area Forecast Discussion (AFD) at Apr 14, 1:26 PM EDT----------------
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