BOX issues Area Forecast Discussion (AFD) at Jun 20, 2:27 AM EDT
558
FXUS61 KBOX 200627
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
227 AM EDT Fri Jun 20 2025
.SYNOPSIS...
High heat and humidity today with strong to severe thunderstorms
possible this afternoon and evening. The best chance of severe
weather today is in interior Southern New England. Turning drier and
much less humid on Friday, but also quite windy by late June
standards. Seasonably warm temperatures are expected this weekend.
Monitoring for thunderstorm potential this weekend but the overall
risk is low. A multi-day stretch of significant heat is looking more
likely for Monday through Wednesday, with the potential for heat to
reach dangerous levels.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Key Messages:
* Heat Advisory in effect through 8PM with apparent temps near triple
digits
* Severe thunderstorm risk quickly wanes
Details:
Heat and Humidity...
A Heat Advisory remains in effect through 8 PM this evening. We've
already seen several hours of full sun today, and the temperatures
skyrocketed this morning in response. Expecting temperatures to
continue to warm into the lower to mid 90s, and with dewpoint
temperatures in the low to mid 70s, it may feel closer to the low
100s.
Remember to stay hydrated and limit strenuous outdoor activities
today. Take frequent breaks in locations with air conditioning and
wear light weight and light colored clothing.
Strong to Severe Thunderstorms This Afternoon...
The severe threat has quickly waned as earlier convection made
quick work of instability. As a result, the severe thunderstorm
watch has been cancelled.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/...
Key Messages:
* Sunny and slightly cooler Friday
* High winds likely during the day on Friday
Friday and Friday Night:
Clearing skies and lots of sun combine with a low-level jet around
40 kts and lead to the likelihood of quite high winds at the surface.
Thinking we could see areas of 30-45 mph with a few gusts near
50 mph in parts of western, central, and northeastern
Massachusetts and possibly go with a Wind Advisory for Friday.
Already went with a Gale Warning for Boston Harbor,
Massachusetts Bay, and Ipswich bay for the day. Wind speeds
should decrease more steadily into Friday evening.
We'll start to dry out a little bit for the start of the weekend
once the post-FROPA airmass moves in. Temperatures look to be in the
mid 80s across the interior and mid to upper 70s across the Cape and
Islands.&&
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Key Messages:
* More seasonable temperatures for the weekend behind cold front.
* Slight chance for showers and thunderstorms early Saturday but
coverage is in question.
* Multiple days of dangerous heat still expected through mid-week
next week. Air temperatures could rise as high as 100 degrees with
humidity making things feel even hotter. Greatest chance across
the interior, especially in river valleys and urban areas.
Little in the way of changes with regards to the evolution of the
upper-level pattern in the 3-7 day range. Heights are still expected
to build across the eastern CONUS as a trough deepens over the
western CONUS. This results in a strong ridge centered over the Ohio
Valley and Mid Atlantic. Ensemble guidance suggests that 500
millibar heights rise to as high as 597 dm by Tuesday. This setup
likely brings the hottest conditions of the season so far starting
Monday and lasting through Wednesday. Widespread 90's, and even a
few 100-degree readings will be likely across the region. Locally
hotter conditions are possible in river valleys where downslope flow
may warm things by a few degrees.
Saturday and Sunday:
The warm-up begins Saturday as heights start to build over the
region. Temperatures will be near to slightly above normal with
highs rising into the mid and upper 80s except across the Cape and
Islands where southwesterly flow will likely keep things a bit
cooler. High temperatures climb a bit more on Sunday, likely
reaching the upper 80s and lower 90s across the interior.
Outside of the increasing temperatures, there is a slight chance for
a few showers or thunderstorms earlier Saturday. A weak shortwave
moving around the periphery of the building ridge may bring a round
of showers and storms mainly across northwestern areas. At the
moment the risk is quite low as the storms will be battling rising
heights and limited surface instability.
Through Mid-Week:
Confidence in a significant heat event continues as guidance shows
near unanimous agreement in dangerously hot conditions. Heat starts
to build on Monday with ensemble guidance showing probs near 100
percent for high temperatures >90F across much of the interior. The
NBM suggests even hotter conditions on Tuesday with widespread 90-
95% probs of high temperatures exceeding 95F! A few spots in area
river valleys may approach 100 degrees with light westerly downslope
flow. The idea for widespread heat is further supported by 850mb
temperatures soaring to +22-24C Monday and Tuesday! This is an
impressive signal considering we are still more than 120 hours away
from the event. Some relief is possible Wednesday as low pressure
passing through the Canadian Maritimes swings a weak backdoor cold
front through the area. Guidance suggests than an onshore flow
develops by Wednesday afternoon. The onshore flow could bring a
relief from the hot weather, mainly for coastal areas and much of
eastern MA.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06Z TAF Update:
Through 12z Friday: High confidence.
Leftover IFR/LIFR over ACK should scatter to VFR, with but SCT-
BKN VFR elsewhere. A cold front will bring a windshift from S
around 5-10 kt to WSW/W and increase in speed to 10-15 kt with
gusts 20-30 kt, highest gusts closer to 12z Friday.
Today: High confidence.
VFR. Gusty westerly winds, with speeds 15-20 kt with gusts
35-40 kt thru 22z, then steadily decreasing to around 10-12 kt
with gusts low-mid 20s kt range toward sundown.
Tonight: High confidence.
VFR although with some increase in VFR-based clouds late.
Easing WNW winds to 5-10 kt.
Saturday: High confidence overall, but lower on rain/thunder
chances.
Mainly VFR. There are mixed signals if we see any showers or
perhaps a rumble or two of thunder during the second half of the
day for the southern airports (BDL-PVD-Cape area). Left any
SHRA/TS mention out of the TAFs for now but something we'll be
monitoring. W to SW winds around 5-10 kt.
KBOS Terminal...High confidence in TAF. VFR. Windshift from S
around 10 kt to WSW/W by 09-10z Fri at 10-15 kt with gusts 20-25
kt. W winds then increase more substantially around/after 14z
to around 15-20 kt/gusts 35-40 kt, which tend to ease after
20-22z.
KBDL Terminal...High confidence in TAF. VFR. Windshift from S
around 10 kt to WSW/W by 07-08z at 10-15 kt with gusts 20-25 kt.
Winds then increase more substantially after 13z to around 13-17
kt with gusts low 30s-kt range, which tend to ease 19-21z.
Outlook /Saturday Night through Tuesday/...
Saturday: VFR.
Saturday Night through Sunday: Mainly VFR, with areas MVFR
possible. Breezy. Slight chance SHRA, slight chance TSRA.
Sunday Night: VFR. Breezy.
Monday through Monday Night: VFR.
Tuesday:
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Small craft advisories have been expanded to all waters starting
this afternoon and were also extended into Friday. SW gusts
today should reach into the 25 kt range, although we expect
stronger gusts on Friday on all waters to around 30 kt. Gusts
could approach near gale force at times on Friday. Seas will
also be building today to around 3-5 ft, and then increase to
around 4-7 ft on Friday.
Because of the building seas and SW to W winds expected for
today and tonight, we've also hoisted a rip current statement
for today and Friday on south-facing beaches. It is somewhat
borderline today, but the threat for dangerous rip currents
should increase tonight and into Friday.
Outlook /Saturday Night through Tuesday/...
Saturday: Winds less than 25 kt.
Saturday Night: Winds less than 25 kt. Slight chance of rain
showers.
Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas locally approaching 5 ft. Slight chance of
rain showers.
Sunday Night through Tuesday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Wind Advisory from 8 AM this morning to 6 PM EDT this evening
for MAZ002>016-026.
High Risk for Rip Currents through this evening for MAZ020>024.
RI...High Risk for Rip Currents through this evening for RIZ006>008.
MARINE...Gale Warning until 8 PM EDT this evening for ANZ230-231-250-
251-254.
Small Craft Advisory until 8 PM EDT this evening for
ANZ232>237-255-256.
&&
$$
SYNOPSIS...Loconto
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Loconto
AVIATION...Loconto
MARINE...Loconto
Source: BOX issues Area Forecast Discussion (AFD) at Jun 20, 2:27 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202506200627-KBOX-FXUS61-AFDBOX)
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