BOX issues Area Forecast Discussion (AFD) at Jul 18, 11:19 AM EDT142
FXUS61 KBOX 181519
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1119 AM EDT Thu Jul 18 2024
.SYNOPSIS...
A cold front moves into southern New England today bringing lower
humidity away from the south coast. The front moves offshore tonight
with high pressure in control Friday through the weekend. This
brings seasonable temperatures and comfortable humidity levels.
Dry and pleasant weather this weekend. The pattern turns more
active again next week with increasing humidity.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1100 AM Update:
Cold front continues to slowly trudge southeastward, its current
position about near Buzzards Bay. Dewpoints were falling into
the middle 60s on the northwestern, cool side of this boundary
and while that is still a little humid it is far better than the
humidity levels we've seen the last several days. Lower to mid
70s dewpoints were still common over the Cape and Islands so
still quite humid there. Regional radar and satellite imagery
shows blossoming thunderstorms over the southeastern outer
waters southeast of ACK; while those could pose problems for
mariners, these should stay far enough southeast to not put any
land areas at risk for thunderstorms.
Front will probably be slower to egress eastward; while
dewpoints will be steadily falling into the lower 60s inland by
this afternoon, near the South Coast, Cape and Islands,
dewpoints in the mid 60s probably won't be observed until late
in the day or tonight. Otherwise a mix of sun and higher-level
clouds today (a few lower cloud decks for the Cape and Islands)
but dry weather prevails.
Previous discussion:
A cold front will slowly make its way across the region through the
day before stalling along the south coast. This means that relief
from the humidity won't arrive for most until later today, and
overnight for far southeast MA. We've still got dewpoints in the low
70s in northern MA and mid 70s in southern MA/RI at 3 AM. Drier air
will be filtering in on northwest flow today dropping those
dewpoints into the 50s for northwest MA by late morning/early
afternoon. That dry air finally pushes over the Cape and islands by
tonight. In the mean time, that moist airmass will be conducive to
scattered showers and even some thunderstorms along and off the
south coast this morning before pushing off by afternoon. Clouds
will become increasingly sparse through the day by the same token.
Temperatures will be warm but not as warm as days past, with cooler
air filtering in in the low and mid levels. Highs max out in the mid
to upper 80s.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
The real difference will be felt overnight as those lower dewpoints
allow for much cooler temperatures than we've felt recently, in the
50s and 60s. Friday is the pick of the week as high pressure moves
overhead and rising heights aloft allowing for clear skies, cooler
temperatures (upper 70s to mid 80s), and a much less humid airmass.
Dry and quiet weather to take us into the weekend.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
High pressure over the Great Lakes will extend eastward into SNE.
This will leave the region with dry and pleasant conditions through
Sunday. High temperatures slowly climb from the mid 80s on Friday
and Saturday to the upper 80s on Sunday. Dewpoints Friday start out
in the low 60s, but climb into the mid to upper 60s for Saturday and
Sunday. Global guidance does show roughly 100-300 J/kg of MUCAPE
will be available in western portions of SNE Saturday afternoon.
With a little bit of cyclonic vorticity aloft, this could lead to
some isolated low topped showers. Saturday will likely be the most
cloudy day of the weekend with a rather thick deck of cirrus clouds
aloft associated with the weak cyclonic vorticity impulse.
Next Week
A more active pattern looks to set in again for next week as deep SW
flow aloft kicks back in bringing increased moisture back and
several weak shortwaves towards SNE. Temperatures through the week
look to stay in the mid 80s, but dewpoints will be on the rise again
reaching the 70s by Tuesday staying there through the end of the
week. Timing these features this far out is difficult given the
spread in deterministic and ensemble guidance. Will need to monitor
trends in the coming days for severe convection with CSU ML probs
showing 5% severe on days 7 & 8.
&&
.AVIATION /15Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
15z TAF Update:
Today: High confidence.
VFR for the majority, but could be occasional MVFR bases over
the Cape and Islands thru 17z. NW winds around 10-12 kt with
occasional gusts to 20 kt in the interior and into the coastal
plain; wind shift from SW to WNW around 10 kt for the Cape and
Islands occurs later this afternoon.
Tonight...High confidence.
VFR. Light NW winds.
Friday and Friday night...High confidence.
VFR. Light W winds with onshore flow at coasts. Overnight winds
become west at all terminals.
KBOS TAF...High confidence in TAF. VFR through the period. NW
winds have developed around 10-12 kt and should continue that
way through tonight, though become NNW at around 10 kt late
tonight. Better chance at seabreeze Fri starting during the late
morning hours.
KBDL TAF...High confidence in TAF. VFR through the period. NW
winds around 8-10 kt today into Fri.
Outlook /Friday Night through Monday/...
Friday Night: VFR.
Saturday: VFR. Slight chance SHRA.
Saturday Night through Monday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through tonight: High confidence.
Winds diminishing, SW becoming NW then N Thu night behind the
front. Seas over south coastal waters will be 5-6 feet today,
diminishing overnight. Showers and a few t-storms continue
into the early afternoon, especially southern waters.
Friday: High confidence.
Winds 5-10 kts. Seas 2-4 feet.
Rip Currents...
A rip current statement is in effect into this evening along
south coastal beaches due to high risk for rip currents. Leftover
5-6 ft southerly swell will result in dangerous rip currents.
Outlook /Friday Night through Monday/...
Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents until 8 PM EDT this evening for MAZ020-
021-023-024.
RI...High Risk for Rip Currents until 8 PM EDT this evening for
RIZ006>008.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ235-
237.
Small Craft Advisory until 2 PM EDT Friday for ANZ254>256.
&&
$$
SYNOPSIS...BW/KP
NEAR TERM...Loconto/BW
SHORT TERM...BW
LONG TERM...KP
AVIATION...Loconto/BW/KP
MARINE...Loconto/BW/KP
Source:
BOX issues Area Forecast Discussion (AFD) at Jul 18, 11:19 AM EDT----------------
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