BOX issues Area Forecast Discussion (AFD) at Sep 5, 3:41 PM EDT426
FXUS61 KBOX 051941
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
341 PM EDT Thu Sep 5 2024
.SYNOPSIS...
Morning drizzle and fog will give way to a drying trend this
afternoon however an approaching cold front may bring a few strong
thunderstorms to western Massachusetts and Connecticut late this
afternoon and evening. Mainly dry and seasonable weather follows
Thursday, then unsettled weather with showers at times returns
Friday afternoon and night. High pressure provides dry and
seasonable weather Sat but the trend toward wet cool weather is
likely late Sunday into early next week as a coastal storm impacts
the area.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Highlights:
* Plenty of late afternoon sunshine with seasonably warm
temperatures
* Increasing low clouds and some drizzle, not out of the question
to have fog develop from the Merrimack Valley south through
the Blackstone Valley.
Hard to complain about an afternoon like today with highs
topping in the upper 70s and low 80s, plus dewpoints on either
side of 50F. No issues for the rest of the daylight hours and
first-half of tonight but there will be deteriorating conditions
late night into early Friday morning.
Surface high pressure shifts to the east overnight, while most
if not all of the night is dry, there are low chances for
drizzle. The wind direction has been out of the east/northeast,
this flow will usher in low-level moisture across the region.
Now, much of this moisture is trapped in the lowest levels,
beneath the mid-level high pressure. As this is compressed below
900mb we expect areas of low stratus and patchy drizzle after
midnight, but more likely 2am through daybreak.
Could see patchy fog develop from the Merrimack Valley south
through the Blackstone Valley tonight. While confidence isn't
high, would say there is moderate confidence in patchy fog to
develop near sun rise on Friday. Will need to monitor this
overnight.
With the added cloud cover tonight we will have "warmer"
overnight lows in the lower to upper 50s. Do think the urban
core of Boston will hold onto today's heating and likely have a
low near 60F. &&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Highlights:
* Coastal low pressure system brings low clouds, drizzle, and
beach hazards to the area on Friday.
* Breaks of sunshine occur late morning through the afternoon
from west to east.
A low pressure system will move north and northeast and passes
east of the bench by late Friday night. It is worth noting, NHC
does give this subtropical low a 30% chance of development over
the next 48 hours. We do not expect much in the way of impacts
from this system on land, but will have coastal impacts with
high surf and dangerous rip currents Friday and into Saturday.
Have opt to issue a High Surf Advisory for Cape Cod and
Nantucket for Friday and Saturday due to large waves and long
period swells, else where a Rip Current Statement for the high
risk of rip currents occurring. Making these hazards more
dangerous, many beaches are not staffed with life guards post
Labor Day Weekend. Those heading to area beaches this weekend
should take note whether or not a life guard is on duty.
Weather-wise, there remains chance for drizzle during the
first-half of Friday across eastern MA/RI. Stratus and any fog
will disperse with mixing of the boundary layer, should lead to
a mixture of sunshine by late morning for western MA and CT. The
lower clouds will hold on until early/mid afternoon in eastern
MA/RI. Where clouds may be the most stubborn are immediate
eastern coast of MA.
The onshore winds increase as the low pressure system moves
north, should have gusty northeast winds along the immediate
coast around 20 mph. Do expect these winds to linger into the
overnight hours as well. Breezy winds keep the immediate coast
cooler with highs in the lower 70s. Inland and away from the
influences of the ocean temperatures should return to the upper
70s to 80F.
Overnight the low pressure system races north towards Nova
Scotia, but winds remain from the northeast and reinforces the
risk for stratus across southern New England. Do think the night
is dry, if there were any spot showers likely to be found in
eastern most MA, being Cape Ann to Cape Cod. Another mild
overnight with lows in the middle 50s to lower 60s.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Highlights...
* Mild days and cool nights Thursday night thru Saturday
* Showers possible Fri afternoon and night then dry Saturday
* Coastal Storm brings a chilly rain late Sun into early next week
Synoptic Overview...
Emerging omega block pattern over Canada reloads the trough over the
Great Lakes and Northeast this period yielding an active pattern
along with temperatures at or cooler than normal at times.
Daily details...
Thursday night...
Any evening showers come to an end as potent short wave trough exits
eastward and offshore. Drier post frontal airmass overspreads the
region on westerly low level winds. Temps fall into the upper 40s
and lower 50s overnight, which is right on track for this time of
year.
Friday...
Models differ on depth of moisture rotating around mid level closed
low over southern Quebec into New England. ECMWF has trended drier.
Will continue with chance pops to reflect chances for scattered
showers. By no means a washout but be ready to dodge a few nuisance
type showers Fri afternoon and evening. Cool airmass in place over
the region with 925 temp anomalies around -1 standard deviation from
climo. Given increasing clouds are likely Fri temps likely fall
short of full potential with highs in the upper 60s and low 70s.
Saturday...
Next potent short wave moving across the region during the morning.
Thus risk of showers early but trending drier during the afternoon
along with some breaks of sunshine. Highs in the upper 60s and low
70s.
Sunday...
Good model agreement on next approaching short wave with parent low
over the Great Lakes entering PA late Sunday then redeveloping south
of Long Island toward Mon morning. So Sunday looks to start dry but
finishes wet. Much cooler given dry airmass initially then wet
bulbing once rain arrives late. Highs in the 60s but then falling
into the 50s late once rain arrives.
Early next week...
Upper trough over the Eastern Great Lakes induces one or more
surface waves tracking near or along our south coast. This will keep
the threat for periods of rain along with very cool weather with
northeast winds Mon and Tue.
&&
.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
This Afternoon and Tonight...High confidence through 06z,
moderate confidence afterwards.
VFR then areas of MVFR and IFR stratus developing 06Z to 10z
with patchy drizzle possible. East to northeast winds up to 10
knots along the coast, with light and variable wind across the
interior. Cape Cod and Islands remain VFR during this period.
May have areas of patchy fog develop between KBED to KORH to
KPVD.
Tomorrow...Moderate confidence.
MVFR-IFR ceilings in the morning with patchy drizzle possible,
improving to VFR in the afternoon. East to Northeast wind 8 to
15 knots.
Tomorrow Night...Moderate confidence.
Widespread MVFR ceilings, lowering to IFR. Northeast winds near
the coast 10 to 15 knots, light from the northeast across the
interior.
KBOS TAF...Moderate confidence in TAF.
VFR through 10z, quickly lowering to MVFR/IFR shortly after,
have the prevailing cloud base as MVFR, though there will be a
tight gradient of IFR ceilings around the terminal, have opt to
use a SCT IFR group to signal this threat. May scatter out to a
low end VFR ceiling around 16z to 18z. East to Northeast winds
throughout the TAF period.
KBDL TAF...High confidence in TAF.
VFR, then MVFR stratus possibly moving in early Friday around
10z to 13z, lifting to lower end VFR, BKN040 by 14z to 15z.
Light wind from the North/Northeast.
Outlook /Saturday through Tuesday/...
Saturday: Mainly VFR, with local IFR possible. Chance SHRA.
Saturday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.
Sunday through Tuesday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Friday Night...High confidence.
Intensifying low pressures system off the coast of the Carolinas
will track to the north/northeast tonight, passing east of the bench
mark by late Friday night, then reaching Nova Scotia as a strong
gale by Saturday morning.
Have extended the Small Craft Advisory for all the outer waters and
Massachusetts Bay through Saturday afternoon for large waves of 5 to
9 feet, but could approach 10 feet southeast of Nantucket. Seas may
remain elevated into Sunday, which may prolong the advisory.
Northeast winds are 20 to 25 knots on the outermost waters, less
near shore.
Opt'd to issue a High Surf Advisory for Cape Cod and Nantucket for
Friday and Saturday due to large waves of 7 to 9 feet and long
period swells of 9 to 10 second. Else where a Rip Current Statement
for the high risk of rip currents occurring. Making these hazards
more dangerous, many beaches are not staffed with life guards post
Labor Day Weekend. Those heading to area beaches this weekend should
take note whether or not a life guard is on duty.
Outlook /Saturday through Tuesday/...
Saturday: Winds less than 25 kt. Areas of rough seas.
Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers.
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Sunday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Monday through Tuesday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents from Friday morning through Saturday
evening for MAZ007-015-016-019>021-023.
High Surf Advisory from 8 AM Friday to 8 PM EDT Saturday for
MAZ022-024.
RI...High Risk for Rip Currents from Friday morning through Saturday
evening for RIZ006>008.
MARINE...Small Craft Advisory from 5 PM Friday to 8 PM EDT Saturday for
ANZ250.
Small Craft Advisory from 2 AM to 8 PM EDT Saturday for ANZ251.
Small Craft Advisory from 8 PM this evening to 8 PM EDT
Saturday for ANZ254>256.
&&
$$
SYNOPSIS...Dooley/Nocera
NEAR TERM...Dooley
SHORT TERM...Dooley
LONG TERM...Nocera
AVIATION...Dooley/Nocera
MARINE...Dooley/Nocera
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 5, 3:41 PM EDT----------------
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