BOX issues Area Forecast Discussion (AFD) at Aug 19, 3:35 AM EDT211
FXUS61 KBOX 190735
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
335 AM EDT Mon Aug 19 2024
.SYNOPSIS...
Dangerous rip current continue due to distant Ernesto today. A
slow moving frontal system moving in from the Great Lakes will
bring several opportunities for showers and thunderstorms
through tonight. Localized downpours are the main risk, but
severe weather is possible later this afternoon and early
evening. Drier weather for the middle portion of this week with
below normal temperatures. Warming trend for Friday into next
weekend, but with continued generally dry weather.
&&
.NEAR TERM /THROUGH TODAY/...
Unsettled day today with a slow-moving front approaching from
the west. The most complex aspect of this forecast will be
trying to time and locate the convective showers, and especially
any downpours that develop. Have high confidence that it will
rain, but significantly less confidence on the timing and
location. Even the rainfall amounts have low predictability.
19/00Z HREF LPMM had 3-4 inches of rainfall over portions of CT.
Normally, this would considered a high-end amount, but perhaps
not as much today based on existing reports. The best advice we
can give is to be prepared for downpours and localized flooding.
The main focus will be towards the south coast of New England
this morning. However, this focus will likely shift later today
as a cold front approaches from the west.
The severe weather risk is limited, but not non-existent.
Tremendous low level helicity was analyzed just south of New
England this morning. If instability were higher, then this
would be of greater concern. Will have to monitor this closely,
as it would not take much more instability to possibly rotate
some of the stronger thunderstorms this morning.
Expecting another round of showers and thunderstorms to arrive
this afternoon and evening from the west. Most-unstable CAPE
values of 1,000-1,500 J/kg are projected. Thus, the possibility
for a few stronger storms that could produce gusty winds or
small hail, in addition to more downpours.
Below normal temperatures expected today.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/...
Loss of daytime heating should lead to a rapid weakening of any
thunderstorms this evening. Thinking mainly rain showers tonight
as this front continues to move east across southern New
England. By Tuesday, drier weather should be dominant, other
than some lingering morning showers towards the east coast of
MA.
Near normal temperatures expected tonight, with below normal
temperatures for Tuesday.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Key Points:
* Cooler autumn-like weather on Wednesday
* Gradual warming trend into the weekend with high pressure
suppressing precipitation chances
A very quiet period in the long-term forecast. An upper-level
low associated with a cooler/drier air mass settles over
southern New England on Wednesday. With 925 hPa temps below 10C,
expect below normal temperatures for August in the upper 60s to
low 70s. Should be plenty of sunshine, but with the cold pool
aloft we can expect some diurnal cu to develop Wednesday
afternoon. As the upper-low shifts east Wednesday into Thursday,
high pressure begins to build in from the west. This will
support a warming trend into the weekend with near-normal
temperature sin the mid to upper 70s on Thursday increasing to
above normal temperatures in the mid to upper 80s by Sunday. The
rather large area of surface high pressure should suppress
precipitation chances during this time frame, so expect abundant
sunshine with only a few diurnal clouds developing during the
afternoons.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through this Morning: High confidence in trends, but only
moderate confidence on timing.
IFR-LIFR with widespread showers and isolated thunderstorms.
While this threat looks greatest during the early morning
towards the south coast. Categories are still expected to be
mainly in the IFR-LIFR range until we get to this aftn. SE
winds 5-10 kt should shift to S/SSW upon passage of warm front.
This Afternoon: Moderate confidence.
Expecting to see some breaks in clouds/improvement in flight
categories toward MVFR levels. Couldn't rule out a rogue SHRA or
TS during the early afternoon, but think better chances for
+SHRA/TSRA arrive after 21Z or so for the western airports
associated with the approach of a cold front. These storms may
become strong and produce gusty winds, frequent lightning and
heavy downpours reducing visibility.
Tonight: High confidence.
SCT TSRA, some strong to start, should advance eastward off the
Berkshires/CT Valley and weaken as they move east between 01-03z
Tue. MVFR/IFR to start, but should see rapid improvement to VFR
upon passage of this cold front. It may take until later tonight
or early Tue before we see VFR categories for eastern airports.
Tuesday: High confidence.
Becoming VFR.
KBOS TAF...High confidence in trends, moderate in exact timing.
KBDL TAF...High confidence in trends, moderate in exact timing.
Outlook /Tuesday Night through Friday/...
VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Tuesday...High confidence.
Expecting persistent SE to S flow at 5-10 kts through the vast
majority of the period. Wind gusts remain generally below 20 kts
as well. Seas remain elevated due to the powerful swell
associated with Ernesto. Small Craft Advisory continues into
Tuesday across the outer coastal waters, but only through today
across the nearshore RI coastal waters. Rain showers along with
a few thunderstorms will impact the waters today, especially
this morning. Poor visibility in showers and fog.
Outlook /Tuesday Night through Friday/...
Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft.
Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft.
Wednesday Night through Friday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents through this evening for MAZ007-022>024.
RI...High Risk for Rip Currents through this evening for RIZ006>008.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ235-
237.
Small Craft Advisory until 7 PM EDT Tuesday for ANZ250-256.
Small Craft Advisory until 10 PM EDT Tuesday for ANZ254-255.
&&
$$
SYNOPSIS...Belk/RM
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...RM
AVIATION...Belk/RM
MARINE...Belk/RM
Source:
BOX issues Area Forecast Discussion (AFD) at Aug 19, 3:35 AM EDT----------------
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