579
FXUS61 KBOX 201049
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
649 AM EDT Sat Jul 20 2024

.SYNOPSIS...
High pressure will build southeastward early today. While this will
bring a modest increase in cloud cover, mostly dry weather,
seasonably warm temperatures and lower humidity levels are expected
through the weekend. The pattern turns more active again next
week with increasing humidity and periods of wet weather with
heavy rain possible.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
The main change today will be increasing cloudcover as mid and high
clouds advect in on southwest flow around the high to our east. A
layer of moisture around 800 mb also allows for some diurnal clouds
to pop up late morning/afternoon as well, so expect a mix of clouds
and sun much of the day. Dewpoints initially in the 50s will
increase to the low 60s by the day`s end on increasingly moist SW
flow, but comfortable humidity continues for much of the day
accompanying high temperatures in the mid 80s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
While SNE remains under the influence of cyclonic flow aloft through
the weekend a weak disturbance will rotate around the trough with
potential to kick off an isolated shower later Saturday given PWATs
briefly rising back to 1.5" and a weak warm front moving north.
However, limited forcing should keep any pop-up showers isolated and
most locations remain dry. Sunday looks to be more of the same, with
mostly dry conditions but increasing lapse rates with diurnal
heating beneath -10C temps at 500mb may allow for a few isolated
diurnal showers. Less cloudcover will allow for temps a few degrees
warmer, in the upper 80s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Key Points

* Seasonable temps with increasing humidity next week.

* Unsettled weather pattern returns with daily chances for rain and
  thunderstorms Monday - Friday.

A more active pattern will set in again next week as deep SW flow
aloft kicks back in bringing increased moisture and humidity.
Temperatures this time wont be nearly as hot with highs peaking in
the upper 80s Monday, then falling into the upper 70s to mid 80s by
Wednesday and Thursday. Dewpoints on the other hand will rise into
the upper 60s to low 70s again Monday and stay there through the
week. As for rain chances this week, exact timing of features
remains messy with several weak shortwaves traversing through the SW
flow. Monday at this time appears the driest day with only isolated
thunderstorms possible. Not expecting any severe thunderstorms with
less then 500 J/kg of MLCAPE.

A stronger shortwave and associated surface low looks to exit the
Ohio River Valley mid week. Guidance was in good agreement on timing
of this feature bringing it through late Tuesday into early
Wednesday, but has since become more spread on the timing bringing
it in as early as Tuesday afternoon to as late as Thursday
afternoon. Guidance is also in significant disagreement on exact
track of the low. PWATS ahead of this low increase upwards of 1.5 to
2.0+ inches which could bring heavy rain concerns to SNE. WPC has
highlighted much of New England in a marginal risk for excessive
rain on Wednesday. 24 hour Ensemble mean QPF for Wed and Thur are
showing a wide spread 1/4 to 1/2 inch of rain, with 99th percentile
still showing localized areas of 2 - 3 inches. Will also need to
watch for severe weather in this time period with CSU machine
learning guidance showing 5% probs for severe thunderstorms on
Wednesday and Thursday.

Looking way ahead to next weekend, the pattern appears to bring back
drier conditions with an upper level ridge building in. This could
bring back excessive heat concerns with CPC highlighting SNE in a
slight risk for excessive heat.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

12z update...

Today...High confidence.

VFR, with increasing mid to high clouds today. Light and
variable winds early this morning increast to 5-10 kts from the
SW today.

Tonight...High confidence.

VFR. SW winds around 5 kt.

Sunday...High confidence.

VFR. W winds 5-10 kts.

KBOS TAF...High confidence in TAF.

VFR thru the period. SE seabreezes to shift to light S winds by
00-01Z, then increasing to around 5-10 kt on Sat and shifting to
SW.

KBDL TAF...High confidence in TAF.

VFR thru the period. Variable winds shift to SW at 5-10 kts by
Sat afternoon.

Outlook /Sunday Night through Wednesday/...

Sunday Night through Monday: VFR.

Monday Night: VFR. Slight chance SHRA, isolated TSRA.

Tuesday through Tuesday Night: Mainly VFR, with local MVFR
possible. Chance SHRA, isolated TSRA.

Wednesday: MVFR/IFR conditions possible. Chance SHRA, isolated
TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.

Through Sunday: High confidence.

W/SW winds becoming breezing today especially over the
nearshore waters, with speeds around 15-20 kt during the
daytime hrs; decreasing to 10 kt or less this evening. Seas 2-3
feet or less all waters. Mostly dry weather to prevail though an
isolated shower is possible. Dry weather continues for Sunday
with SW winds continuing. Seas 2-3 feet.

Outlook /Sunday Night through Wednesday/...

Sunday Night through Monday Night: Winds less than 25 kt.

Tuesday: Winds less than 25 kt. Slight chance of rain showers.

Tuesday Night: Winds less than 25 kt. Chance of rain showers.

Wednesday: Winds less than 25 kt. Chance of rain showers,
isolated thunderstorms.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$

SYNOPSIS...BL/KP
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...KP
AVIATION...BW/KP
MARINE...BW/KP