Preview of NWS' New Version of Forecast
This preview is not operational and should not be used for support decisions.

Area Forecast Discussion (AFD)

Issued by Boston / Norton, MA (BOX)

                            
000
FXUS61 KBOX 191735
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
135 PM EDT Thu Sep 19 2019

.SYNOPSIS...
High pressure lingers over our region through early next week. 
Below normal temperatures late this week will trend to above  
normal temperatures over this weekend and early next week. A 
cold front brings the next chance of showers early next week. 
Distant Hurricane Humberto will bring high surf and dangerous 
rip currents late this week, which should peak on Friday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
945 AM update...

High pres overhead will bring abundant sunshine and light N/NE
winds with sea breezes developing along east coastal MA. 12z 
soundings tell the story with very dry air throughout the column
and PWATs near 0.25". Temperatures will remain below normal,
generally mid 60s to near 70, but cooler along the immediate 
coast.

East-southeast swell from Hurricane Humberto will continue to
impact the coastline of southern New England. Rough surf and
dangerous rip currents will affect ocean-exposed beaches.
Swimming is not recommended, nor is walking out on low-lying
piers or jetties. High Surf Advisories will continue.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Dry weather continues through Friday. Swell from Humberto will
also continue the threat for rough surf and dangerous rip currents.
With warming conditions Friday, will continue the High Surf Advisory
through much of Friday along ocean-exposed portions of the coast.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
*/ Highlights...

 - Lingering high surf, dangerous rip currents Saturday
 - Warm weekend, anticipating fantastic weather
 - Mild days, cool nights the following week
 - Two shots at wet weather around Monday night and Thursday night

*/ Overview... 

BIGGEST CONCERN: Weekend lingering swell from Humberto during which 
the weather will be fantastic and beaches unguarded. High surf and 
dangerous rip currents pose a threat to life, especially Saturday 
during which beach hazard statements will likely be needed. Those 
interested in observing the surf should do so from a safe distance. 
Swimming is not recommended. 

OTHERWISE: Mostly mild, dry long-range forecast. Continued ensemble-
weighted +WPO/+EPO/-PNA/+AO/+NAO teleconnections with a phase 8 to 1 
MJO. Signals pointing towards warmer than average E CONUS conditions 
ahead of preferred W CONUS troughing. But there's some hope we will 
see some rain that'll wash out all the airborne allergens. Upstream 
N Pacific pattern amplifying, buckling, potentially cutting off W 
CONUS troughing, energy cascades E along with continental-tropical 
airmasses. So long as N Atlantic higher heights do not suppress the 
environment given an active tropical pattern and subsequent latent 
heat release, we could see some decent shots of much needed rain, 
the first around Monday night with a second around Thursday night. 
Associated mid-level disturbances and accompanying jet dynamics in 
concert with sweeping cold fronts, while specifics remain uncertain 
far out in time, any rainfall is welcoming. 

Aside from the weekend which is looking rather warm, most locations 
in the 80s well-above normal highs around the low 70s, looking at a 
trend of mild days and cool nights. Some uncertainty as to whether 
the upstream pattern reloads (preferred W CONUS troughing) acting to 
buckle colder air N. Aside, there's the possibility the following 
weekend that we could see our first shot of cool Canadian air right 
on time with the start of Autumn. Continued preference of ensembles 
given pattern uncertainty and recent deterministic adjustments to 
wetter outcomes through next week.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

Short Term /through Friday/...High confidence.

VFR through the period. Diminishing NE wind this afternoon
Cape/Islands. 

KBOS Terminal...High confidence in TAF. 

KBDL Terminal...High confidence in TAF. 

Outlook /Saturday through Monday/...

Saturday through Saturday Night: VFR. 

Sunday through Sunday Night: VFR. Breezy. 

Monday: VFR. Breezy. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Friday/...High confidence.

High pressure centered over New England. N to NE winds will
continue to diminish through today, then become light W to NW
tonight into Friday. E swell from Hurricane Humberto will build
through the day, with swell up to around 7 feet forecast by
tonight into Friday. Rough seas will require Small Craft
Advisories to continue across the outer coastal waters through
Friday.

Outlook /Friday Night through Monday/...Moderate confidence.

Friday Night: Winds less than 25 kt. Areas of rough seas. 

Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft. 

Saturday Night through Sunday: Winds less than 25 kt. 

Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. 

Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. Chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Surf Advisory until 6 PM EDT Friday for MAZ020-022>024.
     High Surf Advisory from midnight tonight to 6 PM EDT Friday 
     for MAZ007-019.
RI...High Surf Advisory until 6 PM EDT Friday for RIZ006>008.
MARINE...Small Craft Advisory until 2 AM EDT Saturday for ANZ250-
     254>256.
     Small Craft Advisory from 6 AM Friday to 2 AM EDT Saturday for 
     ANZ251.

&&

$$
SYNOPSIS...Belk/Sipprell
NEAR TERM...Belk/KJC
SHORT TERM...Belk
LONG TERM...Sipprell
AVIATION...KJC/Sipprell
MARINE...Belk/Sipprell