Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kbox 181056 
afdbox

Area forecast discussion
National Weather Service Boston/Norton Massachusetts
656 am EDT Wed Sep 18 2019

Synopsis...

High pressure will maintain an extended period of dry weather
into this weekend other than perhaps a brief spot showers /
sprinkles this morning. Below normal temperatures into Thursday
will moderate by Friday with unseasonably warm afternoons this
weekend into Monday. Distant Hurricane Humberto will bring high
surf and dangerous rip currents late this week, which should
peak on Friday. A cold front may finally bring a few brief
showers sometime Monday and/or Monday night, but if any rain
occurs amounts will be light.

&&

Near term /until 6 PM this evening/...

7 am update (no major changes)...

High pressure will build across New England and the Maritimes
today. Any leftover sprinkles this morning should end this morn.
The most clouds should be towards Rhode Island and southeast Massachusetts. Clearing
skies by late in the day.

Gusty NE winds, especially towards the coasts. Colder air arrives.
Expecting high temperatures to be about 5-10 degree lower than
Tuesday.

Swell from distant Hurricane Humberto will start to impact portions
of the southern New England coastline today. High risk for rip
currents towards the cape and islands, which will be highlighted
with a high rip risk statement.

&&

Short term /6 PM this evening through 6 PM Thursday/...

High pressure brings clear skies and light wind tonight into
Thursday. Portions of the more sheltered Connecticut River valley
could see some frost early Thursday morning. Have posted a frost
advisory where this risk is highest. Later shifts could expand
it if confidence grows.

Dry with slightly higher temperatures Thursday.

Will gradually expand the high rip current risk statement through
Thursday as swell from Humberto continues to arrive. Despite
the dry weather, it will be dangerous to be in the ocean along
ocean-exposed beaches, especially since most, if not all, of
these beaches are now unguarded. Swimming is not recommended in
these areas.

&&

Long term /Thursday night through Tuesday/...

*/ highlights...

- high surf and dangerous rip current conditions along ocean beaches
- this the result of ocean swell associated with Cat 3 Humberto

- mild days, cool nights through the week, dry throughout
- weekend heat prior to an early week cold front with spot showers
- warmth building back over the following week

*/ overview...

Biggest concern: as will be noted below, we've got some nice weather
coming up this weekend as high surf and dangerous rip currents are
expected along ocean facing beaches associated with the swell from
presently category 3 Humberto. The absence of life guards given the
now off-season, there is certainly a concern for beachgoers. Those
interested in observing the surf should do so from a safe distance.
Swimming is not recommended.

Mild, dry. Continued ensemble-weighted +wpo/+epo/-pna/+ao/+nao tele-
connections along with consensus forecast phase 1/8 mjo. Altogether,
signals support further North Atlantic tropical development and latent
heat release through the troposphere as broader synoptics suggest a
stormy pattern over western North America with a heat pump into eastern
North America (noting ensemble-weighted 850 mb temperature anomalies). A
trend towards higher heights, an axis of drier outcomes apparent in
ensemble precipitation totals across the east Continental U.S. With amounts around
0.50, all seemingly the result of wedged high pressure / subsidence
between resisted S-dips of maritime energy ejecting from the west Continental U.S.
Trof and offshore tropical-axis round the North-Atlantic steering flow.
Any surface cold fronts sliding S associated with the north-stream are
going to struggle under the weight noted above. Diffuse, light out-
comes subsequent hence the low ensemble-weighted total precipitation
amounts. In other words, looking dry through the rest of September
which is typically climatologically one of our driest months. With
dependency on low level winds associated with the location of the
surface high, days in which S/SW flow prevail we could easily get to
90 which per daily records is not impossible. Not surprisingly, CPC
day 6-10 and 8-14 day outlooks continue to advertise above average
temperatures which normally for late September see highs around 70
with lows around 50.

An ensemble blend forecast with lower certainty on specifics further
out in the forecast. Warming trend into the weekend as high pressure
shifts east and S/SW winds prevail prior to a sweeping cold front early
the following week with a chance of showers. Could see a brief cool
down thereafter before warmer weather builds back in as we go into
autumn.

&&

Aviation /12z Wednesday through Sunday/...

Forecaster confidence levels...

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

Short term /through Thursday/...

Today...
scattered-broken low-end VFR cigs with spot -shra this morning, some
isolated MVFR, becoming scattered VFR while -shra conclude into this
afternoon. Breezy NE winds throughout sustained around 10 to 15
kts with gusts around 20 to 25 kts, upwards of 30 kts along ack.

Tonight and Thursday...
VFR. Gusty NE winds continue, but not as strong as today.
Generally around 10 kts with gusts up to 20 kts.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Thursday night through Sunday/...

VFR.

&&

Marine...

Forecaster confidence levels...

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

Short term /through Thursday/...high confidence.

High pressure remains centered over the Saint Lawrence valley.
NE winds continue across the waters. Increasing pressure
gradient between this high pressure and Hurricane Humberto.
Gusty winds and rough seas expected, especially across the outer
coastal waters. Small craft advisories continue across most
waters into this evening. Winds diminish some late tonight into
Thursday, but rough seas will continue.

Outlook /Thursday night through Sunday/...moderate confidence.

Thursday night: winds less than 25 kt. Areas of rough seas.

Friday: winds less than 25 kt. Rough seas up to 12 ft.

Friday night: winds less than 25 kt. Rough seas up to 10 ft.

Saturday: winds less than 25 kt. Seas up to 5 ft.

Saturday night: winds less than 25 kt. Seas locally approaching
5 ft.

Sunday: winds less than 25 kt.

&&

Box watches/warnings/advisories...

CT...none.
Massachusetts...high rip current risk through Friday afternoon for maz022>024.
High rip current risk from late Thursday night through Friday
afternoon for maz007-019.
High rip current risk from late tonight through Friday
afternoon for maz020.
Frost advisory from 3 am to 8 am EDT Thursday for maz003-010.
Rhode Island...high rip current risk through Friday afternoon for riz008.
High rip current risk from late tonight through Friday
afternoon for riz006-007.
Marine...Small Craft Advisory until 2 am EDT Thursday for anz231>234-
251.
Small Craft Advisory from 10 am this morning to 8 PM EDT this
evening for anz236.
Small Craft Advisory until 8 am EDT Thursday for anz235-237.
Small Craft Advisory until 8 PM EDT Thursday for anz250-
254>256.

&&

$$

Synopsis...Belk/sipprell
near term...Belk/sipprell

National Weather Service Glossary of Abbreviations