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Area forecast discussion
National Weather Service Boston/Norton Massachusetts
659 PM EDT Fri Oct 18 2019

Synopsis...
high pressure will build across the region this weekend bringing
dry and seasonable Fall-like weather. Low pressure across the
Great Lakes with another low well south of Nantucket will
likely bring showers and gusty onshore winds Tuesday into the
mid week timeframe. Another high builds to the mid Atlantic
coast with more dry weather around Thursday.

&&

Near term /until 6 am Saturday morning/...

700 PM update...

No major changes to the near term forecast this evening. Skies
continue to clear with the last of the mid level deck lingering
over western Massachusetts and CT this evening. These will be gone in
plenty of time to benefit from radiative cooling overnight.

The big storm from yesterday will continue to move north across
eastern Canada tonight as high pressure builds in from the west.
This coupled with the loss of daytime heating should allow gusty
winds to diminish early this evening. We also should see the strato
cumulus dissipate this evening with skies eventually becoming mainly
clear tonight.

Diminishing winds coupled with mainly clear skies should result in a
good night of radiational cooling. Low temps in many locations
should bottom out in the lower to middle 30s. We have continued the
frost advisory for the areas that were technically still in the
growing season. The urban heat islands of Boston/Providence should
only drop into the upper 30s to lower 40s by daybreak.

&&

Short term /6 am Saturday morning through Saturday night/...
Saturday...

High pressure overhead will result in a very nice fall day. After a
chilly start, mostly sunny skies should allow Sat afternoon high
temps to top out near 60 in most locations. Light winds and lots of
sunshine will make for a rather comfortable, but fall-like afternoon.

Saturday night...

High pressure will remain in control of the region, resulting in
continued dry/tranquil weather. Model cross sections do indicate
that some high thin cloudiness may move into the region, but do not
expect them to have much impact on temperatures. The relatively dry
airmass in place along with light winds should allow a good night of
radiational cooling. Low temperatures by daybreak Sunday will be in
the upper 20s to the middle 30s in most locations except milder in a
few of the urban centers. Additional frost/freeze headlines will
likely be needed where the growing season is technically still in
progress.

&&

Long term /Sunday through Friday/...
highlights...

* remnants of tropical storm Nestor may bring some showers on
Sunday, mainly to the South Coast
* dry Monday under high pressure ridge
* unsettled weather returns tues/Wed with rain and gusty winds
* dry late week

Sunday and Monday...

Upper level ridge axis crosses the region early Sunday, placing
southern New England on the backside of the ridge under SW return
flow aloft, brining in more moisture and cloudy skies. Better cloud
coverage the further south you go, in closer proximity to the
subtropical tap of moisture lifting north. This is associated with
what is now tropical storm Nestor, currently in the Gulf of Mexico.
Nestor is expected to move off the coast of North Carolina into the
western Atlantic as a Post-tropical cyclone late Sunday. Currently
the most consistent guidance keeps the low center far enough south
that southern New England should escape any significant wind/rain,
with perhaps the northern periphery of the rain shield reaching the
South Coast or toward the Mass Pike. For now going with a slight
chance of rain showers Sunday in southern Massachusetts and southern Rhode Island.

Monday, while the remnants of Nestor meander well to our south a
nice day is in store. An inverted ridge of high pressure keeps the
low center away while a mid level heights rise. Good subsidence and
a dry column will lead to a sunny, dry day with highs in the 60s.
This is right in line with seasonal normals for late October. The
gradient between the high and remnant low to our south may make
things breezy along the South Coast, but not expecting anything
particularly impactful (gusts 15-25 mph).

Tuesday and Wednesday...

Next chance of rain ramps up on Tuesday, maximizing in probability
and rainfall amounts Tuesday evening through the overnight hours.
This as a deep mid level shortwave approaches from the Midwest,
becoming negatively tilted as it approaches New England Tuesday
night. A deep plume of moisture precedes the associated cold front
which crosses the region sometime late Tuesday or early Wednesday.
Additionally, along this frontal boundary a secondary low is
generated over the Delmarva, while likely phasing with the remnants
of Nestor. A lot of dynamic mesoscale features will be in play with
many moving parts, details of which will come into better focus as
we approach. All things considered, none of the guidance shows this
system getting near the strength of this past week's storm; no eps
members take the low sub-1000mb over southern New England. So,
expecting a rain event with breezy winds - details to be ironed out
in the future.

Thursday and Friday...

Dry weather on tap to end the week as high pressure takes hold. No
major warm ups or cool downs; temperatures stay seasonal with highs
in the low 60s and lows in the 40s.

&&

Aviation /00z Saturday through Wednesday/...
forecaster confidence levels...

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

Short term /through Saturday night/...

00z update...

Tonight...high confidence. VFR conditions as the remaining
strato cumulus dissipates this evening. Gusty northwest winds
diminish early in the evening.

Saturday and Saturday night...high confidence in VFR conditions.
Northwest winds of 5 to 10 knots during the daylight hours Saturday
become very light Saturday night.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Sunday through Wednesday/...high confidence.

Sunday: VFR. Slight chance rain showers.

Sunday night: VFR.

Monday through Monday night: VFR. Breezy.

Tuesday: mainly VFR, with local IFR possible. Breezy. Chance
rain showers.

Tuesday night: mainly VFR, with local IFR possible. Breezy.
Rain showers likely.

Wednesday: VFR. Breezy. Chance rain showers.

&&

Marine...
forecaster confidence levels...

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

Short term /through Saturday night/...

Tonight...high confidence. Lingering Small Craft Advisory winds/seas will gradually
diminish as the night wears along from west to east. This in
response to high pressure building in from the west. Small Craft Advisory headlines
will gradually expire in most locations tonight as a result.

Saturday and Saturday night...high confidence. High pressure in
control will keep winds/seas below Small Craft Advisory thresholds.

Outlook /Sunday through Wednesday/...moderate confidence.

Sunday through Sunday night: winds less than 25 kt. Slight
chance of rain showers.

Monday: winds less than 25 kt. Local rough seas.

Monday night: winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.

Tuesday: low risk for Small Craft Advisory winds with gusts up
to 25 kt. Rough seas up to 9 ft. Chance of rain showers.

Tuesday night: low risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 9 ft. Rain showers likely.

Wednesday: moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 8 ft. Chance of rain
showers.

&&

Box watches/warnings/advisories...
CT...frost advisory from 3 am to 8 am EDT Saturday for ctz002>004.
Massachusetts...frost advisory from 3 am to 8 am EDT Saturday for maz017-018.
Rhode Island...frost advisory from 3 am to 8 am EDT Saturday for riz001-003.
Marine...Small Craft Advisory until 8 PM EDT this evening for
anz231>235-237-251-256.
Small Craft Advisory until 8 am EDT Saturday for anz250-254.
Small Craft Advisory until 2 am EDT Saturday for anz255.

&&

$$
Synopsis...Frank/bw
near term...Frank/bw

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