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Area forecast discussion
National Weather Service Boston/Norton Massachusetts
206 am EDT Sat Oct 19 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 this morning/...

2 am update...

No major changes from previous forecast. Dry northwest flow continues
into southern New England with 992 mb maritime low and 1018 mb
eastern Great Lakes high pressure. Northwest winds will continue to
slacken overnight and with mostly clear skies (decreasing
clouds across CT into western ma) along with dry airmass in
place (dew pts in the 30s) will yield a chilly/frost night ahead
with lows in the 30s. Not as cold for Boston Cape Cod and
islands where northwest winds will preclude temps from free falling
yielding lows in the lower 40s.

&&

Short term /6 am this morning through 6 PM Sunday/...

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 night 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 /06z Saturday through Wednesday/...
forecaster confidence levels...

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

Short term /through Sunday/...

06z update ... high confidence thru Sunday morning then lowering
sun PM regarding how far north rain shield and MVFR conditions
from remnants of Nestor track.

Today ... VFR, dry and light west-northwest winds.

Tonight ... VFR and dry conditions continue but light northwest winds
late today become light and variable tonight.

Sunday ... VFR, dry weather and light winds to start the day but
then rain shield from remnants of Nestor approach CT late in the
day.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

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

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 Sunday/...

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 night 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 until 8 am EDT this morning for ctz002>004.
Massachusetts...frost advisory until 8 am EDT this morning for maz017-018.
Rhode Island...frost advisory until 8 am EDT this morning for riz001-003.
Marine...Small Craft Advisory until 8 am EDT this morning for anz250-
254.
Small Craft Advisory until 2 am EDT early this morning for
anz255.

&&

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

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