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Area forecast discussion
National Weather Service Taunton Massachusetts
641 am EST Tue Nov 21 2017

Synopsis...
mild day today as winds shift to the southwest. A cold front
approaches the region tonight, and will combine with moisture
working up the eastern Seaboard to bring a period of rain
through Wednesday morning, especially southeast New England. Dry and
colder conditions expected Wednesday night through the end of
this week. Milder with a few showers possible Saturday as a cold
front approaches, then blustery and colder weather follows
Sunday into Monday.

&&

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

No significant changes to the forecast this morning. Only minor
tweaks to bring forecast back in line with observed trends.
Expecting gusty winds to develop quickly this morning as low
level warm advection gives the mixing process a little kickstart.

Previous discussion...

Mid-level ridge axis will push northward towards the Maritimes
today as cold front from the west approaches the region. Overall
anticipate a dry day as southwest winds take hold of the region.
Strong warm air advection will continue to stream into the region as 925mb
temps warm near 7-9 c by the afternoon. BUFKIT soundings
indicate mixing to near 900 mb thus expect temperatures to warm
well into the 50's with locations across southeast mass near the
upper 50's. If we mix a bit higher, then cannot rule out a few
spots reaching 60f.

Clear skies across the area today. Cross sections show some
moisture across the cape and islands which could bring a mix of
clouds and sun. Otherwise the focus is on the winds for today.
Increasing low level jet ahead of approaching front will mix down to the
surface today. Expect southwest winds gusting to around 25-35
miles per hour.

&&

Short term /6 PM this evening through 6 PM Wednesday/...
dry weather to start tonight ahead of approaching cold front
from the west. High pressure to the east of the region will help
increase southerly low level moisture off the ocean. This flow
will increase low level moisture and thus some isolated showers
after 2 am across the South Coast.

Upper level shortwave will help push the front closer to the
region during the early morning hours. While moisture appears to
be meager with this front, the focus is more on the coastal low
which will develop off the coast of the Carolinas. Moisture
from this low will stream into the region resulting in precipitable water
values increasing to 1 inch which is 1-2 Standard above normal.
Appears that the 2 systems will remain split from each other,
however the interactions between the upper and low level jets
will help increase lift across the region. In fact, some model
guidance suggest strong lift around daybreak which could lead to
heavy downpours which will impact the Wed morning commute.
Still a spread in where the heavy axis will be located with the
ec and rgem on the western envelope compared to hi- res guidance
and NAM. The GFS continues to the eastern outlier and thus
trended away from it. Right now appears the the axis of heavier
rainfall will occur across the I-95 corridor and points
eastward. However this axis could still shift if the two streams
do meet up, of if coastal low trends farther eastward.
Regardless, looks like a good slug of rain with quantitative precipitation forecast amounts
around 0.5-1 inch. These amounts could also increase within any
thunderstorms. Went ahead and inserted a slight chc of thunder
as dewpoints reach into the 50s and models continue to show some
surface cape. Highest confidence will be across the cape and
the islands.

Conditions will quickly improve from west to east during the
day on Wednesday. In fact, once the cold front moves through the
region, dry air will quickly usher into the region resulting in
clearing skies and dry weather. Cold air advection will spill into the area
resulting in temperatures to fall during the day. Northwest winds will
also be on the increase as wind gusts increase to 25-30 miles per hour by
the afternoon.

&&

Long term /Wednesday night through Monday/...
highlights...

* mainly dry and cool Thanksgiving day and Friday
* milder with a chance of showers Saturday
* blustery and colder Sunday/Monday

21/00z guidance suite remains in rather good agreement on the
overall pattern through this portion of the forecast. In
general, looking at a persistent mid level trough lingering near
our region, although the amplitude and axis varies with time as
various shortwaves move through the flow. This should mean
temperatures trending below normal, especially late this weekend
into early next week.

Dry weather likely to persist into Friday, despite a cold front
getting close to the northern Massachusetts border Friday. The most
supportive moisture and dynamics for showers are expected to
remain over northern New England. Our next chance for
precipitation looks to be sometime this weekend. It's not
looking like a great risk, as humidity levels are somewhat
lacking. However, there are a couple of fronts to move through,
so this potential will need to be watched over the coming days.
Colder air arriving Sunday into Monday could generate some
ocean-effect showers toward the coast.

&&

Aviation /12z Tuesday through Saturday/...
forecaster confidence levels...

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

Short term /through Wednesday/...high confidence.

Today...VFR. Increasing south-southwest wind gusts 25-35 kt through the
day.

Tonight into Wednesday...VFR to start. Rain will overspread the
region from southwest to the northeast after 2 am lasting into
Wednesday morning. MVFR/IFR cigs within heavier rain showers
and fog. Conditions will improve to VFR quickly from west to
east during the day on Wed as cold front passes through.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Wednesday night through Saturday/...

Wednesday night: VFR. Windy with local gusts to 30 kt.

Thanksgiving day through friday: VFR.

Friday night: VFR. Breezy.

Saturday: VFR. Breezy. Slight 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 Wednesday/...high confidence.

Today...building seas across the region as low level jet increases ahead
of approaching cold front. Southwest wind gusts around 35-40 kts
will result in gales across the waters. Went ahead and included
mass Bay, Boston Harbor and Narragansett Bay as strong mixing
will occur during the afternoon.

Tonight into tomorrow...southwesterly gales will continue but
subside across the near shore waters. Small Craft Advisory will be needed as seas
will remain above 5 feet and gusts near 30kts. Approaching cold
front will bring widespread rain for the waters and limit vsbys
by Wed morning. Front will sweep through Wed afternoon switching
winds to the northwest with gusts near 30 kts by Wed evening.

Outlook /Wednesday night through Saturday/...

Wednesday night: low risk for Small Craft Advisory winds with
local gusts up to 30 kt. Seas up to 5 ft.

Thanksgiving day: winds less than 25 kt. Local rough seas.

Thursday night through Friday night: winds less than 25 kt.
Seas up to 5 ft.

Saturday: winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain showers.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Gale Warning from noon today to midnight EST tonight for
anz231>235-237-250-251-254>256.
Gale Warning from noon today to 6 PM EST this evening for
anz230-236.

&&

$$
Synopsis...Belk/dunten

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