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Area forecast discussion
National Weather Service Taunton Massachusetts
648 am EST Wed Nov 22 2017

Synopsis...
a cold front approaches the region today, and with moisture
working up the eastern Seaboard to bring a period of rain this
morning, especially southeast New England. Quiet weather Thursday and
Friday. Another shot of wet weather and breezy conditions this
weekend. Drier and milder toward the middle of next week.

&&

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

Latest runs of the high resolution guidance, most notably the
hrrr, appear to have a very good handle on the location and
timing of the band of moderate to heavy rainfall working into
southern New England this morning. As such, relied heavily upon
the hrrr to try and refine the rainfall details through today.

No other major changes to the forecast for today. Adjusted the
next several hours to reflect observed trends.

Previous discussion...

Split flow across the region early this morning as northern
stream cold front approaches from the Great Lakes. Southern
stream shortwave/coastal low off the Carolina coast will move
northward up the East Coast. This system will remain well
offshore but its moisture plume will impact the region.

Currently, surface cold front is making its way into upstate
New York. Radar imagery shows some showers along this front, but
overall moisture is pretty meager. Southern New England remains
in the warm sector ahead of this approaching front thus temps
early this morning have reside above average. In fact, the
office is currently a balmy 51 degrees with Nantucket at 56f.

Focusing south, latest GOES-16 satellite shows moisture
beginning to stream northwards towards New England thanks to
Bermuda high pressure. Current radar imagery shows widespread
showers across the Carolina coast, with scattered showers
developing across Long Island and into southeast Massachusetts.
These showers are associated with the upper level jet and mid-
level moisture at 700mb. At the surface, Theta-E gradient has
set-up with a 1000-925mb frontogenesis which has help aided the
showers in southern New England. The profile has moisten up as
guidance suggested as rainfall is being reported from wst to
ewb.

Over the next few hours, moisture will continue to stream into
the region as surface cold front from the west approaches. This
will help pool the moisture into the area and push precipitable water values
to above 1.0 inch by the mid-morning hours. Showers will begin
to overspread the rest of the region after 7am. The combination
of the upper level jet and low level jet will help aid in strong lift for
the region. In fact, guidance continues to hint at strong Omega
during the mid-morning hours especially along and points east of
I-95. This combined with the high pwats will lead to heavy
downpours across Rhode Island and eastern Massachusetts. Ncar ensembles continue to
show the potential for 40dbz during the 7am to noon time-frame.
Also cannot rule out a rumble or thunder as guidance continues
to hint as sb cape thanks to higher dewpoints.

Continued to trend quantitative precipitation forecast towards the ec but with the hi-res
guidance mix in as well. Appears that heavy precip axis will be
along of just east of the I-95 corridor. This is also supported
by the href, ncar ensembles and hrrr. Generally 0.5 to 1 inch
quantitative precipitation forecast will fall across a line east of ijd to bvy. Highest amounts
will occur just east of I- 95. Areas west of the Worcester Hills
will see rainfall amounts less than 0.25 inches.

As the front pushes through southern New England, precip will
exit the region by the mid-afternoon. Behind the front, dry but
cooler air will quickly usher into the region leading to temps
dropping through the afternoon hours and winds beginning to pick
up. Overall anticipate a rainy morning leading to heavy
downpours slowing the morning commute. Conditions will improve
by the afternoon hours leading to a great, but chilly start to
the Holiday travel.

&&

Short term /6 PM this evening through 6 PM Thursday/...
tonight into Thanksgiving day...

Cold front will be offshore by this evening as strong cold air advection usher
into the region. Good mixing with this cold air aloft resulting
in gusty northwest winds near 20-25 miles per hour during the overnight hours.
Surface high pressure approaching from the west may be enough to
allow for the winds to slacken off resulting in radiational
cooling before daybreak. Highest confidence is across the
interior. Thus will keep temps cooler than mav/met guidance.

Chilly start to the Thanksgiving Holiday as high pressure from
the west builds into the region. Weak shortwave aloft will
increase cloud cover during the afternoon. Moisture associated
with this wave looks meager enough to keep the forecast dry.
Westerly winds at the surface as temperatures in the upper 30s
to low 40s across the region. Overall, a chilly but dry Turkey
day as temperatures will remain 5 to 10 degrees below normal.

&&

Long term /Thursday night through Tuesday/...
*/ highlights...

- quiet weather through Friday
- showers possible at times this weekend, could be breezy
Sunday
- turning mild Tuesday into Wednesday, could also be breezy

*/ overview...

22/00z guidance suite is rather good overall agreement into
Sunday. More detail differences become more prevalent early next
week. Continue to favor a consensus approach to smooth over the
less predictable details, particularly with timing and amplitude
of various shortwaves moving through the larger synoptic pattern.

In general, expecting a mid level longwave trough to linger
near our region Friday into Saturday. As previously note, this
is more of a split flow during this time. Majority of the
guidance merges this flow into a deeper mid level trough Sunday
into Monday. This mid level trough expected to finally move
over the Maritimes toward the middle of next week.

Only concern for precipitation during this time will be this
weekend. Besides a series of front Saturday, will need to
monitor the progress of an offshore low pressure. At this time,
thinking this coastal low remains far enough east to not have a
major impact other than increasing the pressure gradient,
especially Sunday.

&&

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/...high confidence.

Today...mixed MVFR/IFR ceilings through the day with rain and visibilities
1-3sm at times in rain/+ra, low risk tsra, especially east of kpvd-
kghg. Areas west may remain mixed MVFR/VFR with mainly -ra. Rain
clears and rapid improvement to VFR occurs after 18z from west-east
as winds shift to the northwest and become gusty.

Tonight into Thursday...VFR. Westerly flow around 10 kt.

Kbos terminal...
bulk of -ra/rain progged 12-20z, mainly MVFR cigs, with +ra/IFR
threats 14-18z. Feel thunderstorms and rain will remain southeast of the terminal.
Clearing to VFR after 20z, with cold frontal passage expected
between 18-20z.

Kbdl terminal...
feel rain/+ra threats will remain east. Looking at mostly -ra
developing around 12z persisting through 18z. MVFR cigs with
lesser impact to visibility. Clearing out shortly after 18z.

Outlook /Thursday night through Sunday/...

Thanksgiving day: VFR.

Thursday night through Friday night: VFR. Breezy.

Saturday: VFR. Breezy. Slight chance rain showers.

Saturday night: VFR. Slight chance rain showers.

Sunday: VFR. Breezy.

&&

Marine...
forecaster confidence levels...

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

Short term /through Thursday/...

Today...high confidence.

Passing cold front during the day and passing coastal low well east
of the waters will lead to widespread rainfall today which could
limit visibilities. Seas will remain near 5 feet for the outer waters but
Small Craft Advisory have been let go elsewhere.

Tonight into tomorrow...high confidence.

Strong cold air advection across the relatively warm waters will result in gusts northwest
winds between 25-30 kts. Seas will also build in response. Small Craft Advisory have
been reissued to account for this trend. Low confidence on gales for
the eastern ocean waters. Conditions will improve on Thanksgiving,
but seas will remain choppy into the afternoon.

Outlook /Thursday night through Sunday/...

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

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

Friday through Friday night: winds less than 25 kt. Areas of
seas approaching 5 ft.

Saturday through Saturday night: winds less than 25 kt. Areas
of seas approaching 5 ft. Chance of rain showers.

Sunday: moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Seas up to 5 ft. Slight chance of rain showers.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory from 4 PM this afternoon to 4 am EST
Thursday for anz230>234-251.
Small Craft Advisory from 4 PM this afternoon to 1 am EST
Thursday for anz236.
Small Craft Advisory from 4 PM this afternoon to 2 PM EST
Thursday for anz235-237.
Small Craft Advisory from 4 PM this afternoon to 8 PM EST
Thursday for anz250.
Small Craft Advisory until 8 PM EST Thursday for anz254>256.

&&

$$
Synopsis...Belk/dunten

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