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Area forecast discussion
National Weather Service Taunton Massachusetts
1009 am EST Mon Jan 22 2018

Synopsis...

Some light precipitation is expected today and tonight. Most of it
will be rain, but light icing is likely over interior high terrain
especially tonight into early Tuesday. A fast moving storm system
will bring a period of heavy rain to the region Tuesday along with
strong winds across southeast New England. Blustery, dry and colder weather
follows Wednesday through Friday, then a warming trend next weekend.
A cold front may bring showers by next Sunday.

&&

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

1010 am update...

Weak warm advection over the shallow cool dome in place has
resulted in a band of rain showers sweeping across the region
this morning. While most of the precipitation was just
liquid...temps generally between 32 and 34 have resulted in some
slippery roads/walkways across parts of interior Massachusetts especially
in the high terrain. Despite marginal temperatures...paved
surfaces are still cold so some slick spots possible where even
temps are above freezing.

Batch of steady rain showers should exit the region by early
afternoon...but a few spot showers and pockets of drizzle along
with areas of fog will persist. May see threat for showers
increase toward evening...especially in our western zones as
forcing/deeper moisture moves into the region.

Temperatures will mainly hold in the 30s and there will
continue to be the threat for some icy travel across interior
Massachusetts...especially across the high terrain. Therefore...opted to
begin Winter Weather Advisory now to cover this potential. Still
monitoring the need to expand advisory across interior
northeast Massachusetts.

&&

Short term /6 PM this evening through 6 PM Tuesday/...
tonight...

A stalled front near or just north of the region will not move much
tonight as the low moves into the western Great Lakes. With the
colder air sitting across northern New England, noting the cold
air damming signature becoming better established tonight,
especially across north central and northwest mass. The bulk of the precip
will shift into northern New England, but will still see more
spotty light precip linger across the region. With the cold air
in place, and milder air working in aloft, will see periods of
light freezing rain continue. As mentioned above, the Winter
Weather Advisory remains in effect from North Worcester County
westward through the night. May see up to 0.1" ice accretion
across portions of the Route 2 corridor mainly west of the
Merrimack valley, where the best chance for freezing rain will
occur.

The warm front S of the region will start to lift north overnight,
so will see temps rise after midnight mainly toward daybreak
along the S coast, with readings holding around freezing well
inland.

Tuesday...

As the low pressure across the Great Lakes lifts into southern
Ontario, will see another shot of milder air lift northward.
This is also associated with a very strong low level jet, on the
order of 50-55 kt, which will move across portions of Rhode Island/southeast mass
during the morning and midday hours. Noting very good low level
mixing in place, along with an increasing pressure gradient as
the low to the west strengthens. Could see S winds gusting up to
35-45 mph Tuesday morning into midday as the jet passes.

Also noting a deep tropical moisture connection, as precipitable water plume
of 1 to 1.25" works across the region. Will also see some good
instability ahead of the approaching cold front as total totals
rise to the lower 50s. Have also mentioned the chance for an
isolated thunderstorms as the front crosses the region from
midday through the afternoon hours.

An area of moderate to heavy rainfall will cross the region
during the day, with the highest amounts (up to around 1 to 1.3
inches across north central and west mass) moving across. There is a
risk for some urban and poor drainage flooding in any heavy
downpours. Could also see some issues along some of the mainstem
rivers, especially along the Connecticut River where the higher
precipitation is expected to fall. Have held off issuing a Flood
Watch at this point, but will continue to monitor this aspect
closely.

Will see temps reach to lower-mid 50s across central and
southern areas, but remain in the upper 40s across the higher
terrain.

&&

Long term /Tuesday night through Sunday/...
highlights...

* blustery and colder Wed, and especially Thu/Fri, but dry
* much milder next weekend with showers possible by Sunday

Tuesday night...

Cold front will be in the vicinity of the cape/islands Tue evening
then moving offshore. Some lingering showers are possible here
early, and a few rain to snow showers possible western Massachusetts in the
evening as mid level trough swings through. Otherwise, gradual
clearing will develop although some lower clouds may linger across
northwest Massachusetts. Gusty west winds will develop overnight as low level cold
advection increases.

Wednesday through Friday...

Blustery and colder pattern as longwave trough develops over the NE
but mainly dry weather expected with dry column and subsidence. Near
normal temps Wed, then trending below normal Thu/Fri. Core of the
coldest air aloft on Thu with 850 mb temps near -15c. This will
result in highs Thu mainly in the 20s to near 30 with gusty winds
making it feel considerably colder, while Thu night wind chills drop
into the single numbers and subzero higher terrain. Temps recover
Fri as heights begin to rise and low level temps moderate but a cold
start will hold temps from the upper 20s to mid 30s.

Saturday and Sunday...

Return to milder airmass and well above normal temps as high pres
moves offshore and mid level ridge builds north along the East
Coast. 850 mb temp anomalies 1-2sd and eps/gefs ensembles have
fairly high probs of 50s in the coastal plain by sun. Deterministic
GFS looks too fast with next approaching trough and not supported by
majority of gefs members so we leaned toward slower ecwmf solution
given downstream ridging in place over the western Atlantic. Next
chance of showers assocd with the mid level trough and attending
cold front should hold off until Sunday or possibly Sat night. Very
low risk of some icing distant interior if precip comes in Sat night
but any freezing precip would probably be localized and this is
a very low probability.

&&

Aviation /15z Monday through Friday/...
forecaster confidence levels...

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

Short term /through Tuesday/...

Today...moderate confidence. Mainly IFR with localized LIFR
conditions in areas of fog, drizzle and showers. Localized
-fzra/fzdz remains possible across parts of interior
Massachusetts...especially the high terrain.

Tonight...low to moderate confidence.
MVFR-IFR ceilings for most areas. Rain most places with -fzra
across north central and northwest mass as winds shift to east- there. Across
S areas, winds shift to S and increase after midnight, with
ceilings lifting to VFR but MVFR-IFR visibilities linger in patchy fog.

Tuesday...moderate confidence.
Mix of conditions from locally VFR to start across north CT/RI/se
mass, ranging to IFR across north central and west mass. Conditions
lower to MVFR-IFR as cold front approaches, bringing low clouds
and areas of locally heavy rain. Low chance of thunderstorms and rain. Depending
upon the timing of the cold front, conditions may improve to VFR
across western areas during the afternoon.

Kbos terminal...moderate to high confidence in taf.

Kbdl terminal...moderate to high confidence in taf.

Outlook /Tuesday night through Friday/...

Tuesday night: mainly VFR, with local MVFR/IFR possible in the
evening across cape/islands. Windy with gusts to 30 kt. Slight
chance rain showers in the evening.

Wednesday: VFR. Windy with gusts to 30 kt.

Wednesday night through friday: VFR. Breezy.

&&

Marine...
forecaster confidence levels...

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

Short term /through Tuesday/...moderate confidence.

Today...
light east-southeast winds increase to around 10 kt during the day. Seas
build up to 2-3 ft. Visibility reduced to around 3 miles during
the afternoon in rain and fog.

Tonight...
wind shift to southeast-S during the night, with gusts increasing to
20-25 kt. Seas build to 3-5 ft on the outer waters after
midnight. Visibility lowering to 1-3 miles in rain and fog.

Tuesday...
Gale Warning issued for all waters. S winds increase, gusting up
to 35-40 kt, highest from mid morning through the afternoon.
Seas build up to 6-9 ft. Visibility 1-3 miles in rain and fog.
Chance for isolated thunderstorm.

Outlook /Tuesday night through Friday/...

Tuesday night: low risk for gale force winds with gusts up to
35 kt. Rough seas up to 12 ft. Slight chance of rain showers.

Wednesday: moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 11 ft.

Wednesday night: low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas.

Thursday through Thursday night: moderate risk for Small Craft
Advisory winds with gusts up to 30 kt. Areas of rough seas.

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

&&

Hydrology...
a Flood Warning remains in effect for the Connecticut River at
Middle Haddam, where ice jams are causing river fluctuations.
No significant change from earlier forecasts.

For details on specific area rivers, including observed and
forecast river stages, please visit the advanced hydrologic
prediction service (ahps) graphs on our website.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...Winter Weather Advisory until 9 am EST Tuesday for maz002>004-
008-026.
Rhode Island...none.
Marine...Gale Warning from 9 am to 8 PM EST Tuesday for anz232>235-237-
250-254>256.
Gale Warning from 10 am to 6 PM EST Tuesday for anz230-231-236-
251.

&&

$$
Synopsis...kjc
near term...Frank
short term...evt

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