Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 161538
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1038 AM EST Tue Jan 16 2018

.SYNOPSIS...
Low pressure moves east from the Great Lakes today, then
redevelops off the Mid Atlantic coast before tracking across SE
New England Wednesday. This will bring several inches of snow
to much of the interior, mainly tonight into Wednesday
afternoon. A changeover to rain is likely Wednesday across
portions of Rhode Island and southeast Massachusetts which will
result in less accumulations here. Mainly dry weather likely
Thursday into Sunday, with a warming trend during the weekend.
Another low pressure system may affect our region early next
week with mostly rain.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

1030 AM Update...

Overall trend in the forecast remains on track for today. Weak
WAA snow showers continue to develop out ahead of the
approaching system. Some sites across eastern NY have lowered
below 3 miles over the past hour, so cannot rule that out when
WAA axis shifts more over western MA and northern CT. Still
waiting for high pressure shift a bit more eastward for this
axis to take over. Thus cannot rule some light snow showers for
the evening commute across the Springfield area.


Previous Discussion...

Some patchy light snow is noted across western MA early this
morning assocd with weak warm advection. Radar showing some
spotty light snow upstream across NY. High pres will be slow to
exit New Eng today so weak warm advection and any light snow
today will remain confined to western MA and portions of
western CT. Accum of a coating to less than an inch is
possible. Otherwise, more clouds than sun expected today.
High will range from the mid/upper 20s interior northern and
western MA to low/mid 30s coastal plain.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...

1030 AM Update...

Latest trends in the hi-res guidance and 12z NAM has this
forecaster a bit concern on snow totals. Warmer air appears to
push a bit farther to the north and west leading to more mixing
and less snow for the I-95 corridor. This makes sense as this
system is quite progressive and a open wave leading to more
warmer air making its way into southern New England. The other
trend we have noticed is how quickly this storm will exit the
region. Thus expect precip to begin to wind down after 21-00z
which would result in less of an impact towards the Wed evening
commute. The morning commute still looks treacherous. Will
continue to evaluate the latest data but that is what the
current trends are showing.


Tonight and Wednesday...

H5 long wave trough remains positively tilted as it slowly but
steadily shifts E. Continue to see a strong jet core, up to
120-130 kt, with right entrance region pushing to the mid
Atlantic coast this evening. The coastal low will take shape off
of the Delmarva peninsula and shift NE, passing across Cape Cod
and the islands around midday or so on Wednesday.

Continue to see best and strongest lift moving across the region
late tonight through around midday Wednesday. Best snow growth
also moves across about that time. 00Z model suite appears to be
in pretty good agreement in bring the low across Cape Cod and
the islands by around 18Z Wed, then will head to the Gulf of
Maine. This will place the best chance for highest snow amounts
across NE, central and W Mass into NW RI and N CT. Some question
on a mix/changeover to rain across SE Mass and central/S RI,
though looking more likely especially across Cape Cod and the
islands.

Models signal slightly lower QPF amounts, in the 0.4 to 0.6
inch range. Snow to liquid ratios of between 12 and 15 to 1
across in the interior, and 10 to 12 to 1 in much of RI and
SE Mass. This continues to support 6 inches or higher pf snow
over much of the region of central and northern areas, with
diminishing amounts south of a Boston-Hartford line due to
temperatures near freezing along with a mix or change to rain.

Have converted Winter Storm Watches to Warnings over much of the
region from Boston into NW RI and all of N central and NE CT N
and W, with Winter Weather Advisories across the remainder of RI
and SE Mass to the N of the Cape Cod Canal. Could see a little
snow on the Cape and islands overnight, but should change to
rain toward daybreak through mid morning Wednesday.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Highlights...

* Cold and dry Thursday
* Continued dry with a warming trend through the weekend
* Another storm may bring mostly rain Monday

Wednesday night and Thursday...

Coastal low over the Gulf of Maine Wed evening will lift into the
Maritimes. Some lingering light snow eastern New Eng is possible
early as sharp mid level trough swings through, otherwise drying
with gradual clearing overnight. Thursday looks dry and cold with a
mix of sun and clouds. Somewhat breezy as well with gusty NW winds
at times. Temps in the mid 20s to lower 30s.

Friday through Sunday...

Looks mainly dry though the weekend. Moderating trend begins
Fri with temps recovering to near seasonable normals then a mild
day Sat with temps in the 40s. Some uncertainty with temps Sun
which will depend on a possible frontal passage. ECMWF further
south with northern stream shortwave across SE Canada which
drives cold front through with high pres building to the north,
while GFS/GGEM/UKMET keep boundary to the north and mild temps.
We leaned toward milder consensus of the guidance, but will have
to monitor this trend as ECMWF would suggest some ice potential
on front end of next shot of precip late Sun night/early Mon.

Monday...

Amplified mid level trough and cold front approaches from the
west with decent pre-frontal low level jet moving into the
region. Timing this far out is uncertain but a period of rain
appears likely sometime Mon into Mon night. One caveat is ECMWF
would suggest some mixed precip/ice would be possible at the
onset with cold high pres to the NE.

&&

.AVIATION /16Z 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/...

Through Today...Moderate confidence. Mainly a mix of MVFR and
VFR cigs. Patchy light snow at times western MA may lower vsbys
to MVFR. Light winds.

Tonight and Wednesday...Moderate confidence. Mainly IFR-LIFR
CIGS/VSBYS in snow, with areas of heavy snow north of a BOS-HFD
line. Snow may mix with or change to rain south of a Marshfield-
Providence-Westerly line during Wed. Conditions improve to VFR
in CT and Western Mass Wednesday afternoon...and in RI and
Eastern/Central Mass Wednesday night. Wind gusts 20-25 knots
around Nantucket and parts of Cape Cod.

KBOS Terminal...Moderate to high confidence in TAF. MVFR CIGS
through 12Z-14Z, then should be mainly VFR through evening
push.

KBDL Terminal...High confidence in TAF. Mainly VFR through 00Z,
then lowering to MVFR-IFR as -SN develops by around 03Z.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Mainly VFR, with local IFR possible in the
evening. Breezy. Slight chance SN.

Thursday through Saturday: VFR. Breezy.

&&

.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.

Through Today...
N winds may briefly gust to 20 kt E and S of Cape Cod through
daybreak, otherwise winds will be below small craft levels.
However, seas across the open waters up to 6-10 ft, mainly on E
swells. Small craft advisories continue.

Tonight...
Expect S-SE winds up to around 10 kt, shift to E after
midnight. Some gusts up to 20 kt toward daybreak across the
southern outer waters. Seas around 5 feet on the outer waters.
Mixed snow and rain developing with reduced visibility. Small
crafts continue.

Wednesday...
East winds with gusts 20 to 25 knots. Seas 5 to 7 feet on the
outer waters and possibly on the RI waters. Rain through the
day, may mix with snow on the eastern nearshore waters toward
evening. Visibility 2 to 4 miles. Small crafts continue.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of snow.

Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas.

Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas.

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

Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft.

Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas.

&&

.HYDROLOGY...
Minor flooding continues along Taunton and Pawcatuck Rivers
where Flood Warnings remain in effect. A Flood Warning is also
in effect for the Connecticut River at Hartford and Middle
Haddam, where ice is causing some river fluctuations.

Colder weather will persist across the river basins through
midweek which will limit additional runoff, along with continued
ice jams on some of the rivers. There will be an increase of
snow pack for much of region today into Wednesday as several
inches of snow will fall.

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...Winter Storm Warning from 1 AM to 6 PM EST Wednesday for
     CTZ004.
     Winter Storm Warning from 7 PM this evening to 3 PM EST
     Wednesday for CTZ002-003.
MA...Winter Weather Advisory from 1 AM to 1 PM EST Wednesday for
     MAZ017>019.
     Winter Storm Warning from 1 AM to 6 PM EST Wednesday for
     MAZ004>007-012>016-026.
     Winter Storm Warning from 7 PM this evening to 3 PM EST
     Wednesday for MAZ002-003-008>011.
     Winter Weather Advisory from 1 AM to 9 AM EST Wednesday for
     MAZ020-021.
RI...Winter Weather Advisory from 1 AM to 1 PM EST Wednesday for
     RIZ002>004.
     Winter Storm Warning from 1 AM to 6 PM EST Wednesday for
     RIZ001.
     Winter Weather Advisory from 1 AM to 9 AM EST Wednesday for
     RIZ005>007.
MARINE...Small Craft Advisory until 5 PM EST this afternoon for ANZ231.
     Small Craft Advisory until 6 PM EST Wednesday for ANZ250-
     254>256.
     Small Craft Advisory until 1 AM EST Wednesday for ANZ251.

&&

$$
SYNOPSIS...KJC/EVT
NEAR TERM...KJC/Dunten
SHORT TERM...Dunten/EVT
LONG TERM...KJC
AVIATION...KJC/EVT
MARINE...KJC/EVT
HYDROLOGY...staff


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