Flood Potential Outlook
Issued by NWS Boston, MA

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CTC003-013-015-MAC001-005-007-009-011-013-015-017-019-021-023-025-
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Winter/Spring Flood Potential Outlook
National Weather Service TAUNTON MA
542 PM EST Thu Jan 18 2018

...Ongoing flooding due to ice jams on the lower Connecticut
River...
...Winter/Spring Flood Potential not related to ice jams is near
normal...

Flooding due to ice jams is ongoing along the lower Connecticut
River in Connecticut. An ice jam is also frozen in place on the
Millers River in Athol. Other than ice jam related flooding, the
winter/spring flood potential for southern New England is near
normal.

The following web site has a map depicting the flood potential
outlook...http://www.weather.gov/nerfc/springfloodpotential
Please note this graphic does not account for ice jam flooding.

This is the second winter/spring flood potential outlook of the
2018 season. This outlook is based on current and forecast
hydrometeorological conditions. This includes snow cover and snow
water equivalent, stream and river levels and the amount of ice
coverage, recent precipitation and temperatures, and expected
temperatures and precipitation over the next two weeks.

...Recent Precipitation and Temperatures...

January 2018 brought very large swings in temperatures and
weather conditions. During the first full week of the month there
was a period of exceptional cold, a continuation from cold that
began during the end of December 2017. These cold temperatures
coinciding with the lowest sun angle of the year enabled a
considerable amount of river ice to quickly develop, estimated to
be 8 to 14 inches thick.

During January 4th an intense Nor`easter brought significant
snowfall to southern New England. Snowfall totals ranged from 10
to 15 inches across much of the area, with locally higher totals
along eastern MA, and lower totals across far northwest MA, the
Cape and Islands. Continued bitter cold allowed the snow pack to
remain in place for a week. The water equivalent of that snow
pack was around 2 inches.

Then during January 11th to the 13th, unseasonably warm air
advanced into the area. Temperatures soared into the 50s and 60s,
accompanied by a strong south wind which eradicated the snowpack
almost in its entirety. On top of the snowmelt, during the 12th to
13th, 1 to 3 inches of rainfall occurred, with higher rainfall
totals of 3 to 3.5 inches across portions of RI and south coastal
MA. Areas of poor drainage flooding and minor river and stream
flooding occurred. In addition to this flooding, breakup of the
river ice occurred, and most of the ice flushed down rivers and
streams. This did result in ice jam formation in some areas,
including but not limited to the lower Connecticut River in CT,
and on the Millers River in Athol.

...Observed snow depths and water equivalents...

Across RI, north central to northeast CT and eastern MA, snow
depth as of January 18th ranged from a few inches to bare ground,
with snow water equivalent ranging from zero to less than an
inch. Across central MA westward to the east slopes of the
Berkshires, snow depth ranged mainly from 3 to 8 inches, with some
locales reporting bare ground, and some higher terrain locales
reporting around a 10 inch snow depth. Snow water equivalent was
an inch or less for most locales, except some 1 to 2 inch
equivalents across the higher terrain of the east slopes of the
Berkshires.

Snow water equivalent was below normal for mid-January.

...River and Ice Conditions...

Much of the river ice that developed was flushed down rivers and
streams. This did result in ice jam formation in some areas.
Active ice jam locations include, but may not be limited to, the
jams listed below.

1. Millers River at Athol- Ice jam existing at the South Main Street
Bridge. This ice jam caused flooding in the vicinity of the ice
jam. The ice jam caused flooding of some buildings in the vicinity.
Water levels were reported to have fallen by a few feet since the
ice jam formed.

2. Lower Connecticut River, near Haddam and points south- NASA
Modis satellite imagery indicates that there are 2 ice jams frozen
in place on the lower Connecticut River. The longer of the two
originates at the East Haddam Bridge and is several miles long.
The second ice field is located further south along the river
channel. A Flood Warning remains in effect for the lower
Connecticut River. The river level is expected to very slowly
recede over the next few days, but remain above Flood Stage. The
ice jam is restricting the amount of water able to move
downstream. Please refer to the latest River Flood Statements for
the Connecticut River at Middle Haddam for more details.

Other area rivers and streams were at above normal levels for
this time of year.

...Soil Moisture Conditions...

The ground was partially frozen. Real-time USGS groundwater wells
did respond to the heavy rain and snowmelt event on the 11th to
the 13th. Soil moisture was normal to above normal for this time
of year.

...Temperature and Precipitation Outlook...

Dry and cold conditions are forecast thru Friday night, then
milder air is expected to move into the area. Highs on Saturday
and Sunday are expected to range from the 40s to low 50s, with
temperatures falling below freezing each night. This will allow
for a gradual snowmelt.

The next chance for significant precipitation is next Monday and
Tuesday. While this is expected to be mainly a rain event, some
wintry precipitation may also occur. Around an inch or so of
rainfall is possible. Dry and seasonably cold weather then returns
for next Wednesday and Thursday.

The week 2 outlook from the Climate Prediction Center, for
January 26 thru Feb 1, calls for above normal temperatures and
above normal precipitation.

...Summary...

Flooding due to ice jams is ongoing on the lower Connecticut River
in Connecticut. There is also an ice jam in place on the Millers
River in Athol. It is difficult to determine the fate of the ice
jams in place. Being mid-January, the sun angle is still low. A
higher sun angle (like what we see in March) can help ice to rot
and flush out. The weekend warmth and moderate rain for early
next week may cause some of the ice to move. This is a situation
that will need to be closely monitored.

Other than the threat for ice jams, based on information
available at this time, the winter/spring flood potential is near
normal across southern New England. River levels are running above
normal, but snow pack is below normal.

Keep in mind that heavy rain can cause flooding any time of the
year. Those with interests along rivers and streams should check
the Hazardous Weather Outlook, which highlights any potential
flood events over the next 7 days. Go to http://weather.gov/boston
and click on the option Hazards, then click on Local Outlook.

$$

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