Flood Potential Outlook
Issued by NWS Buffalo, NY

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Winter/Spring Flood Potential Outlook
National Weather Service Buffalo NY
529 PM EDT Thu Mar 16 2017

...NEAR NORMAL FLOOD RISK...

This is the sixth flood potential outlook of the 2017 season.
Flood outlooks will be issued every two weeks into early spring to
summarize basin conditions and to assess the potential for
flooding. The outlooks are based on current and forecast
hydrometeorological conditions. This includes snow cover and
water equivalent, creek and river levels and the amount of ice on
them, along with the expected conditions during the next two
weeks.

...CURRENT CONDITIONS SUMMARY...

A warm pattern which lasted for much of February and into the
first week of March melted nearly all the snow which fell during
the heart of winter. Only the deepest of snows on the Tug Hill
and Western Adirondacks lasted through this warm pattern, which
also melted nearly all the river and creek ice.

Since then, temperatures have been well below normal during the past
week. Some light lake effect snow followed by a widespread snowfall
from a powerful mid-March system has helped reestablish the snowpack.
Most of the snow on the ground is from this one snowstorm, with
relatively uniform snowfall amounts and snow water equivalent (SWE)
values in the 1 to 2 inch range. There is a bit more snow in the
Black River basin due to lake effect snow and left over snow
from earlier in the season. Snow water amounts vary greatly in
the Black River Basin. In general, the higher SWE amounts are
isolated and only cover less than 10 percent of the overall basin,
with lesser amounts more commonplace.

SWE in the Black River basin only about two-thirds of normal with
the snowpack more fluffy and less ripe than normal since most of it
fell in the last week. Elsewhere, this storm was enough to replenish
snow pack to near to even slightly above normal levels.

The following is a summary of the conditions by basin as of
Thursday morning, March 16th:

...BUFFALO AREA CREEKS / LAKE ERIE BASIN...
.SNOW COVER..........10 to 16 inches.
.WATER EQUIVALENT....1 to 2 inches.
.CREEK FLOWS.........Below normal.
.CREEK ICE...........Some, mainly thin or along edges.
.GROUND FROST........3 to 6 inches.
.GROUND STATE........Frozen.

...GENESEE RIVER BASIN / FINGER LAKES / ROCHESTER AREA...
.SNOW COVER..........10 to 16 inches.
.WATER EQUIVALENT....1 to 2 inches.
.RIVER/CREEK FLOWS...Below normal.
.RIVER/CREEK ICE.....Patchy.
.GROUND FROST........3 to 6 inches.
.GROUND STATE........Frozen.

...ALLEGHENY RIVER BASIN...
.SNOW COVER..........6 to 12 inches.
.WATER EQUIVALENT....1 to 1.5 inches.
.RIVER/CREEK FLOWS...Below normal.
.RIVER CREEK ICE.....Some, mainly thin or on edges.
.GROUND FROST........3 to 6 inches.
.GROUND STATE........Frozen.

...BLACK RIVER BASINS / TUG HILL...
.SNOW COVER..........10 to 20 inches, except 20 to 30 inches on the
Tug Hill and Western Adirondacks.
.WATER EQUIVALENT....Variable. 1 to 3 inches across lower
terrain with 3 to 10 inches on the Tug Hill and Western Adirondacks.
.RIVER/CREEK FLOWS...Below normal.
.RIVER/CREEK ICE.....Mostly frozen, but open areas with variable
thickness.
.GROUND FROST........6 to 12 inches.
.GROUND STATE........Frozen.

...TEMPERATURE AND PRECIPITATION OUTLOOK...

A weak system will bring generally light mixed precipitation to the
region on Saturday, followed by dry weather which will last into early
next week. Precipitation amounts from this system will likely run
in the quarter to half inch range. Temperatures will average near
normal through early next week, resulting in a slow and steady
snow melt given the higher March sun angle.

A strong cold front is forecast to cross the region early
Tuesday, with much below normal temperatures likely during middle
and latter portion of next week. Any precipitation that falls
during this period should be snow, with some lake effect snows
possible during this time which could add to the snow pack.

After this, there is moderate forecast confidence that low pressure
will develop across the mid-west and track near the Great Lakes
region on Friday and Saturday. This would bring warmer
temperatures and a period of rainfall to the region. It is still
too early to tell rainfall amounts which will depend on the track
and speed of the system. A period of mainly dry weather is likely
behind this system heading toward the end of March.

The CPC 8 to 14 day outlook is for below normal temperatures an
above normal precipitation. This reflects an average for the entire
period, with most of the precipitation likely to come from one
system...the Great Lakes low forecast to impact the region next
Saturday.

...FLOOD POTENTIAL OUTLOOK...

The flood risk is near normal.

The chance for flooding in minimal during most of the outlook
period, with the primary risk coming with the expected system next
weekend on March 24th and 25th. Before this, weak low pressure will
bring only light precipitation, followed by another period of cold
weather which will pose little risk for flooding. Another factor
is current river and creek flows are below normal.

Looking ahead to next weekend, the forecast track for the system
is favorable to bring in warm temperatures ahead of the system
resulting in some snow melt. Rainfall amounts are highly uncertain
this far out, but a deep trough forecast to be across the nations
mid-section can support heavy rainfall in our region. The risk
from this system offsets the remainder of the outlook period
which has a very low risk for flooding.

...ADDITIONAL INFORMATION...

Real time river information and probabilistic forecast for
specific locations along rivers across Western New York can be
found on the internet at www.weather.gov/buf. Since conditions can
change, please refer to the latest flood watches, warnings, and
statements for additional information.

Thank you to all the observers and agencies which have helped
gather data in support of this outlook. The next Winter/Spring
Flood Outlook will be issued on March 30th.

$$

Apffel



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