Flood Potential Outlook
Issued by NWS Binghamton, NY

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Winter/Spring Flood Potential Outlook
National Weather Service Binghamton NY
900 AM EDT Thu Apr 12 2018

...AVERAGE FLOOD POTENTIAL FOR THE REST OF APRIL...

This is the eighth, and final, in the series of regularly
scheduled hydrologic outlooks issued during the Winter and Spring
season. This outlook is designed to provide a generalized
assessment of river flood potential (not flash flooding) across
Central New York and Northeast Pennsylvania for the next two
weeks...April 12th through April 26th.

...SUMMARY...

The Spring flood potential for central New York and northeast
Pennsylvania is considered about average across the major basins
for the next two weeks. When ground and river conditions are
considered normal, it typically takes in excess of 2 inches within
48 hours to cause flooding.

...CURRENT CONDITIONS...

.PRECIPITATION: Near to Below average. The past two weeks have
seen approximately 1 to 2 inches of rainfall in the region, with
locally higher amounts found across the Western Mohawk valley.
This is roughly only 25 to 75 percent of normal for the Finger
Lakes, Chemung and Upper Main Stem Susquehanna basins, but closer
to 80 to 110 percent of normal elsewhere.

.SNOW COVER AND WATER EQUIVALENT: Near normal. Most of the region
had little to no snow cover which is normal. There were areas of
snow reported in the deeper woods of the Tully-Heibergs and
Catskills which is a bit above normal for mid-April. Liquid
equivalent in the snow pack was generally less than an inch, and
should be an insignificant contribution to runoff.

.RIVER ICE COVER: Normal. The river ice season has passed.

.STREAMFLOW: Normal. Streamflow, averaged over the past week, was
generally normal for early April when compared to the long term
history of each gauge.

.SOILS AND GROUNDWATER: Normal to above normal. The Palmer
Drought Severity Index, along with other multi-model soil moisture
indicators, showed wetter than average deep soil conditions in
the Finger Lakes/Oswego basin. Elsewhere, soil moisture was damp,
which is generally normal for early April. A majority of
groundwater index stations were reporting below normal to normal
levels.

.RESERVOIR AND LAKE LEVELS...Normal. NYC Reservoirs, the Finger
Lakes, and Lake Wallenpaupack were all generally considered to be
within average pool elevations for this time of year.

...FORECAST OUTLOOK...

.FUTURE WEATHER CONDITIONS: The official 6 to 14 day outlook
calls for colder than normal temperatures and above average
precipitation. Long range atmospheric model, and ensemble,
guidance suggested a similar forecast, although focused on the
wetter than normal period being during the first week of the
outlook. Medium to long range weather models indicated the
potential for a period of moderate to heavy rainfall from April
15-17.

.LONG RANGE RIVER MODELING AND PROBABILITY FORECASTS: The
ensemble of river forecast systems was indicating a slight chance
for minor flooding on several rivers in central New York, mainly
as a result of the rainfall expected during the first few days of
this outlook period.

A further analysis of flooding, using current hydrologic
conditions compared to historical flows, suggested a below average
risk of flooding across most of the region for the remainder of
April and early May, except across the East and West branches of
the Upper Delaware basin where the flood potential was ranked
slightly higher.

...IN CONCLUSION...

This outlook estimates the potential for river and lake flooding
based on a current overview of hydro-meteorological factors which
contribute to flooding.

It is important to note that significant flooding does not occur
from snow melt alone. Rainfall, how much and in how short a period
of time, is the most important factor in determining the severity
of flooding. Specific forecasts of heavy rainfall and flash
flooding are not included in this outlook.

This is the last outlook for the season. The next Winter/Spring
Flood Outlook will be issued by this office in January 2019.

$$

JAB



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