Flood Potential Outlook
Issued by NWS Raleigh/Durham, NC

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Winter/Spring Flood Potential Outlook
National Weather Service Raleigh, NC
1230 PM EST Wed Jan 11 2017

...THE CHANCE OF RIVER FLOODING FROM MID JANUARY THROUGH SPRING IS
NEAR NORMAL...

Precipitation Summary

To date, hurricane Matthew was the major rain-producing system for
eastern North Carolina this Fall/Winter season. Up to 20 inches of
rain fell over eastern NC in early October, with amounts tapering
off quickly to only a couple of inches westward into the western
Piedmont. This was fortuitous, as rainfall was well below normal in
the weeks following Matthew (Oct 10 through Dec 3). Near-normal
rainfall resumed in December and has continued into early 2017.

See www.water.weather.gov for detailed rainfall analysis.

Precipitation and departure from normal:

          Precipitation (inches) and departure from normal
            for the water year beginning 1 October 2016

    Month                RDU            GSO        Fayetteville
------------------------------------------------------------------

  October             7.10/ 3.85     3.91/ 0.78    15.07/11.81
  November            0.60/-2.52     1.02/-2.09     0.81/-1.96
  December            2.19/-0.88     1.70/-1.28     2.64/-0.01
  January(to date)    2.78/ 1.56     2.15/ 1.06     1.94/ 0.87

Total precip   (YTD) 12.67/ 2.01     8.78/-1.53    20.46/ 9.70
Percent normal (YTD)     119             85            211


                  Begin     Actual   Normal  Departure  Percent
                  date       Pcpn     Pcpn   from norm  of norm

Raleigh-Durham International Airport (RDU)

 Past   7 days   01/04/2017   0.85    0.79      0.06      108%
 Past  14 days   12/28/2016   3.13    1.49      1.64      210%
 Past  30 days   12/12/2016   3.68    3.07      0.61      120%
 Past  90 days   10/13/2016   5.71    9.22     -3.51       62%
 Past 180 days   07/15/2016  24.14   21.90      2.24      110%
 Past 365 days   01/12/2016  53.76   43.34     10.42      124%

Piedmont Triad International Airport (GSO)

 Past   7 days   01/04/2017   0.70    0.70      0.00      100%
 Past  14 days   12/28/2016   2.33    1.33      1.00      175%
 Past  30 days   12/12/2016   2.66    2.86     -0.20       93%
 Past  90 days   10/13/2016   4.87    8.99     -4.12       54%
 Past 180 days   07/15/2016  16.84   20.85     -4.01       81%
 Past 365 days   01/12/2016  41.41   42.21     -0.80       98%

Fayetteville Airport (FAY)

 Past   7 days   01/04/2017   0.99    0.69      0.30      143%
 Past  14 days   12/28/2016   2.44    1.23      1.21      198%
 Past  30 days   12/12/2016   3.59    2.48      1.11      145%
 Past  90 days   10/13/2016   5.39    7.88     -2.49       68%
 Past 180 days   07/15/2016  34.22   22.96     11.26      149%
 Past 365 days   01/12/2016  57.93   44.44     13.49      130%

Streamflow and lake levels

Timing and distribution of precipitation events has been fairly
regular over the past few weeks. Thus, streams and rivers across
central NC are flowing in the normal range for the time of year
except for a few sites in the northwest (the Yadkin river basin)
where an 8 to 12 inch snowfall from a recent winter storm has yet
to melt.

See https://waterwatch.usgs.gov for additional details.

The major water supply and flood control reservoirs in central NC
are Falls Lake and B. Everett Jordan Lake, both operated by the U.S.
Army Corps of Engineers. Falls Lake elevation is at 251.9 feet,
which is half a foot above its target elevation. B. Everett Jordan
Lake elevation is 216.9 feet, a foot above target elevation. As
such, water allocations for water supply and power generation are
100 percent at both lakes, with ~98% of flood storage available
should that capacity be needed.

See www.epec.saw.usace.army.mil for additional details.

Short term forecast

The ongoing cycle of regular frontal passages and associated
precipitation events is expected through mid January. The next
potentially significant precipitation event is not expected until
next Wednesday the 18th. Sub-freezing air will be blocked north of
the area through the period, and this system will be liquid, perhaps
ranging up to a widespread half to one inch of rain.

Longer term precipitation outlook

We are currently in a weakening La Nina phase of the El
Nino/Southern Oscillation (ENSO) cycle. A pronounced La Nina
typically produces an increased chance for warmer and drier than
normal conditions during the winter/spring over central NC. As the
La Nina phase is expected to continue weakening and become neutral
over the next 1-2 months, the tendency towards drier conditions will
be diminishing as well. With the antecedent near normal moisture
conditions and a weak climatological signal favoring drier
conditions, the longer range chance of river flooding is near
normal.

Additional details and discussion may be found at the Climate
Prediction Center website: http://www.cpc.ncep.noaa.gov

In summary, current hydrologic conditions are near normal across
central NC. There are no strong systems looming in the near term
forecast and no strong climatological signals which might point
towards a prolonged wet periods in the longer range outlook. As
such, the chance of river flooding is near normal.

The next scheduled Winter/Spring flood outlook will be issued
on January 19th.

For additional hydrologic or weather information, visit our website
at www.weather.gov/raleigh.

MLM



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