Flood Potential Outlook
Issued by NWS Raleigh/Durham, NC

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Winter/Spring Flood Potential Outlook
National Weather Service Raleigh, NC
1210 PM EST Fri Mar 3 2017

...THE CHANCE OF RIVER FLOODING FOR THE REMAINDER OF WINTER THROUGH
SPRING IS BELOW NORMAL...

Precipitation Summary

Precipitation was meager over central NC during the past 4 weeks,
and few locations received as much as one inch of liquid water
equivalent. If we disregard the anomalous rainfall from hurricane
Matthew in early October, all of central NC has received 75 to 90
percent of normal precipitation for the water year. Temperatures
have been well above normal for the past month, with average daily
temperatures for February ranging from 8 to 9 degrees above normal.
The anomalously warm temperatures have spurred the onset of the
growing season several weeks early, and the additional need for
water by emerging plants will lessen runoff, especially from rain
events of light to moderate intensity and longer duration.

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             3.77/ 0.27     5.12/ 2.06     2.43/-0.87
  February            0.66/-2.57     0.49/-2.47     0.99/-1.77

Total precip         14.32/-1.85    12.24/-3.00    21.94/ 7.20
Percent normal            89             80            149
---------------------------------------------------------------

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

Raleigh-Durham International Airport (RDU)

 LAST   7 DAYS   02/24/2017   0.97    0.87      0.10      111%
 LAST  14 DAYS   02/17/2017   0.97    1.71     -0.74       57%
 LAST  30 DAYS   02/01/2017   1.63    3.49     -1.86       47%
 LAST  90 DAYS   12/03/2016   7.59    9.86     -2.27       77%
 LAST 180 DAYS   09/04/2016  18.32   20.31     -1.99       90%
 LAST 365 DAYS   03/03/2016  50.14   43.34      6.80      116%

PIEDMONT TRIAD INTERNATIONAL AIRPORT (GSO)

 LAST   7 DAYS   02/24/2017   0.85    0.81      0.04      105%
 LAST  14 DAYS   02/17/2017   0.96    1.59     -0.63       60%
 LAST  30 DAYS   02/01/2017   1.30    3.19     -1.89       41%
 LAST  90 DAYS   12/03/2016   8.12    9.02     -0.90       90%
 LAST 180 DAYS   09/04/2016  15.18   19.21     -4.03       79%
 LAST 365 DAYS   03/03/2016  39.81   42.20     -2.39       94%

FAYETTEVILLE AIRPORT (FAY)

 LAST   7 DAYS   02/24/2017   0.67    0.69     -0.02       97%
 LAST  14 DAYS   02/17/2017   0.67    1.45     -0.78       46%
 LAST  30 DAYS   02/01/2017   1.66    2.97     -1.31       56%
 LAST  90 DAYS   12/03/2016   6.73    8.69     -1.96       77%
 LAST 180 DAYS   09/04/2016  29.53   18.87     10.66      156%
 LAST 365 DAYS   03/03/2016  52.47   44.46      8.01      118%


Streamflow and lake levels

Streamflow on streams and rivers across central NC had fallen off
precipitously during February, and by month`s end nearly every
stream had flows below the 10th percentile for the date. A fairly
widespread rain event with amounts ranging from 1 to 1.5 inches
on March 1st lifted flow readings into the 25th percentile range.
This bump in stream levels will fall off quickly, however, given
expected continuation of lighter and relatively infrequent nature
of rain events through mid March.

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 a bit above its target elevation of 251.5 feet. B. Everett
Jordan Lake elevation is 216.6 feet, also above the target elevation
of 216 feet. 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

Temperatures will remain above normal over the next two weeks, with
two or perhaps three systems affecting the area which might have a
chance of producing significant precipitation. It would require as
much as 3 inches of widespread rain to cause river flooding of
significance. Given the relative speed upcoming systems, they are
unlikely to produce widespread rainfall capable of causing flooding.

Longer term precipitation outlook

We are currently in a neutral phase of the El Nino/Southern
Oscillation (ENSO) cycle, which provides no climatological
signal upon which to base a seasonal outlook. Thus, given the
persistent dryness in place and a basic `climatological` outlook,
the longer range chance of river flooding is considered below 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 drier than normal
across central NC. There no hints of any system in the near-term
which would be capable of producing significant rain, thus there is
a below normal chance for flooding through mid March. Similarly,
there are no climatological signals which might point towards
prolonged wet periods in the longer range outlook, so the chance
of flooding through the late winter and early spring is also below
normal.

The next scheduled Winter/Spring flood outlook will be issued
on March 16th.

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

MLM



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