Flood Potential Outlook
Issued by NWS Raleigh/Durham, NC

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FGUS72 KRAH 021118


Precipitation Summary

Rainfall over the past two weeks has been near normal across Central
NC, slightly below normal along the SC border and slightly above
over far NW NC and between Charlotte and Rocky Mount. There have
been three precipitation events the second half of March, two of
which produced about an inch of rain over Raleigh and Greensboro.
Both events produced lesser amounts over Fayetteville, between half
an inch and an inch. The most recent significant rainfall event was
on the 25th/26th of March.

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 2017

    Month                RDU            GSO        Fayetteville

  October             4.29/ 1.04     3.03/-0.10     2.76/-0.45
  November            1.28/-1.84     0.95/-2.16     0.54/-2.23
  December            2.29/-0.78     1.60/-1.38     2.97/ 0.32
  January             3.92/ 0.42     3.65/ 0.59     3.08/-0.22
  February            1.70/-1.53     2.56/-0.40     1.62/-1.14
  March               4.80/ 0.69     4.32/ 0.59     2.87/-0.68

Total precip         18.28/-2.00    16.11/-2.86    13.84/-4.40
Percent normal            90             85             76

Streamflow and lake levels

Streamflow on unregulated streams and rivers across central NC
were almost all showing flows for the month of February in the below
normal (10-24th percentile) to much-below-normal (<10th percentile)
range. The trend was a gradual decline as the month progressed, as
rainfall was sparse in the latter half of the month. Over the past
two weeks, as of March 31st, most streams and rivers were in the 25-
75 percent of normal range, with just a few remaining in the below
to much below range.

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 was 252.7 feet, an increase of 1.9 feet since
March 1st. That puts Falls 1.2 feet above guide curve (251.5 feet).
Jordan Lake elevation was 217.5, which is an increase of 0.6 feet
since the 1st. That puts Jordan at 1.5 feet above guide curve

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

Short term forecast

The weather pattern favors progressive systems for the next two
weeks, and models suggest that several systems could potentially
provide modest to significant rainfall to the area. At this time,
none appear potent enough to produce a widespread 2-3 inches, which
current near normal hydrologic conditions would require to produce
flooding of significance on larger streams and rivers.

Longer term precipitation outlook

We are currently in a weak to moderate La Nina phase of the El
Nino/Southern Oscillation (ENSO) cycle, which is expected to
transition to ENSO-neutral over the next month or so. This is
the `warm` ENSO phase, which typically produces increased chances
of warmer-than-normal temperatures and less-than-normal
precipitation. This weakening climatological signal suggests
that the longer range chance of river flooding is normal to
slightly 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 near normal across
central NC. There is potential for weather systems in the near-term
forecast which could produce precipitation significant enough to
cause minor river flooding through mid March. There are no
climatological signals suggesting higher-probability wet periods in
the longer range outlook. As such, the chance of flooding through
early Spring is normal to slightly below normal.

This will be the final scheduled Spring flood outlook for 2018.

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

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