Flood Potential Outlook
Issued by NWS Blacksburg, VA

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Winter/Spring Flood Potential Outlook
National Weather Service Blacksburg VA
1155 AM EST Fri Feb 8 2019

...Winter/Spring Flood Outlook...Number 3

...River flood potential slightly above normal...

Each winter and early spring, the National Weather Service office
in Blacksburg issues a series of routine flood potential
outlooks. These outlooks estimate the potential for river flooding
(not flash flooding) across the Blacksburg office`s Hydrologic
Service Area (HSA). The HSA includes 40 counties covering parts of
southwest Virginia, far northwest North Carolina and far
southeast West Virginia. Major river basins in the HSA include all
or parts of the New, Greenbrier, Tennessee, James, Roanoke, Dan,
and Yadkin. This outlook is based on the current assessment of
hydrometeorological factors which contribute to river flooding.
These factors include, but are not limited to, recent
precipitation, soil moisture, snow cover and snow water
equivalent, stream flows, river ice and expected future weather
conditions.

In this part of the southern Appalachian and Mid-Atlantic region,
heavy rainfall is the primary factor that leads to river
flooding. Heavy rainfall can rapidly cause river flooding at any
time of the year, even when overall river flood potential is
considered low.

Flood Potential Outlook:
For the Blacksburg HSA, the river flood potential is slightly
above normal through the period, due primarily to a rain event
expected early next week.

Current Flooding:
No flooding is occurring at this time.

Recent Precipitation:
Precipitation since February 1st has ranged from less than 0.10
inches in the lower Roanoke and Dan river basins up to 1.5 inches
in parts of the upper Tennessee basin. Most areas have seen
around 0.25 to 0.50 inches of rain. Temperatures have been
extremely mild with no snow.

January precipitation was slightly above average with a mean
of 3.73 inches versus the long-term (1981-2010) normal mean
of 3.32 inches or 112 percent of normal.

Conditions were very wet from October through December 2018
with precipitation roughly 150 to 200 percent of the long-term
averages across the entire HSA.

Drought:
There is no drought at this time and none is expected to develop
during the outlook period.

Please visit the www.droughtmonitor.unl.edu/ for access to the
drought maps and additional information.

Snow cover:
There is no snow even in the highest elevations after the record
warmth this past week.

Please visit www.nohrsc.noaa.gov for detailed information on snow
cover and snow water equivalent.

River ice:
There is no river ice anywhere in the HSA at this time.

Streamflow:
USGS real-time streamflows at 14-day and 28-day averages are
nearly all indicating above-normal flows and in the near average
range at shorter durations from 1-day through 7-days.

For more detailed information on streamflow conditions see the
USGS WaterWatch website: https://waterwatch.usgs.gov

Soil Moisture:
Soil moisture analyses from the Climate Prediction Center (CPC)
indicate continued moisture surpluses ranging from 3.0 to 4.0
inches above normal across the entire HSA.

For additional soil moisture information see:
http://www.cpc.ncep.noaa.gov

Reservoirs:
Major water supply reservoirs, including John H. Kerr, W. Kerr
Scott, Philpott Lake, Lake Moomaw and the Roanoke area reservoirs
of Carvins Cove and Spring Hollow, are near or above average or
guide curves where applicable.

Future Weather Conditions:
Quantitative precipitation forecasts (QPF) from the Weather
Prediction Center (WPC) over the next 7 days (through 7 AM Friday,
February 15th) indicate amounts ranging from about 1 to 2 inches
across the HSA, with isolated higher amounts possible in the
western mountain basins. While these totals are somewhat above
normal they present only a minor flood threat. This forecast will
likely be refined as the system approaches the region late in the
weekend into early next week.

WPC QPF is updated frequently and is available at:
www.wpc.ncep.noaa.gov/#page=qpf

The longer term outlooks for the 6 to 10 and 8 to 14 day periods
through February 21st higher chances for both temperatures and
precipitation to be well above normal as a strong ridge over the
southeastern U.S. maintains a warm and fairly moist pattern in
place.

For additional long range forecast information see:
http://www.cpc.ncep.noaa.gov

Probabilistic/Ensemble river forecasts:
The Meteorological Model Ensemble River Forecasts (MMEFS) valid
through about February 15th indicate a slight potential for river
flooding due to the incoming rainfall event mainly in the Dan and
lower Roanoke river basins. Rises to near Action stage are also
possible on the James and New River basins.

Ensemble river forecasts (MMEFS) are available at:
www.weather.gov/erh/mmefs

Summary:
For the Blacksburg HSA, the river flood potential is slightly
above normal through the period.

Next issuance:
The next winter/spring flood potential outlook will be issued on
or around Thursday, February 21st, 2019. An outlook may be issued
before then if conditions warrant.

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

$$

pc



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