Flood Potential Outlook
Issued by NWS Wakefield, VA

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Winter/Spring Flood Potential Outlook
National Weather Service WAKEFIELD VA
443 PM EST Thu Feb 15 2018

...Fourth Winter/Spring Flood Outlook for 2018...

...River Flood Potential is normal to below normal through March
1st...

Each winter and early spring, the National Weather Service office
in Wakefield, VA issues a series of flood potential outlooks.
These outlooks estimate the potential for river flooding across
the Wakefield Forecast Office`s Hydrologic Service Area (HSA).
The HSA includes Central and Eastern Virginia, the Lower Maryland
Eastern Shore, and portions of Northeast North Carolina. The
outlook is based on the current assessment of hydrometeorological
factors which contribute to river flooding. These factors
include, but are not limited too recent precipitation, soil
moisture, snow cover and snow water equivalent, stream flows,
river ice and expected future weather conditions.

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

The following is a summary of the current conditions as of 3 PM
Thursday February 15 2018:

Current flooding - No rivers are currently in flood as of 3 PM
Thursday February 15 2018.

Recent precipitation - Over the last 30 days from January 16 2018
to February 15 2018, the precipitation has ranged from 3" to
6.50" with the lowest amounts of 3" - 4" across eastern portions
of the Chowan Basin and coastal regions of Virginia and North
Carolina. These totals were near normal for the 30 day period.
The remainder of the area saw totals of 4" - 6.50" which were up to
3" above normal. The CoCoRaHS observer just south of Gordonsville
reported 6.47" in the 30 day period.

Looking back to the beginning of the water year through February
15th, the rain totals generally range from 9"- 17" with the
deficits of 2" - 6" across the Appomattox Basin and Chowan
Basins. Wallops Island VA reported 16.13 since the beginning of
the water year which is nearly 2.3" above normal and this is the
highest total across the HSA since Oct 1.

Snow conditions - Currently there is no snow on the ground in the
Wakefield HSA.

River ice conditions - Currently there is no ice on area rivers.

Stream Flow Conditions - The 14 day average stream flows, through
February 15th, continued to show improvement from previous
outlooks with all gages showing normal to above normal except for
3 gages in Virginia which are below normal. Two of those gages
were in the Southern Virginia Piedmont counties where moderate
drought continues to be depicted in the US Drought Monitor.

When looking at the real time flows as of 3 PM February 15th, the
river levels are generally in the normal to above normal range.
The Chowan basin has the only gages that are below normal in the
real time flows and there are 5 gages reading below normal. Much
of that is due to missing out on the bulk of the rain over the
last two weeks where departures are up to 1" below normal.. Here
are some real time stream flows as of 3 PM February 15th:

LOCATION OBSERVED LEVEL/MEDIAN FLOW/PERCENTAGE OF MEDIAN
RIVANNA RIVER
PALMYRA VA 1070 CFS/ 670 CFS/159.7
JAMES RIVER
CARTERSVILLE VA   15800 CFS/7150 CFS/221.0
RICHMOND VA   18600 CFS/7000 CFS/265.7
APPOMATTOX RIVER
    FARMVILLE VA   229 CFS/ 269 CFS/    85.1
MATTOAX VA     653 CFS/ 720 CFS/ 90.7
    MATOACA VA    1490 CFS/1260 CFS/109.6
NOTTOWAY RIVER
    RAWLINGS VA     284 CFS/    319 CFS/    89.0
    STONY CREEK VA     452 CFS/    700 CFS/    64.6
    SEBRELL VA    1310 CFS/   2180 CFS/    60.1
MEHERRIN RIVER
    LAWRENCEVILLE VA      403 CFS/    538 CFS/    74.9
    EMPORIA VA      482 CFS/    752 CFS/    64.1
BLACKWATER RIVER
    FRANKLIN VA     637 CFS/   1060 CFS/    60.1
MATTAPONI RIVER
    BOWLING GREEN VA     927 CFS/    283 CFS/   292.2
    BEULAHVILLE VA    2930 CFS/    740 CFS/   395.9
POCOMOKE RIVER
    WILLARDS MD     132 CFS/     96 CFS/   137.5
POTECASI CREEK
    UNION NC     157 CFS/    339 CFS/    46.3

Soil Moisture Conditions - Normal to below normal.

Soil moisture indicators including the Palmer Drought Severity
Index, which is used to infer deep soil moisture and long term
drought, shows that as of February 10 2017, the Wakefield HSA, is
depicted as being near normal for deep soil moisture.

The CPC Soil Moisture Monitor, which looks more at top soil
moisture, has continued to show some improvement over the last
two weeks. The deficits over the central Piedmont of Virginia have
dropped into the -40mm - -60mm range after being near -100m just 2
weeks ago. Minor deficits of -20 - -40 mm continue across Eastern
portions of VA and Northeast NC. Meanwhile the Delmarva Peninsula
is in the normal range for top soil moisture.

Ground Water - NORMAL TO BELOW NORMAL LEVELS.

Ground water levels across the HSA are in the normal to above
range along the coastal portions of the Wakefield HSA. However,
further inland across Virginia, including the Piedmont counties,
the ground water levels are running below normal to much below
normal. But thanks in part to recent rains, the water levels have
begun to rise indicating that recharge of the ground water has
finally begun.

Reservoirs - Normal to Below normal pool levels

Most major reservoirs are hold water storage at near normal levels
for this time of year and with recent rains and increased inflow,
pool levels continue to rise. At Kerr Dam the pool level has
climbed over 300 FT for the first time this winter.

Future Precipitation...There is the potential for rain on 4 of the
next 7 days across the region as multiple frontal passages are
expected. A cold front crosses Friday night and quickly lifts back
to the north on Saturday afternoon and evening. Showers are
expected with each frontal passage. Another chance for rain comes
on Monday as warm air overrides cool air from a retreating area of
high pressure. Finally another strong cold front arrives during
the second half of the week. Overall precipitation amounts of
0.50" - 1.25" are expected during the next 7 days.

The latest CPC 8 to 14 day outlook for February 23 - March 1 2018
is indicating above normal temperatures and near normal to below
precipitation for the 7 day time period.

Lastly, for the 3 month outlook for March through May, the
precipitation forecast is for near normal to above normal while
for temperatures the forecast is for above normal conditions.

WWW.CPC.NCEP.NOAA.GOV

The river flood potential through March 1 2018 across the
Wakefield HSA is normal to below normal for this time of year.
Again, remember that heavy rainfall is the most common cause of
river flooding in the Mid-Atlantic States. However river flooding
can be exacerbated when heavy rain is combined with snow melt.

The next outlook will be issued on March 1, 2018.

For additional weather or hydrologic information, please visit
our website at WWW.WEATHER.GOV/AKQ.

$$

Seymour



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