Flood Potential Outlook
Issued by NWS Wakefield, VA

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Winter/Spring Flood Potential Outlook
National Weather Service WAKEFIELD VA
419 PM EST Thu Jan 18 2018

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

...River Flood Potential is below normal through February 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
Thursday January 18 2018:

Current flooding - No rivers are currently in flood as of 2 PM
Thursday January 18 2018.

Recent precipitation - Over the last 30 days from December 20
2017 to January 18 2018, the precipitation has ranged from 0.75"
to 3" with the lowest amounts of 0.75" - 1" across the Northwest
Virginia Piedmont counties. These amounts were between 2" - 3"
below normal. The remainder of the area saw between 1" - 3" with
deficits up to 2.5". Hopewell VA recorded the most rain for the
period with 3.27" with 2.10" falling on the evening of the 12th
as a strong cold front moved across the region.

Looking back to the beginning of the water year through January
18th, the rain totals generally range from 6" - 13" with the
deficits as high as 6" - 7" across the VA Piedmont and also
through the Tri-Cities. Wallops Island VA reported 12.61 since
the beginning of the water year which is nearly 1.5" above normal
and this is the highest total across the HSA since Oct 1.

Snow conditions - A new fresh snow pack has been laid over the
region in the last 24 hours with the highest totals occuring
across the South Central Piedmont with 4" - 7". Most of the region
along and south of the I-64 corridor saw between 2" - 5" while
across the far north including the Northern Neck of VA and the
Lower Maryland Eastern Shore, the amounts were closer to 1". Water
equivalents in the snow were generally between 0.20" - 0.75". For
a graphical depiction of the snowfall from the January 17 storm
see:

www.weather.gov/images/AKQ/winter/Jan17.png

River ice conditions - There is still ice on area rivers, stream
and creeks, although not as significant as of two weeks ago. There
has been some melting due to the warm up and rain that occurred on
the between the 9th and 13th. But with more cold weather that has
followed through the 18th, there is still some ice on area stream
and creeks with a few gages still showing some flucuations due to
the freezing at night and melting during the day. However,
conditions should continue to improve through Tuesday the 23rd as
warmer conditions are expected.

Stream Flow Conditions - The 14 day average stream flows, through
January 18TH, were generally still below normal across the
majority of the Wakefield HSA but somewhat better than two weeks
ago. Across the Lower Maryland Eastern Shore, 2 gages showed
average flows in the normal range and 2 in the below normal range,
while across Northeastern NC, the 2 gages there were showing
normal to above normal readings, thanks in large part to the rain
on the 11th and 12th. Now across Virginia, there was some
improvement but many locations continue show below normal flows.
Thirty one out of the 33 gages in the Wakefield HSA that the USGS
has rated have below normal flow values. Only 2 are in the normal
range, but that is an improvement from just 2 weeks ago when all
sites were below normal.

When looking at the real time flows as of 1 PM January 18th, the
river levels are mainly mixed for this time of year with some
locations having improved into the normal range in Southeastern VA
and Northeastern NC, while much of Eastern VA is in the below
normal to much below normal range, but again is an improvement
over two weeks ago.. Here are some real time stream flows as of 1
PM January 18th:

LOCATION OBSERVED LEVEL/MEDIAN FLOW/PERCENTAGE OF MEDIAN
RIVANNA RIVER
PALMYRA VA  228 CFS/ 590 CFS/ 38.6
JAMES RIVER
CARTERSVILLE VA    4050 CFS/5980 CFS/ 67.7
RICHMOND VA    4160 CFS/6180 CFS/ 67.3
APPOMATTOX RIVER
    FARMVILLE VA    76 CFS/ 230 CFS/    33.0
MATTOAX VA     123 CFS/ 594 CFS/ 20.7
    MATOACA VA     169 CFS/1030 CFS/ 16.4
NOTTOWAY RIVER
    RAWLINGS VA      78 CFS/    247 CFS/    31.6
    STONY CREEK VA     161 CFS/    500 CFS/    32.2
    SEBRELL VA    1030 CFS/   1460 CFS/    70.5
MEHERRIN RIVER
    LAWRENCEVILLE VA       99 CFS/    391 CFS/    25.3
    EMPORIA VA      174 CFS/    557 CFS/    31.2
BLACKWATER RIVER
    FRANKLIN VA     592 CFS/    830 CFS/    71.3
MATTAPONI RIVER
    BOWLING GREEN VA      70 CFS/    264 CFS/    26.5
    BEULAHVILLE VA     211 CFS/    674 CFS/    31.3
POCOMOKE RIVER
    WILLARDS MD      56 CFS/     80 CFS/    70.0
POTECASI CREEK
    UNION NC     621 CFS/    243 CFS/   255.6

Soil Moisture Conditions - Normal to much 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 January 13 2017, the Wakefield HSA, is
depicted as being near normal for deep soil moisture.

However, the CPC Soil Moisture Monitor, which looks more at top
soil moisture, shows that the entire region is below normal to
much below normal. The moisture deficits range from 20 mm below
normal along the coastal regions of the HSA, while the greatest
deficits of near 100 mm are located in the Central Virginia
Piedmont.

Ground Water - NORMAL TO BELOW NORMAL LEVELS.

Ground water levels across the HSA are in the normal range along
the coastal portions of Virginia and Maryland. However, further
inland across Virginia, including the Piedmont counties, the
ground water levels are running below normal to much below
normal. Across Northeastern North Carolina, the groundwater gage
in Elizabeth City is also showing below normal levels, but this is
a very shallow well and responds quickly to precipitation events.
With several inches of snow currently on the ground this gage is
may respond quickly and return to more normal levels.

Reservoirs - Below normal pool levels

Area reservoir pool levels are in the below normal range for this
time of year due to the low rainfall totals over the last 6
months.

Future Precipitation...After a winter weather event on January 17,
the region will see a period of dry weather with a good warm up
expected as high pressure slides off the Southeast US coast and
southwesterly flow returns from the 19th - 22nd. A strong cold
front is anticipated to cross the region the night of the 22nd
into the 23rd, which will bring a chance for rain showers.
Rainfall amounts of a quarter to half inch are possible with this
front. Behind the front cooler and drier conditions return with
Canadian High pressure dropping southeastward into the Mid-
Atlantic States.

The latest CPC 8 to 14 day outlook for January 25 - February 1
2018 is indicating above normal temperatures and above normal
precipitation for the 7 day time period.

Lastly, for the 3 month outlook for February through April, the
precipitation forecast is for equal chance of being below normal,
near normal and above normal while for temperatures the forecast
is for above normal conditions.

WWW.CPC.NCEP.NOAA.GOV

The river flood potential through February 1 2018 across the
Wakefield HSA is 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 February 1, 2018.

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


$$



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