Decision Support Briefing

Tuesday, December 11, 2018

NWSSERFC @NWSSERFC

Issued:

Weather Ready Nation

NWSSERFC @NWSSERFC12/11/2018 10:02 AM

• Widespread minor river flooding, with some isolated

moderate flooding, is occurring or forecast as a result of the

latest precipitation event across the southeast US.

• The potential for a “rain-on-snow” flood event in North

Carolina and Virginia is becoming more likely as the next

precipitation event approaches.

NWSSERFC @NWSSERFC

Over the past 24 hours, precipitation was generally light

across the northern half of the SERFC service area.

Heaviest precipitation totals were found across portions

of the coastal plain of North Carolina.

Over the next 48 hours, no significant precipitation is

expected across the SERFC area of responsibility.

NWSSERFC @NWSSERFC

In areas that received liquid precipitation,

headwater forecast points have generally

crested over the past couple of days and

flood waves are working their way

downstream on rivers across the

Southeast.

Using 48 hours of forecast rainfall, this

map depicts current and forecast flood

conditions.

Please visit the SERFC home page or your

local weather office’s page for more

details and updates to the forecasts.

https://www.weather.gov/serfc/

NWSSERFC @NWSSERFC

SERFC accounts for water stored in snowpack

in our modeling system and forecasts. This

map, current as of Dec. 11, 12Z, depicts a

rather large area across the northwestern third

of North Carolina and a large portion of Virginia

with stored water between 1 and 2 inches. The

pale blue color represents isolated areas where

2 to 4 inches of stored water is estimated.

These values are being used to adjust SERFC

model states.

Data from NOAANational Operational Hydrologic Remote Sensing Center

NWSSERFC @NWSSERFC

This morning’s 5-day precipitation forecast from

NOAA’s Weather Prediction Center shows a

large area of 2+ inches of rainfall forecast

across the Carolinas later in the period. The

entirety of the area that currently has 1 inch or

more of water equivalent snowpack in SERFC’s

area of responsibility is currently forecast to

receive at least 1 inch of rainfall. The majority

of the forecast rainfall across the Carolinas and

Virginia is expected on Friday and Saturday.

NWSSERFC @NWSSERFC

The state of the snowpack and the distribution of forecast rainfall

through this next potential flood event will continue to be

reassessed as additional observations and model information

are received.

One way to depict the potential scenarios is through ensemble

modeling. These simulations are produced by varying forecast

precipitation and temperature scenarios through the next week.

This morning’s ensemble run, using the GEFS, indicates a range

of hydrographs with an enhanced flood threat depicted across

Virginia and North Carolina starting Friday, Dec. 14.

These runs are automated and do not replace official forecasts.

Updates and station-specific plots of precipitation, temperature,

snowpack, and streamflow can be found on the MMEFS website.

• SERFC will terminate 24 hours operations this evening.

• The Decision Support Briefing will continue until further notice.

Please send all operational correspondence tosr-alr.rivers@noaa.gov or call the office directly.

NWSSERFC @NWSSERFCWeather Ready Nation

Latest Radar SERFC Quick Brief

Latest Forecast

RainfallMMEFS – Ensemble River Forecasts

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• These slides are intended for your use. Please feel free to share these with others. If you have anyquestions please email sr-alr.rivers@noaa.gov or contact your local NWS Weather Forecast Office.

• Remember: SERFC briefings cover freshwater flooding. For information on coastal and tidal flooding,flash floods, winds, and severe weather risks, please contact your local Weather Forecast Office.

NWSSERFC @NWSSERFCWeather Ready Nation