Flood Potential Outlook
Issued by NWS Blacksburg, VA

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE BLACKSBURG VA
415 PM EST THU FEB 4 2016

...WINTER/SPRING FLOOD OUTLOOK...NUMBER 3

...FLOOD POTENTIAL DECREASING AFTER THIS WEEKEND DUE TO LOSS OF
SNOWPACK AND LACK OF WIDESPREAD PRECIPITATION...

THIS IS THE THIRD IN A SERIES OF ANNUAL WINTER/SPRING FLOOD
POTENTIAL STATEMENTS INTENDED TO PROVIDE INSIGHT INTO THE
LIKELIHOOD OF RIVER FLOODING (NOT FLASH FLOODING) ACROSS THE
BLACKSBURG HYDROLOGIC SERVICE AREA (HSA). THE HSA INCLUDES ALL OR
PARTS OF THE JAMES...ROANOKE...UPPER YADKIN...GREENBRIER...
NEW...CLINCH AND HOLSTON RIVER BASINS IN WESTERN VIRGINIA...
SOUTHEAST WEST VIRGINIA AND NORTHWEST NORTH CAROLINA.

THESE STATEMENTS PROVIDE INFORMATION ON FLOOD THREAT CONDITIONS
SUCH AS RECENT PRECIPITATION...SOIL MOISTURE...SNOW COVER AND ITS
WATER EQUIVALENT...RIVER ICE CONDITIONS...STREAMFLOW...FUTURE
PRECIPITATION AND OTHERS FACTORS. THIS OUTLOOK IS VALID FOR THE
PERIOD THROUGH FEBRUARY 18 2016.

MINOR FLOODING IS OCCURRING ON THE LOWER DAN AND ROANOKE RIVERS
THROUGH FEBRUARY 6TH DUE TO RECENT HEAVY RAIN...HOWEVER THE
POTENTIAL FOR FLOODING DURING THE REMAINDER OF THE OUTLOOK PERIOD
FOR THE BLACKSBURG HSA IS CONSIDERED TO BE BELOW NORMAL DUE TO
LOSS OF SNOWPACK AND LACK OF ANY WIDESPREAD PRECIPITATION EVENT IN
THE FORESEEABLE FUTURE.

IN THIS PART OF THE MID-ATLANTIC REGION...IT IS HEAVY RAINFALL
THAT IS THE PRIMARY FACTOR LEADING 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.

CURRENT FLOODING...

MINOR FLOODING IS OCCURRING ON THE DAN RIVER FROM DANVILLE THROUGH
SOUTH BOSTON THROUGH SATURDAY FEB 6TH. MINOR FLOODING IS ALSO
OCCURRING ON THE ROANOKE RIVER AT RANDOLPH...WHICH IS EXPECTED TO
PERSIST THROUGH THE EVENING OF FRIDAY FEB 5TH.

RECENT PRECIPITATION...

WIDESPREAD HEAVY RAIN FELL ACROSS THE BLACKSBURG HSA DURING THE
EARLY MORNING THROUGH AFTERNOON HOURS OF FEBRUARY 3RD. RAINFALL
AMOUNTS RANGED FROM 1 TO 3 INCH AMOUNTS ACROSS THE ROANOKE...
DAN...YADKIN...AND UPPER NEW RIVER BASINS...WITH HIGHER AMOUNTS
ALONG THE CREST OF THE BLUE RIDGE. LESSER RAINFALL AMOUNTS OF
GENERALLY AROUND AN INCH WERE OBSERVED ACROSS OTHER RIVER BASINS
INCLUDING THE GREENBRIER AND JAMES RIVER.

AVERAGE JANUARY 2016 PRECIPITATION BASED ON 51 REPORTING
COOPERATIVE AND ASOS STATIONS WAS 2.87 INCHES...WHICH IS ROUGHLY
86 PERCENT OF THE 1981-2010 NORMAL OF 3.32 INCHES FOR JANUARY.

DECEMBER 2015 WAS MUCH WETTER THAN NORMAL WITH PRECIPITATION AT 62
NWS COOP STATIONS OF 5.97 INCHES OR 180 PERCENT OF THE 1981-2010
NORMAL OF 3.32 INCHES.

FALL 2015 (SEP-NOV) WAS CONSIDERABLY WETTER THAN NORMAL WITH 17.25
INCHES VERSUS THE NORMAL OF 10.38 INCHES.

DROUGHT...

NONE.

SNOW COVER...

VERY LITTLE SNOW COVER REMAINS ACROSS THE AREA...WITH PERHAPS AN
INCH OR TWO REMAINING IN SPOTS AGAINST NORTH FACING SLOPES.
REMAINING SNOW COVER IS INCONSEQUENTIAL IN TERMS OF SNOW MELT AND
IMPACTS TO RIVER LEVELS.

PLEASE SEE WWW.NOHRSC.NOAA.GOV FOR DETAILED INFORMATION ON SNOW
COVER AND SNOW WATER EQUIVALENT.

RIVER ICE...

RIVER ICE IS VIRTUALLY NON EXISTENT ACROSS THE BLACKSBURG HSA DUE
TO RECENT WARM TEMPERATURES AND HEAVY RAINFALL.

STREAMFLOW...

SHORTER DURATION STREAMFLOWS (REAL-TIME AND 7-DAY AVERAGES) FOR
ALL RIVER BASINS IN THE BLACKSBURG HSA ARE RUNNING VERY HIGH ABOVE
NORMAL DUE TO RECENT HEAVY RAIN AND SNOW MELT FROM THE WIDESPREAD
JANUARY SNOWFALL. LONGER DURATIONS (14-DAY AND 28-DAY AVERAGES)
ARE TRENDING TO NORMAL TO SLIGHTLY ABOVE NORMAL FLOWS...REFLECTING
THE DRIER CONDITIONS FROM THE EARLY HALF OF JANUARY. THE HIGHEST
LONGER DURATION FLOWS RELATIVE TO NORMAL ARE IN THE SOUTHERN RIVER
BASINS...INCLUDING THE YADKIN...DAN AND THE UPPER NEW.

FOR MORE DETAILED INFORMATION ON STREAMFLOW CONDITIONS SEE THE USGS
WATERWATCH SITE BELOW.

HTTP://WATERDATA.USGS.GOV/?ID=WW_CURRENT

SOIL MOISTURE...

THE CPC SOIL MOISTURE RANKINGS INDICATE WELL ABOVE NORMAL SOIL
MOISTURE ACROSS NEARLY ALL OF THE BLACKSBURG HSA.

FOR ADDITIONAL INFORMATION FROM CPC: HTTP://WWW.CPC.NCEP.NOAA.GOV

THE UNIVERSITY OF WASHINGTON EXPERIMENTAL SOIL MOISTURE ANALYSIS
CONFIRMS VERY WET SOIL MOISTURE CONDITIONS EXIST ACROSS NEARLY ALL
OF THE BLACKSBURG HSA.

THIS DATA CAN BE ACCESSED AT:
HTTP://WWW.HYDRO.WASHINGTON.EDU/FORECAST/MONITOR/

RESERVOIRS...

ALL MAJOR RESERVOIRS SERVING THE HSA REMAIN NEAR GUIDE CURVES
AND/OR CONSERVATION POOL LEVELS.

FUTURE WEATHER CONDITIONS...

THE BLACKSBURG HSA WILL BE IMPACTED BY MULTIPLE COLD FRONTS
THROUGH FEBRUARY 12TH THAT WILL RESULT IN PRECIPITATION AMOUNTS
RANGING FROM 0.25 TO 0.75 INCHES OF LIQUID EQUIVALENT...WITH
HIGHEST AMOUNTS EXPECTED ALONG THE RIDGES OF SOUTHEAST WEST
VIRGINIA AND FAR WESTERN VIRGINIA. MUCH OF THIS PRECIPITATION WILL
FALL IN THE FORM OF SNOW SHOWERS.

LONGER TERM OUTLOOKS (6-10 AND 8-14 DAY) FROM THE CLIMATE
PREDICTION CENTER VALID THROUGH FEBRUARY 13 AND FEBRUARY 17
INDICATE NORMAL TO SLIGHTLY BELOW NORMAL PROBABILITIES FOR
PRECIPITATION...ESPECIALLY IN THE LATER PERIOD. TEMPERATURES ARE
FORECAST TO BE BELOW NORMAL IN THE 6-10 DAY PERIOD BUT WILL RETURN
TO NEAR NORMAL FOR THE 8-14 DAY PERIOD. COOLER TEMPERATURES AND
BELOW NORMAL PRECIPITATION WILL SIGNIFICANTLY REDUCE THE POTENTIAL
FOR RIVER FLOODING BEGINNING THE SECOND WEEK OF FEBRUARY.

PROBABILISTIC/ENSEMBLE RIVER FORECASTS...

OUTSIDE OF CURRENT FLOODING OCCURRING ON THE DAN AND ROANOKE
RIVERS...THE PROBABILISTIC OUTLOOKS FROM THE METEOROLOGICAL MODEL
ENSEMBLE RIVER FORECASTS (MMEFS) INDICATE A LOW PROBABILITY OF
RIVER FLOODING AT ALL FORECAST POINTS THROUGH THE NEXT WEEK...
FEBRUARY 11TH...DUE TO A LACK OF SNOWPACK AND SIGNIFICANT
PRECIPITATION.

ENSEMBLE RIVER FORECASTS (MMEFS) ARE AVAILABLE ON THE WEB AT:
WWW.WEATHER.GOV/ERH/MMEFS.

REPEATING THE CURRENT FLOOD POTENTIAL OUTLOOK: MINOR FLOODING IS
OCCURRING ON THE LOWER DAN AND ROANOKE RIVERS THROUGH FEBRUARY
6TH...AND THEN BELOW NORMAL POTENTIAL FOR FLOODING EXISTS
THEREAFTER FOR ALL BASINS ACROSS THE BLACKSBURG HSA.

THE NEXT SCHEDULED UPDATE OF THE WINTER/SPRING FLOOD OUTLOOK WILL
BE FEBRUARY 18 2016.

FOR ADDITIONAL WEATHER OR HYDROLOGIC INFORMATION...VISIT OUR
WEBSITE AT WWW.WEATHER.GOV/BLACKSBURG

$$



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