Flood Potential Outlook
Issued by NWS Blacksburg, VA

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FGUS71 KRNK 191945
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NCC005-009-033-157-169-171-189-193-197-VAC005-009-011-017-019-021-
023-029-031-035-037-045-063-067-071-077-083-089-121-141-143-155-
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WVC025-055-063-089-211945-

WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE BLACKSBURG VA
245 PM EST THU FEB 19 2015

...WINTER/SPRING FLOOD OUTLOOK...NUMBER 4

...NEAR NORMAL RIVER FLOOD POTENTIAL...

THIS IS THE FOURTH 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 MARCH 5TH 2015.

FOR THE BLACKSBURG HSA THE POTENTIAL FOR FLOODING DURING THE TWO-
WEEK OUTLOOK PERIOD IS NEAR NORMAL BASED EXISTING SNOW AND
PRECIPITATION OUTLOOKS. THE BEST CHANCE WOULD BE THIS WEEKEND WITH
A SNOW CHANGING TO RAIN EVENT BUT ANY FLOODING WOULD BE MINOR.

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...

NONE.

RECENT PRECIPITATION...

FEBRUARY TO DATE (THROUGH 12Z ON THE 19TH) HAS CONTINUED THE
PATTERN OF BELOW NORMAL PRECIPITATION THAT HAS EXISTED ALL WINTER.
AMOUNTS SO FAR THIS MONTH RANGE GENERALLY FROM 0.75 TO 1.50 INCHES
WITH UP TO 2 INCHES IN PARTS OF THE GREENBRIER VALLEY AND THE
LOWER DAN RIVER BASIN. THIS REPRESENTS FROM LESS THAN 50 PERCENT
OF NORMAL UP TO NEAR NORMAL...BUT MOST AREAS ARE BELOW.

JANUARY WAS VERY DRY...WITH AVERAGE PRECIPITATION OF 1.88 INCHES
VERSUS THE 30-YEAR MEAN OF 3.31 INCHES OR ONLY 57 PERCENT OF THE
MEAN.

DECEMBER 2014 PRECIPITATION WAS ALSO BELOW NORMAL AT 2.85 INCHES
OR 86 PERCENT OF THE 1981-2010 NORMAL OF 3.32 INCHES.

FALL 2014 (SEP-NOV) PRECIPITATION FALL WAS ALMOST EXACTLY NORMAL
WITH 10.54 INCHES VERSUS THE NORMAL OF 10.38 INCHES.

DROUGHT...

ABNORMALLY DRY (D0) CONDITIONS ON THE LATEST WEEKLY U.S. DROUGHT
MONITOR HAVE BEEN EXPANDED IN RECENT WEEKS DUE TO THE PERSISTENT
DRY PATTERN AND D0 NOW COVERS NEARLY THE ENTIRE AREA WITH THE
EXCEPTION OF THE GREENBRIER BASIN IN WEST VIRGINIA AND PARTS OF THE
LOWER DAN AND LOWER ROANOKE BASINS. 60- TO 90-DAY PRECIPITATION IN
MUCH OF THE D0 AREAS IS ONLY 50 TO 75 PERCENT OF NORMAL.

PLEASE SEE DROUGHTMONITOR.UNL.EDU FOR MORE INFORMATION ABOUT
DROUGHT.

SNOW COVER...

THE STORM OF FEBRUARY 16-17 BROUGHT WIDESPREAD SNOW THAT RANGED
FROM ABOUT 3 TO 10 INCHES WITH THE LOWER AMOUNTS IN THE SOUTHEAST
HSA WHERE SLEET MIXED IN AND THE HIGHER TOTALS IN THE WESTERN
MOUNTAINS. SNOW WATER EQUIVALENT RANGED FROM ABOUT 0.50 TO 1.00
INCH...AN AMOUNT THAT REMAINS IN THE SNOWPACK AFTER DAYS OF SUB-
FREEZING TEMPERATURES.

PLEASE SEE WWW.NOHRSC.NOAA.GOV FOR MORE INFORMATION ON SNOW
COVER.

RIVER ICE...

THE BITTER COLD HAS LED TO RAPID ICE FORMATION ON SOME RIVERS AND
STREAMS ACROSS THE MOUNTAINS AND COULD CAUSE SOME ICE JAM FLOODING
ISSUES WHEN WARMER TEMPERATURES RETURN.

STREAMFLOW...

STREAMFLOWS ARE RUNNING WELL BELOW NORMAL IN NEARLY THE ENTIRE
HSA DUE TO THE DRY WINTER SO FAR. THE LOWEST STREAMFLOWS ARE IN
PARTS OF THE LOWER ROANOKE AND DAN RIVER BASINS WHERE A FEW SITES
ARE BELOW THE 10TH PERCENTILE OF ALL FLOWS FOR THIS DATE.

PLEASE SEE WATERWATCH.USGS.GOV FOR MORE STREAMFLOW INFORMATION.

SOIL MOISTURE...

THE LATEST CPC SOIL MOISTURE ANALYSIS SHOW BELOW NORMAL SOIL
MOISTURE IN MOST OF THE HSA WITH A BROAD AREA SHOWING A DEFICIT
OF 20 MM OR NEARLY ONE INCH.

PLEASE SEE WWW.CPC.NCEP.NOAA.GOV FOR MORE SOIL MOISTURE AND
CLIMATE INFORMATION.

THE UNIVERSITY OF WASHINGTON EXPERIMENTAL SOIL MOISTURE ANALYSIS
CONFIRMS THE GENERAL PATTERN OF BELOW NORMAL SOIL MOISTURE
CONDITIONS ACROSS PARTS OF THE HSA WITH PERCENTILES AS LOW AS THE
5TH OVER SMALL AREAS OF SOUTHWEST VIRGINIA.

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

RESERVOIRS...

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

FUTURE WEATHER CONDITIONS...

A SIGNIFICANT STORM APPEARS LIKELY DURING THE UPCOMING WEEKEND
WITH A COMBINATION OF SNOW...SLEET...FREEZING RAIN AND RAIN ACROSS
THE HSA. THIS SYSTEM SHOULD START OUT AS SNOW AND TRANSITION
THROUGH VARIOUS TYPES TO ALL RAIN BUT THE AMOUNT AND DURATION OF EACH
TYPE IS UNCERTAIN AND WILL VARY WIDELY ACROSS THE HSA. STORM TOTAL LIQUID
EQUIVALENT AMOUNTS COULD RANGE FROM 1 TO 2 INCHES...BUT IT DOES
NOT APPEAR AT THIS TIME THAT A COMPLETE MELT OF THE SNOWPACK WILL
OCCUR BEFORE FREEZING TEMPERATURES RETURN BY LATE SUNDAY AND SLOW
ANY RUNOFF DRAMATICALLY. NO RIVERS ARE FORECAST TO REACH FLOOD
STAGE BUT SEVERAL ENSEMBLE HYDROLOGIC SOLUTIONS DO INDICATE A
POSSIBLE RISE TO AT LEAST ACTION STAGE ON SOME RIVERS BY LATER
SUNDAY OR MONDAY. NO SIGNIFICANT STORMS ARE EXPECTED DURING THE
REMAINDER OF THE 7-DAY FORECAST PERIOD.

LONGER TERM OUTLOOKS (6-10 AND 8-14 DAY) FROM THE CLIMATE
PREDICTION CENTER VALID THROUGH FEBRUARY 28TH AND MARCH 4TH SHOW
A HIGHER PROBABILITY OF CONTINUED BELOW NORMAL TEMPERATURES IN
BOTH PERIODS. THERE IS A HIGHER PROBABILITY OF NEAR NORMAL
PRECIPITATION IN THE 6-10 DAY AND HIGHER PROBABILITY OF ABOVE
NORMAL IN THE 8-14 DAY.

REPEATING THE CURRENT FLOOD POTENTIAL OUTLOOK FOR THE NEXT TWO
WEEKS: NEAR NORMAL.

THE NEXT SCHEDULED UPDATE OF THE WINTER/SPRING FLOOD OUTLOOK WILL
BE MARCH 5TH 2015.

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


$$

PC



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