DROUGHT INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
1130 AM EDT THU JUN 26 2008
...SPORADIC JUNE RAINFALL SUSTAINS DROUGHT IN THE REGION...
SYNOPSIS...
JUNE RAINFALL HAS BEEN INCONSISTENT ACROSS THE REGION WITH POCKETS OF
HEAVY RAINFALL AND AREAS WITH VERY LITTLE. DROUGHT CONDITIONS ARE ABOUT
THE SAME OR SLIGHTLY WORSE THAN TWO WEEKS AGO ACROSS THE BLACKSBURG
HYDROLOGIC SERVICE AREA (HSA). EXTREME DROUGHT CONTINUES OVER
SEVERAL COUNTIES IN NORTH CAROLINA AND SEVERE DROUGHT HAS REACHED AS
FAR NORTH AS SOUTHERN VIRGINIA.
THE BLACKSBURG HSA COVERS 27 COUNTIES IN SOUTHWEST VIRGINIA...
4 IN EXTREME SOUTHEAST WEST VIRGINIA AND 9 IN NORTHWEST NORTH
CAROLINA AND INCLUDES PORTIONS OF THE FOLLOWING RIVER BASINS:
JAMES...ROANOKE...NEW...GREENBRIER...DAN...YADKIN...CLINCH AND
HOLSTON.
SUMMARY OF IMPACTS...
THE U.S. DROUGHT MONITOR (USDM)...
THE USDM ISSUED TODAY AND REFLECTING CONDITIONS THROUGH 8 AM ON
JUNE 24 SHOWED A VERY SLIGHT CHANGE IN THE AREA OR INTENSITY OF
DROUGHT ACROSS THE BLACKSBURG HSA. D3 OR EXTREME DROUGHT IS
AFFECTING PORTIONS OF THE UPPER YADKIN RIVER BASIN IN
ASHE...WILKES AND YADKIN COUNTIES. SEVERE DROUGHT (D2) WAS EDGED
NORTHWARD AND NOW COVERS ALL THE REMAINING NORTH CAROLINA COUNTIES
AND INTO EXTREME SOUTHERN VIRGINIA. MODERATE DROUGHT (D1) REMAINS OVER
MOST OF THE NEW AND ROANOKE RIVER VALLEYS IN VIRGINIA. D0 OR ABNORMALLY
DRY CONDITIONS...PERSIST OVER PARTS OF FAR WESTERN VIRGINIA AND
INTO WEST VIRGINIA...EXCEPT FOR GREENBRIER COUNTY.
IT SHOULD BE POINTED OUT THAT THE CATEGORIES ON THE DROUGHT
MONITOR ARE GENERALIZED AND THE LOCAL IMPACTS OF DROUGHT MAY BE
MORE OR LESS THAN WHAT IS DEPICTED ON THE MAP.
THE CATEGORIES OF DROUGHT ARE EXPLAINED BELOW:
D0 IS THE LEAST INTENSE INDICATOR OF DROUGHT ON A SCALE THAT
RANGES FROM D0 THROUGH D4. IT IS BASICALLY A DROUGHT WATCH THAT
INDICATES A REGION GOING INTO OR COMING OUT OF DROUGHT.
D1 IS MODERATE DROUGHT...CONDITIONS THAT MAY BE ASSOCIATED WITH
D1 INCLUDE SOME CROP DAMAGE...INCREASED FIRE RISK...FALLING
RIVER... STREAM...AND RESERVOIR LEVELS AND SOME WATER SHORTAGES.
D2 IS SEVERE DROUGHT...CROP OR PASTURE DAMAGE IS LIKELY. FIRE
RISK IS POTENTIALLY HIGH...ALONG WITH WATER SHORTAGES AND POSSIBLE
WATER RESTRICTIONS.
D3 IS EXTREME DROUGHT...MAJOR CROP AND PASTURE LOSSES AND
WIDESPREAD WATER SHORTAGES AND RESTRICTIONS.
D4 IS EXCEPTIONAL DROUGHT...WIDESPREAD CROP AND PASTURE LOSSES...
WATER SHORTAGES AND WATER EMERGENCIES. MAY BE THOUGHT OF AS THE
50-YEAR DROUGHT OR THE 2 PERCENT ANNUAL CHANCE OF OCCURRENCE.
THE CATEGORIES ARE BASED ON A NUMBER OF KEY INDICATORS: 1) PALMER
DROUGHT INDEX (PDSI) 2) CPC SOIL MOISTURE MODEL 3) USGS WEEKLY
STREAMFLOW PERCENTILES 4) THE STANDARDIZED PRECIPITATION INDEX
AND 5) THE SATELLITE VEGETATION INDEX.
PALMER DROUGHT SEVERITY INDEX (PDSI)...
THE TABLE BELOW SHOWS THE JUNE 21 2008 PDSI FOR THE SIX CLIMATE
ZONES WHICH COVER THE BLACKSBURG HSA. THE INDEX FOR THE NORTH
CAROLINA MOUNTAINS CONTINUED TO DECLINE IN THE PAST TWO WEEKS AND
REMAINS WELL INTO THE EXTREME DROUGHT CATEGORY. THAT AREA NEEDS OVER
A FOOT OF RAIN TO REACH NON-DROUGHT CONDITIONS. DROUGHT INDICES ALSO
DECLINED IN ALL THE OTHER CLIMATE ZONES IN THE HSA AND SEVERE
DROUGHT HAS BEEN REACHED IN THE SOUTHWEST VIRGINIA MOUNTAINS AND
NORTHERN PIEDMONT OF NORTH CAROLINA.
STATE CLIMATE ZONE PDSI PRECIP NEEDED
TO BRING PDSI TO -0.5
NC N. MOUNTAINS -4.47 13.00
NC N. PIEDMONT -3.11 8.51
VA W. PIEDMONT -2.31 6.32
VA CENT. MTNS. -0.94 2.10
VA SW MOUNTAINS -3.31 7.59
WV SOUTHERN -1.21 2.44
THE PALMER INDEX IS CALCULATED WEEKLY AND INDICATES THE RELATIVE
DRYNESS OR WETNESS AFFECTING AN AREA. THERE ARE SEVEN PDSI
CATEGORIES DEFINING WET AND DRY CONDITIONS AS SHOWN IN THE TABLE
BELOW:
-4.0 OR LESS - EXTREME DROUGHT
-3.0 TO -3.9 - SEVERE DROUGHT
-2.0 TO -2.9 - MODERATE DROUGHT
-1.9 TO +1.9 - NEAR NORMAL
+2.0 TO +2.9 - UNUSUAL MOIST SPELL
+3.0 TO +3.9 - VERY MOIST SPELL
+4.0 OR ABOVE - EXTREMELY MOIST
SOIL MOISTURE...
THE NWS CLIMATE PREDICTION CENTER SOIL MOISTURE MODEL IS
USED TO ESTIMATE SOIL MOISTURE IN THE TOP 4 TO 5 FEET USING
RECENT OBSERVED DATA VERSUS LONG-TERM NORMALS. SLIGHT DEFICITS
HAVE DEVELOPED OVER SOUTHEAST WEST VIRGINIA AND WESTERN VIRGINIA
WHILE NORTHWEST NORTH CAROLINA NOW SHOWS DEFICITS OF 2 TO 4
INCHES.
RIVERS AND STREAMFLOW...
THE TABLE BELOW SHOWS 7-DAY AVERAGE STREAMFLOW PERCENTILE CLASSES
FROM RIVER BASINS IN THE UNITED STATES GEOLOGICAL SURVEY (USGS) NETWORK.
THE TABLE SHOWS THAT SEVERE HYDROLOGIC DROUGHT EXISTS IN MOST OF THE NEW
RIVER BASIN IN NORTH CAROLINA AND VIRGINIA...IN THE YADKIN-PEE DEE
IN NORTH CAROLINA AND IN THE UPPER ROANOKE AND TENNESSEE BASINS IN VIRGINIA.
MODERATE HYDROLOGIC DROUGHT IS FOUND IN THE LOWER DAN AND ROANOKE RIVER
BASINS. A NUMBER OF GAGES HAVE HAD NEW RECORD LOW FLOWS FOR THE DATE IN
RECENT WEEKS ESPECIALLY IN THE YADKIN-PEE DEE RIVER BASIN IN NORTH CAROLINA
AND IN THE UPPER ROANOKE IN VIRGINIA.
RIVER BASIN PERCENTILE HYDROLOGIC DROUGHT
CLASS CATEGORY
NEW (VA/NC) <5 SEVERE
UPPER ROANOKE <5 SEVERE
UPPER DAN 10-24 BELOW NORMAL
LOWER DAN-ROANOKE 6-9 MODERATE
YADKIN-PEE DEE <5 SEVERE
MIDDLE JAMES 10-24 BELOW NORMAL
UPPER TENNESSEE <5 SEVERE
RESERVOIR LEVELS...
REDUCED INFLOWS HAVE BEGIN TO REDUCE LAKE LEVELS AT SEVERAL
OF THE MAJOR RESERVOIRS IN THE HSA WITH THE EXCEPTION OF
BLUESTONE AND CLAYTOR LAKES WHICH REMAIN LEVEL. BOTH LAKE
MOOMAW AND W. KERR SCOTT HAVE FALLEN NEARLY TWO FEET IN
THE PAST TWO WEEKS.
RESERVOIR CURRENT POOL NORMAL POOL
SMITH MOUNTAIN LAKE VA 792.60 795
CLAYTOR LAKE VA 1843.08 1846
LAKE MOOMAW VA 1579.34 1582
PHILPOTT RESERVOIR 971.76 974
BLUESTONE LAKE WV 1411.01 1410
W. KERR SCOTT NC 1027.96 1030
CARVINS COVE RESERVOIR...A MAJOR SOURCE FOR ROANOKE DRINKING
WATER...IS 5.6 FEET BELOW THE SPILLWAY AND REMAINED
FAIRLY STABLE IN RECENT WEEKS. SPRING HOLLOW RESERVOIR...WHICH
SERVES ROANOKE COUNTY...IS 11.4 FEET BELOW ITS SPILLWAY.
CLIMATE SUMMARY...
HIGHLY VARIABLE IS THE BEST WAY TO DESCRIBE JUNE RAINFALL SO FAR.
NUMEROUS CONVECTIVE EVENTS HAVE AFFECTED THE AREA WITH SEVERE STORMS
AND SOME HEAVY RAINFALL BUT IT HAS BEEN A HIT AND MISS SITUATION.
ROANOKE AIRPORT FOR EXAMPLE IS ABOVE NORMAL FOR THE MONTH WITH 3.50
INCHES TO DATE...WHILE BLACKSBURG...LYNCHBURG AND DANVILLE ARE ALL
UNDER 50 PERCENT OF NORMAL JUNE RAINFALL. DANVILLE IN FACT HAS SEEN
ONLY 0.81 INCHES AND IS ON A PACE FOR ITS DRIEST JUNE ON RECORD WHICH
WAS 1.13 INCHES IN 1985. THE MONTH HAS ALSO BEEN VERY WARM...RUNNING
3 TO 5 DEGREES ABOVE NORMAL WHICH HAS INCREASED EVAPORATION LOSSES.
THE TABLE BELOW SHOWS THAT MAY HAD ONLY 71 PERCENT OF NORMAL RAINFALL
AT THE 77 NWS COOPERATIVE STATIONS...BUT SOME NORTH CAROLINA MOUNTAIN
SITES HAD ONLY 25 TO 50 PERCENT.
MONTH OR SEASON PRECIPITATION NORMAL % OF NORMAL
MAY 3.15 4.42 71
SPRING 2008 (MAR-MAY) 11.55 12.28 94
APRIL 2008 4.95 3.72 133
MARCH 2008 3.42 4.14 83
WINTER 07-08 (DEC-FEB) 7.19 9.99 72
FALL 2007 (SEP-NOV) 8.49 10.51 81
SUMMER 2007 (JUN-AUG) 9.42 11.79 80
PRECIPITATION/TEMPERATURE OUTLOOKS...
THE FIVE-DAY PRECIPITATION FORECAST FROM THE HYDROMETEOROLOGICAL
PREDICTION CENTER (HPC) DOES NOT SHOW MUCH RAINFALL ACROSS
THE REGION. THE VIRGINIA PIEDMONT IS FORECAST TO RECEIVE
LESS THAN 0.50 INCHES WHILE MOUNTAIN AREAS ARE FORECAST TO
RECEIVE UP TO 1.50 INCHES. IN ALL LIKELIHOOD THE RAINFALL
WILL CONTINUE TO BE SPOTTY WITH POCKETS OF HEAVY RAINFALL BUT
MANY AREAS RECEIVING LITTLE IF ANY.
WITH A MEAN LONG-WAVE TROUGH EXPECTED TO DEVELOP AND PERSIST OVER
THE EASTERN ONE-THIRD OF THE CONUS THE NWS CLIMATE PREDICTION CENTER
IS FORECASTING NEAR NORMAL TEMPERATURES AND RAINFALL DURING THE
6 TO 10 DAY OUTLOOK PERIOD FROM JULY 1-5. IN THE 8 TO 14 DAY
OUTLOOK THROUGH JULY 9 THE HIGHEST PROBABILITY IS FOR ABOVE
NORMAL PRECIPITATION AND NEAR NORMAL TEMPERATURES.
NEXT ISSUANCE DATE...
THE NEXT DROUGHT STATEMENT WILL BE ISSUED ON OR ABOUT JULY
10 UNLESS CHANGED CONDITIONS WARRANT AN EARLIER UPDATE.
RELATED WEBSITES...
ADDITIONAL INFORMATION ON CURRENT AND FORECAST DROUGHT CONDITIONS
MAY BE FOUND AT THE FOLLOWING WEB ADDRESSES /USE LOWER CASE
LETTERS:/
U.S. DROUGHT MONITOR...HTTP://WWW.DROUGHT.UNL.EDU/DM
NATIONAL INTEGRATED DROUGHT INFORMATION SYSTEM...
HTTP://WWW.DROUGHT.GOV
NWS CLIMATE PREDICTION CENTER...HTTP://WWW.CPC.NCEP.NOAA.GOV
UNITED STATES GEOLOGICAL SURVEY...
HTTP://WATER.USGS.GOV/WATERWATCH
NORTH CAROLINA DROUGHT MANAGEMENT ADVISORY COUNCIL...
HTTP://WWW.NCDROUGHT.ORG/
VIRGINIA DEPARTMENT OF ENVIRONMENTAL QUALITY...
HTTP://WWW.DEQ.VIRGINIA.GOV/
ACKNOWLEDGMENTS...
THE DROUGHT MONITOR IS A MULTI-AGENCY EFFORT INVOLVING THE
NATIONAL WEATHER SERVICE...NATIONAL CLIMATIC DATA CENTER...USDA
...STATE AND REGIONAL CLIMATOLOGISTS AND DROUGHT MITIGATION CENTER.
INFORMATION FOR THIS STATEMENT HAS BEEN GATHERED FROM NWS...STATE
COOPERATIVE EXTENSION SERVICES ...THE USDA...USACE AND USGS.
QUESTIONS OR COMMENTS...
PLEASE CONTACT...
NATIONAL WEATHER SERVICE
1750 FORECAST DR.
BLACKSBURG VA 24060
PHONE: 540-552-1341
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PC