DROUGHT INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
1245 PM EDT THU OCT 2 2008
...VARIABLE DROUGHT PATTERN CONTINUES...
SYNOPSIS...
THE PAST TWO WEEKS HAVE SEEN ADDITIONAL DROUGHT IMPROVEMENT IN
PARTS OF THE BLACKSBURG HYDROLOGIC SERVICE AREA (HSA)...MAINLY
OVER THE PIEDMONT AREAS. MODERATE TO SEVERE DROUGHT PERSISTS IN
MOST OF THE MOUNTAINS OF NORTH CAROLINA AND 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)...RELEASED OCTOBER 2 AND
REFLECTING CONDITIONS THROUGH 8 AM ON SEPTEMBER 30TH SHOWED D2...OR
SEVERE DROUGHT...STILL PERSISTING IN ONLY THREE NORTH CAROLINA
COUNTIES...ASHE...WATAUGA...AND FAR WESTERN WILKES COUNTY.
MODERATE DROUGHT (D1) COVERS PORTIONS OF THE WESTERN NORTH
CAROLINA PIEDMONT AND FOOTHILLS AND EXTENDS INTO THE MOUNTAINS OF
VIRGINIA. THIS INCLUDES MOST OF THE NEW AND UPPER ROANOKE RIVER
VALLEYS. ABNORMALLY DRY (D0) PERSISTS IN THE FAR NORTHWEST
HSA...ALLEGHANY AND BATH COUNTIES AND EXTENDS INTO SOUTHEASTERN
WEST VIRGINIA AND ALSO ACROSS PARTS OF THE PIEDMONT IN NORTH
CAROLINA AND VIRGINIA. SEPTEMBER RAINS ELIMINATED DROUGHT ENTIRELY
FROM SEVERAL VIRGINIA PIEDMONT COUNTIES...INCLUDING
CHARLOTTE...APPOMATTOX AND BUCKINGHAM. THE CATEGORIES ON THE U.S.
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 SEPTEMBER 27 AND SEPTEMBER 13 2008 PDSI FOR
THE SIX CLIMATE ZONES WHICH COVER THE BLACKSBURG HSA. MOST ZONES SHOWED
IMPROVEMENT DURING THE TWO-WEEK PERIOD BUT MOST NOTICEABLY OVER THE
PIEDMONT AREAS WHICH RECEIVED MORE WIDESPREAD RAINFALL. ONLY THE
NORTHWEST NORTH CAROLINA ZONE IS IN MODERATE DROUGHT ACCORDING TO THIS
INDEX.
STATE CLIMATE ZONE PDSI PRECIP TO PDSI
9/27 END DROUGHT 9/13
NC N. MOUNTAINS -2.19 6.90 -3.00
NC N. PIEDMONT 1.59 -0.57
VA W. PIEDMONT 0.19 -0.36
VA CENT. MTNS. 0.28 -0.25
VA SW MOUNTAINS -1.71 3.44 -1.97
WV SOUTHERN -0.71 0.98 -0.61
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
CROP MOISTURE...
THE NWS CLIMATE PREDICTION CENTER (CPC) CROP MOISTURE INDEX
INDICATED NEAR NORMAL SOIL MOISTURE IN THE 5-FOOT PROFILE
ACROSS MOST OF THE AREA...ALTHOUGH PARTS OF THE NORTH CAROLINA
PIEDMONT ARE ABNORMALLY MOIST. THIS PATTERN IS ALSO SHOWN ON
THE CPC SOIL MOISTURE MODEL WHICH HAS SMALL POSITIVE
MOISTURE ANOMALIES OVER THE PIEDMONT COUNTIES IN NORTH CAROLINA.
RIVERS AND STREAMFLOW...
7-DAY AVERAGE STREAMFLOW PERCENTILE CLASSES AS OF OCTOBER 2
FROM RIVER BASINS IN THE UNITED STATES GEOLOGICAL SURVEY
(USGS) NETWORK SHOW SOME IMPROVEMENT IN AREA STREAMFLOWS.
THE VERY DRY SEPTEMBER IN THE WEST HAS LED TO SIGNIFICANT
STREAMFLOW DECLINES IN THE IN UPPER TENNESSEE RIVER BASIN WHERE
SEVERE HYDROLOGIC DROUGHT IS NOW INDICATED WITH FLOWS BELOW THE
5TH PERCENTILE.
RESERVOIR LEVELS...
POOL ELEVATIONS ON MAJOR AREA RESERVOIRS HAVE REMAINED FAIRLY
STABLE THE PAST TWO WEEKS. HOWEVER LAKE MOOMAW FELL AN ADDITIONAL
2 FEET THE PAST TWO WEEKS AND IS NOW ABOUT 21 FEET BELOW NORMAL POOL.
RESERVOIR CURRENT POOL NORMAL POOL
SMITH MOUNTAIN LAKE VA 790.20 795
CLAYTOR LAKE VA 1842.92 1846
LAKE MOOMAW VA 1561.00 1582
PHILPOTT RESERVOIR 961.98 974
BLUESTONE LAKE WV 1411.92 1410
W. KERR SCOTT NC 1030.90 1030
CARVINS COVE RESERVOIR...A MAJOR SOURCE FOR ROANOKE DRINKING
WATER...IS NOW 8 FEET BELOW THE SPILLWAY...DOWN LESS THAN 1 FOOT IN
THE PAST TWO WEEKS. SPRING HOLLOW RESERVOIR...WHICH SERVES ROANOKE
COUNTY...HAS FALLEN ABOUT 1 FOOT IN THE PAST TWO WEEKS AND IS NOW
32 FEET BELOW ITS SPILLWAY.
CLIMATE SUMMARY...
SEPTEMBER RAINFALL WAS A TALE OF TWO AREAS. FROM THE BLUE RIDGE
FOOTHILLS AND EASTWARD THERE WAS ABOVE NORMAL RAIN FROM THE REMAINS
OF TROPICAL STORM HANNA AND THE SUBTROPICAL STORM LATE IN THE MONTH.
MUCH OF THE PIEDMONT HAD 150 TO 200 PERCENT OF NORMAL SEPTEMBER
PRECIPITATION. IN THE MOUNTAINS IT WAS A DIFFERENT STORY WITH MUCH DRIER
CONDITIONS AND ANYWHERE FROM 25 TO 50 PERCENT OF NORMAL SEPTEMBER RAINFALL.
AT NWS COOP STATIONS THE AVERAGE OF 61 SITES WAS 3.28 INCHES VERSUS THE
AVERAGE OF 3.81 INCHES OR 86 PERCENT OF NORMAL. THE RANGE WAS QUITE WIDE
HOWEVER...WITH ONLY 1.14 AT STAFFORDSVILLE IN GILES COUNTY VA UP TO 7.75
INCHES AT YANCEYVILLE IN CASWELL COUNTY NC. NUMEROUS WEST VIRGINIA
STATIONS HAD UNDER 1.50 INCHES FOR THE MONTH.
THE TABLE BELOW SHOWS RAINFALL AMOUNTS AND PERCENTAGES OF NORMAL OVER
VARIOUS DURATION IN THE PAST YEAR.
MONTH OR SEASON PRECIPITATION NORMAL % OF NORMAL
SEPTEMBER 3.28 3.81 86
SUMMER 2008 (JUN-AUG) 11.35 11.79 96
SPRING 2008 (MAR-MAY) 11.55 12.28 94
WINTER 07-08 (DEC-FEB) 7.19 9.99 72
FALL 2007 (SEP-NOV) 8.49 10.51 81
PRECIPITATION/TEMPERATURE OUTLOOKS...
THE FIVE-DAY PRECIPITATION FORECAST FROM THE HYDROMETEOROLOGICAL
PREDICTION CENTER (HPC) THROUGH OCTOBER 7 SHOWS A VERY DRY PERIOD
WITH NO PRECIPITATION FORECAST.
IN THE LONGER RANGE OUTLOOKS FROM THE NWS CLIMATE PREDICTION CENTER
VALID THROUGH OCTOBER 15 BELOW NORMAL RAINFALL AND ABOVE NORMAL
TEMPERATURES ARE FORECAST.
NEXT ISSUANCE DATE...
THE NEXT DROUGHT STATEMENT WILL BE ISSUED ON OR ABOUT OCTOBER 16
UNLESS CHANGED CONDITIONS WARRANT AN EARLIER UPDATE.
RELATED WEB SITES...
ADDITIONAL INFORMATION ON CURRENT DROUGHT CONDITIONS MAY BE FOUND
AT THE FOLLOWING WEB ADDRESSES...
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/
ADDITIONAL RIVER INFORMATION...
NWS..... http://www.weather.gov/water/
USGS.... http://water.usgs.gov/
USACE... http://www.mvr.usace.army.mil/
ACKNOWLEDGMENTS...
THE DROUGHT MONITOR IS A MULTI-AGENCY EFFORT INVOLVING NOAA'S
NATIONAL WEATHER SERVICE AND NATIONAL CLIMATIC DATA CENTER...THE
USDA...STATE AND REGIONAL CENTER CLIMATOLOGISTS AND THE NATIONAL
DROUGHT MITIGATION CENTER. INFORMATION FOR THIS STATEMENT HAS
BEEN GATHERED FROM NWS AND FAA OBSERVATION SITES...STATE
COOPERATIVE EXTENSION SERVICES...THE USDA...USACE AND USGS.
QUESTIONS OR COMMENTS...
IF YOU HAVE ANY QUESTIONS OR COMMENTS ABOUT THIS DROUGHT
INFORMATION STATEMENT...PLEASE CONTACT...
NATIONAL WEATHER SERVICE
1750 FORECAST DRIVE
BLACKSBURG VA 24060
PHONE: 540-552-1341
RNK.webmaster@noaa.gov
PC