DROUGHT INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
1125 AM EST SAT JAN 3 2009
...ABOVE AVERAGE DECEMBER PRECIPITATION HELPS WITH THE DROUGHT...
SYNOPSIS...
DECEMBER RAINFALL WAS ABOVE AVERAGE ACROSS NEARLY THE ENTIRE AREA
ALTHOUGH NOT ENOUGH TO END DROUGHT CONCERNS COMPLETELY. THE LAST TWO
WEEKS OF THE MONTH WERE FAIRLY DRY LEAVING CONDITIONS BASICALLY
UNCHANGED SINCE IMPROVEMENTS OCCURRED TWO WEEKS AGO.
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 DECEMBER 31 AND
REFLECTING CONDITIONS THROUGH 8 AM ON DECEMBER 30 SHOWED VERY LITTLE
CHANGE SINCE A SIGNIFICANT IMPROVEMENT OCCURRED IN MID-DECEMBER.
WHILE NONE OF THE HSA IS IN THE SEVERE OR D2 DROUGHT CATEGORY...D1
OR MODERATE DROUGHT STILL PERSISTS IN FAR NORTHWEST NORTH CAROLINA
INTO PARTS OF WESTERN VIRGINIA AND SOUTHEAST WEST
VIRGINIA...INCLUDING MOST OF THE NEW RIVER VALLEY...THE UPPER
ROANOKE RIVER VALLEY AND MOST OF THE MOUNTAIN EMPIRE.
THE ABNORMALLY DRY CATEGORY (D0) REMAINS IN A NARROW SWATH OF THE
VIRGINIA AND NORTH CAROLINA PIEDMONT TO THE EAST OF THE MODERATE
DROUGHT AREA. NO DROUGHT AT ALL IS SHOWN IN THE REST OF THE
PIEDMONT WITHIN THE BLACKSBURG HSA AT THIS TIME. THE CATEGORIES ON
THE USDM 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 DECEMBER 27 AND DECEMBER 13 PDSI FOR
THE SIX CLIMATE ZONES WHICH COVER THE BLACKSBURG HSA. THE INDEX
NUMBERS SHOWED SMALL CHANGES IN BOTH DIRECTIONS BUT NO CATEGORY
SHIFTS. NONE OF THE AREA IS IN DROUGHT ACCORDING TO THE PALMER
INDEX AT THIS TIME.
STATE CLIMATE ZONE PDSI PRECIP TO PDSI
12/13 END DROUGHT 12/13
NC N. MOUNTAINS 0.41 0.45
NC N. PIEDMONT 2.50 2.61
VA W. PIEDMONT 1.88 2.39
VA CENT. MTNS. 0.74 0.92
VA SW MOUNTAINS 0.91 0.30
WV SOUTHERN 1.58 1.32
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) SOIL MOISTURE MODEL STILL
SHOWS ONLY A SMALL MOISTURE DEFICIT OVER SOUTHWEST VIRGINIA INTO
NORTHWEST NORTH CAROLINA...LESS THAN 1 INCH. THIS IS ESSENTIALLY
UNCHANGED SINCE TWO WEEKS AGO.
RIVERS AND STREAMFLOW...
7-DAY AVERAGE STREAMFLOW PERCENTILE CLASSES AS OF JANUARY 2
FROM RIVER BASINS IN THE UNITED STATES GEOLOGICAL SURVEY NETWORK
HAVE FALLEN SHARPLY OVER THE PAST TWO WEEKS. MOST OF THE LARGE
RIVER BASINS ARE NOW RUNNING IN THE BELOW NORMAL CATEGORY...IN
THE 10TH TO 24TH PERCENTILE RANGE. THE RAPIDITY OF THIS DECLINE
EVEN IN MID-WINTER MAY BE INDICATIVE OF THE LONGER TERM DROUGHT...
SHOWING THAT GROUNDWATER LEVELS HAVE YET TO RECOVER.
RESERVOIR LEVELS...
POOL ELEVATIONS ON MOST MAJOR AREA RESERVOIRS HAVE LEVELED OFF
OVER THE PAST TWO WEEKS AND SEVERAL MAJOR RESERVOIRS REMAIN
WELL BELOW NORMAL POOL LEVELS INCLUDING LAKE MOOMAW...PHILPOTT
RESERVOIR AND SMITH MOUNTAIN LAKE.
RESERVOIR CURRENT POOL NORMAL POOL
SMITH MOUNTAIN LAKE VA 792.30 795
CLAYTOR LAKE VA 1842.18 1846
LAKE MOOMAW VA 1561.50 1582
PHILPOTT RESERVOIR 965.26 974
BLUESTONE LAKE WV 1406.58 1410
W. KERR SCOTT NC 1030.88 1030
CARVINS COVE RESERVOIR...A MAJOR SOURCE FOR ROANOKE CITY DRINKING
WATER...IS NOW 10.7 FEET BELOW THE SPILLWAY...ABOUT EQUAL TO
TWO WEEKS AGO. SPRING HOLLOW RESERVOIR...WHICH SERVES ROANOKE
COUNTY...IS NOW 41.1 FEET BELOW ITS SPILLWAY AT 54 PERCENT OF
CAPACITY.
CLIMATE SUMMARY...
PRELIMINARY DECEMBER PRECIPITATION DATA...FROM 60 OF THE 77
COOPERATIVE STATIONS AVAILABLE WAS 3.93 INCHES OR 126 PERCENT OF
THE NORMAL OF 3.12 INCHES.
IN ADDITION...PRELIMINARY DATA FOR CALENDAR YEAR 2008 SHOWS ANNUAL
PRECIPITATION OF 37.88 INCHES VERSUS THE ANNUAL MEAN (1971-2000)
OF 44.55 INCHES OR 85 PERCENT OF NORMAL. THESE NUMBERS WILL BE
REVISED WHEN FINAL DATA BECOMES AVAILABLE.
THE TABLE BELOW SHOWS RAINFALL AMOUNTS AND PERCENTAGES OF NORMAL OVER
VARIOUS DURATIONS IN THE PAST YEAR.
MONTH OR SEASON PRECIPITATION NORMAL % OF NORMAL
ANNUAL 2008 37.88 44.55 85
FALL 2008 (SEP-NOV) 7.62 10.51 73
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
PRECIPITATION/TEMPERATURE OUTLOOKS...
LOW PRESSURE IS EXPECTED TO AFFECT THE AREA THE NEXT 24 TO 36 HOURS
WITH RAINFALL OF 0.25 TO 0.50 INCHES ACROSS MUCH OF THE AREA.
ANOTHER MOSTLY RAIN EVENT IS FORECAST TO AFFECT THE REGION
TOWARD MID-WEEK WITH THE POTENTIAL FOR ADDITIONAL SIGNIFICANT AMOUNTS.
THE COMBINED EFFECT OF THESE EVENTS COULD LEAD TO SOME MORE IMPROVEMENT
IN THE DROUGHT PICTURE.
THE LONGER RANGE OUTLOOKS FROM THE NWS CLIMATE PREDICTION CENTER FOR
THE 6 TO 10 PERIOD VALID THROUGH JANUARY 12 AND THE 8 TO 14 DAY
PERIOD THROUGH JANUARY 16 INDICATE NORMAL OR BELOW NORMAL
PRECIPITATION WITH COLDER THAN NORMAL TEMPERATURES THROUGHOUT THE
PERIOD.
NEXT ISSUANCE DATE...
THE NEXT DROUGHT STATEMENT WILL BE ISSUED ON OR ABOUT JANUARY 15
UNLESS CHANGED CONDITIONS WARRANT AN EARLIER UPDATE.
&&
RELATED WEB SITES...
ADDITIONAL INFORMATION ON CURRENT 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://WATERDATA.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/AHPS
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
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