FXUS25 KWNC 081330
PMDDRO
US DROUGHT MONITOR DISCUSSION
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EST THU 08 MAY 2008
NATIONAL DROUGHT SUMMARY -
MAY 6, 2008
AN INTENSE, LATE-SPRING STORM AT THE BEGINNING OF THE
PERIOD DUMPED HEAVY SNOW AND RAIN ON THE NORTH-CENTRAL
HIGH PLAINS, EASING DROUGHT CONCERNS IN SOUTHEASTERN
MONTANA, NORTHEASTERN WYOMING, AND WESTERN SOUTH DAKOTA.
LATER IN THE PERIOD, AN UPPER-LEVEL LOW TRACKED FROM
THE SOUTHWEST INTO THE CENTRAL AND SOUTHERN PLAINS,
TRIGGERING SCATTERED SHOWERS AND THUNDERSTORMS AND
REDUCING DROUGHT CONDITIONS IN WESTERN TEXAS AND
SOUTHEAST NEW MEXICO. DRYNESS PERSISTED FOR THE
EASTERN GULF AND SOUTHERN ATLANTIC COASTS, WHILE LIGHT
TO MODERATE RAINS IN THE NORTHEAST MAINTAINED FAVORABLE
TO ABUNDANT MOISTURE CONDITIONS. LIGHT PRECIPITATION
FELL ON THE NORTHWEST FOR THE 8TH CONSECUTIVE WEEK,
AND THE SOUTHWEST REMAINED DRY. TEMPERATURES ACROSS
MUCH OF THE LOWER 48 STATES AVERAGED BELOW NORMAL,
WITH THE GREATEST DEPARTURES /LESS THAN -4 DEGF/
IN THE GREAT BASIN, CENTRAL PLAINS, UPPER MIDWEST,
AND NORTHEAST.
THE SOUTHEAST AND MID-ATLANTIC:
UNFORTUNATELY, D2-D3 AREAS OF EASTERN TENNESSEE
AND NORTHERN ALABAMA MISSED OUT ON THE HEAVIEST
RAIN THIS WEEK WHEN A POWERFUL STORM SYSTEM DUMPED
2 TO 7 INCHES OF RAIN ON THE DELTA AND THE WESTERN
TENNESSEE AND SOUTHWESTERN OHIO VALLEYS. WEEKLY TOTALS
BELOW 0.5 INCHES WERE OBSERVED ACROSS THE D2 AREAS IN
SOUTHEASTERN TENNESSEE AND NORTHERN ALABAMA AND GEORGIA,
WHERE SHORT-TERM /30- AND 60-DAYS/ DEFICITS PERSISTED,
RANGING FROM 3-6 INCHES, AND LONGER-TERM DEFICIENCIES
/6- AND 12-MONTHS/ REMAINED BETWEEN 10-25 INCHES.
A STRONG LINE OF THUNDERSTORMS MOVED THROUGH THE GULF
COAST REGION EARLY ON SATURDAY MORNING, BRINGING 1-2
INCHES OF RAIN TO SOUTHERN LOUISIANA, MISSISSIPPI, AND
ALABAMA, WHILE 4 TO 8 INCHES INUNDATED SOUTHEASTERN
LOUISIANA. CONSEQUENTLY, THE D0 AND D1 AREAS WERE
ALLEVIATED TO THE NORTH AND WEST OF LAKE PONTCHARTRAIN,
WHERE 30-DAY DEFICITS /1-3 INCHES/ AND 90-DAY SHORTAGES
/2 TO 6 INCHES/ WERE ERASED. THE D2H AND D3H REGIONS
OF CENTRAL AND NORTHERN ALABAMA BENEFITED FROM 0.5 TO
1.5 INCHES OF RAIN DURING THE WEEK /TOPSOIL MOISTURE/,
BUT LONG-TERM PRECIPITATION DEFICITS AND VERY LOW
STREAM FLOW LEVELS SUGGESTED THAT IMPROVEMENTS TO
THIS AREA WERE NOT WARRANTED YET. THOUGH EASTERN D0
AREAS ALONG THE SOUTHERN ATLANTIC COAST DID RECEIVE
RAINFALL EXCEEDING ONE INCH, THE DROUGHT-STRICKEN
WESTERN REGIONS OF NORTH CAROLINA, SOUTH CAROLINA AND
NORTHERN GEORGIA RECEIVED LITTLE OR NO PRECIPITATION,
AND D3 WAS EXPANDED SLIGHTLY INTO THE WESTERN COUNTIES
OF SOUTH CAROLINA DUE TO PERSISTENTLY LOW USGS 7-DAY
AVERAGED STREAM FLOW PERCENTILES /2-10TH PERCENTILE/.
SOUTH FLORIDA D0 AND D1 COVERAGE WAS EXPANDED EASTWARD
ACROSS PALM BEACH, BROWARD AND MIAMI-DADE COUNTIES
DUE TO THE THIRD CONSECUTIVE DRY WEEK, AND D2 WAS
INTRODUCED INTO GLADES, HENDRY AND COLLIER COUNTIES
OWING TO DECREASING SOIL MOISTURE PERCENTILES ACROSS
INTERIOR PORTIONS OF SOUTHERN FLORIDA.
THE PLAINS AND MIDWEST:
A LATE SPRING SNOWSTORM BROUGHT BLIZZARD CONDITIONS
AND HEAVY SNOW TO THE NORTH-CENTRAL HIGH PLAINS, WITH
LIQUID EQUIVALENT PRECIPITATION TOTALS AS HIGH AS
4.5 INCHES IN SOUTHEAST MONTANA, AND BETWEEN 2 AND 3
INCHES IN WESTERN SOUTH DAKOTA. A GENERAL ONE-CATEGORY
IMPROVEMENT WAS MADE IN THIS AREA. THE D2 COVERAGE IN
SOUTHEASTERN MONTANA WAS REDUCED INTO WESTERN NORTH
DAKOTA, WHERE SURPLUSES NOW EXIST IN BOTH THE SHORT
AND MEDIUM-TERM. IN WESTERN AND NORTHERN SOUTH DAKOTA,
D0 AND D1 COVERAGE WAS TRIMMED BACK AS WELL, AND D1
WAS REDUCED TO D0 IN FAR WESTERN PARTS OF THE STATE,
ALONG WITH D0 BEING CUT BACK IN NORTHEAST WYOMING.
WHILE THIS HEAVY PRECIPITATION BROUGHT RELIEF TO THE
NORTH-CENTRAL HIGH PLAINS, RAINFALL AMOUNTS BETWEEN 0.5
AND 1.2 INCHES IN THE NEBRASKA PANHANDLE DID LITTLE
TO EASE LONG-TERM DRYNESS, PRECLUDING ANY CHANGES TO
THE D2H AND D3H COVERAGE THIS WEEK. DROUGHT BLENDS
DO SHOW A SLIGHT IMPROVEMENT THIS WEEK, BUT 30-, 60-,
AND 90-DAY PRECIPITATION REMAINED BELOW 50 PERCENT
OF NORMAL, AND BOX BUTTE RESERVOIR WAS REPORTED TO
BE AT 27 PERCENT OF CAPACITY /49 PERCENT OF NORMAL
CAPACITY/, THOUGH SLOWLY INCREASING WHICH IS EXPECTED
AT THIS TIME OF YEAR. FURTHER SOUTH, HEAVY SHOWERS AND
SLOW-MOVING THUNDERSTORMS DUMPED OVER 2 INCHES OF RAIN
ON SOUTHWESTERN KANSAS /ACROSS THE D1A AND D2A AREAS OF
SEWARD, MEADE, AND CLARK COUNTIES/, REPLENISHING TOPSOIL
MOISTURE AND PROMPTING A REDUCTION IN DROUGHT COVERAGE
IN A LOCALIZED AREA OF SOUTHWEST KANSAS. ADDITIONAL
STORMS IN WESTERN TEXAS AND EASTERN NEW MEXICO LATE IN
THE PERIOD BROUGHT OVER 2 INCHES OF RAIN TO WESTERN
AREAS OF THE BRAZOS AND RED RIVER VALLEYS, WITH MUCH
OF THE D2A IN SOUTHEASTERN NEW MEXICO REDUCED TO D1,
AND THE D1 BOUNDARY REDUCED WESTWARD INTO NEW MEXICO.
AREAS OF NORTHWESTERN TEXAS AND THE OKLAHOMA PANHANDLE,
HOWEVER, MISSED OUT ON THIS RAINFALL, AND NO ADJUSTMENTS
WERE MADE TO THE D2A COVERAGE. EAST OF THE BIG BEND
AND ALONG THE RIO GRANDE VALLEY, MODERATE RAINS OVER THE
PAST TWO WEEKS, COMBINED WITH RECENT HEAVY RAINFALL FROM
THUNDERSTORMS, ELIMINATED THE EXCEPTIONAL DROUGHT /D4/
AREA ENCOMPASSING MAVERICK, DIMMITT, AND WEBB COUNTIES.
THE WEST:
MUCH OF THE SOUTHWEST REMAINED DRY DURING THIS
PERIOD, WITH MOST OF CALIFORNIA, ARIZONA, AND THE
GREAT BASIN REPORTING LITTLE OR NO PRECIPITATION.
LIGHT PRECIPITATION /0.1 TO 0.3 INCHES/ WAS OBSERVED
IN SOUTHEASTERN OREGON AND SOUTHWESTERN IDAHO,
BUT AN UPPER-LEVEL RIDGE KEPT THE REGION RAIN-FREE
EARLY IN THE WEEK, OFFERING NO DROUGHT RELIEF.
MORE SIGNIFICANT PRECIPITATION /0.3 TO 1.5 INCHES/
FELL FURTHER NORTH ON THE DROUGHT-FREE NORTHWEST,
ESPECIALLY IN THE CASCADES. AFTER AN EXCEPTIONALLY
WET START TO THE 2007-08 WATER YEAR, PRECIPITATION IN
THE WEST HAS GREATLY DIMINISHED SINCE EARLY FEBRUARY,
ESPECIALLY IN THE SOUTHWEST. PRECIPITATION DURING
THE PAST 90-DAYS WAS WELL UNDER 50 PERCENT OF NORMAL
FOR MUCH CALIFORNIA, NEVADA, ARIZONA, AND WESTERN NEW
MEXICO. FARTHER NORTH, PRECIPITATION HAS ALSO BEEN
SUBNORMAL, BUT NOT QUITE AS SEVERE AS THE SOUTHWEST.
HOWEVER, LOOKING BACK DURING THE PAST 7 MONTHS, THE
WATER YEAR TO DATE /WYTD/ BASIN-AVERAGE PRECIPITATION
IS SURPRISINGLY CLOSE TO NORMAL FOR MUCH OF THE WEST.
FORTUNATELY, COLD CONDITIONS SINCE MID-MARCH HAVE
LIMITED SNOW MELT, AND ALONG WITH FREQUENT BUT WEAK
PACIFIC STORM SYSTEMS AND DECREASING NORMAL SNOW WATER
CONTENTS, THE OBSERVED NRCS BASIN-AVERAGED SNOW WATER
CONTENT /SWC/ ACROSS THE NORTHERN HALF OF THE WEST
HAS REMAINED AT OR ABOVE-NORMAL, REMAINING STEADY OR
ACTUALLY INCREASING DURING THE PAST FEW WEEKS. IN THE
CASCADES, SWC WAS BETWEEN 150-285 PERCENT OF NORMAL.
FARTHER SOUTH, HOWEVER, AN AREA OF CONCERN WAS IN
CALIFORNIA’S SIERRA NEVADA, WHERE SWC HAS DECLINED TO
BETWEEN 45-77 PERCENT OF NORMAL, AND WYTD PRECIPITATION
AVERAGED BETWEEN 72-81 PERCENT OF NORMAL.
HAWAII, ALASKA, AND PUERTO RICO:
WEEKLY RAINFALL TOTALS REMAINED LOW ACROSS MUCH OF
HAWAII, WITH JUST 0.5 TO 1 INCH REPORTED ON MAUI, AND
BETWEEN 0.5 AND 4 INCHES REPORTED ON THE EASTERN SLOPES
OF BIG ISLAND, KEEPING D0 AND D1 CONDITIONS STATUS-QUO.
DROUGHT-AFFLICTED AREAS OF CENTRAL AND EASTERN ALASKA
ALSO REMAINED UNCHANGED, DUE TO RAINFALL AMOUNTS
GENERALLY BELOW 0.5 INCHES, WHILE MUCH OF INTERIOR AND
WESTERN ALASKA RECEIVED CLOSE TO ZERO PRECIPITATION.
SOME IMPROVEMENT WAS MADE IN D0 COVERAGE ACROSS WESTERN
PUERTO RICO AFTER A SECOND WET WEEK BROUGHT OVER 5
INCHES OF RAIN TO THE NORTHERN AND WESTERN SLOPES OF
THE ISLAND, ELIMINATING ABNORMAL DRYNESS ACROSS THE
NORTHERN TWO-THIRDS OF THE ISLAND.
LOOKING AHEAD:
DURING THE NEXT 5 DAYS, AN UPPER-LEVEL LOW MOVING
THROUGH THE SOUTHWESTERN UNITED STATES WILL TRIGGER
THUNDERSTORMS CLUSTERS ACROSS THE SOUTHERN AND CENTRAL
PLAINS AND DELTA ON WEDNESDAY, MAY 7, WITH ADDITIONAL
RAIN AND STORMS MOVING INTO THE SOUTHEAST ON THURSDAY.
RAINFALL IN EXCESS OF 4 INCHES IS FORECAST FOR THE PARTS
OF EASTERN KANSAS AND CENTRAL MISSOURI ON WEDNESDAY,
WITH RAIN TRANSITIONING EASTWARD INTO THE OHIO RIVER
VALLEY AND MID-ATLANTIC BY THE END OF THE WEEK.
SCATTERED PRECIPITATION IS ALSO EXPECTED FOR THE
NORTHERN HIGH PLAINS, WHERE DROUGHT-AFFECTED AREAS
OF SOUTH DAKOTA, MONTANA AND NEBRASKA COULD BENEFIT
FROM 1-2 INCHES OF RAINFALL BY FRIDAY. AN OPTIMISTIC
FORECAST FOR THE SOUTHEAST HAS RAINFALL IN EXCESS OF 2
INCHES OVERSPREADING DROUGHT-STRICKEN AREAS OF EASTERN
TENNESSEE AND NORTHERN GEORGIA OVER THE WEEKEND.
OUT WEST, DRY CONDITIONS ARE EXPECTED TO CONTINUE
FOR MUCH OF CALIFORNIA, ARIZONA AND NEW MEXICO,
WHILE NORTHERN AREAS OF THE GREAT BASIN SHOULD SEE
LIGHT AMOUNTS OF PRECIPITATION /UNDER 1 INCH/ OVER
THE NEXT FIVE DAYS. FOR THE ENSUING 6- TO 10-DAYS
/MAY 12-20/, COOL, WET CONDITIONS ARE EXPECTED FOR
THE EASTERN HALF OF THE NATION, WITH DRIER THAN NORMAL
CONDITIONS FORECAST FOR MUCH OF THE WEST, ALONG WITH
TEMPERATURES MUCH WARMER THAN NORMAL. SOUTH FLORIDA
SHOULD SEE CONTINUED WARM, DRY CONDITIONS DURING THIS
PERIOD, AND SOUTHERN AND EASTERN PARTS OF ALASKA MAY
SEE ABOVE NORMAL PRECIPITATION THROUGH MAY 20, WHILE
SOUTHERN TEXAS IS EXPECTED TO SEE INCREASED WETNESS
DEVELOP BY MAY 14, AFTER AN INITIAL DRY PERIOD OVER
THE NEXT 7 DAYS.
AUTHOR: MICHAEL JAMES/DAVID MISKUS, JAWF/CPC/NOAA
DROUGHT INTENSITY CATEGORIES...
D0 ABNORMALLY DRY...
D1 MODERATE DROUGHT...
D2 SEVERE DROUGHT...
D3 EXTREME DROUGHT...
D4 EXCEPTIONAL DROUGHT
DROUGHT TYPES...
USED ONLY WHEN IMPACTS DIFFER...
A AGRICULTURAL...
H HYDROLOGIC.
$$
