Flood Potential Outlook
Issued by NWS Denver/Boulder, CO

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093-095-115-117-121-123-050000-

WATER SUPPLY OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
529 PM MDT THU APR 17 2014

...SPRING FLOOD AND WATER RESOURCES OUTLOOK...

THIS OUTLOOK IS FOR THE DENVER/BOULDER SERVICE AREA. IT INCLUDES THE
UPPER COLORADO AND NORTH PLATTE RIVER BASINS IN NORTH CENTRAL
COLORADO AND SOUTH PLATTE BASIN EXTENDING ACROSS NORTHEAST COLORADO.

.SPRING SNOWMELT FLOOD OUTLOOK
...IN THE NORTH CENTRAL MOUNTAINS AND NORTHERN COLORADO FRONT RANGE
THE SPRING FLOOD RISK IS ELEVATED. HOWEVER...THE FLOOD POTENTIAL IS
HIGH COMPARED WITH SPRING RUNOFF THE PAST TWO YEARS IN AREAS
SEVERELY IMPACTED BY THE SEPTEMBER 2013 FLOODS.
...ON THE NORTHEAST PLAINS THE FLOOD RISK IS NEAR NORMAL EXCEPT THE
RISK OF FLOODING IS SOMEWHAT ELEVATED ALONG AREA RIVER AND STREAMS
IN SOUTHWEST WELD COUNTY.

THE FLOOD POTENTIAL DUE TO SNOWMELT IS ELEVATED. MUCH ABOVE AVERAGE
APRIL-JULY RUNOFF VOLUMES ARE EXPECTED. MORE SIGNIFICANT FLOODING
WILL OCCUR THIS SPRING IF RAIN FALLS ON THE SNOW...RAPID WARMING
OCCURS AND IF THERE IS MORE SNOW BETWEEN NOW AND THE MELT. THE
THREAT OF SPRING SNOWMELT FLOODING WILL DECREASE WITH GRADUAL OR
INTERMITTENT FREEZING AND THAWING...BELOW AVERAGE PRECIPITATION AND
DRY WINDS.

THERE ARE ADDITIONAL FLOOD CONCERNS THIS SPRING PRIMARILY IN THE
FRONT RANGE FOOTHILLS EXTENDING INTO THE URBAN CORRIDOR OF
BOULDER...LARIMER...SOUTHWEST WELD AND EXTREME NORTHERN JEFFERSON
COUNTIES. AS A RESULT OF LAST SEPTEMBER`S RAIN AND FLOODING...THE
RISK OF FLOODING AND FLASH FLOODING IS HIGHER. A SMALL AMOUNT OF
WATER COULD START MOVING LARGE QUANTITIES OF SEDIMENT IN AFFECTED
STREAMS. THERE ARE REDUCED CREEK AND RIVER CAPACITIES DUE TO THE
INCREASED SEDIMENTATION...ROCKY DEBRIS AND STREAM BANK EROSION.
DEBRIS FLOWS AND LANDSLIDES MAY CAUSE ACCESS ISSUES AND OBSTRUCT
CREEK FLOWS. WOODY DEBRIS ALONG STREAMS COULD POTENTIALLY CAUSE
DEBRIS DAMS AND SUBSEQUENT FLOODING. ALTERED LOCATIONS AND
CONDITIONS OF RIVERS AND CREEKS MAY IMPACT STRUCTURES AND
INFRASTRUCTURES AT RISK. SOME RESERVOIRS IN THESE AREAS ARE AT OR
NEAR CAPACITY AND WILL SPILL EARLIER THAN USUAL CAUSING ADDITIONAL
FLOW DURING THE RUNOFF AND THUNDERSTORM SEASON.

.SNOWPACK...MOUNTAIN SNOWPACK IN NORTH CENTRAL COLORADO REMAINED
WELL ABOVE AVERAGE. THE MOUNTAIN SNOWPACK WAS 142 PERCENT OF NORMAL
IN THE NORTH PLATTE BASIN...136 PERCENT OF NORMAL IN THE SOUTH
PLATTE BASIN AND 127 PERCENT OF NORMAL IN THE UPPER COLORADO RIVER
BASIN ON APRIL 17TH. IN THE NORTH AND SOUTH PLATTE BASINS THIS WAS
ONE OF THEIR 5 HIGHEST MID APRIL SNOWPACKS IN THE PAST 35 YEARS.

.RESERVOIRS...THE SOUTH PLATTE BASIN STORAGE REMAINED 108 PERCENT OF
AVERAGE AND THE UPPER COLORADO RIVER STORAGE WAS 93 PERCENT OF
AVERAGE ON MARCH 31ST. THE UPDATED END OF MARCH COMBINED RESERVOIR
STORAGE WAS 84 PERCENT OF CAPACITY IN THE SOUTH PLATTE BASIN AND 61
PERCENT OF CAPACITY IN THE UPPER COLORADO RIVER BASIN.

.DROUGHT CONDITIONS AND SOIL MOISTURE...CONDITIONS ARE ABNORMALLY
DRY IN THE FAR NORTHEAST PLAINS...WITH SEVERE DROUGHT PERSISTENT IN
SOUTHERN LINCOLN COUNTY. IN CONTRAST...THE SOIL MOISTURE IN AREAS OF THE
NORTH CENTRAL COLORADO MOUNTAINS IS ABOVE AVERAGE.

.CLIMATE SUMMARY...TEMPERATURES WERE GENERALLY 1 TO 5 DEGREES BELOW
AVERAGE IN THE NORTH CENTRAL MOUNTAINS THE PAST TWO WEEKS.
PRECIPITATION VARIED WIDELY.

.PRECIPITATION/TEMPERATURE OUTLOOK...SPRING MOUNTAIN SNOWMELT RUNOFF
WILL INCREASE IN THE NEXT COUPLE OF WEEKS. THE 8 TO 14 DAY OUTLOOK
THROUGH THE END OF APRIL CALLS FOR ABOVE AVERAGE TEMPERATURES AND
BELOW AVERAGE PRECIPITATION. THE OUTLOOK FOR THE MONTH OF MAY CALLS
FOR EQUAL CHANCES OF ABOVE...NEAR OR BELOW AVERAGE PRECIPITATION.
THE MAY THROUGH JULY OUTLOOK HAS ABOVE AVERAGE PRECIPITATION IN THE
FOUR CORNERS REGION INCLUDING COLORADO WITH THE EXCEPTION OF THE FAR
EASTERN PLAINS. THE 30 AND 90 DAY OUTLOOKS HAVE A TILT TOWARD ABOVE
AVERAGE TEMPERATURES IN THE SOUTHERN TWO THIRDS OF COLORADO AND
EQUAL CHANCES OF ABOVE...NEAR OR BELOW AVERAGE TEMPERATURES IN THE
NORTH.

THE NEXT ROUTINE LONG-RANGE PROBABILISTIC RIVER OUTLOOK WILL BE
ISSUED TOWARD THE END OF THIS MONTH. THE NEXT WATER SUPPLY OUTLOOK
WILL BE ISSUED AROUND THE 10TH OF MAY.

$$
TH



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