Flood Potential Outlook
Issued by NWS Denver/Boulder, CO

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PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
414 PM MST THU MAR 6 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.

.FLOOD OUTLOOK...THE POTENTIAL FOR MINOR FLOODING THIS SPRING IS
MODERATE TO HIGH IN THE SOUTH PLATTE RIVER BASIN AND MODERATE IN THE
NORTH PLATTE AND UPPER COLORADO RIVER BASINS IN NORTH CENTRAL
COLORADO.

THE FLOOD POTENTIAL DUE TO SNOWMELT IS ELEVATED. AROUND 20 PERCENT
OF THE SNOW ACCUMULATION SEASON REMAINS AND CONDITIONS COULD CHANGE
BEFORE THE RUNOFF BEGINS. ABOVE NORMAL FUTURE SNOW ACCUMULATIONS
COMBINED WITH HEAVY RAINS AND RAPID MELT WILL INCREASE THE CURRENT
FLOOD POTENTIAL WHILE BELOW NORMAL FUTURE PRECIPITATION AND GRADUAL
OR INTERMITTENT FREEZING AND THAWING WILL DECREASE THE MAGNITUDE OF
THE CURRENT ASSESSMENT.

THERE ARE ADDITIONAL FLOOD CONCERNS THIS SPRING PRIMARILY IN THE
FRONT RANGE FOOTHILLS IN BOULDER...JEFFERSON AND LARIMER COUNTIES
DUE TO THE DESTRUCTIVE SEPTEMBER 2013 FLOODS. RESIDENTS IN AREAS
WHERE STREAM CHANNELS HAVE MOVED OR SIGNIFICANT DEBRIS AND
SEDIMENTATION HAS OCCURRED...SHOULD BE PREPARED FOR LOCALIZED SPRING
SNOWMELT FLOODING. A SMALL AMOUNT OF WATER COULD START MOVING LARGE
QUANTITIES OF SEDIMENT IN AFFECTED STREAMS. DEBRIS FLOWS MAY
OBSTRUCT STREAM CHANNELS AND CAUSE FLOOD ISSUES. THE SEPTEMBER 2013
RAINS LIKELY DESTABILIZED HILLSIDES AND STEEP SLOPES SO INCREASED
LANDSLIDES AND ROCK SLIDES WILL ALSO BE POSSIBLE THIS SPRING
PARTICULARLY WITH HEAVIER OR PROLONGED RAINFALL.

.SNOWPACK...MOUNTAIN SNOWPACK GENERALLY REMAINED ABOVE TO MUCH ABOVE
AVERAGE IN EARLY MARCH WITH NEAR RECORD SNOWPACK OBSERVED AT SEVERAL
LOCATIONS. THE CURRENT HIGH COUNTRY SNOWPACK IS ALREADY NEAR THE
TYPICAL SEASONAL PEAK VALUES EVEN THOUGH THE SNOWPACK USUALLY DOES
NOT REACH ITS PEAK UNTIL APRIL. THE MARCH 6TH MOUNTAIN SNOWPACK IN
THE SOUTH PLATTE RIVER BASIN THIS YEAR AS WELL AS IN 1986 AND 1997
WAS 144 PERCENT OF AVERAGE. THE ONLY YEAR WITH A HIGHER MARCH 6TH
SNOWPACK IN THE SOUTH PLATTE RIVER BASIN DURING THE PAST 35 YEARS
WAS 1996. THE SNOWPACK IN THE NORTH PLATTE AND LARIMIE RIVER BASINS
WAS 136 PERCENT OF AVERAGE WHICH TIED WITH 1997 AS NEARLY THE
HIGHEST MARCH 6TH SNOWPACK BEHIND 1986 AND 1996. THE UPPER COLORADO
RIVER BASIN SNOWPACK WAS 129 PERCENT OF AVERAGE WHICH IS THE NINTH
HIGHEST MARCH 6TH SNOWPACK IN THE COLORADO RIVER HEADWATERS SINCE
1979. LIQUID WATER IN THE SNOTEL MOUNTAIN SNOWPACK GENERALLY RANGED
FROM 4 TO 38 INCHES. AT LOWER ELEVATIONS EAST OF THE DIVIDE THERE
WAS GENERALLY ONLY PATCHY SNOW IN SHADED AREAS.

.RESERVOIRS...THE SOUTH PLATTE BASIN STORAGE WAS 112 PERCENT OF
AVERAGE AND AROUND 83 PERCENT OF CAPACITY ON MARCH 1ST. THE COMBINED
RESERVOIR STORAGE IN THE UPPER COLORADO RIVER BASIN WAS 97 PERCENT
OF AVERAGE AND 64 PERCENT OF CAPACITY.

.RIVER CONDITIONS AND WATER SUPPLY FORECASTS...45 PERCENT OF THE
U.S. GEOLOGICAL SURVEY STREAM GAGES WITH A LONG HISTORICAL RECORD
ARE REPORTING ABOVE NORMAL TO HIGH FLOWS IN NORTH CENTRAL COLORADO
AND 45 PERCENT OF THE GAGES HAVE NEAR NORMAL FLOWS. THE APRIL
THROUGH JULY STREAMFLOW VOLUME FORECASTS HAVE INCREASED TO BETWEEN
113 AND 163 PERCENT OF AVERAGE.
                             MOST PROBABLY FORECAST
                                      VOLUME      PERCENT
STREAM AND STATION         PERIOD     1000 AF      OF AVG
__________________         ______     _______     _______
SOUTH PLATTE RIVER
 ANTERO RESERVOIR INFLOW   APR-JUL      19         131
 SPINNEY MTN RES INFLOW    APR-JUL      65         135
 11-MILE CANYON RES INFLOW APR-JUL      67         134
 CHEESMAN LAKE INFLOW      APR-JUL     137         137
 SOUTH PLATTE              APR-JUL     245         136

BEAR CREEK
 EVERGREEN ABV             APR-JUL      18.5       113
 MORRISON                  APR-JUL      25         114

CLEAR CREEK
 GOLDEN                    APR-JUL     133         127

ST VRAIN CREEK
 LYONS                     APR-JUL     107         122

BOULDER CREEK
 ORODELL                   APR-JUL      67         124

SOUTH BOULDER CREEK
 ELDORADO SPRINGS          APR-JUL      47         121

BIG THOMPSON RIVER
 CANYON MOUTH              APR-JUL     116         129

CACHE LA POUDRE
 CANYON MOUTH              APR-JUL     280         124

NORTH PLATTE RIVER
 NORTHGATE                 APR-JUL     275         122

COLORADO RIVER
 LAKE GRANBY               APR-JUL     310         141

WILLOW CREEK
 WILLOW CREEK RES          APR-JUL      59         126

FRASER RIVER
 WINTER PARK               APR-JUL      28         144

WILLIAMS FORK RIVER
 WILLIAMS FORK RES         APR-JUL     135         141

BLUE RIVER
 DILLON RES                APR-JUL     245         150
 GREEN MTN RES             APR-JUL     395         144

MUDDY CREEK
 WOLFORD MTN RES BLW       APR-JUL      88         163

COLORADO RIVER
 KREMMLING                 APR-JUL    1250         145

.DROUGHT CONDITIONS...SINCE LATE FEBRUARY DROUGHT CONDITIONS IN
EXTREME NORTHEAST COLORADO WERE REDUCED WITH MODERATE DROUGHT /D1/
IN EASTERN PHILLIPS COUNTY REPLACED BY ABNORMALLY DRY CONDITIONS
/D0/. ABNORMALLY DRY CONDITIONS WERE REMOVED FROM
SOUTHEAST LOGAN...SOUTHWEST SEDGWICK...WESTERN PHILLIPS AND
NORTHWEST WASHINGTON COUNTIES. THE SITUATION IN LINCOLN COUNTY
CONTINUED TO VARY FROM SEVERE DROUGHT /D2/ IN THE SOUTH TO
ABNORMALLY DRY CONDITIONS /D0/ IN THE NORTH. ABNORMALLY DRY
CONDITIONS /D0/ REMAINED IN SOUTHERN PARK...SOUTHWEST DOUGLAS AND
EXTREME SOUTHERN JEFFERSON COUNTIES.

.CLIMATE SUMMARY...A PROGRESSIVE WEATHER PATTERN BROUGHT 150 TO OVER
300 PERCENT OF THE AVERAGE PRECIPITATION FROM THE NORTH CENTRAL
MOUNTAINS EASTWARD AND INTERSTATE 70 NORTHWARD THE PAST 30 DAYS. IN
CONTRAST PRECIPITATION RANGED FROM ONLY 25 TO 75 PERCENT OF AVERAGE
IN THE ALREADY DRY OR DROUGHT STRICKEN SOUTHERN SECTIONS OF
DOUGLAS...ELBERT...JEFFERSON...LINCOLN AND PARK COUNTIES.
TEMPERATURES THE PAST MONTH RANGED FROM 2 TO 8 DEGREES ABOVE AVERAGE
IN THE NORTH PLATTE AND UPPER COLORADO RIVER BASINS IN THE MOUNTAINS
TO 2 TO 10 DEGREES BELOW AVERAGE IN THE LOWER SOUTH PLATTE BASIN ON
THE NORTHEAST PLAINS.

.PRECIPITATION/TEMPERATURE OUTLOOK...AN UNSETTLED WEATHER PATTERN
WILL CONTINUE THROUGH MARCH 12TH WITH TWO MORE DISTURBANCES FORECAST
TO BRING SOME PRECIPITATION. THE WEEK TWO OUTLOOK CALLS FOR NEAR
AVERAGE PRECIPITATION AND TEMPERATURES THROUGH MARCH 20TH. THE 90
DAY OUTLOOK CALLS FOR EQUAL CHANCES OF NEAR...ABOVE OR BELOW AVERAGE
PRECIPITATION AND TEMPERATURES THROUGH MAY. THE NWS CLIMATE
PREDICTION CENTER HAS ISSUED AN EL NINO WATCH FOR THE UPCOMING
SUMMER. AN EL NINO WATCH IS ISSUED WHEN CONDITIONS ARE FAVORABLE FOR
THE DEVELOPMENT OF AN EL NINO WITHIN THE NEXT SIX MONTHS.

.LONG-RANGE PROBABILISTIC RIVER OUTLOOK...THE FOLLOWING TABLE GIVES
THE CHANCE OF REACHING FLOOD STAGE AT THE FORECAST POINTS DURING THE
VALID PERIOD.

CS VALUES INDICATE THE PROBABILITY OF REACHING A FLOOD CATEGORY
BASED ON CURRENT CONDITIONS.

HS VALUES INDICATE THE PROBABILITY OF REACHING A FLOOD CATEGORY
BASED ON HISTORICAL OR NORMAL CONDITIONS.

WHEN THE VALUE OF CS IS GREATER THAN HS...THE PROBABILITY OF
EXCEEDING THAT LEVEL IS HIGHER THAN NORMAL. WHEN THE VALUE OF CS IS
LESS THAN HS...THE PROBABILITY OF EXCEEDING THAT LEVEL IS LOWER THAN
NORMAL.

...TABLE 1--PROBABILITIES FOR MINOR...MODERATE AND MAJOR FLOODING...
                  VALID PERIOD:  3/08/2014 - 9/30/2014

                                       :    CURRENT AND HISTORICAL
                                       :     CHANCES OF EXCEEDING
                                       :       FLOOD CATEGORIES
                                       :      AS A PERCENTAGE (%)
                      CATEGORICAL      :
                   FLOOD STAGES (FT)   :   MINOR    MODERATE   MAJOR
LOCATION           MINOR   MOD   MAJOR :  CS   HS   CS   HS   CS   HS
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:SOUTH PLATTE RIVER
SOUTH PLATTE         7.0    9.0   11.0 :   9    9   <5   <5   <5   <5
DENVER              11.0   12.5   14.0 :  <5   <5   <5   <5   <5   <5
HENDERSON           10.0   11.0   15.0 :   8    5    5   <5   <5   <5
KERSEY              10.0   11.5   12.0 :  31   12   17    5   15   <5
WELDONA             10.0   11.0   13.0 :  18    7   10   <5    5   <5
BALZAC              10.0   11.0   13.0 :  27    8   17   <5    8   <5
JULESBURG           10.0   12.0   13.0 :  13    8   <5   <5   <5   <5
:PLUM CREEK
SEDALIA              8.0   10.0   12.0 :  <5   <5   <5   <5   <5   <5
:BEAR CREEK
MORRISON             9.0   10.0   11.0 :  <5   <5   <5   <5   <5   <5
SHERIDAN             8.0   10.0   11.0 :  <5   <5   <5   <5   <5   <5
:CLEAR CREEK
GOLDEN              10.0   13.0   14.0 :  <5   <5   <5   <5   <5   <5
DERBY                9.0   10.5   11.5 :  <5   <5   <5   <5   <5   <5
:N FK BIG THOMPSON RIVER
DRAKE                6.0    7.0    8.0 :  <5   <5   <5   <5   <5   <5
:CACHE LA POUDRE RIVER
FORT COLLINS 9NW     7.5    9.0   10.5 :  16   <5   <5   <5   <5   <5
FORT COLLINS        10.5   11.5   13.0 :  <5   <5   <5   <5   <5   <5
GREELEY              8.0    9.5   11.0 :  28    8    7   <5   <5   <5
:NORTH PLATTE RIVER
NORTHGATE            8.0    9.5   11.0 :  13    6   <5   <5   <5   <5

LEGEND
CS = CONDITIONAL SIMULATION (CURRENT OUTLOOK)
HS = HISTORICAL SIMULATION
FT = FEET

IN TABLE 2 BELOW...THE 95 THROUGH 5 PERCENT COLUMNS INDICATE THE
PROBABILITY OF EXCEEDING THE LISTED STAGE LEVELS (FT) FOR THE VALID
TIME PERIOD.

...TABLE 2--EXCEEDANCE PROBABILITIES...

                              CHANCE OF EXCEEDING STAGES
                                 AT SPECIFIC LOCATIONS

LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:SOUTH PLATTE RIVER
SOUTH PLATTE          4.2    4.4    4.6    5.2    5.6    6.9    7.7
DENVER                5.1    5.4    5.7    6.1    6.7    7.6    8.0
HENDERSON             6.4    6.6    7.1    7.9    8.9    9.4   10.8
KERSEY                6.4    6.7    7.8    8.8   10.6   12.8   16.9
WELDONA               5.2    5.6    6.7    8.0    9.6   11.1   13.0
BALZAC                6.0    6.1    7.5    8.2   10.2   12.0   13.7
JULESBURG             6.3    6.6    7.4    8.2    9.0   10.3   11.4
:PLUM CREEK
SEDALIA               4.4    4.5    4.6    4.7    5.0    5.4    6.1
:BEAR CREEK
MORRISON              6.5    6.5    6.8    6.9    7.1    7.5    7.7
SHERIDAN              2.9    3.2    3.3    3.8    4.4    4.9    5.3
:CLEAR CREEK
GOLDEN                6.1    6.3    6.4    6.8    7.3    7.7    8.0
DERBY                 2.5    2.6    2.9    3.2    3.7    4.2    4.4
:N FK BIG THOMPSON RIVER
DRAKE                 4.4    4.4    4.5    4.6    4.7    4.8    5.1
:CACHE LA POUDRE RIVER
FORT COLLINS 9NW      4.8    5.2    5.5    5.8    6.8    8.5    8.6
FORT COLLINS          5.1    5.5    6.0    6.5    7.7    9.8   10.2
GREELEY               6.0    6.4    7.0    7.5    8.1    9.3    9.7
:NORTH PLATTE RIVER
NORTHGATE             5.3    5.6    6.0    6.7    7.8    8.1    9.0

THESE LONG-RANGE PROBABILISTIC OUTLOOKS CONTAIN FORECAST VALUES THAT
ARE CALCULATED USING MULTIPLE SEASON SCENARIOS FROM 30 OR MORE YEARS
OF CLIMATOLOGICAL DATA...INCLUDING CURRENT CONDITIONS OF THE
RIVER...SOIL MOISTURE...SNOW COVER...AND 30 TO 90 DAY LONG-RANGE
OUTLOOKS OF TEMPERATURE AND PRECIPITATION. BY PROVIDING A RANGE OF
PROBABILITIES...THE LEVEL OF RISK ASSOCIATED WITH LONG-RANGE
PLANNING DECISIONS CAN BE DETERMINED. THESE PROBABILISTIC FORECASTS
ARE PART OF THE NATIONAL WEATHER SERVICE`S ADVANCED HYDROLOGIC
PREDICTION SERVICE.

VISIT OUR WEB SITE AT WEATHER.GOV/DENVER FOR MORE HYDROLOGIC
INFORMATION INCLUDING GRAPHS OF PROBABILISTIC RIVER OUTLOOKS.

THE NEXT ROUTINE LONG-RANGE PROBABILISTIC RIVER OUTLOOK WILL BE
ISSUED TOWARD THE END OF THIS MONTH.

$$
TH



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