Flood Potential Outlook
Issued by NWS Denver/Boulder, CO

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FGUS75 KBOU 192202
ESFBOU
COC001-005-013-014-019-031-035-039-047-049-057-059-069-073-075-087-
093-095-115-117-121-123-050000-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
302 PM MST THU FEB 19 2015

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

THIS OUTLOOK IS FOR THE UPPER COLORADO AND NORTH PLATTE RIVER BASINS
IN NORTH CENTRAL COLORADO AND SOUTH PLATTE BASIN WHICH ALSO EXTENDS
ACROSS NORTHEAST COLORADO.

...FLOOD OUTLOOK...
THE FLOOD RISK THIS SPRING IS NEAR TO BELOW NORMAL IN NORTH CENTRAL
AND NORTHEAST COLORADO. THE COMBINATION OF NEAR TO BELOW AVERAGE
MOUNTAIN SNOWPACK...DRIER THAN NORMAL SUBSURFACE SOILS IN AREAS AND
DIMINISHED FROZEN GROUND HAVE COMBINED TO MAKE THE RISK OF
SIGNIFICANT SPRING SNOWMELT FLOODING LOW.

IT SHOULD BE NOTED THAT IT IS STILL EARLY IN THE SNOW ACCUMULATION
SEASON 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. NEAR
NORMAL RISK SUGGESTS THAT LOCATIONS WHICH TYPICALLY EXPERIENCE MINOR
SPRING TIME FLOODING MAY FLOOD AGAIN THIS YEAR. THOSE LOCATIONS THAT
DO NOT NORMALLY EXPERIENCE FLOODING ARE NOT PROJECTED TO FLOOD THIS
YEAR.

...CURRENT HYDROLOGIC CONDITIONS...
THE FEBRUARY 19TH MOUNTAIN SNOWPACK IN NORTH CENTRAL COLORADO RANGED
FROM 100 PERCENT OF AVERAGE FOR THE SOUTH PLATTE RIVER BASIN...89
PERCENT OF AVERAGE IN THE UPPER COLORADO RIVER BASIN AND 84 PERCENT
OF AVERAGE IN THE NORTH PLATTE BASIN. LIQUID WATER IN THE HIGH
COUNTRY SNOWPACK GENERALLY RANGED FROM 3 TO 25 INCHES. THE FEBRUARY
1ST SUB-BASIN SNOWPACK RANGED FROM 122 PERCENT OF NORMAL IN THE BLUE
RIVER BASIN WEST OF THE DIVIDE TO 88 PERCENT OF NORMAL IN THE
BOULDER CREEK BASIN EAST OF THE DIVIDE. THERE WAS TYPICALLY A TRACE
TO 4 INCHES OF SNOW ALONG THE FRONT RANGE URBAN CORRIDOR THE MORNING
OF FEBRUARY 19TH. HOWEVER...BY AFTERNOON THE SNOW AT LOWER
ELEVATIONS WAS MELTING RAPIDLY AS TEMPERATURES IN THE DENVER METRO
AREA CLIMBED INTO THE LOWER 60S. MINIMAL TO NO SNOW EXISTS ON THE
NORTHEAST AND EAST CENTRAL PLAINS.

RESERVOIR STORAGE SINCE THE BEGINNING OF THE WATER YEAR HAS BEEN
FALLING IN THE SOUTH PLATTE BASIN AND SLOWLY RISING IN THE UPPER
COLORADO RIVER BASIN BUT BASIN STORAGE REMAINS ABOVE AVERAGE. THE
COMBINED RESERVOIR STORAGE WAS 119 PERCENT OF AVERAGE OR 84 PERCENT
OF CAPACITY IN THE SOUTH PLATTE BASIN AND 116 PERCENT OF AVERAGE OR
80 PERCENT OF CAPACITY IN THE UPPER COLORADO RIVER BASIN.

WITH ABOVE AVERAGE TEMPERATURES PREVAILING SINCE THE BEGINNING OF
THE CALENDAR YEAR...THE U.S. GEOLOGICAL SURVEY STREAM GAGES WERE
REPORTING NORMAL TO HIGH FLOWS ON FEBRUARY 19TH. 38 PERCENT OF THEIR
GAGES IN NORTH CENTRAL COLORADO HAD NORMAL STREAMFLOWS...24 PERCENT
HAD ABOVE NORMAL FLOWS AND 38 PERCENT HAD MUCH ABOVE NORMAL TO HIGH
STREAMFLOWS.

...CLIMATE SUMMARY...
PRECIPITATION SINCE JANUARY 1ST RANGED FROM 0.5 TO 1.5 INCHES ABOVE
AVERAGE IN THE DENVER METRO...SOUTH PARK AND PALMER DIVIDE AREAS AND
NEAR TO 0.75 INCH BELOW AVERAGE ON THE NORTHEAST AND EAST CENTRAL
PLAINS AND 0.25 TO 2.25 INCHES BELOW AVERAGE IN GRAND...JACKSON AND
SUMMIT COUNTIES IN NORTH CENTRAL COLORADO. TEMPERATURES THIS
CALENDAR YEAR HAVE GENERALLY BEEN 6 TO 10 DEGREES ABOVE AVERAGE IN
THE NORTH PLATTE RIVER BASIN IN JACKSON COUNTY...4 TO 8 DEGREES
ABOVE AVERAGE IN THE HEADWATERS OF THE UPPER COLORADO AND SOUTH
PLATTE RIVER BASINS IN NORTH CENTRAL COLORADO AND 2 TO 6 DEGREES
ABOVE AVERAGE IN NORTHEAST COLORADO.

...WEATHER AND DROUGHT OUTLOOKS...
THE 8 TO 14 DAY AND 90 DAY OUTLOOKS CALL FOR ABOVE AVERAGE
PRECIPITATION. THE 30 DAY OUTLOOK FOR MARCH HAS EQUAL CHANCES OF
NEAR...ABOVE OR BELOW AVERAGE PRECIPITATION.

THE 8 TO 14 DAY OUTLOOK CALLS FOR BELOW AVERAGE TEMPERATURES. THE 30
AND 90 DAY OUTLOOKS INDICATE EQUAL CHANCES OF NEAR...ABOVE OR BELOW
AVERAGE TEMPERATURES EXCEPT THERE IS A TILT TOWARD ABOVE AVERAGE
TEMPERATURES IN NORTH CENTRAL COLORADO DURING MARCH.

THE U.S. SEASONAL DROUGHT OUTLOOK VALID FEBRUARY 19TH THROUGH MAY
31ST INDICATES DROUGHT CONDITIONS WILL NOT OCCUR IN NORTH CENTRAL OR
NORTHEAST COLORADO.

...NUMERICAL RIVER OUTLOOKS...
IN TABLE 1 BELOW, THE CURRENT (CS) AND HISTORICAL (HS) OR NORMAL
PROBABILITIES OF EXCEEDING MINOR...MODERATE...AND MAJOR FLOOD STAGES
ARE LISTED FOR THE VALID TIME 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:  2/21/2015 - 9/30/2015

                                       :    CURRENT AND HISTORICAL
                                       :     CHANCES OF EXCEEDING
                                       :       FLOOD CATERGORIES
                                       :      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 :   6    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 :  16   12   12    5   10   <5
WELDONA             10.0   11.0   13.0 :  10    7    7   <5   <5   <5
BALZAC              10.0   11.0   13.0 :  22    8   13   <5    5   <5
JULESBURG           10.0   12.0   13.0 :   8    8   <5   <5   <5   <5
:PLUM CREEK
SEDALIA              8.0   10.0   12.0 :   7   <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 :   7   <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 :  17    8   <5   <5   <5   <5
:NORTH PLATTE RIVER
NORTHGATE            8.0    9.5   11.0 :  <5    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...
                        VALID PERIOD:  2/21/2015 - 9/30/2015

                              CHANCE OF EXCEEDING STAGES
                                 AT SPECIFIC LOCATIONS

LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:SOUTH PLATTE RIVER
SOUTH PLATTE          4.0    4.2    4.3    4.8    5.2    6.5    7.3
DENVER                4.7    5.3    5.5    6.0    6.6    7.5    8.1
HENDERSON             6.0    6.4    7.1    7.4    8.6    9.2   10.6
KERSEY                5.0    5.5    6.5    7.5    9.0   12.0   14.1
WELDONA               4.4    4.5    5.4    6.5    8.0   10.1   12.2
BALZAC                4.6    5.0    6.3    7.3    9.4   11.8   12.9
JULESBURG             4.9    5.1    6.1    7.1    8.2    9.7   10.7
:PLUM CREEK
SEDALIA               3.9    4.0    4.3    4.5    5.3    6.8    8.2
:BEAR CREEK
MORRISON              6.6    6.7    6.9    7.0    7.2    7.5    7.8
SHERIDAN              3.0    3.3    3.5    3.7    4.3    4.6    5.1
:CLEAR CREEK
GOLDEN                5.1    5.2    5.5    5.9    6.5    7.0    7.3
DERBY                 2.5    2.6    2.8    3.1    3.5    3.9    4.4
:N FK BIG THOMPSON RIVER
DRAKE                 4.3    4.3    4.4    4.5    4.6    4.8    5.0
:CACHE LA POUDRE RIVER
FORT COLLINS 9NW      4.3    4.5    4.8    5.2    5.7    7.3    8.0
FORT COLLINS          3.6    4.0    4.6    5.1    5.6    7.6    8.9
GREELEY               3.4    4.1    5.5    6.3    7.3    8.4    9.2
:NORTH PLATTE RIVER
NORTHGATE             4.0    4.4    4.8    5.6    6.4    7.0    7.6

IN TABLE 3 BELOW...THE 95 THROUGH 5 PERCENT COLUMNS INDICATE THE
PROBABILITY OF FALLING BELOW THE LISTED STAGE LEVELS (FT) FOR
THE VALID TIME PERIOD.
                      ...TABLE 3--NONEXCEEDANCE PROBABILITIES...
                         VALID PERIOD:  2/21/2015 - 9/30/2015

                            CHANCE OF FALLING BELOW STAGES
                                 AT SPECIFIC LOCATIONS

LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:SOUTH PLATTE RIVER
SOUTH PLATTE          2.2    2.2    2.2    2.2    2.2    2.2    2.2
DENVER                3.2    3.2    3.1    3.1    3.1    3.0    3.0
HENDERSON             4.8    4.8    4.7    4.6    4.5    4.5    4.5
KERSEY                3.4    3.3    2.9    2.5    2.1    1.9    1.9
WELDONA               2.9    2.8    2.6    2.6    2.6    2.5    2.5
BALZAC                1.0    1.0    1.0    1.0    1.0    1.0    1.0
JULESBURG             1.0    1.0    1.0    1.0    1.0    1.0    1.0
:PLUM CREEK
SEDALIA               3.1    3.1    3.1    3.1    3.1    3.1    3.1
:BEAR CREEK
MORRISON              6.0    6.0    5.9    5.9    5.8    5.7    5.6
SHERIDAN              2.5    2.5    2.5    2.3    2.2    2.1    2.1
:CLEAR CREEK
GOLDEN                3.4    3.4    3.4    3.4    3.4    3.4    3.3
DERBY                 0.8    0.5    0.5    0.5    0.5    0.5    0.5
:N FK BIG THOMPSON RIVER
DRAKE                 3.7    3.7    3.7    3.6    3.6    3.6    3.6
:CACHE LA POUDRE RIVER
FORT COLLINS 9NW      3.1    3.1    3.0    3.0    3.0    3.0    3.0
FORT COLLINS          1.1    1.1    1.1    1.1    1.1    1.1    1.1
GREELEY               1.6    1.6    1.5    1.5    1.5    1.5    1.5
:NORTH PLATTE RIVER
NORTHGATE             2.7    2.6    2.6    2.6    2.6    2.5    2.5

THE LONG-RANGE PROBABILISTIC OUTLOOKS ABOVE 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.

FOLLOWING ARE THE STREAMFLOW FORECASTS FOR SELECTED LOCATIONS:
                              MOST PROBABLY FORECAST
                                      VOLUME      PERCENT
STREAM AND STATION         PERIOD     1000 AF      OF AVG
__________________         ______     _______     _______
SOUTH PLATTE RIVER
 ANTERO RESERVOIR INFLOW   APR-JUL      12.5        86
 SPINNEY MTN RES INFLOW    APR-JUL      44          92
 11-MILE CANYON RES INFLOW APR-JUL      46          92
 CHEESMAN LAKE INFLOW      APR-JUL      95          95
 SOUTH PLATTE              APR-JUL     170          94

BEAR CREEK
 EVERGREEN ABV             APR-JUL      15.6        95

CLEAR CREEK
 GOLDEN                    APR-JUL      99          94

ST VRAIN CREEK
 LYONS                     APR-JUL      84          95

BOULDER CREEK
 ORODELL                   APR-JUL      52          96

SOUTH BOULDER CREEK
 ELDORADO SPRINGS          APR-JUL      36          92

BIG THOMPSON RIVER
 CANYON MOUTH              APR-JUL      85          94

CACHE LA POUDRE
 CANYON MOUTH              APR-JUL     205          91

NORTH PLATTE RIVER
 NORTHGATE                 APR-JUL     137          61

COLORADO RIVER
 LAKE GRANBY               APR-JUL     215          98

WILLOW CREEK
 WILLOW CREEK RES          APR-JUL      42          89

FRASER RIVER
 WINTER PARK               APR-JUL      19.0        98

WILLIAMS FORK RIVER
 WILLIAMS FORK RES         APR-JUL      95          99

BLUE RIVER
 DILLON RES                APR-JUL     183         112
 GREEN MTN RES             APR-JUL     300         109

MUDDY CREEK
 WOLFORD MTN RES BLW       APR-JUL      48          89

COLORADO RIVER
 KREMMLING                 APR-JUL     850          99

THE STREAMFLOW FORECASTS ABOVE REFLECT NATURAL FLOW ONLY. ACTUAL
OBSERVED FLOW WILL LIKELY BE AFFECTED BY UPSTREAM WATER MANAGEMENT.

SPRING FLOOD OUTLOOKS ARE ROUTINELY ISSUED IN FEBRUARY AND MARCH TO
GIVE ADVANCED NOTICE OF POSSIBLE FLOODING. THE NEXT SCHEDULED SPRING
FLOOD OUTLOOK WILL BE ISSUED ON MARCH 5TH.

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

$$
TH



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