Flood Potential Outlook
Issued by NWS Denver/Boulder, CO

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FGUS75 KBOU 052226
ESFBOU
COC001-005-013-014-019-031-035-039-047-049-057-059-069-073-075-087-
093-095-115-117-121-123-230000-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
326 PM MST THU MAR 5 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 SPRING RUNOFF FLOOD POTENTIAL DUE TO SNOWMELT IS NEAR TO BELOW
NORMAL IN NORTH CENTRAL AND NORTHEAST COLORADO. THE LONG TERM
STANDARDIZED PRECIPITATION INDEX REVEALED MAINLY WET CONDITIONS IN
NORTH CENTRAL COLORADO WITH DRYNESS ON THE NORTHEAST PLAINS.
MOUNTAIN SNOWPACK IS NEAR TO SLIGHTLY ABOVE AVERAGE. SIGNIFICANT
FLOODING DUE TO SNOWMELT ALONE IS NOT EXPECTED THIS SPRING.

IT SHOULD BE EMPHASIZED THAT SNOW TYPICALLY ACCUMULATES INTO APRIL.
THEREFORE 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...
A WEATHER PATTERN CHANGE OCCURRED IN MID FEBRUARY AS STORMS BEGAN
BOOSTING THE SNOWFALL...EXCEPT ON THE FAR NORTHEAST PLAINS. BY MARCH
5TH THE MOUNTAIN SNOWPACK IMPROVED TO 113 PERCENT OF AVERAGE IN THE
SOUTH PLATTE RIVER BASIN...98 PERCENT OF AVERAGE IN THE UPPER
COLORADO RIVER BASIN AND 94 PERCENT OF AVERAGE IN THE NORTH PLATTE
BASIN. IN THE NORTH CENTRAL COLORADO SNOW WATER EQUIVALENT IN THE
HIGH COUNTRY SNOWPACK RANGED FROM 5 TO 30 INCHES AT NRCS SNOTEL
SITES. OBSERVERS ALONG THE URBAN CORRIDOR REPORTED UP TO 6 INCHES OF
SNOW ON THE GROUND WITH SNOW WATER EQUIVALENTS LESS THAN AN INCH AND
A HALF. SNOW DEPTHS IN THE COLORADO PLAINS REGION RANGE FROM NO SNOW
TO SEVERAL INCHES.

RESERVOIR STORAGE REMAINED IN GOOD CONDITION. ON MARCH 1ST THE
COMBINED RESERVOIR STORAGE WAS 117 PERCENT OF AVERAGE OR 87 PERCENT
OF CAPACITY IN THE SOUTH PLATTE BASIN AND 120 PERCENT OF AVERAGE OR
79 PERCENT OF CAPACITY IN THE UPPER COLORADO RIVER BASIN.

AS THE SNOWPACK CONTINUED TO SLOWLY CLIMB...NUMEROUS USGS STREAM
GAGES ACROSS NORTH CENTRAL COLORADO CONTINUED TO RECORD ABOVE NORMAL
FLOWS. ON MARCH 5TH...35 PERCENT OF USGS GAGES WITH A LONG
HISTORICAL RECORD HAD NORMAL FLOWS...20 PERCENT HAD ABOVE NORMAL
FLOWS AND 45 PERCENT HAD MUCH ABOVE NORMAL TO HIGH STREAMFLOWS.

...CLIMATE SUMMARY...
THE MOST NOTABLE FEBRUARY STORM OCCURRED FROM FEBRUARY 20TH THROUGH
THE 22ND. THIS STORM BROUGHT 8 TO 24 INCHES OF SNOW TO THE FRONT
RANGE URBAN CORRIDOR AND PALMER DIVIDE. PRECIPITATION THE PAST 2
WEEKS WAS 2 TO 5 INCHES ABOVE AVERAGE ALONG AND JUST EAST OF THE
CONTINENTAL DIVIDE IN BOULDER...GILPIN AND LARIMER COUNTIES.
ELSEWHERE PRECIPITATION GENERALLY RANGED FROM NEAR TO 2 INCHES ABOVE
AVERAGE. THE EXCEPTION WAS THE NORTHEAST CORNER OF COLORADO WHERE
TOTALS HAVE BEEN UP TO A HALF INCH BELOW AVERAGE.

TEMPERATURES THE PAST 2 WEEKS RANGED FROM 0 TO 6 DEGREES BELOW
AVERAGE WEST OF THE CONTINENTAL DIVIDE AND IN THE NORTH AND SOUTH
PARK AREAS. TEMPERATURES HAVE BEEN 6 TO 15 DEGREES BELOW AVERAGE
ELSEWHERE EAST OF THE DIVIDE.

...WEATHER OUTLOOK...
A RIDGE OF HIGH PRESSURE BUILDS OVER THE WESTERN U.S. BRINGING
MOSTLY DRY CONDITIONS TO COLORADO THROUGH MARCH 12TH. THE ATMOSPHERE
WILL ALSO CONTINUE TO WARM AND BY EARLY NEXT WEEK TEMPERATURES WILL
RISE ABOVE AVERAGE. THE MARCH 13TH THROUGH 19TH OUTLOOK CALLS FOR
WARM AND WETTER CONDITIONS. THE OUTLOOK FOR THE MONTH OF MARCH CALLS
FOR EQUAL CHANCES OF ABOVE...NEAR OR BELOW AVERAGE TEMPERATURES AND
PRECIPITATION EXCEPT THERE IS A TILT TOWARD BELOW AVERAGE
TEMPERATURES ON THE FAR EASTERN PLAINS.

EL NINO CONDITIONS ARE OCCURRING ACROSS THE WESTERN AND CENTRAL
EQUATORIAL PACIFIC. OVERALL THESE FEATURES ARE CONSISTENT WITH
BORDERLINE WEAK EL NINO CONDITIONS. THERE IS A 50 TO 60 PERCENT
CHANCE EL NINO CONDITIONS WILL CONTINUE THROUGH THIS SUMMER. THE
STRENGTH OF THE EL NINO IS EXPECTED TO REMAIN WEAKER. COLORADO TENDS
TO EXPERIENCE MORE SIGNIFICANT OR WIDESPREAD EFFECTS WHEN AN EL NINO
IS MODERATE TO STRONG.

...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:  3/7/2015 - 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 :  17   12   12    5   11   <5
WELDONA             10.0   11.0   13.0 :  10    7    9   <5    5   <5
BALZAC              10.0   11.0   13.0 :  23    8   16   <5    7   <5
JULESBURG           10.0   12.0   13.0 :   9    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 :   6   <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 :  15    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...

                              CHANCE OF EXCEEDING STAGES
                                 AT SPECIFIC LOCATIONS
                          VALID PERIOD:  3/7/2015 - 9/30/2015

LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:SOUTH PLATTE RIVER
SOUTH PLATTE          4.0    4.2    4.4    4.9    5.4    6.6    7.4
DENVER                4.8    5.3    5.6    6.0    6.7    7.6    8.1
HENDERSON             6.2    6.5    7.1    7.4    8.6    9.2   10.6
KERSEY                5.4    5.7    6.6    7.7    9.3   12.1   14.9
WELDONA               4.5    4.8    5.4    6.5    8.2   10.2   12.7
BALZAC                5.2    5.6    6.4    7.7    9.8   11.9   13.4
JULESBURG             5.2    5.6    6.3    7.5    8.3    9.8   10.8
:PLUM CREEK
SEDALIA               3.9    4.0    4.3    4.5    5.3    6.6    8.3
:BEAR CREEK
MORRISON              6.7    6.7    6.9    7.0    7.2    7.6    7.7
SHERIDAN              3.1    3.3    3.5    3.8    4.4    4.7    5.1
:CLEAR CREEK
GOLDEN                5.2    5.2    5.5    5.9    6.4    6.9    7.2
DERBY                 2.5    2.6    2.8    3.1    3.5    3.9    5.0
: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    6.7    8.2
FORT COLLINS          3.7    4.1    4.6    5.1    5.7    7.0    9.1
GREELEY               4.0    4.2    5.6    6.4    7.5    8.3    9.1
:NORTH PLATTE RIVER
NORTHGATE             4.2    4.5    4.9    5.6    6.4    7.0    7.4

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...

                            CHANCE OF FALLING BELOW STAGES
                                 AT SPECIFIC LOCATIONS
                          VALID PERIOD:  3/7/2015 - 9/30/2015

LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:SOUTH PLATTE RIVER
SOUTH PLATTE          2.1    2.1    2.1    2.1    2.1    2.1    2.1
DENVER                3.2    3.2    3.1    3.1    3.1    3.1    3.0
HENDERSON             4.9    4.9    4.7    4.6    4.5    4.5    4.5
KERSEY                3.5    3.3    3.0    2.7    2.2    2.0    1.9
WELDONA               3.0    2.8    2.7    2.6    2.6    2.5    2.5
BALZAC                1.1    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              5.9    5.9    5.9    5.8    5.8    5.7    5.6
SHERIDAN              2.6    2.5    2.4    2.3    2.2    2.1    2.1
:CLEAR CREEK
GOLDEN                3.4    3.4    3.4    3.4    3.4    3.3    3.3
DERBY                 2.1    0.5    0.5    0.5    0.5    0.5    0.5
:N FK BIG THOMPSON RIVER
DRAKE                 3.6    3.6    3.6    3.6    3.6    3.6    3.6
:CACHE LA POUDRE RIVER
FORT COLLINS 9NW      3.1    3.0    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    2.7    2.6    2.6    2.6    2.6    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. THE
HEADWATERS IN THE UPPER COLORADO AND SOUTH PLATTE RIVER BASINS ARE
FORECAST TO HAVE NEAR TO ABOVE AVERAGE PEAK FLOWS.

                              MOST PROBABLY FORECAST

                                      VOLUME      PERCENT
STREAM AND STATION         PERIOD     1000 AF      OF AVG
__________________         ______     _______     _______
COLORADO RIVER
 LAKE GRANBY               APR-JUL     230         105

WILLOW CREEK
 WILLOW CREEK RES          APR-JUL      44          94

FRASER RIVER
 WINTER PARK               APR-JUL      20         103

WILLIAMS FORK RIVER
 WILLIAMS FORK RES         APR-JUL     100         104

BLUE RIVER
 DILLON RES                APR-JUL     188         115
 GREEN MTN RES             APR-JUL     310         113

MUDDY CREEK
 WOLFORD MTN RES BLW       APR-JUL      50          93

COLORADO RIVER
 KREMMLING                 APR-JUL     910         106

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

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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