Climatological Report (Monthly)
Issued by NWS Denver/Boulder, CO

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CXUS55 KBOU 030136 CCA
CLMDEN

CLIMATE REPORT
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
244 AM MDT THU JUN 1 2017

...................................

...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF MAY 2017...

CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1872 TO 2017

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR`S
                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)
                                          NORMAL
................................................................
TEMPERATURE (F)
RECORD
 HIGH              95   05/26/1942
 LOW               19   05/02/2013
                        05/03/1907
                        01/01/2000
HIGHEST            86   05/06        95      -9       83  05/21
LOWEST             32   05/04        19      13       28  05/02
AVG. MAXIMUM     69.6              71.5    -1.9     66.9
AVG. MINIMUM     42.3              42.7    -0.4     41.9
MEAN             55.9              57.1    -1.2     54.4
DAYS MAX >= 90      0               0.8    -0.8        0
DAYS MAX <= 32      0               0.0     0.0        0
DAYS MIN <= 32      1               1.9    -0.9        3
DAYS MIN <= 0       0               0.0     0.0        0

PRECIPITATION (INCHES)
RECORD
 MAXIMUM         8.57   1876
 MINIMUM         0.06   1974
TOTALS           3.66              2.12    1.54     2.38
DAILY AVG.       0.12              0.07    0.05     0.08
DAYS >= .01        17               9.4     7.6       13
DAYS >= .10        11               4.8     6.2        4
DAYS >= .50         2               1.2     0.8        1
DAYS >= 1.00        1               0.2     0.8        1
GREATEST
 24 HR. TOTAL    1.13   05/18 TO 05/18           05/26 TO 05/27
                                                 05/01 TO 05/01
                                                 05/01 TO 05/01

SNOWFALL (INCHES)
RECORD            15.5 1898
TOTAL                T 2017         1.1

DEGREE_DAYS
HEATING TOTAL     281               265      16      326
 SINCE 7/1       5084              5996    -912     5556
COOLING TOTAL       6                21     -15        3
 SINCE 1/1          6                22     -16        3

FREEZE DATES
RECORD
 EARLIEST     09/08/1962
 LATEST       06/08/2007
EARLIEST                        10/07
LATEST                          05/05
..................................................

WIND (MPH)
AVERAGE WIND SPEED              10.6
RESULTANT WIND SPEED/DIRECTION   0/229
HIGHEST WIND SPEED/DIRECTION    43/230    DATE  05/07
HIGHEST GUST SPEED/DIRECTION    52/230    DATE  05/07

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM
AVERAGE SKY COVER           0.60
NUMBER OF DAYS FAIR            6
NUMBER OF DAYS PC             19
NUMBER OF DAYS CLOUDY          6

AVERAGE RH (PERCENT)     59

WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM              0     MIXED PRECIP               0
HEAVY RAIN                4     RAIN                      10
LIGHT RAIN               17     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       1
HEAVY SNOW                0     SNOW                       2
LIGHT SNOW                2     SLEET                      0
FOG                      15     FOG W/VIS <= 1/4 MILE      0
HAZE                      0

-  INDICATES NEGATIVE NUMBERS.
R  INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T  INDICATES TRACE AMOUNT.

...MAY 2017...WETTER AND SLIGHTLY COOLER THAN NORMAL...

FOR THE FIRST FEW DAYS OF THE MONTH, AN UPPER LEVEL TROUGH OF LOW
PRESSURE COVERED THE CENTRAL AND EASTERN UNITED STATES, WHILE AN
UPPER LEVEL RIDGE OF HIGH PRESSURE CENTERED OVER THE WEST COAST OF
THE U.S.  COLORADO WAS LOCATED BETWEEN THESE TWO SYSTEMS, UNDER THE
INFLUENCE OF A MODERATE NORTHWESTERLY FLOW ALOFT. THIS PATTERN
ALLOWED A FEW COLD FRONTS TO MOVE ACROSS NORTHEASTERN COLORADO,
RESULTING IN SLIGHTLY BELOW NORMAL TEMPERATURES AN LIGHT
PRECIPITATION ACROSS THE FRONT RANGE URBAN CORRIDOR.

DENVER EXPERIENCED DRY WEATHER AND VERY WARM TEMPERATURES FROM THE
5TH THROUGH THE 7TH AS UPPER LEVEL HIGH PRESSURE BUILT OVER THE
ROCKY MOUNTAIN REGION. ON MAY 8TH, THE UPPER HIGH SHIFTED EASTWARD
OVER THE CENTRAL PLAINS, AS A LARGE UPPER LEVEL STORM SYSTEM
APPROACHED THE DESERT SOUTHWEST. WEAK UPSLOPE FLOW BEHIND THE
PASSAGE OF A WEAK MORNING COLD FRONT PRODUCED UPSLOPE FLOW ACROSS
THE FRONT RANGE URBAN CORRIDOR AND PALMER DIVIDE. INCREASED MOISTURE
ASSOCIATED WITH THIS UPSLOPE FLOW COMBINED WITH LIFT FROM THE UPPER
LOW AND ADEQUATE WIND SHEAR RESULTED IN A ROUND OF SEVERE WEATHER
ACROSS THAT MOVED OVER THE METRO DENVER DURING THE AFTERNOON.
BETWEEN 3 AND 4 PM A SUPERCELL THUNDERSTORM IMPACTED METRO DENVER
WITH HEAVY RAIN AND VERY LARGE HAIL THAT FELL AT SIZES UP TO 2.75
INCHES OR THE SIZE OF BASEBALLS. THIS HAILSTORM WAS THE COSTLIEST
HAILSTORM IN COLORADO HISTORY AND 3RD COSTLIEST IN U.S HISTORY. THE
OFFICIAL OBSERVING SITE AT DENVER INTERNATIONAL AIRPORT RECEIVED
ALMOST ONE HALF INCH OF PRECIPITATION WITH THIS STORM AND MANAGED TO
AVOID ANY HAIL.

A CUT OFF LOW MOVED SOUTHEAST FROM THE PACIFIC COAST OF WASHINGTON
STATE INTO IDAHO ON MAY 17. AT THIS TIME THE DEEP LOW PRESSURE
TROUGH EXTENDED DOWN THROUGH COLORADO BRINGING THE START OF A LARGE
SPRING SNOW STORM WHICH MOVED IN THE EVENING OF THE 17TH AND LASTED
THROUGH MIDDAY ON THE 19TH. THIS STORM BLANKETED THE MOUNTAINS,
FOOTHILLS, AND NEARBY PLAINS WITH HEAVY SNOW. THE AREAS ACROSS THE
NORTHERN FOOTHILLS SAW THE MOST SNOW, WITH BUCKHORN MOUNTAIN
RECEIVING 47 INCHES OF SNOW AND ALLENSPARK MEASURING 42 INCHES.
DENVER DID NOT EXPERIENCE NEARLY AS MUCH SNOWFALL. REPORTS OF LESS
THAN AN INCH IN SOUTHWEST DENVER AND DENVER INTERNATIONAL AIRPORT
ONLY SEEING A TRACE.

THE LAST WEEK AND A HALF OF MAY CONTAINED ALMOST DAILY CHANCES OF
SHOWER AND STORMS. THE NORTHEAST PLAINS OF COLORADO SAW A FEW SEVERE
STORMS WITH HAIL UP TO PING PONG BALL SIZE AND A COUPLE WEAK
TORNADOES.

TEMPERATURES:

THE AVERAGE TEMPERATURE AT DENVER INTERNATIONAL AIRPORT FOR THE
MONTH WAS 55.9 DEGREES F, WHICH IS 1.2 DEGREES BELOW NORMAL. THE
WARMEST MAY ON RECORD OCCURRED IN 1934 WITH AN AVERAGE MONTHLY
TEMPERATURE OF 64.7 DEGREES F. THE COLDEST MAY ON RECORD WAS 48.7
DEGREES BACK IN 1917. ON THE 6TH...THE TEMPERATURE CLIMBED TO 86
DEGREES F WHICH IS THE HIGHEST TEMPERATURE OF THE MONTH. THE COLDEST
TEMPERATURE OF 32 DEGREES F OCCURRED ON THE MORNING OF THE 4TH.

ELEVEN WARMEST MAY`S IN DENVER WEATHER HISTORY SINCE 1872:

64.7 1934
63.2 1994
62.0 1886
61.7 1958
61.6 1974...1879
61.5 1939
61.3 1936
61.1 1875
61.0 1941...1874

TEN COLDEST MAY`S IN DENVER WEATHER HISTORY SINCE 1872:

48.7 1917
50.0 1995
50.1 1935
50.3 1907
51.4 1983
51.5 1892
52.0 1946
52.6 1967
52.7 1924
52.8 1943

PRECIPITATION:

PRECIPITATION FOR THE MONTH OF MAY AT DENVER INTERNATIONAL
AIRPORT WAS 3.66 INCHES, WHICH IS 1.54 INCHES ABOVE THE NORMAL OF
2.12 INCHES. THERE WERE 17 DAYS WITH MEASURABLE PRECIPITATION DURING
THE MONTH. 1.13 INCHES OF PRECIPITATION FELL ON THE 18TH, WHICH IS
THE GREATEST DAILY AMOUNT FOR THE MONTH. A TRACE OF SNOW WAS
MEASURED DURING THE MONTH WHICH IS 1.1 INCHES BELOW NORMAL.

TEN WETTEST MAY`S IN DENVER WEATHER HISTORY SINCE 1872:

8.57 INCHES 1876
7.31 INCHES 1957
6.12 INCHES 1969
5.06 INCHES 1973
4.95 INCHES 1935
4.88 INCHES 1938...1898
4.79 INCHES 2011
4.77 INCHES 1967
4.67 INCHES 1995

TEN DRIEST MAY`S IN DENVER WEATHER HISTORY SINCE 1872:

0.06 INCHES 1974
0.09 INCHES 1886
0.15 INCHES 1899
0.22 INCHES 1919
0.34 INCHES 1977...1966
0.43 INCHES 1925
0.49 INCHES 1972
0.52 INCHES 1911
0.53 INCHES 1900

TEN SNOWIEST MAY`S IN DENVER WEATHER HISTORY SINCE 1872:

15.5 INCHES 1898
13.7 INCHES 1950
13.5 INCHES 1978
13.2 INCHES 1912
12.0 INCHES 1917
10.0 INCHES 1908
 9.0 INCHES 1907
 8.9 INCHES 1893
 8.8 INCHES 1957
 8.3 INCHES 1944

THERE WERE 13 DAYS IN WHICH THUNDER WAS OBSERVED AT DENVER
INTERNATIONAL AIRPORT AND 0 DAYS WITH DENSE FOG WITH A
VISIBILITY AT OR BELOW 1/4 MILE DURING THE MONTH. THE PEAK
WIND GUST OF 52 MPH FROM THE SOUTHWEST OCCURRED ON THE 7TH.

$$


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