Public Information Statement
Issued by NWS Denver/Boulder, CO

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NOUS45 KBOU 272158
PNSBOU

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BOULDER CO
358 PM MDT THU MAR 27 2014

...A STATISTICAL PREVIEW OF DENVER`S APRIL WEATHER...

APRIL IN DENVER IS CONSIDERED A TRANSITION MONTH SIMILAR TO MARCH,
HOWEVER WARMER WITH A BIAS TOWARD RAINFALL AND SEVERE WEATHER
INSTEAD OF SNOW. LIKE MARCH, APRIL OFTEN PROVIDES A WIDE VARIATION
OF WEATHER AND TEMPERATURE RANGES. FOR OUTDOOR ENTHUSIASTS, A DEEP
SNOWPACK OFTEN REMAINS AVAILABLE AT HIGHER ELEVATIONS WHILE WARM
SPRINGLIKE TEMPERATURES IN THE 80`S CAN BE EXPERIENCED AT LOWER
ELEVATIONS.

FAST CHANGING WEATHER IS COMMON IN APRIL OVER THE DENVER METRO AREA
AND EASTERN PLAINS. WHEN CANADIAN COLD FRONTS OCCASIONALLY CLASH
WITH RELATIVELY WARM AND MOIST GULF MOISTURE, SEVERE WEATHER
TYPICALLY ENSUES. WITH SOME OF THE MORE ORGANIZED PACIFIC TROUGHS OF
LOW PRESSURE, SEVERE WEATHER OFTEN STRIKES AHEAD OF SIGNIFICANT SNOW
STORMS. THE MONTHLY NORMAL SNOWFALL TOTAL CAN BE OFTEN REACHED WITH
A SINGLE STORM SYSTEM LASTING FROM 1 TO 3 DAYS. IN ADDITION, WHETHER
THE PRECIPITATION IS RAIN OR SNOW, APRIL`S NORMAL PRECIPITATION
DOUBLES THAT OF MARCH.

DENVER`S MONTHLY MEAN TEMPERATURE FOR APRIL IS 47.4 DEGREES (1981-
2010 AVERAGES) AND IS DENVER`S 6TH COLDEST MONTH OF THE YEAR BEHIND
DECEMBER, JANUARY, FEBRUARY, NOVEMBER AND MARCH RESPECTIVELY. APRIL
STARTS THE MONTH WITH A NORMAL HIGH OF 58 DEGREES AND ENDS WITH A
NORMAL HIGH OF 66 DEGREES. FOR LOW TEMPERATURES, THE MONTH BEGINS
WITH A NORMAL OF 30 DEGREES AND FINISHES WITH A NORMAL OF 37.

THE WARMEST TEMPERATURE EVER RECORDED DURING THE MONTH OF APRIL,
SINCE RECORDS BEGAN IN 1872, WAS 90 DEGREES ON THE 30TH DAY OF 1992.
APRIL`S COLDEST TEMPERATURE EVER RECORDED IN DENVER WAS -2 DEGREES
AND OCCURRED ON THE 2ND DAY OF 1975.

APRIL: DENVER`S TOP 5 COLDEST (MEAN TEMPERATURES):

38.8 DEGREES 1920
40.5         1997
41.0         1873, 1983
41.4         1957
42.2         1945

APRIL: DENVER`S TOP 5 WARMEST (MEAN TEMPERATURES):

56.4 DEGREES 1946, 1981
55.5         1930
55.2         1943
54.8         1992
53.7         1881

FOR DENVER`S NINE MONTH SNOW PERIOD OF SEPTEMBER THROUGH MAY, APRIL
RANKS AS THE 5TH SNOWIEST MONTH AND ACCOUNTS FOR APPROXIMATELY 13
PERCENT OF THE ANNUAL SNOWFALL OF 53.8 INCHES. DENVER NORMALLY
COLLECTS 6.8 INCHES OF SNOW IN APRIL BASED ON AVERAGES FROM FORMER
STAPLETON INTL AIRPORT (1981-2010 AVERAGES). AT LOWER ELEVATIONS,
INCLUDING THE EASTERN PLAINS, FRONT RANGE AND METRO DENVER, APRIL
STORMS VARY WIDELY WITH RESPECT TO PRECIPITATION TYPE. PRECIPITATION
FROM PACIFIC STORM SYSTEMS CAN COME IN THE FORM OF RAIN DURING
DAYLIGHT HOURS WHICH THEN TRANSITIONS OVER TO SNOW IN THE EVENING
HOURS AS TEMPERATURES COOL.

MUCH LIKE MARCH, SIGNIFICANT SNOW STORMS ARE ALSO POSSIBLE IN APRIL.
DENVER`S 5TH BIGGEST SNOW STORM IN HISTORY OCCURRED IN 1885 AND
BROUGHT A QUICK 23.0 INCHES IN LESS THAN 24 HOURS. FROM A MONTHLY
TOTAL-SNOWFALL ASPECT, APRIL WEATHER PROVES TO BE VERY COLD AND
UNSETTLED AT TIMES WITH MONTHLY TOTALS LANDING VERY MUCH IN-LINE
WITH SNOWFALL AMOUNTS SEEN IN MARCH.

APRIL: DENVER`S SNOWIEST

33.8 INCHES 1933
32.0        1885
28.3        1920
28.2        1945
25.5        1957

THE END OF THE WINTER AND ONSET OF SPRING ALONG THE FRONT RANGE AND
HIGH PLAINS OCCASIONALLY EXPERIENCE EXTENDED DROUGHT-LIKE
CONDITIONS. THESE DRY PERIODS ARE OFTEN ASSOCIATED WITH LA NINA
PHASES OF THE PACIFIC OCEANIC REGION. LIKE MARCH, THE DRIEST APRILS
USUALLY END THE MONTH WITH ABOVE NORMAL MONTHLY TEMPERATURES MAINLY
DUE TO WINDY, CLOUD FREE, DOWNSLOPE WINDY DAYS COMBINED WITH WARMER
NIGHT-TIME LOW TEMPERATURES.

APRIL: DENVER`S LEAST SNOWY

 0.0 INCHES 1888, 1930, 1943, 1992
  T         1887, 1889, 1910, 1915, 1925, 1946, 1969, 2002
 0.2        1963
 0.3        1965
 0.5        1896, 2010

APRIL CAN BE CONSIDERED THE FIRST MONTH OF THE SEVERE WEATHER AND
THUNDERSTORM SEASON IN THE DENVER AREA. TROUGHS OF LOW PRESSURE
OFTEN USHER IN RELATIVELY COLD AIR ALOFT IN NORTHWEST FLOW. THIS CAN
CREATE PERIODS OF INSTABILITY IN COMBINATION WITH SURFACE AIRMASS
COLLISIONS OF COLD CANADIAN AIR AND MOIST GULF AIR. PRECIPITATION IN
THE FORM OF SLEET AND SMALL HAIL IS ALSO COMMON WITH APRIL
THUNDERSTORMS. AS WE MOVE INTO THE WARM AND CONVECTIVE MONTHS OF
SPRING AND SUMMER, MONTHLY PRECIPITATION TOTALS BECOME A MEASURE OF
INTEREST. DENVER`S SECOND WETTEST MONTH IN HISTORY OCCURRED IN
APRIL, 1900.

APRIL: DENVER`S WETTEST

8.24 INCHES 1900
5.86        1999
4.95        1905
4.94        1885
4.13        1957

APRIL: DENVER`S DRIEST

0.03 INCHES 1963
0.05        1878
0.23        2002
0.31        1880
0.32        2008

                    ...THE OUTLOOK FOR APRIL 2014...

WITH MARCH 2014 COMING IN WITH NEAR AVERAGE TEMPERATURE AND
PRECIPITATION, THE SHORT TO MEDIUM RANGE MODEL INDICATE A PERSISTENT
PATTERN OF QUICK MOVING PACIFIC STORM SYSTEMS PASSING ACROSS THE
NORTHERN AND CENTRAL ROCKIES THROUGH THE FIRST 10 DAYS OF THE MONTH.
LOOKING BEYOND THE FIRST 10 DAYS, THE CLIMATE PREDICTION CENTER`S
LONG RANGE MONTHLY FORECAST INDICATES CONDITIONS TO REMAIN NEAR
SEASONAL AVERAGES WITH NO SIGNIFICANT BIASES AS WE MOVE TOWARD MID
SPRING.

                       ...APRIL STATISTICS...

...TEMPERATURES (1981-2010 NORMALS)...

AVERAGE HIGH...........................  61.5
AVERAGE LOW............................  33.3
MONTHLY MEAN...........................  47.4
DAYS WITH HIGH 90 OR ABOVE.............   0 (<0.1)
DAYS WITH HIGH 32 OR BELOW.............   0  (0.3)
DAYS WITH LOW 32 OR BELOW..............  13 (13.0)
DAYS WITH LOWS ZERO OR BELOW...........   0 (<0.1)

...PRECIPITATION...

MONTHLY MEAN...........................   1.71 INCHES
DAYS WITH MEASURABLE PRECIPITATION.....   9  (9.1)
AVERAGE SNOWFALL........................  6.8 INCHES (5TH SNOWIEST MONTH)

...MISCELLANEOUS APRIL AVERAGES...

HEATING DEGREE DAYS....................  529
COOLING DEGREE DAYS....................    1
WIND SPEED (MPH).......................   10.0*
WIND DIRECTION.........................  SOUTH*
DAYS WITH THUNDERSTORMS................    2* (1.5)
DAYS WITH DENSE FOG....................    1* (0.8)
PERCENT OF SUNSHINE....................   67*
(NOTE: SUNSHINE DATA ARE NO LONGER COLLECTED AS OF OCTOBER 1, 2009)

* = 1971-2002 NORMALS

...APRIL EXTREMES...

RECORD HIGH............................  90 DEGREES ON 4/30/1992
RECORD LOW.............................  -2 DEGREES ON 4/2/1975
WARMEST................................  56.4 DEGREES IN 1946, 1981
MAXIMUM COOLING DEGREE DAYS............  19 IN 1989
MINIMUM COOLING DEGREE DAYS............   0 NUMEROUS YEARS
COLDEST................................  38.8 DEGREES IN 1920
MAXIMUM HEATING DEGREE DAYS............ 784 IN 1920
MINIMUM HEATING DEGREE DAYS............ 260 IN 1981
WETTEST................................   8.24 INCHES IN 1900
DRIEST.................................   0.03 INCHES IN 1963

WFO BOULDER



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