A Statistical Preview to Denver's April Weather

        ...A STATISTICAL PREVIEW OF DENVER’S APRIL WEATHER...
 
APRIL IN DENVER IS CONSIDERED A TRANSITION MONTH SIMILAR TO MARCH, HOWEVER IT’S WARMER WITH A BIAS TOWARD RAINFALL AND SEVERE WEATHER. 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'S NORMALS.
 
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. MARCH'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 MONTLY 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 2013...
 
ATER A MARCH 2013 WHICH EXPERIENCED ABOVE NORMAL PRECIPITATION, WELL ABOVE NORMAL SNOWFALL AND BELOW NORMAL TEMPRATURES, THE SHORT TO MEDIUM RANGE MODEL INDICATE A NORMAL PROGRESSION OF THE RIDGE TROUGH PATTERN THROUGH THE FIRST 10 DAYS OF APRIL. LOOKING BEYOND THE FIRST 10 DAYS, THE CLIMATE PREDICTION CENTER'S LONG RANGE MONTHLY FORECAST INDICATES A BIAS BACK TOWARD PRECIPITATION BEING SLIGHTLY BELOW NORMAL WITH NEAR NORMAL TEMPERATURES EXPECTED FOR APRIL 2013.
 
                       ...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
 
FREDIN


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