April brought cold, cloudy, slow start to spring
Spring continued to be elusive in April with a cold, cloudy weather pattern holding a firm grip on much of the nation from the Rockies to the East Coast.
Precipitation was very close to normal and snowfall was a bit less than we would expect to see during a normal April.
After a long and snowy winter across much of the central and eastern U.S., an extensive snow cover lingered well into April helping to refrigerate the air above the snow. A winter-like weather pattern helped bring more snow to the Midwest which kept the snow pack intact and sent cold air our way.
While we only saw small amounts of snow through southern New Hampshire last month we felt the chill of the cooled air arriving from the middle of the nation until the final week of April. The cool, cloudy weather certainly slowed the development of the spring season.
A common pattern that brings cool, damp weather during April is when the jet stream lifts northward and leaves behind stalled pools of cold air. These systems sometimes spark week long episodes of rain, drizzle and east winds but this is not what happened this year. This year a winter-like weather pattern just bullied its’ way deep into spring.
Temperatures were March-like through a good part of April and helped bring snow instead of April showers several times through the early and mid-part of the month.
April 2018 would be the 20th coldest out of 125 years of temperature record for Nashua after last April which was the 6th warmest.
Nashua’s average temperature of 42.3 degrees was 3.4 degrees below normal and the coldest April since 2003. Only one record was set and that was a record low high temperature of 33 degrees on the 16th breaking the mark of 36 from 1904. Temperatures during the daylight hours of the 15th were below freezing all day, quite unusual for so late in the season.
The cold temperatures kept the greening of the grass slow and it was not until somewhat milder than normal readings arrived late in the month that lawns began to take on a nice green color. Maple and poplar trees were also delayed in blooming by a couple of weeks.
The monthly high of 72 was chilly for the fourth month of the year. This was the lowest April high since 1999. The lowest all-time is 67 from April 1893. Cloudiness was a contributing factor to the chilly weather as well.
While the final sunshine statistics are not yet available from the Blue Hill Observatory it appears that April will be about 5% below the long term average. April is normally a cloudy month to begin with and when we see above normal cloudiness it only increases the dreariness.
The sun’s strength during April matches the period from mid-August to mid-September but cloudiness this time of year frequently prevents us from seeing it.
Although it seemed like a wet month, April’s precipitation was almost exactly normal. The total measured at Pennichuck Water Works was 4.40 inches, just 0.04 inches above normal. For the year we’ve received 15.36 inches, only 0.08 inches below normal.
The frequent episodes of rain and wintry mix during April kept down the wildfire threat that sometimes sparks up this time of year.
The active jet stream kept a series of low pressure areas moving across the nation. For our neighborhoods we saw mostly light to moderate amounts of precipitation with the passage of these systems. Some sleet and ice on the 15th was followed by one notable storm system on the 16th.
This storm gobbled up some Gulf of Mexico and Atlantic moisture to bring the area 1.5 to 2.5 inches of rain and even some short-term urban and street flooding.
The final week of the month was damp as several fast moving systems brought modest amounts of rain and showers.
We added just a little more to our snowy season total during April. The total measured at Pennichuck Water Works of 0.5 inches was 0.3 inches below normal. Snow was observed on several days during the early and middle of the month, mostly in the air and not sticking to the ground.
A couple of days with snow are not unusual during April but we did see more days with some snow in the air than normal.
The cold temperatures with the snow just added to the effect of winter lingering on.
The final statistics for the 2017-18 snow season show a tally of 81.9 inches for Nashua, a surplus of 27.0 inches.
This past snow season was the 20th snowiest out of 108 years of record.
During the past quarter century snow seasons have produced a notable increase in average snowfall for the Nashua area. Beginning with the 1992-93 season the average snowfall has been 62.4 inches for Nashua. This is 7.5 inches above the long-term normal.
Fifteen of the past 26 winters have featured above normal snowfall. The current period matches the period from 1955 to 1978 when snow was copious across the region. The previous snowy period was followed by many lack-luster snow years from 1979 to the 1991-92 season.
Anyone native to the region is well aware that spring can be short-lived with winter turning into summer quite fast and as we start May we have seen just that take place.
The weather during May can still wear many hats. It’s all about wind direction this time of year. A west wind we can bring the sizzle of summer but the east wind can bring chilly temperatures, clouds and sometimes drizzle or light rain.
For the gardener, hardy plantings are good anytime, but other vegetables and flowers that can be damaged by frost should not be planted until Memorial Day. Frosts are not unusual through mid May and can occur infrequently until late month.
The average date for the last 32 degree reading locally is May 10. Keep in mind that this date is an average with last frost dates over the years varying from as early as mid-April to as late as early June.
April Facts and Feats dating back to 1884
April 2018 Average T
42.3 degrees, 3.4 degrees below normal.
All-time April High
93, Apr. 20, 1941, and Apr. 18, 2002.
April 2018 High
72, Apr. 29.
All-time April Low
8, Apr. 1, 1969.
April 2018 Low
22, Apr. 6, 7.
April 2018 Precipitation
4.40 inches, 0.04 inches above normal.
2018 Annual Precipitation to date
15.36 inches, 0.08 inches below normal.
2007, 10.72 inches.
1941, 0.48 inches.
April 2018 Snowfall
0.5 inches, 0.3 inches below normal
1982, 16.8 inches
81.9 inches, 27.0 inches above normal.