Heavy rains and snow this week

Heavy rains and snow this week:

Wednesday, May 8th brought from 1 to 2 inches of rain to many parts of the state in a storm that last for many hours. Late in the day the precipitation turned to snow in many northern communities dropping from 2 to 10 inches in portions of northeastern Minnesota. This was a distinctly untimely storm as many spring road projects had begun with excavations and Minnesota farmers were busy trying to plant crops.

Several climate stations reported new daily record amounts of rainfall, including:
2.10” at Stillwater
1.92” at Spring Valley
1.87” at Rosemount
1.84” at Faribault
1.65” at Zumbrota and Red Wing
1.60” at Marshall

The evening snow storm turned out to be record-setting for many communities as well. Those reporting new record daily snowfall amounts included:
8.3” at Duluth
6.6” at Wright (Carlton County)
6.0” at Cloquet (Carlton County), Isabella (Lake County), and Isle (Aitkin County)
5.0” at Wolf Ridge (Lake County)
2.0” at Babbitt and Cotton (St Louis County)

The snow was relatively short-lived as temperatures climbed into the mid 40s to low 50s F on May 9th.

Big Temperature Swings in May Explained:

For many locations in Minnesota, May is the month with the largest average daily temperature range, typically 20 to 30 degrees F (difference between the daily maximum and minimum). What causes this? Several factors come to mind.

Crops are rarely fully leafed out, so much of the landscape is still composed of bare soil, which more readily stores heat during the day and surrenders it at night. Perennial vegetation is not yet fully utilizing soil moisture since it is still relatively early in the growing season. Therefore the release of water vapor into the atmosphere by actively growing vegetation is somewhat limited. Sun elevation angle is increasing, as is day length, providing the sun with more time to heat the Earth's surface. The change in

air masses that accompanies a frontal passage can still be rather dramatic in May, modifying the air temperature significantly in just a few hours.

Though these are all good reasons to expect a relatively large range in daily temperatures, I think one of the primary factors is water vapor. The difference between average air temperature and average dew point (the temperature at which the air is saturated) is large during May and the relatively drier air can heat and cool more readily as a result. Dew points have been as low as 0°F in May. Western locations in the state show many days with daily temperature ranges in May of 40 to 50 degrees F. An example is Milan, in Chippewa County. On May 16, 1934 a chilly morning low of 34 degrees F was recorded, followed hours later by an afternoon high of 100 degrees F.....a rise of 66 degrees F. The dew point was only in the mid 30s F that day. More recently at Granite Falls on May 19, 2009 the temperature climbed from 47°F to 99°F under bright sunny skies and dew points in the 30s F.

Weekly Weather Potpourri:

Tropical Cyclone Lili formed northwest of Darwin, Australia this week, but it is expected to remain relatively week and remain out to sea meandering towards East Timor through the weekend.

Earlier in the week Maldura in Victoria, Australia was swept over by a blinding dust storm with winds over 50 mph. Dust covered everything and traffic was stopped in many areas.

A new study from researchers in the United Kingdom finds that abrupt climate change some 8,000 years ago led to a dramatic decline in early South American populations. You can read more about this study from Nature International Reports.

This week the AGU-EOS newsletter reports that the U.S. House of Representatives approved legislation that directs President Donald Trump to honor the nation’s commitments under the 2015 Paris climate agreement, despite Trump’s earlier pledge to withdraw the United States from the accord. This legislation was passed on May 2nd. The Climate Action Now, formally known as House Resolution 9, requires the administration to develop and update the nation’s plan to meet its “nationally determined contribution” (NDC) under the Paris Agreement.

MPR listener question:

Last week you said that May snowfalls in northern Minnesota were fairly common. Which northern Minnesota locations have had June snowfalls?

Answer:

The following climate stations have reported June snowfalls: International Falls, Mizpah, Virginia, Grand Rapids, Grand Portage, Tower, Babbitt, and Hibbing. All of these were in the first 5 days of the month.

Twin Cities Almanac for May 10th:

The average MSP high temperature for this date is 68 degrees F (plus or minus 10 degrees F standard deviation), while the average low is 47 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for May 10th:

MSP weather records for this date include: highest daily maximum temperature of 90 degrees F in 1987: lowest daily maximum temperature of 43 degrees F in 1902; lowest daily minimum temperature is 28 degrees F in 1907; highest daily minimum temperature of 68 degrees F in 1922; record precipitation of 1.40 inches in 1986; and there was a trace of snowfall on this date in 1966.

Average dew point for May 10th is 40 degrees F, with a maximum of 70 degrees F in 2011 and a minimum of 14 degrees F in 1981.

All-time state records for May 10th:

The state record high temperature for this date is 97 degrees F Beardsley (Big Stone County) in 1928. The state record low temperature for this date is 11 degrees F at Pine River (Cass County) in 1905. State record precipitation for this date is 4.27 inches at Wheaton (Traverse County) in 1920; and record snowfall is 6.0 inches at Pigeon River Bridge (Cook County) in 1927.

Past Weather Features:

On May 10, 1902 a fast moving late season snow storm swept across northern Minnesota depositing 4 to 5 inches of snowfall in many areas. The swath of snow extended from Fergus Falls to Warroad, and across the northeast to Grand Portage.

May 10, 1987 was arguably the warmest in state history with over 50 climate stations reporting afternoon high temperatures in the 90s F.

Strong thunderstorms brought heavy rains and even some hail to portions of southern and central Minnesota over May 9-10, 2004. Strong winds were measured as well with gusts over 50 mph.
Many citizens captured photos of the tall anvil-shaped clouds in the early evening as they passed to the east.

Outlook:

Cloudiness will increase later on Saturday and continue into early Sunday with a chance for rain. Monday will be dry with climbing temperatures reaching normal values for this time of year. Later on Tuesday there will be another chance for showers and thunderstorms, then drier for and warmer (above normal temperatures for Wednesday- Friday.