Dry With Frost Threats for This Week

Dry With Frost Threats for this Week:

A remarkable turn in the weather over the past week, or at least since May 2nd has taken place with respect to atmospheric moisture content. Not only has there been little to no rainfall since May 2nd, but relative humidity and dew point readings have been near record low values across the state. In the Twin Cities Metro Area afternoon relative humidity levels have ranged only from 14 to 24 percent over the past 5 days, while dew points have been in the teens and twenties. Combined with winds that have ranged from 20 to 30 mph, the landscape has dried out rapidly, especially the top 6 inches of the soil. The National Weather Service has issued Red Flag Warnings for fire danger on some of these days. On Thursday, May 7th MSP set a new low dew point record with a reading of just 5°F and associated relative humidity of just 14 percent.

Minnesota farmers have been rapidly planting, mostly corn and soybeans, and some crops have emerged. Vegetable growers have also been transplanting crops, and apple orchards are budding or even blooming in many areas. Unfortunately, the drier, cooler air from the northern latitudes is also bringing a repeating threat of frost, at least through next Tuesday morning. Some field crops, produce crops, and orchards may show signs of frost damage on Friday, Saturday, Monday, or Tuesday mornings. Friday morning (May 8th) brought some scattered frosts in southern Minnesota, and more widespread frosts in central and northern counties. Beyond May 12th the weather will bring more clouds and moderate temperatures to the state. But getting through this very dry, and unseasonably cool spell of weather unscathed may be too optimistic.

Despite following the wettest year in Minnesota history (2019) gardeners may need to water early this spring to keep the top layers of soil moist enough for emerge and growth of plants.  Deeper layers of soils still have plenty of moisture in storage from last year.

Weekly Weather Potpourri:

The BBC reports this week that portions of Ethiopia, Kenya, and Somalia are suffering from huge infestations of locusts that are destroying many food crops. They are trying to control the pests but lacking in some critical pesticides. Their food supply chains are already being affected by the pandemic, so it is a very challenging situation.

Further Ben Rich of the BBC Weather Center reported this week on features of the world’s weather and climate that are being affected by the global pandemic. It is an interesting review on the reduction in greenhouse gas emissions, improved air quality, and impacts on food production systems.


The Weather Underground reported this week that parts of Eastern Asia broke many high temperature records for April as a huge early year Heat Wave emerged. Incredible heat for late April extended across parts of Central and East Asia. At least three all-time national heat records for April were set:

—Kyrgyzstan: 35.1°C (95.2°F) at Tokmak on April 27

—China: 43.5°C (110.3°F) at Ayding Lake on April 29 (Ayding Lake is one of the lowest spots on Earth, at 502 feet or 154 meters below sea level)

—Mongolia: 36°C (rounded) (96.8°F) at Ekhiyn-Gol (Oasis) on April 30

Even in these extreme desert climates, such temperatures are more on par with normal readings in July. Many other Chinese towns and cities set all-time April heat records.

Early May heat has been reported from the desert southwest of the USA as well with readings of 106 degrees F from Tucson, Phoenix, Yuma, and Imperial (CA). The heat is expected to last there throughout the weekend.

MPR listener question:

With the threat of frost widespread over the coming weekend, we were wondering what are the latest spring dates reported for frosts in the Metro Area of the Twin Cities?

Answer:

In recent years, late spring frosts are somewhat rare, though they still have some miniscule probability through early June. Here are some of the latest historical dates:

MSP May 24, 1925
Stillwater May 23, 1974
Forest Lake May 26, 1961
Maple Plain May 29, 1947
Chaska June 4, 1945
Farmington June 7, 1897
University of Minnesota St Paul Campus May 23, 2013

After we get past the third week of May, the historical probability for frost really tails off, typically less than 10 percent.

Twin Cities Almanac for May 8th:

The average MSP high temperature for this date is 67 degrees F (plus or minus 11 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 8th:

MSP records for this date include: highest daily maximum temperature of 90 degrees F in 1874; lowest daily maximum temperature of 41 degrees F in 1924; lowest daily minimum temperature of 28 degrees F in 1960; highest daily minimum temperature of 67 degrees F in 1896; record precipitation of 1.73 inches in 1872. Record snowfall is 0.5 inches also in 1923.

Average dew point for May 8th is 38°F; the maximum dew point on this date is 67°F in 1965; and the minimum dew point on this date is 6°F in 1947.

All-time state records for May 8th:

The state record high temperature for this date is 102 degrees F at Beardsley (Big Stone County) in 1934. The state record low temperature for this date is 10 degrees F at Pine River (Cass County) in 1907. The state record precipitation for this date is 4.85 inches at Santiago (Sherburne County) in 2014. Record snowfall for this date is 12.0 inches at Windom (Cottonwood County) in 1938.

Past Weather Features:

Over May 8-9, 1924 a late spring snow storm brought 1-5 inches of snow to many parts of eastern Minnesota. It was a surprise to the National Weather Service, and to farmers who were out planting their crops. Fortunately the snow was short-lived.

By far the hottest May 8th in history was in 1934. Most places in Minnesota reported afternoon high temperatures from the mid 80s ot mid 90s F. Portions of Big Stone and Chippewa Counties in the west broke the century mark. On the same day, Two Harbors reported a high temperature of only 48°F.

55-years ago this week the worst tornado outbreak in history for the Twin Cities Metro Area occurred. On May 6, 1965 the Twin Cities recorded a record high dew point with a reading of 66 degrees F, indicating a huge amount of latent energy in the atmosphere. Six tornadoes roared across the Metro Area between 6pm and 9pm causing widespread damage, injuring over 500 people, and killing 14. Some of the storms were EF-4 (winds over 207 mph), and 25 planes were destroyed at the Anoka Airport. The National Weather Service was credited with doing a good job in forecasting these storms and they were assisted in reporting on them by Charlie Boone and Dick Chapman of WCCO radio.

Outlook:

Much cooler than normal weather will dominate Minnesota over the Saturday through Tuesday period. There will be multiple chances for early morning frosts, and even a chance for light rain and snow flurries on Sunday morning. A gradual warm-up will begin by next Wednesday and there will be a chance for rain by Thursday, but temperatures will remain a bit below normal.