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Very dry air this week

Very dry air this week

Following a wet first ten days of the month, May turned quite dry this week, with low dewpoints and high evaporation rates (0.25 to 0.35 inches on May 14). Montevideo (Chippewa County) reported some record-setting low daily humidity readings over May 12-16. Afternoon air temperature and relative humidity are noted for each day:
May 12 70 degrees F with RH of 7%
May 13 75 degrees F with RH of 11%
May 14 88 degrees F with RH of 4%
May 15 72 degrees F with RH of 12%
May 16 73 degrees F with RH of 14%

These humidity readings at Montevideo were the equivalent of those at Tucson, Arizona this week. Many Minnesota citizens were using moisturizing creams and chapstick.

Cold morning on May 16th

After a very warm Monday this week (afternoon temperatures ranged from 86 F to 90 F in western Minnesota), Minnesota reported the coldest temperature in the 48 contiguous states on Wednesday morning (May 16) with a reading of 24 degrees F at Embarrass, the first time this month that the state has reported the coldest reading. Many observers reported overnight lows in the 20s F on May 16th including 28 degrees F at Warroad, Cook, Hibbing, Bigfork, Ely, Grand Marais, and Kabetogama, 27 degrees F at Orr,Silver Bay, and Crane Lake, and 26 degrees F at International Falls. These overnight readings represent new record lows for May 16th at Kabetogama and Orr, and ties the record low for Crane Lake.

NOAA CPC Climate Outlook

On Thursday, May 17, NOAA-Climate Prediction Center release a new climate outlook for June through August. The outlook suggests equal chances for warmer or colder than normal temperature conditions over the summer in Minnesota. It also suggests equal chances for a wetter or drier than normal summer.

Weekly Weather Potpourri

The May 16th report from the Amundsen-Scott Weather Station at the South Pole (Antarctica) was -77 degrees F with an east wind of 10-15 mph and a windchill of -114 degrees F.

The NOAA National Hurricane Center in Miami, FL was issuing advisories this week on the first Tropical Storm of the 2012 season in the Eastern Pacific. Tropical Storm Aletta was generating winds of 40 mph and sea waves of 12 feet as it moved westward well off the coast of Mexico. It is expected to dissipate over the next several days.

Scientists from the University of Utah and Harvard University have developed a new way to estimate carbon dioxide emissions based on measured pattern detection in the atmosphere. This technique may be further refined to be used as a compliance validation measurement system should an international treaty ever be invoked that forces reduction in carbon dioxide emissions over specified periods of time. You can read more about their work here.

MPR listener question

How much does a large thunderstorm cloud weigh? It must contain a lot of water.

Answer: Thomas Schlatter, a NOAA scientist and contributor to Weatherwise magazine addressed this question in a past issue. Of course the answer is highly dependent on cloud volume. But consider a cumulus cloud with a volume of one cubic mile (1 mile wide, 1 mile long, and 1 mile deep) and a water content of 1 gram/cubic meter. This would calculate to a weight of about 9 million pounds (nearly 1.1 million gallons). That's quite a load to remain suspended in the atmosphere, but of course it does, primarily because of the droplet size and the updraft winds that hold these water droplets aloft until they reach a critical mass.

Twin Cities Almanac for May 18th

The average MSP high temperature for this date is 69 degrees F (plus or minus 11 degrees F standard deviation), while the average low is 49 degrees F (plus or minus 7 degrees F standard deviation).

MSP Local Records for May 18th

MSP weather records for this date include: highest daily maximum temperature of 91 degrees F in 1911; lowest daily maximum temperature of 45 degrees F in 1890; lowest daily minimum temperature of 27 F in 1915; highest daily minimum temperature of 68 F in 1911; record precipitation of 1.57 inches in 1892; record 3.0 inches of snowfall in 1915.
Average dew point for May 18th is 46 degrees F, with a maximum of 72 degrees F in 1998 and a minimum of 19 degrees F in 2002.

All-time state records for May 18th

The state record high temperature for this date is 101 degrees F at Fairmont (Martin County) and Pipestone (Pipestone County) in 1934; the state record low temperature for this date is 16 degrees F at the Duluth Experimental Farm (St Louis County) in 1924. State record precipitation for this date is 5.01 inches at Lanesboro (Fillmore County) in 2000; and state record snowfall for this date is 3.0 inches at Minneapolis (Hennepin County) in 1915.

Past Weather Features:

May of 1892 was one of the wettest in Twin Cities history. It rained everyday from 13th to the 21st (totaling nearly 4 inches). Farmers were late in planting crops that year because it rained on 18 days during the month. Many observers reported 6-8 inches of rainfall for the month, and Northfield reported nearly 10 inches.

May 18, 1915 brought cold and snow to many places in the state. Park Rapids and Caledonia observers reported 1 inch of snowfall, while Taylors Falls reported 1.5 inches. In Minneapolis an observer recorded 3 inches of snowfall, still a record for the date.

About 8:30 pm on May 18, 1918 an F-2 tornado (winds 113-157 mph) moved 8 miles across the rural landscape of Big Stone County in western Minnesota. It damaged buildings on 30 farms, but caused no injuries.

May 17-18, 1968 brought snow to many northern Minnesota communities, in one of the latest spring snow storms on record. Duluth reported 3.6 inches, Grand Rapids 3.0 inches, and Mahnomen 2.0 inches. As far west as Milan (Chippewa County) reported 0.5 inches. Temperatures warmed into the 50s and 60s F the next day so the snow was very short-lived.

May 18, 2000 brought heavy thunderstorms and flash flooding to many southern Minnesota communities. Jackson, St Peter, Wells, Grand Meadow, Hokah, Preston, Rushford, and Rochester measured over 4 inches of rain. Huge drifts of hail stones piled up near Mankato and there was reported crop damage in many areas. Many roads were closed, one due to a mud slide in Winona County.

Most recently on May 18, 2002 a hard freeze visited many northern Minnesota communities. Many areas saw morning lows in the 20s F, while Tower reported just 18 degrees F and Embarrass was the coldest with 17 degrees F.


Generally a warm Saturday with chances for showers and thunderstorms. Cooling down on Sunday and Monday with a continued chance for showers. Drier on Tuesday. Warmer with another chance for showers by Thursday next week.
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