Perhaps the Last Arctic Blast

Perhaps the Last Arctic Blast:

After moderating a bit since Valentine’s Day (last Friday), temperatures plummeted over February 18-20 this week with an Arctic high pressure system slowly moving over the state. Many portions of the state saw temperatures drop\ to the teens and twenties below zero, while areas in St Louis and Lake Counties reported low temperatures from -32°F to -40°F. For three days in a row this week Minnesota reported the nation’s lowest temperature. Even with sunny skies the daytime high temperatures remained quite cold. For February 19th Detroit Lakes reported a maximum afternoon temperature of only 2°F, and Warren (Marshall County) in the Red River Valley only reached a high of -3°F.

The good news is that recent outlook guidance from the NOAA Climate Prediction Center indicates that for the balance of the month temperatures will trend upward either near normal or above normal. This means that at least for the southern half of the state we may have seen the last subzero temperature reading until next winter. Temperatures are expected to remain near normal as the month of March begins as well. For the most part the outlook models also call for an extended drier than normal period, with no major snowstorms on the horizon.

USGS Reports High Stream Flow Volumes:

The USGS reports that 2019 brought record setting high volume stream flow for 46 percent of the gaged stations in southern Minnesota watersheds. The high-volume flow records were not set with peaks of record stream flow, but by persistence of high volume flow. Even now as winter dissipates high volume flow remains in many streams and rivers.

29 percent of the gaged stations on the Mississippi, Minnesota, and St Croix Rivers report their greatest winter flow rates

More than half of the gaged stations report winter volume flow in the 95th percentile. Hydrologists hope that these high discharge volumes shrink significantly before a prolonged thaw period settles in, so that the risk of flooding along the major rivers will be reduced.

Weekly Weather Potpourri:

Pete Boulay from the Minnesota State Climatology Office has produced the first comprehensive map of the precipitation values and their historical ranking for 2019, wettest year in state history. Roughly 40 percent of the state landscape received over 40 inches of precipitation in 2019, and about 80 percent of the landscape reported annual precipitation that was greater than the 90th percentile historically. Areas of southern Minnesota received annual precipitation in 2019 that was 16 to 18 inches greater than normal.

In a rare event on Monday February 17th, US National Weather Service radar captured birds migrating from South America over Florida. Atmospheric conditions caused the systems to detect the birds, which took hours to fly over the Key West station. You can read more from the Tampa Bay Time.

On Wednesday, February 19th “pure whiteout conditions” along a highway near Montreal, Canada cause a 200-vehicle pile up to occur. At least two people were killed. Blowing snow was blamed for the blinding conditions. The incident was written up by the Weather Underground.

This week the AGU-EOS bulletin features an interesting article about how scientists have discovered that in the mid to high latitudes climate change has diminished the persistence of river ice on major rivers. Using 400,000 satellite images from 1984 to 2018, the researchers found that on average, ice cover declined by almost a week over those decades. This has important implications for the health of these river ecosystems.

MPR listener question:

We were wondering about the state record climate readings for Leap Day, February 29th. Since they are measured only every 4 years are they somewhat odd relative to the other calendar days?

Answer:

Yes, and No. We have for our daily statewide climate records a sampling of measured data that go back 130 to 150 years. But for February 29th we have a much smaller pool with about 33 years measured. Here is what the statewide daily climate record values show for Leap Day in Minnesota:

Precipitation 2.23 inches at Faribault in 2012…..in range with all other dates just before and just after that date.

Maximum temperature 65°F at Forest Lake in 2000….this number is lower than the 7 days before Leap Day, and vastly lower than all days in March.

Minimum temperature -38°F at Roseau in 1916……this number is not as cold as the first 6 days of March and with the exception of February 27th (-40°F at Warroad in 1913) is no where near all the all minimum temperature records for February dates.

Snowfall inches of snowfall at Ortonville (Big Stone County) in 2012……this number is tied for the lowest daily snowfall record for any date in February (also 12.0 inches for February 3 at Caledonia in 1983.

So overall, the daily precipitation record for Leap Day appears to represent the overall climate record pretty well. But the other records are not especially representative since they come from a much shorter sampling period.

Twin Cities Almanac for February 21st:

The average MSP high temperature for this date is 31 degrees F (plus or minus 11 degrees F standard deviation), while the average low is 15 degrees F (plus or minus 13 degrees F standard deviation).

MSP Local Records for February 21st:

MSP weather records for this date include: highest daily maximum temperature of 62 degrees F in 2017: lowest daily maximum temperature of -1 degrees F in 1963; lowest daily minimum temperature is -21 degrees F in 1873; highest daily minimum temperature of 44 degrees F in 1930; record precipitation of 0.82 inches in 1882; and record snowfall of 5.5 inches in 1962.

Average dew point for February 21st 13 degrees F, with a maximum of 52 degrees F in 1930 and a minimum of -33 degrees F in 1963.

All-time state records for February 21st:

The state record high temperature for this date is 64 degrees F at Whitewater State Park (Winona County) in 1943. The state record low temperature for this date is -51 degrees F at Baudette (Lake of the Woods County) in 1966. State record precipitation for this date is 2.02 inches at Two Harbors (Lake County) in 2014; and record snowfall of 19.2 inches at Madison (Lac Qui Parle County) in 2011.

Past Weather Features:

An Arctic Cold Wave gripped the state over February 20-22, 1939. The landscape was already blanketed with a heavy coating of snow, so temperatures fell to record cold levels. Much of central and northern Minnesota saw morning low temperatures of -30°F or colder. Over a dozen climate stations reported readings between -40°F and -50°F, and the high temperature never rose above 0 degrees F at Fosston for over 3 days.

In a relatively snow-free landscape temperatures across southern Minnesota soared into the 60s on February 21, 1981. Bright sun and thawed soils provoked some farmers to go out and till, while some even planted small grains.

A slow-moving low-pressure system crossed the state and brought heavy snowfall to many areas over February 20-21, 2011. So climate stations reported record amounts including over 16 inches at Granite Falls, Montevideo, Milan, Dawson, and Springfield. Madison and Ortonville reported over 20 inches.

Outlook:

Relatively sunny and warm over the weekend with some areas seeing 40 degrees F temperatures. Increasing cloudiness on Monday with a chance for light snow. Temperatures will cool back closer to normal for the Tuesday through Friday period with chances for light snow or snow flurries.