To: Morning Edition From: Mark Seeley Re: Topics for MPR's Morning Edition, Friday, April 30, 2004 Topic: Arbor Day Happy National Arbor Day today. Minnesota also celebrates Arbor Month during May. We certainly missed the refreshing shade of deciduous trees on Wednesday of this week, when high temperature records were broken all around the state. Many of these trees were not yet leafed out, so they could not provide the welcome shade on our patios, decks, and gardens. Arbor Day is a day for planting trees, and in many places a ceremonial act of spring that dates back to 1872 in Nebraska. In Minnesota today and during the month of May (Arbor Month) there will be a good deal of tree planting and educational activities about the value of trees. It is worth noting the many advantages trees bring to the local environment. In recent years with the research on global climate change we have learned that trees take up large quantities of carbon dioxide on a global scale. When used in the home landscape they can also provide a buffer from nearby sources of dusts, odours, aerosols and noises. They are planted in the rural landscape to provide wind protection, to reduce soil erosion potential, to capture blowing and drifting snow, preventing it from clogging roadways, and to provide wildlife habitat. In the residential landscape trees provide selective shading in the summer, somewhat reducing air conditioning needs,.particularly when placed on south or west facing exposures to protect roofs, windows and air conditioning units from direct sunlight. In winter, trees (especially evergreens) can provide protection from northerly and westerly winds which may tend to carry off heat from buildings more rapidly. They also tend to alter the local radiation balance, as they have lower albedo (reflectivity) and help reduce long wave radiation loss to the atmosphere at night, keeping minimum temperatures higher. Topic: Hottest April 28th in Minnesota History..... One could say it was the hottest April 28th in state history this past Wednesday, as many communities reported new record high temperatures, breaking records from 1910, 1934, and 1952. Even the all-time state record high for the date of 94 degrees F at Argyle in 1952 was broken when Benson, MN reported 95 degrees F at 4 pm that afternoon. The following communities reported new record high temperatures on Wednesday.... MSP airport 91 F St Cloud airport 92 F Fargo airport 91 F Detroit Lakes 90 F Fergus Falls 93 F Madison 91 F Glenwood 93 F Redwood Falls 93 F Wheaton 91 F Orr 90 F Willmar 93 F Litchfield 91 F Hutchinson 93 F New Ulm 91 F Faribault 90 F Waseca 91 F Albert Lea 90 F Alexandria 91 F Olivia 93 F Morris 90 F St James 90 F Red Wing 88 F Brainerd 87 F Little Falls 88 F Austin 88 F Preston 90 F Cambridge 93 F Lamberton 93 F Chaska 92 F Rochester and Fairmont tied record highs with 87 degrees F and 90 degrees F, respectively. La Crosse too tied a record high with 89 degrees F. In addition, new record low humidity values (greatly inflating the fire danger) were reported on Wednesday afternoon, many lower than what Tucson, Arizona reported for the same date (13 percent)!!!! New record low relative humidity values for April 28th included... Detroit Lakes 12% Fergus Falls 6% Glenwood 9% Litchfield 10% Waseca 12% New Ulm 5% Redwood Falls 9% Olivia 5% Pipestone 2% St James 9% Fosston 9% Cambridge 12% Madison 8% Willmar 12% Windom 10% Marshall 10% Montevideo 11% Ortonville 10% Some of these are about as low as we ever see in Minnesota. Locally, the Twin Cities relative humidity dropped as low as 20 percent, but did not reach the 11 percent value recorded on April 28, 1934. Topic: Climate Summary for April The average temperature for April was warmer than normal most places around the state, except in the far north-central and northeastern sections where it was slightly cooler than normal. Extremes ranged from 95 degrees F at Benson on the 28th to just 7 degrees F at Embarrass on the 2nd. Though there were some welcome rains during the month, total precipitation was generally less than normal, except for portions of east-central and northeastern Minnesota where some communities saw 2.5 to 3 inches fall. Snowfall was generally absent during the month. Only Babbitt, Tower, and Isabella in northeastern Minnesota reported more than 1 inch of snowfall. The month was generally cloudy and windy as well. MPR listener question: Was that an exceptionally strong cold front on Wednesday night? I see that Olivia's temperature dropped from 93 degrees F to 36 degrees F over a 12 hour period (5 pm Wed to 5 am Thu), a 57 degrees F plummet. Answer: Indeed, most meteorlogists would agree that a temperature drop of 40 degrees F or greater indicates a very strong cold front passage. Such was the case Wednesday and Thursday this week. This time of year the temperatures of different air masses that cross Minnesota can be substantially different and bring huge temperature changes. For example April 2, 1982 brought a near record high temperature of 78 degrees F to Lamberton, MN, but a very strong cold front swept in later in the day and took the low down to just 7 degrees F, a drop of 71 degrees F! Local Almanac: Twin Cities Almanac for April 30th: The average MSP high temperature for this date is 62 degrees F (plus or minus 13 degrees standard deviation), while the average low is 43 degrees F (plus or minus 9 degrees standard deviation). MSP Local Records for April 30th: MSP weather records for this date include: highest daily maximum temperature of 91 degrees F in 1934 and 1952; lowest daily maximum temperature of 31 degrees F in 1909; lowest daily minimum temperature of 24 degrees F in 1903; highest daily minimum temperature of 66 degrees F in 1934; record precipitation of 1.53 inches in 1954; and record snowfall of 3.1 inches in 1984. There has only been one measurable snowfalls on this date since 1948. Maximum snow depth on this date was 4 inches in 1984. Average dew point for April 30th is 37 degrees F, with a maximum of 63 degrees F in 1942 and a minimum of 8 degrees F in 1918. All-time state records for April 30th: Scanning the state climatic data base: the all-time high for this date is 96 degrees F at Maple Plain (Hennepin County) in 1934 and at Winona in 1952; the all-time low is 8 degrees F at Cook (St Louis County) in 1966. Words of the week: Ironwood, Kentucky coffeetree, Shagbark hickory, Big-Toothed Aspen These are undoubtedly familiar names to arborists who might be planting trees today. They are all deciduous trees adapted to Minnesota's climate, though some are recommended only for certain parts of the state. From the DNR web site I found over 40 recommended deciduous tree species for Minnesota and ten coniferous trees suitable for planting. So go out, pick a favorite from your local nursery, and give it a try. Outlook: Cooler than normal for this time of year, with chances for showers and perhaps snow flurries over the weekend and into early Monday. A warming trend will start on Tuesday and carry temperatures back into the 60s and 70s F. Another chance for showers by late Tuesday and into Wednesday.