|HydroClim Minnesota - April , 2000
A monthly electronic newsletter summarizing Minnesota climate conditions and the resulting impact on water resources.
Distributed on the Wednesday following the first Sunday of each month.
State Climatology Office - DNR Waters
WHAT HAS HAPPENED:
- to reiterate from earlier HydroClim newsletters ... the last quarter of 1999 (October
1 - December 31) was extraordinarily dry across most of Minnesota. Many western Minnesota
communities were at or near all-time record low precipitation totals for the period. The
lack of precipitation created deficits in surface hydrology normally benefiting from
- for much of Minnesota, the snow season is essentially over. Snowfall totals this past winter were very light, typically 50 to 75 percent of average. The deficiency in snow melt runoff revealed itself in reduced early spring recharge of lakes and wetland complexes, and in reduced stream discharge.
- precipitation totals for the month of March were near to above normal for a
relatively narrow stripe stretching west to east from Moorhead to Duluth. Elsewhere in
Minnesota, precipitation was one quarter to three quarters of an inch below normal. On
March 8, showers and thundershowers produced a band of occasionally heavy rains from
Alexandria to Duluth. In Duluth, the precipitation measurement was 1.76 inches, a new
record for the city on March 8. On March 14 and 15, six to ten inches snowfalls were
reported along a narrow streak from Moorhead to Duluth, in some cases overlapping the
areas that received the rains a week earlier. These areas are the only locations in
Minnesota where topsoil moisture could be categorized as moist.
- for the past six months, October through March, precipitation totals have fallen short of normal by approximately two and one half inches on a state-wide basis.
- March temperatures were very warm throughout Minnesota, ranging from seven to ten
degrees above normal. Minnesota and the Upper Midwest experienced uncommon warmth during
the first week of March. Temperatures soared into the 60's and 70's on March 4th through
8th, breaking many maximum temperature records. Maximum temperatures in the 70's have
occurred during the first week of March in only seven prior years in Minnesota's 110 year
modern climate record. March was the fifth consecutive month of above average
temperatures. The period November, 1999 through March, 2000 was the warmest November
through March in the modern Twin Cities climate record.
WHERE WE STAND NOW:
- the National Drought Mitigation Center continues to classify southwestern Minnesota
in their "D2" category ("Severe Drought - crop or pasture losses likely;
fire risk very high; water shortages common; water restrictions imposed"). Portions
of the rest of Minnesota remain in the "D1" category ("First Stage
Drought"). The NDMC index is a blend of science and subjectivity where intensity
categories are based on six key indicators and numerous supplementary indicators.
- the Palmer Drought Index places southwestern Minnesota in the moderate drought
category, and near normal elsewhere. The Palmer Drought Index is used for assessing
long-term meteorological conditions.
- soil moisture conditions seldom change substantially during the winter. However, the warm temperatures of February and March thawed topsoil and allowed for infiltration of melting snow and falling rain. In spite of the recharge, topsoil moisture is short in most locations due to the dry autumn weather. In southwestern Minnesota, soils are very dry throughout the rooting zone. Most other areas of Minnesota have average moisture in the middle and lower soil layers.
- current stream discharge values for many southern and central Minnesota streams rank
below the 25th percentile for this time of year. Stream flows values in southwestern
Minnesota are particularly low. Elsewhere, stream flows fall in the middle of the
distribution. However, this winter's unique climate regime must be noted when comparing
present stream flows to historical averages. In most years at this point of the season,
northern Minnesota streams have yet to reach peak discharge. This year, snow melt runoff
(limited as it was) spiked discharge values many weeks ago. Without significant
precipitation over the next few weeks, northern Minnesota stream flow levels will show a
significant drop relative to historical averages.
- delayed early-winter ice development and mild winter temperatures have led to
extraordinarily early lake ice-out dates thus far in the year 2000. Many Minnesota lakes
lost their ice three to four weeks ahead of their historical average. For some lakes, this
year's ice-out was the earliest on record.
- frost rapidly left the soil during the warm spell in late February and early March. Most soils are completely free of frost. In areas where frost remains in the ground, the top 16 or more inches of soil is thawed.
- water levels in many wetland complexes are quite low, or in many cases the wetlands are completely dry.
- because of the early loss of snow cover and mild temperatures, the wildfire season
that typically begins around April 1, arrived a month early. Wildfires continue to be a
concern. Burning restrictions are in place for many central and southwestern Minnesota
- the 30-day outlook from the Climate Prediction Center calls for near-normal
precipitation for the month of April. Normal April precipitation ranges from one and one
half inches in the northwest, to two and one half inches in the southeast. The April
temperature outlook is for above-normal conditions. Normal high temperatures climb from
the mid-40's in early April to around 60 by the end of the month. Normal lows climb from
the mid to upper 20's early in the month to near 40 by month's end. The 90-day outlook for
April through June tilts towards below-normal precipitation and above-normal temperatures.
- (REPEATED FROM LAST MONTH) foresters are concerned about the potential for a major burn in the BWCA. Many trees blown down by the July, 1999 superstorm rest on their larger branches, keeping most of the heavier fuel off the ground. This architecture, plus a lack of shade, creates an excellent drying condition. A modest dry spell in future growing seasons will lead to high forest fire danger in that area.
FROM THE AUTHOR:
- Minnesota enters the growing season on the heels of a dry autumn and a snow-scarce winter. Many of the state's hydrologic systems are showing the signs of the precipitation imbalance. This imbalance leaves Minnesota's water resources very dependent on adequate spring rains. Precipitation patterns over the next four weeks will most likely set the tone for the coming growing season. Should Minnesota not receive near to above normal April precipitation, the situation could deteriorate quickly. It is PREMATURE to declare an imminent drought. However, public and private entities should take the proactive step of reacquainting themselves with their drought contingency plans. Drought information resources can be found on the State Climatology Office Web site at http://climate.umn.edu/doc/drought.htm .
NOTES FROM THE FIELD:
UPCOMING DATES OF NOTE:
- April 13, Climate Prediction Center releases 30/90 day outlooks
WEB SITES FEATURED IN THIS EDITION:
http://climate.umn.edu - Minnesota Climatology
Dana Dostert, DNR Waters Hydrologist - St. Paul
Contributions of information and suggestions are welcome!