Heat Shifts Toward/Into Iowa (With Dryness) Medium-range

The June 2021 Global Climate Records/Climate Discussion
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07/16/2021, 7:58 am EDT
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Dryness propels intensifying drought and historic heat across the Canadian Prairies and North-central U.S. in the medium-range forecast. The dryness and anomalous heat expands into the west and northwest U.S. Corn Belt.

Early U.S. AG Report Highlight: West/northwest U.S. Corn Belt enjoys excessive rainfall today followed by long duration dry spell with increasing heat risk.

Later today: Month 1-3/season 1-3 outlooks for South America/Australia.

Fig. 1: NOAA/WPC excessive rainfall/flash flood risk areas for today.

Discussion: NOAA/WPC excessive rainfall/flash flood risk forecast is centered on the west/northwest U.S. Corn Belt today (Fig. 1). The area needs the rainfall as dry soil moisture trend has strengthened in this zone during the first half of meteorological summer. Rainfall amounts for IA/MN/WI peak in the 2-3 in. range according to ECMWF for this event. More rainfall (4 in.) is forecast for northeast Iowa by GFS.

The west/northwest U.S. Corn Belt goes dry for the remainder of July after today’s heavy rainfall event. The important question becomes whether the shift of the excessive heat in the West U.S. to the Canadian Prairies/North-central U.S. in the 6-10-day period (Fig. 2) can expand southeastward into the west/northwest U.S. Corn Belt. The mega-cluster 6-10-day forecast of percent normal rainfall is confidently very dry for much of the U.S. Corn Belt (Fig. 3). The catalyst to this drier change is emergence of the Southwest U.S. Monsoon. In the 11-15-day period the anomalous heat in central North America is expanding toward the west/northwest U.S. Corn Belt (Fig. 4). The precipitation forecast is likely drier than indicated due to the dry Midwest U.S. correlation to wet Interior West monsoon weather (Fig. 5). The 15-day maximum temperature forecast for Des Moines, IA indicates emerging heat risk beginning early next week (Fig. 6).

Fig. 2-3: The mega-cluster ensemble identifies the most likely temperature anomaly and percent of normal rainfall forecast for North America for days 6-10.

Fig. 4-5: The mega-cluster ensemble identifies the most likely temperature anomaly and percent of normal rainfall forecast for North America for days 11-15.

Fig. 6: The 15-day maximum temperature forecast for Des Moines, IA by Climate Impact Company is indicated.