Late Season Northern U.S. Snow Cover Deepens, Likely To Last Into May

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Headline: Wet risk and cold U.S. Crop Areas into early May. U.S. spring wheat snow cover continues. Maybe warmer mid-May.


Fig. 1-4: Latest GFS precipitation amount forecast through the next 10 days and risk of <32F 5-day forecast plus the GFS 15-day temperature anomaly outlook.

Discussion: Negative North Atlantic oscillation (-NAO) is intense into early May and supports streaks of heavy rain over parts of the Great Plains in the 10-day outlook. Heavy rain is more focused on Oklahoma than Kansas this week (Fig. 1) followed by another heavy rain streak through Iowa in the 6-10-day period (Fig. 2). Dryness is likely to follow in the 11-15-day period. The -NAO pattern forces unusually cool weather through the next 2 weeks. Risk of <32F starts the week as far south as the central Great Plains (Fig. 3). The GFS 15-day forecast is impressively chilly across all major crop areas (Fig. 4). The cold weather is allowing the snow cover across the northern U.S. spring wheat areas, which has increased in recent days, to continue (Fig. 5). The 10-day outlook indicates additional patchy snowfall is likely (Fig. 6) and temperatures are certainly cold enough to support the chill.

Fig. 5-6: Current U.S. snow depth and the GFS 10-day snowfall forecast.

Fig. 7: Current U.S. snow depth and the GFS 10-day snowfall forecast.

The latest Madden Julian oscillation (MJO) forecast projects phase_5/phase_6 (Maritime Continent/West Pacific) for mid-May (Fig. 7). In May, MJO in this position would cause a warmer pattern for the Great Plains (Fig. 8) with a thunderstorm regime (Fig. 9). Cautiously, a warmer pattern change is forecast for the middle third of May.

Fig. 8-9: Current U.S. snow depth and the GFS 10-day snowfall forecast.