Midwest Drier Again; Delta Much Wetter: Previously the remnants of Harvey were expected to stay confined to TX, LA and parts of MS through the week ahead, but the major forecasting models have expanded heavy rainfall coverage to include a bulk of the Delta region through Fri/Sat. The EU model’s latest 5-day precip forecast is attached, and notice that accumulation upwards of 7-9” looks to impact W LA, AR and W TN through the period. Limited moisture is forecast elsewhere. Temps will maintain a cooler than normal bias through Sep 12th – something that needs close monitoring.
In the near term, Harvey will linger in SE TX/LA through mid-week. Thereafter, the system’s remnants will travel northward along the MS River, bring very heavy rainfall with it. Bean harvesting in LA is just 25% finished; bean harvest in AR has just started.
Again ARC mentions – and this is contributing to Harvey’s strength – that the Central US upper air pattern has not been much affected by the season’s first major hurricane. A broad NW flow will persist for another 10-12 days, and a rather deep low pressure Trough is indicated aloft Southeast Canada & the Great Lakes Sep 5-10. This will allow much cooler air to be funneled into the region, and there are hints of overnight lows in the 30s across the Canadian Prairies, ND, MN and parts of WI late in the 11-15 day period. The GFS may be overdone with this outlook, but a pattern of sub-normal temps will linger in the background. NOAA’s temp outlook is at left, and crops across the Northern US demand an extended growing season. Recall normal frost dates in ND & MN occur around Sep 15-20.