Trend suggests normal frost date

Monday's USDA-NASS Crop Progress report showed some troubling numbers that indicate the corn and soybean crops are well behind the normal pace in their development. Combined with conditions that are turning dry in many parts of the Corn Belt, that could be a recipe for disaster if a frost hits before the normal time frame.

Nerves about a potential early frost — or even one at the normal time, which could trim yield potential based on the crop's slow advancement — got soothing news from Commodity Weather Group (CWG), a crop weather forecaster that released its seasonal outlook for late summer and early fall this week. It's far from a lead-pipe-lock assurance, but it gives reason to be optimistic that an early frost may not hit this year's crops.

Just think high; the keys to CWG's outlook this week focus on the movement and ridging of air in the upper atmosphere. In years when ridging has happened farther north, frost has usually come at or after the normal time. A move southward in atmospheric ridging this time of year typically foreshadows an early or more normally timed frost.

"Thus far, ridging has focused across northern and western Canada, with troughs just off the West Coast and from the Great Lakes into southeastern Canada. The forecast for the balance of the month shows broad ridging into central parts of North America as well," according to CWG's report released Monday. "An analysis of other years that showed notable ridging in August across western Canada yielded a variety of outcomes in terms of first frost dates."

Though that ridging's moved south, this year will likely buck the trend of early frost, according to CWG, mainly because of the temperature outlook for the next two to three weeks.

"The upper air pattern in the normal or later-than-normal first frost cases showed at least weak ridging in central North America, which will likely fit better to this month’s outcome," according to CWG. "We will still need to monitor forecast models for any specific cold air threats, but this tends to support the best odds for a near-to or later-than-normal first frost in the Midwest."

Though the growing possibility of a late frost this fall is good news for farmers whose crops have a lot of developing to do, the forecast that's trying to push back that frost also doesn't bide particularly well for the health of those crops. Temperatures are expected to stay at or above seasonable levels through the remainder of August and into September, and in the absence of much rainfall, the crops could feel some pain fairly soon.

"It does look like hotter temperatures will return over the weekend into the first of next week. By Saturday, 90-degree temperatures could extend across Iowa and continue hot on Sunday and Monday with highs in the mid-90s over southern Iowa and northern Missouri. The extreme heat is forecast to move farther west back toward Kansas and Nebraska early next week, but the heat may try to advance back across much of Iowa toward the latter part of next week," says Harvey Freese of Freese-Notis Weather, Inc. "The heat is helping to speed the crops toward maturity and add growing degree days, but the lack of significant moisture will mean that moisture stress will dramatically increase."