General Observations
This past week could be characterized as a bookend event where storm activity was confined to the first and last day of period, with dry conditions in between. NERain observations from October 12 indicate that precipitation was reported across east central and southeast Nebraska during the afternoon of October 11. Since these locations are 24-hour daily observers, precipitation totals were incorporated into the daily observations taken the morning of October 12.
This precipitation event provided 0.25 to 0.50 inch totals across much of southeast and east central Nebraska with the event. However, there was a line of moderate to heavy rainfall that fell in an area east of Columbus, north of Omaha, and south of Sioux City, Iowa. Precipitation reports ranged from 1.25 to 1.80 inches. This led to one of the few changes on the current U.S. Drought Monitor depiction for Nebraska by reducing the D3 (extreme) drought designation to D2 (severe) drought (Figure 1).
The other significant moisture event occurred October 17-18 as a strong cold front pushed through the state. A narrow band of snowfall 1-2 counties wide fell from the northern Panhandle southeast through the southern Sandhill region, then eastward through east central Nebraska. Widespread 4-6 inch snowfall totals, with water equivalencies ranging from 0.50-0.80 inches fell across the southern Sandhill region. Precipitation totals dropped off dramatically north and south of this snow band, with liquid equivalent moisture ranging from nothing to a tenth of an inch.
Cumulative precipitation from October 6-12 (Figure 2) shows the impacts from these two storm systems across the state. Although some moderate snows were observed, most of the state failed to receive a tenth of an inch of moisture. Temperatures at the beginning and end of the period were well below normal, with above normal temperatures confined to the weekday period. The cold air intrusions were not as significant across southern Nebraska, as the southern half of the state had above normal temperatures, while the northern half of the state was slightly below normal (Figure 3).
A much more active storm pattern appears to be setting up for the state over the next week, with a good chance for accumulating snowfall this coming weekend. With numerous systems moving across the northern Plains over the next 7 days, harvest activity will likely slow down considerably. After four consecutive weeks of excellent harvest weather, a break would be welcome if it provides needed moisture, especially across the western half of the state.
Crop Progress
Harvest activity this past week continued to progress at a rapid pace, even with the inclement weather that moved across the state on October 18th. According to Nebraska Agricultural Statistics Service (NASS), the soybean harvest crossed the 90% threshold. Harvested acres stood at 92%, compared to 82% last week, 27% last year and the 5-year average of 31%.
With the soybean harvest nearing completion, corn and sorghum saw significant increases in acres harvested. The corn harvest stood at 58% complete, a gain of 24 percentage points from last week according to NASS. Last year at this point in time the corn crop was 27% complete and the 5-year average is 31% complete.
The sorghum harvest experienced a greater percentage increase than corn over the past week. According to NASS, the sorghum harvest stood at 60%, compared to 31% last week which translates into an acreage harvested increase of 29 percentage points. Last year the crop stood at 51% completed and the 5-year average is 35% complete.
Dry conditions across western Nebraska slowed down emergence. As of October 18, 72% of the wheat had emerged according to NASS. This was an increase of 12% points over last week, but still behind the 5-year average of 81% and 80% last year. Dry topsoil levels continue to stress newly emerged wheat with 14% of the crop rated poor to very poor. NASS reports that 38% of the crop was rated fair, 37% good and only 4% excellent.
Topsoil and subsoil moisture ratings continued to decline, even with the precipitation events that crossed the state October 11-12 and 17-18. NASS reports that 80% of the top soil is rated in the very short to short category which is a gain of 7 percentage points from last week. Subsoil moisture was rated 72% short to very short according to NASS. This is a gain of 8 percentage points over last week when 64% of acreage had short to very short ratings.
Outlook
Last week the GFS model suggested that little significant moisture could be expected through the remainder of the month. As is the case during the fall and spring seasons, weather models can change outlooks almost overnight. If the most current GFS model run (October 20) verifies, the next week will provide several tastes of winter weather before a sustained warming trend develops by month’s end and continues into the first full week of November.
The GFS model indicates that the central and eastern United States will see multiple rounds of precipitation as energy rotates around a broad upper air trough situated from the Rocky Mountains eastward through the western Great Lakes region. The first system is forecast to move across the northern Plains October 20, bringing light precipitation chances to extreme northern Nebraska.
This first system is expected to strengthen as it moves into the western Great Lakes with moderate (3-6 inch) snowfall to Minnesota and Wisconsin. At the same time, another piece of energy is predicted to move along the backside of the upper air trough and impact the northern Plains October 21-22. This system is forecast to move eastward and pull warmer air into Nebraska, with widespread snowfall likely from eastern Montana through the upper Great Lakes. Snowfall may approach 6 inches from eastern North Dakota through the northern half of Wisconsin.
The warmer air will bring a rebound in temperatures across the state with highs moving into the upper 50’s October 21 and 70’s October 22. As the warm air moves into the state, there are hints that thunderstorms could develop across extreme eastern Nebraska. The remainder of the state appears to be caught west and south of the primary precipitation pattern. As the this upper Plains system moves east, a surge of colder air will begin to enter northwestern Nebraska late during the second half of October 23.
Yet another piece of energy is predicted by the GFS model to move southward from eastern Montana on October 24. The GFS model takes this energy southward along the front range of the Rockies and moves it to the Texas Panhandle by October 26. It appears that a broad area of snowfall will develop across western Nebraska during the evening hours of October 24 and continue through most of October 25. This snowfall is forecast to continue developing southward and eastward as the day progresses, giving the entire state a good chance for accumulating snowfall.
At present, liquid equivalent moisture projected with this systems would bring 0.25-0.50 inches to the western 1/3 of the state. Snowfall amounts greater than 6 inches are possible for parts of the western Sandhill region, as well as the northern half of the Nebraska Panhandle. Further east and south, snowfall totals are projected to be in the 1-3 inch range.
As this cold air pushes south into the Texas Panhandle on October 26, very cold air will be pulled southward across Nebraska, effectively ending the growing season for those areas that have escaped a season ending freeze event. Low pressure is projected to develop over the Texas Panhandle and move east-northeast toward the eastern Ohio river valley by October 28. There may be an opportunity for light accumulating snowfall across southwest Nebraska on October 26th, as this area lies at the northern edge of the precipitation shield associated with this storm.
As this major low pressure system moves toward the Ohio Valley, it is projected to pull the upper air trough eastward. Very heavy rainfall and /or snowfall is likely across the central and eastern corn belt. For Nebraska, as this system pulls east of the state, upper air ridging is projected to develop by October 29 and continue through the first full week of November. High temperatures should rebound back into the 60’s and 70’s with no precipitation events projected. A return to favorable harvest weather is expected.
Al Dutcher, Agricultural Extension Climatologist with the Nebraska State Climate Office