27 October 2020

Snowstorm Accumulation Totals
Snowstorm Accumulation Totals

October 24-27 Cumulative Snowfall - National Perspective. Source: NOAA National Operational Hydrologic Remote Sensing Center

Snowstorm Accumulation Totals

Snowstorm Accumulation Totals
Snowstorm Accumulation Totals

October 24-27 Cumulative Snowfall - Nebraska Perspective. Source: NOAA National Operational Hydrologic Remote Sensing Center

Snowstorm Accumulation Totals

General Observations

A series of storm systems pivoted around the base of an upper air trough situated over the northern Plains this past week. The first two pieces of energy moved across the northern Plains and upper Midwest, dropping significant snowfall across North Dakota, Minnesota, Wisconsin and the upper peninsula of Michigan. Nebraska was located on the southern periphery of these storms and precipitation totals were light.

According to NERain observations, precipitation totals ranging from a trace to 0.20 inches were reported with the first system across the central third of the state from west to east on October 20. The second system brought scattered light moisture ranging from a trace to 0.10 inches north and west of a line from Nebraska City to Beatrice October 22-23. Totals southeast of this line ranged from 0.10 to 1.02 inches. The heaviest moisture fell across the southeast half of Richardson county where totals ranged from 0.50-1.02 inches.

After a brief respite from the light moisture activity, a surge of Arctic air on the backside of the upper air low over the northern Plains helped to develop a powerful snowstorm that slid down the front side of the Rocky Mountains. This system was eerily similar to the path taken by the Labor Day week storm that brought record cold and accumulating snowfall to the northern half of the Panhandle.

The main impacts of this storm began in northwestern Nebraska during the evening hours of October 24 and came to an end across southern Nebraska during the morning hours of October 26. According to NERain observers taking snowfall measurements, total storm snowfall was reported to be in the 7-10 inch range across the Panhandle and northwestern Sandhill region. Unofficial reports of 12-14 inches were noted west of Scottsbluff .

A band of 5-8 inches was reported across the southern Sandhill region from Anselmo to Ord. Snowfall totals from 3-5 inches were common across the eastern Sandhill region, northeast, central and southwest Nebraska. South central and east central Nebraska snow totals ranged from 1 to 3 inches, with trace to one inch totals reported from counties bordering Kansas.

A visual representation of satellite estimated snow totals can be found in Figures 1 and 2. Based upon ground truth, these estimates appear to be very close to observational data. Unfortunately, the data provider didn’t include contour codes on the maps and to interpret snow totals, use the following color codes: Orange (8-12), Yellow (6-8), Dark Blue (4-6), Dark/Medium Blue (3-4), Medium Blue (2-3), Medium/Light Blue (1-2) and Light Blue (Trace – 1).

This snowfall event provided very valuable moisture for western Nebraska, with considerably light amounts across the southeastern 1/3 of the state. NeRain reports indicate that liquid equivalent moisture with this system ranged from 0.40-0.70 inches across the Panhandle, with one report exceeding an inch. The northern half of the state and the southwest reported 0.30 to 0.60 inches of moisture, while areas south of I-80 from south central though southeast Nebraska reported 0.01 to 0.30 inches of moisture.

Crop Progress

The light precipitation events prior to this past weekend’s snow storm slowed down harvest activity compared to the prior week, but sizable gains were still noted by Nebraska Agricultural Statistics Service (NASS). NASS reported that producers had 5.2 days of field activity, with the most significant period of delays relegated to this past weekend. Producers will likely be delayed until the snow melts and soil surfaces dry. With a return to warmer and dry weather, producers should be returning to harvest activities by the latter end of this week.

NASS reports that the soybean harvest is virtually complete with 97% of the acreage harvested. Well ahead of last year and the 5-year average, both at 78 percent. The grain sorghum harvest stood at 82% complete, compared to 36% last year and the 5-year average of 51 percent. Even with weather delays there was a 22 point increase in harvested acres compared to last week.

The corn harvest slowed down considerably compared to the last crop reported issued by NASS. As of October 25, 76% of the corn acres had been harvested, compared to 58% last week. Last year 40% of the corn had been harvest, while the 5-year average is 46%. The slower pace is likely the result of moisture events that had a larger impact on the northern half of the state than on southern Nebraska where the harvest is nearly complete.

NASS reports that top soil moisture is rated 73% short to very short, 27% adequate, and 0% surplus. Subsoil moisture is rated at 69% short to very short, 30% adequate, and 1% surplus. The dry conditions continue to be reflected in pasture ratings and NASS reports that 40% are poor to very poor, 27% are fair and 32% good to excellent. With the snow event ongoing at the end of the reporting period, topsoil moisture and pastures should see some improvement in next week's NASS crop progress report.

The widespread snowfall across the Panhandle and southwest Nebraska is welcome news as this region represents the majority of wheat produced in the state. According to NASS, 21% of the crop was rated poor to very poor, 36% fair and 43% good to excellent. Emergence stood at 84%, compared to 90% last year and the 5-year average of 89%. The moisture from the snowstorm should help germinate wheat not emerged and provide surface moisture for root growth prior to winter dormancy.

Outlook

According to the GFS model issued the morning of October 27, it appears that the next two weeks will be dominated by dry weather. There is one storm system that could impact northern Nebraska with precipitation, but present forecasts offer less than a 20% chance of this occurring. The biggest issue will be dry cold fronts moving through the region, lowering relative humidity levels and increasing the fire danger risk.

The upper air trough responsible for this past weekend’s snow storm pulled Arctic air southward into the Texas Panhandle and formed a cutoff upper air low. This low is projected to slowly move east-northeast through the southern Plains October 27-29 and merge with Hurricane Zeta which is projected to make landfall across coastal Louisiana. This entire complex will move across the southeastern U.S. and the southern Ohio river valley.

The northern periphery of the precipitation shield associated with this storm is projected to pass just south and east of Nebraska. If precipitation is realized, it will likely occur across the southeastern four counties bordering Kansas. The GFS indicates the best opportunity for moisture would be October 28-29. After this system moves eastward, upper air ridging will build across the central United States bring a return to dry weather into the first third of November.

As the ridge builds over the central Plains, high temperatures will return to the 50’s and 60’s October 30-31. A weak cold front will move through the state during Halloween night in association with a trough crossing the northern Plains. High temperatures will drop 5-7 F on November 1, before quickly warming into the 60’s November 2-3 as a surface high builds over the central High Plains.

Another trough is projected to move across the northern Plains November 4, which will drive a cold front through the state. Once again, the GFS keeps moisture well north of the state with high temperatures cooing back into the 50’s to low 60’s. The upper air ridge rebuilds from the western into the central U.S. October 6-7 and if the GFS is correct, high temperatures may reach the 70’s across western Nebraska.

Another upper air low is projected to move across the northern Plains October 8-9, driving a cold front through the state. High temperatures may drop back into the 40’s. Currently the GFS model keeps moisture north of the state, but it also represents the best opportunity for moisture within this forecast period. At this time of the year, models can change rapidly and this system bears watching for more southward development. A return to dry weather is forecast October 10-12, with high temperatures warming into the mid 50’s to low 60’s.

Al Dutcher, Agricultural Extension Climatologist, Nebraska State Climate Office

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