07 July Weekly Update

7-day temperature departures
7-day temperature departures

Average Temperature Departures from June 29 - July 5, 2020. Source: High Plains Regional Climate Centerr

7-day temperature departures

7-day precipitation departures
7-day precipitation departures

Precipitation Departures from June 29 - July 5, 2020. Source: High Plains Regional Climate Center

7-day precipitation departures

Drought Monitor depiction for the High Plains region issed July 2, 2020
Drought Monitor depiction for the High Plains region issed July 2, 2020

High Plains Drought Monitor for July 2, 2020. Source: National Drought Mitigation Center

Drought Monitor depiction for the High Plains region issed July 2, 2020

60 day precipitation trend for the High Plains region
60 day precipitation trend for the High Plains region

60-day Percent of Normal Precipitation for the High Plains Region. Source: High Plains Regional Climate Center

60 day precipitation trend for the High Plains region

60-day precipitation trend for Nebraska
60-day precipitation trend for Nebraska

60-day Percent of Normal Precipitation for Nebraska. Source: High Plains Regional Climate Center

60-day precipitation trend for Nebraska

General Observations

The upper air pattern during this past week featured a dominant high pressure ridge centered over the southern Plains and an upper air trough situated over the northwestern U.S. Energy ejecting out of the upper air low as it slowly moved toward the northern Plains triggered several rounds of thunderstorms across limited areas of the state.

Aggressive storm activity was mostly focused across the northern Plains, but sections of Nebraska were able to receive beneficial moisture, at a cost. Severe weather rolled through the Panhandle region July 2 - 3 with 3 tornado reports, 15 hail reports, and 8 wind reports. The remainder of severe weather occurred on July 6 across north central and northeast Nebraska where 2 hail and 7 wind reports were submitted.

With several rounds of thunderstorms crossing the state and a surge of dew point temperatures into the upper 60s to mid 70s, high temperatures remained primarily in the mid 80s to mid 90s. Low temperatures increased to the mid 60s to low 70s over the eastern two-thirds of the state. Therefore, weekly average temperatures were generally a couple of degrees above to below normal across the state.

The increase in dew points, although uncomfortable, reduced crop water demands across eastern Nebraska. Additionally, lighter winds reduced evaporative demands. This will help offset some of the stress likely occurring across the drier areas of western Nebraska, as above normal moisture was limited to small portions of the southeast, north central, northeast, and the Panhandle.

Crop Progress

According to the Nebraska Agricultural Statistics Service (NASS), corn conditions declined from the previous week as the good/excellent rating fell from 76 % to 74%. Corn reaching the silk stage was reported to be 4%, compared to 1% last year, and the 5-year average of 11%. Soybean condition improved 1 percentage point from 75% to 76% good to excellent. NASS reported that 41% of the soybeans were blooming, compared to 7% last year, and the 5-year average of 27%.

Pasture ratings continue to decline, as has been the case for the past month. NASS reports that pastures in the good to excellent category stood at 63%, a decrease of 3 percentage points from last week. Only 4% of the pasture acres were rated excellent, with 5% rated very poor and 9% poor. With limited moisture expected, coupled with above normal average temperature across western Nebraska the next 14 days, further deterioration is anticipated.

The latest U.S. Drought Monitor released July 2 and based upon data through the morning of June 30, shows abnormal dryness expansion into central and northeastern Nebraska. Moderate drought conditions have been assigned to the northwestern Panhandle and southwestern corner of the state. The 60-day percent of normal moisture map for Nebraska shows the worst moisture conditions are likely occurring across the southern Panhandle, the northwestern corner of the Panhandle, as well as portions of west central and southwest Nebraska, where precipitation has been averaging 25-50% of normal.

Outlook

The GFS morning run issued July 7 favors a continuation of above normal temperatures with limited chance of widespread rainfall through July 21, the final day for the forecast model package. Even with the models tendency to project above normal temperatures, long lived extreme heat is not expected. In fact, depending on how the northwestern United States upper air trough progresses, there may be short intervals of normal to slightly below normal temperatures.

The GFS model indicates that the upper air trough over the northwestern U.S. will migrate toward the northern Plains July 7-10. This will help drive a cold front through the state July 8, with the GFS model aggressively pointing toward severe thunderstorm development over the eastern half of the state. As the upper air low swings toward the western Great Lakes, zonal (west to east) flow will set up over the northern U.S. July 9-11. Several pieces of energy are expected to move through the state, with the best opportunity of moisture assigned to north central and northeast Nebraska.

Another upper air trough is expected to build into the northwestern U.S. July 12-14, forcing the ridge over the southern Plains and Rockies to expand northward. The GFS model indicates dry weather and high temperatures moving into the mid 90s south, with low 100s possible across southwest Nebraska. If rainfall materializes across eastern Nebraska July 8-9, it will likely increase water vapor at the surface and create the potential for heat index values above 110°F during the peak of the afternoon July 13-14.

The GFS model then breaks down the advertised ridge July 16-18 as it moves the northwestern U.S. trough due eastward toward the northern High Plains. The GFS is also very aggressive initiating thunderstorm development across the entire state July 16-17, with precipitation shifted into the eastern half of the state July 18. Hot and dry conditions are then forecasted to return July 19-21 at the end of the model run, as the GFS expands the southern Plains high pressure northward.

Source: Al Dutcher at Nebraska State Climate Office

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