Weather Review
Once again, this past week’s weather was dominated by a battle between competing air masses, an upper air ridge centered over the southern Plains and an upper air trough migrating across the northern Plains. This time the air mass behind the upper air trough lacked atmospheric moisture and the return of hot temperatures with very windy conditions June 28-30 created high evapotranspiration conditions for growing crops. With subsoil moisture levels depleting, crop stress was reported for across northeast Nebraska dryland acres, as well as irrigated fields impacted by structural damage of center pivot systems impacted by severe winds from early June thunderstorm activity.
Figure 1 shows the cumulative precipitation that fell from the morning of June 26th through the morning of July 3rd. Precipitation that fell after 9 am Central and Mountain Daylight Savings Time is not included in this analysis and will be reflected in next week’s edition. The vast majority of moisture reported during this period occurred from the morning of June 30th through the morning of July 1st in response to an upper air trough moving across the northern Plains.
Precipitation reports from NERain observers indicate that most concentrated area of moisture fell along and north of the I-80 corridor from west central through east central Nebraska. Precipitation ranged from 0.25 to 1.50 inches in this area, with the highest totals occurring where thunderstorm activity was more pronounced. Additional areas receiving moisture included the northern Panhandle and a small area of south central and southeast Nebraska immediately adjacent to the Kansas border. The greatest 24 hour precipitation total reported last week occurred in the Superior area with 4.30 inches.
On the flip side, the northeastern Sandhill region, northeast Nebraska and southwestern areas to the west of McCook received no measurable moisture. These areas stand out in Figure 2, which depicts precipitation anomalies compared to normal expectations for June 27th through July 3rd. Precipitation departures exceeded 0.75 inches across pockets of northeast, central and southwest Nebraska. It is these areas that have the highest probability of drought deterioration when the U.S. Drought Monitor is updated July 7th.
Although Nebraskan’s did get some limited relief from hot temperatures this past weekend, most of last week was dominated by high temperatures consistently in 90’s to low 100’s across the northwestern ¾ of the state. Average temperature anomalies ranged from 1 F to 4 F above normal across the northern half of the state, as well as southwest Nebraska as depicted in Figure 3. Below normal anomalies were mainly confined to south central, east central and southeast Nebraska where cloud cover was more extensive and limited daytime heating compared to western regions of the state.
The highest maximum temperature recorded each day across the state ranged from 89 to 104 F using airport locations June 27th through July 3rd. Daily high temperatures are as follows: 27th (93 – Chadron), 28th (99 - Ogallala), 29th (104 – Chadron, Ogallala, Valentine), 30th (100 – McCook), 1st (89 – Valentine), 2nd (92 – Scottsbluff), 3rd (101 – Chadron). With drier air in place across the Panhandle, it is not surprising that maximum temperatures were hot for this time of year. However, the dry air mass also contributed to unseasonable cool low temperatures.
The lowest daily minimum temperature recorded each day across the ranged from 43 F to 59 F using airport locations June 27th through July 3rd. The marks the second consecutive week that the daily low temperature readings were all recorded at Panhandle locations. Daily low temperatures are as follows: 27th (43 – Alliance), 28th (45 - Alliance), 29th (55 – Alliance), 30th (51 - Kimball), 1st (53 – Kimball, Chadron), 2nd (58 – Kimball), 3rd (59 – Gordon, Kimball). So the diurnal spread between maximum and minimum temperatures ranged from 34 F on July 2nd to 54 F on June 28th. The Panhandle would normally experience a diurnal temperature range of 30-35 F this time of the year.
Crop Progress
With above normal temperatures and below normal moisture this past week across a large swath of the northern and southern 1/3 of Nebraska, it is not surprising that the Nebraska Agricultural Statistics Service (NASS) reported declines in crop conditions and soil moisture estimates in their most recent crop progress report. Wheat and pasture had the largest crop rating declines, likely due to the fact that the vast majority of acreage dedicated to these crops are located across western Nebraska where last week's heat and dryness were most pronounced.
NASS reports that pastures as of July 3rd were rated 24% very poor, 32% poor, 31% fair, 12% good and 1% excellent. Compared to conditions through June 26th, the very poor category doubled from 12 percent and good conditions shrank in half from 24 percent the previous week. There was also a 3 percentage point increase in the poor rating, while the pastures rated good dropped 3 percentage points.
The wheat crop continues to deteriorate as the first harvest information for 2022 was included in this week’s crop report. NASS estimates that 22% of crop has been harvested compared to 6% last year and the 5-year average of 11 percent. Below normal moisture from last fall through this spring, coupled with above normal temperatures during June sped up maturity and were contributing factors for below normal yields across the western 1/3 of Nebraska. Current crop condition reflect these disappointing yields and NASS reports that the wheat crop is currently rated 28% very poor, 17% poor, 38% fair, 15% good and 2% excellent. The very poor category expanded 12 percentage points compared to conditions on June 26th.
Topsoil and subsoil moisture readings declined last week due to above normal temperatures and the lack of widespread precipitation. NASS reports that topsoil moisture as of July 3rd was rated 23% very short, 37% short, 39% adequate and 1% surplus. Subsoil moisture was rated 26% very short, 33% short, 40% adequate and 1% surplus. Topsoil moisture rated very short increased 3 percentage points compared to the previous week, while the adequate rating dropped an equivalent 3 percentage points. Subsoil moisture rated very poor increased 5 percentage points compared to the previous week, which was at the expense of the short and adequate ratings that decreased 2 and 3 percentage points, respectively.
Corn and soybean condition ratings declined slightly during the past week, while sorghum showed a slight improvement. For both corn and soybeans, 12% of the crop is rated very poor to poor, both unchanged from the previous week. Corn rated good to excellent as of July 3rd is 62%, a decrease of 2 percentage points from the previous week. Soybeans rated good to excellent is 61%, a decrease of 1 percentage point from the previous week. Sorghum rated very poor to poor was 10% this week, an improvement of 1 percentage point from the June 26th rating. The crop was rated 63% good to excellent, which is an improvement of 1 percentage point from the previous week.
With thunderstorm development the past two days across Nebraska and several more opportunities for moisture this week, expectations are that warm season crops will show improvement when NASS releases their next crop progress report on July 11th. Areas receiving more than two inches of moisture from 8 am July 5th through 8 am July 12th are the most likely candidates for drought improvement when next week’s U.S. Drought Monitor is released on July 14th.
Weather Outlook
Although Nebraska has seen a significant increase in thunderstorm activity the past two days, the GFS model run issued the morning of July 6th has turned hotter and significantly drier after July 8th. Last week, the GFS model was indicating that hot and dry conditions would develop from July 11th through July 18th, before cooling back into the 80’s, along with periodic thunderstorm chances. The GFS model currently indicates that hot and dry conditions are favored from July 12th through July 22nd.
In the short term, the GFS model indicates that energy will rotate along the periphery of the southern Plains upper air ridge July 7th and 8th. Monsoonal moisture will be drawn northward through the southern and central Rocky Mountains on the backside of the ridge, then shunted eastward across Nebraska. On July 7th, the southern half of Nebraska has the best opportunity for widespread moisture, with some localized heavy precipitation (> 2 inches) south of the I-80 corridor. The upper air ridge begins to push northward on July 8th and this would shift the best opportunity for precipitation to the northern half of Nebraska.
The ridge builds further northward on the 9th, but also deepens the upper air trough forecast to be over the eastern corn belt. A piece of energy pushing southeast on the backside of this trough is forecast to generate showers and thunderstorms across the eastern 1/3 of Nebraska, with the northeast ¼ of the state having the best opportunity for widespread moisture. From July 10th through July 22nd, the GFS model indicates that the only precipitation opportunities for Nebraska are on the 12th and 21st.
On July 12th, the GFS model indicates an upper air trough will move across the northern High Plain and drive a surface cold front into southern Nebraska. Precipitation is forecast to move southward during the day and weaken as it approaches the Kansas border. North Central and northeast Nebraska are currently depicted as having the highest precipitation probabilities with this cold front. Another upper air trough is forecast to cross the northern Plains July 20th and drive a cold front through the northern half of the state on July 21. The GFS model currently limits precipitation to the northern 1/3 of Nebraska and appears to generate less than 0.50 inches of moisture.
High temperatures are forecast to warm through the remainder of this week according to the GFS model, with upper 90’s to low 100’s possible July 9-10. A slight cool down is forecast July 11-12 as an upper air trough moves across the northern High Plains and high temperatures should be around 10 degrees cooler. The southern Plains upper air ridge is forecast to build northward and dominate Nebraska’s weather July 13-20. High temperatures are forecast to be in the 90’s to low 100’s during this period, with the hottest temperatures located over the western half of the state.
The GFS model does show a slight cool down on July 21st (5-7 F cooler) before rebounding back into the 90’s and low 100’s July 22nd. Hopefully, this recent movement toward a longer period of heat coupled with little to no moisture by the GFS model is overblown. However, if it is not, then this week’s precipitation events will be important to carry crops through this hot spell, especially with the onset of warm season crop reproduction.
Al Dutcher, Agricultural Extension Climatologist, Nebraska State Climate Office