October sowing seeds of seasonal temps

A strong cold front resulted in moderate to heavy precipitation across the Great Plains, Ozarks, and western Gulf Coast during the first week of October.

The most widespread improvements were made to southern Arkansas, northwestern Louisiana, southeastern Oklahoma, and eastern to central Texas where more than 2 inches of precipitation was observed this past week. Following anomalous heat across the central United States to start October, the cold front ushered in much cooler temperatures from Oct. 5 to 7.

The first frost or freeze of the fall affected the northern to central Great Plains on Oct. 7.

As the cold front progressed eastward, drought-easing rainfall overspread parts of Illinois and northern Indiana. Farther to the south, short-term drought continued to expand north and east across the Southeast.

South

A broad 1-category improvement was made to southern Arkansas, northwestern Louisiana, southeastern Oklahoma, and eastern to central Texas where more than 1.5 inches of precipitation occurred this past week.

SPIs at multiple time scales, soil moisture, and 28-day average streamflows were also factors in determining where to depict the improvements. For areas that received more than 3 inches of precipitation and there was support from the NDMC’s drought blends, a 2-category improvement was justified across southwestern Arkansas, northeastern Texas, and the Texas Gulf Coast.

Drought coverage and intensity across Texas peaked in early September when 85.68% of the state was covered with drought (D1 or higher) and two-thirds of the state was designated with severe (D2) to exceptional (D4) drought.

Based on 90-day SPEI, an expansion of D2 to D4 was made to parts of Mississippi. Impacts in Mississippi include poor pasture conditions, soybean and peanut losses, and cattle sell offs. The 90-day SPEI also supported an expansion of D4 across northeastern Louisiana. Increasing short-term dryness led to an expansion of abnormal dryness (D0) and moderate drought (D1) across Tennessee.

Midwest

Widespread precipitation amounts of more than 0.5 inch along with much cooler temperatures resulted in improvements throughout Minnesota. Parts of northeast Minnesota were removed from abnormal dryness since Duluth had its second wettest September on record.

These improvements extended east to include northwestern Wisconsin. Closer to the Green Bay area, a 1-category degradation was made due to increasing short-term precipitation deficits and declining soil moisture. NDMC’s long-term drought blend and six-month SPI supported a 1-category degradation to parts of northwestern and central Missouri.

High Plains

A 1-category improvement was made to northwestern North Dakota and northeastern South Dakota where more than 1 inch of precipitation occurred this past week. Small improvements were also warranted in central Nebraska with the wet start to October.

Although parts of eastern Nebraska also received heavier precipitation, NDMC’s long-term blend supports D2+ levels of drought. Based on drier-than-normal conditions during the past 60 days and soil moisture, abnormal dryness (D0) was expanded across the southwestern corner of Nebraska. The 60-day SPI, soil moisture, and NDMC’s short-term blend supported an increase in D0 and the addition of D1 across southern Wyoming.

The suppressed 2023 Monsoon and the six-month SPEI supported an expansion of D2 in southwestern Colorado, while increasing short-term dryness led to increasing D0 coverage across northwestern Colorado.

West

A 1-category improvement was made to northeastern Montana where more than 1 inch of precipitation occurred this past week. Precipitation during the past two weeks along with long-term SPIs supported the removal of extreme drought (D3) in north-central Montana.

Abnormal dryness (D0) was expanded across northeastern Utah due to increasing short-term dryness during the past one to three months and this was also consistent with changes made to adjacent Colorado and Wyoming.

Looking ahead

During the next five days, Oct. 12 to 16, an intense low-pressure system is forecast to track from the central Rockies and Great Plains eastward to the Midwest and Central Appalachians. A swath of heavy precipitation (1 to 3 inches) is likely to accompany this surface low.

On Oct. 12, a vigorous area of mid-level low pressure is expected to bring heavy snow (6 to 12 inches) to the higher elevations of Wyoming. A low-pressure system is forecast to move offshore of the Southeast by Oct. 13 after it brings widespread precipitation to parts of the Southeast. Mostly dry weather is forecast to persist across the Tennessee Valley, while much drier weather prevails across the southern Great Plains.

The Climate Prediction Center’s six- to 10-day outlook, valid Oct. 17 to 21, favors near to below-normal precipitation throughout much of the contiguous U.S. Increased probabilities for above-normal temperatures are forecast across the West and northern to central Great Plains.

Brad Pugh is with the National Oceanic and Atmospheric Administration and Climate Prediction Center.