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Colder with Fire to West/Sally in the Tropics on September 7-13, 2020
 
A large storm system ("L") in the Rockies was set to spread cold air to the east on 09/07/2020. However, a ridge of high pressure ("H") over the southeast states prevented fall conditions from reaching Arkansas, and it stayed warm locally.
In the picture: A large storm system ("L") in the Rockies was set to spread cold air to the east on 09/07/2020. However, a ridge of high pressure ("H") over the southeast states prevented fall conditions from reaching Arkansas, and it stayed warm locally.
 

After a very wet August in western Arkansas, and a deluge across northern and western sections of the state to begin September, the pattern slowed down a lot locally through the middle of the month. A ridge of high pressure parked over the southeast United States, and provided mostly warm and dry conditions.

 

Temperatures dropped 30 to more than 50 degrees from the Rockies into the Plains behind a cold front in the twenty four hour period ending at 400 pm CDT on 09/08/2020. Ahead of the front, readings remained seasonal to a little above average in Arkansas.
In the picture: Temperatures dropped 30 to more than 50 degrees from the Rockies into the Plains behind a cold front in the twenty four hour period ending at 400 pm CDT on 09/08/2020. Ahead of the front, readings remained seasonal to a little above average in Arkansas.
 

The ridge prevented a significant cool air mass from plowing through the region from the west. Parts of the Rockies and Plains experienced a thirty to more than fifty degree temperature drop from the 7th to the 8th. Thermometers at Denver, CO, Amarillo, TX, and Kansas City, MO went from the lower 90s at 400 pm CDT on the 7th to 34 degrees, 47 degrees, and 57 degrees respectively twenty four hours later. It cooled down as far south as San Antonio, TX, with a low temperature of 57 degrees on the 10th. On the same day, the low at Dallas, TX was 55 degrees, and the high was only 69 degrees. Meanwhile, afternoon readings were in the upper 80s to around 90 degrees at Little Rock (Pulaski County).

 

In the picture: Record heat quickly became record cold and snow at Denver, CO in early September, 2020. The information is courtesy of the National Weather Service in Boulder, CO via Twitter.
 

The heat on the 7th was nothing new at Denver, CO. On that day, it was at least 90 degrees for the 73rd time in 2020. This tied 2012 for the most 90 degree days locally. On the 5th, it was 101 degrees, which was the all-time high temperature for September, and the latest 100 degree day on record.

It was a different world by the morning of the 8th. It was 31 degrees in the mountain metropolis, which became earliest recorded freeze (tied with 1962). There was also an inch of snow, which was the second earliest measurable snowfall. This also broke a streak of nineteen consecutive snowless Septembers in the city.

Elsewhere, it was the earliest measurable snow at Fort Collins, CO on the 8th, and at Pueblo, CO on the 9th. At the latter site, this broke a record that stood since 1898. The snow in the central Rockies slowed the growth of a huge fire (Cameron Peak) just north of Estes Park, CO. The fire consumed just over 100,000 acres before flakes starting flying, and was only 4 percent contained as of the 13th.

 

A moderate to exceptional drought (D1 to D4) was ongoing in the western United States on 09/08/2020.
In the picture: A moderate to exceptional drought (D1 to D4) was ongoing in the western United States on 09/08/2020.
 

The fire in Colorado was partly due to very dry conditions, with widespread drought across the western United States. Wildfires were especially bad/destructive along the Pacific Coast from Washington to California.

 

In the pictures: Twenty large wildfires torched more than 400,000 acres in Oregon and Washington as of 09/08/2020. The information is courtesy of USDA Forest Service Pacific Northwest Region via Twitter.
 

It was absolutely awful in Oregon. Fires forced the evacuations of at least 40,000 people. Entire towns (such as Phoenix, OR and Talent, OR) and hundreds of homes were torched by fire. In a press conference, the Governor of Oregon declared: "This could be the greatest loss of human lives and property due to wildfire in our state's history.” In California, an unprecedented 3,000,000 acres had burned by the 12th. In northern sections of the state, the August Complex fire (a result of three dozen separate fires triggered by lightning in mid-August) was the largest ever in the state at over 850,000 acres. So many fires led to copious amounts of smoke and poor air quality in parts of the west.

 

In the video: The HRRR model showed a large storm system (swirl moving from the central Rockies to the northern Plains) dragging smoke from fires across the Western United States into areas farther east on 09/11/2020. The information is courtesy of the Cooperative Institute for Meteorological Satellite Studies (CIMMS) at the University of Wisconsin-Madison via Twitter.
 

The smoke spread to the east toward Arkansas by the same storm system that brought colder air felt by our neighbors to the north and west.

 

The satellite showed a large storm system in the upper Midwest trailed by smoke across the southern United States on 09/12/2020. The smoke was from wildfires mostly along the Pacific Coast from Washington to California.
In the picture: The satellite showed a large storm system in the upper Midwest trailed by smoke across the southern United States on 09/12/2020. The smoke was from wildfires mostly along the Pacific Coast from Washington to California.
 

While the smoke was not at ground level, it was certainly visible aloft. An otherwise blue sky became milky white as smoke invaded our atmosphere from the southwest. Sunsets became more colorful (reddish hue) as a result.

 

One hundred sixty eight hour (seven day) rainfall ending at 700 am CDT on 09/14/2020.
In the picture: One hundred sixty eight hour (seven day) rainfall ending at 700 am CDT on 09/14/2020.
 

As far as rainfall from the 7th through the 13th, portions of northern and central Arkansas received nothing at all. At the North Little Rock Airport (Pulaski County), after 1.09 inches of precipitation on the 1st, only 0.07 inch occurred through the 13th. Russellville (Pope County) had 5.47 inches on the 1st/2nd, and 0.03 inch to follow. Jonesboro (Craighead County) got 2.60 inches on the 1st/2nd, and 0.01 the next eleven days.

Parts of the south did get significant rain. In the twenty four hour period ending at 700 am CDT on the 11th, El Dorado (Union County) picked up 2.59 inches of liquid. By the next morning, Ashdown (Little River County) had 1.70 inches. A day later, 2.54 inches of rain was measured in Fordyce (Dallas County), with 1.65 inches at Cane Creek State Park (Lincoln County). These higher amounts were spotty.

For the month (through the 13th), it was more wet than dry overall. Locales that had below average precipitation were generally subpar by under an inch. Some sites with above average totals were in the plus category by over three inches. 

 

Precipitation in September, 2020 (Through the 13th)
Site Amount Normal +/- % of Normal
Fayetteville (NW AR) 1.39 1.88 -0.49 74%
Harrison (NC AR) 2.42 1.79 +0.63 135%
Jonesboro (NE AR) 2.61 1.31 +1.30 199%
Fort Smith (WC AR) 5.49 1.66 +3.83 331%
Little Rock (C AR) 1.27 1.35 -0.08 94%
West Memphis (EC AR) 0.81 1.11 -0.30 73%
Texarkana (SW AR) 1.49 1.53 -0.04 97%
El Dorado (SC AR) 4.51 1.32 +3.19 342%
Pine Bluff (SE AR) 0.74 1.01 -0.27 73%

 

Tropical Storm Sally headed slowly westward across the Gulf of Mexico toward southeast Louisiana on 09/13/2020. The system became a hurricane the next day, and the track eventually shifted to the east toward Alabama and the Floridan panhandle. The forecast is courtesy of the National Hurricane Center.
In the picture: Tropical Storm Sally headed slowly westward across the Gulf of Mexico toward southeast Louisiana on 09/13/2020. The system became a hurricane the next day, and the track eventually shifted to the east toward Alabama and the Floridan panhandle. The forecast is courtesy of the National Hurricane Center.
 

On the 13th, the focus was on the tropics. In the Gulf of Mexico, Tropical Storm Sally (which eventually became a hurricane) was headed for the central Gulf Coast. Arkansas had already been hit by Cristobal in June, and Laura in August. This time around, it appeared Sally would go well east of the state. The system was a slow mover, with prolonged downpours leading to 15 to more than 20 inches of rain from far southern Alabama to the Florida panhandle.