The Freaky East Wind
of Eastern Oklahoma and Western Arkansas


The Freaky East Wind (hereupon referred to as FEW) is a relatively common occurance along the Arkansas River Valley extending from Arkansas into Eastern Oklahoma. Its presence can be seen when there is a easterly wind in reporting stations anywhere from occasionally as far west as Gore, OK in Sequoyah County, eastward through the Ft. Smith, AR area, and extending sometimes possibly as far east as Conway, AR in Faulkner County. The reporting stations surrounding the Arkansas River Valley will likely be reporting southerly winds. The FEW most often occurs overnight through early morning, usually ending by noontime, but can occur at anytime and last a much longer period of time.

The area of the Arkansas River Valley from extreme eastern Oklahoma into western Arkansas lies west to east with 2000+ ft tall mountainous regions on the north and south sides (the Ozark Plateau - Boston Mtns on the North and the Ouachita Mtns on the South). Below is elevation relief map and map showing the area of occurance of the FEW.


Green Colors = Lower Elevations & Red Colors = Higher Elevations

You can clearly see the elevational difference between the Arkansas River Valley and the areas north and south of it. The most likely cause(s) of the FEW are orographic although there are several different scenarious in which the FEW can be created and maintained.

The most common scenario for FEW formation is: Southerly or southwesterly winds across much of Eastern Oklahoma and Western Arkansas. As the southerly wind hits the 2000+ tall Oucahita mountains it rides up and over the Arkansas River Valley and continues over the Ozark Plateau/Boston Mountains. The creates a sort of top over the valley where it is somewhat protected from the southerly winds.

At this point the valley is protected from the mean airflow.

If you look above at the elevation relief map you will see that in Oklahoma the southern mountains (the Ouachitas) lye further west than the northern mountains (the Boston Mtns/Ozark Plateau). In Arkansas the northern moutains (the Boston Mtns/Ozark Plateau lye further east than the southern mountains (the Ouachitas). This creates areas of differential pressure. Low pressure develops on the west end of the Arkansas River Valley as a sort of vaccum develops in the lee of the southern mountains (the Ouachitas) while an area of high pressure develops along the windward side of the northern mountains (Boston Mtns/Ozark Plateau).

As the pressure gradient forms between the eastern and western ends of the Arkansas River Valley, the protected valley feels the effects and the pressure gradient tries to equalize by sending an easterly wind up (towards the west) the valley towards the area of lower pressure.

The image below shows all of the parts that come together to form the FEW imposed on a elevational relief map. Yellow block marked 1 shows the area of the Western portion of the Ouachita Mountains. Red block 3 shows the Western portion of the Ozark Plateau/Boston Mtns. You can clearly see that the Ouachita Mtns (yellow block 1) lye further west than the Ozark Plateau/Boston Mtns (red block 3). As the south winds ride up and over the Ouachita it creates a very weak area of low pressure on the leeward side of the Ouachita Mtns. To the east, yellow block 2 shows the eastward extent of the Ozark Plateau/Boston Mtns. And red block 4 shows the eastward extent of the Ouachita Mtns. You can cleary see that the Ozark Plateau/Boston Mtns (yellow block 2) lye further east than the Ouachita Mtns (red block 4). As the south wind brushes by the Ouachita Mtns it crosses the Arkansas River and collides with the Ozark Plateau/Boston Mtns creating a area of high pressure on that windward side of the Ozark Plateau/Boston Mtns. The FEW is formed as a result of the pressure gradient between the eastward lying high pressure and westward lying low pressure.

Also, frequently in the weather of eastern Oklahoma and western Arkansas, the winds are stronger in Oklahoma than Arkansas and while I dont think this has to happen to produce the FEW, I do think it is very important in the intensity and longevity of the FEW.

For the FEW to form the air along the valley has to be fairly stable. This is why the FEW forms usually after sunset and persists sometimes till noon. As the sun sets and the effects of daytime heating began to subside the air in the valley becomes calmer and thus easier to feel the slight effects of the pressure gradient between the west and east ends of the valley and the FEW is formed. As the sun rises and daytime heating commences, air parcels began to rise and mix, and the slight pressure differences cannont be equalized due to the "interference" between them and this brings and end to the FEW.

This is the most common scenario in which the FEW can form but there are other ways it can develop.

Besides the formation of the FEW, there are some important side effects of it.

One of the more easily understood and more frequent effects is: On many spring nights when there is a strong south wind ushering in warm moist air from the Gulf Of Mexico ahead of an approaching trough/low pressure system, the FEW forms and the valley remains protected enough for radiational cooling to commence whereas the neighboring mountains are unaffected by the FEW and with the strong south winds radiational cooling is very weak. Therefore, whereas, usually Fayetteville would be around 5 degrees cooler than Fort Smith, during this type of event Fayetteville could be 5, 10, even 15 or more degrees warmer than Fort Smith.


There are some real questions about the FEW. One that has been asked a lot is: How does the FEW affect storms that are moving into the Arkansas River Valley and specifically the Fort Smith, AR area. This question may never be fully answered due to several pre-existing questions.

Climatologically, conditions tend to be more favorable for severe storms and tornadoes in Oklahoma than in Arkansas. How do we know that a storm that might be weakening as it moves into the Arkansas River Valley is not weakening because its simply moving into more unfavorable conditions that have nothing to do with the FEW?

Also, some have mentioned about how supercells travelling from SW to NE across the area can be affected by the FEW. For about 99% of the time I dont believe there is any connection between the two. Why? Because the FEW most often does not exist when supercells are travelling across the area. So the FEW cant be much of a affect. Others think that supercellular storms approaching the Fort Smith area tend to have a "greater likelihood" to have rotation in them due to the FEW. This theory has no basis in fact whatsoever. Looking at reported tornadoes for the last 50 years there is no more tornadoes in Sebastian county and the Fort Smith area than any other area of land surrounding it (execpt for the expected decrease in tornadoes from west to east out of Oklahoma into Arkansas).

There is another theory about squall lines and I believe that the answer to this question is two fold. 1. Squall lines are already typically weakening when they are moving into the area. and 2. I believe there could be some misrepresentation of radar data owning to the "cone of silence". As storms approach the Fort Smith area they proceed directly over the radar located just se of Fort Smith. The radar beam cannot "look" straight up and so storms tend to look "weaker" when in fact they are not. The fact that some say storms re-intensify as they move just east of Fort Smith would seem to support this theory.

This is just a basic overview of what the FEW is and some of the questions about the FEW. I will continue to add more information to this page.

Brian Emfinger
http://www.realclearwx.com