Oh, October, you are a fickle month. After a beautiful weekend across much of the eastern two-thirds of the country, this week brings the wet remnants of a hurricane into the southwest and the risk of tornadoes to the Tennessee Valley this afternoon.
Severe Storms Snuff Stellar Seasonable Streak
A slight risk for severe weather is in place from Mississippi and Arkansas northeast through Ohio and West Virginia this afternoon. A marginal risk for severe weather exists all the way from Houston, Texas to Lake Erie for the potential of scattered reports of wind damage or hail the size of quarters.
Most people won't see awful weather today. However, the scattered nature of the storms doesn't rule anybody out—the worst weather could be confined to open farmland, or it could bubble up over major cities such as Nashville or Little Rock. The potential for thunderstorms mixed with favorable wind shear across the slight risk area will allow any storms that do develop to either organize into a squall line or even turn into supercells. Any severe storms that do form will carry the risk of damaging winds in excess of 60 MPH, but storms that grow into supercells will carry a risk for large hail (larger than a quarter) and even a few tornadoes.
A 5% risk for tornadoes exists across a swath of Tennessee and Kentucky this afternoon. That doesn't sound like much, but given that the climatological risk for tornadoes across the highest risk area on October 6 is zero, it's worth close attention. Low-level wind shear may be favorable for a tornado or two from Little Rock to Dayton, as well, but it's a low-end (2%) chance.
Simon to Drench Southwest
The remnants of Hurricane Simon, a once-powerful category four hurricane in the eastern Pacific Ocean, are set to move into the southwestern United States towards the end of this week after making landfall in Mexico on Wednesday as a tropical depression. Simon continues the trend of storms from this year's active eastern Pacific hurricane season ending up over the desert southwest.
Simon's remnants won't produce as much rain as some of the previous tropical systems the region has had to deal with this year, but heavy enough rains could cause some flooding problems in areas prone to the issue.
The Weather Prediction Center's latest rainfall forecast map over the next seven days shows up to two inches of rain falling over parts of the southwest. The moisture from Simon could merge with a stalled frontal boundary over parts of the Midwest and Ohio Valley later this week, producing a huge area of three to four (or more) inches of rain.
It looks like October's longstanding reputation for being a wild, active weather month will stand for yet another year.
[Images: NASA, author x3, WPC]