Severe Weather Outbreak, Including Threat For Tornadoes, In the Midwest, Plains Wednesday

November 7,2015

Despite the mid-November date on your calendar, a severe weather outbreak, including the threat of tornadoes, may target parts of the Plains and Midwest the middle of this upcoming week.
A powerful southward dip in the jet stream, which had earlier spun up an impressive storm over Alaska's Aleutian Islands, is expected to swing out of the Desert Southwest Tuesday and punch east into the Plains and Midwest Wednesday.

The meteorological ingredients in play for Wednesday's severe weather threat.

Ahead of this jet stream dip, warmer, more humid air in the lower levels of the atmosphere will flow northward into the Plains from the western Gulf of Mexico as strong low pressure forms to the east of the Rocky Mountains.
The resultant wind shear and instability from the strong jet stream and colder air aloft overlapping warm, humid air near the surface should give rise to severe thunderstorms.
As with virtually all severe weather forecasts several days out, there are uncertainties. In this case, it pertains to the magnitude of the tornado threat.

• Scenario 1: If the intense jet stream dip punches out in more west to east fashion, and the air mass in the Plains becomes particularly warm and humid, that would favor more tornadic supercells.
   
• Scenario 2: If, however, the jet stream dip hangs back to the west and only slowly lumbers out into the Plains, or slides more to the northeast than punching east, over a not-so-warm and humid air mass, then the tornado threat would be less.

(MORE: Where November Tornadoes Are Most Common)
Regardless of the tornado threat, damaging thunderstorms winds and large hail appear to be likely. We expect the areal coverage and number of severe weather reports to be far greater than we saw this past week.
Here is our latest forecast thinking.

Severe Weather Forecast

Wednesday's Thunderstorm Forecast

•  Tuesday night: A few strong to severe thunderstorms may break out overnight in the Plains from Nebraska to north Texas.
   
• Wednesday: The most active day with severe thunderstorms and tornadoes possible from parts of the central and southern Plains to the Upper and mid-Mississippi Valley, or from parts of Texas to Iowa or southern Minnesota.
   
• Thursday: The jet stream disturbance will blast east, but near-surface air in the Great Lakes, Appalachians, and Northeast may only be marginally warm and humid. However, thunderstorms with damaging straight-line winds are certainly possible in these areas. 

For specific tornado threat forecasts, check out the latest TOR:CON forecasts from severe weather expert, Dr. Greg Forbes.
(MORE: View National Interactive Radar Map | Difference Between a Watch and a Warning)
Severe weather and tornado outbreaks are not unusual in November. In fact, November is a climatological "second season" of severe weather, not simply in the Deep South but, occasionally, in parts of the Midwest.
Almost two years ago, an outbreak of 72 tornadoes raked through parts of seven states, including a pair of EF4 tornadoes in Washington, Illinois, and near New Minden, Illinois.
This outlook is subject to change in the days ahead. Check back with us at weather.com for the latest on this potential severe weather event.

PHOTOS: Tornadoes, Flooding in the South (Late Oct. 2015)