The Storm Prediction Center's current assessment of areas facing a moderate risk of severe weather, including possible long-track tornadoes. This graphic is valid through 11 Apr/1200Z. For updates--and more information--visit their website,
Much of the Mid-South and Middle Mississippi Valley is under the gun for severe weather over the next 18 hours, as a powerful storm moves out of the Great Plains.
As the weather system churns east, it is expected to produce a large number of tornadoes, including violent, long-track twisters. Meteorologists at Accu-Weather have backed off a bit on their original predictions, which suggested that the storm might rival the "Super Outbreak" of 1974, which produced 149 tornadoes in a 24-hour period.
However, both private forecasting services (like Accu-Weather) and the National Weather Service's Storm Prediction Center (SPC) still expect numerous tornado warnings before the end of the day. Accu-Weather's severe weather expert, Henry Margusity, believes the greatest risk of tornadoes will exist from eastern Arkansas to central Illinois, as the storm gathers more strength. From his latest weather blog entry:
As we go through the day, the jet regions become important in regards to where severe weather will develop. I pulled the moderate impact area west into eastern Kansas and eastern Oklahoma where a line of storms will develop in the notch of the low pressure. That area will get large hail, wind damage and some quick hitting tornadoes as the left exit region of the jet comes over that area. The line of storms will move into western Missouri later this evening.
The next area will cover the Mississippi Valley where the right entrance region of the jet will support an increase in thunderstorms and supercell storms later today into tonight. The highest risk of large tornadoes associated with the supercells will be from central Illinois through eastern Arkansas, western Tennessee into northern Mississippi. It may take a good part of the day for things to get going, but once the storms do get going, numerous tornado warnings will be issued I believe.
Similar thoughts from the forecast team at the SPC:
"THE COMBINATION OF INCREASINGLY WARM AND HUMID AIR WITH VERY STRONG ENVIRONMENTAL WINDS THAT CHANGE DIRECTION WITH HEIGHT WILL CREATE A FAVORABLE SETUP FOR LONG-LIVED ROTATING THUNDERSTORMS. SOME OF THESE SUPERCELL STORMS WILL CONTINUE EAST AND NORTH INTO ARKANSAS...SOUTHERN MISSOURI AND NORTHERN LOUISIANA FROM OVERNIGHT ACTIVITY IN TEXAS AND OKLAHOMA. OTHER STORMS LIKELY WILL FORM LATER THIS AFTERNOON THROUGH TONIGHT ACROSS PARTS OF MISSISSIPPI ...TENNESSEE...KENTUCKY...ILLINOIS AND INDIANA. A FEW OF THE STORMS WILL BE CAPABLE OF PRODUCING STRONG AND POSSIBLY LONG-LIVED TORNADOES...IN ADDITION TO DAMAGING WINDS AND LARGE HAIL."
The prediction center has already posted a "moderate risk" area across portions of eastern Arkansas, western Tennessee, northern Mississippi, southeast Missouri and southern Illinois. With daytime heating, favorable jet stream conditions and moisture surging northward from the Gulf of Mexico, the threat of severe weather in these areas will likely increase during the afternoon and early evening hours. As Henry Margusity observed in his blog:
"This is not the type of day where you go about you normal business. It's a day where you need to be alert and ready to move to a safe location if tornado warnings are issued for your area."