It’s becoming a broken record. Once more, a nasty mix of atmospheric ingredients are converging in parts of the Plains and Midwest, setting the stage for the latest round of violent severe weather late this afternoon and evening.
The National Weather Service’s Storm Prediction Center says there is a “moderate” risk for severe thunderstorms and perhaps large tornadoes in a zone that includes Oklahoma City, Norman, Okla. and Joplin, Miss:
SCATTERED STORMS WILL FORM ALONG A DRYLINE OVER PARTS OF CENTRAL OKLAHOMA BETWEEN 4 AND 7 PM. THESE STORMS WILL BECOME RAPIDLY SEVERE AND BE CAPABLE OF PRODUCING A FEW STRONG TO VIOLENT TORNADOES…SCATTERED VERY LARGE HAIL ABOVE BASEBALL SIZE AND ISOLATED SEVERE WIND GUSTS ABOVE 60 MPH.
A rare “particularly dangerous situation” tornado watch has been issued for a large chunk of central Oklahoma (through midnight central time) where violent storms are expected to erupt after 4 p.m. central time.
Surrounding this area of elevated severe thunderstorm risk, a larger area stretching from north Texas into southern Wisconsin and Michigan may also contend with dangerous storms, though the risk is somewhat less. This area includes Kansas City, Chicago, Milwaukee, and Detroit.
The National Weather Service forecast office in Norman, Okla., responsible for forecasts and warnings in central Oklahoma, has been sounding the alarm bell dispatching an onslaught of preparedness messages on Twitter.
— NWS Norman (@NWSNorman) May 31, 2013
Residents of the Plains are becoming ever accustomed to hearing this storm readiness advice. Remarkably, in nine of the last 14 days, SPC has posted moderate risk outlooks for severe weather in parts of the region spanning Texas through Nebraska – an unheard of frequency.
The reason for the repeated episodes of violent weather is a stagnant configuration of high altitudes winds or jet stream. In between a persistent dip in the jet stream over the Rockies and ridge in the jet stream over the East, a volatile transition zone has set up in the Plains – where multiple streams of air keep colliding.
The good news is that dip in the jet stream over the Rockies will lift out tomorrow, finally bringing a more tranquil weather pattern to the Plains.