The 2009 Severe Weather Season Kicks Off Next Week

Two major storm systems are forecasted to impact the U.S. next week, and both will likely produce both winter precipitation in their cold sectors, as well as strong to potentially severe storms in the mild airmass ahead of them.

The first system brings heavy mountain snows to the Southwest on Saturday and Sunday, then ejects out into the central and southern Plains states on Sunday and Monday.  The return of deep, quality moisture from the Gulf of Mexico looks suspect right now, as does the level of instability, but the strength of the system will tend to overcome the lack of moisture and instability.  This system has the potential to produce a squall line of severe storms across southwest Kansas, the Texas panhandle and into western Oklahoma late Sunday afternoon and evening, with that squall line racing east and northeast and affecting parts of southern Kansas,  the remainder of Oklahoma and north Texas during the overnight hours Sunday into Monday morning.  Then a weakened line of strong to isolated severe storms will impact Missouri, Arkansas and eastern Texas on Monday.  The main threats from the storms Sunday and Monday will be damaging wind and hail.  Any tornado activity that happens will be rather isolated.

Fast on the heels of this first system is one that will move out of the Southwest and get it’s act together quickly once it emerges into the central Plains on Tuesday.  Low pressure will rapidly deepen in the Kansas or Nebraska region on Tuesday, and a richer supply of Gulf of Mexico moisture will be pulled northwward.  Greater instability in the atmosphere will also exist across the MO and MS Valley ahead of this system.  The stage is set for a potentially significant episode of strong to potentially severe storms across a large area generally along and east of the Mississippi River and south of I-80, next Wednesday and Thursday.  There would also be a major winter storm threat in the cold sector of this storm, potentailly across parts of Kansas, Nebraska, Iowa, Minnesota, Illinois, Michigan and Wisconsin.  The GFS model and the ECMWF are currently at some odds regarding the strength and track of this potential weather-maker, so it is still way too early to get into specifics until these two models come into better agreeement.  The GFS has been much stronger and farther south in its forecast, while the ECMWF has been farther north and weaker.  The ECMWF is statistially proven to be the more accurate model in this range, so if it begins to trend more toward the more dangerous solution depicted by the GFS, then the threat for the middle and end of next week will certainly gain credibility in the eyes of many forecasters, me included.  I will say that the 0z run of the ECMWF from last evening did trend a bit more toward what the GFS has been showing, but I will need to see a few more runs of the ECMWF trending this way before I accept it as legitimate.  This system definitely has *potential* to be a high-impact storm for the eastern half of the country next week, so it will be monitored closely and carefully.

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