In my last post I discussed how a ridge would build across the central U.S. Thursday and Friday in response to a deepening trough over the western United States. As often happens this time of year, the downstream polar vortex that has brought the unseasonably chilly weather to much of the north-central U.S. over the past two weeks has become closed off aloft, which has resulted in an Omega blocking pattern that has delayed our warm-up.
The Thursday afternoon GFS shows just how blocky this pattern is as three closed off upper level features can be seen on the map. A slow-moving warm front over the south-central United States has triggered severe thunderstorms this afternoon and shows how far away our long-awaited warm air remains. The northwest flow from Thursday will gradually become westerly Friday and Saturday before the real warm air arrives for Sunday – Tuesday. Monday should be the warmest day but the warm air will not stick around for long because as the polar vortex over the western United States lifts out over the weekend the upper-level flow will become zonal and allow a cold front to bring more seasonable temperatures to the Mid-South for midweek.
The big question is will any location in the Mid-South hit 90 degrees for the first time this year? The best chance will occur in southwest TN (Memphis), which has already hit 88 this year. Even though this air mass hit 110 degrees in Phoenix a few days ago, I think there will be enough soil moisture around to keep highs in the middle to upper 80s for most of the Mid-South.
