It is too soon to say exactly how hot temperatures will be, but initial indications are that the central United States may face some of the country’s hottest weather with respect to normal. Record heat is certainly a possibility, although exactly how many records fall and where won’t come into focus for several more days.
The worst of the heat wave may still be seven to nine days away. Forecasts this far into future carry with them substantial uncertainty, although confidence that a significant event is likely is boosted in this case due to forecast model agreement.
The source of the predicted heat dome is the desert Southwest. By early next week, the dome will shift into the southern plains. It is forecast to reach maturity by the middle and latter parts of next week when it may sprawl from the Rockies to the Appalachians.
Between Thursday and Saturday of next week, while much of the country is forecast to be hotter than normal, the biggest heat anomalies are predicted from the central United States to the Upper Midwest. In these locations, temperatures may be 10 to 20 degrees above average.
Oklahoma City, St. Louis, Minneapolis, Chicago, Milwaukee, Des Moines and Kansas City, Mo., are some of the cities that may be hardest hit.
The average of a group simulations of the GFS model (the GEFS ensemble) predicts highs in Des Moines to exceed 100 degrees on three straight days.
The major forecast models suggest the intensity of the heat dome, at its core, may near rare thresholds.
“Both the European and GFS models, among others, are depicting the height of the 500 millibar pressure surface, which is normally located around 5,000 meters, or 18,000 feet, to be at or above 6,000 meters, or 19,685 feet,” writes Mashable’s Andrew Freedman. “[T]hat is an indication that this event may be unusually severe.”