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The atmosphere across the eastern half of the country is undergoing a harsh correction, trading record-breaking heat for a bone-dry arctic chill in less than 48 hours. As temperatures plummet by as much as 30 degrees, a dangerous combination of biting winds and plummeting humidity is turning the landscape into a tinderbox.
Fire Weather Warnings have already been issued for nearly 50 million people across nearly 20 states.
The same cold front responsible for Thursday’s severe weather and the temporary end of historic heat in the Plains and Southeast is continuing to sink south.
Temperatures on Saturday will be 20-30 degrees colder than the previous day across the Carolinas, Georgia and north Florida.
To the west, temperatures will be 10-20 degrees colder than Friday from Alabama toward south Texas. And in the north, cities like St. Louis, Indianapolis and Philadelphia will be waking up below freezing just two days after being in the 70s, 80s and 90s.
Originating from polar regions, this cooler air mass is exceptionally dry, causing humidity to drop into the teens across a large portion of the country. While the dry air is significant on its own, the combination of the dryness with strong winds creates a dangerous potential for the spread of wildfire.
The winds are driven by an area of high pressure building behind the cold front.
HISTORIC HEAT WAVE EXPANDS INTO CENTRAL US AFTER WEEKS OF RECORD HEAT IN THE SOUTHWEST
On Saturday, this seasonably strong high will settle over the southern Great Lakes, and the pressure gradient will tighten over a relatively short distance, generating stiff breezes, causing the fire threat to intensify across the Southeast and the Plains.
In the Southeast, humidity will drop as low as 20%, especially across parts of South Carolina, southern Georgia and north Florida. Sustained winds will reach 10-20 mph with higher gusts.
Fire Weather Warnings span from western North Carolina through Louisiana, including parts of the Florida panhandle, with a Fire Weather Watch issued for parts of east Texas.
Relief from these threats is not far off. Increasing moisture will diminish the fire threat east of the Mississippi River on Sunday.
Across the Plains, however, lingering danger will persist. The pressure gradient will fuel a low-level jet, yielding strong southerly winds of 20-30 mph, with gusts reaching up to 45 mph. Combined with humidity levels between 15-20%, the winds will allow any new ignitions to spread rapidly.
The critical zone includes much of Nebraska, including areas recently scorched by the historic Morrill Fire, which is now contained after burning more than 640,000 acres.
Fire Weather Warnings in the Plains span from as far north as Minnesota down to the northernmost tip of Texas, and as far west as Wyoming over some western counties in Illinois.
