As we close in on the official start of winter Dec. 21, there’s little cold to be found across the Lower 48. The first of two surges of warmth has set records across Texas and parts of the South already. Dozens more records are possible Friday and Saturday, ahead of a powerful storm system triggering severe thunderstorms as it pushes east.
After only a brief break to start next week, warmth is set to build in again. By Tuesday, a new round of records is likely across the Southern Plains, expanding into the Midwest and Eastern states during the second half of the week. Some records could be set by large margins. In parts of the Midwest, temperatures could be as much as 40 degrees above normal, approaching their highest temperatures observed during December.
Current warmth
Dozens of records are slated to be tied or topped Friday and Saturday ahead of a cold front sweeping east. Friday’s record-challenging warmth is centered over the south-central United States. On Saturday, the record warmth will stretch to the East Coast with a focus on parts of the Mid-Atlantic and Northeast.
Thursday featured record highs in Houston, Brownsville and Laredo, where maximum temperatures of 87, 88 and 89 occurred, respectively.
Forecast record/near record High temperatures from today (Thurs) to next Wed for locations east of the Rockies. This week's anomalies are 20-30 above normal, while next week's are 30-40 degrees! There are more records for overnight High Minimums too: https://t.co/zXFegcnVVt pic.twitter.com/0iepH51BXJ
— NWS Weather Prediction Center (@NWSWPC) December 9, 2021
The 87-degree high at Houston’s William P. Hobby Airport was also the warmest December high temperature on record for the city, surpassing the previous monthly mark of 85, set in 1933.
Many of the same spots are likely to see record or near-record highs Friday. Oklahoma City may top its daily record of 75 from 1996. Dallas’s record of 84 could also fall. Farther east, record highs in Memphis and New Orleans are also among those at risk of falling.
Along the Texas-Mexico border region, readings may reach the sweltering low 90s in places like Laredo.
The anomalous warmth is also fueling a significant severe weather threat Friday evening into Friday night. Tornadoes, some which could be strong, are a possibility across parts of the mid-South and surrounding areas Friday night. A moderate risk, or Level 4 of 5, has been issued by the Weather Service for portions of the area.
A Moderate (4/5) Risk is now in place for portions of the Mid South this evening and overnight. A few tornadoes (some strong), damaging wind gusts, and large hail are possible mainly overnight. Please see https://t.co/QMmU4tBZDt and your local NWS office for more info. pic.twitter.com/z2KwSuhw3R
— NWS Storm Prediction Center (@NWSSPC) December 10, 2021
Warmth shifts east with the cold front into Saturday. Temperatures reaching the 60s and 70s — some 20 to 25 degrees above normal for the date — could deliver records to places such as Buffalo, Washington and New York City.
In addition to record highs, numerous record-warm low temperatures have been or will be set, including up to three or four dozen Friday night.
Round 2
With a cold front clearing the East Coast late Saturday, a few days without massive winter warmth seem likely.
It won’t last for long. Unusually toasty conditions will surge back into many of the same regions east of the continental divide early next week. By Tuesday and Wednesday, temperatures as much as 30 to 40 degrees above normal are possible across the central United States.
While next week is too far out for specifics, temperatures should rise to at least the values indicated below between Tuesday and Thursday, progressing from west to east. If anything, these forecasts may be conservative, given the anticipated strength of the wintertime heat dome. There is certainly a chance for more all-time December records in spots.
- Wichita: Lower 70s.
- Iowa City: Near 70.
- Minneapolis: Low-to-mid 60s.
- Chicago: Near or above 60.
- Memphis: 60s.
- Washington: 60s.
Why so warm?
The large-scale weather pattern has recently favored warmth across much of the Lower 48 east of the Rocky Mountains. That seems set to continue for some time.
Much of December has been dominated by a polar jet stream locked across the northern tier of the United States and into Canada. This is quite far north for the time of year, and in large part thanks to persistently higher pressure over the contiguous United States.
More recently, and into the time ahead, the weather pattern is becoming dominated by a recurring area of low pressure over the western part of the country, bringing stormy weather. To the east, like the opposite side of a seesaw, a sprawling zone of high pressure and associated warm conditions will dominate.
Both of these weather drivers are expected to be high-end versions of themselves by the middle of next week. Some forecasting has shown the next round of “subtropical” high pressure in the eastern United States to be near historic intensity for the time of year.
On top of these weather factors, human-caused climate change is helping to push unusual warmth toward extreme levels.
More of the same is expected through the winter. While colder breaks are a good bet, an overall pattern of above-normal temperatures in the East and below-normal in the Northwest is common for La Niña winters like the present.
