Chilly Arctic air has settled in for most of the lower 48 for late November, bringing widespread heavy snow and wind across the Rockies, Plains, and Midwest. Many places along the Eastern Great Lakes saw significant lake-effect snow, totaling 1-2 feet in some areas in western New York, and cities such as Withita and Kansas City saw record one day snowfall amounts, picking up nearly a foot of snow. The first major cold snap of the season even hit the deep south, bringing the first freeze of the season to North Florida and the Gulf Coast, and dropping temperatures into the 20s and upper 10s across the interior southeast. Does this mean a colder than average December? Stemify’s December Temperature Outlook has a look ahead.
Overall, most of the U.S. should expect a mild to warm December, with frequent ridging across the entire U.S. The Northern Great Lakes and Upper Midwest should expect temperatures most above average while the Southeast Gulf and Southern Arizona will likely see near average temperatures associated with wetter conditions amplified by the Subtropical Jet Stream. With the Polar Jet Stream locked into Canada, arctic outbreaks associated with the Arctic Oscillation will be less frequent, but occasional cold snaps will be possible, particularly across the Eastern U.S. This is often the pattern of a typical El Niño Winter, but as the El Niño continues to strengthen, the overall pattern could change into the start of 2024.
Disclaimer: These outlooks are only used for generic purposes and simply depict trends overtime, not day-by-day forecasts. Errors are possible in these outlooks due to the high amount of uncertainty of forecasting months in advance. Most data is obtained from Tropical Tidbits.
Although the start of winter is still far away, it is never too early to start looking at some indications of what the upcoming winter might bring. A notable development from the spring into the summer of 2023 was the formation of an El Niño pattern, which is a major change from the La Niña pattern that has dominated the globe for the past few years. An El Niño pattern typically favors above average sea surface temperature anomalies in the Equatorial Eastern Pacific, around the Galapagos islands, which in general leads to more thunderstorm activity and less nutrient-rich waters. The warmer these waters are, the stronger the El Niño tends to be, currently, the El Niño is considered to be a weak El Niño.
The general pattern for an El Nino features the Pacific Jet cutting across the southern tier of the U.S. providing frequent storm activity and generally cooler conditions, while much of the northern tier experiences warmer than average temperatures with the lack of frequent storms. The Ohio Valley also tends to be drier than normal away from the active jetstream track to the south.
However, the El Nino is already in a weak phase, and is expected to intensify as winter approaches, with the NOAA providing roughly 90% probabilities of the formation of a Moderate to Strong El Nino by the winter of 2023-2024. Many forecast guidance models support this understanding with the continued increase in SST temperature anomalies in the Eastern Pacific.
With the high chance of development of a moderate to strong El Nino by the Winter of 2023-2024, it is not only important to examine long range forecasts, such as those provided by the NMME, CanSIPS, and CFS, but also look at historical climatology for weak and moderate-strong El Nino episodes. Weak El Nino’s historically from December to March tend to favor below average temperatures for the Eastern two thirds of the U.S., while moderate to strong El Nino’s tend to favor below average temperatures across the Southern tier, and above average temperatures across the Northern tier. Precipitation from weak El Nino’s tends to be below normal for the Southeast, Midwest and Southern Plains, while above average precipitation is favored for the West Coast. Precipitation from moderate to strong El Nino’s tends to favor above average precipitation for the South, East Coast, and immediate West Coast, and below average precipitation for the Ohio Valley and parts of the Northwest.
With all this taken together, Stemify has created a preliminary 2023-2024 outlook for both temperature and precipitation. Overall, below normal temperatures are expected for the Southeast, Southern Plains and into parts of the lower Ohio Valley, while above normal temperatures will extend widely across the Northern tier, particularly across the Upper Great Lakes, Northwest, Upper New England, and Alaska. In terms of precipitation, above normal precipitation is expected along the Gulf Coast and East Coast, with the bullseye targeting portions of North Florida and South Georgia. Below normal precipitation is expected across the Northwest.
Images created by Navam Arora
Disclaimer: The Climate Prediction Center also creates similar seasonal outlooks but this outlook is not solely based on that of the CPC, the CPC outlook can be foundhere. These outlooks are only used for generic purposes and simply depict trends overtime, not day-by-day forecasts. Errors are possible in these outlooks due to the high amount of uncertainty of forecasting months in advance. Most data is obtained fromTropical Tidbits.
As record-breaking summer heat continues across much of the lower 48, August does not appear to bring much relief. Much of the interior of the country should expect temperatures to be solidly above average for the duration of the month, with the northern plains potentially seeing temperatures several degrees above normal. Wetter conditions in the northeast should keep temperatures around average for August while coastal sections of the southeast and the west coast should expect near average to marginally above average temperatures. The trend for warmer conditions in northern Alaska should continue for the rest of summer and into the fall, while Hawaii should continue to expect average temperatures for the duration.
Disclaimer: These outlooks are only used for generic purposes and simply depict trends overtime, not day-by-day forecasts. Errors are possible in these outlooks due to the high amount of uncertainty of forecasting months in advance. Most data is obtained fromTropical Tidbits.
(Image by the SPC, visit the SPCfor more information)
Severe thunderstorms producing large hail, damaging winds, and some tornadoes are possible across much of the central plains this afternoon and evening, with the greatest risk extending Eastern Colorado into Western Kansas and far Northwest Oklahoma. High levels of low-level moisture already present in the region combined with instability from daytime heating will promote rapid supercell development on the eastern plains of Colorado. Some Supercells may produce hailstones greater than 3 inches in diameter, and occasional damaging wind gusts. High levels of windshear will be present across portions of Eastern Colorado which may aid in some tornadic development. As these storms push east, they will become more linear in nature promoting a strong damaging wind event particularly into Kansas and Oklahoma. Strong mid-level winds will enhance this damaging wind threat.
Clusters of thunderstorms could develop in the high plains and northern Rockies as a trough enters the region, some of these storms could produce large hail, occasional damaging wind gusts, and an isolated tornado. A lack of shear will likely limit tornadic development, but an isolated tornado remains possible with support from strong mid-level winds.
Further southeast, the Arklatex region may also see strong to severe storms result from clusters moving southeast from Oklahoma, although daytime heating and Instability will be very high, very weak shear and mid-level support will likely inhibit widespread severe thunderstorm development. An isolated cell with damaging wind gusts will be the main threat for this region. Probabilities for prominent severe weather hazards are given below (the dashed area represent a significant severe risk):
Hail. (Image by the SPC, visit the SPCfor more information)Wind. (Image by the SPC, visit the SPCfor more information)Tornado. (Image by the SPC, visit the SPCfor more information)
As the Summer heat and violent storms continue to rage across the US, some are already looking ahead to what Autumn may bring, and for many, it may not be much of a relief. Most of the country is forecasted to experience above average temperatures for most of fall, with cooler periods arriving in November as an El Nino setup continues to strengthen in the Eastern Pacific. Areas in the Great Lakes and the northern tier should expect temperatures to be most above average during the 3 month period. Many in the Northwest and Hawaii could also expect to see drought conditions develop during the fall months, as there is a strong indication of below average precipitation. Areas along the gulf coast and central plains could experience slightly wetter than average conditions while the four corners could see slightly drier than average conditions. An outlook for the Winter of 2023-2024 will be released in the coming months.
Disclaimer: The Climate Prediction Center also creates similar seasonal outlooks but this outlook is not solely based on that of the CPC, the CPC outlook can be found here. These outlooks are only used for generic purposes and simply depict trends overtime, not day-by-day forecasts. Errors are possible in these outlooks due to the high amount of uncertainty of forecasting months in advance. Most data is obtained from Tropical Tidbits.
