NATIONAL WEATHER SUMMARY

DECEMBER 2024

1-7: An amplified polar jet stream was highlighted by a Western ridge of high pressure and an Eastern trough, cutting off moisture from reaching much of the country. Except in the western and central Gulf Coast States, where locally heavy rain fell, cool but dry weather. cold, blustery conditions across the eastern half of the U.S. were an occasional impediment to outdoor activities. Weekly temperatures averaged 10 to 15°F below normal from the middle and lower Mississippi Valley into the middle and southern Atlantic States. In fact, below normal temperatures covered nearly all areas from the eastern Plains to the Atlantic Coast.

By the morning of December 8, snow blanketed less than 18 percent of the Lower 48 States, with non-mountain coverage mostly limited to the nation’s northern tier (from North Dakota to New England). Elsewhere, warm, dry weather in southern California and the Southwest was ideal for late-season fieldwork, while some fog and air-stagnation issues plagued California’s Central Valley and some interior valleys in the Northwest. Late in the week, warm, dry weather expanded as far east as the Plains and western Corn Belt. Western weekly temperatures ranged from at least 5°F below normal in parts of Oregon and southwestern Idaho to more than 10°F above normal on the northern High Plains and adjacent Rockies. Early in the week, record-setting warmth developed in the Desert Southwest, as temperatures soared above the 80-degree mark. Phoenix, AZ, posted a daily-record high of 83°F on December 3. Elsewhere on that date, unusual warmth extended to the northern High Plains, where Livingston, MT, notched a daily-record high of 58°F. In contrast, early week maximum temperatures remained below 32°F in the central Appalachians and environs. Highs on December 3 were the lowest on record for the date in locations such as Bluefield, WV (20°F), and London, KY (26°F). In fact, Bluefield’s temperatures remained below the freezing mark on 5 consecutive days, from November 29 – December 3.

In the Atlantic Coast States, daily-record lows for December 4 dipped to 20°F in Florence, SC, and 22°F in New Bern, NC. Two days later, on the 6th, daily-record lows in Virginia plunged to 13°F in Lynchburg and 16°F in Danville. In North Carolina, New Bern (22 and 20°F) and Elizabeth City (21 and 17°F) closed the week on December 6-7 with consecutive daily-record lows. Late in the week, warmth developed across much of the western half of the U.S. By December 6, daily-record warmth in the West Coast States included highs of 87°F in Camarillo, CA, and 60°F in Bellingham, WA. The following day, record-setting highs for December 7 surged to 69°F in Rapid City, SD; 68°F in Lincoln, NE; 62°F in Waterloo, IA; 60°F in Great Falls, MT; and 59°F in Redmond, OR. With a high of 66°F on the 7th, Grand Island, NE, experienced its warmest December day since December 15, 2021, when it was 69°F. With storminess confined to a few areas, precipitation highlights were scarce.

8-14: Weekly temperatures averaged 5 to 10°F above normal across northern sections of the Rockies and High Plains, with general warmth also covering an area extending from the southern half of the Plains to the lower Mississippi Valley, and into the central Appalachians. In contrast, readings averaged at least 5°F below normal from parts of North Dakota into the upper Great Lakes States, while near-normal readings were observed in the Northeast, southern Atlantic States, and many areas west of the Rockies. With several disturbances traversing the country, temperatures regularly rose and fell, although warmth was less prominent in the Great Lakes States. As the week began, a surge of warmth across the Plains and Midwest led to daily-record highs for December 8 in Colorado Springs, CO (68°F), and Sioux City, IA (65°F). Farther south and east, daily record highs included 85°F (on the 9th) in Austin, TX, and 80°F (on the 10th) in Wilmington, NC. December 11 was a warm day in the Atlantic Coast States, with daily-record highs being set in locations such as Miami, FL (86°F); Hartford, CT (64°F); and Bangor, ME (59°F). Elsewhere in Maine, Houlton (58°F) posted a daily record-tying high for December 12. A few days later, however, a surge of cold air into the northern U.S. led to a daily-record low (-7°F on December 14) in Gaylord, MI.

15-21: Western warmth limited significant snow accumulations to high-elevation sites in northern California and the Northwest. Western snowpack continued to languish in several areas, including much of the Southwest and the eastern slopes of the northern Rockies. Concurrently, warmth was prevalent across the West and the High Plains, as well as the western Gulf Coast region. In fact, weekly temperatures averaged at least 10°F above normal in many locations from southern and eastern Texas into the lower Mississippi Valley, and throughout the High Plains. In contrast, temperatures averaged slightly below normal in the north-central U.S., from northeastern northern Minnesota. Montana into Early-week warmth was focused across the western Gulf Coast region, where Victoria, TX, tallied a trio of daily-record highs (86°F each day) from December 15-17. The last time a warmer December day occurred in Victoria was December 25, 1964, with a high of 88°F. Unusual warmth extended eastward across the Deep South, with daily-record highs reaching 81°F in Louisiana locations such as Baton Rouge (on the 15th) and Lake Charles (on the 16th). On December 17 in Florida, daily-record highs surged to 87°F in Punta Gorda and 86°F in Ruskin. During the mid- to late-week period, an expansive area of record-setting warmth stretched from the Pacific Coast to the High Plains. In southern California, daily-record highs for December 18 rose to 86°F in Anaheim, Camarillo, Escondido, and Woodland Hills. Elsewhere in California, Palm Springs logged three consecutive daily records (85, 85, and 82°F) from December 18-20. Warmth also extended into the Great Basin and Northwest, where consecutive daily-record highs occurred on December 19-20 in locations such as Astoria, OR (61 and 64°F, respectively), and Tonopah, NV (61°F both days). Astoria’s reading of 64°F also tied a monthly record originally set on December 26, 1980. Finally, consistent Southwestern warmth pushed the maximum temperature in Phoenix, AZ, to 83°F from December 18 20, breaking a record each day. Phoenix has already set a station record with 4 December days reaching 83°F or higher; the previous record of 3 such days had been set in 1939. Similarly, Tucson, AZ, tied a 1939 record with 8 days of 80-degree warmth in December, including 5 in a row from the 18th through the 22nd. Tucson also registered four consecutive daily-record highs (82, 82, 82, and 83°F) from December 18-21. In contrast, a late-week cold blast sweeping across the Midwest led to consecutive daily-record lows (-15 and -21°F, respectively) in Gaylord, MI, on December 21 and 22. Gaylord’s lows both occurred on the night of December 21-22, with the reading of -15°F being reported just before midnight. Northwestern precipitation was particularly heavy during the first half of the week.

22-28: An ongoing Pacific storm train kept active weather in place across northern California and the Northwest, with the average water equivalency of the Sierra Nevada snowpack increasing to 10.5 inches, about 115 percent of the late-December average, according to the California Department of Resources.

Several rounds of showers and thunderstorms swept across areas from eastern Texas into the mid South, lower Midwest, and Southeast. Wintry precipitation, such as snow and freezing rain, was scarce and limited to parts of the Corn Belt and Northeast. From December 26-29, back-to-back outbreaks of severe weather from eastern Texas into Southeast spawned several dozen tornadoes and resulted in numerous reports of wind damage. Concurrently, much of the country basked in winter warmth, although chilly conditions lingered along and near the Atlantic Coast. Weekly temperatures averaged 10 to 20°F above normal in a vast area stretching from the northern Great Basin to the northern and central Rockies, then eastward across large sections of the Plains and Midwest. A separate area of record-setting warmth covered the western Gulf Coast region. In contrast, significantly below-normal temperatures prevailed in the Atlantic Coast States, from Georgia northward. Weekly readings averaged at least 10°F below normal in parts of New England and eastern New York. Consistent warmth nearly nationwide kept snow cover at a minimum, except across the nation’s northern tier and higher elevations of the western U.S. At daybreak on December 25, barely one-quarter (26 percent) of the Lower 48 States had snow on the ground, with that value falling to 19 percent just 4 days later. As the week began, however, frigid air gripped the Great Lakes and Northeastern States, with Gaylord, MI, posting a daily-record low of -21°F on December 22. The following day, record-setting lows for December 23 in Pennsylvania included -9°F in Mount Pocono and -2°F in Scranton. Farther west, warm weather spanned most areas from the Pacific Coast to the Plains. December 22 featured daily-record highs in Nebraska locations such as McCook (73°F) and North Platte (71°F). On the same date, Nogales, AZ, notched a daily record high of 80°F. On December 23 in California, daily-record highs surged to 78°F in Campo and 74°F in San Jose. Arizona also remained quite warm, with record-setting highs for December 24 soaring to 79°F in Tucson and 78°F in Douglas. During the second half of the week, warmth intensified across the western Gulf Coast region. In Deep South Texas, McAllen (89 and 91°F, respectively) and Brownsville (85 and 90°F) both logged daily-record highs on December 26 and 28. Other daily-record highs in Texas on the 28th included 87°F in Corpus Christi, 85°F in Victoria, and 83°F in San Antonio. Late-week warmth also spread across the Plains and Midwest, with daily-record highs occurring on December 27 in locations such as Pierre, SD (54°F), and Ashland, WI (45°F).  The next day, record-setting highs for the 28th reached 48°F in St. Cloud, MN, and 51°F in Sisseton, SD. 

 

Jim G. Munley, jr.
http://www.jimmunleywx.com