It’s beginning to feel a lot more like early winter across most of the United States after the warmest autumn on record
. Several lobes of low pressure in the middle atmosphere, beneath the stratospheric polar vortex, have been swinging across the Midwest and Northeast U.S. These lobes are pushing large masses of Arctic surface air southward across the bulk of the nation in a series of pulses, with only limited relief in between. Even the worst of the cold doesn’t look like it will be truly historic at ground level. Still, some places will see their most frigid December conditions in several years. Cold and snow don’t have to be record-shattering in December to pack a noticeable punch.Figure 1.
A lone runner makes his way through Eagle Creek Park in Indianapolis, IN, as snow falls on Tuesday, Dec. 13, 2016. Image credit: AP Photo/Darron Cummings.Figure 2.
Extremely cold air in the middle atmosphere was pooled in central Canada, as shown by the light colors on this depiction of the height of the 500-mb surface (about midway up through the atmosphere). Values on the right-hand side are shown in tens of meters. Contours of surface air pressure (in black) show high pressure dominating the central U.S. Image credit: tropicaltidbits.com
.A week of wintry pulses
The latest phase of the cold wave was sweeping from the Midwest into the southern and eastern U.S. on Wednesday. Temperatures at midday were hovering a few degrees on either side of 0°F across most of Minnesota and the Dakotas. Strong northwest winds will push bitter cold across the East Coast corridor from Washington to Boston by Thursday, with temperatures tamped below freezing for at least a couple of days. Very light snow is possible for a few hours Wednesday night into Thursday
, with another dose of wintry precipitation late Friday into Saturday. That round could have significant impacts for a few hours, as it falls onto already-cold road surfaces, until warmer air brings a transition from snow, sleet, and/or freezing rain to rain later Saturday. Capital Weather Gang warned of the potential for “an icy mess”
on Saturday morning in the D.C. area.
Meanwhile, the next Arctic blast will push more frigid air into the central U.S., with a shield of light to moderate snow from the northern and central Rockies and Plains into the Upper Midwest. Denver may not get much above 0°F on Saturday, and single-digit lows could extend as far south as St. Louis, MO, on Sunday. Along the front, a band of thunderstorms is expected to drop a welcome 1” - 3” of rain across drought-hammered parts of the South, including northern Alabama and eastern Tennessee.Figure 3.
Winter weather alerts for the Great Lakes region as of Wednesday morning, December 14, 2016. Image credit: weather.com
.Lake effect machine kicks into overdrive
The most noteworthy snow this week will be in areas familiar to it: the lake-effect snow belts of the Great Lakes. Strong westerly winds associated with this week’s Arctic blasts will be passing over waters that have been unusually warm
for this time of year (2°F to 4°F above average
), leading to very unstable conditions that will favor snow-band formation. Areas in and near Buffalo, NY, and Cleveland, OH, could see periods of heavy snow with near-zero visibility
on Wednesday into Thursday, although weather.com notes that the heaviest amounts may stay just south and east of Cleveland and Buffalo
. (See embedded radar loop at bottom.)Still more record highs than lows for December thus far
Largely because winter warmth is a welcome arrival to many, record highs in winter don’t grab the same attention as record lows. This week has already seen quite balmy conditions across the Gulf Coast and Southeast, and the region will see a brief recovery in temperatures over the weekend in between cold blasts. Monday’s high of 81°F was the warmest December day on record
in Galveston, TX, in data going back to 1873. On the national scale, this warmth has actually been more exceptional than the cold observed further north. According to preliminary data from NOAA
, the first few days of December (Dec. 1 - 12) saw 104 daily record highs in the U.S., but only 67 daily record lows. That ratio will tighten or even flip over the next few days, but don’t expect anything as out-of-whack as the 48-to-1 ratio
of U.S. daily record highs to lows that occurred in November.Figure 4.
Strong northerly flow in mid-levels of the atmosphere (shown by white arrows) pushed very cold air southward at 18Z (1:00 pm EST) on December 23, 1983, near the peak of the great December 1983 cold wave. Red colors in the north-central U.S. denote the coldest air at 850 mb, about a mile above sea level. Yellow contours show the height (in decameters) of the 500-mb surface, near the vertical midpoint of the atmosphere. Image credit: National Weather Service/Dodge City, KS
.Echoes of a colossal December cold wave
We haven’t seen anything in recent decades like the truly historic cold wave that struck in December 1983. As noted by Eric Fisher (WBZ/Boston)
and Angela Fritz (Capital Weather Gang)
, that memorable blast happened to follow the “super” 1982-83 El Niño event, which was roughly as strong as last winter’s 2015-16 El Niño event. The other comparably strong El Niño was in 1997-98; the following December (1998) ended up among the warmer Decembers in U.S. weather history
but still produced some intense regional cold toward month’s end. In all three cases
, the Pacific had swung from a very strong El Niño state into weak to moderate La Niña conditions by December.
Archives kept by meteorologist Guy Walton show that December 1983 produced a phenomenal 14,482 daily record lows and only 676 record highs. On December 24, barometric pressure (converted to sea-level equivalent) reached 1064 mb (31.42”) in Miles City, MT, the highest surface pressure on record for the contiguous U.S. according to WU weather historian Christopher Burt
. Temperatures in mid- to late December 1983 plummeted to extreme values almost everywhere east of the Rockies, especially across the central third of the country. At Sioux Falls, SD, readings dipped below 0°F on December 16 and didn’t rise above zero again until December 25. Christmas Eve (December 24) brought a low of -25°F in Chicago, with wind gusts up to 41 mph. Christmas morning (December 25) saw low temperatures dip to 0°F as far southeast as Little Rock, AR, with a high of just 12°F
. Even Tampa, FL, only reached a Christmas Day high of 38°F, as noted by weather.com’s Jon Erdman in a roundup of great American cold waves
The average temperature for December 1983 in Minneapolis was 3.7°F, the coldest for any December on record. The upcoming weekend will be a rough one in the Twin Cities, with a low of around -15°F expected Saturday night and a high of just -5°F on Sunday. Neither would be a record, though: Minneapolis dipped to -24°F on December 18, 1983 (and -29°F the next night), with a high on the 18th of just -11°F. Other potential records and close-but-no-cigar forecasts:Albany, NY,
Fri. 12/16: forecast low -1°F (daily record -11°F, 1917)Boston, MA,
Fri. 12/16: forecast low 6°F (daily record 1°F, 1883)International Falls, MN,
Sun. 12/18: forecast low -22°F (daily record -36°F, 1983)Detroit, MI,
Mon. 12/19: forecast low -6°F (daily record -6°F, 1884)Louisville, KY,
Mon. 12/19: forecast low 15°F (daily record -5°F, 1884)
We’ll be back with a new post by Friday at the latest.
Bob Henson Sea level pressures near the peak of the December 1983 cold wave, as mapped by the North American Regional Reanalysis. Image credit: Greg Carbin, NOAA.