THE HALLOWEEN BLIZZARD, AN ALL-TIME BIGGIE...
During the time I've been on this planet (more than 6 decades) I can only think of a handful of times when an October snow whitened the pumpkins in my neighborhood. Even when its happened, it was all melted in less than a day, if not hours. Let's face it October snowstorms are hard to come by.
That makes the Halloween blizzard of 1991 all the more unusual, even in a place like Minnesota where early snows are a bit more common than here in southeastern Iowa. It truly takes a perfect storm to get the cold air, moisture, and storm track in the right place to get a biggy that early. In October of 1991 it happened over much of Iowa, Minnesota, and northwest Wisconsin. In places like Duluth, Minnesota where 37" of snow fell, it's still the storm that all others are measured against no matter what time of year. Here's a recap on the Halloween blizzard from the NWS in Duluth, Minnesota.
The Halloween Blizzard of 1991:
The snowstorm that hit parts of the area starting around Halloween (October 31 - November 3) in 1991 was an impressive storm in many respects, and it is still remembered by many people across the Northland. In fact, this storm was set up, in part, by the weather patterns that caused the "Perfect Storm" that struck the East Coast of the United States, and was famously depicted in Sebastian Junger's book. Moreover, the "Perfect Storm" was beginning to wind down in the Northeast on Halloween, around the same time that Minnesota was starting to see heavy snow creeping in. To have two exceptional storms impacting the continental United States at the same time is quite rare.
During the height of trick-or-treating- the storm began as rain, then changed quickly to freezing rain and before the evening was over, it was snowing. It continued to snow for two more days, with final totals of 36.9 inches at the Duluth Airport and 45 inches in Superior. A large area of more than 20 inches of snow covered most of the northwest quarter of Wisconsin from Bayfield to River Falls and near the eastern half of Minnesota. At times the snow fell at a rate of two inches per hour and was accompanied by thunder and lightning. In addition, winds gusting to to 40 mph created huge snowdrifts and zero visibility.
At the time, the 36.9" of snow that fell at Duluth set the state record for storm total snowfall. That was surpassed in 1994.
Snow began in Duluth at about 1:00 pm on October 31st, and did not end until 1:00 pm on November 3rd, meaning that snow fell continuously on the city for about 72 hours.
Moderate to heavy snow fell in Duluth with as much as 2 inches per hour from about 11:00 am on November 1st to about 2:00 am on November 2nd - about 15 hours.
Blowing snow was reported in Duluth for 33 consecutive hours, starting at 2 PM on November 1st. Winds regularly gusted to between 30 and 40 MPH. Visibilities were frequently near zero.
The Halloween Blizzard of 1991
The "Halloween Blizzard" was made possible by a strong Arctic cold front that surged south through the central United States several days prior. On October 28, 1991, temperatures in advance of the cold front were quite pleasant as high temperatures reached into the 70s from the Mid Mississippi River Valley south into North Texas, and into the 80s across much of central and southern Texas. Meanwhile, high temperatures did not crack 20 degrees across most of Montana and Wyoming.
The contrast between the two air masses was stark, and by the morning of October 29th, the cold front was already about halfway through Texas. At 6 AM CST, the temperature in Amarillo, TX had plummeted to 22 degrees with a stiff northerly breeze. Abilene, TX was reporting a temperature of 40, while Dallas came in at 64 - a 24 degree difference over about 180 miles. Meanwhile, morning lows were much more frigid to the north - in the single digits across Montana and Wyoming, and in the teens (with snow) in the Dakotas.
A broad upper level trough, or low pressure area was in place over the western US at this time, with one particular shortwave (a disturbance, or small area of low pressure aloft) lifting northeast through the Dakotas, and another digging to the southeast into the Intermountain West. By October 30th, the cold front had reached the Texas shoreline with the Gulf of Mexico, and stalled in that location. As the shortwave aloft rounded the base of the broad trough and approached the southern Plains, it aided the development of an area of surface low pressure along the sharp temperature gradient near the Texas Gulf Coast. The development of low pressure systems along coastal fronts in this fashion is relatively common in the cool season along the Texas Gulf Coast and along the Atlantic Seaboard near the Gulf Stream current.
From October 30th into the 31st, this low pressure system slowly became better organized over Texas, before it ejected north over the Mississippi River Valley. This trajectory of a low pressure track (almost due north from the western Gulf) is climatologically favorable to produce very heavy snowfall in the winter months because it allows copius amounts of moisture to surge north where they can interact with colder air. Cooler readings lingered at the very end of October across the Upper Midwest, and a re-inforcing shot of Arctic air was just beginning to push southeast through the western Canadian Provinces.
On November 1st, the surface low pressure moved north from western Illinois into the Upper Peninsula of Michigan and the minimum pressure fell about 24 millibars in 24 hours, indicative of rapid deepening and strengthening of the cyclone. This was when the heavier snow set in across the Northland, and winds became quite gusty - producing some blizzard conditions with visibilities at or below 1/4 mile at times. Snowfall rates occasionally peaked in the 1 to 2 inches per hour range.
The low pressure eventually became occluded, weakened, and then continued to dissipate as it pushed east across northern Ontario in subsequent days. When the storm had exited, it had taken quite a toll on the area. Almost every place received at least a foot of snow, with lower totals to the west of the International Falls, Grand Rapids, and Brainerd areas as they were further away from the low, and also east of the Ashland and Hayward areas where warmer air kept snow from accumulating as much. Snow drifts were as high as 6 to 10 feet in some areas, and a few spots saw businesses and schools closed for several days.
In 1991, Halloween was no treat for many residents in parts of Iowa and Minnesota. The morning of October 31, 1991, a storm, which would eventually become known as the “Halloween Blizzard” in most of Minnesota and the “Halloween Ice Storm” in Iowa, began quickly moving northeastward through the Mississippi Valley.
The NWS in Des Moines, Iowa registered this account of the storm in my state.
1991: A major winter storm pounded the upper Midwest from October 30th into November 2nd with some of the most severe effects occurring on Halloween. Snow moved into southern Iowa on the afternoon of the 30th and changed to mixed precipitation and ice on the morning of the 31st and continuing into late afternoon on November 1st. Total ice accumulations ranged from 1 to 2 inches from southwest into north central Iowa and 2 to 3 inches across southern and southeast Minnesota. In northwest Iowa, the precipitation fell as all snow. Total snow accumulations of 8 inches or more blanketed the area with 15.0 inches falling at Estherville. Stong winds produced blizzard conditions into November 2nd. The damage and hazardous travel conditions were so severe and extensive that 52 of the 99 counties in Iowa were declared disaster areas. Highways and interstates were closed across most of the state and Halloween festivities were cancelled at many locations. As the storm system moved further northeast it dumped 36.9 inches of snow at Duluth which, at the time, was the largest storm total snowfall accumulation on record in Minnesota until it was surpassed in 1994.