Early snow hits north-central USA

Advertisment
  • A handy form of transport for the early snowfall in north-central USA, which has seen unknown numbers of stranded motorists. Credit: David Cheskin/PA.

    Modeled snow depths (cm) at midday on Saturday 5th October 2013.

    A graphic illustrating the projected path and winds of Tropical Storm Karen, produced using our MeteoEarth app.

  • Early snow hits north-central USA
    05.10.2013 13:56

     

    Whilst much of the UK basks in higher than average temperatures this weekend, it seems that winter has arrived (well, at least temporarily) in parts of north-central USA. 

    Although by no means out of the question, snowfall in early October is uncommon across these parts of the USA. This is especially the case this week, when more than three feet of snow was locally dumped within a large affected region stretching from the eastern Rocky Mountains to the north-central Great Plains. The Black Hills area, which straddles north-east Wyoming and south-west South Dakota, was notably hit by Friday’s snowstorm, with nearly 400 miles of the main Interstate 90 subsequently closed to traffic. The snow also left motorists stranded and homes without power, although it wasn’t just the snow causing problems – strong winds and thunderstorms were also a concern, and even a handful of tornadoes were reported. 

    So what caused all this wintry weather?

    Prior to the snow, there was relatively warm air over the affected area. Building high pressure over south-west Canada together with low pressure in central USA helped to steer colder air down from Canada. As a front sank south-eastwards across north-central states, the frontal precipitation fell as snow in the newly arrived cold air. As low pressure pushed north-eastwards towards the Midwest, added instability helped to spark thunderstorms and tornadoes.

    Will the snow last?

    The lying snow may lie for a while, yes, although no fresh snowfall is forecast for a time. The accompanying graphic of modelled snow depths shows the expected conditions at midday on Saturday (the time of writing). Some of the more substantial totals may prove slow to shift; however on a whole this white zone will shrink and snow depths will decrease over the coming days as more settled conditions dominate.

    What about elsewhere in the USA?

    Although this wintry interlude is set to fade away, other parts of the USA are under a watchful eye for interesting weather. A far cry from the snow-white conditions over the north-central states, parts of southern California are currently under threat from wildfires, following a prolonged period of Santa Ana winds (very dry and strong downslope winds common at this time of year). Meanwhile, Tropical Storm Karen, the first of the hurricane season set to strike the south-east US, has seen locals prepare for strong winds, heavy rain and storm surges through this weekend and into Monday.

    By: Laura Caldwell