Heat before the Snow

As Pacific storm systems move west to east across the U.S., a southerly flow develops ahead of the cold front.  In the central and eastern States, this flow draws warm, humid air up from the Gulf of Mexico, fueling rain and/or snow as the storm arrives.

Here along the Colorado Front Range, well west of the Gulf of Mexico, the southerly winds bring warm, dry air up from the Desert Southwest; downsloping winds east of the Continental Divide further heat and dry the air, often producing summer-like warmth in the middle of winter.  Today, we reached a near-record high of 67 degrees F as the front approaches from the Great Basin.

Once the cold front crosses our region, expected to occur by tomorrow afternoon, the winds shift from the north and the temperature plummets.  Depending upon the latitude of the central low, we may receive upsloping northeast winds, pulling in moisture from the Great Plains and leading to significant snow accumulation.  For Metro Denver, such an upslope snowstorm is most likely to develop when the central low moves long the Colorado-New Mexico line; currently, the forecast indicates that the storm will follow that pattern and snow is expected to develop by the early morning hours on Sunday.  Since the storm system is forecast to move rapidly to the northeast, our snow accumulation will likely be modest (though we could use a foot or more).