6:00 AM MDT, Tuesday, October 30, 2018
Intermittent precipitation during the day should be mainly snow above 7000 feet and mainly rain below 6000 feet, with rain changing to snow between 6000 and 7000 feet. During the late afternoon and evening northeasterly flow through a deep layer of the lower atmosphere will probably result in a period of steady precipitation changing over to snow at all elevations. Snow should end from Denver north late tonight, but may linger into morning for the Palmer Divide region and south.
Big variation can be expected from mountains to plains with this storm. Even on the plains you may not have to go very for to the east in northeastern Colorado to get little or no snow.
Above 7000 feet: 5-10 inches (locally 12″ in some areas south of I-70)
6000-7000 feet: 3-6 inches
Boulder, Broomfield, Denver (south & west suburbs), Colorado Springs: 2-4 inches
Fort Collins, Longmont, east Denver & DIA: 0-2 inches
Does it really almost always snow on Halloween?
Snow on Halloween is a reputation around here. The Boulder climate record shows that the phrase “almost always” is a bit of an exaggeration, but it’s easy to see where the snowy reputation comes from. In the last 30 years there has been measurable snow (at least 0.1 inch) five times on Halloween. But if we look at the week centered on Halloween (Oct 28-Nov 3) there has been measurable snow 16 out of the last 30 years, or 53% of the time. By comparison the 1-week periods that include Thanksgiving, Christmas, Presidents Day, and St Patrick’s Day all have about a 60% chance for measurable snow. So Halloween week does signal the ramp-up to winter season snow probability.