The cold has arrived, and it will stick with us for several days in what will be one of the areas coldest streaks of weather in recorded history for October. Here's a look at temperatures across the region as of 7 am Sunday. For many, this is as warm as it'll be until at least Thursday.
GFS MOS guidance is COLD. Even colder than we are over the next few days for Denver... It's got a high of 29°F on Monday, 17°F on Tuesday, and 16°F on Wednesday before climbing into the mid-30s for Halloween. Overnight lows are likely to dip into the single digits on Wednesday and Thursday morning for many locations across Northeast Colorado:
Using our current forecast high for Monday of 29°F as our benchmark, and assuming we don't make it above that until Thursday, how does that compare to other cold outbreaks on record?
If we look at the Stapleton location, with records back to 1948, and find all consecutive days of four our more where the temperature doesn't climb above 29°F, we see there are quite a few on record. The list below is partial, but over the entire list, there are NO October dates in the record book.
We will challenge a few record lows as well in the coming days. Currently, our only forecast record low is Halloween morning... but you can see the other days will be close. We'll see how things pan out over the coming days, but it's easy to see a scenario where we end up colder than currently forecast on one or several of these days.
Finally, a quick visualization showing the cold pushing... We'll see several reinforcing shots of cold air over the coming days, with the blues, purples, and whites indicating temperatures WELL below average across the state for much of the upcoming week:
For the local traditionalists that assume Halloween will be cold, consider this an early treat.