Plummeting Temperatures and the First Measurable Snow are Coming to Ned

posted in: Weather Discussions | 0

A quick look at my weather history compiled over the past 9 years we have lived here shows that the first measurable snowfall (>= 0.1 inches) and the first snowfall over an inch typically occur each year in the first or second week of October. With a few exceptions, it is striking how close these dates are each year:

First Snowfall >= 0.1 Inches
Date Snowfall Amount (in)
October 7, 2018 0.4
October 2, 2017 6.3
October 6, 2016 2.5
October 23, 2015 1.4
September 12, 2014 0.7
October 5, 2013 1.5
October 12, 2012 0.5
October 8, 2011 5.0
October 12, 2010 2.7

 

First Snowfall >= 1 Inch
Date Snowfall Amount (in)
October 8, 2018 3.2
October 2, 2017 6.3
October 6, 2016 2.5
October 23, 2015 1.4
November 10, 2014 2.5
October 5, 2013 1.5
October 24, 2012 2.8
October 8, 2011 5.0
October 12, 2010 2.7
If the current forecast remains on track, the first measurable snowfall and the first inch of snow this year will be on Thursday, October 10th!
A strong storm system in the mid levels of the atmosphere will be located over Idaho on Wednesday morning. Colorado will be positioned in the warm southwesterly flow ahead of this system, and as a result Wednesday will be another mild fall day:
Storm1
The big change will come Wednesday evening as the cold front associated with this system sweeps through Colorado. Behind this front, bitterly cold winds will blow from northeast and temperatures will rapidly plummet into the teens by Thursday morning. The cold temperatures are really the big story with this system. After highs in the mid 60s F on Wednesday, highs will only be in the mid teens (yes, around 15 F) on Thursday.  This is almost a 50 F drop in temperatures! Shorts and T-shirts on Wednesday will be replaced by gloves and hats on Thursday. Given that we really are not acclimatized to cold weather yet, 15 F will feel even colder.
In addition to the cold, there will be snow. The storm will track to a position just to our north by midday Thursday:
Storm2
This is not an optimal storm track for significant snow east of the Continental Divide. Still, there should be enough forcing, upslope flow, and moisture to result in a prolonged period of light snow in Nederland and the surrounding Foothills communities.  Just as important, it will be could enough even on the plains for snow. The National Weather Service snowfall forecast reflects what seems to be the consensus forecast from several different sources:
SnowfallForecast
This places Western Boulder County in the 6-8 inch snowfall range. This may be a bit high, but as I said it seems to be the consensus forecast. It is also important to note that the ground is still warm.  There will be some melting as the snow falls. However, as temperatures drop well below freezing, mountain roads will freeze solid, and driving will likely be treacherous Thursday afternoon.
Temperatures will drop back to around 6 F Thursday night.  My coldest October temperature in the 10 years we have lived here is 5.3 F set on October 15, 2018.  We’ll come close to breaking this record.
Temperatures will gradually moderate this weekend as this storm system pulls away and we dry out.  Whatever snow falls should melt fast.

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