This week in weather: November 26, 2018

The weather this week will be nearly a mirror-image of last week. Quiet conditions statewide early on will fade slowly, with the potential for heavy mountain snow later in the week. Read on for our complete forecast.

Mountain snow totals since last Thursday

Snow totals since late last week were quite impressive across the Mountains, with several ski resorts reporting more than a foot of snow.

A-Basin: 20″
Winter Park: 19″
Breckenridge: 15″
Steamboat: 13″
Eldora: 13″
Vail: 12″

As expected, very little moisture/snow actually made it into the Metro area. A few areas did receive a light dusting a wet snow Saturday night as upper-level dynamics briefly won out in the battle against the downslope. This occurred mainly east and south of Broomfield.

Shown below is our snowfall forecast map (issued Friday afternoon), with the observed storm totals per location contained in boxes. Green ones indicate that the observed snowfall was within one inch of the given forecast range, while red was outside the scope of our forecast.

The biggest snow total in our forecast domain was 14″ near Grand Lake! Boulder reported no snow, while DIA picked up 0.7″ Saturday evening.

As we close out the month of November, the snowpack in Colorado is quite healthy, resting at 124% of normal. As you will see, we should add to this further during the upcoming week.

Quiescent weather through Wednesday

The storm system responsible for the Mountain snow earlier in the weekend and in Chicago last night is now located in the Northeast accompanied by a deep and cold trough (see below). Similar to last week, though, Colorado begins on a quiet note with a ridge set-up across the West.

GFS 500 mb vorticity map for Tuesday morning.

Initially we will be on the leading edge of the ridge pattern with cool northwest flow in place across our region on Monday. However, the ridge axis will pass on Tuesday, shifting Colorado into warmer weather with return flow coming from the west and southwest (see below).

GFS 500 mb height anomaly forecast animation covering Monday through Wednesday night.

This will translate into calm conditions across Colorado through Wednesday, with temperatures reaching the upper 40’s on Monday and then warming to near 60 degrees for Tuesday and Wednesday with no chances for any precipitation statewide.

Another wave train late in the week

You will notice towards the end of the animation above that as the ridge deteriorates on Wednesday in Colorado, a foreboding pattern looms to our west. Yes, just like last week, a series of Pacific storm systems of varying intensity will move ashore into California and then eastward to threaten Colorado.

The first system will arrive Wednesday night and will be little more than a weak passing trough with some embedded moisture. The second system is scheduled for Thursday night and Friday and will be stronger, but takes a more southern track.

GFS 500 mb height anomaly forecast for Thursday morning showing the two late-week storms

At this time, both systems appear to keep a progressive, open-wave structure and therefore won’t materialize much if any upslope east of the Mountains. Thus, the late week storms will mainly impact the Mountains with more heavy snowfall. Most areas above 10,000 feet in western Colorado should see 6 to 12″ of snowfall by the end of the week. We do caution that the GFS is a little more active with the pattern than the Euro model at this time. The exact potential for snowfall in the High Country is somewhat uncertain.

GFS total snowfall forecast through the week. Heavy snow in the Mountains is again possible.

The lower elevations stand only a small chance of picking moisture late in the week, mainly on Friday during the day, though our forecast includes a slight chance of showers early Thursday as well. As can happen with Pacific storms, both late-week systems will be lacking cold air, so much so that we think precipitation will remain rain on the Plains, or at worst, a rain/snow mix with no accumulation.

GFS model-derived snow level forecasts for the timing of the two late-week precipitation chances in Denver.

Overall, the story again this week will be the widespread moderate to heavy Mountain snow. Any trickle-over moisture into the Metro area will be sparse and likely in the form of patchy rain showers early Thursday morning or during the day Friday. Temperatures late in the week will cool back down into the mid 40’s to lower 50’s.

If you’re hoping for snow, the end of next weekend looks intriguing from the perspective of several models. Both the current and new GFS indicate a potential snow storm for the Front Range. The Euro model isn’t quite on-board with this yet, and neither are we…..

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Forecast Specifics:

Monday: Mostly sunny and quiet. Highs in the upper 40’s on the Plains and mid 30’s in the Foothills.

Tuesday: Mostly sunny with increasing clouds through the afternoon. Warm and pleasant. Highs in the upper 50’s on the Plains and in the middle 40’s in the Foothills.

Wednesday: Morning clouds then mostly sunny and warm with highs in the lower 60’s on the Plains and upper 40’s in the Foothills.

Thursday: An isolated morning rain shower, then partly to mostly cloudy and cooler with temperatures in the low 50’s on the Plains and upper 30’s in the Foothills.

Friday: Overcast with a chance of isolated rain showers throughout the day. Highs in the mid to upper 40’s on the Plains and mid 30’s in the Foothills.

High Country: Dry, partly cloudy, and breezy conditions will be in place across the Mountains through Wednesday evening. Two late-week storm systems will bring pulses of moderate to heavy snowfall to most of Colorado’s mountains. The first is Wednesday night into Thursday afternoon. The second is Thursday night into Friday night. 6 to 12″ or more of snow is possible as a result. Check PowderCAST for forecasts for all the Colorado ski resorts.

DISCLAIMER: This weekly outlook forecast was created Monday morning and covers the entire upcoming week. Accuracy will decrease as the week progresses as this post is NOT updated. To receive daily updated forecasts, subscribe to BoulderCAST Premium.