wxgeek's weather-Snow-Update Oct 8

Update Sat Oct 8

It's always nice when the atmosphere does what the models say once in a while. So things are tracking to previous forecasts. Upper low currently over south central CO and will slowly move northward today. Snow will continue steady most of today through about 3-6 pm and then lighten up and turn more showery. Could still be some flurries overnight and into Sunday morning, but not much additional accumulation after 6 pm Saturday. Snow is being reported down on the Plains at DIA and at APA airport, but temps above freezing so not sticking below about 6500 ft. Plains could see a dusting by this evening though.

Currently 4 inches on Conifer Mtn, so looks like total accumulation will be around 6-10 inches on Conifer Mtn and surrounding favored areas.

Skies may be a little more slow to clear Sunday as upper trough hangs around, but Monday should see clear and warmer temps and will continue through next week. ====================================
Update Fri Oct 7

Sure feels like Fall today, and it's gonna feel like Winter Saturday. Models now in good agreemenbt on the track of our upcoming storm. Upper low will form over the 4 Corners region this evening and track northeast across CO on Saturday into northeast CO by Saturday evening. The track is not ideal for a big snow event for us, but it is close enough that it will provide ample snow to the foothills. Ideal track for foothill snow would be if the upper low tracked slightly farther south and east. The end result will still be a surface low forming over southeast CO Saturday and flow aloft will be a favorable northeast upslope flow. Vicinity to upper low will also provide some good lift and instability. With the low tracking a little farther west, mountain areas east of the Divide will also see quite a bit of snow. NWS has a Winter Storm Watch in effect from 6 am to 6 pm Saturday, and this will either change to a Wnter Storm Warning or Winter Weather Advisory later today. So, forecast now looks like this:

Clouds will increase tonight with snow beginning between 9 pm and midnight. Light snow will fall overnight with snow level initially between 8000-9000 ft. Accumulations of 1-2 inches likely by 6 am. Snow will become heavy at times by Saturday morning and persists into Saturday afternoon with snowfall rates of 1-2 inches per hour at times. Snow level will lower to 7000-8000 ft by Saturday morning and remain at that level during the day on Saturday. Some snow may fall down to 6000 ft, but I doubt there will be any accumulation below 6500-7000 ft. Models still output close to an inch of liquid equivalent, so here is how snow totals are looking:

Favored foothill areas above 8000 ft: 6-10 inches, with up to 12 inches above 9000 ft
Banana Belt Areas: 3-6 inches
Foothills between 7000-8000 ft: 4-8 inches
Foothills below 7000 ft: 1-2 inches

Roads will likely become snow and ice packed above 8000 ft on Saturday, and could be slushy down to 7000 ft, so driving will be difficult, and there will likely be lots of accidents to deal with. Visibility will be very low at times due to fog and snow in the foothills. Areas below snow level will receive a good soaking of cold rain, and roads in the Metro area will be wet and could have standing water at times. Snow should end by Saturday evening with only a few lingering showers Saturday night. Skies should be mostly clear by Sunday morning. Temps will begin to rise Sunday, and will be back to seasonal norms by Monday. Next week looks dry with temps at or slightly above seasonal norms.


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High confidence now that we will see our first snowfall of the season this weekend. Models are in good agreement that an upper low will form over the 4 Corners region Friday night and meander over southern CO through Sunday. A good upslope flow will develop starting late Friday night and persist into Sunday morning. Here is how the forecats looks:

Very windy today before front moves through between 4-6 pm. Winds up to 60 mph are possible over the foothills and Plains, so driving could be difficult at times, along with downed trees and power outages. Snow in the mountains west of the Divide should subside after 6 pm. A brief slop over shower is possible in the foothills as front passes over this afternoon/evening. Winds will subside tonight.

Friday will be a cool and breezy day in the wake of a cold front that will pass over the foothills around 4-6 pm Thursday.

Upper low forms over the 4 corners late Friday night and will bring upslope flow with precip beginning around midnight for the foothills and eastern Plains. Snow level will begin around 8000-9000 ft Friday night, lowering to 7500-8500 ft by Saturday morning. Snow could be moderate at times Saturday into Saturday evening wth snow level lowering to 7000-8000 ft by Saturday evening. Precip will lighten up after midnight Saturday night with only light precip or showers into Sunday afternoon. Skies should begin to clear late Sunday night.

Models produce between 0.75 and 1.5 inches of liquid equivalent for this system from Friday night into Sunday afternoon, so using a Fall translation of about 8 inches of snow per inch of rain, we could see from 6-12 inches of snow above 8000 ft from this system, with 3-6 inches above 7000 ft. Snow could fall down to about 6000 ft on Saturday night, but little if any accumulation below 7000 ft is expected. Since Friday temps will be much cooler, road surfaces will have a chance to cool before snow starts, so I would expect road surfaces above 8000 ft to become snow and ice packed, especially overnight Friady into early Saturday, and then again late Saturday into Sunday morning. Roads may just be slushy or wet during the day on Saturday below 9000 ft. With the upclope flow and precip, visibility will be greatly reduced in the foothills. Please drive with your lights on, even during the day. when fog or precip is present so other drivers can see you. This will be a mostly wet and heavy early season snow. Since roads will be warm underneath, this also means as roads become snow packed, ice will likely form underneath, so roads can be very slick with these types of systems. I believe the NWS will issue a Winter Weather Advisory for the foothills above 8000 ft either later today or on Friday.

My forecast is based on using the NAM/WRF model, as the GFS moves the upper low out much faster, and the Euro model is much slower, so it is a compromise and what I feel will actually happen. If the system is weaker and moves out faster, then we get less snow. If the Euro verifies, precip could stay farther west and affect more of the mountains than the foothills and Plains. But I currently believe the NAM/WRF has the best handle on the situation. Either way, we will see snow in the foothills this weekend, so hope everyone can enjoy the beauty that accompanies our first snowfall, and that if you haven't already done so, this will remind you that winter is not far away and to be prepared for the upcoming snow season.

_________________
"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".

Update Oct 8th