textproduct: Denver/Boulder

KEY MESSAGES

- Another round of snow for the mountains tonight. Mostly light accumulations, more around Rabbit Ears Pass and Steamboat Springs.

- On and off snow for the mountains through this weekend and into next week.

- Above normal temperatures continue through this coming weekend. Change to colder temperatures early next week.

SHORT TERM /Through Tonight/

Issued at 406 AM MST Thu Dec 26 2024

Take a quick look at the sun this morning as we're in a quick break between weather systems. North and Middle Parks won't get a peek as they're still under stratus as a lot of low level moisture got into those valleys over the last couple days and that will remain so for quite a while. In a change of roles, these areas will now have fairly steady and moderate temperatures due to the moisture. Fog over the eastern border is advecting out and should be either gone or dissipated by mid morning.

Cirrus is racing in from the west and should get thick again this afternoon. We sped up the timing a few hours and it may come even faster than that. If so, our forecast highs may be a bit too warm. The best lift from tonight's wave will move across the mountains late afternoon/early evening and the I-25 corridor in the early evening. There could be a few light showers with this, but there's westerly flow off the ground so there should be more evaporation than what we had last evening. And once again, it will probably be warm enough to be all rain below 6000 feet.

The bigger story is the beginning of a long period of orographic snows in the mountains. Tonight just looks like a warmup as the period of QG lift and instability associated with the passing wave is pretty short. Just a couple inches in most places, though the Park Range which does really well in these setups could have heavy snow in the backcountry. Probably just minor to moderate impacts to Rabbit Ears Pass tonight.

LONG TERM /Friday through Wednesday/

Issued at 406 AM MST Thu Dec 26 2024

Northwest flow aloft continues to bring multiple rounds of light mountain snow through this weekend. With snowfall rates relatively light, decided no highlights at this time due to minor impacts of slick roads along mountain passes. Friday morning, a plume of Pacific moisture arrives. Orographic lift should allow for light snow to continue for areas above 9.5k ft north of I-70; 2-4 inches total snowfall could occur Friday through Friday night with the heaviest along Rabbit Ears Pass. QPF fields drop significantly across WPC ensemble viewer by Friday night into Saturday morning thus leading to a short break in snow. 700mb temperatures increase 1-2C across the region. Afternoon highs Saturday should increase with majority of the lower elevations reaching mid 40s to low 50s. Mountains and valleys should remain similar to Friday due to cloud cover and ongoing light snow with temperatures peaking to the mid 20s to low 30s. Westerly winds Saturday will lead to downslope winds for the lower elevations. Wind gusts up to 35 mph may occur for parts of the I-25 corridor especially near the Wyoming border. QG field display strong subsidence Sunday morning for majority of northeastern Colorado thus any additional snowfall for the northern mountains will not amount to much.

700mb temperature advection displays cooler air entering the forecast area Monday morning. There is strong agreement in ensembles for both recent runs and previous runs of cooler temperatures for majority of our region. This update includes overall lower temperatures Monday afternoon and night. Also, model guidance is in agreement of strong northwesterly flow and tighter pressure gradients creating a widespread gusty day from the mountains to the lower elevations. Ensembles favor cooler temperatures continuing into mid next week.

AVIATION /12Z TAFS through 12Z Friday/

Issued at 406 AM MST Thu Dec 26 2024

VFR will prevail through tonight. Ceilings in the 6000-8000 foot range are expected after 01z. Scattered rain and snow showers could push ceilings lower briefly requiring instrument approaches to KDEN (30% chance). South winds at KDEN/KAPA are expected to become northwest around 10 knots around 20-22z.

BOU WATCHES/WARNINGS/ADVISORIES

None.