12:45 PM MDT, Monday, October 28, 2019
After a short lull in activity, and maybe some breaks in the overcast this afternoon and tonight, snow is likely to redevelop Tuesday morning from north to south behind another cold front. It may be midday before snow develops south of metro Denver. Snow will likely continue into Wednesday morning and then end from north to south.
This next storm is stronger and better organized than the one we just had, but it is working with less moisture. So although the potential exists for a greater snowfall, the limited moisture may result in a similar amount to what we just had, but no freezing drizzle this time. It does appear that mountain areas (which did not get as much as expected in this last storm) might get a little more with this next one. It also appears that significant snow will spread more onto the high plains of eastern Colorado this time around. Although the winds won’t be as strong as we get in our bigger blizzards, there is likely to be enough wind for some blowing snow and dangerous wind chills, especially east of I-25.
Most likely snow accumulation Tuesday-Wednesday morning
7-12″ Rocky Mountain Park, Nederland, Evergreen, Eisenhower Tunnel
5-10″ Denver-Boulder metro and Cheyenne
3-6″ Fort Collins, Longmont, Colorado Springs
Because it may be cloudy on Wednesday morning, the reduces the chance for a record low (7 in Denver from 1991, 6 in Boulder from 1993). On Thursday morning there is a better chance for clear skies that could allow record lows (10 in Denver from 1991, 5 in Boulder from 1991). The high temperatures in Boulder on Tuesday and Wednesday could be the coldest highs for those dates (record low highs are 26 and 23 both set in 1991). The record low high temperatures in Denver are 25 (Tuesday) and 18 (Wednesday).
The snowfall and record cold should be well over by Halloween evening. But expect snow and the ground and temperatures quickly dropping well below freezing at sunset.
Noon MDT, Saturday, October 26, 2019
We are still looking at a cold wave tonight through Thursday morning with possible record low temperatures and two periods of wintry precipitation, one late tonight through early Monday morning, and the other Tuesday into Wednesday morning.
Snow and freezing drizzle, Saturday night- Monday morning
The one real change since my blog yesterday is that it looks like the potential for a period of heavy snow will probably hold off until Sunday afternoon or night. But that doesn’t mean it will be pleasant before then. After the cold front Saturday night, low clouds and some areas of freezing drizzle and light snow are likely late Saturday night through Sunday morning, with light accumulations possible. Expect icy road conditions, especially Sunday evening and Monday morning.
Most likely accumulation through Monday morning (with most occurring Sunday afternoon or night):
8-12″ mountains & foothills (including Rocky Mountain Park, Nederland, Evergreen, and the approach to Eisenhower Tunnel).
6-10″ in Cheyenne, Boulder, Broomfield, and the Denver area west of I-25 and south of I-70.
3-6″ Colorado Springs, northeast Denver, Longmont, Fort Collins
1-3″ Weld County
Snow, round 2
And even colder air mass and another storm system is forecast to move into the region on Tuesday. Expect snow during the day Tuesday continuing into Tuesday night or Wednesday morning. With this round the heavier accumulations may spread out over the high plains with time. Expect a general 4-8 inches more.
Temperatures are likely to remain below freezing even in the lower elevations Sunday through Wednesday, and maybe Thursday too. The best chance for record low minimum temperatures in Denver and Boulder appear to be Wednesday morning and Thursday morning. The records in Denver for Wednesday and Thursday mornings are 7 and 10, both set in 1991. The record in Boulder on Wednesday morning is 6 (1993) and on Thursday it’s 5 (1991). Record low maximum temperatures are possible in the Monday through Wednesday period as well.
12:15 PM MDT, Friday, October 25, 2019
Enjoy the mild autumn weather today and Saturday. A cold front Saturday evening (maybe afternoon in Cheyenne) is expected to begin a 4 or 5-day period with much below average temperatures. Significant snow is likely Saturday night through Monday morning, with perhaps another period of snow on Tuesday as an even colder air mass arrives.
The first period of snow is likely to spread north-to-south from Cheyenne to Colorado Springs Saturday evening and night, and continue until late Sunday night or Monday morning. It appears that there can be periods of moderate or heavy snow alternating with periods of lull in the action. Most likely accumulations through Monday morning:
8-14 inches in the mountains from Rocky Mountain Park south through the Pikes Peak region, and in the Palmer Divide region.
6-10 inches: Denver (south and west sides), Broomfield, Boulder, Cheyenne
2-5 inches: DIA, Longmont, Fort Collins, Colorado Springs
I will update these numbers tomorrow if necessary. Additional snow is possible on Tuesday.
Sunday and Monday in Denver-Boulder are likely to stay below freezing during the day with teens on Monday morning (assuming cloud cover does not let it get colder). An even colder air mass on Tuesday should result in temperatures barely making to 20s, and falling to the single digits at night. The record low on Tuesday for both Denver and Boulder is -2 (the October record) and that will likely stand. On Wednesday we have a shot at a record if skies clear out Tuesday night. The record for Wednesday in Denver is +7 (1991) and for Boulder it is +6 (1993).
There is some disagreement in weather models about how quickly this very cold air mass will release its grip. Some have milder weather starting to return on Halloween while others keep it quite cold until then.
6:00 AM MDT, Wednesday, October 23, 2019
Today will turn colder after a mild morning with clouds and snow this evening. The best chance for significant snow is south and west of Denver. The northeastern plains north of Denver may see little or no snow. The snow should end Thursday morning.
Most likely accumulations:
6-10 inches: mountains, foothills, and Palmer Divide region of Douglas, Jefferson, and Gilpin Counties.
3-6 inches: Nederland, Rocky Mountain Park, Castle Rock, Colorado Springs, southwest suburbs of Denver.
2-4 inches: Boulder, Broomfield, Denver
around an inch: DIA, Longmont, Cheyenne
less than 1 inch: Fort Collins, Weld County
Next Chance Sunday
After a couple mild days Friday and Saturday, a multi-day period of colder than average temperature will likely begin on Sunday. Snow during that period is a little uncertain now, but it appears that there may be some on Sunday. More on that later.
5:30 AM MDT, Monday, October 21, 2019
The first part of the week should be dry for the lower foothills and plains, and milder by Tuesday. Some flurries are likely today as you get closer to the continental divide.
A cold front on Wednesday will bring cold weather back Wednesday evening and Thursday. The timing is uncertain, but be prepared for the cold air to move in during the day on Wednesday. Some snow is likely by Wednesday evening, probably ending Thursday morning. It’s a little early to pin down accumulation, but several inches looks probable.
In the longer range it is looking like we could be in for a multi-day period of colder than average temperatures and maybe some snow beginning next Sunday.
5:50 AM MDT, Friday, October 18, 2019
Friday and Saturday
You may notice it is unusually mild early Friday morning, but it may not warm up much during the day following a Pacific cold front. It’s not a strong front so temperatures today and Saturday should get into the 60s in the urban corridor. The front may bring a period of gusty west winds, and for the mountain areas expect some snow showers. If any of that precipitation survives east of the mountains, it should be in the form of a brief rain shower. Saturday should start out mainly sunny.
Saturday evening and Sunday
A strong storm should move across northern Wyoming and the Dakotas Saturday evening and Sunday and drag a strong Pacific cold front across Colorado. That one should result in snow along and west of the continental divide, maybe on the order of 6 inches at some of the high passes along with gusty winds.
For the foothills and plains there may be a few rain or snow showers, but most of the precipitation should remain near and west of the high mountains. The main impact for the foothills and plains will be cool temperatures and a period of blustery west or northwest winds.
Public talk about Boulder climatology on Thursday, October 24th
I will be giving a talk at the NCAR Mesa Lab at 6:30 PM on Thursday, October 24th. The Boulder climate station is in its 30th year. Official climatological numbers are typically 30-year averages, and this is the first time Boulder’s observations have been in one consistent location for 30 years. I will talk about the 30-year averages, extremes, and how those relate to the longer-term record. DBAMS October 2019 Meeting Flyer – Kelsch
12:30 PM MDT, Tuesday, October 8, 2019
A strong cold front Wednesday evening will bring in unusually cold weather, with record lows likely on Friday morning. Wintry precipitation is likely Wednesday night and Thursday bringing the first measurable snow of the season to the lower foothills and plains.
Low clouds are likely to increase rapidly Wednesday evening following the arrival of the cold air. Some areas of light freezing drizzle or snow are likely Wednesday overnight (maybe some rain at the start). Precipitation on Thursday is likely to be snow. This is not a classic upslope event with east of northeast winds through the depth of the mountains. The main snow will likely be a southwest-to-northeast band that moves southward through the area (oriented with the upper air jet stream). There may be a brief period of moderate or heavy snow with that band. Right now it looks like timing of the snow band will be Thursday morning for areas north of Denver, and maybe late morning and early afternoon from Denver south. This timing may shift by a few hours as we get closer to the storm.
Foothills and plains: 1-3 inches in most areas (local areas up to 5″ if the snow band slows or stalls briefly)
Near the continental divide: 3-7 inches.
The front will probably be through Cheyenne in the late afternoon Wednesday and then move rapidly down the Front Range late Wednesday afternoon through early evening. Temperatures are likely to plunge to the 20s Wednesday night, and remain near or below freezing on Thursday. Under clear skies and likely snow cover Thursday night we will likely see record lows by Friday morning.
Friday’s record for Denver is 22 set in 1946.
Friday’s record for Boulder is 20 set in 1977.
Friday’s record for Cheyenne is 15 set in 1977.