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Snow and record cold coming Sunday

9:30 AM MDT, Saturday, October 24, 2020

But first, the fires. Gusty and dry west winds are already occurring above 7500 feet and will continue through today creating conditions for spreading wildfire. Those winds make break through the denser cold air in some places below 7500 feet as well. Then, a record cold air mass and snow should quiet the fires tonight and Sunday.

The cold front will likely be through the Cheyenne area in the late afternoon, the Boulder-Denver area early this evening, and Colorado Springs a couple hours after nightfall. We are not likely to see temperature rise above freezing again until Tuesday afternoon. Snow is likely to begin during the late night in Cheyenne and spread southward during Sunday morning. Sunday and Sunday evening are expected to see the most snow, but some areas of snow could linger into Monday morning.

The upslope (northeasterly winds into the mountains) will favor areas in and along the foothills and the north side of the Palmer Divide for the heaviest amounts. But there will be another important element with this storm. Bands of heavy snow oriented southwest-to-northeast about 10-20 miles wide will probably develop and extend 100 miles or so out onto the plains. Snowfall rates in these bands could exceed an inch per hour. Some areas might only see those heavier rates for about an hour, while other areas could experience one or more multi-hour periods of moderate or heavy snowfall rates.

Most likely accumulation:

3-7 inches: northeast plains (DIA, east side of Denver metro, Weld County, Longmont), with the heaviest amounts where those heavy bands occur.

6-10 inches: in and near the foothills (west and south sides of Denver metro, Castle Rock, Boulder, Nederland, Estes Park, Cheyenne)

12 inches: in some locations where the heavy bands are more persistent (probably about 10% of the area)

Records:

Snowfall records are not expected since the storm is occurring on the same dates as the October blizzard of 1997 that left 15-50″ throughout the region (including 29.8″ in Boulder).

Record cold is very likely. Sunday and Monday high temperatures should remain below freezing, and possibly in the teens on Sunday. Monday and Tuesday mornings will probably range from the single digits to low teens.

Fire weather to winter weather

1:00 PM MDT, Thursday, October 22, 2020

The first of two strong cold fronts is impacting the lower foothills and eastern plains of Colorado but not resulting in much change for the higher terrain and west of the continental divide. The next cold front Saturday evening is expected to bring more widespread cold as well as snow to the whole area during the second half of the weekend.

Fire weather

The lower elevation fires east of the divide are being tamed by the colder and damper weather in the eastern foothills. There may be a brief period of warmer and drier westerly winds that develop on Saturday ahead of the next cold front, but then very cold weather and snow should really help control those fires Sunday and Monday.

The high elevation and west slope fires (like East Troublesome Gulch) are still in the relatively dry and warm air above this shallow cold air mass. By Saturday it is likely that strong westerly winds will develop ahead of the next cold front. Then snow and cold on Sunday and Monday should help quiet those fires as well.

Cold and Snow

Today’s cold air and clouds are shallow (the higher mountains are above it) and not likely to produce any significant precipitation. But there will probably be some areas of drizzle or freezing drizzle and maybe some tiny snowflakes (called snow grains) through Friday morning, mainly in localized areas in and along the foothills.

After the cold front late Saturday we are likely to see widespread snow and cold, with record cold possible early next week. At least a couple inches of snow appears likely, and this type of storm may exhibit some southwest to northeast bands of snow with heavier amounts. I will update on Saturday.

More fire weather, then colder Thursday, snow this weekend

11:30 AM MDT, Tuesday, October 20, 2020

Dry and mild weather with some gusty west winds Wednesday will keep the fire danger high for the next 36 hours. Then a cold front on Thursday will turn it colder and less windy (after an initial surge of north and northeast wind), and a colder front late Saturday will likely bring some snow with it.

Today through Friday morning

There is already a weak front moving through today. Wind should calm down later today and overnight. Gusty west winds may develop again in and near the foothills Wednesday afternoon and night ahead of the next cold front that should push through on Thursday (probably morning or early afternoon). There may be some areas of low clouds and light freezing drizzle Friday morning, but most areas will stay dry as the temperature falls below freezing.

The Weekend

The cold front this weekend is looking quite cold and accompanied by a storm system. It may not warm up too much ahead of the weekend cold front. Friday afternoon and possibly part of Saturday should be the relatively mild part of the weekend, but still cool. Right now it appears that the cold front will push through sometime Saturday afternoon and snow should develop Saturday evening or very early Sunday. It looks likely that at least several inches will occur across the Front Range region, but that part of the forecast will need updating later this week.

More wind and smoke

2:45 PM MDT, Friday, October 16, 2020

The next cold front for the Front Range region is due to move through late Saturday afternoon or evening. Gusty winds may develop tonight and continue Saturday ahead of the cold front, with warm and dry conditions. Areas east and southeast of the major fires will have the highest chance of smoke.

Gusty winds from the north or northwest are likely behind the cold front late Saturday, and then decrease in strength as they will swing around to the east and southeast by Sunday. Sunday will be the cooler day of the weekend, and there is a chance for some areas of clouds by Sunday morning. But overall, dry conditions are forecast to continue for the foreseeable future.

The impact of the cold front will be much smaller in western Colorado where dry and relatively warm weather is expected this weekend. Watch for gusty winds above treeline and at the passes on Saturday.

Widespread frost tonight

10:30 Am MDT, Wednesday, October 14, 2020

For many parts of the Front Range region there has already been frosts and freezes going back to the first snow on September 8th. But some areas have escaped anything too damaging. A cold front approaching Cheyenne late this morning should sweep down the Front Range this afternoon. With a good possibility of clear skies and lighter winds late tonight, there is a good chance for widespread temperatures in the upper 20s to low 30s by Thursday morning, and maybe again on Friday morning.

Until then expect warm and windy weather to give way to cooler and windy weather this afternoon and evening. The winds should ease up during the night. Thursday should be a cool day but mainly sunny, then warming up again by Friday afternoon.

Cold front on Sunday, Windy

6 AM MDT, Saturday, October 10, 2020

A cold front should return temperatures to more average autumn levels on Sunday afternoon. For the eastern foothills and plains, Sunday morning will probably still be relatively warm. Windy conditions across the state later today and Sunday are likely to enhance the already serious fire danger and create large areas of smoke downwind of fires.

Precipitation with the cold front on Sunday will probably be limited to mountain areas, especially west-facing slopes. That will probably help tame some of the fires. But significant and widespread precipitation is not expected, and a dry week ahead may very well see more fire issues.

Colder Sunday

6 AM MDT, Saturday, September 26, 2020

Today will be the last in a string of unseasonably warm days. It will also be dry with breezy conditions at times, so be careful with fire.

A cold front will probably have moved through the Front Range region by Sunday morning, and a second cold front will probably move north-to-south through the area during the day. Expect the high temperatures on Sunday and Monday to be 20 degrees cooler than today. It will be mainly dry, but a few areas of clouds and some sprinkles may develop late Sunday. The chance for that is greatest south of Denver, and even there it’s a small chance.

Both Monday and Tuesday mornings could bring some local frosts in some of the colder spots along the Front Range.

Beautiful weekend weather

8:00 AM MDT, Saturday, September 12, 2020

It’s a great weekend for outdoor activity. Chilly mornings will be followed by warm days, around 80 today and into the 80s (lower elevations) beginning Sunday and continuing until at least midweek.

There is still a lot of smoke in the air along the West Coast, and some of that may work its way in our direction after a few days. But the local sources of smoke have been tamed by the storm earlier this week. There is some hopeful news for the West Coast. Some areas of rain or drizzle may move into Washing and Oregon this coming week, and maybe even parts of northern California.

Accumulation likely this evening

12:30 PM MDT, Tuesday, September 8, 2020

If you were expecting to wake up to whitened ground in the Denver-Bouder-Fort Collins corridor, so was I. Although as I indicated yesterday, the full accumulation probably would’t be over until tonight.

The storm is farther west than expected. Moderate and some heavy rain and snow (along with some thunder snow), is occurring in western and central parts of Colorado, which includes the major fire areas.

It appears likely that a period of snow accumulation is likely this evening along the Front Range, with intermittent light snow later tonight. Although the amounts forecast yesterday are probably a little too high, there could still be some tree/power line damage, and record cold temperatures are still expected.

Cold and snow coming, may be slower to leave than originally forecast

9:50 AM MDT, Monday, September 7, 2020

The main change from yesterday is that the storm progression is slower, so the chance for periods of accumulating snow will likely extend well into Tuesday night. Before the cold front this evening, some hot, dry westerly winds may develop again along the foothills.

Storm progression

The strong cold front is likely to move through this evening before nightfall north of I-70, and around or after sunset as you go south. Clouds and precipitation are likely by about midnight (snow above 7500 feet) along the foothills from the western Denver suburbs northward, and spread south and east during the late night.

Rain will probably change to snow before 3 AM in Cheyenne, between 4 and 7 AM from Fort Collins to Denver, and after sunrise as you move south. Snow may be heavy at times Tuesday and become more intermittent as it continues through part or all of Tuesday night.

Peak depth in grassy areas through Tue night

Accumulation this time of year is more efficient at night, but accumulation during the day can occur quickly during periods of heavy snow, and then melting can dominate during lighter snow periods. For that reason, snow depth at the lower elevations is likely to be quite variable.

Above 8000 feet: 10-18 inches

6000-8000: 6-12 inches

Fort Collins (west side), Boulder, Broomfield, west & south sides of metro Denver, Castle Rock: 4-9″

Greeley, Fort Collins (east side), Longmont, DIA, Aurora, Colorado Springs: 1-5″

*NOTE: the official snowfall may be greater than the peak depth on the ground, especially in the lower elevations because the snow depth may increase and decrease more than once during the storm

Impact

Prepare for power outages and damage to vegetation.