Much-needed snow for portions of the San Juan Mountains

A low pressure system over the Four Corners region has brought some good snow to the Southern San Juan Mountains of Colorado, where 27″ of snow has fallen at Wolf Creek Ski Area over the previous 24 hours as of this morning.  Snowpack in the San Juans was only about 50% of average prior to this storm, so this has been a much-needed heavy snow event.  Of course, this heavy snow was fairly localized, with much lighter snowfall amounts reported at other ski areas in Colorado, even in the northern/western San Juan Range.

More snow is expected for Wolf Creek today as they will be in a favorable S/SW flow.  Elsewhere, a cold storm system dropping down the west coast continues to bring snowfall to the lower elevations near the coast in Oregon and even Northern California.  The past several days have featured well below average temperatures along the west coast, including low elevation snowfall in Washington and Oregon, including the Seattle and Portland areas.  Seattle itself has received only light snowfall amounts due to downsloping winds, but some areas of the San Juan Islands picked up impressive snowfall amounts.

Here is an image of NOAA’s 24-hour probabilistic snowfall forecast, showing the 50th percentile snowfall projection across the Western U.S.  While this shouldn’t be taken verbatim, it does give a good idea of which areas will be favored for snow today.


Very cold temperatures across the Western U.S.

A very cold airmass has become entrenched across the Rockies this week, resulting in bitterly cold temperatures across the region, including some record lows.  This morning, DIA set a daily record low of -8, following a daily record low maximum temperature of 13 on Tuesday.  The cold airmass is impressive both in terms of its persistence and for the time of year, given that we’re in the third week of February which is getting late in the season for extended cold snaps.  Also, the depth of the arctic airmass is impressive, meaning that mountain inversions are not as strong as usual with cold temperatures experienced at all elevations.  The West Coast has not been immune to the cold either, with record low temperatures this week from Seattle to San Francisco. 

Below are some of the low temperature readings over the past 24 hours (time ending 7am this morning) for both Colorado and the rest of the Rocky Mountain states.  The coldest temperature in Colorado was -26 in Fraser.  Elsewhere, the northwest side of Glacier National Park recorded a low of -42, Peter Sink in northern Utah recorded a low of -40, and West Yellowstone in SW Montana recorded a low of -38!

Colorado (24 hour lows):

  • -26, Fraser
  • -23, Crested Butte
  • -21, Craig
  • -20, Silverton
  • -18, Leadville
  • -17, Vail Pass
  • -15, Greeley
  • -14, Pikes Peak
  • -12, Steamboat Springs
  • -8, Denver/DIA
  • -8, Air Force Academy
  • -4, Ft. Collins

Rocky Mountains (24 hour lows, 7am Feb 20 – 7am Wed Feb 21):

  • -42, Polebridge/Glacier NP (MT)
  • -40, Peter Sinks (UT)
  • -38, West Yellowstone (MT)
  • -31, Yellowstone Lake (WY)
  • -31, Seeley Lake (MT)
  • -30, Butte (MT)
  • -28, Big Sandy Opening (WY)
  • -23, Pinedale (WY)
  • -20, Bozeman (MT)
  • -19, Stanley (ID)
  • -19, Cody (WY)
  • -18, Island Park (ID)
  • -18, McCall (ID)
  • -15, Laramie (WY)
  • -15, Togwotee Pass (WY)
  • -15, Dillon (MT)
  • -13, Jackson Hole Ski Area (WY)
  • -13, Lander (WY)
  • -12, Alta-Mt. Baldy (UT)
  • -11, Helena (MT)
  • -11, Kalispell (MT)
  • -8, Jackson Hole (WY)
  • -8, Park City (UT)
  • -5, Sun Valley (ID)

Eastern Colorado Preliminary Snowfall Totals February 19-20

A storm system accompanied by an arctic airmass brought widespread snowfall and very cold temperatures to the Front Range and Eastern Colorado on Monday February 19.  Snowfall was banded in nature, which resulted in variable snowfall amounts with the highest totals reported in Boulder County.  Here are some of the preliminary snowfall totals from NWS local storm reports across the region as of Tuesday morning, February 20.

Snowfall Totals February 19-20, 2018:

  • 9.0″ – Louisville
  • 8.5″ – Lafayette
  • 8.1″ – Boulder
  • 7.2″ – Arvada
  • 7.0″ – Idledale
  • 6.0″ – Evergreen
  • 5.7″ – Greeley
  • 5.6″ – Wheat Ridge
  • 5.6″ – Loveland
  • 5.5″ – Thornton
  • 5.0″ – Air Force Academy
  • 4.8″ – Westminster
  • 4.5″ – Manitou Springs
  • 4.0″ – Englewood
  • 4.0″ – Denver (Downtown)
  • 3.5″ – Aurora
  • 3.5″ – Colorado Springs
  • 3.0″ – Castle Rock
  • 2.9″ – DIA
  • 2.8″ – Monument

Why does snow have difficulty showing up on radar sometimes?

Snow can sometimes be difficult for radar to pick up on especially here in Colorado.  When there are “shallow” cold air masses that do not break mountain top level the cloud deck can be near or at the surface up to around 10,000 feet.  With the ground level at 5-6,000 feet the cloud mass is only 4-5,000 feet thick.  That is enough cloud mass to produce light snow at the surface but the radar beam is looking well above the surface.  The radar beam may be too high in fact to pick up on the snow that is falling out of the low clouds.  That setup is occurring today (2/19/2018) with snow falling from Fort Collins to Castle Rock but there are minimal to no radar returns.  As upper level moisture increases this afternoon snow will show up very well on radar but as the upper level moisture decreases late this evening there will likely be a period of snow that radar does not pick up on very well once again.    

Winter storm system moving into the Rocky Mountains

A storm system is moving into the inter-mountain west today, which will result in a good snowfall for the Northern and Central Rockies over the next 24-48 hours.  The storm has already been producing heavy snowfall across portions of Washington and Idaho, including the Spokane area.  The system will continue to spread snowfall into the mountains of western Montana and Wyoming today, and eventually the Colorado Rockies tonight through Thursday where Winter Storm Warnings are in effect.  

The heaviest snowfall amounts over the next 48 hours are expected in the Bitterroot Mountains of Idaho/Montana, Glacier National Park in Montana, the Tetons in Wyoming, and the northern/central Rockies in Colorado.  Snowfall will reach Utah is well, extending from the Wasatch Mountains southward to the Bryce Canyon region, but amounts will be lower as the main storm track will be taking a NW to SE trajectory across Montana, Wyoming, and Colorado. 

Below is a screen capture of the current NWS watches, warnings, and advisories in effect for the Western U.S. with the pink colors indicating Winter Storm Warnings and the purple colors indicating Winter Weather Advisories.  Also, strong downslope winds are expected ahead of this storm along the eastern slopes of the Continental Divide, especially in southern Wyoming as evidenced by the dark yellow-shaded colors.


Colder and more active pattern developing over Western U.S.

The weather pattern has been undergoing a shift over the past several days to colder temperatures across the Rockies, which is a change from most of the winter up to this point which has been unseasonably warm for all but northern Montana.  High pressure is shifting farther west just off the west coast, which is allowing for colder Canadian airmass intrusions into the Rockies, along with a more active storm track.  While the strong ridge of high pressure off the Pacific coast will continue to act as a barrier to storm systems with deeper moisture, the active pattern with frequent low pressure systems from the northwest will continue to bring frequent snow chances to the Rockies over the next week, and likely through the end of the month.  Depending on the individual storm tracks, some of these systems will occasionally bring snow to areas east of the Continental Divide as well.

The map below shows NOAA’s climate prediction center probabilistic snowfall forecast for the next 72 hours.  The 50th percentile range indicates the “most likely” range of snowfall over geographic areas, and paints a general picture of which areas will be favored for the most snowfall over the next 3 days.  



The low pressure system will be moving into Northwestern U.S. tonight through Wednesday, resulting in locally heavy snowfall amounts across the Washington Cascades, Idaho Panhandle, and Northwest Montana.  Strong winds expected along the eastern slopes in Glacier National Park have even prompted a blizzard warning as this storm arrives.  The track of this system will continue to move toward the southeast Wednesday night into Thursday, bringing good snow to the Tetons of Wyoming and eventually the Colorado Rockies.  

The snow will be beneficial to the mountains of Colorado where snowpack has been below average, but notice how other areas hurting for snow this winter will not be favored in this pattern, such as California, and to a lesser extent Utah.  This is due to high pressure just off the California coastline acting as a barrier, and resulting in a storm track that will be missing these areas to the north and east.

Cloud cover makes for tough viewing of lunar eclipse in Colorado, Wyoming

A rare event occurred on early Wednesday morning January 31, 2018, in which there was a lunar eclipse combined with a super moon, and a blue moon (i.e. second full moon within a calendar month).  Unfortunately for viewers in the Rockies, cloud cover obscured the lunar eclipse for many, although this spectacular event still ended up being viewable in some areas with less widespread cloud cover and.  Here are a couple of images of the lunar eclipse from Castle Rock, CO on January 31.



Storm track this week to favor Pacific Northwest and Northern Rockies

A northwest flow pattern will be in place across the Western U.S. this week with high pressure over southwest and west central areas helping to direct the jet stream over the Pacific Northwest and Northern Rockies.  This will result in a wet and snowy pattern for these areas, while southern areas remain much drier.  Below is an image of the 5-day precipitation forecast from NOAA, which outlines the weather pattern well.  Northern Colorado will likely see some precipitation from this pattern, especially the northern mountains and even the northeast plains at times, but it does not favor big storms. 

While the Cascades and Northern Rockies will likely see heavy snows at the high elevations through the weekend, unseasonably warm air pushing in from the southwest will result in rising snow levels for many areas west of the Continental Divide.  For much of California, Utah, Southwest Colorado, Arizona, and New Mexico – areas that are already suffering from extremely low snowpack values – this pattern continues to favor dry conditions unfortunately.  As has often been the case this winter, we are heading back into a western ridge of high pressure/eastern trough of low pressure pattern, with much colder and more active weather over the Eastern U.S.


Drought conditions expanding across Colorado

An abnormally dry winter season so far has resulted in drought conditions expanding across the state in recent months.  The latest U.S. drought monitor, released on January 25th, now has the majority of Colorado officially under drought conditions.  For the first time since this dry pattern took hold, drought conditions have now extended into the Denver Metro area, I-25 corridor and eastern plains.  Portions of the northern/central Colorado mountains as well as the Boulder/Ft. Collins areas remain drought-free for now, but are classified as “abnormally dry”, and will likely end up under drought conditions sooner rather than later if the weather pattern doesn’t undergo a significant shift.  Western and southern Colorado is now experiencing severe drought conditions, where snowfall has been minimal so far this winter.

Unfortunately, the pattern heading into February does not look to improve, as high pressure appears to be the dominant feature (aside from a weak system here or there) through at least the first half of the month.  Let’s hope we start to see better moisture arrive during the spring months before fire season arrives.


Eastern Colorado Snowfall Totals – January 21, 2017

Following an uncharacteristically quiet start to the winter season, Eastern Colorado finally experienced its first substantial snowfall event of the 2017-2018 winter season on Sunday January 21st as a strong storm system moved across the state.  Strong northerly winds during the storm resulted in high impacts due to blowing and drifting snow, especially across the plains.  Here are some of the preliminary snowfall totals as reported by NWS local storm reports.  The highest totals occurred in the Jefferson County foothills.

  • 17.2″ – Pinecliffe
  • 15.0″ – Conifer
  • 14.0″ – Eldorado Springs
  • 12.0″ – Genesee
  • 10.5″ – Idledale
  • 9.8″ – Monument
  • 8.5″ – Nederland
  • 7.5″ – Federal Heights
  • 7.1″ – Boulder
  • 7.0″ – Arvada
  • 7.0″ – Greenwod Village
  • 6.9″ – SE Aurora
  • 6.5″ – Westminster
  • 6.5″ – Castle Rock
  • 6.3″ – Parker
  • 6.0″ – Denver
  • 5.7″ – DIA
  • 4.9″ – Ft. Collins
  • 4.0″ – Canon City
  • 3.5″ – Longmont
  • 3.5″ – Greeley
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