Dec 28,2006 Snowstorm Log

Just a few minutes ago, the first snowflakes of the newest storm began to fall. If the National Weather Service's predictions are correct, this storm could be epic - maybe becoming one of the Top 10 largest snowfalls in Fort Collins history. Amazingly, this storm comes on the heels of last week's holiday blizzard which dumped 19.7" of snow on the city! A storm of that size is fairly rare in Fort Collins, but to have two storms of this size in just over a week apart may be unprecedented. The numerical weather prediction models have been all over the place with their predictions, but if even the moderate scenarios verify, we could be looking at 15-20" by the time everything wraps up. If the most extreme scenario occurs (basically a snowy version of Armageddon), Fort Collins might end up with 30" or more! This is hard to believe, and while there are still many uncertainties, it seems a sure bet that we will get at least 10" from this new storm and probably more like 15-20".

So how much is really predicted? The text of the latest Winter Storm Warning is calling for Fort Collins to get 10-18" for the first round of the storm ending Friday morning, then mentions the possibility of 10-20" more snow for Friday night and Saturday! The gridpoint forecast issued at 11:32 AM gives Fort Collins a total of 20": about 2" by 5 PM this afternoon, 8" overnight, about 4" during the day on Friday (a big break is expected on Friday while the storm reorganizes and cranks up over OK/NM/TX), then another round is supposed to come in Friday night with 4" by noon on Saturday. About this time, the winds are forecast to become quite strong with gusts to 45 mph possible. This along with another 2" of snow Saturday afternoon and evening should bring true blizzard conditions to the area.

Looking at the NWP models, if the 12Z run of the WRF-NMM (North America Model) is correct, the heaviest snow will be tonight and then we will just have nuisance snow on Saturday and maybe snowshowers on Sunday (although farther east, the backlash may give heavy snow to NE Colorado even on Sunday night). This model did very well during the last storm, so it is tempting to buy it's forecast this time as well. I think the GFS has also backed off from yesterday's craziness (for a few runs, the models were leaning towards the extreme scenarios). I think that the 2nd wave of the storm may not be as bad as predicted, but I could certainly be wrong. My best guess is that we'll see a total of 17" of measurable snow when all is said and done. We shall see . .

Are we ready for this? Not really - snow removal from the last storm has been rather difficult or downright frustrating depending on where you live. Last week's storm was enough to overwhelm the resources and manpower that the city keeps on hand for these types of events - while the main arterials have been cleared and are in good shape, many residential streets have barely been touched or just been passed through once with a plow. Some of these streets have huge humps where the snow has been compacted and turned into sheets of ice. The past week saw several days of surprisingly warm and sunny weather, so the neighborhood streets have improved a lot - but there is hardly any place to put any new snow. All the places which were convenient to pile snow have already been piled high! So this next storm could absolutely paralyze the city. Thankfully, CSU is on holiday and overall traffic in town is quite light. But time will tell. I'm guessing that if we get the low end of the predicted amounts (10"?), the city will be able to return to normal fairly rapidly. If we get the NWS-predicted amount of 18", we are going to be in bad shape. If the apocalyptic scenario occurs, there is going to be weeping and gnashing of teeth! The city will be in dire straights for days. In the past couple days, I've seen a renewed sense of urgency - a lot of heavy equipment including road graders are out on the streets trying to make room for the new snow. I'm sure the city's snow removal crews are already exhausted.

That's all for now. I'm going into work now to collect about a week's worth of papers to read (I'm hoping for the apocalyptic scenario), put snow cables on my car, and maybe stop by the grocery store. Then I'm just going to hunker down and enjoy the storm :) I'll probably write another update tonight as the heavy snow begins.

Posted 6:55 PM, Thursday, Dec 28, 2006

The storm has begun! By 10:00 this morning, clouds were lowering and it looked like it might already be snowing in the Foothills. During the day, the clouds lowered further and became more nondescript - this often happens as the upslope flow sets up. The temperature had warmed close to 40 degF so when the precip started falling at around 2 PM, it was rain! It hardly ever rains in Fort Collins in the wintertime. It was very light, more like a drizzle. At 4:30 PM the rain changed to snow as a heavy band on the radar moved in from the east. By the time I left work at 5:30, it was snowing heavily and the roads were already extremely slick. I was the second to last to leave from my department, so the parking lot was wide open! Needless to say, I had some fun doing doughnuts. I'm not sure I've ever done them properly before - anyway, it was a total blast! As I drove the 4 miles back, I saw the results of a traffic accident near the King Soopers on West Elizabeth. The mayhem has begun.

I am a volunteer snow spotter for the National Weather Service. At 5:55 PM I sent in my first report for this storm:

New snow: 1.0", storm total: 1.0", snowdepth: 12.0". Snow began at 4:30 PM. Current weather: heavy snow, 32 degF, winds gusting to 15 mph. Secondary roads already very slick. Because of the previous rain, snow is sticking to tree branches.

The snow began quite a bit earlier down in Denver this afternoon. Some locations in the Foothills have already received 10" with snow rates of 2" per hour! Fort Collins has just 1" . . . Things have really picked up though and the radar shows a solid heavy band has filled and is just hammering the Front Range. It looks like the storm is well underway.

Radar composite from the UCAR-RAP Weather Page for 6:58 PM MST, 12/28/2006. This is about the peak of the storm for Fort Collins.

I subscribe to the Larimer County emergency e-mail list, and this afternoon they sent out the following somewhat ominous e-mail:

Posted 8:55 PM, Thursday, Dec 28, 2006

The snowstorm is going gangbusters - we're probably now in the middle of the first heavy snow period which should start tapering off early tomorrow morning. During the last three hours it has snowed steadily and heavily - at least an inch per hour, sometimes 2" per hour.

In this update, I'll focus on some of the meteorological parameters contributing to this heavy snowstorm.

[Picture lost due to my ineptitude - I accidentally hot-linked instead of putting the actual image here, so it's gone.]

This first map (all of the following maps in this section are from the UCAR-RAP Weather Page) shows the upper level weather chart at 700 mb (about 10,000 feet). Actually, this is not the actual data, but the analysis of a short-term model - but it is pretty close to being the real thing. It shows that the very large storm system has closed off and is currently centered a little south of the Four Corners area. The circulation around this low is bringing up very warm, moist air from the Gulf of Mexico, throough TX and around into Colorado.

Here is the same type of map, but for 500 mb (roughly 18,000 feet). The 500 mb low is centered over the NM-AZ border and is quite broad. Normally for the ideal Fort Collins snowstorm, the low should be over the Four Corners area - but in this case, the low is so large that it appears we are still in a prime area to get strong upslope flow. But this may be more ideal for a heavy Denver snow event.

Here is the current surface plot at 8:33 PM MST, Dec 28, 2006. Strong northerly winds are developing to our north, but our local surface winds have a bit of an easterly component - this is good for continued heavy snow. If the winds went even further easterly, it would be even better. Northerly winds in our area normally descend more than a 1000 feet as they come of the Cheyenne Ridge - this tends to dry the air out and warm it up, reducing our snow. So far this hasn't been a big factor yet. But a so-called barrier jet of northerlies right near the surface can actually increase snowfall in certain situations - this is because the moist, easterly flow hits this band of low-level northerly winds and is forced to rise even before it gets to the mountains - this means that heavy snow falls further east than it might normally fall.

This is a plot from the Platteville wind profiler which is about 30 miles southeast of Fort Collins. Wind profilers sense the wind strength and direction from near the surface up to near the top of the troposphere (the part of the atmosphere where nearly all weather happens). So this plot shows the winds through the depth of the troposphere (to 12 km) vs. time (bottom axis). The leftmost data are the most recent (8 PM MST, Dec 28, 2006). The direction is indicated by the wind barb (it points in the direction the winds are coming from). So you can see that in the lower part of the atmosphere the winds have become strong out of the east, but right at the surface, they are northerly. The speed is indicated by the number of barbs (10 kt for every full barb, 50 kt for a flag). So we have deep upslope throughout the atmosphere all the way up to 5 km (18,000 feet). Since this air is very moist and the winds are blowing it right towards the mountains, this is VERY good for heavy snow.

The 5 PM MST Denver sounding also shows the deep upslope developing. It also shows that the atmosphere is nearly saturated all the way up above 300 mb (that's about 30,000 feet).

Okay, that's enough for now. I'm going to go outside and make one last measurement for the evening. Before I go to bed, I plan to post some pictures from the storm so far - look for these in about an hour.

Posted 9:30 PM, Thursday, Dec 28, 2006

The region's transportation is coming to a halt. Media reports I-70 traffic has come to a standstill and I-70 at Floyd Hill has now been closed. It was already a mess earlier today up near the Eisenhower Tunnel when accidents caused a temporary closure. It reopened this afternoon, but the heavy snow has continued in the Foothills (with close to 20" in a few areas). Now it looks like accidents have brought traffic to a standstill in Idaho Springs. With heavy snow continuing, this means that plows can't plow the road (since it is filled with a traffic jam). Needless to say, the prognosis doesn't look good. I-25 is now closed between Wellington and Cheyenne - a notorious section of road in winter conditions. Also I-80 is closed between Laramie and Cheyenne, and other major routes like US-287 are now closed.

But - Denver International Airport is still open - mindful of all the media coverage of the thousands of stranded travelers from the previous storm, the city is making a Herculean effort to keep the airport open. It helps that this storm has weaker winds (so far) and that the snow is stickier, so it is not blowing as much. My brother-in-law is supposed to fly through on his way to Montana tomorrow, so it will be interesting to see if the airport is still open by then. United has already canceled 120 flights, and Frontier has canceled 100 flights.

Here is an update radar composite as of 9:48 PM MST, Dec 28, 2006. The heavy snow area is still anchored solidly over Fort Collins and areas west of I-25, but it is not looking nearly as solid to the east. This may indicate that the first break is coming in a few hours. But a large area of heavy precipitation is blossoming down in TX and moving northward. It will be interesting to see what happens with this - the short range RUC model seems to indicate that most of this moisture will NOT make it this far north, but rather will circulate around closer to the low center. The low still has to cross the NM mountains and then reorganize, so it is not completely certain how the storm will evolve at this point.

Posted 10:30 PM, Thursday, Dec 28, 2006

New snow (in past 4h15m): 6.7", storm total: 7.7", snowdepth 18". Current weather: 27 degF, heavy snow, winds gusting to 15 mph. Absolute winter wonderland - snow has stuck to every sprig and branch.

Of exceptional note, we are about to eclipse the maximum snowdepth from last week's storm which was 19" - this was apparently the 2nd greatest snowdepth on record since 1949. This morning, before the storm began, I measured a snowdepth of 11-14" in the I-House backyard (which is somewhat protected and shaded) and 9-12" in the front yard. For the specific area I'm measuring snowdepth at, as the storm began we were at 12". Now we're up to 18" and the snow is still going strong. If we surpass 23", this *might* be the all-time record snowdepth (at least as far as I can tell from the data I have - it may be spotty and missing previous large storms though). The 23" snowdepth was the official maximum set during the 2003 March Snowstorm (unofficially I measured 27" in the I-House backyard, but again this is a somewhat protected area so it might collect a bit more snow than an open field would).

Posted 11:30 PM, Thursday, Dec 28, 2006

Okay, the exciting part of the storm is about done. I think the heavy band over Fort Collins will probably break up and taper off in the next few hours. So I am going to bed now. Here are the pictures I've taken of the storm so far.

Here is the view from my office at the Department of Atmospheric Science building at 4:22 PM. The snow has now begun at the lower levels.

This is the Taft Hill/West Elizabeth intersection at 5:52 PM. The roads are already quite treacherous by now.

Here are some pictures taken in the the International House parking a few minutes later.

This is the view of the I-House backyard, taken from my porch at 8:19 PM. I am using the nearest picnic table as my snowboard for taking new snow measurements. The large mound is a snowcave that someone built from last week's storm. By now, you can tell that several inches of snow have fallen.

Here is the view at 9:32 PM. In the last hour, the snow has gotten considerably deeper. The trees are now totally coated with snow - this is partly because it rained before it switched to snow so the snow stuck well. But it is also due to the fact that the snow was very sticky at first.

This is the view at 10:16 PM, just a few minutes after I measured 7.7" of snow so far.

This morning's (12Z Dec 29, 2006) 500 mb map shows that the upper low has barely moved. If anything, it has sunk further south. This is not good for more snow here, but it is excellent for northeast NM and southeast CO.

The 700 mb map shows a scene similar to last night - a very broad and somewhat diffuse low pressure system. The eastern side of the circulation continues to advect very warm and moist air up through TX and KS, supporting heavy rain and convection there. But the flow is just not strong enough right now to bring it all the way into the Front Range. A ridge extends down right along the Front Range, while an inverted trough extends through NE Colorado - most of the precipitation is happening out there.

This morning's Denver sounding is quite different than last night. Now it is only saturated to about 500 mb and there is little upslope component at the lower levels. Also, it has gotten quite a bit colder in the lower levels - reflective of the continued cold air advection in the ridge of high pressure that is nosing down just east of the Front Range.

Unfortunately, I didn't save last night's Platteville wind sounding, and this one (as of about Noon today) only extends back to the period when the upslope was just ending (and the snow was ending as well).

Posted 4:30 PM, Friday, Dec 29, 2006

There hasn't been any snow of note since late last night, so it's been a rather quiet and boring day. CSU was closed today because of the snow, so I've just been enjoying the day at home. I think I'm about blogged out at the moment though. I'm going to post my pictures a little later tonight, but here are the snow totals. If nothing else happens, I might write one more wrap-up and post some video (my best guess is that we'll get 2-3" of snow tomorrow and then that might be it). Anyway, it's been a fun storm. I hope you enjoyed my first snow blog :) Maybe I jinxed this storm by keeping too close of a watch on it.

Here is a map of the snow spotter reports through the first part of the storm (about Noon, Friday, Dec 29, 2006) - courtesy of the National Weather Service. The Foothills have gotten the most by far, with several places close to 30". (NOTE, the NWS has updated their maps - see the entry on Jan 4 for the final version).

[Here are some updated statistics about the storm from Denver's perspective - this is from the Denver NWS web page.]

December 2006 Has Now Moved Into 3rd Most Snowiest Denver December

The latest winter storm (December 28th-29th 2006), which is a second separate winter storm, has officially dumped 7.0 inches at the former Stapleton International Airport. This amount is measured by COOP weather observers and their snow depth is measured at 6AM. This total of 7.0 inches has moved December 2006 into 3rd snowiest Denver December in Denver weather history with a total of 28.4 inches. The most snow ever recorded in Denver during December is 57.4 inches recorded in 1913. December 1913 is also the snowiest month in Denver weather history. (Note: These 2 recent winter storms are separate storms and cannot be added together to count as one single storm because they are one week apart and therefore the December 20-21 storm will still remain in 7th strongest winter storm in Denver weather history)

The December 20-21 Winter Storm officially measured 20.7 inches at the former Stapleton International Airport. This puts this winter storm in 7th position in strongest winter storms in Denver Weather History since 1946. See the table below for the Top 12 Denver Snowstorms since 1946.

Denver’s Snowstorm Total Snowfall Statistics

Greatest Amount Of Snowfall Over 5 Days: 45.7 inches intermittently from December 1-5, 1913
(37.6 inches of continuous snowfall (40 hours) recorded between December 4-5th)

The Top 12 Denver Snowstorms since 1946:

31.8 inches Mar 18, 2003
30.4 inches Nov 3, 1946
23.8 inches Dec 24, 1982
21.9 inches Oct 25, 1997
21.5 inches Nov 27, 1983
21.2 inches Nov 19, 1991
20.7 inches Dec 21, 2006
18.7 inches Mar 5, 1983
17.7 inches Nov 19, 1979
17.3 inches Apr 1, 1957
16.9 inches Mar 20, 1952
16.0 inches Oct 3, 1969

Posted 9:00 PM, Friday, Dec 29, 2006

The latest word from the NWS is that the second wave has been cancelled - at least for Fort Collins. It now seems more certain that the brunt of the storm will hammer the Eastern Plains of Colorado but leave the Front Range relatively untouched. We might get a little light snow and wind tomorrow, but that should be about it. So in the end, this wasn't the remarkable storm that it could have been, but it was still significant, especially coming on the heels of last week's blizzard. The combined snowfall from both storms was about 28"!

Here are some more pictures of the winter wonderland I woke up to this morning.

This is how much snow fell last night after my 10:05 PM measurement - only 0.8".

Here's my car - it looks like digging out a parking spot won't be as bad this time.

It still took about 15 min, but it wasn't that difficult. For good measure, I cleared an extra space.

Posted 10:00 PM, Thursday, Jan 4, 2007

I took some more pictures of the storm aftermath as I drove around in Fort Collins over the weekend, so I'm making another entry on this now very long snow blog. Also, the NWS updated their maps for both storms, so I'm adding this for posterity's sake. In retrospect, the 2nd storm was mostly a dud here in Fort Collins and not really that spectacular for the rest of the Urban Corridor, but it will hold it's place in history - namely for the awesome impacts that it had on SE Colorado, SW Kansas, and NE New Mexico. Some areas of Kansas and SE Colorado had upwards of 30-35" during the 2nd storm. The far southern mountains of Colorado had up to 4 feet and an area near the Raton Mesa had a total of 60"! Needless to say, for the second time in 10 days, large sections of the surface transportation network. Practically all routes south and east of Colorado were shut for several days. A major effort is underway to help save tens of thousands of head of cattle which have been trapped by snowdrifts up to 18 feet high! Helicopters from across the region are being used to airlift hay to the areas where cattle are, and people are also using sledgehammers to break through the ice on creeks so the cattle can drink. It is not a fun time to be a cow in SE Colorado.

This is the view out from my porch on Saturday morning, Dec 30. I bet a lot of people in Fort Collins probably woke up hoping the snow had mysteriously vanished during the night. No such luck. An eerie fog blanketed the area.

Here is the view on Laurel Street less than 36 hrs after the storm had ended. As you can see, the snow removal efforts were decent after this storm.

As I turned onto the side streets, the situation looked less optimistic. Indeed, Fort Collins looks a bit like I would imagine Narnia might have looked like when under the Witch's winter spell.

Some people live off of alleys - a rather dubious journey for anyone not owning a 4WD vehicle with high clearance.

Several of our deacons own hefty equipment which came in very handy this week - they cleared all the snow form the parking lot and piled it onto the church lawn. Needless to say, this snow might be here for a while (June?).

There was a nice sunset Saturdaynight - here is the view from the NE side of town looking SE.