Chinook

NWS digital forecast as of this morning

NWS digital forecasts are now at 9.1" for Fort Collins-Loveland and also the same for Denver (Stapleton) up to Tuesday, 5:00PM.

Thanksgiving Week = traffic snarled with heavy snow across the country

We will get a winter storm watch for the northern half of Colorado.

As I mentioned in October (I believe,) there are above normal water temps in the North Pacific, south of Anchorage, by 2 degrees C. I think this has, in this 30-day time period, helped larger ridges to form in the NE Pacific, leading to troughs in the central US. I think the warmer water temps in many recent years have led to larger 500mb-ridges in Alaska, helping to send down arctic air, like during "the blob" of 2013 or 2014 or something like that. So, too much ridge action near Seattle means that little precipitation has fallen. Now, of course, our synoptic systems are also linked to other things, most notably the MJO and east Asian jet streams.

Tuesday: The GFS and Canadian continue to have 7.9" - 14.1" for Fort Collins-Longmont-Denver stations on the maps. The 00z and 12z Euro went north to Scottsbluff Nebraska with a large amount of snow, and the Front Range cities are mostly dry. I think the Euro has the surface front farther north.

Much later than I posted this, the snowfall really started. Apparently it snowed 2.5" to 3.5" in Denver overnight. My area got about 1" overnight.

2nd piece of our snow storm is coming in right now. The 12z Euro has 6-7" of snow all around Denver metro, up to my area, for Monday-Tuesday.

My place got about 1.5" to 2" last night, with temps around 32. The GFS has this for Monday-Tuesday. The 00z Euro is similar but a little weaker with 2.3"-3.9" at our cities (10:1 ratio). The 12z Canadian has this snowfall in Wyoming. I suppose the Canadian might be disregarded at this point. The new 12z Euro isn't done yet. The other storm from next week continues to undergo large changes in the models.

Models have a somewhat better agreement on Monday-Tuesday, as a mostly westerly feature at 500mb could produce some moderate snow amounts in Colorado.

Yeah, the 06z GFS has 38" within 24 hours for Limon to almost DIA at hour 204 (snow total of hours 180-204). So I think that's a little bit unlikely, but fun to look at.

Not too much has changed with this storm. The GFS now has the most of the snow hitting the Front Range cities with the 500mb shortwave on Wednesday, that is 00z Thu to 06z Thu. Then the second pulse, associated with the closed 500mb low, will produce additional snowfall across central and southern Colorado and New Mexico, with some lower snow possibilities up north near me. The weakening 500mb low will also be likely to bring some snow to Kansas. Interesting stat: At Fort Collins, Nov. 9th had a high of 73 and a low of 30, with a temperature departure of +10.0F. This is the first 10.0F positive temperature departure since September 16th, which had a high of 89, low of 57. At Fort Collins, Nov. 16th had a temperature departure of +12.6F, which is the largest positive temperature departure since April 8th, which had a high of 75, low of 44, departure of +12.8F. Models may indeed be hinting at something around 11/27. This 00z GFS run produces a very very strange storm. I don't think this is possible. Other GFS runs had something different. It's so strange that I'll post it.

18z GFS and 12z Euro today are still not going too big with snow amounts, with some decent values over 9000 ft. Of course, there should be higher snow values for SW Colorado (San Juan Mountain Range.) Also, around 6" for Raton NM, with potential of 6" - 18" in the Sangre De Cristo near Raton. The 18z GFS shows the highest 12-hr amount of snow for Denver is 2.9" from 18z Thursday to 06z Friday. I am actually hoping that this won't produce much slippery roads on Thursday night.

The 00z Euro finally changed its synoptic forecast for the 500mb low. It now has the low moving eastward to the Rockies faster,. QPF values now show 3-5" of snow for the Front Range cities, which the GFS has shown for a number of runs. Note: there is not one single 24-hr period when 3-5" of snow falls. Sometimes I think the Euro can struggle with Southwestern storms. By the way, if you haven't checked Pivotalweather.com in a while, it has the Euro QPF, snowfall, and temperatures, and you are allowed to zoom in on regions of the USA. If 2" of rain fall at PHX airport in this storm (as the WPC forecast had about 2") then this will be greater than the TOTAL amount of rain that PHX has had since FEBRUARY 22nd. Perhaps Phoenix should be renamed "Atacama."

Wind gusts are 55-65 mph off the coast, at a couple of buoys

The GFS has 925mb winds up to 65-72 knots offshore from Cape Fear and Cape Hatteras. The GFS 42-hour forecast shown here. These winds would be about 700m or 2300 ft above sea level.

On Wednesday and Thursday, a 500mb low will cut off near San Francisco and will track toward S. California and the Four Corners. The models have been slowly coming into agreement on this. The thing that seems likely is heavy rain for Arizona. The details of the storm system for Colorado are not as clear.

This visible satellite image from yesterday looks kind of like a January satellite image after the snowfall. I think it has more green than mid-winter color images. Also, about 0% of the lakes are frozen over.

Interesting storm-total precipitation plot from KGRR shows that the heavy mesoscale band around Jackson had about 0.92" of precip. The LES north of South Haven had 1.60". I am not sure if these are likely to be accurate in terms of actual precipitation amount.

Lorain to Cleveland is 34-36 degrees right now, but you can already see the evidence of the LES north of Lorain on the radar, in the midst of the synoptic snow.

Local storm report says 6.5" for Spring Arbor MI (Jackson County). Interesting note: I lived on the SW side of Jackson for the Blizzard of '78. I was a baby. I believe there may have been 18" with drifts to 4 ft or 5 ft in that incredible storm.

Fayetteville, AR says thunderstorm in vicinity, heavy rain, 34 degrees, Bentonville AR has unknown precipitation, Rogers AR (next to Bentonville) has freezing rain. Apparently the Tulsa metro area has freezing drizzle, snow, and unknown precipitation.

I just love looking at the radar when there are bands of precipitation that are so smooth.

18z NAM Kuchera snow ratio snow totals (to hour 33.) There are these super weird holes in the snow accumulation that shouldn't be there. It makes snow disappear off the map. Seriously. Could somebody program these post-processing schemes better?

NWS web page now shows a WWA for Grand Rapids, Lansing, Kalamazoo, and a Winter Storm Watch for the Michigan thumb.