Denver: High of 37 Snow Tuesday, 100 degrees today

[StormchaserChuck!]

9-8 snow in Denver

https://forecast.weather.gov/MapClick.php?lon=-104.9966125320643&lat=39.74309828855951#.X1O7BXlKhPY

[raindancewx]

Severe cold tends to sporadically dump into the Southwest during La Nina years with low ACE. Look at the record cold outbreaks in CO, NM, etc - they tend to be in La Ninas. I think January 1971 was -17 in Albuquerque. 2010-11 isn't a great example since it had fairly high ACE, but you did see negative readings in February down here.

In some sense there were hints of this in June, when there was a rogue snow storm pretty far south with lows in the 40s in some spots down almost to Mexico.

 

[donsutherland1]

4 hours ago, StormchaserChuck! said:

9-8 snow in Denver

https://forecast.weather.gov/MapClick.php?lon=-104.9966125320643&lat=39.74309828855951#.X1O7BXlKhPY

Denver has had one case where there was measurable snow the day after the temperature hit 90 degrees. On September 12, 1993, the temperature reached 92 degrees. On September 13, 5.4” snow fell.

[Ginx snewx]

 

[StormchaserChuck!]

Technically 99*.

https://w1.weather.gov/data/obhistory/KBJC.html

 

Winter Storm Watch in Denver metro!

https://forecast.weather.gov/showsigwx.php?warnzone=COZ040&warncounty=COC031&firewxzone=COZ240&local_place1=2 Miles W Denver CO&product1=Winter+Storm+Watch&lat=39.768&lon=-104.873#.X1TGTnlKhPY 

[StormchaserChuck!]

10 hours ago, donsutherland1 said:

Denver has had one case where there was measurable snow the day after the temperature hit 90 degrees. On September 12, 1993, the temperature reached 92 degrees. On September 13, 5.4” snow fell.

That's good info about Phoenix breaking it's Summer record by 2 degrees this year, and Alaska by 2 degrees last year, I feel it's related. 

[donsutherland1]

27 minutes ago, StormchaserChuck! said:

That's good info about Phoenix breaking it's Summer record by 2 degrees this year, and Alaska by 2 degrees last year, I feel it's related. 

Also, there on September 4, Israel and Cyprus set national record high temperatures for September. Jerusalem reached 109.

[Amped]

Seems like Denver usually got snow in September back in the 90s.   9/8 is a little early.   I think the record earliest is 9/2.

[Roger Smith]

This is already setting up north of the border. The heat ridge over the west coast has begun to retrogress slightly and it's allowing a much colder high over northern Alberta to push south, with fronts slowly edging west as well. My location is still in the warm air (it has been hot and hazy here for 2-3 days, highs in low 90s). The front is into eastern BC now and Calgary AB has a northeast wind, rain and 41 F. It will probably be like that around Denver by Tuesday, I think the snow will be confined to higher western suburbs and the Rockies, the high plains will be chilly but maybe a bit above 40 F with rain mixing at times. 

These devellopments spell trouble for California already facing some wildfire threats, a Santa Ana wind situation will intensify, the heat will remain in place west of the Sierra Nevada, and we may be hearing about wind-driven firestorms again. 

[Roger Smith]

The flow of cold, dry air around the northwest flank of this developing low has proved problematic for widespread portions of the northwestern U.S. and southern BC.

In some places, assisted by topography, northeast winds gusted to near 50 mph. This brought down tree branches and caused power failures scattered throughout the region. Blowing dust closed I-90 west of Spokane and also US 2 and US 395 highways near Spokane. I see from hourly reports that similar winds have spread out of the Green River valley into the Vernal UT region. Much of Nevada was reporting very windy conditions today (Labor Day).

I think the impact on California may be very serious. The wind gradient will increase there on Tuesday and Wednesday, it won't turn colder though, just a hot Santa Ana downsloping wind, and with numerous wildfires already underway, some of those might turn into uncontainable fast moving firestorms like the situation that destroyed the city of Paradise two years ago. 

Where I live, which is roughly 150 miles northwest of Spokane, we had no severe impacts, but gusty northeast winds made it feel very chilly, compared to the heat wave we were experiencing, and tonight is cold enough for scattered frost through the higher terrain around here. The heat is going to build back up as the ridge redevelops over top of the Colorado low which will be ejected as a closed low heading east-northeast. 

Quite an active weather pattern for early September, but I remember that it snowed heavily in Calgary at this time of year in 2014. 

[raindancewx]

Red River, New Mexico, at 8,600 feet above sea level has reliable weather records for 1906-2014. The local NWS is calling for six inches of snow with this storm in that town. That would be the third highest September snowfall on record there - and only behind 1936 and 1971. Getting up to 4 inches of snow in September is pretty common at that elevation (~once a decade) but more than that is pretty rare. For the 1906-2014 period, there is also no record of accumulating snow earlier than September 17th.

[Roger Smith]

Hey raindancewx, 60 mph east wind gusts at KABQ -- that's stronger than almost anywhere else in this storm so far. 

Las Vegas had a gust to 50 mph at 0700h and I looked on their TV news sites, plenty of minor wind damage and four foot waves on Lake Mead (what's left of it). 

Looks to me like the cold northeast turning north to northwest outflow is petering out now as the dynamics weaken slowly, will be slowly back to ridge building over the far west from now on. Visible satellite imagery earlier showing massive smoke outflows in northeast CA towards northern central valley. Expect to hear some fire news later but not sure whether any other parts of the central valley experienced strong outflow winds, they did reach 29Palms earlier (in the Mojave). 

The humid wedge that was over the south-central interior of CA was gently nudged back to where it originated, the Sea of Cortez. 

Looks like the heat trough is bruised but still standing. 

Most of Utah is very chilly, Vernal is barely above freezing and they are not high up at all. I'm sure if they got even a trace of snow it would earliest on record (unless the dinosaurs were keeping records maybe). 

[raindancewx]

I saw gusts to 71 mph at Albuquerque on sustained winds of 47 mph out of the East at one point. But to be honest...that's actually pretty common here. The east wind is the main reason Albuquerque gets 10 inches of snow long term rather than 15 or 20, the wind just destroys the snow.

I was looking at my method for calculating what the PDO will do in Nov-Apr (in aggregate), and the best match I got was 1961-62. PDO was around -0.4 for March-August on the Nate Mantua method (I think it will be this year too when the Mantua PDO comes in sometime in the next week), and I think Nino 1.2 will be around 20.0C on the monthlies for October (they tend to run much warmer than the weeklies). Anyway...a lot of the closest years for Nino 1.2/March-Aug PDO blends have essentially a super -PDO.

I wasn't really expecting that, but it'd be interesting if it verified. Still have to see the August PDO value though, and see if there are any last second changes with Nino 1.2. 

I mention this because you can get unusual cold/dry air dumps into the West if the PDO goes really negative. It's not a cold signal at all for the East.

 

[StormchaserChuck!]

crazy for 9-9

[Roger Smith]

So for DEN the actual result (at KDEN) was a mixture of rain, sleet and snow, they're only saying 1.0" on 8th out of 0.72" precip, and today's prelim report is .02" precip with light snow mentioned (but they don't give an amount until end of day). Even if that 0.02" is something like 0.2 to 1.0 more, the total snow was sparse at the location, probably did increase steadily across the DEN metro to reach mostly snow in the mix at higher elevations. 

Temperature anomalies on 8th (-30) and 9th (-29) have yanked the monthly anomaly down from +6 after 7d to -2 after 9d. This will continue for a day or two then DEN will see what I'm already seeing here, a return to the heat (highs here from Sunday to Wednesday have been 92, 65, 68, 84). Here we had a minimum of 33F on Tuesday morning (DEN had 31F). 

The anomalous cold was also quite exceptional in Utah. SLC on 8th had 55/43 for a -21 anomaly. Vernal in northeast UT had 41/31, not sure what anomaly that gives but assuming their normal mean is 2 lower than SLC, it would be around -32. Moab (Canyonlands) also failed to break 50. It has warmed up slightly today in Utah. At one point Bryce Canyon had a wind chill in the 20s (F). Normally it would be close to 80 F there at this time of year. I was there in 2016 and it was around 90 degrees on the first of September. Even more bizarre, I think Las Vegas had a midnight high and the entire night was warmer than most of the day. At this time of year, that rarely if ever happens in the desert southwest. 

[raindancewx]

Today was the second coldest September high in Albuquerque back to 1892 - only 47F. Trailing only 9/27/1936. No high had ever been below 61 during Sept 1-15 in Albuquerque, from 1892-2019.

The average high for the last 100 years on 9/9 is 85F - so legitimately close to 40 below average. Monthly high here dropped from 89.1 through 9/8 to 84.4 through today.

It's actually almost unprecedented in the records to go from a hot August to a cold September - I'm a little skeptical yet that September will be able to remain below average.

[bowtie`]

I see KDEN's biggest 24 hour change was 93 to 43. Impressive. Nothing like going from shorts and no shirt to winter parka in 24 hours. 

[Roger Smith]

More likely from skateboard to snowboard.