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Front Range snowstorm nowcast/conditions 3/13-15


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13 minutes ago, thunderbolt said:

Any updates

I brought the Heisy magnet with me. Flurries for a few hours now ha. Meso Models actually accurately forecasted the snow hole near Estes today. Me and the friend I’m with tried to get out N of here late yesterday but it was too late. Still, we got to walk down into town in a foot of snow this morning was nice scenery.

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313 
FXUS65 KCYS 142257
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
457 PM MDT Sun Mar 14 2021

.SHORT TERM...(Tonight - Monday) 
Issued at 352 PM MDT Sun Mar 14 2021

...HISTORIC AND CRIPPLING BLIZZARD SEVERELY IMPACTING TRAVEL AND
COMMERCE ACROSS MUCH OF THE AREA... 

Extreme snowfall. Whiteout conditions. Severe drifting. Impossible
travel. This epic winter storm & blizzard has truly become one for
the record books, literally. A storm total snowfall of 25.8 inches
was recorded at NWS Cheyenne as of the 12 PM MDT observation, with
periods of moderate to heavy snow continuing through the afternoon
hours. This already shatters our 2-day record, and could even near
or exceed 30 inches by the time all is said and done. Snow amounts
upwards of 4 feet have been reported in some of the higher terrain
along the Laramie Range! Very impressive indeed. Extreme snow fall
rates of 2-3 inches were common through the event with a number of
instances of thunder snow as a highly anomalous fetch of moist and
unstable air interacted orographically with the Cheyenne Ridge and
the Southern/Central Laramie Range. 10 inches of snow fell in a 4-
hour period ending at 7 AM MDT this morning! That would be a solid
snowfall event just in itself, but extreme rates persisted through
the morning with widespread totals reaching 2-3 feet along/east of
the Laramie Range as an extremely impressive TROWAL wrapped across
the CWA in the presence of deep upslope. Surface cyclogenesis over
Colorado led to tightening MSLP gradients, and widespread blizzard
conditions as wind gusts up to 50 MPH plagued the area for most of
the early morning and afternoon hours. Drifts became impressive at
5-10 feet and WYDOT has reported via Twitter that rotary plows are
needed to clear portions of I-80. Perspective: This is the type of
equipment normally used to clear mountain passes in the Spring. It
is virtually impossible to travel, and could remain very difficult
for the next day or two as the degree of drifting is unprecedented
on this scale. This is even considering that snow and wind impacts
should diminish this evening and overnight. 

Spectacular Water Vapor Satellite display with an extremely large/
intense upper-level low spinning over east central CO w/ quite the
footprint encompassing over half of the CONUS. Expect this record-
breaking system will begin to fill shortly as it drifts off to the
east-northeast, but wrap-around moisture should support periods of
snow through Monday morning, although any additional accumulations
should be limited. Direct impacts from snow and blowing snow could
lessen considerably in the next few hours, but it will take a good
bit of time to dig out. 

.LONG TERM...(Tuesday - Sunday) 
Issued at 332 AM MDT Sun Mar 14 2021

A very active pattern in store for Tuesday to Wednesday evening as 
we have a quick succession of this current winter storm lifting 
northeast, followed by a closed low moving south across the Four 
Corners region, and finally a shortwave embedded in the eastern side 
of a ridge that builds into SE Wyoming and W Nebraska Thursday. Once 
the ridge builds in Thursday, skies should clear and temperatures 
will warm up to above normal once again. But, until then, there are 
chances of precipitation across most of SE Wyoming and W Nebraska, 
most likely snow as our temperatures will be in the 20s at night, 
only warming up the lower-to-mid 30s during the day. Accumulations 
were previously forecast to be between 1 and 3 inches, but now with 
the latest model runs, it's looking closer to an inch or less with 
higher amounts in the mountains and higher elevations. The center of 
the low stays well south of forecast region and it moves very 
quickly eastward and northeastward, but as it interacts with the 
current major winter storm, the low stalls the winter storm, keeping 
the snow and some minor impacts around until Wednesday 
afternoon/evening when both systems are pushed out of the way by a 
strong ridge. Another reason this small second wave is less likely 
to drop buckets of snow on Wyoming and Nebraska again is because as 
the winter storm moves northeast, it puts Wyoming and Nebraska on 
the southeast side of the storm where the winds are westerly, which 
is downsloping for most of our forecast area and limits the growth 
of the snow showers.

&&

 

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Just came in from shoveling. 19.7” total. Running out of places to put it. I actually hope we’re about done!

Also, several posters on weather5280 noted a reddish color in the first few inches of the storm from last night, and I did too- probably the snow that fell 12-8 AM today. There have been big dust storms in west Texas the past couple days. Could this have been ingested into the snow that made it all the way up and around to here?

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After the storm in a couple days, I think there are 2-4 more storms of lower intensity based on the progression of powerful lows over southern Kamchatka since late February. There was another big one the other day, 990 mb or so. That's for the end of the month. Big SOI crash the other day has been showing up around 3/22-3/23 as a good system too. After that, there are several days forecast with 980-990 mb lows in that southern Kamchatka zone over the next three days on the GFS, favoring, roughly early April. The final storm in the sequence will probably be the most powerful, and then it will warm dramatically, I think we'll see mid-80s down here once the sequence ends.

Broadly speaking, that Kamchatka zone is the northern part of the WPO / West Pacific Oscillation zone, and that area is highly correlated to cold in the West in Feb-Apr, and it also helped us out in the Fall with the big systems in Sept/Oct.

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5 minutes ago, skierinvermont said:

WOW so ~46" total (I can add)

Yea it’s an amazing amount of snow.  Open our patio door and there’s a 5 ft. bank of snow staring at you.

In Nov. 2019 we got 30” of snow from a storm right before Thanksgiving - that storm took a similar track as this one, but this one apparently stalled in a very favorable location.

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Models were 5-6" too high with the snow yesterday and about 3-5" too low today. 

Looks like they  overestimated the  SE flow regime and underestimated the N flow regime on the south side of the CCB. Heavy snow started right as the 700mb winds started cranking out of the north.  The storm did not really track further north than predicted.   Palmer divide was always going to be the southern cutoff.

 

 

 

 

 

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2 minutes ago, Amped said:

Models were 5-6" too high with the snow yesterday and about 3-5" too low today. 

Looks like they  overestimated the  SE flow regime and underestimated the N flow regime on the south side of the CCB. Heavy snow started right as the 700mb winds started cranking out of the north.  The storm did not really track further north than predicted.   Palmer divide was always going to be the southern cutoff.

 

 

 

 

 

The NWS snow obs were pretty much in line with the Euro/NAM about two days ago.

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