Another day of monsoon season, and we're looking at a broader area of increased Flash Flood risk as moisture and dynamic support expand somewhat north and east today. The Flood Watch for flash flooding has been updated accordingly. Read on for a little more info... #utwx (1/4)
Here's one model's representation of how convective activity could play out throughout the day and evening. Given the cloud cover and convective inhibition in place, the delayed start of more significant convection (likely not until 1-2PM) appears appropriate. (2/4)
While convection brings high uncertainty in total rainfall amounts at certain locations, QPF gives us some sense of where water amounts may be highest and how large those amounts may be. These totals are for the whole day, but are likely to fall in much shorter periods. (3/4)
As always, use caution in areas prone to flash flooding: Slickrock, slot canyons, normally dry washes, steep terrain, burn scars, and be aware that heavy rainfall can produce deep ponding or fast moving water in urban areas and roadways. #utwx (4/4)
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1/9 To shed some light on the science, here's a schematic look at the structure of a downslope wind event along the Wasatch Front. For more detail on this graphic and the setup for this impactful event, keep reading... #utwx
2/9 The September 2020 wind storm was a complex meteorological event combining elements of strong synoptic winds associated with deep low pressure system with components of a classic downslope wind event. It was this combination that led to a widespread, long-duration event #utwx
3/9 A pool of cold continental air moved southward from Canada through the Intermountain West with the progression of an upper-level trough. As the system deepened, upper level winds (our 'background' flow) increased, and significant transport of this dense cold air occurred.
1/7 It is the first anniversary of the 2020 Downslope Wind Storm that impacted much of northern Utah. This event goes down as one of the most widespread, impactful weather events the state has experienced in many years. This thread details some of the impacts. #utwx
2/7 Here are the peak wind gusts for the event across northern Utah. Wind gusts as high as 99 mph were reported (with unofficial reports near the U over 100 mph).
3/7 Initial reports estimated more than 4500 trees were damaged or downed during the event across mainly Salt Lake, Davis and Weber Counties. Liberty Park lost near 70 trees. Some of these tress were up to 100 years old. Tree damage was especially severe due full leaf canopies.
1/8 For those wondering why the mountains are no escape from the smoke these days... One key difference between our wintertime valley pollution and summertime smoke is the presence or lack of a stable layer in the form of a temperature inversion. #utwx
2/8 This oversimplified graphic shows how the stable layer/temperature inversion creates a cap that traps a shallow layer of pollution near the surface in winter, while under warm and well mixed summer conditions, these pollutants (like smoke) are distributed throughout.
3/8 There are scenarios where the concentrations are high near the surface, and others where the surface remains relatively 'clean' while concentrations aloft are very high. But with enough smoke, over sufficient time and distance, distribution in the column becomes homogeneous.