You know you are desperate when you get excited about the shallow cumulus that are developing over the Salt Lake Valley today, Below is a loop showing the development of these clouds looking south from the University of Utah through about 1450 MDT. There's even some virga!
Those clouds are developing ahead of a weak upper-level trough that is near the Pacific Coast and a weak surface boundary that is in advance of the upper-level trough near the boarder of Idaho and Nevada/Utah. The 2119 UTC radar image shows that area is producing stronger cells than the "cumulus patheticus" that we've had over the Salt Lake Valley so far today.
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| Source: NCAR/RAL |
Let's have a look at what the Rapid Refresh Forecast System (RRFS) ensemble does over the next few days. I'll focus on 24-hour precipitation totals ending at 0600 UTC (0000 MDT), but note that most of this precipitation is produced during the afternoon and evening when convection is strongest.
For the period ending at 0600 UTC 14 August (0000 MDT Thursday), which covers today, the RRFS gives a nothing burger to the Salt Lake Valley and most of the west desert areas of Utah. The action is in that area around the aforementioned boundary. Mean forecast precipitation (upper right panel) is greatest right along the ID-UT border. Maximum forecast precipitation (lower right) is over 0.5" in some areas.
I would not interpret that as meaning everyone in the Salt Lake Valley will get precipitation, especially since there are only six members in this ensemble, but I would expect that we will see deeper convection tomorrow and perhaps storms that can produce rain to the valley floor. For Salt Lake City, the NWS is going with a 30% chance of showers and thunderstorms after noon tomorrow and a 40% tomorrow night before midnight. There's a chance!
This weak monsoon surge will keep some shower and thunderstorm chances around until Saturday. Will we get measurable rain at the airport? Time will tell.
Why is that UT-ID-NV border area so active for storms in the summer? Many days this year when I've checked the radar there are storms moving off the border tripoint northeast into Idaho, but little activity elsewhere in Utah.
ReplyDeleteThe simple but maybe not all that satisfying answer is that the pattern this year has been pretty persistent this year with a weak anomalous troughing over the northwest that has helped keep things going there.
DeleteYou know after this near record breaking dry summer, I'll take any amount of rain....but let's get down to brass tax, Jim. What are the chances we get some snow this week?
ReplyDeletePay me enough and I'll say 100%
DeleteWelp after looking at the 5 day forecast, I just might take you up on that offer lol
DeleteLast saturday (august 9th) there was a small wildfire in Skull Valley, and created a very well defined lane of smoke high over salt lake. I'm curious if your cams caught it, or if there is anything interesting meteorologically? It surprised me how little it seemed to spread out, and how tight the smoke stayed over such distance.
ReplyDeletehttps://kutv.com/news/wildfire/fire-ignites-in-skull-valley-burning-nearly-1500-acres-in-one-day
Great to have the RRFS back. The four maps you present: 1 control ; 2 mean; 3 min; 4 max. What is the control? It's similar to the mean but slightly different, reminds me of NAEFS and GFS. Is the control related to HRRR?
ReplyDeleteIt's been running, but I haven't been using it.
ReplyDeleteThe RRFS is comprised of 6 forecast runs with differing initial contions. The "control" is member one. The mean is the average of the 6. The max and min are the highest and lowest values of the 6 run at each grid point.
The RRFS will eventually replace the HRRR. It has a similar grid spacing (3 km). That said, the NWS has really struggled with the RRFS and it will be a wile longer until its operational.
Thx. So the "control" is 1 of 6. Is there any reason to note it? Thinking no. Should it have equal weight as the other 5? Thinking yes. Is it likely to be more accurate? Thinking no. I'm assuming member 1 (the "control") is equally likely as the other 5, the difference being initial conditions. The three items: mean, min, max make total sense to me. Trying to make sense of this 4th item "control." It's 1 of 6, no more than that?
DeleteLooks like the Utah Snow Ensemble has the same 4 map setup. I've always focused on the plumes haven't really looked at maps, didn't realize this control has always been there. For summer rain, the RRFS total precip map of the Wasatch Front is nice bc it gives you a sense of rain in both the valley and the mountains. These days I'm trying to avoid being on a bike in the mountains in the rain ... so I'm on the hunt for additional info like the "control" as to whether rain is more likely. Btw, thx for all the great work you do getting really useful info up on weather.utah.edu, Great resource
DeleteI find it helpful to have one member of the ensemble displayed. The idea of a "control" run is a leftover from a long time ago and probably incorrect nomenclature today. Just think of it as one member of the ensemble, just to get your bearings.
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