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Isolated showers possible today. Break on Saturday before showers and storms return for Sunday and Monday. A more Fall-like system possible for late next week.
Our frontal boundary yesterday virtually stalled over far northwest Utah and southeast Idaho. By the time it finally moved into the Wasatch Front overnight, it had weakened significantly. Still, some metro areas saw stronger storms with plenty of lightning and thunder. You can see radar estimates for precip show were most of it fell to our northwest:
We will start to dry out today, but a few stray showers will be possible in the Wasatch and especially in the Uintas. Tomorrow should be a break day and the best day to get out and do something outside. A closed low will move through the region on Sunday bringing additional showers to the area. Showers should continue into Monday.
High pressure will be back for the middle part of next week but all eyes are on what looks to be our first Fall-like system since the end of August. A lot of uncertainty as both the EC and GFS have been waffling a bit, but right now it looks like the system will move in on Friday into Saturday. At the very least, we'll see cooler temps in the area and a good chance for at least a dusting of snow in the high elevations. We'll keep you updated!
Evan | OpenSnow
Scattered showers and thunderstorms likely late today (Thursday), tonight, and tomorrow. A break on Saturday before another push of moisture brings showers and storms late Sunday into Monday. Attention then turns to a colder storm for late next week.
The moisture from Odile all but missed Utah this time around, but the atmosphere is slightly more damp than it would typically be this time of year. Add in dynamics from a low pressure system moving through northern Utah and you get showers and storms that are likely to form late on Thursday into Friday.
We will dry out by Friday night and have a break on Saturday and for the first part of Sunday before moisture pushes back into the area late on Sunday. Another round of scattered showers and storms looks likely to last through Monday before we dry out again on Tuesday.
Now for the exciting part... Both the EC and GFS now have a trough dropping down off the PacNW coast middle of next week. The trough is progged to progress inland next Thursday and Friday. Both models currently show the trough weakening as it does so. Still, this would be a much colder storm than we've been seeing lately. Snow would likely return to the highest elevations. We'll have to keep an eye on it but it looks like around Friday of next week we could be much cooler and thinking about winter again. GFS then follows this trough up with a second one for the end of the month.
This change in pattern is fairly typical during Fall, which is why I said just the other day that even if models show dry patterns continuing, they may just be slow this time of year to catch on to things. Looks like they are catching on now...
Evan | OpenSnow
Moisture associated with another tropical system will move into the area late this week (Thursday-Friday). Heavy rain is possible.
Remember last week when the remnants of Hurricane Norbert brought heavy rains to much of the area? Well it's a new week and we've got a new tropical system that will help push moisture into the area. This system is named Odile.
There are, however, subtle differences between our scenario last week and the situation for this week. Unlike Norbert, which weakened and moved inland, Odile is likely going to weaken and slowly turn west out to sea. However, there will still be plenty of moisture associated with the system that will be dragged up into the area. Like last week, we have a second, more fall-like low pressure system off the west coast that will help pull the moisture north into the region. This is when forecasting becomes difficult. If this east pacific low moves inland earlier than expected, it will quash the moisture and keep it from making its way far enough north for us to see a lot of rain. Conversely, if the Low stays offshore for too long, there won't be enough flow to pull the moisture up to us. But if this low is in the "sweet spot" at the right time. It can not only pull moisture from Odile north into the region, but it will also add dynamics to the situation to generate more organized convection (thunderstorms) and heavy rain. Right now... this last scenario is what models seem to be liking. That means moisture will move into the area on Thursday and last at least through Friday.
Below is the EC's QPF thru next weekend:
Decent rainfall for most of western and central Utah, including the Wasatch. Next, the GFS's qpf thru next weekend:
As you can see, the GFS is significantly more aggressive with even more widespread rain. Either way, it looks like we'll have a good shot at precipitation.
As for precipitation type, this is warm origin storm so we won't have much cold air to work with. There is some cooler air with the Low in the Eastern Pacific that will gradually work its way into the area. Still... probably the only chance for snow will be on the highest peaks.
The second half of September is when the pattern really starts to change... So I'd expect for something interesting and more winter-like to develop in the models in the next week or two. I'll keep you posted.
Evan | OpenSnow
It's officially Autumn, at least for meteorologists and weather/ski junkies. While the astronomical start of Fall is the more well-known Autumn equinox (~ Sept 21), the more relevant calendar for our purposes is the meteorological one, in which Autumn starts on September 1. So congratulations, we are 2 days into Fall (and that much closer to winter).
After a very cool and wet August for most of the area, we've dried out significantly over the past week. Temps have for the most part been near average. However, signs of the new season continue to emerge. Today, we have a cold front moving through the state that is kicking up winds a bit this morning ahead of it. Precipitation will stay well north of the area up in Montana and Southern Alberta, but cooler air will make it as far south as northern Utah. Tomorrow's high temps should be a touch cooler than today's. This weekend should be back to mostly calm conditions and it will feel a bit more like summer than Fall. Currently the forecast looks tranquil for the next 7 days. We could see another monsoonal moisture surge next week but it will likely mainly affect southern and eastern Utah. Overall, we are just beginning the roller coaster ride we experience every Spring and Fall when the overall pattern is changing and we see dramatic changes from one day to the next. Expect cold fronts to become stronger and more frequent over the next month or two.
Fall / Winter Outlook - El Nino update:
El Nino conditions, which started to develop in the Spring before taking a hiatus for most of the summer, are now starting to reappear. The ONI value in the Nino 3.4 region is once again warming further above normal:
If you recall, El Nino conditions are defined as +0.5C or more above normal. It looks like we are on our way back toward that threshold after briefly dropping below normal in late July.
The CFS model is currently forecasting the following precip anomalies for the Fall months (Sep-Oct-Nov):
What I take from this is that we will likely see occasional monsoonal moisture surges through the next month that might boost parts of Utah and the desert southwest slightly above normal in terms of precip, but in terms of winter-like storms, we should be near average.
By winter, El Nino should be stronger and things get a little more interesting:
This is much more typical of El Nino and exactly what the forecast has been all summer. Northern Utah has about equal chances for above/below normal precip. Southern Utah will be favored more and have a better chance for a good winter.
Again, all of this should be taken with a massive grain of salt as always. There is cautious optimism for a good year. Even an average year here is still 500" -- which is better than we've seen the last 3 seasons...
Evan | OpenSnow
Low pressure will spin slowly through the west today bringing cooler temps and a chance for showers to the area starting today (Monday) through Wednesday. Snow showers will be possible at times above 8,000 feet, but accumulation should be minimal. A bit of a break later this week before chance for showers returns over the weekend.
El Niño is on the rise right now in the Pacific. Latest readings show us continuing to head toward an official El Niño event. Latest ONI shows us just passing the El Niño threshold of 0.5C above normal SST in the Niño 3.4 region. Despite crossing this threshold, we are not in an official El Niño until we have 3 consecutive months of +0.5C SSTs in this region. So while we are not there yet, we are well on our way as temps continue to warm relative to normal. Below is a graph from the CPC that shows our chances through the rest of the year of El Niño/Neutral/La Niña:
As you can see, El Niño becomes increasingly likely through this summer. By the time late Fall and early Winter come around, our chances are nearly 80% of being in an El Niño event.
The big question is "Will this be a strong event?" It is my belief, based on historical records, that weak El Niños don't favor northern Utah much. However, strong El Niños do increase our chances of having above average years. Looking at the model forecasts, we can see the following:
The dotted line is the model average, which shows our ONI value increasing to +1.0 or so by Fall. This is a weak to moderate El Niño event. The strong El Niño events of the past (83-84 and 97-98) saw ONI values in excess of +2.0. Right now, according to the models at least, it looks doubtful that our El Nino will be overly strong.
How about summer? Typically El Niño summers are slightly wetter than normal with a strong monsoonal tap which starts earlier in the summer. The latest 3-month outlook from the CPC reflects this with greater than average precipitation forecasted for the 4-corners region.
So for now we'll just have to wait and see how strong El Niño gets this summer. Again, I'd say the stronger the better for us in Utah as we've typically done well in strong El Niño events in the past.
Evan | OpenSnow