October Outlook

 

Short term:
The first part of the advertised cool down began yesterday with high temperature about 5-10 degrees lower than they were on Tuesday.  Today is another near average day before temps will dip below average tomorrow through the weekend along the Wasatch Front with the arrival of a reinforcing shot of cold air that will push slightly farther west than yesterday’s.  We, however, will see nothing in the way of precipitation, as all of that action is well to our east.  A few more clouds tomorrow and light breezes is all that will accompany the cooler temperatures.  Night time temps tomorrow night through the weekend will dip below freezing in mountain valleys and some of the colder low valleys as well. Time to cover up or harvest the plants.
Next week, the closed cut-off low pressure system that has been sitting off the California coast will gradually move inland.  Over Southern California, Southern Utah, and Arizona.  Not too much dynamics or moisture associated with this system but it will bring us a slight chance of showers–with the best chance for precip mostly to our south.  The timing on this looks to be about Wednesday of next week.  Southerly flow that develops ahead of the low may warm us up back to near average by Tuesday



Long term:
Everything beyond the next 7 days is very vague at this point but there is nothing to suggest that the blocking high pressure ridge parked off the coast of British Columbia will be going anywhere anytime soon.  So our best chances for snow will remain with cut-off low pressure systems or weak, cool systems that periodically drop down the east side of the ridge.  El Nino, which for a couple weeks, was looking a little stronger in the models, now looks weaker again.  The CPC has now given only 55% chance of development.  I was never as sold on it’s development as they were so I’m not too surprised.  I also believe that an ENSO neutral year or a very weak El Nino is better for Northern Utah’s chances at seeing average or above precipitation.  La Nina has a tendency to favor the Northwest, El Nino – the southwest, but an ENSO neutral year often aims the jet stream more at the mid-latitudes (including the Wasatch).  Teleconnections begin to play a significant role in our weather this time of year, but as of now, most of those are in neutral states and forecasted to stay that way for at least the next ten days or so.  We’ll keep an eye on those as well as the MJO over the next few weeks to see if they show signs of livening up, whether good or bad.
For the month of October, it’s looking mostly dry until at least mid-month.  After that, the CFSv2 suggest near average precipitation through the end of the month. So overall, I think we’ll be below normal precip-wise and near normal temperature-wise for the month barring some drastic change in the pattern.  Not too much excitement as of yet, but remember, things can change in a hurry once the Pacific steps on the gas.


 As far as seasonal outlook, not much reason to change my original snow forecast for the season of about normal.  If a weak El Nino does indeed develop, the southern parts of Utah may be more likely to jump above average with the North slightly below.  But I’m guessing that El Nino will be mostly a non-factor for us this winter so most areas of Utah will have equal chances of seeing above/below average snowfall.  Sounds a bit like a cop-out to say just an average year, but the best we can do is call it as we see it, and right now there isn’t anything out there to suggest otherwise.  Besides, I think after last winter, we’d all be quite happy with an average snow year, right?

El Nino vs. La Nina influnces on the Untied States

 

According to NOAA’s Climate Prediction Center, weak El Niño conditions may develop this fall. How might a full-fledged El Niño event this winter influence weather where you live?
Years of monitoring and studying El Niño and La Niña events have helped scientists better understand how these seesawing warm and cool cycles in the tropical Pacific typically influence climate and weather patterns throughout the United States. This information can be particularly useful to farmers and water managers.
El Niño and La Niña are particularly influential in the winter. These maps show the difference from average December-February temperature and precipitation averaged over 22 El Niño and 19 La Niña episodes that have occurred in the past 60 years.
In the top row, shades of red indicate areas that were up to 3 degrees Fahrenheit warmer than average while shades of blue indicate areas that were up to 3 degrees cooler than average. In the bottom row, shades of brown indicate areas that received up to 2.5 inches less than average precipitation while green indicates up to 2.5 inches more than average.
During El Niño events, the easterly trade winds that blow across the tropical Pacific Ocean are weaker than usual and sea surface temperatures in the central and eastern Pacific become warmer than usual. An outcome of warmer waters is increased thunderstorms in the eastern tropical Pacific, contributing at times to well above normal precipitation on the West Coast. El Niño events also increase the odds of unusually wet and cold winters across the southern tier of the United States, while the Pacific Northwest tends to experience milder winter temperatures than usual.
During La Niña events, the pattern is typically reversed. Sea-surface temperatures in the eastern tropical Pacific are cooler than normal. The polar jet stream tends to shift northward over the central Pacific Ocean, increasing the likelihood of wetter- (or snowier-) than-normal winters in the Pacific Northwest and colder temperatures in much of the western half of the country. The meandering jet stream also typically leads to dry conditions and above-average temperatures in the southern tier of the country.
Maps by NOAA climate.gov team, based on data provided by Michelle L’Heureux, NOAA Climate Prediction Center. Caption by Caitlyn Kennedy. Reviewed by Mike Halpert, NOAA Climate Prediction Center.