JACKSON, Wyo. – The past week has been dry and sunny across Jackson Hole following a wet start to August. However, we are about to head back into an active pattern late this week and through much of next week.
An uptick in monsoonal moisture along with moisture from Tropical Storm Hilary in the Pacific will both have influences on this upcoming active pattern.
Recent Weather
Summer conditions have returned to the Tetons over the past week following a cool and wet start to the month. Aside from some sprinkles last Thursday morning (August 10), the past week has been dry and sunny.
Temperatures were quite pleasant from last Thursday (August 10) through Monday (August 14) with highs ranging from the upper 70s to low 80s.
The past two days have been hotter with the high temperature in Jackson reaching 89ºF on Tuesday. Similar values are also expected on Wednesday afternoon.
Temperatures are running 1.4 degrees below normal so far in August. This is mostly due to high temperatures which have been well below normal this month, while low temperatures have been above normal.
Upcoming Weather Pattern
Wednesday may be our last dry and sunny day for a while as changes are heading our way.
First, monsoonal moisture will return to the area on Thursday evening and linger through Saturday. Then on Sunday and Monday, we may see another surge in moisture from Tropical Storm Hilary in the Eastern Pacific, though there is some uncertainty.
Moisture is then expected to remain over our area through much of next week with additional surges of monsoonal moisture possible from the southwest.
Before this stormy pattern really takes hold, we may actually see a brief intrusion of wildfire smoke on Wednesday and Thursday morning. This is a result of increasing fire activity over the Pacific Northwest in recent days that has coincided with a multi-day heat wave over this region.
Short-range models are indicating that Jackson Hole will be right on the edge of the smoke trying to sneak into the area from the west/northwest, but it will be a close call. The good news is that any smoke will clear out by Thursday afternoon as stronger southwest winds push this smoke north of our area.
Monsoonal moisture will also begin to filter into Northwest Wyoming by late Thursday afternoon. As a result, we could see some isolated thunderstorms develop late in the day. Otherwise, Thursday will be our last hot day for the foreseeable future with highs topping out in the upper 80s to near 90 in the valleys.
On Thursday night, a shortwave disturbance will arrive from the southwest as monsoonal moisture continues to increase. As a result, scattered showers and thunderstorms will be possible throughout the evening and overnight hours.
Friday is looking active as well with scattered showers and thunderstorms possible during both the morning and the afternoon hours, though we should see some breaks in the action as well. High temperatures on Friday will reach the upper 70s to low 80s.
On Saturday, we have a better chance of seeing a weather window with dry conditions during the morning hours. However, there is a good chance of afternoon thunderstorms as abundant moisture will be in place.
Stronger storms on Friday and Saturday will have the potential to produce frequent cloud-to-ground lightning along with heavy rain.
On Sunday, we could see another weather player as Tropical Storm Hilary works its way northward parallel to the Baja Peninsula.
Weather models are still honing in on the track of this storm, with the latest projections taking it northward all the way into Southern California at which point it is expected to become “extra-tropical” – meaning it will be taking on characteristics of a mid-latitude storm system (rather than a tropical system) as it becomes absorbed into a low pressure trough near the West Coast.
The impacts of Hilary could make it all the way to Jackson Hole. Significant moisture and heavy rainfall will be possible across portions of California and the Southwest initially.
Then, depending on the eastward versus westward extent of the moisture as it pushes northward, we could potentially see an active period of showers and thunderstorms on Sunday and Monday as well.
For now, both Sunday and Monday have a medium to high likelihood of showers, and if the storm system tracks far enough east, then widespread significant rainfall would be possible across Northwest Wyoming.
At the other end of the spectrum, if the track of this storm system were to shift too far west (lower likelihood but within the range of possibilities), then it’s possible we could miss out on the moisture entirely and see dry and windy conditions instead on Sunday and Monday.
As we head into the middle part of next week, moisture related to both the monsoon and Hilary will linger and drift eastward across our area, resulting in additional chances of showers and thunderstorms – generally in the afternoon and early evening hours.
Here is a rainfall projection over the next seven days based on an average of multiple simulations of the European weather model.
As far as temperatures go, it will be somewhat dependent on cloud cover and the frequency of showers. But from Saturday through Tuesday, we should generally see highs in the 70s.
Extended Outlook
An active pattern is expected to remain in place during the second half of next week and into the weekend of August 26-27. Moisture is expected to linger across our area initially, and we could see another monsoonal moisture surge from the south/southwest as well.
As a result, near-daily thunderstorm chances can be expected through the August 26-27 weekend, and possibly through the end of the month.
High emperatures are expected to be within a few degrees of average for the most part, which by late August is in the upper 70s.
Alan Smith, Meteorologist
