JACKSON, Wyo. – A spring roller coaster weather pattern will continue across heading into late April. After hitting 73ºF in Jackson on Tuesday, a cold and snowy pattern will return from Wednesday night to Friday with 1-2 feet of snow expected across the higher elevations of the Tetons.
Recent Weather Pattern
The weather pattern has fluctuated substantially over the past week, and every day has presented a new set of conditions compared to the day prior.
Around this time last week, we were in the midst of a late season cold blast and winter storm, which produced 48-hour snow totals of 5-13 inches in the Tetons above 8,000 feet on April 16-17.
Grand Targhee enjoyed excellent late-season powder conditions during its final week of the season.
In fact, at least some snow fell over seven consecutive days from April 11-17, with seven-day snow totals ranging from 1-2 feet in the Tetons.
Snow fell in the valleys as well, though accumulations were generally light and short-lived, as much of the snow that fell did not accumulate, as is typical this late in the season.
Still, the change to colder weather was quite noticeable as Jackson had a high temperature in the 30s on Thursday and Friday.
Precipitation favored the crest of the Tetons and Teton Valley during the April 16-17 storm, while only limited moisture made it to the Jackson Hole Valley, with off-and-on light snow showers occurring.
The town of Jackson only received 0.09 inches of precipitation during the April 16-17 event, while the higher elevations of the Tetons received 1.0 to 1.5 inches of precipitation. On the west side of the Tetons, totals ranged from 0.2 to 0.4 inches around Driggs and Alta.
Over the weekend and early this week, a strong ridge of high pressure built over the Interior Western U.S., leading to a return to warm temperatures. Jackson hit a high of 70ºF on Monday and 73ºF on Tuesday, and all of a sudden it felt like early summer.
Scattered high-based showers and thunderstorms developed on Tuesday evening, producing spotty light/brief rain, gusty winds, and a bit of lightning activity across the area.
Below is a 7-day weather summary for the town of Jackson.
For perspective, the average high and low in Jackson on April 15 are 53º and 28º.
Upcoming Weather Pattern
The next storm system is already beginning to impact the Tetons with snow and rain showers developing across the area during the day on Wednesday.
A cold front moved through on Wednesday morning, and temperatures on Wednesday afternoon are 30ºF to 35ºF colder than on Tuesday afternoon in the valleys, with temperatures hovering in the upper 30s to low 40s in Jackson and Driggs as of 3 p.m. Wednesday.
Showers will continue to pick up in coverage heading into Wednesday night, and snow levels will dip to the valley floor overnight. Moderate to heavy snowfall is expected in the Tetons overnight, with minor accumulations also possible in the valleys.
On Thursday, we may see some lulls during the day as the first of two main waves exits our region, but snow showers will remain possible, favoring the higher terrain. Temperatures will remain chilly with highs in the low 40s in the valley and 20s in the mountains.
A second wave will then arrive from the northwest on Thursday afternoon and evening, and a second stronger cold front will also arrive.
As a result, snowfall rates will pick up in coverage and intensity on Thursday afternoon and Thursday night, with significant accumulations expected in the Tetons. Snowfall from this round will also be drier and more powdery across the higher elevations with a colder airmass in place.
The valleys will also pick up some accumulating snowfall on Thursday night, though accumulations will likely be heavier in Teton Valley compared to the Jackson Hole Valley, due to expected west/northwest winds which favor the west side of the Tetons more so than the east side.
Snow will also continue into the day on Friday, eventually becoming more showery and intermittent on Friday afternoon. We could see some sunshine peek through on Friday afternoon, but temperatures will remain cold for this time of year, with highs in the low 40s in the valleys and 20s in the mountains.
Total snowfall from Wednesday through Friday will range from 1-2 feet above 9,000 feet in the Tetons, including Targhee, the higher terrain in Grand Teton Park, and the higher terrain around Teton Pass.
Significant travel impacts are expected over Teton Pass, starting on Wednesday evening and Thursday morning, with the highest impacts then expected from Thursday evening through Friday morning when a combination of snowpacked roads and icy underlying surfaces is expected.
After this storm, a break in the pattern is expected on Saturday with partial clearing and comparatively warmer temperatures with highs near 50 in the valley. However, afternoon cloud-build-ups and isolated rain and snow showers can still be expected.
Another system is projected to move across the Western U.S. on Sunday and Monday, with snow and rain shower chances returning to the area. Confidence in the details is low, however, as this system looks more disorganized.
Heading into the middle of next week, an unsettled pattern looks to continue with near-daily rain and snow shower chances, and highs projected to reach the low to mid 50s each day (close to average for late April).
Here is a 7-day snowfall projection across North America, which represents the average of 50 simulations of the European Weather Model. This is another impressive “winter” pattern in April on the heels of a historically poor winter for snow across the Western U.S. as a whole.
Looking further out, a fairly typical spring pattern looks to continue into the first week of May, with frequent shower chances expected. NOAA’s 8-14 day outlook has near-average temperatures favored (average highs in early May are in the upper 50s), with a slight above-average signal for precipitation.
Looking even further out, a transition from a weak La Niña pattern to a strong El Niño pattern is underway, which means that sea surface temperatures in the Eastern Equatorial Pacific Ocean are warming to above-average levels. And by mid-summer, well above average sea surface temperature anomalies associated with a strong El Niño are expected.
Strong El Niño conditions in the summer tend to favor an active subtropical jet stream, which in turn favors above-average summer precipitation (May through September) across Wyoming and Eastern Idaho, including the Greater Yellowstone region. The best examples of summer analog years similar to what is expected this year include 2023, 2015, and 1997.
Summer temperatures do not show a strong tendency during summer El Niños, meaning “equal chances” for above and below average temperatures can be expected. But generally speaking, heat waves seem to be fewer and shorter-lived during summer El Niños compared to non-El Niño summers.
Alan Smith, Meteorologist
