textproduct: Western and Central Wyoming

KEY MESSAGES

- Scattered thunderstorms, some strong, are expected through the afternoon and evening hours today. The primary severe weather threat will be strong wind gusts, with a lesser threat of large hail. Isolated flash flooding is possible with any stronger cells today.

- Warmer than normal temperatures will continue through the weekend, with isolated showers and thunderstorms mainly across the northern half of the area. Some storms on Friday may be strong.

- Elevated fire weather conditions are expected Friday through the weekend across central and southern Wyoming.

DISCUSSION

Issued at 427 AM MDT Wed Jun 11 2025

A few remnant showers from yesterday's shortwave are lingering across northern portions of the area early this morning. These should end or move out by sunrise. Then, focus turns to the next shortwave that is currently digging into western Idaho. This one is a little more robust, and with ample moisture availability, convection will be more widespread today.

The latest CAMs have storms beginning by late morning as instability builds across western Wyoming, with this initial activity moving from Teton/Park counties into the Bighorn Basin after noon. Additional development is then expected across central and southern Wyoming as MLCAPE increases above 500 J/kg. By 21Z, the trough axis will begin to push into western Wyoming. This will bring another round of convection to the area, moving from west to east through the evening. With all of this activity today, strong outflow winds will be the primary concern given ample surface heating expected today. Forecast soundings support this concern with the classic inverted-V look and DCAPE values over 1000 J/kg; temperature/dewpoint spreads of 40 to 50 degrees will support outflow wind gusts of 50 to 60+ mph. While a little less widespread, modest shear and steep lapse rates will also support a hail threat with any stronger storms today, especially across western and northern areas. Finally, isolated flash flooding cannot be ruled out with any stronger cells given elevated precipitable water values today (nearing an inch at KRIW which would be close to or higher than the maximum for this date).

Storms will end from west to east late this evening, finally exiting the area around midnight with clearing skies through the rest of the night. The shortwave will be quickly replaced by a weak ridge. This will keep temperatures warmer than normal through the weekend, while still allowing for daily shower and thunderstorm chances as a few waves move through the prevailing flow. The strongest of these may lead to another round of strong storms on Friday across northern and eastern areas. Finally, elevated fire weather conditions are expected Friday through the weekend, especially across central and southern Wyoming where a dry southwest surface flow will set up.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1105 PM MDT Tue Jun 10 2025

VFR conditions across all terminals to start the TAF period with these conditions prevailing through the late morning. Isolated showers are moving across parts of the state for the start of the period. Little to no impacts are expected as a result of these weakening showers but a brief gust 15-25 knots as a result of a decaying shower cannot be ruled out. A nearing disturbance will bring widespread chances for showers and thunderstorms by Wednesday afternoon and evening. There looks to be two rounds of showers/thunderstorms Wednesday. The first occurs in the afternoon starting around 19Z through 00Z Thursday. The second round arrives shortly behind the first moving through the state during the evening from 01Z to 06Z. The main hazards as a result of each round of showers/thunderstorms will be strong gusty outflow winds, small hail, and heavy downpours. Winds will likely be the most concerning as many terminals will see dewpoint spreads of 40 to 50F leading to outflows possibly around 40 to 50 knots or more. Western terminals such as KJAC, KPNA, KBPI, and KRKS have PROB30 groups to show both rounds of showers as they will be fairly close together. Eastern terminals will also see PROB30 groups to represent the second round of showers which does not have full confidence on its exact impacts and timing. Overall there is a good chance for nearly all terminals to see brief outflow gusts of 35 to 45 knots during the period. Stronger gusts of 50 or more knots cannot be ruled out at some terminals. Conditions improve across western terminals around 2-3Z Thursday with eastern terminals seeing quieting conditions around 4- 5Z. The only exception to this may be KCPR where showers and gusty winds may linger through the end of the TAF period.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts.

RIW WATCHES/WARNINGS/ADVISORIES

None.