textproduct: Billings

KEY MESSAGES

-Hot Wednesday (90s to lower 100s). Heat Advisory in effect for portions of the area Wednesday.

-Isolated mainly dry thunderstorms with strong wind gust potential Wednesday afternoon and evening.

-Cold front brings an increasing chance of precipitation late Thursday into Friday; Highs in the 70s Friday.

-Turning warmer again for the weekend.

DISCUSSION

Through Wednesday Night

Hot and dry conditions will continue into Wednesday with upper level ridging and mid-level downslope flow in place. While temperatures are expected to peak in the upper 80s to lower 90s today, the addition of pre-frontal warming Wednesday will allow for temperatures to warm a few degrees warmer into the 90s to lower 100s. While relative humidities will be lower during this time, meaning it will be a dry heat, extended exposure to these temperatures can still be dangerous. Therefore, a Heat Advisory remains in effect for Yellowstone, Musselshell, Treasure, northern Big Horn, northern Rosebud, Custer, and Fallon Counties from 9 AM to 9 PM MDT Wednesday. If you have outdoor plans anywhere over the lower elevations Wednesday, but especially in the counties listed above, make sure to take the necessary precautions to prevent heat related illness.

With the heat, the forecast remains mostly dry. However, high resolution models continue to show a weak signal for isolated mountain showers/thunderstorms today, but any convection that does develop will have to compete with very warm 700mb temperatures. Therefore, we are not expecting much in the way of precipitation today. On Wednesday, a shortwave trough and associated cold front look to move into and through the region during the late afternoon and evening. With this, scattered high-based showers and isolated thunderstorms (some potentially dry) are forecast. With the warm 700mn temperatures, convection will be limited, but high resolution models continue to point towards some activity developing. The warm and dry conditions will also favor gusty and erratic winds with any shower or thunderstorm that forms. This is something to watch for outdoor activities and fire, as there is a low, but non-zero chance of dry lightning during the afternoon and early evening. By later in the evening, the lower atmosphere looks to moisten enough to end the dry thunderstorm threat. Arends

Thursday through Tuesday A weak upper trough will track across Wyoming Thursday while another upper trough drops out of Canada and tracks across north eastern Montana. The associated cold front will push through and drop temperatures 10 to 15 degrees from Wednesdays triple digit readingsand ultimately cool off the region so that temperatures on Friday only reach the mid to upper 70s.

Primarily height falls and accent are not generated until Thursday night into Friday morning. The latest model run has backed off somewhat on overall precipitation. However, probabilities for a quarter inch or more of rainfall Thursday night into Friday morning range from 20 percent over most of the lower elevations to 45 percent over the higher terrain and SE corner of the state. There is even a slight chance of seeing a little bit of snow over 10k feet in the Beartooths. The precipitation is progged to move out of the area by Friday afternoon with the exiting trough.

By the weekend, flat west to northwest flow prevails over the region. This pattern will have downslope flow bumping temperatures back up to around or even above normal for the weekend into early next week (mid 80s to lower 90s). The downslope will also keep us mostly dry as PWATs remain below 0.80 inches through the weekend before slowly climbing back by next Monday. Ensembles hint at a low amplitude trough moving through the region by Tuesday / Tuesday night time frame with an increasing chance of showers. However, cluster analysis suggests confidence is below average due to relatively wide spread in the ensembles 500 mb pattern. So any rainfall early next week still remains questionable. BT

AVIATION

VRF conditions will prevail through the TAF period. By Wednesday afternoon and evening, isolated, mostly dry showers and thunderstorms could produce gusty, erratic wind gusts. Arends

BYZ WATCHES/WARNINGS/ADVISORIES

MT...Heat Advisory in effect from 9 AM to 9 PM MDT Wednesday FOR ZONES 29>33-57-173-235. WY...None.