Area Forecast Discussion · National Weather Service Grand Junction (GJT) · issued Monday, July 27 at 2:31 PM MDT.
Revised in 5 passages since the 11:38 AM discussion. See every revision.
Messages
Warm overnight lows and triple digit highs for portions of eastern Utah and western Colorado are expected through Tuesday morning. The Heat Advisories remain in place.
Afternoon and evening showers and storms will continue thanks to ample moisture and daytime heating.
Slow storm motions will allow heavy rain under the stronger cells. Small hail and gusty outflow winds will also be possible.
Watch out for flash flooding and debris flows in vulnerable terrain, especially for areas near and downstream of burn scars.
Discussion
High pressure centered to our southeast, and the resultant southwesterly flow over our area, continues to advect monsoonal moisture into our forecast area. Storm motion is forecast to remain slow while ridging is aloft. At the same time, this mornings sounding shows that precipitable water remains well above normal for this time of the year, and there is an increase in instability when compared to yesterday. So, expect another day of slow moving storms capable of producing heavy rainfall. This means flooding and debris flow concerns remain elevated, especially over our recent burn scars. Lightning, small hail, and strong outflow winds are also concerns with thunderstorms.
Highs remain anywhere from 5 to 10 degrees above climatological norms with 100s still in the forecast for many lower elevations. Overnight lows will drop, obviously, but still remain above normal and without much relief, the going Heat Advisory remains in effect for the Grand Valley and Lower Yampa River Basin through tomorrow morning.
Looking ahead, a shortwave looks to move across the area Wednesday. If this should occur, thunderstorm chances will become more widespread, and potential for some stronger thunderstorms would increase. Keep an eye on the latest forecast. After that, high pressure continues to be forecast to build in to our west. Flow around the high will cause moisture to slowly decrease which will temper convection across the region.
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