Area Forecast Discussion · National Weather Service Grand Junction (GJT) · issued Sunday, July 26 at 1:02 PM MDT.
Revised in 5 passages since the 11:41 AM discussion. See every revision.
Messages
A Heat Advisory is in effect for many of the lower desert valleys of Eastern Utah and Western Colorado through Tuesday morning for triple digit highs and extremely mild overnight lows in the 70s and 80s.
Showers and storms will develop each afternoon/evening for the foreseeable future.
Heavy rain remains the primary threat of storms across the region. Gusty outflow winds and hail are likely in stronger cells as well.
Watch out for flash flooding and debris flows in vulnerable terrain, especially for areas near and downstream of burn scars.
Discussion
There's little change in the day-to-day forecast as high pressure remains in control through at least early next week. This keeps temperatures 5-10 degrees above normal, with triple digits in the lower elevations each afternoon. Moisture will also remain elevated, with precipitable water around an inch through the rest of the week. Unfortunately, this combination will lead to some very uncomfortable days ahead, as evaporative coolers struggle to work efficiently and overnight lows refuse to cool, remaining 10-20 degrees above seasonal norms. As a result, a Heat Advisory has been issued for the lower elevation zones of eastern Utah and for the Grand Valley and the Lower Yampa River Basin, lasting through 6AM Tuesday morning.
Additionally, daily heating will act on the ample moisture in place to fire convection over the higher terrain. Storm motion will continue to be slow, keeping the threat of heavy rain and flash flooding in the forecast, especially over sensitive terrain and recent burn scars. Lightning and gusty outflow winds will also be threats with any storms. This convection could move out over the adjacent valleys later in the day, before activity starts to dwindle after 9PM or so. Remember to stay up to date with the forecast if travelling across the region, especially across the higher terrain, and have multiple ways to receive urgent warnings.
The high begins to shift south and westward through the latter half of the week as a weak upper level trough tracks across the Northern Rockies. Some jet energy associated with the passing wave could create an environment favorable for strong thunderstorms, with possible large hail and stronger outflow winds. Stay tuned to see how this develops over the coming days.
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