977 FXUS65 KGJT 030001 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 601 PM MDT Wed Jul 2 2025 .KEY MESSAGES... - Showers and thunderstorms have begun to develop over higher terrain this afternoon. Lightning and outflow winds capable of gusting in excess of 50 mph are the primary concerns. - With rich moisture in place and slow storm motions expected, heavy rain and localized flash flooding threats will be on the increase today and tomorrow. - Near to below normal temperatures are expected through Friday, then a gradual warming and drying trend will last through the holiday weekend. && .SHORT TERM /THROUGH THURSDAY/... Issued at 328 PM MDT Wed Jul 2 2025 Earlier this morning, widespread cumuli developed along the high terrain, and many thunderstorms have begun to form across our southern CWA. As cells tap into the steadily increasing moisture, expect for additional storm development throughout the afternoon. Upper-level flow does remain weak given our position under the western edge of a broad ridge though. This should limit the lifespan of today's storms and keep them fairly slow-moving, similar to yesterday. Beyond this, while small hail and gusty outflow winds will again be possible today, the 18Z sounding is hinting at an environment noticeably lacking in instability. High-resolution models yesterday did anticipate a dip in CAPE today, but we are even falling short of those estimates. This is partly due to cooling surface temperatures from early day cloud cover, and some warming in the mid-level atmosphere. PoP's are down as a result, though isolated, stronger convection remains possible. Tomorrow looks to be much more potent for active weather as PWAT's quickly rise to 180-210% of normal. This comes with the passage of a shortwave trough through the Intermountain West and resultant beneficial upper-level support. We'll likely see the bulk of moisture move overhead overnight. This actually threatens to inhibit the storm setup tomorrow should clouds linger into the morning thanks to the added moisture, which is expected as of this moment. While this won't change the high likelihood of widespread wetting rain, it could considerably alter the organization of tomorrow's storms. A more stratiform type event would become more favorable should morning cloud cover hamper the development of deep afternoon instability. Stronger cells embedded within stratiform rain would be possible, albeit more isolated. Should clouds break during the morning though, a more convective event would become more probable, but with the way models have been trending, this appears to be the less likely scenario. Regardless of how storms are characterized tomorrow, the widespread nature of precipitation will pose an isolated flash flood threat over prone locations. Portions of the CWA are under a marginal excessive rainfall risk tomorrow as a result. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Issued at 328 PM MDT Wed Jul 2 2025 High pressure begins to return to the lower levels on Friday as broad high pressure begins to build across the Four Corners, thanks to consistent southwesterly flow at all levels. Our brief wet spell/cool down will continue Friday afternoon for much of the CWA outside of the Four Corners, where warm dry air invades and temperatures begin to recover towards three digits. Leftover moisture will get reworked on much of our terrain Friday afternoon and produce more showers and thunderstorms. Depending on soil saturations from Thursday, this could produce some more hydrology concerns on a local scale Friday afternoon. For those enjoying Independence Day in the wild, staying abreast of local forecasts is advised, especially where flood and lightning prone terrain is involved. Dry air will continue to spread across the region Friday night. Showers and storms should all be wrapped up around midnight. High pressure and dry air exert enough influence Saturday to produce a mostly hot and dry forecast across the CWA. The terrain immediately west of the Divide and north of highway 50 could see an isolated shower or two pop up Saturday afternoon. Varying degrees of subsidence pose high uncertainty in shower coverage Saturday on the terrain. Dry boundary layers will likely keep much of anything from reaching the surface, aside from gusty outflow winds. This should feel familiar, as we've held on to this same basic regime the past week ahead of the current moisture surge. Sunday and beyond, models are bullish for high pressure building over the Southwest. Some extra-tropical moisture starts to bubble under the high from the south. This returns non-zero afternoon precipitation chances to the CWA Sunday into Wednesday. According to guidance, temperatures closer to the high pressure center push well above 100 early next week around the Four Corners. Elsewhere, we expect temperatures in excess of 7-10 degrees over climatology during this warm up. Light winds under the high will keep critical fire weather conditions under thresholds, but hot and very dry conditions will persist. Showers and thunderstorms that arise will continue to produce gusty outflow winds and potential dry lightning. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 548 PM MDT Wed Jul 2 2025 Today's showers and thunderstorms will gradually diminish across the region. The most impactful precipitation is expected to end after 02Z. Isolated showers are possible in the area overnight, but TAF site impacts are not anticipated to return until tomorrow morning and afternoon. After 12Z precipitation will begin to move into eastern Utah from the southwest. After 18Z impacts spread across the region. Possible impacts with showers and storms include brief periods of heavy rain, lowered ceilings, strong wind gusts, and lightning. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...BW LONG TERM...LTB AVIATION...TGJT |