Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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325 FXUS65 KGJT 041724 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 1124 AM MDT Tue Jun 4 2024 .KEY MESSAGES... - A few light showers will be possible over the northern and central mountians through about midday today, but will taper off this afternoon as high pressure and drier air builds in. - Some of the hottest temperatures of the year so far are expected late week, with highs running 10-15 degrees above normal, and triple digits likely for the lower desert valleys. - Chances of mountain showers and storms will return for the weekend into early next week. && .SHORT TERM /THROUGH WEDNESDAY NIGHT/... Issued at 300 AM MDT Tue Jun 4 2024 With the surface front just about through the area, shower activity has decreased quite sharply across the area. Generally, only areas along the Divide are still seeing rain showers, and these are expected to come to an end over the next few hours. With 700-500 mb mixing ratio guidance indicating a lingering pool of moisture over the northern and central Colorado Divide mountains, as well as some modest CAPE thanks to steepening mid-level lapse rates in the post- frontal regime, chances for isolated to scattered showers will be possible over this area through the mid-morning hours. Northwesterly flow aloft will quickly bring in some drier midlevel air that will erode these lingering pockets of moisture through the day, tapering off any shower activity by the afternoon hours and bringing gradual clearing from west to east through the day. High temperatures will run near to maybe a degree or two below highs yesterday...but still remaining 5 or so degrees above normal for early June. Clear skies and light winds tonight will allow radiational cooling to do its job and drop low temperatures to near normal values. Ridging building into the Desert Southwest starting tonight will kick off a warming trend, with high temperatures tomorrow running a good 10 degrees above normal. Parts of southeast Utah will likely see their first triple digit day of the year, with the rest of the desert valleys seeing mid to upper 90s. Higher elevation valleys will see highs in the 80s, while mountain towns are looking at upper 60s to 70s. A shortwave passing by across Wyoming may tighten the gradient aloft enough to bring some increased gusts up to 30 mph across northeast Utah and northwest Colorado, but otherwise, look for clear skies and light winds to characterize the day Wednesday. && .LONG TERM /THURSDAY THROUGH MONDAY/... Issued at 300 AM MDT Tue Jun 4 2024 The big story in the Long Term is the heat that will make it feel like Summer already across the Western Slope for the first full week of June. A ridge of high pressure builds across the area with its axis sliding overhead by Thursday. The flow will turn southerly by Friday ushering in strong WAA and some of the hottest temperatures of the year thus far. Basically from Thursday through Saturday, high temperatures across the area will exceed 10 to 15 degrees above normal with triple digit heat seeming more like a near certainty for the lower valleys of west-central Colorado (Grand Valley) as well as east-central and southeast Utah. High temperatures seem to peak on Friday as there is potential for some subtropical moisture to advect northward heading into the weekend and early next week. Mid to upper 90s will be felt across the Uinta Basin, Delta and Uncompahgre River Basin, up through Debeque Canyon to Rifle and the valleys across southwest Colorado. So, all in all, it will get hot quickly making it all the more important to stay hydrated and take it easy in this heat, whether doing work or recreating outdoors or even trying to stay cool indoors. The latest NBM probabilities of exceeding 99 degrees (so basically reaching 100 or more) is near 100% for Moab and portions of east-central and southeast Utah with most of that area greater than 90%, while the Grand Valley is over 80% and Delta to Hotchkiss is around 60 to 80% depending on where you are. While higher confidence exists for the heat, what is less certain is the eventual advection of subtropical moisture and how that impacts our area. It all has to do with the evolution of a cut off low that will be sitting over the Baja Peninsula underneath this high pressure ridge. The ridge axis largely remains firmly in place over the spine of the Rockies this weekend with a trough moving into the Pacific Northwest and the cut off low either remaining over the Baja/SoCal region or getting absorbed in the flow and pulling through our neck of the woods by late this weekend into early next week by this PacNW trough as it tracks inland. It does appear like Thursday and Friday will remain dry. There might be some isolated storms Friday afternoon over the western Colorado mountains along the Divide or at the very least cumulus buildups as this subtropical moisture tries to work its way northward. It seems like guidance is honing in on the development of afternoon convection at least over the high terrain this weekend, potentially expanding in coverage Sunday into Monday, depending on if this cut off low is absorbed and tracks across with the embedded shortwaves from the PacNW trough. There is lots of uncertainty this weekend into early next week as models are not in great agreement on how this plays out with the different scenarios listed above. At the very least, afternoon convection favoring the high terrain seems like a good compromise with the lower valleys remaining drier, given the drier low levels and lower confidence. If this wave tracks across the area, the lower valleys could see some storms and precipitation but gusty outflow winds seem like the better bet and more probable outcome. The heat remains through this weekend with near record heat possible, although could turn slightly cooler early next week if it becomes more unsettled (and by cooler I mean 90s for the lower desert valleys instead of 100s and 80s for the rest of the valleys instead of 90s...still 5 degrees above normal for early June). Projections beyond the uncertainty this weekend into early next week seem to indicate potential for a strong ridge to build back over the west and into our area for mid June, as is more typical this time of year...meaning drier and hot (warmer than normal). The CPC outlooks would seem to agree with this scenario. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1120 AM MDT Tue Jun 4 2024 Skies will continue to slowly clear out as the afternoon progresses. Some broken skies continue along the Divide and near KHDN but satellite shows these skies becoming more scattered in nature and this trend will continue. Some gusty winds of 20 to occasionally 30 mph will be common this afternoon before dying down after 00Z. Skies will become clear overnight with VFR remaining the predominant flight condition. && .HYDROLOGY... Issued at 530 PM MDT Mon Jun 3 2024 High pressure building overhead through the end of the week will result in an unseasonably warm period across the Western Slope. Simultaneously, as those temperatures rise, so will the rate of snowmelt across our high terrain. Even though low to mid elevations have already melted out, there`s still an abnormally high amount of snow left over basins generally at and above 11,000 ft. As a result, we`ll see creeks, streams and major tributaries along the Upper Colorado River Basin rise. Seasonal peak flows are expected over the next 10 days, with the Upper Gunnison, Upper Yampa and Colorado Headwaters basins potentially peaking this weekend. Current guidance oscillates diurnal peaks cresting the Action Stage for portions of Gore Creek and Eagle River in Eagle County and the Elk River in Routt County Colorado. We will continue to monitor these evolving forecasts to see if any Flood products are warranted. But for now, we just want to pass on the message: As scorching temperatures lure folks to the water, please remember the potential hazards associated with high flows during the snowmelt season. Fast flows are not just dangerous for those choosing to float the rivers. In addition, high diurnal swings may drastically change the depth and flow for normally small creeks and streams. Swift currents and cold water temperatures can catch you off guard, so please be vigilant with current conditions and look for forecast updates when recreating or working near the water`s edge. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...BGB LONG TERM...MDA AVIATION...TGJT HYDROLOGY...ERW