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Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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498 FXUS65 KGJT 051145 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 545 AM MDT Wed Jun 5 2024 .KEY MESSAGES... - The warmup to well above normal temperatures begins today as high pressure builds overhead, providing mostly sunny skies and dry conditions with high temperatures rising to around 10 degrees above normal. - Some of the hottest temperatures 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 THURSDAY/... Issued at 311 AM MDT Wed Jun 5 2024 The warmup to well above normal temperatures begins today and lasts through this weekend, peaking on Friday with some of the hottest temperatures we have seen so far this year on the Western Slope. High pressure will continue to build over the Great Basin with a dry northwest flow overhead. High temperatures today will be about 5 degrees warmer than yesterday, with highs settling around 10 degrees above normal. Very little instability and moisture exists in this pattern with mixing ratios down to about 1 to 2 g/kg and CAPE basically non- existent, so like yesterday afternoon, do not expect any convection to fire over the high terrain, resulting in a quiet day. The winds will be breezy at times but lighter than previous days, with gusts to 25 mph possible at times, but not widespread by any means. The ridge moves overhead by Thursday, with highs jumping up another 5 degrees to end up 10 to 15 degrees above normal. Under this heat dome, strong WAA looks to take place, especially later in the week as the flow shifts to a more southwesterly direction. For Thursday though, we stand a good chance to see our first 100 degree day in the Grand Valley, or at least pretty close with triple digit heat more likely in the desert valleys of east-central and southeast Utah. The latest probabilities show the Grand Valley at a 50-60% chance of exceeding 99 degrees on Thursday with some lower desert valleys of east-central and southeast Utah at greater than 90% chance. When you change this value to greater than 98 degrees, that probability jumps up to 80% for the Grand Valley and near 100% for the lower desert valleys of east-central and southeast Utah. So, needless to say, confidence is high that highs will be near 100 degrees for these areas, if not upper 90s. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Issued at 311 AM MDT Wed Jun 5 2024 Thursday night sees the dome of high pressure firmly in place over the Desert Southwest while an area of cutoff low pressure lurks off the coast of southern Baja California. Despite the expected clear skies and light winds, the heat associated with this dome of high pressure will keep overnight lows 10-15 degrees above normal from Thursday night through the weekend. Likewise, daytime highs will soar for Friday, with the current forecast carrying upper 90s to low 100s for all of the desert valleys of eastern Utah and western Colorado. Multiple ensemble suites also are hitting on this unusual heat, with both the ECENS and NAEFS situational awareness tables indicating record high values against the 30-year climatology. In fact, for the Grand Junction Regional Airport, the record for June 7th, this Friday, is 100F. So we have a good shot of at least tying, if not breaking, this record. With such unusual early season heat, make sure to take precautions if spending time outside. Stay well hydrated, wear light colored and loose fitting clothing, and, if possible, stay somewhere cool during the hottest part of the day, whether that be in an air conditioned building or just in a shaded area out of the sun. These hot temperatures will stay with us through the weekend as the ridge of high pressure remains overhead, but a gradual cooling trend will start up on Saturday. Increasing moisture aloft as the clockwise flow around the high and counterclockwise flow around the previously mentioned cutoff low pumps some subtropical moisture northward will lead to increasing clouds and chances for mountain showers beginning Saturday afternoon. This will knock high temperatures down a few degrees compared to Friday. Passing weak shortwaves to the north of eastern Utah and western Colorado will add an occasional boost to storm coverage through the weekend. With dry surface air in place, the main threats with any showers or storms this weekend will be gusty outflow winds and lightning. By Saturday night, a Pacific trough approaches the West Coast and model agreement begins to fall apart on a lot of details. Looking at the broadest take on model guidance, the ridge axis should pass overhead on Sunday, while a portion of energy associated with that Pacific trough dives south and begins to cut off over the SoCal coast. Models are indicating a pretty good fetch of moisture making it into the Four Corners region during this period, so mountain showers and storms will remain in the forecast into early next week. As the California low continues drifting southwest, flow over eastern Utah and western Colorado becomes westerly to northwesterly, allowing some cooler air to build in. This, combined with increasing cloud cover and storm coverage, will allow high temperatures to drop to within 5 degrees of normal to kick of the coming workweek. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 545 AM MDT Wed Jun 5 2024 VFR conditions will prevail with clear skies under high pressure today. Winds will generally be light and terrain driven with occasional gusts 20 to 25 kts at times during the afternoon. && .HYDROLOGY... Issued at 229 PM MDT Tue Jun 4 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...MDA LONG TERM...BGB AVIATION...MDA HYDROLOGY...ERW