Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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588 FXUS65 KGJT 070514 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 1114 PM MDT Thu Jun 6 2024 .KEY MESSAGES... - Hot and dry into weekend, with desert valleys approaching 100. - Mountain showers and thunderstorms develop Friday afternoon. A few storms will produce strong outflow gusts. - Low valleys remain warm and dry, while afternoon mountain showers and thunderstorms remain a threat into the early half of next week. && .SHORT TERM /THROUGH FRIDAY/... Issued at 229 PM MDT Thu Jun 6 2024 Warm and dry conditions continue on the West Slope this afternoon. Relative humidities in the teens under a broad ridge of high pressure are keeping skies mostly clear, aside from a cloud or two forming on terrain features, where melting snow continues to produce some localized moisture. A couple of weak shortwaves push across the Great Basin this evening and overnight. This will cut into the ridge`s amplitude and begin to whittle away its stranglehold on the region.(more to follow on this) Likewise, southward over Baja Mexico, a cutoff low will do its best to send some weak moisture up across the Four Corners on Friday. Some model guidance had temperatures surging north of 100 Friday afternoon. Some cloud cover and less subsidence from the flattening ridge looks like the early forecasts were a touch aggressive. Followed this morning`s shift and backed off of the highs a touch. Still looks like much of the lower deserts of southeast Utah will come pretty close to triple digits tomorrow, while across the state line we`ll stick around the upper 90`s tomorrow in our low valleys. Up the hill, high temperatures will depend on the depth of cloud cover and any shower activity we see Friday afternoon. Temperatures will still hover around 10 degrees over early June climatology. Shower development Friday afternoon will favor terrain features, then shift more widespread across the northern half of the CWA thanks to another weak shot of moisture pushing through on a series of shortwaves. Some scattered convection is expected, with storms capable of dropping some strong wind gusts into the dry boundary layer at the surface. A few showers will likely continue into the overnight hours Friday night, but meager moisture supplies probably will keep things mostly cloud cover and a few showers on the terrain of northwest Colorado. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... Issued at 323 AM MDT Thu Jun 6 2024 The relocation of the SubTrop High from the Desert SW to the Southern Plains will be complete by early Saturday. Easterly flow around the southern periphery of this High will begin to transport Gulf of Mexico moisture back toward our southern CWA...which gets enhanced later in the day as a cold front dives along the lee of the Rockies into New Mexico and the upslope flow drives it through the gaps. Finally...a low pressure system will be drawn northward out of the Baja region on Sunday into Monday tapping into another moisture source with a Pacific origin. The bigger picture of this is PWAT is pushed up to near and above 3/4 of an inch for the weekend into early next week...which for early June is in the region of the 90th percentile. The moisture will help fire daily afternoon thunderstorms while also easing the temperatures back a bit each day back to just a single digits above normal instead of 10 to 15 degrees. With the higher then normal moisture in the profile there will be a threat of some of the organized storms producing moderate to maybe even heavy rainfall rates. However sounding profiles in the lower to mid elevations suggest gusty outflow winds will likely be more of a threat than wetting rainfall. Sunday afternoon looks to be the peak of the convective activity as the Baja low rotates south of the 4 Corners. As we get later into the week the SubTrop High looks to try and re-establish itself over the Desert SW with greater uncertainty on where the next cutoff low in the SoCal/Baja region will reside. Moisture will begin to wane by Tuesday with afternoon storms mainly becoming focused on the higher terrain. The decrease in moisture and storms will allow the temperature trend to increase with highs once again approaching the triple digits in the lower desert valleys by midweek. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1114 PM MDT Thu Jun 6 2024 VFR conditions and light winds will occur through late morning on Friday. Afternoon breezes and the chance of passing thunderstorm will increase through the afternoon at most TAF sites. Confidence remains low on direct impacts to the airfield due to isolated storm coverage. Gusty winds will be the main threat and may occur from outflow from distant storms. The probability of below VFR remain very low however. && .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...and it`s melting...fast. As a result, creeks, streams and major tributaries along the Upper Colorado River Basin are on the rise. Seasonal peak flows are expected over the next 10 days, with the Upper Gunnison, Upper Yampa and Colorado Headwaters basins likely peaking for the season this weekend. Current guidance oscillates diurnal peaks cresting the Action Stage for portions of Gore Creek and Eagle River in Eagle County. No highlights needed, yet, for that area after discussion with local officials but we will keep an eye on things over the coming days. The Elk River near Milner in Routt County, on the other hand, is expected to exceed Minor Flood Stage each morning through Sunday. This increase in forecast stage/flow warranted an upgrade from Flood Advisory to a Flood Warning. Also, the East River near Almont is forecast to exceed Action Stage each morning through Sunday, with the potential for exceeding Flood Stage by Saturday. For now, a Flood Advisory is in effect for this stretch of river. However, stay tuned for the potential upgrade to a warning and/or extending the advisory downstream into the Gunnison at Gunnison. 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...LTB LONG TERM...15 AVIATION...GJT HYDROLOGY...ERW