Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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551 FXUS65 KGJT 241721 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 1121 AM MDT Mon Jun 24 2024 .KEY MESSAGES... - A rinse and repeat pattern will continue this week, with temperatures 5-10 degrees above normal and afternoon mainly afternoon/evening showers and thunderstorms over higher terrain. - A push of deep subtropical moisture is expected to move in at mid week, bringing a return to widespread thunderstorms with an increasing flash flood threat. Drying will follow for the weekend. && .SHORT TERM /THROUGH TUESDAY/... Issued at 414 AM MDT Mon Jun 24 2024 Showers and thunderstorms have dissipated over the forecast area in the early morning hours. However, a disturbance moving through the northern Wasatch has caused showers and a few thunderstorms to redevelop. It`s unclear at this point whether this activity will hold together as the disturbance pushes across the Green River toward sunrise. Precipitable water (PW) in the 00Z/Mon sounding at KGJT dipped to 0.67" from 0.94" Sunday morning finally bringing the drying models had been touting over the past several runs. HREF indicated that PW will remain largely unchanged today and Tuesday as the broad area of high pressure stretching from the Gulf States to southern California will inhibit moisture from infiltrating the area early this week. Consequently, isolated to scattered showers and thunderstorms are expected from late morning through early evening today and Tuesday, mainly impacting higher terrain. Reduced moisture in the column limits the potential for heavy rain while drying in the subcloud layer shifts storm characteristics toward stronger downbursts/outflow winds. Meanwhile, increased solar insolation will result in increased temperatures today with even warmer highs on Tuesday. Diurnal cooling in the absence of upward forcing tonight will cause moist convection to dissipate early this evening. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Issued at 414 AM MDT Mon Jun 24 2024 With the high pressure having moved a bit northward over Colorado, the weak circulation around the high begins pulling the deep moisture over southern Arizona north into Utah and northern Colorado with IVT`s of 414-300 kg/m/s Tuesday night into Wednesday peaking around 500 kg/m/s Wednesday night into Thursday. With the weak flow around the high, this would say that there must be a lot of water in this stream, hence pwat`s jump back to over an inch Wednesday peaking at about 1.5 inches early Thursday. Look for widely scattered showers and thunderstorms initiating late Wednesday morning becoming widespread through the afternoon. CAPE looks to run 500 to 1000 J/kg indicating deep convection with possible isolated large hail. With the weak flow aloft, flash flooding concerns across the region return with slow moving/training showers and thunderstorms through the afternoon and overnight Wednesday. At the same time, the deep cold low that has been spinning off the Pacific Northwest Coast finally moves inland to track across Montana and the Dakotas late Thursday into Friday with the trough brushing the northern boundary of eastern Utah and Western Colorado. With the pressure gradient increasing aloft, look for increased shear generally along and north of the I-70 corridor Thursday afternoon and evening spawning the potential for severe thunderstorms across the northern areas with large hail, damaging winds the primary threats. It`s really too soon to make the call, but this is something to watch. Can`t rule out this area of severe weather spreading south into the central areas overnight. Models were showing a dryline pushing through early Friday sweeping the moisture out of the region, but don`t show a thermal gradient/cool front one would expect with this boundary. Likely this is just the models wanting to dry out the region like they`ve been doing the past couple weeks. More probable, the moisture will linger with scattered afternoon and evening showers and thunderstorms Friday through the weekend. With the heavy cloud cover limiting diurnal heating, temperatures will fall to near normal to a little below normal Thursday and Friday. As the skies clear out over the weekend, temperatures climbing back to five to ten degrees above normal by Sunday. The question on everyones mind is whether this weather has anything to do with "the M-word." Some are asking if we`ve been in it now for a week or so since we have had tropical moisture move up, but it`s been blamed on remnants of a tropical storm and not "the M-word." Models show the high pressure setting up strong over Texas and troughing/low pressure off Baja, which looks like... Well, if it walks like a duck and talks like a duck... && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1118 AM MDT Mon Jun 24 2024 Afternoon showers and thunderstorms are expected over the next 3-6 hours across the higher terrain of eastern Utah and western Colorado. These should mainly impact higher terrain terminals, but even lower elevation terminals may see showers or storms in the vicinity at some point. Main threats will be gusty winds, brief heavy rain, and lightning. These should diminish after sunset, with skies clearing and typical terrain driven winds kicking in. Tomorrow is expected to be very much the same, with a clear and quiet morning giving way to afternoon showers and storms. VFR conditions will prevail for the next 24 hours, but impacts from showers or storms passing over a terminal will lead to the potential for brief drops to MVFR conditions and possibly drops below ILS breakpoints. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...NL LONG TERM...DB AVIATION...TGJT