Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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789 FXUS65 KGJT 141127 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 527 AM MDT Tue May 14 2024 .KEY MESSAGES... - Shower and thunderstorm activity is expected again today and will likely linger into the early morning hours of Wednesday. Gusty outflow winds in excess of 45 mph will be a threat with with storms this afternoon and evening. - Another round of storms occurs tomorrow as the troughing phases across the eastern Great Basin and Rockies. Temperatures look to drop to near or slightly below normal. - Drier and much warmer conditions are forecast to end out the week and persist into the weekend. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 259 AM MDT Tue May 14 2024 Water vapor imagery early this morning is showing a compact wave moving across western WY providing the ascent needed for nocturnal convection over our northern CWA. Dew points across the North indicate a slightly more favorable profile for getting measurable rainfall down to the valley surface. Satellite and radar imagery also show a plethora of outflow boundaries/weak gravity waves drifting southward which is helping to pop additional isolated storms south of I-70 into east-central Utah...but most of this shower activity has been unmeasurable. Models of course struggling a bit with this scenario and will likely be updating near term grids through the next several hours to keep up with reality. Planning on a downturn through the mid morning hours as weak subsidence behind the Wyoming wave briefly caps the atmosphere until we again hit the free convective temperature by mid day. This convection will be aided by the next wave in line moving into western Idaho attm which will track across our northern border by mid afternoon through the evening. Additional ascent will be focused across the central CWA by a strengthening jet streak as energy curves through the base of the parent trough to the North along with moistening mid level flow and orographics. The main threat from storms today will be the gusty outflow winds another warm day leading to a robust EML. These outflows are likely to keep the convection going well into the early morning hours such as the current situation...but where and when is a very low confidence forecast. By tomorrow another wave dropping down the backside of the trough departing into the Plains will phase with the southern stream low moving into the Desert SW. The forcing isn`t off the charts but conditional instability and terrain circulations will again lead to showers and storms popping by late morning and expanding through the afternoon. Temperatures the next few afternoons will be hampered just a bit by the clouds and better storm coverage. They should be the coolest of the forecast running a bit above normal today then near normal tomorrow. Clouds and outflows likely to keep another mild night in place tonight. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Issued at 259 AM MDT Tue May 14 2024 Wednesday afternoon`s shower and thunderstorm activity is expected to linger through the night as another lobe of energy tracks through the base of the trough overhead, dragging a weak boundary along with it. Activity is expected to linger longest along the Divide and across southwest Colorado, but will taper off after midnight as the entire system shifts to the east. At the same time, the cutoff low pressure that has been lingering over southern California will finally be absorbed into the base of the trough and will track eastward through the day Thursday. The best lift associated with this feature will track across the Desert Southwest, far enough south of the CWA to limit it`s influence. Only the San Juans are forecast to see any precipitation out of this event, with low-end PoPs in the forecast currently. The remainder of the area sees drier air and higher pressure build in on Thursday, with clearing skies and temperatures jumping around 5 degrees compared to the day before. This trend of drier and warmer weather will stick with us into the weekend, as high pressure remains in control. By Saturday, temperatures will be running around 10 degrees above normal, with the desert valleys seeing upper 80s to low 90s, the higher elevation valleys looking at 70s to low 80s, and the mountain towns seeing upper 50s to mid 60s. Overnight lows will also remain mild through the period. By Saturday, flow aloft will shift to southwesterly over eastern Utah and western Colorado as the ridge axis shifts east in response to a Pacific trough tracking across the Northwest. In addition, yet another cutoff low is forecast to be off the Southern California coast. This setup will allow that southwesterly flow to tap into some deeper subtropical moisture and begin advecting it into the region. This uptick in moisture on Saturday will bring the return of mountain showers and thunderstorms, although, with little upper level support, these showers will likely remain over the higher terrain and adjacent high valleys. For Sunday into the coming week, model guidance isn`t in the best agreement. The question is, how will the cutoff low be handled? Will it be quickly reabsorbed into the trough? Or will it linger and keep troughing overhead of the Western CONUS into the coming week? Only time will iron these questions out. As it stands, it does look like a more troughy pattern will return for the coming week, with slightly cooler and more unsettled conditions expected. && .AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 527 AM MDT Tue May 14 2024 VFR conditions should prevail over the next 24 hours even with passing showers and thunderstorms at times. ILS conditions could temporarily set up but it the gusty outflow winds that will be the main concern through the evening. Conditions will be favorable for gusts exceeding 45 mph in some of the outflows coming from storms but the probability of this occurring at a TAF site is less than 30 percent. Therefor VC has been been used in the forecast until confidence increases. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...15 LONG TERM...BGB AVIATION...GJT