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492 FXUS65 KCYS 161137 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 537 AM MDT Mon Jun 16 2025 .KEY MESSAGES... - Coverage of showers and thunderstorms will increase for Monday and Tuesday with continued potential for scattered strong to severe thunderstorms and locally heavy rainfall. - Hot temperatures are expected through Monday before a modest cool down on Tuesday. Well above average temperatures are expected to return late in the week. && .SHORT TERM /THROUGH TUESDAY NIGHT/... Issued at 402 AM MDT Mon Jun 16 2025 An active next few days are expected as several upper-level shortwaves traverse the CWA. Each shortwave will help provide synoptic lift needed to generate storms across the area today and Tuesday. The weaker of the two shortwaves will move in from the west this afternoon, bringing with it some Pacific moisture. Models continue to show elevated dewpoints east of the Laramie Range, aiding in instability. Model soundings echo this, with environments favorable for severe weather across much of the CWA. Model soundings east of the Laramie Range show MUCAPE anywhere from 1400 to 2500 J/kg with effective shear values up to 45 kts. This will support a large hail threat in storms. DCAPE values across much of the CWA are also elevated, showing over 900 J/kg with even higher values in Wyoming, which will lead to threat of strong winds in storms. MLCAPE values, especially in the Nebraska panhandle and northern part of the CWA are also quite high, exceeding 1500 J/kg which could lead to an isolated tornado. However, it is worth mentioning that GFS soundings do show a capping inversion across the panhandle that is still present by mid-afternoon. This could limit both storm development and lifespan of storms moving into the panhandle. Hi-Res guidance like the HRRR shows only a few storms developing during the afternoon and clearing out during the evening hours. Earlier runs of the HRRR were a bit more aggressive and even had nocturnal storms developing late Monday night and continuing into Tuesday morning. The HRRR has since taken this out, but other CAMs like the RRFS develop this convection around 3 AM on Tuesday. The RAP, on the other hand, shows the cap eroding, with models like the MPAS developing a widespread line of storms during the afternoon. As previously mentioned, cannot rule out nighttime convection as models sustain MUCAPE values over 1200 J/kg for areas east of the Laramie Range. However, models are fairly split on whether or not this convection will occur. Tuesday will be another active day as a stronger shortwave moves across the Rockies. Once again, model soundings favor a severe environment with Hi-Res guidance showing a line of storms developing over the Laramie Range early in the afternoon and blasting across the CWA through the evening hours. A line of storms will favor more of a strong wind threat, however, isolated large hail will be possible with up to 2000 J/kg of MUCAPE with around 30 kts of effective shear. A few lingering storms will be possible behind the main line, but all storm activity will likely be done by midnight Tuesday night. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Issued at 402 AM MDT Mon Jun 16 2025 Warmer, drier and quieter weather is expected in the long term as a ridge of high pressure sits over western CONUS. By Thursday evening, 700 mb temperatures will rise to +18C, which is in the 97th percentile and above according to NAEFS climatology. These 18C temperatures will continue through Saturday, leading to well above average high temperatures. Some locations may creep into the 100s on Friday and Saturday, with widespread 90s expected across most of the CWA. High temperatures will be anywhere from 10 to 15 degrees above average for mid-June. Precipitation chances through Saturday will be on the low side as subsidence under the ridge keeps skies sunny and conditions dry. Precipitation chances could return Sunday night with an incoming trough. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 537 AM MDT Mon Jun 16 2025 Scattered showers and thunderstorms are expected across portions of the forecast area this afternoon and evening. Terminals east of the Laramie Range are most likely to be affected by storms, with moderate rain potentially causing brief visibility drops. Storms may also contain damaging wind and hail. Storms will end this evening, but nocturnal convection cannot be ruled out, with low CIGs potentially developing early Tuesday morning. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...SF LONG TERM...SF AVIATION...SF