030 FXUS65 KCYS 150541 AFDCYSArea Forecast Discussion National Weather Service Cheyenne WY 1140 PM MDT Sun Sep 14 2025
.KEY MESSAGES...
- Showers and isolated thunderstorms will continue over far eastern Wyoming and western Nebraska through the early evening.
- Warmer temperatures are expected Monday with a few isolated PM showers and thunderstorms capable of producing gusty winds.
- Another cold front will push across Wyoming on Tuesday, resulting in cooler temperatures and a daily chance for showers and isolated thunderstorms.
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.SHORT TERM /THROUGH TUESDAY/... Issued at 300 PM MDT Sun Sep 14 2025
The latest GOES satellite imagery shows the upper level low circulating near the Nebraska/South Dakota border as it lowly ejects to the northeast. Fairly potent low to mid-level isentropic lift / positive theta-e advection has been analyzed over western Nebraska, which is supporting ongoing shower activity in this area. However, this forcing is on a weakening trend, and should be gone by about 6 to 7 PM or so. However, modest instability remains in the wake of the system over the High Plains. SBCAPE is around 500 to 1000 J/kg, and we have fairly decent low level convergence providing some forcing over Platte, Goshen, and Laramie Counties as well as into the Nebraska panhandle. Most of this convection is fairly low- topped, and thus the probability of severe weather is quite low. Still, we could see some isolated gusty winds and pea sized hail. Surface vorticity in place also means a brief, weak landspout can`t be ruled out. Expect clearing skies overnight tonight as this system finally departs.
The weather pattern will remain active heading into Monday. The next upper level low is already apparent moving over the Pacific Northwest this afternoon. A transient ridge will move over the area tonight into Monday ahead of this next system, supporting one warm day in between systems. West-southwest flow aloft will support warm air advection across the area, boosting temperatures back above average for this time of year. Dry air will also work in tonight, but moisture advection aloft is expected to return as early as late morning Monday. Forecast soundings show fairly dry inverted-vs in the low levels with moisture increasing aloft overtop of the dry boundary layer. With some weak forcing anticipated, we should be looking at isolated to widely scattered high based showers and thunderstorms moving rapidly across the area ahead of the upper level low. Coverage is not expected to be all that high, but we will need to watch for strong gusty winds with this activity due to the dry low-levels and fairly strong winds (for this time of year) aloft.
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.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Issued at 300 PM MDT Sun Sep 14 2025
Tuesday...The shortwave trough aloft moves overhead near peak heating, sparking scattered showers and thunderstorms in the afternoon and evening. Somewhat cooler in the wake of a cold front and with more cloud cover and precipitation coverage.
Wednesday...The next shortwave trough aloft moves across Wyoming, and with adequate low and mid level moisture, we expect to see scattered afternoon and evening showers and thunderstorms. Somewhat cooler with extensive cloud cover.
Thursday...North flow aloft develops, with drier air moving in at low and mid levels, producing a drier day. 700 mb temperatures near 5 Celsius will produce a warmer day.
Friday...Somewhat drier air moves in with northwest flow aloft, producing a dry day. 700 mb temperatures rise slightly, producing a warmer day.
Saturday...Ridging aloft builds over western Wyoming. We may see isolated late day showers and thunderstorms with just enough low and mid level moisture.
Sunday...Northwest flow aloft continues, and with enough low and mid level moisture, we anticipate isolated to widely scattered afternoon and evening showers and thunderstorms. 700 mb temperatures near 12 Celsius will yield maximum temperatures in the 70s.
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.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1140 PM MDT Sun Sep 14 2025
Dry westerly flow aloft expected for Monday over southeast Wyoming and western Nebraska with a lower chance for showers and thunderstorms Monday afternoon. Another period of unsettled and cool weather is expected Tuesday and Wednesday as Pacific system moves into the region and stalls.
HAZARDS/WEATHER TRENDS: VFR conditions expected over the next 24 hours. There is a small chance for a few thunder showers after 18z Monday, but coverage is expected to be limited (~10% to 20%)...so will leave out any mention in the TAFs for now.
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.CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None.
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SHORT TERM...MN LONG TERM...RUBIN AVIATION...TJT
NWS CYS Office Area Forecast Discussion