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Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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880 FXUS65 KCYS 180939 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 339 AM MDT Sun Aug 18 2024 .KEY MESSAGES... - Hot and (generally) dry conditions will persist across much of the area today. A couple of high based showers or storms cannot be entirely ruled out later this afternoon or this evening across southern and eastern areas. While strong gusty winds would be the primary hazard, any developing storms in western Nebraska could be associated with a risk for small hail as well. - A break down in the upper-level ridge will yield a good chance for showers and storms across much of the area on Monday. The threat for widespread organized severe storms is low, but a strong storm or two is still possible. - Seasonable temperatures will continue through the period. Showers and thunderstorms will be most likely for Wednesday through Friday, with less coverage for Tuesday and Saturday. && .SHORT TERM /THROUGH MONDAY NIGHT/... Issued at 314 AM MDT Sun Aug 18 2024 Hot and generally dry conditions will persist across much of the area today w/ upper-level ridging remaining in control with 700- millibar temperatures of +16 to +18 deg C across the CWA. Should see the majority of areas along/east of I-25 in the 90s again w/ 80s west, although there will be at least some potential for mid and upper level cloud cover to hold us back a few degrees as 500 millibar vort energy undercuts the ridge. Profiles look to be on the dry side today w/ notable subsidence present on all guidance and little support for convection from the CAMs as a result. NBM guidance remains quite puzzling with 40+ percent PoPs across our southern zones this afternoon and evening, but do not see really any support at all for this in QPF fields or CAM reflectivities. Have maintained some very low 15-20 percent PoPs over our south/ east between 21z-06z as a high-based shower or weak storm cannot be entirely ruled out w/ the energy aloft, or in the vicinity of the retreating dryline over the western Nebraska Panhandle later this evening. If any storms can manage to develop, would believe the primary hazard would be strong wind gusts 55-65 MPH with the high cloud bases, but MLCAPEs around 1000-1500 J/kg and vertical shear profiles could support a stronger/organized updraft or two capable of producing hail as well. This threat is expected to be highly conditional. Larger-scale ridging will break down Monday, with strong southwest flow aloft giving way to improved moisture profiles and cooling thermal profiles aloft contributing to much weaker capping. As such, numerous showers and storms appear very likely on Monday and Monday night. The overall threat for strong to severe storms is low, but not zero as continued steep low/mid level lapse rates support sufficient instability for more robust updrafts. Shear profiles will not be quite as good as Sunday but flow aloft should still support around 35 knots of 0-6 km shear. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Issued at 314 AM MDT Sun Aug 18 2024 Tuesday...Atmospheric moisture decreases to 0.4 to 0.8 inches. With less atmospheric moisture, ridging and warm temperatures aloft producing convective inhibition, it looks mostly dry. High temperatures from the mid 80s to upper 90s with 700 mb temperatures near 18 Celsius. Wednesday...Although ridging aloft continues, precipitable water values will increase to 0.8 to 1.4 inches. Thus, it looks like widely scattered to scattered late day showers and thunderstorms, most numerous near the Colorado state line and west of a Douglas to Kimball line. 700 mb temperatures remain near 19 Celsius, yielding maximum temperatures from the mid 80s to near 100 degrees. Thursday...The ridge axis aloft moves further east over the Central Plains states, with an increase in atmospheric moisture for our counties, thus providing more fuel for scattered afternoon and evening showers and thunderstorms, most numerous near the Colorado state line. With more cloud and precipitation coverage, temperatures will be somewhat cooler. Friday...Moist southwest flow aloft continues with another round of scattered afternoon and evening showers and thunderstorms, most common near the Colorado state line. Slightly warmer with 700 mb temperatures near 15 Celsius. Saturday...Southwest flow aloft continues, though atmospheric moisture decreases slightly, thus coverage of late day showers and thunderstorms will decrease somewhat. Maximum temperatures will be similar to those of Friday. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1133 PM MDT Sat Aug 17 2024 Ridging aloft will continue. Scattered to broken clouds from 9000 to 25000 feet will prevail. Winds will gust to 20 knots at Chadron until 17Z, to 22 knots at Rawlins and Laramie from 18Z to 03Z, and to 26 knots at Alliance and Sidney after 22Z. Low level winds shear occurs at Scottsbluff until 08Z. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...CLH LONG TERM...RUBIN AVIATION...RUBIN