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Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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977 FXUS65 KCYS 121045 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 445 AM MDT Wed Jun 12 2024 .KEY MESSAGES... - Hot today. Scattered to numerous high-based showers and a few rumbles of thunder in the afternoon and evening, possibly associated with 45+ MPH wind gusts. - Widespread showers and thunderstorms are expected across the high plains on Friday. Some storms may be severe, with all hazard types possible. && .SHORT TERM /THROUGH FRIDAY/... Issued at 402 AM MDT Wed Jun 12 2024 A very hot day for much of the area w/ 700-mb temperatures of 16 to 18 deg C beneath quasi-zonal flow aloft. Members of both HREF and NBM spectrums suggest 20+ percent probabilities of exceeding 90 deg F for most areas along and east of I-25, with the highest probs along the Platte River Valley from Wheatland to Torrington to Scottsbluff and Bridgeport. A fair amount of mid & high level moisture will overspread the region today as numerous weak short waves traverse the flow regime, supporting potential for several high-based showers and storms through the afternoon/evening. The main concern w/ this activity should be strong wind gusts, given the very dry sub-cloud layer w/ LCLs above the 0 C level. Expect the increase in cloud cover & convective outflow to impact highs to some degree, but 85-95 deg F should still be easily achieved. The seasonable warmth persists on Thursday w/ potential for more robust convective activity focused along a frontal zone which is progged to be draped from northwest to southeast from central WY into the southern NE Panhandle. Low-level moisture pooling along this boundary with dew points near 50 deg F may support a narrow ribbon of up to 1000 J/kg CAPE immediately along the boundary w/ 45+ knots of effective bulk shear parallel the frontal zone from mid afternoon through early evening. This should support a mixed storm mode with multicell and embedded supercell structures with potential for marginally severe hail and wind. Any upward trends in the instability profiles would significantly increase concern for organized severe storms. Friday will be the more likely day for organized severe thunder- storms as a sharp, negatively tilted short wave lifts rapidly NE from the 4 Corners into the central Rockies. Significant surface cyclogenesis over eastern Colorado will give way to robust moist southeasterly flow supporting 50s to perhaps low to mid 60s dew- points in far southeast Wyoming, and especially the southern Neb Panhandle. This coupled w/ steepening mid-level lapse rates will support strong instability with 2000+ J/kg MLCAPEs. Veering wind profiles and persistent 35+ knot 500-mb flow will support strong deep layer shear favorable for supercell storm structures w/ all hazards possible, including potential for significant hail & the risk for a few tornadoes. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Issued at 402 AM MDT Wed Jun 12 2024 Headed into the weekend, the weather will quiet down as the shortwave responsible for Friday`s storms pushes eastward into the Central Plains. Weak ridging behind the shortwave on Saturday will advect +16C 700 mb temperatures into the CWA, leading to a toasty afternoon across the area with highs in the mid 80s to low 90s. Winds will turn more zonal late Saturday afternoon, leading to a windy afternoon and evening for areas west of the Laramie Range. Temperatures on Sunday will cool off a few degrees as a broad trough over the Pacific northwest begins to dive southeast. This will push slightly cooler 700 mb temperatures into CWA. Overall, conditions over the weekend look to remain dry. Could potentially see better precipitation chances for the start of the work week. Both the GFS and ECMWF have the trough moving across northern Wyoming Monday night into Tuesday. However, they both have the better moisture north of the CWA. Could possibly see some light precipitation develop across the area, but the low and mid-levels remain fairly dry. There is higher confidence in temperatures becoming colder as the trough drags a strong cold front along with it. Frontal passage Monday night could lead to high temperatures in the 70s on Tuesday. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1118 PM MDT Tue Jun 11 2024 Looking at a quiet overnight with mostly clear skies and VFR conditions. VFR conditions will continue into the day on Wednesday, but with gustier winds and increasing cloud cover during the afternoon. A slight chance of showers will be possible. && .HYDROLOGY... Issued at 342 PM MDT Tue Jun 11 2024 Flows remain just below flood stage on the Medicine Bow River near Elk Mountain with a slight trend downward the past few days with early morning crests. However, with the warm weather expected the next few days including overnight lows in the mid-40s at higher elevations, decided to extend the Flood Watch for snowmelt through Thursday morning. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...CLH LONG TERM...SF AVIATION...SF HYDROLOGY...MB