Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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931 FXUS65 KCYS 022006 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 206 PM MDT Thu May 2 2024 .KEY MESSAGES... - A cold front will move through the region on Friday with another round of shower activity in the mountains and isolated thunderstorms over the southern Nebraska panhandle. Snow levels will remain above 6500 feet. - Mainly dry and warmer conditions are anticipated for the weekend. - Breezy to windy, and cooler weather expected for Monday through Wednesday, with isolated to scattered late day showers and thunderstorms. && .SHORT TERM /THROUGH FRIDAY NIGHT/... Issued at 125 PM MDT Thu May 2 2024 Afternoon satellite imagery and mesoanalysis reveals a stream of fast mid-level flow over southeast Wyoming evidenced by several mountain wave structures in both visible and Water vapor imagery. Surface gusts reflect this signal and have remained elevated in the 20-30 knot range today over much of the region. With a deeply mixed and dry boundary layer present, borderline critical fire weather conditions are possible for a few hours this afternoon before solar heating diminishes toward sunset. Expect surface flow east of I-25 to quickly diminish through the evening before switching to southeasterly upslope ahead of our next storm system. By early Friday morning, most guidance remains in good agreement showing a band of moisture stretching across central and southern Wyoming as a vort max approaches from the west. HREF ensemble guidance is in tight agreement depicting a surface cold front moving southward through southeast Wyoming and western Nebraska through the morning and early afternoon hours on Friday. Precipitation should remain generally confined to areas west of the Laramie range. Medium range and global guidance has continued the trend of slight increases in QPF today, with up to 6 inches expected in the higher elevations of the Snowy and Sierra Madre ranges. Given that this precipitation will fall mostly after sunrise on Friday, have opted to keep these areas out of headlines for now given the expected very low impact nature of this event. Snow showers are possible in lower elevations on Friday as well in Carbon, Albany, and far western Laramie and Platte Counties. However, impacts will remain quite low with warm ground temperatures and partly sunny skies during the afternoon. Farther east, the frontal boundary will not quite clear the southwest Nebraska Panhandle before convective initiation commences. With upper-30s to near 40 dewpoints in place with southeast flow, wind and moisture profiles favor a few isolated convective cells possibly affecting Cheyenne and Morrill Counties from 1pm through about 4pm. Briefly gusty winds and perhaps some sub-severe hail would be the greatest threat from any storms. Behind this system, expect a reinforcing shot of cold air with temperatures in the 20s or lower in all zones by Friday night. Forecast guidance is in generally good agreement with high confidence through the short-term period. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Issued at 220 AM MDT Thu May 2 2024 Saturday...Warming and drying expected as a transitory low amplitude shortwave ridge aloft builds overhead. 700 mb temperatures near 2 Celsius will yield maximum temperatures in the lower to mid 60s. Sunday...Continued mainly dry, though with isolated showers and thunderstorms, as the flow aloft transitions to southwest and there is minimal low and mid level moisture. This day looks like the warmest day of the period as a low level thermal ridge develops with 700 mb temperatures near 9 Celsius yielding maximum temperatures mainly in the 70s. Monday...Cooler temperatures expected as the next progressive shortwave trough aloft moves across the region. It looks like there will be adequate low and mid level moisture to produce scattered afternoon and evening showers, and a few thunderstorms. Tuesday...Looks like a windy and mild day as a wound up trough aloft and its associated surface low pressure pivots across eastern Montana, producing decent low level pressure gradients for our forecast area. With cyclonic curvature aloft and some low and mid level moisture, we anticipate isolated to scattered afternoon showers and a few thunderstorms despite the drying westerly low level downslope winds. Wednesday...The trough aloft pivots across the Dakotas, keeping cyclonic northwest flow aloft over our counties, and with adequate low and mid level moisture, we anticipate isolated late day showers. Continued breezy with decent low level pressure gradients and low level winds. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 1049 AM MDT Thu May 2 2024 VFR expected to dominate at all terminals through the entire afternoon and evening. Expect gusty westerly winds in the 20 to 35 knot range at most terminals. Winds will diminish this evening with partly cloudy skies overnight at all terminals. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...MAC LONG TERM...RUBIN AVIATION...MAC