Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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465 FXUS65 KCYS 020415 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 1015 PM MDT Mon Jul 1 2024 .KEY MESSAGES... - Strong to severe thunderstorms possible this afternoon and evening...mainly across the northern Nebraska Panhandle into Converse and Niobrara Counties in east central Wyoming. Thunderstorms will generally end by 6pm. - Much drier air and warmer temperatures expected Tuesday into Wednesday when we could see critical fire weather conditions for some areas along and west of the Laramie Range. && .UPDATE... Issued at 749 PM MDT Mon Jul 1 2024 Latest radar loop was showing the storm in Niobrara county showing signs of weakening during the last 15 minutes or so and becoming more outflow dominant. In fact, Douglas reported a 56 mph wind about 20 minutes ago due to the outflow winds. As a result, we are letting the Severe Thunderstorm Watch expire at 8pm. Still cannot rule out a few storms storms developing later this evening and overnight, due to the passage of the upper level trof. However, we are not anticipating any severe convection due to limited instability and shear. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 258 PM MDT Mon Jul 1 2024 Ongoing showers and thunderstorms will generally diminish in intensity this evening as they move east toward more stable air in the central NE panhandle given strong capping remaining in stable cloud cover. Farther west, a broad trough axis will continue slowly lumbering eastward through the northern Rockies. This feature and associated weak lift/elevated instability will keep isolated showers and possibly a few rumbles of thunder going overnight, especially over the higher terrain and higher basins of southeast Wyoming. The trough axis finally will pass east of southeast Wyoming and Western Nebraska by mid-morning on Tuesday. Have opted to keep low-chance PoPs in the forecast through Tuesday morning to cover the threat given by this trough and any lingering instability aloft. By 18z Tuesday, dry westerly flow will overspread most of the CWA with temperatures running near to slightly below seasonal averages on Tuesday afternoon. The one exception will be in northern Converse and Niobrara counties, possibly into Sioux and Dawes county NE where colder air aloft over top of surface heating in the wake of the trough will be enough to force a few afternoon showers in a post- frontal regime. Cloud cover will generally clear in the southern half of the CWA, with areas along and north of US26 remaining partly to mostly cloudy through the day. By Tuesday night into Wednesday morning, heights will steadily rise with zonal flow moving in over the high plains. Expect a mainly clear night with dry air in place on Tuesday night, leading to temperatures running around 5 degrees below average, possibly even cooler in the southeast Wyoming mountains. Forecast confidence is generally high throughout the short-term with only minor adjustments done to PoP and QPF grids in this forecast package. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Issued at 258 PM MDT Mon Jul 1 2024 Thursday... Deterministic and ensemble model guidance agree on the next upper-level trough and associated jet digging into southeast Wyoming by Thursday morning. The trough will send a cold front down the eastern WY plains early in the period, resulting in slightly cooler temperatures and highs in the mid to upper 70s, along with breezy northwest winds. This feature will also bring the best precipitation chances to east-central WY and northwest NE Thursday morning and afternoon, ending during the evening. The best low-level moisture will remain to the east, and shear weak, resulting in only weak thunderstorms expected. Friday-Saturday... Behind the aforementioned trough, models agree on building a ridge over the western US, resulting in northwest flow developing over WY and w NE. Weak disturbances in the flow may bring an occasional weak shower or storm. Otherwise, as the ridge builds, temperatures across the plains will rise from around 80 on Friday to near 90 on Saturday. Sunday - Monday... Models begin to diverge Sunday and Monday, the agree on continued ridging across the western US with northwest flow over WY. Ensembles and deterministics disagree on how amplified the ridge becomes, with the Euro becoming more amplified than the GFS. The GFS solution brings better shower and thunderstorm chances to the region. High temps should remain in the mid to upper 80s by the start of next week. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1020 PM MDT Mon Jul 1 2024 Westerly flow aloft will continue. Wyoming TAFS...Scattered clouds from 8000 to 12000 feet will prevail. Winds will gust from 25 to 32 knots from 15Z to 00Z. Nebraska TAFS...Scattered to broken clouds from 8000 to 10000 feet will prevail. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ UPDATE...REC SHORT TERM...MAC LONG TERM...BL AVIATION...RUBIN