


Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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771 FXUS65 KCYS 070750 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 150 AM MDT Mon Jul 7 2025 .KEY MESSAGES... - There is an Enhanced Risk (Level 3 of 5) for severe weather today across portions of western Nebraska. All modes of severe weather are possible today: large hail, damaging winds, and tornadoes. - Hot temperatures and dry conditions return Tuesday, limiting precipitation chances across the CWA. && .SHORT TERM /THROUGH TUESDAY NIGHT/... Issued at 148 AM MDT Mon Jul 7 2025 Fairly quiet across the region once again tonight as skies slowly clear on the backside of afternoon and evening convection. Some low stratus is attempting to develop across southwestern Laramie County as of 07Z. Winds are fairly gusty at Cheyenne at this time, with southerly winds gusting around 25mph. Breezy conditions are ongoing across much of the area, with locations in the southern Panhandle gusting around 25mph and portions of southeast Wyoming gusting around 20mph. Temperatures are mild with current temperatures in the mid-50s to mid-60s across the CWA. Another active severe weather day is expected this afternoon into the evening hours, especially across western Nebraska where SPC has highlighted a portion of the CWA in an Enhanced Risk (Level 3 of 5) for severe weather. A very similar setup is expected today across the region, with westerly flow remaining in place aloft. The CWA remains sandwiched between a trough moving across southern Canada to the north and a ridge moving northward across the southern CONUS. The 500mb high over the southern CONUS will slowly meander northward towards the Four Corners Region, potentially signaling the start of the monsoon. Prior to this, however, several 500mb vorticity maxima will eject out around the high and traverse across the CWA this afternoon. One especially strong vorticity maxima will provide enough CVA that a 500mb shortwave develops and slides across this region this afternoon, starting between noon and 3pm. This shortwave and the induced shortwave at 700mb, will be the primary forcing mechanisms again today, along with the terrain-induced dryline surging eastward during the afternoon hours. Ahead of the surging dryline, southerly to southeasterly winds will keep dewpoint values in the mid-50s to low-60s this morning into the afternoon hours. Surface temperatures will rise into the mid-80s to low-90s again with daytime heating allowing for daytime destabilization. A weak backdoor cold front will drop down into the region this evening from South Dakota, likely increasing lift and leading to thunderstorm activity later into the night. Storm motion looks to be a bit faster than previous days as a 500mb jet streak develops and winds in the mid-levels increase to around 50kts. 700mb flow remains weak once more, though winds should be around 20 to 25kts at 700mb, slightly better than the 15 to 20kts of the previous days. Current HRRR runs suggest around 1800 to 2000J of SBCAPE this afternoon across the Panhandle, with the highest values on a line from Chadron south through Sidney. 0-6km Bulk Shear is progged to be a little lower with forecast soundings from the HRRR and RAP suggesting only around 30 to 40kts of bulk shear across the Panhandle. However, ample low-level turning is expected with 0-3km SRH values in the 100 to 120 range. 0-1km SRH remains low again, only around 25 to 35 in the northern Panhandle. The southern Panhandle boasts 0-1km SRH values around 50 to 75, suggesting a better environment for tornadoes across the southern Panhandle. Steep mid-level lapse rates across the region once again favor large hail, especially with a rather fat CAPE profile in the -10C to -30C hail growth range. Strong winds will also be favored a forecast soundings from the RAP and HRRR suggest around 1500 to 1700J of DCAPE, all with strong lapse rates throughout much of the atmosphere. Despite all of this, there is one featuring appearing on several forecast soundings that may result in convective inhibition remaining in place and prevent storms from forming. Several forecast soundings from the RAP suggest a warm nose around 1km above the surface, which would increase CIN significantly and potentially prevent storms from forming. The HRRR on the other hand does not have this warm nose, with steep lapse rates from the surface throughout much of the atmosphere. This potential warm nose will need to be monitored throughout the morning and afternoon hours as it could prevent convective initiation if it does show up in the late morning to early afternoon hours. The upper-level ridge across the southern CONUS will advect northward as the 500mb high moves over the Four Corners Region on Tuesday. With multiple vorticity maxima ejecting out from the high into the CWA, afternoon showers and thunderstorms will once again be possible. However, forcing will be much weaker Tuesday, leading to storms likely struggling to develop. Temperatures will soar into the mid-80s to mid-90s across the entire CWA Tuesday, leading to a hot, dry day across the CWA. Breezy conditions are possible out west of the Laramie Range, leading to continued elevated fire weather conditions across Carbon and Albany Counties Tuesday. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Issued at 207 PM MDT Sun Jul 6 2025 The upper level ridge over the Four Corners states will amplify for the middle part of the upcoming week. On Tuesday, 500-mb heights will climb close to the 90th percentile of climatology as the ridge strengthens. Expect highs to reach the mid 80s to mid 90s across the area. The surface dryline will nudge off to the east Tuesday, but not move completely out of the area. Current model guidance shows the dryline setting up near the WY/NE state line Tuesday afternoon, with ample moisture still present in the Nebraska panhandle despite drier air moving in aloft. There will be somewhat of a capping inversion in place once again, but a weak vort-max moving over the top of the ridge may be able to kick off isolated thunderstorms in far eastern Wyoming and into western Nebraska. Expect coverage to be much more limited, but we probably won`t be completely in the clear. The dryline will nudge further east on Wednesday as the magnitude of the heat reaches its peak. 700-mb temperatures will climb close to +18 to +20C, with the highest values over south central Wyoming. Ensemble mean 700-mb temperatures are around the 90th percentile of climatology. Considering this is the climatological hottest time of the year, record highs are fairly unlikely at this time, but hotter scenarios would put a few daily record highs in jeopardy. With drier air over most of the area, expect PM thunderstorm activity to be more limited, and likely confined to our far eastern zones. The next shortwave trough will move in from the west on Thursday, adding a bit more moisture aloft and cooling temperatures down by several degrees. PM storm activity may be more in the form of gusty high- based showers and thunderstorms as low levels look to remain on the dry side. A potent surface front will move through late Thursday or early Friday, leaving much cooler and more moist conditions in place for Friday. This may suppress instability too much over much of the High Plains, but scattered PM showers and thunderstorms may still be possible against the higher terrain as the surface front pushes against it. Temperatures will begin to rebound on Saturday, with continued chances for scattered PM shower and thunderstorm activity. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1037 PM MDT Sun Jul 6 2025 Outside of isolated showers moving west to east across the area through 07Z, expecting a relatively calm overnight period. With a moist boundary layer in place across the plains along with south-southeasterly upslope flow, pockets of MVFR stratus will likely develop after 05Z. Conditions will improve after sunrise. A cold front moving south across the area late morning through the afternoon will shift winds to the north-northeast and spark another round of showers and thunderstorms for the plains terminals after 20Z. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...AM LONG TERM...MN AVIATION...WFOCYS