Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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096 FXUS65 KRIW 290411 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1011 PM MDT Tue May 28 2024 .KEY MESSAGES... - Another mostly sunny and mild day across the Cowboy State. - Isolated showers and thunderstorms will be possible over southern/southwestern WY this afternoon and evening. - Wednesday will bring the possibility for scattered showers and thunderstorms with a few strong storms possible over parts of Johnson and Natrona Counties as well as the Bighorn Basin. && .DISCUSSION... Issued at 135 PM MDT Tue May 28 2024 Another beautiful late May day across the Cowboy State. Temperatures will continue to warm today, with highs in parts of the Wind River and Bighorn Basins having a (60-80%) chance of meeting or exceeding 80 degrees. Other parts of the state will still be warm, with highs in the 70s. Much of the state will remain dry today with the only exception being SW/S WY where there is a (10-40%) chance for showers this afternoon and evening. These showers will create some breezy winds with gusts of 20-30 mph, but much of the CWA will see light winds through the day. Wednesday sees the warming trend continue with areas east of the Divide having a (60-90%) chance of seeing highs at or greater than 80 degrees. These temperatures may create some river flooding issues, due to melting of mountain snow. Many ranges across the state currently have snowpack values greater than 100%, which may overload rivers depending on how quickly the snow melts. This is not expected to be a significant concern at the moment, but will need to be monitored over the next week. Wednesday will see the upper-level ridging be ushered out by a trough digging across the PACNW. The bulk of the disturbance is expected to remain to the north of the CWA, but a cold front will begin to sweep across the region during that time. CAMs continue to show the possibility of some convective showers and thunderstorms developing ahead of the front. Any storms that do develop look to initiate off high terrain during the late morning and afternoon. Some instability will be present with highs in the 70s to low 80s and dew points in some places ranging from the mid 30s to low 40s. This, combined with steep lapse rates across the region, should create CAPE values of 1000-1500 J/kg. Shear values are lacking across most of the CWA, meaning storms will pop up then quickly collapse. Overall, thunderstorms are possible with much of the state seeing a (20-50%) chance during the late morning and afternoon Wednesday. A few isolated strong storms cannot be ruled out with the best chance being across parts of Johnson and Natrona Counties where the most favorable dynamics may be present. Recent CAMs have begun to show there being a possibility for an isolated strong thunderstorm to develop across parts of western WY and especially the Bighorn Basin. These areas look to have favorable dynamics with dewpoints near 40 and some shear present through the low to mid atmosphere. If any strong storms were to develop, the main hazards would be strong gusty outflow winds and small hail. The cold front sweeps across the state during the evening Wednesday and early morning hours Thursday. A few isolated showers are possible across the northern CWA Thursday, as the northern shortwave slowly moves east. Temperatures for the second half of the week return to seasonable values, with quiet weather returning through Friday. Models are mostly coming into good agreement regarding the weekend. The consensus seems to be scattered showers and thunderstorms possible as a weak shortwave moves through the region. Most of the CWA looks to remain dry with temperatures returning to above seasonable values. Ensembles continue to agree on a pretty large warm-up for the first week of June, with a large potent ridge moving in over the western CONUS. The magnitude of this ridge and the warm temperatures that come along with it are still uncertain. However, early indications are showing possibly some of the warmest temperatures so far this year. It is starting to look like there will be a possibility (20-40%) of some areas seeing their first 90 degree temperatures of the year. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1010 PM MDT Tue May 28 2024 VFR conditions will prevail through the first half of the TAF period. Clouds will begin to increase over northwestern portions after 12Z, as a cold front approaches the area. Showers will be confined to this area through 18Z as well. Winds will increase at all terminals after 18Z, as the cold front makes its way over the area, resulting in gusts of 25 to 30 kt through the afternoon. Showers and thunderstorms will become more widespread through the afternoon, as the cold front progresses eastward. Most, if not all, terminals have a chance to be directly impacted, with KCOD and KWRL having the best chances. The wind will be the main impact, but IFR visibilities/MVFR ceilings and higher wind gusts could occur if a thunderstorm moves directly over a terminal. Showers and thunderstorms will become more confined over northern portions of the forecast area after 00Z, becoming more isolated through 06Z. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Dziewaltowski AVIATION...LaVoie