711 FXUS65 KRIW 020310 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 910 PM MDT Tue Jul 1 2025 .KEY MESSAGES... - A few showers continue through around midnight tonight, with a few lingering wind gusts possible. - Afternoon showers and thunderstorms chances increase beginning Wednesday and continuing through Friday. More widespread chances Thursday and Friday. - Slow moving showers and thunderstorms producing heavy rainfall Thursday and Friday could result in localized flash flooding. && .UPDATE... Issued at 114 PM MDT Tue Jul 1 2025 The forecast remains on track with hot temperatures and mostly virga/dry thunderstorm potential this afternoon and evening. Mean peak 700-mb temperatures ranging from 14C-18C will continue to support widespread highs in the upper 80s and 90s. Locations where there is more afternoon cloud cover could see high temperatures a few degrees below what is currently forecast and vise versa. This cloud cover is originating from mid-level moisture being advected into the region by the upper-level high over the Central Rockies and upper-level low off the coast of California, evident on water vapor imagery. A weak disturbance aloft rounds the high this afternoon and provides support aloft, combined with sufficient daytime heating, for isolated to scattered convection through sunset. Convection initiation is focused across high elevations of western and central Wyoming. However, given the dry low-levels with dewpoint depressions 40-60F degrees, most of this convection will likely be virga showers/dry thunderstorms. Any virga showers/dry thunderstorms has potential to produce dry downbursts with 40-60 mph outflows. If a thunderstorm gets strong enough, a brief downpour could occur. Convection remains on track to dissipate shortly after sunset, however, lingering high based, light rain showers over higher elevations cannot be ruled out through midnight. The forecast remains on track for increasing shower and thunderstorm potential for the second half of the work week. && .DISCUSSION... Issued at 242 AM MDT Tue Jul 1 2025 June has concluded and today marks the start of July. The upcoming weather pattern for the beginning of July is looking warm and unsettled across much of the Cowboy State. Warm, above normal temperatures are forecast over the next few days. Daily chances for showers and thunderstorms are expected through the remainder of the week. Southwesterly flow will usher in well above normal PWAT values for Wednesday through Friday. Convection chances will increase around the same time with daily coverage becoming more widespread starting Wednesday. Today, the first day of July, as mentioned earlier will be warm with above normal temperatures. Highs today will range from the mid to upper 80s west of the Divide and low to mid 90s east of the Divide. An upper level low moving into the Western CONUS today will be the key weather maker through the week. Multiple small disturbances will move across the area over the week bringing daily chances for showers and thunderstorms. Tuesday will see fairly limited convection being mainly isolated to scattered in nature during the afternoon and evening. One thing to keep in mind is that the atmosphere will still be rather dry, which will limit storm development and likely produce mainly virga showers. These showers and thunderstorms will be capable of producing some strong outflow winds due to large dewpoint depressions of 40 to 60 degrees in some locations, especially southern WY. Showers and thunderstorms will dissipate shortly after sunset. Wednesday will see much of the same with warm above normal temperatures and afternoon showers and thunderstorms. The one difference will be the influx of well above normal moisture. The aforementioned upper level low over the western CONUS will aid in funneling moisture into the region. Models show PWAT values of 0.60 to 0.90 inches which would be nearly 100 to 150% above normal. This moisture will aid in creating more widespread development of showers and thunderstorms. The strength of any storms that develop will still be fairly minimal as CAPE values only look to be around 500- 800 J/kg. Other favorable dynamics are not expected to be in place which should limit any strong storm development. Thursday will see the warm and unsettled pattern continue. However, moisture is expected to increase further with PWATs nearing 1 inch translating to almost 200% above normal values. This will increase the chances for periods of heavy downpours as showers and thunderstorms develop and move across the state during the afternoon and evening. While storm motion is not expected to be stationary there will still be the potential for some isolated flash flooding as a result of this increased influx of moisture. The other concern that develops on Thursday will be increased chances for strong thunderstorms. These increased chances are due to higher CAPE values along with more favorable dynamics as a result of a leeside low developing over the Northern Plains. While still a few days out the best chances for strong thunderstorms would be across eastern WY including portions of Natrona and Johnson Counties. Looking ahead towards the 4th of July, the unsettled weather persists with widespread chances for showers and thunderstorms. Temperatures will cool slightly compared to earlier in the week, returning to near seasonable values. Above normal PWATs linger which would create another day with chances for heavy downpours and isolated flash flooding. The best chances are currently looking to be across central and northern WY. These may create some difficulties when it comes to Independence Day celebrations. While the forecast is not set in stone, it is starting to look more likely that Friday may be quite unsettled for much of the Cowboy State. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 349 PM MDT Tue Jul 1 2025 Gusty outflow winds will continue to be a concern with any lingering convection through the evening. Convection should generally end towards sunset. BKN high clouds are expected to persist through the evening, but should scatter overnight, generally around 06Z to 09Z. Light winds (less than 8kts) will persist overnight through Wednesday morning. Widespread spotty showers and thunderstorms will then be present across the region Wednesday afternoon once again. All terminals with the exception of KJAC have at least a 25% chance of seeing shower or thunderstorms. Gusty winds would again be the primary threat from any showers and storms. 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. && $$ UPDATE...Straub DISCUSSION...Dziewaltowski AVIATION...Hensley |