Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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937 FXUS65 KRIW 130501 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1101 PM MDT Sun May 12 2024 .KEY MESSAGES... - An unsettled weather pattern sets up thanks to weak ridging and northwest flow, but temperatures remain above normal through Tuesday. - Shower and thunderstorm chances increase through the next several days. Best chances for showers and thunderstorms will be across areas east of the Divide Tuesday and Wednesday afternoons. - Ridging redevelops for the later half of the week, decreasing shower and thunderstorm chances and allowing temps to rise back to above normal values through the weekend. && .DISCUSSION... Issued at 101 PM MDT Sun May 12 2024 A generally unsettled weather pattern begins to set up today, but we really won`t start to see the impacts of the unsettled pattern until tomorrow. That leaves today to be a relatively quiet day. Light winds exist across the CWA, with the exception of the northwest favored locations (mainly the Green River Basin and northeast Johnson County). Even across those locations, wind gusts will still generally remain less than 20 to 25 mph through the afternoon. Winds will be a tad stronger tomorrow afternoon, but only by 5 to 10 mph. As of noon, some terrain enhanced showers have developed along the Bighorn Mountains. These will continue through the afternoon. Some locations along the Bighorns could see up to 0.1" of rainfall out of these showers, with less than 10% chance of seeing more than 0.25". A few very isolated showers will also develop along the Absarokas and Owl Creeks, but these will be few and far between and dissolve just as quickly as they developed. Dewpoint depressions across lower elevations are 30 to 35 degrees this afternoon, so as showers slide off the mountains, they will quickly dry and dissolve. Hi-res models, such as the HRRR, hint at some outflows as a result of the dissolving showers across the Bighorn Basin and across Natrona and Johnson Counties. If outflows do develop, they are not expected to be more than 30 to 35 mph or to sustain themselves for any significant distance from the dissolving storm. Shower activity will end around sunset. Showers and thunderstorms will become more prevalent tomorrow afternoon, as well as Tuesday and Wednesday afternoons. Passing shortwaves in prevailing unsettled northwest flow will enhance instability, particularly across northern portions of the CWA. SPC continues with only a general thunder outlook for both Monday and Tuesday and CAPE will be weak (<500J/kg). Dewpoint depressions also will continue to be in the 30 to 40 degree range, so getting long- lived thunderstorms will be very difficult. Showers and weak thunderstorms are certainly possible though. Most northern areas have a 30 to 40% chance of rain Monday afternoon through the evening. Another, stronger shortwave will pass through on Tuesday and Wednesday. More showers and thunderstorms are expected, again, mainly focused across the north, especially east of the Divide. Details are lacking due to the inherently convective and chaotic nature of the showers and thunderstorms. We will continue to monitor and as we get more high-res model input over the next days, we will be able to narrow down timing and favored locations a bit better. At this time though, strong long-lived thunderstorms are not looking likely. After the passage of the shortwave Wednesday, which will cool temps back to near seasonal normals, Thursday will see temperatures will start to climb back above normal. Models are progging zonal flow through the weekend, but as of the latest runs, are suggesting the flow will be mostly dry. That is not to say that we won`t see afternoon showers and thunderstorms through next weekend, as confidence remains low in the pattern beyond Wednesday`s shortwave. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1059 PM MDT Sun May 12 2024 VFR conditions will prevail through Monday morning. Any showers roaming across the area this evening will wane over the next few hours. Convection will be increased in coverage Monday afternoon, though still focused on the northern half of Wyoming. KCOD, KJAC, and KWRL will have the best chance of terminal impacts, though confidence is still low on specific timing. Trends will need to be watched for a possibility of convection farther south as well. Otherwise, KBPI, KPNA, and KRKS will see a breezy afternoon. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hensley AVIATION...Myers