Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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262 FXUS65 KRIW 181743 AFDRIW Area Forecast Discussion National Weather Service Riverton WY Issued by National Weather Service Billings MT 1143 AM MDT Tue Jun 18 2024 .KEY MESSAGES... - Much cooler today, with highs in the upper 50s to middle 60s. - Light snow chances continue for the northwest mountains and the northern Bighorn Mountains. Afternoon showers and thunderstorms develop for the northern half of the area. - Warming trend through the rest of the week. Hot temperatures return to end the weekend and start next week. - Gulf moisture brings widespread rain chances Friday. && .UPDATE... Issued at 856 AM MDT Tue Jun 18 2024 Forecast in good shape. No changes necessary. && .DISCUSSION... Issued at 111 AM MDT Tue Jun 18 2024 Notably cooler air has made its way into the state from a cold front yesterday and last night. Lows this morning are generally in the low 40s east of the Continental Divide. West of the Divide, temperatures in the upper 20s are common. Would not be surprised if some of the more cold prone locations see lower 20s. Clearing clouds have allowed for the best cooling over the Green River Basin and southern Lincoln County. A similar story occurs for high temperatures today. Most locations peak in the upper 50s to middle 60s, which are 10 to 20 degrees below average, depending on location. As the upper low moves northeast out of Montana, some wrap around moisture keeps precipitation chances across the northern portion of the state today. This means continued snow for the northern mountains, including Yellowstone. Additional accumulations are largely less than an inch, though a few inches are possible in the Absarokas and northern high elevations of the Bighorns. Overall, little to no impacts are expected with this additional snowfall. For liquid (rain) precipitation, chances (20% to 60%) generally remain over far northern Wyoming, including the Bighorn Basin and Johnson County. More isolated chances (20% or less) occur for central areas, including Fremont and Natorna Counties. These chances peak during the afternoon as daily heating is maximized. Conditions are not favorable for anything strong, with CAPE less than 100 J/kg. Some thunder does look to occur though with the stronger showers, so the occasional outflow gust of 30 to 40 mph is possible. Gusty winds remain today for the Wind Corridor and some central locations. Gusts will largely be 20 to 30 mph. As mentioned above, some stronger gusts are possible with convection. These winds decrease Tuesday night. The synoptic pattern Wednesday is a dry, slightly southwest flow. This keeps precipitation chances to near zero. Temperatures also rebound to the uppers 60s to middle 70s, only slightly below average. Thursday starts very similar. A trough approaching from the west increases moisture across the region, so some afternoon and evening convection is possible, mainly along and east of the Divide. Highs Thursday reach near, to a bit above, average. The pattern becomes more interesting by Friday. A high over the eastern U.S., combined with the inbound trough, allows some Gulf moisture to makes its way into the area. How far north the best moisture occurs is still uncertain, with models currently keep the best moisture to our south, in Colorado. However, precipitable water (PWAT) values approaching 200% of normal are possible Friday. As a result, widespread rain chances remain in the forecast for Friday. This pattern looks short-lived, though, with that aforementioned trough moving eastward and cutting off the moisture supply through Saturday. Ridging looks to build in for Sunday, with hot temperatures to end the weekend and start next week. Though still too far out for a very accurate temperature forecast, there are indications for low to middle 90s. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1142 AM MDT Tue Jun 18 2024 Showers will increase after 18Z over northern portions of Wyoming affecting mainly KJAC and KCOD. Mountain tops may be obscured at times with some snow showers. Main aviation concern is west winds gusting 20 to 25 kts this afternoon. Skies will generally clear this evening, with light and variable winds returning. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Tesar DISCUSSION... AVIATION...Tesar