Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
650 FXUS65 KRIW 081110 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 510 AM MDT Sat Jun 8 2024 .KEY MESSAGES... - Isolated (10-20%) showers and thunderstorms will be possible this afternoon and evening. - An area of subtropical moisture, along with Gulf moisture over eastern portions, will result in widespread showers and thunderstorms Sunday. - Above normal temperatures through the next week will continue to melt any remaining snowcaps on higher elevations. && .DISCUSSION... Issued at 211 AM MDT Sat Jun 8 2024 The Cowboy State will once again be squeezed between an upper level ridge to the west and an upper low/elongated trough to the north over Canada. The ridge will have more of an influence over the region, keeping temperatures about 10 degrees above normal. However, these readings will be a few degrees cooler than Friday. West- northwest wind will increase over areas west of the Divide this afternoon as a result of this squeeze play, while areas east of the Divide have a more northerly wind. Any convection will be very isolated (10-20%), with the better chances over the Green Mountains/Rattlesnake Range and southern Natrona County, the Absaroka Mountains and far western portions. Strong gusty winds will be the main threat from any shower and thunderstorm, as large inverted-V soundings will be in place again. Winds will decrease through the evening, with gusty outflows remaining possible east of the Divide through much of the night. The ridge will shift eastward over western portions of the CWA by Sunday morning. This will allow an area of subtropical moisture to move into this area by midday, leading to a more unstable environment. A shortwave trough will also be moving onshore over the PACNW Sunday morning. Rain showers and isolated thunderstorms will be possible over far western portions before 12pm as a result. Additionally, precipitable water values will range between 0.6 and 1.0 inches across the forecast area through the day. Gulf moisture will advect into eastern portions through the afternoon, adding to the moist and unstable atmosphere. This will culminate in CAPE values of 1000 to 1500 J/kg and LI`s of minus 4 to minus 6 across much of the CWA. SPC has outlined areas near the Star and Jackson Valleys for Sunday, but would not be surprised to see this expanded to areas east of the Divide. Strong gusty winds, small hail and locally heavy rain will be the main threats as storms move toward the east-northeast. This convective activity will be more isolated after midnight, with showers remaining possible through the night as the trough begins to move over western WY Monday morning. Temperatures west of the Divide will be about 5 degrees cooler Monday, with any convection staying over far northern portions of the forecast area as the trough makes its way over MT. Gusty winds will be more concentrated west of the Divide, due to the resulting pressure gradient from the passing trough. Winds will also be more north-northwesterly over the CWA. Dry conditions will return Tuesday, as a transitory ridge moves over the region. A more zonal flow pattern will be in place Wednesday, before a ridge, from a strong high center over AZ/NM, rebuilds over the Northern Rockies Thursday into Friday. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 509 AM MDT Sat Jun 8 2024 VFR conditions prevail through the TAF period. Afternoon showers and thunderstorms develop today, but will mainly be confined to the mountains and the area roughly between KRKS and KCPR. As a result, KCPR has about a 30% chance for a shower/thunderstorm this afternoon. KRKS and KJAC have less chances, about 15%. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .HYDROLOGY... Issued at 207 AM MDT Sat Jun 8 2024 Rivers and creeks will remain on the high side today at Action Stage or below, but look to remain steady for now. SnoTel sites above 9000 ft continue to drop and are now below 10 inches of SWE. At this rate, the remaining snow at these sites could be gone in the next couple of days. The notable exception is sites in the Tetons and portions of Yellowstone NP, where 20-30 inches of snow remain on the ground. Will keep the Flood Advisories in effect as a result, likely continuing through the weekend. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...LaVoie AVIATION...Wittmann HYDROLOGY...LaVoie