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
726 FXUS65 KRIW 312151 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 351 PM MDT Fri May 31 2024 .KEY MESSAGES... - Active mountain snowmelt will occur Saturday through Monday as daytime high temperatures climb to 5-10F above normal. Foothill creeks and streams see daily diurnal rises. - Above normal temperatures combined with a breezy west to southwest wind could elevate rangeland fire conditions over central and southern Wyoming Monday. - Temperatures across the region will be above normal the latter half of next week as a ridge of high pressure builds across the western United States. && .DISCUSSION... Issued at 1250 PM MDT Fri May 31 2024 Cloud cover dissipated across the far north and eastern zones late Friday morning as cyclonic flow exited to our northeast. This has left abundant sunshine and seasonal temperatures across the forecast area early Friday afternoon. These conditions persist through Saturday morning with little more than increasing high clouds. Saturday finds mid-level moisture progressing into southwest Wyoming from the Great Basin in zonal flow. Daytime heating leads to isolated convection over the southwest mid to late afternoon and after 5 PM for portions of central Wyoming. Instability is limited and the sub-cloud layer is dry, so gusty outflow wind around 40kts would be the primary convective hazard. It appears this mid-level plume continues to traverse southwest and central Wyoming through Saturday evening and into the Sunday morning hours, so light showers may indeed linger much of the night. Otherwise, cloud cover steadily increases Saturday night helping to keep temperatures warm for Sunday morning. Shortwave energy swings east-southeast across the forecast area around midday Sunday. Showers look to be a decent bet (30-50 percent) across the northwest and most areas east of the Continental Divide, but extensive cloud cover Sunday morning should hinder instability for stronger convection that afternoon and evening. A trough off the Pacific Northwest coast spins a stronger shortwave toward western Wyoming Monday afternoon. Instability is more favorable for deeper convection across the west and north Monday afternoon and early evening. Breezy southwest wind Monday helps to boost temperatures a few degrees from those of Sunday, while also lowering relative humidity. As such, elevated rangeland fire weather conditions are possible across portions of central and southwest Wyoming Monday afternoon. The warmer temperatures of the Saturday through Monday time period enables active mountain snowmelt, with the bulk of the remaining snowpack positioned above 9K feet. Foothill creeks and streams will see daily diurnal rises, but available channel capacity and the fact this will be higher elevation melt should limit flooding concerns. The exceptions would be the Salt and Snake drainages where lower snow has yet to melt, and those drainages fed by the northern Bighorn Mountains. West-northwest flow follows for Tuesday dropping temperatures to more seasonal readings, while keeping isolated convection mainly confined to northern Wyoming and the I-25 Corridor. Ensembles continue to show a building ridge over the western United States for the latter half of next week. Temperatures rise into the 80s for many locations under the building ridge, approximately 10F above normal. There is some hint that a weak low in the Desert Southwest could circulate moisture north on the backside of the ridge late in the week. Thus, it is conceivable that isolated convection could still be present Thursday and Friday even with the ridge in place. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 351 PM MDT Fri May 31 2024 VFR conditions will prevail through the period at all terminals. Skies will remain mostly clear across the region through much of the period as well. Any breezy winds will diminish by 03Z this evening to light drainage flows or even light and variable to calm winds. Winds remain light at all terminals through 17Z Saturday. 15 to 20kt gusts from the west-northwest will then develop at the usual terminals (KBPI, KCPR, KPNA, KRIW, KRKS) and persist through Saturday afternoon. SCT to BKN mid-level cumulus will develop across the south late in the period (after 15Z Saturday) as a weak disturbance will bring chances for showers and isolated thunderstorms by Saturday afternoon across souther portions of the state. Best chance for any thunderstorm impacts (30% Chance) will be at KRKS after 19Z Saturday. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...CNJ AVIATION...Hensley