Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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492 FXUS65 KRIW 041729 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1129 AM MDT Tue Jun 4 2024 .KEY MESSAGES... - Drier and warmer weather will arrive this afternoon and continue through at least Thursday. - Windy conditions are expected today and tomorrow, with elevated fire weather possible on Wednesday afternoon. - Warm temperatures will lead to high elevation snowmelt which could bring rising river levels and minor flooding late this week. && .DISCUSSION... Issued at 125 AM MDT Tue Jun 4 2024 Summer, at least weather wise, will be arriving, especially starting on Wednesday. As for now, we still have some showers across northern portions of the area in response to the Pacific trough moving across the area and the left front quadrant of an 120 knot jet providing some upper level divergence. These showers should continue to decrease through the overnight but a few may linger into the morning hours before everything ends by around 10 am or so. The main concern then shifts to wind as we shift from the left front to right front quadrant of the jet this afternoon, enhancing downward forcing. Reasoning remains the same as yesterday. The 700 millibar winds do not look sufficient for high winds, but gusty to strong winds are certainly possible. Some windier areas, like Rock Springs, have greater than a 1 in 2 chance of seeing wind gusts over 40 mph. Temperatures today will average close to slightly above normal. Humidity should remain high enough to prevent many fire weather issues. Wednesday also looks dry. This is where temperatures will begin to rise, with many locations likely seeing their warmest temperatures of the calendar year with lower elevations seeing highs well into the 80s. This a day when elevated fire weather may be a concern. The low that brought the rain will be held up by a blocking ridge over eastern Canada, with the low spinning over Manitoba. A tight height line gradient between the low and ridging building across the desert southwest. In addition, the jet will be close enough to keep breezy to windy conditions continuing. With relative humidity falling into the teens at times, fire weather statements may be needed for Wednesday. Thursday looks dry and warmer as well, and probably the first possibility to see high temperatures hit 90 in our warmer spots. Also, with the ridge building northward, wind will decrease. The heat really looks to peak on Friday, with the best chance of seeing high temperatures in the 90s. This is also the day some mid level moisture will be introduced to the area, bring a possibly, although a small one (generally less than 1 out of 4 chance) of some afternoon or evening convection. And, with the hot temperatures, rising rivers will likely become a concern. A general rule of thumb around here is three days with highs in the 80s is when high level snowpack really starts to melt. So, we will have to start watching for this, especially starting on Friday. More uncertainty creeps into the forecast stating on Saturday. The ridge looks to get suppressed just a bit with some shortwaves moving into the area, bring chances of convection, mainly of the diurnal variety. There are still differences in guidance in the timing of the waves, so details are still hard to come by though. It does look more active for the weekend and Monday as well. Nevertheless, I think we can safely say, welcome to summer in western and central Wyoming. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1130 AM MDT Tue Jun 4 2024 Yesterday`s weather system moved eastward overnight, bringing strong northwest mid-level flow over western and central Wyoming today. With some cumulus around 5-7K ft and high clouds streaming toward the southeast, VFR conditions will dominate today and remain through the forecast period at the TAF sites. Biggest issue today is the WNW wind, with 15-25 kts and gusts 25-35/40 kts this afternoon and early evening. Far northwest WY may see some localized MVFR conditions late this afternoon and evening, but precipitation is not expected at any TAF sites. Winds will decrease around sunset, but remain 8-12 kts. The WSW- WNW winds will increase again between 05/15-17Z tomorrow as a zonal/NW mid-level flow pattern continues with high pressure building over the Great Basin. A weak wave in the flow will bring increased clouds to northern WY from 05/06-18Z, with decreasing clouds in the afternoon. Wednesday`s winds will again be 15-25 kts with 20-30 kt gusts during the afternoon at most TAF sites. 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. && $$ DISCUSSION...Hattings AVIATION...McDonald