Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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998 FXUS65 KRIW 070900 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 300 AM MDT Tue May 7 2024 .KEY MESSAGES... - Showers continues across western WY with moderate to heavy snowfall possible in higher elevation through the morning. - Scattered showers and isolated thunderstorms develop this afternoon/evening. Winds are expected to remain gusty across most of the state. - Another round of precipitation is expected to move through the state Wednesday and Thursday. Mountain snow and low elevation rain with a few areas possibly seeing a transition to light snow by Thursday morning. - Quiet and mild weather returns to end the week, with the possibility for a sunny, mild, and pleasant weekend. && .DISCUSSION... Issued at 259 AM MDT Tue May 7 2024 IR this morning shows a well defined circulation over parts of of SE Montana, NE Wyoming, and W South Dakota. This circulation was the main culprit behind the soggy start to the week in many places east of the Divide. Showers spread across the state during the morning hours on Monday, as an upper-level low tracked across the area. Moderate to heavy rain fell across parts of Johnson and Natrona Counties, with rainfall amount by Monday evening nearing and even exceeding 1.50 inches in places. Winds continued to gust as well, with periodic winds gusts of 50+ mph in parts of Fremont and Sweetwater Counties. Unfortunately, showery activity continues today across the Cowboy State today but does not look to be widespread. Winds look to remain gusty in much of the same parts of the state as Monday. As mentioned earlier, the pesky Pacific low continues to bring impacts to the state whether that be in the form of precipitation or gusty winds. The low has moved into the Dakotas and eastern Montana this morning but impacts will continue to be seen. The pressure gradient remains tight with widespread gusts of 30+ mph during the day today. Areas that experienced strong winds yesterday will likely see another round today, with parts of Sublette, Sweetwater, Fremont, and Natrona Counties having a (50-80%) chance of seeing 45+ mph gusts. Due to the position of the low, flow will continue to be from the west/northwest. During the day today moisture will be wrapping back around into the state, which will aid in creating some instability in the atmosphere. Showers are expected to continue across western mountains especially in westerly/northwesterly flow favored areas such as the Tetons. Due to this winter highlights remain through the morning and afternoon across YNP, the Tetons, and the Gros Ventre. Lower elevation western valleys can expect to see some convective showers develop during the early afternoon, with a few rumbles of thunder possible. Some recent CAMs have shown showers developing in other parts of the CWA as well this afternoon. While these showers are not expected to be widespread most of the state will have at least a (20-40%) chance of seeing a shower this afternoon/evening. Temperatures remain on the cooler side across the whole CWA with highs being 10-15 degrees below normal. Unsettled weather continues through the overnight into Wednesday morning. The next round of precipitation develops during the morning Wednesday and becomes more widespread by the afternoon and evening. Winds are expected to decrease compared to the past few days but still remain breezy across most of the state. All of this is due to the low or its residual energy returning back into the CWA and moving across the state Wednesday. The remnants will gradually make their way over the state and end up near Utah by Wednesday evening. Flow will begin to shift as a result of this, with winds becoming north/northeasterly by late Wednesday evening. Areas that favor such flow like the eastern slopes of the Wind River Range, Absarokas, and Bighorns may see winter highlights issued, due to possible snow accumulation greater than 6 inches. At the same time northerly flow will help usher in some cooler air, with 700 mb temperatures ranging between 4-7 C for Thursday morning. This will be something to monitor especially in parts of the Wind River Basin along the slopes of the Wind River Range. Lander may see temperatures cool enough to see rain transition over the snow during the early morning hours Thursday. Currently the forecast remains to warm for this to happen but if there was a slight shift of 2-3 degrees lower than this may be a possibility. However, impacts would remain minimal with the only concern being slick roads mainly during the morning commute. These temperatures will need to be monitored as mentioned earlier, a shift of a few degrees may be the difference between all rain or morning snow in Lander come Thursday morning. Remainder of the week... Showers continue through most of the morning on Thursday, especially in northerly/northeasterly favored areas. Conditions begin to dry out by Thursday afternoon, as the low moves south into the Desert Southwest. A large area of high pressure looks to begin to build in by Friday, with a return to milder and quieter weather for the weekend. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 940 PM MDT Mon May 6 2024 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals A deepening low pressure system will continue to spin over the Northern Plains through the TAF period. On the backside of this low strong northwest flow will persist. Tonight, wind will be relatively light (sustained 10-15 knots gusting 20-25 knots) compared to Monday afternoon. Wind will increase by mid-morning across all terminals. The strongest wind will occur at KRKS where gusts as high as 45 knots will occur Tuesday afternoon. Tonight should remain dry as the low shifts to the north and east through the overnight hours. Then, this low will retrograde back toward WY Tuesday afternoon. Some breaks in cloud cover is expected Tuesday morning/afternoon, which will give way to convective showers. The best chance of snow/rain will be at KJAC with prevailing MVFR conditions by 12Z. Conditions may drop to IFR briefly if a stronger shower directly impacts the terminal. For now have PROB30 for snow showers at KPNA/KBPI. Mountain obscuration continues for the next 24 hours. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals A deepening low pressure system will continue to spin over the Northern Plains through the TAF period. On the backside of this low strong northwest flow will persist. Tonight wind will be relatively light for KCOD/KWRL/KLND terminals. At KCPR/KRIW wind will remain strong through the overnight hours into tomorrow. Wind will increase by mid-morning across all terminals. The strongest wind will occur at KRIW where gusts as high as 45 knots will occur Tuesday afternoon. Tonight should remain dry as the low shifts to the north and east through the overnight hours. Then, this low will retrograde back toward WY Tuesday afternoon. Some breaks in cloud cover is expected Tuesday morning/afternoon, which will give way to convective showers. The best chance of rain/snow will be at KCPR Tuesday evening. Conditions may drop to MVFR if a shower directly impacts a terminal, but the chance is too low (20%) at this time for prevailing rain. Mountain obscuration continues for the next 24 hours. 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... Winter Weather Advisory until 6 PM MDT this evening for WYZ001. Winter Storm Warning until 11 PM MDT this evening for WYZ012. && $$ DISCUSSION...Dziewaltowski AVIATION...Rowe