Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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589 FXUS65 KRIW 071729 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1129 AM MDT Tue May 7 2024 .KEY MESSAGES... - Showers continue 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 /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1130 AM MDT Tue May 7 2024 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals. Broad trough remains across the region today with gusty westerly wind again the primary hazard. Frequent surface gusts of 28-40kts at KRKS, KPNA, and KBPI into the evening hours. Meanwhile, southwest wind 15-28kts will be common at KJAC until sunset. Weak orographic flow to aid snow showers in the vicinity of KJAC through the afternoon with occasional MVFR conditions. KJAC to temporarily see VFR conditions before snow showers return in northerly flow aloft as a shortwave spins south across the state late tonight and Wednesday. Other than scattered brief MVFR snow showers this afternoon around KBPI and KPNA, VFR to prevail at the remaining terminals. A brief rain shower at KRKS to start the period, then quiet except for the winds. Breezy westerly wind persists overnight with an increase in speeds around 15Z-16Z/Wednesday. Mountain tops frequently obscured above 10K feet MSL through the period. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals. A broad trough persists over the Northern Rockies today leading to gusty west-northwest surface winds until around sunset. Gusts of 25- 40kts will be common during this time. Shortwave energy within the broad trough pinwheels south across the region late tonight and Wednesday. VFR conditions gradually give way to lowering ceilings and a better chance of rain and snow showers over the Bighorn Basin after 08Z/Wednesday. MVFR or low-end VFR to develop at KCOD and KWRL between 12Z-15Z/Wednesday, while other terminals remain VFR through 18Z/Wednesday. Mountain tops obscured after 09Z/Wednesday. 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...Jones