699 FXUS65 KPIH 171949 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 149 PM MDT Fri Jun 17 2022 .SHORT TERM...Today and Saturday. Satellite imagery shows high pressure ridging just east of our area with an approaching upper level low over western OR/WA. This is creating a tight pressure gradient. Southerly winds are strong across the area. Models are forecasting winds at 700 mb at around 45 mph. There are widespread areas of relative humidity less than 15 percent current. Lapse rates are 9 to 10. Thus, we are expecting mostly full mixing from 700 mb to the surface. Have wind advisories and high wind warnings out for the entire areas outside of mountain zones. Winds will be, in general, 25 to 35 mph with gusts of 45 to 55 mph. Our southwest areas including I-84 and the I-86 corridors as well as the Arco desert will be the strongest, 35 to 45 mph sustained with gusts greater than 57 mph likely. High wind warnings are in place for these areas. Downslope winds creating direct crosswinds on I-86 and I-84 are the biggest concerns. The low pushes slightly east tomorrow. Winds will again be elevated around 20 to 30 mph with gusts of 40 to 50 mph. Saturday afternoon a wind advisory may be needed along the Utah and Wyoming lines, where winds will be strongest. Also, due to monsoon moisture there is a slight chance of thunderstorms tomorrow afternoon, mainly along the Wyoming border. Expect strong outflows from these thunderstorms as winds aloft again will be high. Temperatures will be 10 to 15 degrees above normal today before dropping to around normal Saturday due to colder air behind a weak cold front moving into the area. Wyatt .LONG TERM...Sunday through Friday. The low moving across the Northern Rockies and Great Basin continues to slowly churn across the area and eventually to the northeast on Monday. There will be a lingering trough on the back side of the main low across Montana. Looking at the the models (NAM, GFS, ECMWF) vs the cluster forecasts. They are showing the general pattern, but there are differences. The NAM and ECMWF all show a deeper low/trough hanging back across southwest Montana and Idaho, which matches closer to about 45-50% of the clusters. The other half of the clusters are even deeper. Meanwhile, the GFS is shallower as the main low depicted is weaker and farther northeast. Despite those differences, the pattern still is focusing rain and mountain snow (above 8500ft) across the central mountains and Montana Divide. Overall amounts have come down, but we will likely see more changes as the event unfolds. At the moment, the trend is toward barely any rainfall across the Snake Plain, southern and southeast highlands. For the eastern highlands, we are looking at 0.10-0.30" based on the current forecast. That is backed up by the probability forecasts, although there is a 25-35% chance of over 0.50" and around a 15% chance for over 1". For the central mountains, amounts range from around 0.10- 0.25" across the Wood River Valley/Sawtooths/Stanley Basin to 0.20- 0.50" for the rest of the central mountain valleys and 0.40-0.80" in the higher elevations. Looking at the probability forecasts, the higher ends of these ranges are only coming up with a 20-40% chance of happening. Snowfall will be light, although the highest peaks may see over 3". Stay tuned. Highs start out next in the 50s/60s down low and jump back into the 80s by the end of next week. Keyes && .AVIATION...The main impact for TAF sites is the higher winds today. At BYI and PIH, southerly gusts are expected in the 40-55kt range. Gusts of 35-45kts are possible at IDA and DIJ, with gusts at SUN even up to 30kts. We may see another round of isolated storms potentially impacting DIJ this evening and have included VCTS in their TAF. As stronger winds aloft shift east tonight, we are forecasting LLWS at PIH, IDA and DIJ through early Saturday morning. We expect a similar situation tomorrow with gusty winds, although much lower at 20-30kts, and isolated storms possible for DIJ. Keyes && .HYDROLOGY...Rivers in the Central Mountains went up slightly today due to snowmelt from warmer temperatures yesterday. The headwaters of the Snake river responded slightly as well. Today will be warmer than yesterday. Expect more snow melt. All rises look to be slight. The Big Wood river at Hailey remains in action stage and will likely only rise slightly. Current forecast has the Big Wood river dropping out of action stage by mid next week after several days of cooler temperatures. Rain is in the forecast for Sunday and Monday. However, current rain amounts look to be light overall, so not a lot, if any, rise in the river is expected due to the rain. Wyatt && .PIH WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 9 PM MDT this evening for IDZ052-054>058. Wind Advisory until 9 PM MDT this evening for IDZ051-053-059- 061>068-070-075. && $$