Local Forecast Discussion
000 FXUS65 KPIH 180923 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 323 AM MDT Fri Aug 18 2017 .SHORT TERM...Today through Monday. Upper ridging over the Pac NW gradually flattens to zonal flow by Saturday. A weak upper low off the southern CA coast is the potential troublemaker as it pushes monsoon moisture into the northern Great Basin by Sunday. This sets the stage for isolated tstms over the southern highlands Sun aftn and eve. This trend continues again on Mon...but it still looks like the morning should be free of tstms. Unfortunately... there is still uncertainly about the cloud cover. Monsoon moisture is usually accompanied by some degree of mid and high cloudiness. Current model runs seem to suggest a higher probability of cloud cover to the north and south of the eclipse track. Although promising...cloud cover is a tough parameter to pin down in the short term let alone this far out. LONG TERM...Tuesday through Friday. Isolated tstms spread to the central mtns by Tue aftn and eve. More monsoon moisture is pushed into the fcst area late Wed as a large upper trof moves into the Pac NW. This increases chances for tstms across the fcst area thru Fri...mainly late afternoon and evening. Hedges && .AVIATION...Upper ridging and dry air will result in clear skies and moderately gusty southwest winds in the aftn and early eve. Hedges && .FIRE WEATHER...High pressure is firmly in place today and will bring dry and warm conditions through Saturday. Haines Index will remain high today through Sunday. High pressure starts to break down later Saturday as a trough moves through. Expect strong wind gusts of 25 to 30 mph across the Central mountains and 20 to 25 mph across the Eastern Magic valley and Snake River plain. A fire weather watch is in effect from Saturday at noon until 9 pm mdt for east Idaho fire weather zones 475 and 476. Though most of southeast Idaho will have low relative humidity below 15 percent, Zone 422, where there will be strong winds, looks to have relative humidity in the 15 to 20 percent range. Winds in all other zones, though elevated, are currently below critical values. Sunday expect Southwest flow allowing moisture to creep into the area. Expect mostly mountain afternoon isolated showers and thunderstorms Sunday and to a slightly higher degree Monday as well. The shower and thunderstorm threat increases Tuesday and beyond. Wyatt && .PIH WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Saturday afternoon through Saturday evening for IDZ475-476. && $$
NWS PIH Office Area Forecast Discussion