One low pressure system will continue to slowly move across the Rockies and Plains today.  Expect partly to mostly cloudy skies with isolated to scattered showers and thunderstorms statewide.  The best chance for precipitation will be in northwestern, central, and southeastern Wyoming.  However, any shower or thunderstorm that develops could produce brief periods of heavy rain.  There will also be a threat for small hail, gusty winds, and frequent lightning.  Temperatures will be cooler than normal in western and southern Wyoming today, with highs in the 50's to lower 60's.  Elsewhere, expect mild and closer to average temperatures, with highs in the 60's and 70's.  Another weather system will then move into the Pacific Northwest and northern Rockies on Saturday and Sunday, which will once again force subtropical moisture and atmospheric energy into Wyoming.  This weather system will then slowly propagate into the entire Rockies and Plains by Memorial Day and Tuesday.  On Saturday and Sunday, expect partly to mostly sunny skies with a smaller chance for showers and thunderstorms.  Temperatures will also be warmer and near or slightly above normal.  For Memorial Day, we will then see more clouds than sun with a better chance for showers and thunderstorms.  Temperatures, however, remain mild and near or slightly above normal.  We can expect partially clearing skies, isolated showers and thunderstorms, and cooler temperatures by Tuesday.