Area forecast discussion National Weather Service Boise Idaho 254 PM MDT Wednesday may 22 2013 Short term...tonight through Friday...deep strong cut off upper low will slowly weaken over the Pacific northwest through Friday. This will keep US cool...and give US a chance for showers mainly in the mountains. Winds will decrease as the gradients associated with the upper low decrease. With very cool air...decreasing clouds...and weakening winds overnight...there is a good chance for frost in the morning. Therefore...a frost advisory has been issued for the Treasure and western Magic Valleys. Temperatures are expected to range from near freezing to the middle 30s in the advisory area. As the low weakens and heights rise Friday...temperatures will warm and therefore the advisory is only for tonight into Thursday morning. After having high temperatures around 10 degrees below normal Thursday...we will have readings just a few degrees below normal for Friday. Long term...Friday night through Wednesday...upper level trough will remain over the Pacific northwest through the weekend and into next week. There are several embedded short waves that will move through the flow that will bring periods of showers and afternoon and evening thunderstorms to the forecast area. Temperatures through the extended period will be near normal. && Aviation...widely scattered MVFR conditions and mountain obscuration in rain and snow showers this evening north of a kbno- kono-ksun line. Snow levels from 3500 feet to 5500 feet mean sea level. After 06z skies will become mostly clear over southwest Idaho...so can not rule out the possibility of local valley fog in the west central mountains...especially at or near kmyl. Westerly surface winds 10-20 knots with gusts to around 25 knots this evening becoming light after 05z. Winds aloft will be westerly around 20 knots up through 10k feet mean sea level. && Boi watches/warnings/advisories... Idaho...frost advisory from midnight tonight to 10 am MDT Thursday idz012-014-016. Or...frost advisory from midnight tonight to 10 am MDT Thursday orz064. && $$ Weather.Gov/Boise Short term...snow pellets long term....ja/wh aviation.....Ja