Local Forecast Discussion
854 FXUS65 KPIH 201945 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 145 PM MDT Fri Oct 20 2017 .SHORT TERM...Tonight through Monday. A strong low pressure trough was advancing east across SRN Idaho early this afternoon resulting in a broad area of advisory level winds throughout the ERN Magic Valley and Snake River Plain and a smaller area of stronger winds across CNTRL INL. Areas of blowing dust and reduced visibility were noted on several ITD web-cams due to the strong winds. Thus the wind advisory will continue for the aforementioned area through 9PM MDT this evening. Radar was showing scattered snow showers across the CNTRL mountains where a colder and drier airmass was advancing into the region from the west. Across the SE Highlands where temperatures were warmer, light rain showers were noted. The trough axis is expected to work into the Wyoming border area early this evening as a secondary trailing wave digs into WRN Idaho. The resulting WNW flow aloft will be supportive of upslope showers favoring the CNTRL and NE mountains overnight and little or now precipitation elsewhere. The next upstream storm system begins to setup over the Gulf of Alaska Saturday resulting in a warm moist overrunning pattern which edges into the CNTRL and NE mountains Saturday night and continues through Sunday evening as an ejecting short-wave shears east through Canada. Thus we should see ongoing snowfall and periods of lower valley rain mainly north of the Snake River Plain Saturday night and Sunday. Wind speeds will nose up towards advisory levels once again Sunday as the short-wave shears north and east of the region. Drier and warmer conditions follow Sunday night into Monday as a ridge of high pressure builds along the west coast driving the storm track north into Alaska and Canada. Huston .LONG TERM...Monday night through Friday. Expect dry and warm conditions Tuesday. A Canadian wave circles around upper ridge in Pacific Wednesday and both the GFS and European operational models have it affecting southeast Idaho to varying degrees Wednesday into Thursday. GFS stronger and much colder with system. Introduced some precipitation chances Wednesday night mainly in high elevations and dropped high temperatures considerably Thursday with warming again Friday as system pushes east. Tuesday and Wednesday should be very warm with highs well above normal. GK && .AVIATION...Strong winds will continue through sunset at BYi, PIH and IDA with speeds in the 20 to 35 knot sustained range and gusts 40 to 50 knots at times. Some MVFR ceilings will continue at those sites as well as DIJ where rain will likely change to snow showers and could lead to some reduction in visibility as well. Lower ceilings expected to linger at DIJ the longest through sunset or slightly beyond. Precipitation has moved out of SUN and expect VFR conditions through Saturday. Sustained winds of 15 to 25 mph expected again Saturday afternoon at the Snake Plain sites BYI, PIH and IDA. GK && .FIRE WEATHER...A surface cold front associated with the low pressure disturbance moving inland will cross the Snake Plain early this morning. Southwesterly winds 25 to 35 mph with gusts to near 50 mph will develop this morning and continue through early evening. A Wind Advisory is in effect. Southwesterly winds will increase over the exposed upper elevations of the mountains in all areas, gusts to 30 mph pretty common, 35 for the Southern Sawtooth and Caribou Forests. The disturbance is tracking a little more south which helped easy the winds on the Lemhi Range down some. Showers will spread to the Wyoming border by noon today. Through about midnight Friday night, the west slopes of the Central Mountains, including Stanley and Galena Summit area could see .10 to .40 inches liquid equivalent of precipitation, a few west facing slopes possibly a half inch. Temperatures drop back to the 40s in the mountains and around 50F valleys Friday. Snow levels after rising to near 10000 feet elevation on Thursday, come back down to around 5500-6000 feet Friday afternoon and continue to fall to the valley floors by Saturday morning. Scattered showers will diminish Friday night and early Saturday before the next round of moisture advances across the Central mountains and Eastern Highlands Saturday night and Sunday. This second round may target the west slopes of the Central Mountains Saturday evening through Sunday evening, thus the wet facing slopes could see an additional .1 to .3 inches of precipitation. Banner and Galena Summits may see 1 to 4 inches of snow from this second round. Then a gradual return to dry high pressure ridge follows Monday and Tuesday. Models are more in agreement by Wednesday of next week and bring a chance of showers in north-northwest flow through the Salmon-Challis and Targhee Forest area. This is followed by another two day period under a ridge of high pressure. RS && .PIH WATCHES/WARNINGS/ADVISORIES... Wind Advisory continues through 9 PM MDT this evening for IDZ017-020- 021. && $$
NWS PIH Office Area Forecast Discussion