282 FXUS66 KOTX 092106 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 206 PM PDT Sat Oct 9 2021 .SYNOPSIS... The next weather system will bring a chance of rain tonight becoming likely in the Idaho Panhandle Sunday morning. Light snow is likely for the Cascade passes by Sunday morning. Breezy winds will also develop followed by cooler temperatures. This bout of cool will likely lead to widespread freezes across most valley locations. Drier weather is expected on Tuesday before a weak weather system brings a chance of precipitation on Wednesday. && .DISCUSSION... Tonight through Sunday night: A 110kt upper level jet will sag southeast over the region tonight sending a cold front quickly across the region. Initially a weak warm front will reach the Cascades late this evening with rain developing near the Cascade crest. The cold front will reach the Cascades late tonight, before reaching the Idaho Panhandle Sunday morning. Snow levels in the Cascades will drop from 7000 feet this evening to 3500 feet Sunday morning. Moist and unstable westerly flow behind the cold front will likely produce showers into the Cascade crest with snow expected for Stevens Pass. Given the warmer road temperatures any accumulation is expected on grassy surfaces with up to 2 inches possible by Sunday evening. With a possible Puget Sound Convergence Zone in the morning near Stevens Pass some brief higher snow intensity is possible. Behind the cold front a colder air mass moves in with 500mb temps falling to near -30C Sunday afternoon which will aid in destabilizing the atmosphere. Although on the flip side to the increased instability will be drying behind the front with model dewpoints dropping into the upper teens and 20s over much of Eastern WA/N Idaho. This should limit post-frontal shower activity except near the Cascade crest, Canadian border, and over the Idaho Panhandle. Model soundings show graupel possible out of the convective showers, with cloud temperatures likely too cold for lightning. The other story will be the windy conditions behind the front as pressure gradient tighten, producing wind gusts of 30-35 MPH across the Columbia Basin, Blue Mountains, Palouse, West Plains, and on ridgetops. Patchy blowing dust is possible, but recent rains leads to lower confidence of any significant visibility restrictions. Sunday night the showers will die off with the loss of daytime heating. Clearing skies, winds becoming light, and low dew points will mean another cold night for the region with widespread frost by morning with another hard freeze for similar locations that dropped in the 20s this morning. JW Monday: The trough will dig deep into the Great Basin. Patchy valley fog will burn off across NE WA and the ID Panhandle through the morning. Cooler northerly flow will prevail in the post frontal environment. Winds down the Okanogan Valley and into the western Columbia Basin will bring gusts 15-20 mph. Temperatures will also be cooler...in the 50s, which is 6-10 degrees below average. Ensembles are suggesting some mountain showers in the afternoon across Idaho. Otherwise all other locations will be seeing drier air rapidly move in providing sunny skies. Monday Night and Tuesday: Skies will be clear with fairly minimal fog development. This will allow temperatures to drop to the coldest readings in the 7 day forecast. Temps in the 20s is expected for most locations, but some typically colder northern valleys could see upper teens and some spots around Wenatchee and Lewiston could be at or slightly above freezing. Clouds will start to increase late Tuesday in the afternoon ahead of the next weather system. Tuesday Night through Wednesday Night: The next trough will move through the region. EC and GFS ensemble models are still showing more precip than what the NBM is. The onset of precip looks to be a bit slower than what it was showing yesterday. Tuesday night mountain snow and valley rain or possibly mixed with snow is expected for the Cascades. Then around sunrise it will move east. This is the period of greatest uncertainty. Will the precip reach the ground after the dry conditions Monday & Tues? Currently there is a slight chance of rain or snow for eastern WA and portions of N ID, albeit the chance and confidence is currently low. Latest ensemble timing bring the best chance of precip through during the afternoon and evening hours and have increased chance of precip for portions of E WA/N ID. We could also see some breezy winds, but currently they look to be 20 mph or less. Snow levels will be lowering through the night with snow down to 3000-3500 ft. So some mountains in the ID Panhandle could see light snow by Thursday morning. Thursday through Saturday: A little bit more uncertainty during this period. We look to be under a westerly or southwesterly flow ahead of another trough that moves out of the Gulf of Alaska and towards the region sometime next Sunday/Monday. Other than some isolated showers mainly across the Cascades and portions of north ID expect some benign weather. Temperatures start rebounding up Thursday and by Sunday we will be right around average for the middle of October...mid 50s to lower 60s. /Nisbet && .AVIATION... 18Z TAFS: Clouds will increase across the region through tonight as a cold front approaches and then tracks across the area. A brief period of rain is possible with the front mainly between 9-15z Sunday, with areas of MVFR conditions mainly over the ID Panhandle and eastern third of WA. Central WA will be in the rain shadow with continued VFR conditions forecast. Southwest winds will be locally gusty this afternoon ahead of the cold front. West-southwest winds will increase Sunday morning region wide behind the cold front with gusts 15-25 kts, locally to 30 kts forecast mainly after 14-15z Sunday. JW && .PRELIMINARY POINT TEMPS/POPS... Spokane 42 57 31 53 28 54 / 40 30 0 0 0 0 Coeur d'Alene 42 54 31 52 28 54 / 50 60 0 10 0 0 Pullman 41 54 30 49 26 51 / 30 50 10 10 0 0 Lewiston 47 61 38 55 34 57 / 20 30 20 10 0 0 Colville 39 57 26 54 19 56 / 50 20 0 0 0 0 Sandpoint 40 52 29 49 24 51 / 60 60 10 10 0 0 Kellogg 42 50 31 49 31 51 / 40 90 10 20 0 0 Moses Lake 44 62 31 57 28 56 / 30 0 0 0 0 0 Wenatchee 45 58 36 57 34 56 / 30 0 0 0 0 0 Omak 40 62 29 59 29 58 / 30 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$