Area Forecast Discussion
Issued by NWS Spokane, WA

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000 FXUS66 KOTX 271203 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 503 AM PDT Tue Oct 27 2020 .SYNOPSIS... Temperatures will begin to moderate this week with near average readings by the end of the week. Significant precipitation is not expected this week. An incoming system increases chances for light rain and mountain snow for the end of the week. && .DISCUSSION... Today through Thursday night: The Inland Northwest will be on the edge of a building high pressure ridge in the eastern Pacific. Moisture streaming over BC will make this a dirty ridge in the sense that mid to high level clouds will filter across at times through Wednesday. A ripple through the westerly flow across western Canada will draw in a bit more moisture into the Northeast Mountains and Northern Panhandle for Wednesday. The atmospheric column is expected to moisten just enough for some flurries in the morning to sprinkles by the afternoon for places like Metaline Falls, Sandpoint and Bonners Ferry. Cloud cover will be a bit thicker across these northern zones on Wednesday as well and remain clear or mostly clear further south into the basin and over to the Palouse, Lewiston-Clarkston Valley and Camas Prairie. The clear skies at night will strengthen nighttime inversions, and, even though there will be some sun in the afternoon, warming temperatures aloft around the ridge will make it tough to break these inversions to achieve as much warming as models are suggesting. The strong inversions will result in stagnant conditions. Conditions may not be as stagnant into Wednesday though with the clouds, but little in the way of mixing is likely region-wide Wednesday night through Friday morning. Fog is expected to increase through this week as dew points see a steady increase with surface moisture mixing into the boundary layer. This will be especially so where snow is on the ground across the northern mountain valleys and down into the Spokane- Coeur d`Alene corridor. Thursday looks like the best chance for fog this week with the best potential for clear skies, a moist boundary layer and weak winds. Temperatures will also modify through the week with lows in the 20s and highs in the 40s to low 50s for most places by mid week. /SVH Friday through Monday: The upper level ridge begins to break down on Friday as a trough and its associated cold front begin to push into the Pacific Northwest Friday afternoon. The front isn`t too impressive and has been becoming less impressive with each new model run. Temperature wise, highs slightly drop this weekend compared to Friday, but remain in the low to mid 50s. Snow levels are expected to be above 5000ft keeping rain and snow chances limited to the higher mountainous regions with little to no precipitation expected for lower lying areas. However, increasing cloud coverage will keep low temperatures quite moderate compared to the cold temperatures we have experience the past few days. Southwest winds will pick up following the front on Friday and will be breezy mainly for the Columbia Basin into the Palouse with gusts up to 20 mph during the afternoon and evening hours. After the trough exits the area early Saturday morning, the ridge returns putting the PNW into a primarily W-NW flow through the weekend into early next week. Skies will partly to mostly cloudy, and temperatures will be normal for late October/early November with highs in the 50s and lows in the 30s. VMT && .AVIATION... 12Z TAFs: A little bit of valley stratus is expected this morning in northeast Washington and in the central to northern Idaho Panhandle. This will include a scattered stratus deck from KGEG to KCOE and up the Silver Valley in Idaho. Ceilings will be above 3 kft agl with VFR or, at times, marginal VFR conditions. Otherwise, high cirrus will filter down into north-central and northeast Washington and the Idaho Panhandle as moisture tops high pressure in the eastern Pacific. Further south toward the Oregon border will be clear to mostly clear skies today and tonight. /SVH && .PRELIMINARY POINT TEMPS/POPS... Spokane 36 22 44 25 48 29 / 0 0 0 0 0 0 Coeur d`Alene 35 24 43 29 49 31 / 0 0 0 0 0 0 Pullman 40 24 48 28 55 32 / 0 0 0 0 0 0 Lewiston 46 31 53 36 60 38 / 0 0 0 0 0 0 Colville 38 19 44 24 47 25 / 0 0 0 0 0 0 Sandpoint 36 25 42 29 45 30 / 0 10 10 10 0 0 Kellogg 39 30 47 35 50 38 / 0 0 0 0 0 0 Moses Lake 43 24 50 26 52 29 / 0 0 0 0 0 0 Wenatchee 44 36 50 36 52 38 / 0 0 0 0 0 0 Omak 40 30 48 33 50 33 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Air Stagnation Advisory until 11 AM PDT Thursday for Central Panhandle Mountains-Lewis and Southern Nez Perce Counties- Lewiston Area-Northern Panhandle. WA...Air Stagnation Advisory until 11 AM PDT Friday for East Slopes Northern Cascades-Northeast Mountains-Okanogan Highlands- Okanogan Valley-Waterville Plateau-Wenatchee Area. && $$

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