543 FXUS66 KOTX 061740 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1040 AM PDT Thu Jul 6 2023 .SYNOPSIS... For most areas very warm to hot temperatures and dry weather is forecast through the upcoming weekend. Chances for mountain showers and thunderstorms are in the forecast for the next several days along the East Slopes of the Cascades into the mountains of northern Washington and the north Idaho Panhandle. Locally gusty winds can be expected near these thunderstorms. && .DISCUSSION... Today through Friday: As of this morning, we remain in a northerly flow regime due to an upper-level ridge stationed off the coast of British Columbia. Throughout the day today we'll see a gradual shift to southwesterly flow as an area of low pressure drops down the east side of the ridge and eventually forms a closed low over Vancouver Island. Any residual smoke high up in the atmosphere that has blown down from the north will clear out by the end of the week. With warm air coming in from the southwest, temperatures will warm a couple of degrees each day throughout the Inland Northwest today through the weekend. Highs today will be in the low to mid 90s. Friday we'll see widespread 90s again with areas of the Western Basin and the L-C Valley potentially hitting 100. Temperatures won't be the only thing on the rise. As the area of low pressure inches closer, precipitable water values will increase to 150% of normal throughout the North Cascades, Okanogan Highlands, and Idaho Panhandle. Increased moisture and instability will bring a chance for afternoon and evening thunderstorms in these regions. 12-hour thunderstorm calibrated SPC probabilities are as follows: Thursday afternoon/evening: North Cascades - 40 to 60% Okanogan Highlands - 10 to 30% Northeastern Idaho Panhandle - 30 to 50% Friday afternoon/evening: North Cascades - 60 to 70% Okanogan Highlands - 30 to 50% Northeastern Idaho Panhandle - 20 to 40% /Fewkes Saturday through Wednesday: The main story this weekend will be the heat (more on that in the last paragraph) and mountain thunderstorms. Southwest flow aloft develops ahead of an upper level trough sending weak disturbances into the region. A combination of warming temperatures and continued moisture over the area (Precipitable Water 110-140% of normal) will yield more shower and thunderstorm activity mainly over the mountainous terrain during the afternoon and evening hours. Slow movement of storms will yield locally heavy downpours, as well as gusty outflow winds given the "Inverted V" structure to forecast soundings. This situation changes Sunday Night into Monday as the trough pushes inland with fire weather concerns on the rise. A combination of elevated instability, moisture, and lift will lead to a broader chance for thunderstorms over Central and Eastern Washington into the Idaho Panhandle, including the Columbia Basin. Giving the mid level flow will be on the increase, any elevated storms will have a quicker movement compared to this weekend. And with continued "Inverted V" soundings, rain amounts will likely be on the light side, which raises concerns for new fire starts. And after this system passes, breezy west to southwest winds has the potential to bring fire spread with any new starts. Tuesday and Wednesday dry westerly flow takes over. Regarding temperatures, a steady climb into Sunday with highs mainly in the 90s. The warmest spots both Saturday and Sunday such as Omak, Moses Lake, and Lewiston will be near 100F. This combined with warmer overnight lows mainly in the upper 50s and 60s will result in increasing heat risk. This will affect those sensitive to the heat, and on Sunday may start to impact anyone without effect cooling and/or adequate hydration. Heat Advisories may be needed and will be something monitored closely in the coming days. The Monday system should shave a few degrees off high temperatures after a mild Sunday Night. Tuesday and Wednesday will cool some behind the Monday system, but will still be above normal with high temperatures in the mid 80s to mid 90s. JW && .AVIATION... 18Z TAFs: Afternoon heating today will promote cumulus buildups across the northern Columbia Basin and mountains. Isolated cells will mature into weak thunderstorms with the greatest risk across the mountains stretching from Sandpoint to Colville to Republic and within the North Cascades around Winthrop, Stehekin, and Lake Wenatchee. Probability for lightning ranges from 15-30% from 18Z to 03Z. Any showers or storms will pose a risk for outflow winds up to 30 mph. && .PRELIMINARY POINT TEMPS/POPS... Spokane 91 60 92 61 94 62 / 0 0 0 0 0 0 Coeur d'Alene 90 59 91 60 93 61 / 0 0 10 0 0 0 Pullman 88 57 91 57 91 59 / 0 0 0 0 0 0 Lewiston 98 65 99 66 99 69 / 0 0 0 0 0 0 Colville 90 54 91 54 93 56 / 10 10 20 10 10 10 Sandpoint 87 57 88 57 90 58 / 0 0 20 10 10 0 Kellogg 85 61 86 62 88 64 / 10 0 10 10 10 0 Moses Lake 97 64 98 64 98 63 / 0 0 0 0 0 10 Wenatchee 95 69 96 69 97 69 / 0 0 10 10 10 10 Omak 96 66 96 65 98 65 / 10 10 20 20 10 10 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$