FXUS66 KOTX 192147 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 247 PM PDT Thu Sep 19 2024 .SYNOPSIS... Weather will trend drier toward the end of the work week, then light rain chances mainly for the mountains Sunday into Monday. Chilly temperatures with frosty conditions is expected in the mornings over the weekend. Colder pockets in the northern mountain valleys will see a greater than 50 percent chance of reaching the freezing mark. A warming trend with above normal temperatures by mid week is expected after this weekend. && .DISCUSSION... Tonight through Sunday: A shortwave trough of lower pressure moving across southern BC will bring enhanced westerly to northwesterly winds through Friday. Winds will pick up through the Cascade gaps this evening with gusts up to around 25-30 mph, especially on the higher benches around Wenatchee to Chelan. The pressure gradient then becomes more northerly into Friday with similar magnitude winds down the Okanogan Valley. Funneling effects late in the morning into the early afternoon hours will increase the potential for wind gusts to around 35 mph between Oroville to Coulee City. The northerly gradient will draw down a polar continental air mass with dew points plunging into the lower to mid 20s. Winds will relax Friday night with mostly clear skies. This will set up the potential for strong radiational cooling with chilly overnight temperatures expected. Model Output Statistics (MOS) guidance tends to do the best for these strong radiational cooling patterns when temperatures can get quite cold right near the surface. Cold pockets across the northern mountain valleys will see the potential of dropping down into the upper twenties. This includes locations such as Republic, Colville, Chewelah, Deer Park, Priest River, and near Priest Lake. Surrounding areas, including up the Methow Valley, northern Columbia Basin, Palouse, Central Panhandle Mountains will see a greater than 50 percent chance for frost. Higher clouds will begin to stream across the Cascades Saturday night. This will help counteract radiational cooling effects for the next night, but it doesn't look like it will be enough to prevent northeast Washington into the Idaho Panhandle from dropping back down to near freezing. A freeze watch is in effect for Friday night through Sunday morning and covers the risk for freeze damage to sensitive vegetation Friday night into Saturday morning and again Saturday night into Sunday morning. Temperatures will warm back up next week, so there is opportunity to squeeze out a little more growing potential if precautions are taken to protect sensitive vegetation over the weekend. Sunday night through Thursday: A shortwave disturbance drops across the northern portion of the region Sunday night followed by a warm front into Monday. Dynamics will be lacking with these disturbances and there is just a 25-50 percent chance for light rain mainly over the mountains from the Cascades over the Idaho Panhandle. It will be so dry at lower levels that moisture will have a hard time making its way all the way to the surface before evaporating as virga showers. Expect clouds to increas and thicken up, but little in the way of appreciable rainfall. Warm air advection with the warm front will pump up a ridge of higher pressure for Tuesday. Temperatures will warm up significantly above normal with highs in the upper 70s to low 80s. Warming trend continues into at least Wednesday with another couple of degrees of warming as many valley locations look to be in the 80s. There is uncertainty in timing and how this ridge will evolve. A minority of the ensemble members indicate a quicker break down with a stronger cold front passage that would bring more in the way of westerly winds. This could begin as early as Wednesday afternoon near the Cascades, and then breezy conditions potential spreading further east and continuing into Thursday. The greater consensus is fore a more gradual weakening and flattening of the ridge that would result in less wind. The concern for the former (less likely) scenario will be for elevated to critical fire weather conditions if all ingredients of winds and dry conditions line up. This scenario will be monitored with the forecast adjusted accordingly as next week approaches. /SVH && .AVIATION... 18Z TAFS: VFR conditions will prevail. A weather system passing to the north will increase westerly winds this afternoon across the Wenatchee area, Columbia Basin. Wind gusts to near 20 kts are forecast but could be locally stronger especially around KEAT. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for VFR conditions to continue for the TAF sites. && .PRELIMINARY POINT TEMPS/POPS... Spokane 46 71 37 71 41 72 / 0 0 0 0 0 10 Coeur d'Alene 45 68 38 69 40 71 / 0 0 0 0 0 10 Pullman 44 65 38 68 37 69 / 0 0 0 0 0 10 Lewiston 53 72 46 75 46 76 / 0 0 0 0 0 0 Colville 35 69 32 71 32 70 / 0 0 0 0 0 20 Sandpoint 42 66 35 67 35 67 / 0 0 0 0 0 20 Kellogg 46 65 38 67 41 67 / 0 0 0 0 0 10 Moses Lake 46 72 40 73 40 75 / 0 0 0 0 0 10 Wenatchee 54 72 46 74 49 74 / 0 0 0 0 0 10 Omak 47 73 42 76 46 74 / 0 0 0 0 0 10 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Freeze Watch from late Friday night through Sunday morning for Northern Panhandle. WA...Freeze Watch from late Friday night through Sunday morning for Northeast Mountains-Okanogan Highlands. && $$