Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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621 FXUS66 KOTX 211006 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 306 AM PDT Sat Sep 21 2024 .SYNOPSIS... Temperatures will be chilly this morning, and again Sunday morning, promoting frost formation for many areas and freezing temperatures in the mountain valleys of northeast Washington. Dry conditions continue into Sunday. There is a small chance of light mountain showers in the north Sunday afternoon and evening. A ridge of high pressure will deliver above normal temperatures early next week. A more active pattern is expected for the latter half of next week, with the potential for breezy conditions, showers, and temperatures returning to near normal. && .DISCUSSION... Today through Sunday night: A dry seasonal westerly flow aloft prevails across the Inland NW through the weekend. A few weak upper level disturbances track will track through the flow. The atmosphere is quite dry especially with dewpoints in the mid 20s to mid 30s. Under weak surface high pressure, surface winds are light and temperatures continue to drop. Currently, most regional temperatures are running 7 to 19 degrees cooler than yesterday at this time. Temperatures have already reached the middle 30s in Deer Park and Sandpoint. Areas of frost and local freezing temperatures look likely across parts of extreme eastern WA into the northern Panhandle. The current early season Freeze Warning and Frost Advisories will remain in effect through mid morning. This looks to be the coldest morning of the week. Anticipate an increase of mid and high clouds by this afternoon as a weak shortwave ripples through the region. Not expecting precipitation as the lower levels remain dry. Afternoon temperatures should be up a couple degrees compared to Friday and close to seasonal normals, while winds remain light. Skies should clear by evening, although high clouds increase from the northwest by Sunday morning. Radiational cooling will be pronounced across extreme eastern WA and the ID Panhandle. Overnight temperatures are expected to take another nose dive with a return to near freezing readings across the valleys of northeast WA, north Idaho, and parts of the Palouse. The next shortwave passes through the region on Sunday and skies remain overcast for much of the day. This feature may lead to a few light showers with a 10-20% chance across the northern mountains Sunday afternoon and evening. West-southwest surface winds increase Sunday afternoon with gusts of 15-20 mph in the lee of the Cascades to the Columbia Basin. Despite the cloud cover, daytime temperatures are expected to warm a few more degrees with widespread 70s to lower 80s. /rfox. Monday to Friday: A ridge of high pressure builds over the Pacific Northwest, before the next trough moves in toward the second half of the week. Expect dry and weather through Tuesday. Then a trough moves in and the onshore flow increases. This will bring shower chances to the Cascades Wednesday, then across the northern mountains Wednesday night into Thursday. About 65% of the solutions favor this depiction, while the other 35% bringing chances to the eastern third of WA and lower ID too. So PoPs will need to be adjusted higher should the solutions start to trend wetter. Thereafter models continue to show a more progressive flow, but they diverge over the evolution of disturbances moving in. Shower chances will continue around the mountains and near the WA/ID border heading into Friday. Overall precipitation will be in the form of rain, but some higher mountain snows are possible starting late Wednesday night continuing into Friday over the Cascades. Away from the Cascades precipitation amounts are expected to be light. In the Cascades, the 24-hour probabilities of wetting rain 40-80%, with the higher probability near the immediate crest and around mid-week. Any snow that may fall there is expected to be light, with ensemble showing 24-hour probabilities of >=1 inch only near 10-20%. These incoming waves will also bring increased winds, with gusts near 15-25 mph each afternoon between Wednesday and Friday. If any of these waves are a bit stronger those winds may also be a bit stronger. Temperatures will reach the 70s to low 80s Monday, then rise into the upper 70s and 80s Tuesday and Wednesday (about 10 degrees above normal). Then temperature cool closer to seasonal norms and by next Friday night (into next Saturday morning) overnight lows near freezing will possible in similar places at they are this morning. Lastly we can`t rule out some patchy fog in sheltered valleys, but this is expected to be isolated. /Solveig && .AVIATION... 12Z TAFS: Bands of mid and high clouds will move over the region into today with light winds, followed by some evening clearing. This will result in continued in VFR conditions. /rfox FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for VFR conditions through Saturday night. /rfox. && .PRELIMINARY POINT TEMPS/POPS... Spokane 72 41 75 46 76 50 / 0 0 10 10 0 0 Coeur d`Alene 70 40 73 47 74 50 / 0 0 10 10 0 0 Pullman 69 39 71 45 71 47 / 0 0 0 0 0 0 Lewiston 75 47 78 55 78 55 / 0 0 0 0 0 0 Colville 72 33 72 36 76 41 / 0 0 10 20 0 0 Sandpoint 71 37 71 43 71 47 / 0 0 10 10 0 0 Kellogg 67 42 68 49 70 52 / 0 0 0 0 0 0 Moses Lake 75 43 78 48 79 51 / 0 0 0 0 0 0 Wenatchee 75 52 78 56 79 59 / 0 0 10 0 0 0 Omak 76 47 77 51 81 54 / 0 0 10 10 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Frost Advisory until 8 AM PDT Sunday for Central Panhandle Mountains-Idaho Palouse-Northern Panhandle. Frost Advisory until 8 AM PDT this morning for Coeur d`Alene Area. WA...Frost Advisory until 8 AM PDT Sunday for Washington Palouse. Frost Advisory until 8 AM PDT this morning for Okanogan Highlands-Spokane Area-Upper Columbia Basin. Freeze Warning until 8 AM PDT Sunday for Northeast Mountains. && $$