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Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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643 FXUS66 KOTX 201744 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1044 AM PDT Sat Jul 20 2024 .SYNOPSIS... Very hot temperatures will continue through Monday with widespread triple digit heat Sunday and Monday. A significant pattern change will arrive on Tuesday with the arrival of a dry cold front. Temperatures will cool to near average values by Thursday. Breezy winds and dry conditions each afternoon will result in elevated fire weather concerns. && .DISCUSSION... Saturday through Monday: A ridge will amplify across the western US this weekend as a deep upper level low churns in the Gulf of Alaska. 850mb temperatures will warm to 26 to 28C in response, corresponding to widespread highs in the upper 90s to low 100s for the Inland Northwest. On Sunday, as the Gulf of Alaska low begins to inch toward the British Columbia coast, repositioning the center of the ridge slightly eastward. With the flow aloft shifting to the south, temperatures will warm even further. 850mb temperatures around 29 to 31C across the Inland Northwest will bring widespread temperatures in the triple digits. Heat advisories will upgrade to Excessive Heat Warnings this afternoon as these temperatures will result in major to extreme HeatRisk across the region. Everyone who is exposed to the heat is at risk for heat related illnesses. Please consider canceling outdoor activities. Warm overnight low temperatures will result in little to no relief overnight. If you have access to air conditioning, use it, or find a location that does. Even a few hours in a cool location can lower risk for illness. Sunday and Monday will need to be watched for the potential for dry thunderstorms as a shortwave moves in from the southwest on Sunday and as a cold front approaches the region on Monday. For Sunday, in combination with intense heating resulting in a very unstable atmosphere, elevated moisture and instability raises these alarms. Models continue to show the strongest lift to our west and south with the probability for thunderstorms remaining below 15 percent. Some high resolution models are showing isolated showers to move northward across central Washington Sunday afternoon, but confidence remains too low to include it in the forecast. As the deep low approaches the British Columbia coast on Monday, moisture and high level clouds will spread eastward into the rest of eastern Washington and north Idaho ahead of an approaching cold front. The threat for thunderstorms will also spread eastward as this mid level moisture increases elevated instability. Currently the best chances will be across the north Cascades, the northeast mountains, and north Idaho with a 10 to 15 percent chance. In addition to this risk, a return to onshore flow will tighten the cross-Cascade pressure gradient with breezy winds through the Cascade gaps and central Washington Monday evening. /vmt Tuesday through Friday: A cooldown is finally on the horizon! A deep center of low pressure is on track to move into northern British Columbia on Tuesday which will send an associated dry cold front sweeping across the Inland Northwest, bringing some long awaited relief from the heat. However, all good things come at a cost. With the cooling temperatures will come an increase in winds due to a pressure gradient setting up over our region with the area of low pressure to our north and higher pressure to our south. Increased winds will create potential for the numerous wildfires throughout Eastern WA and North ID to grow and spread rapidly, especially with vegetation being primed for burning thanks to our extended spell of hot and dry conditions. Breezy winds will begin Monday night and will persist through the end of the workweek. As for specifics on temperatures, the most dramatic drop in temperatures will occur from Monday to Tuesday. Daytime highs on Tuesday will be around 10 degrees cooler than those on Monday. For most locations, this means going from triple digits on Monday to the low 90s on Tuesday. The cooling trend, though more gradual, will continue through the end of the week. By Thursday, if our current forecast pans out, Spokane will see temperatures drop into the 80s for the first time since July 4th! This will mark the end of what has been a record-breaking streak of 90-degree-or-higher days. Spokane`s previous record was 15 days in a row of temperatures climbing above 90F. If our current streak continues through Wednesday as forecasted, we`ll obliterate that record with a whopping 20 days of 90+ degree temperatures. /Fewkes && .AVIATION... 18Z TAFS: A building upper level ridge will allow VFR conditions to continue through the period. The only exception will be some hazy conditions from smoke near wildfires that may reduce visibilities. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: With the exception of smoke near wildfires confidence is high for continued VFR conditions. ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance For additional probabilistic information for NWS Spokane airports, please refer to the Aviation Dashboard on our webpage: https:/www.weather.gov/otx/avndashboard && .PRELIMINARY POINT TEMPS/POPS... Spokane 100 67 106 70 102 65 / 0 0 0 0 0 0 Coeur d`Alene 98 67 102 68 100 64 / 0 0 0 0 0 0 Pullman 97 64 103 63 97 59 / 0 0 0 0 0 0 Lewiston 106 73 111 75 106 71 / 0 0 0 0 0 10 Colville 98 57 103 60 101 56 / 0 0 0 0 0 0 Sandpoint 96 62 100 65 99 60 / 0 0 0 0 0 0 Kellogg 96 72 100 72 100 68 / 0 0 0 0 0 0 Moses Lake 102 64 108 68 102 61 / 0 0 0 10 10 0 Wenatchee 102 75 108 75 102 66 / 0 0 0 10 10 0 Omak 104 68 110 73 107 65 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Heat Advisory until 11 AM PDT this morning for Central Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse-Lewis and Southern Nez Perce Counties-Lewiston Area-Northern Panhandle. Excessive Heat Warning from 11 AM this morning to 8 PM PDT Monday for Central Panhandle Mountains-Coeur d`Alene Area- Idaho Palouse-Lewis and Southern Nez Perce Counties- Lewiston Area-Northern Panhandle. WA...Heat Advisory until 11 AM PDT this morning for Central Chelan County-Lower Garfield and Asotin Counties-Moses Lake Area- Northeast Blue Mountains-Northeast Mountains-Okanogan Highlands-Okanogan Valley-Spokane Area-Upper Columbia Basin- Washington Palouse-Waterville Plateau-Wenatchee Area- Western Okanogan County. Excessive Heat Warning from 11 AM this morning to 8 PM PDT Monday for Central Chelan County-Lower Garfield and Asotin Counties-Moses Lake Area-Northeast Blue Mountains-Northeast Mountains-Okanogan Highlands-Okanogan Valley-Spokane Area- Upper Columbia Basin-Washington Palouse-Waterville Plateau- Wenatchee Area-Western Okanogan County. Fire Weather Watch from Sunday afternoon through Sunday evening for East Portion of North Cascades National Park/Lake Chelan National Recreation Area (Zone 697)-East Washington Central Cascades (Zone 696)-East Washington North Cascades (Zone 698)-Foothills of Central Washington Cascades (Zone 705)-Methow Valley (Zone 704). Heat Advisory from 11 AM this morning to 8 PM PDT Monday for Western Chelan County. && $$