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Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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443 FXUS66 KOTX 211006 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 306 AM PDT Sun Jul 21 2024 .SYNOPSIS... Very hot temperatures continue through Monday, with widespread triple digits value. A significant pattern change arrives Tuesday with a dry cold front. Temperatures cool to near average values by Thursday. Breezy winds and dry conditions each afternoon will result in elevated fire weather concerns. && .DISCUSSION... Sunday through Monday: A high amplitude upper level ridge is centered over northern Alberta as a closed upper level low slowly inches toward the British Columbia coast. Resultant deep southerly flow aloft has allowed elevated monsoonal moisture to stream northward as a shortwave slides along western Oregon. Current radar imagery shows scattered thunderstorms across western Oregon early this morning. As the shortwave progresses northward into Washington, elevated moisture and thunderstorm chances will increase across central Washington this afternoon and evening. Overall lift does not look very supportive of widespread thunderstorms, but the elevated moisture combined with orographic enhancement over the Cascades will bring a 10 to 15 percent chance of isolated shower and thunderstorm activity. Any showers or thunderstorms would increase the risk for lightning caused fires and breezy outflow winds. 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 20 percent chance.The return of strong onshore flow will tighten the cross- Cascade pressure gradient with breezy winds through the Cascade gaps and central Washington Monday evening. Winds look to pick up around sunset on Monday as a cold front moves into western Washington. Despite a slight increase in minimum relative humidities on Monday, these winds will elevate fire weather concerns. With regard to temperatures, widespread triple digits are expected across the Inland Northwest today. Widespread smoke and haze from area wildfires may dampen high temperatures a couple degrees, but it will still be very hot regardless with many spots forecasted to break their daily high temperature record. The return to onshore flow as the low moves onshore will slightly cool the air mass on Monday, but it will still be very hot. 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. /vmt Tuesday to Saturday: An long-wave upper trough gradually shifts inland through this week to bring a relative cooling trend, periodic breezy conditions which might sync up with some low RH values to bring near critical fire weather conditions, and some very limited shower chances. Tuesday and Wednesday continue to see above normal temperatures, but a shortwave pivoting into the region Wednesday will bring a few more cloud and some passing shower chances. The main shower chances will be found near the southeast periphery of the CWA and near the northeast mountains. Some guidance (particularly the Canadian model) show broader shower chances with this incoming wave, but 66% of the models are drier. Still this will be monitored. Most of the convective instability sits east/southeast of our region, so I don`t have any thunderstorms in the forecast. More notable on Wednesday and continuing into Thursday will be increased winds. Speeds around 10-20 mph (with higher gusts of 25-40 mph) will be possible, particularly near the lee of the Cascades across the Waterville Plateau to the West Plains of Spokane county and the Palouse. Afternoon minimum RH values will be near critical values, so this will be monitored for fire weather concerns. However temperatures are forecast to cool slightly below normal by Thursday. Friday continues to feature slightly below normal readings, before warming closer to normal Saturday. The forecast remains dry for the end of the week and bit breezy, but not as breezy as Wednesday and Thursday. /Solveig && .AVIATION... 12Z TAFS: An 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 104 69 100 63 93 60 / 0 0 10 10 0 0 Coeur d`Alene 102 68 98 62 91 59 / 0 0 10 10 0 0 Pullman 102 63 95 57 89 57 / 0 0 10 0 0 0 Lewiston 110 75 105 70 99 69 / 0 0 10 10 0 0 Colville 102 61 99 54 91 50 / 0 0 20 10 0 0 Sandpoint 99 65 96 59 90 52 / 0 0 20 10 0 0 Kellogg 100 72 98 66 91 65 / 0 0 20 10 0 0 Moses Lake 107 68 101 58 94 58 / 0 10 0 0 0 0 Wenatchee 105 74 101 64 95 64 / 10 10 0 0 0 0 Omak 107 73 106 64 98 61 / 0 10 10 10 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Excessive Heat Warning until 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...Excessive Heat Warning until 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. Red Flag Warning from noon today to 10 PM PDT this 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 until 8 PM PDT Monday for Western Chelan County. && $$