Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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418 FXUS66 KOTX 071739 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1039 AM PDT Sun Jul 7 2024 .SYNOPSIS... Weather conditions are expected to be hot and dry the next seven days. Winds will be light through Tuesday. Breezy to gusty winds return Wednesday with increasing fire weather concerns. && .DISCUSSION... ...SIGNIFICANT HEATWAVE TO IMPACT THE INLAND NW THIS WEEK... Key messages for the week - Hot to very hot temperatures will be in place through Wednesday increasing the risk for heat related illnesses - Tuesday and Wednesday will deliver the hottest afternoon temperatures and warmest overnight lows - No precipitation is in sight throughout the week - Smoke from the Pioneer fire will impact air quality around Lake Chelan and nearby communities at times - The weakening of the heat on Wednesday will bring breezy to gusty winds increasing fire weather concerns - Prior to Wednesday, the heat + drying of fuels coupled with an unstable atmosphere will result in elevated fire weather conditions - Temperatures cool 10 degrees Thursday then look to slowly warm again heading into next week prolonging the risk of above normal temperatures Sunday through midday Wednesday: A significant heatwave is poised to impact the Inland Northwest this week delivering widespread triple digit heat. Confidence has not changed and remains high with very little spread in the models. High temperatures will warm from the 90s to lower 100s Sunday to 100`s Monday, Tuesday, and Wednesday. Tuesday and Wednesday will feature the hottest readings of this heatwave with numerous communities between 105-110F. Excessive heat warnings are meant to capture the areas that will carry the greatest risk for overnight lows of 65-75F offering little to no relief at night. Valleys of NE WA and N ID carry a higher probability of cooling into the 50s to 60s which has led to advisories vs warnings. The heat is courtesy of a anomalously strong upper-level ridge of high pressure that promotes subsidence and atmosphere warming and also allows the heat that has been festering across the Southwest to expand northward. Keep the sun glasses handy as any moisture or cloud cover for that matter will be deflected well around the Northwest. The Pioneer Fire burning south of Stehekin on Lake Chelan will have high probabilities to remain active given the projected weather pattern. Smoke from the fire will settle into the lake basin overnight with a drift downlake toward Manson and Chelan overnight and uplake during the day. Deeper plumes of smoke during the day will bring the potential for smoke into the Methow Valley as well. Air quality is likely to be impacted at times. Please refer to fire.airnow.gov for the latest readings and smoke outlooks. Wednesday afternoon through Saturday: Changes arrive in this period with the initial blow and flattening of the upper-level ridge. This will usher a dry "cool" front through the region with the most impactful element coming as breezy to gusty winds. This has been advertised for a few days and confidence is starting to grow. Strongest winds look to channel through the Cascade Gaps and spill into the Western Columbia Basin but an increase in winds will definitely be noticeable for many across the Eastern Basin, Spokane-Cd`A Area, Palouse, and L-C Valley. Uncertainty right now is whether these eastern zones will experience strong enough wind speeds for any fire weather highlights. The highest probabilities for sustained winds greater than 15-20 mph are focused around Chelan, Wenatchee, Waterville, Wilbur, Ephrata, Moses Lake, and to some degree Ritzville (40-70%) and continue to increase with each run. The eastern Basin (Spokane to Pullman to Lewiston) are close to 10-20% at this time. Nonetheless, any wind will be a major concern with temperatures in the 100s, RH in the teens, and following an extended period of hot weather. Temperatures will be 10-15 degrees cooler on Thursday with a flatter ridge in place but still 10 degrees above normal as readings remain in the 90s. The air mass also becomes quite dry behind the front with PWATs lowering from 0.50 to 0.25 Wednesday night and Thursday so despite the cooling, RH values will remain very low. The good news, if the winds can calm overnight, the drier air should allow for more adequate cooling at night. Friday will feature similar afternoon readings then the thermometer will be on the rise again for the weekend. How warm? This comes with a moderate amount of uncertainty. Models are having a hard time resolving the placement of an offshore low and the interior ridge which is impacting temperatures. It is conceivable that temperatures rebound back into the upper 90s or even lower 100s. When this offshore low rotates inland some point early next week, will be keeping a close eye on the bout of wind and potential for lightning. /sb && .AVIATION... 18Z TAFS: VFR conditions will prevail. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in 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 96 67 100 69 103 70 / 0 0 0 0 0 0 Coeur d`Alene 92 63 97 67 100 68 / 0 0 0 0 0 0 Pullman 93 60 96 63 100 65 / 0 0 0 0 0 0 Lewiston 101 70 105 72 108 74 / 0 0 0 0 0 0 Colville 93 57 98 60 101 61 / 0 0 0 0 0 0 Sandpoint 89 57 93 60 97 63 / 0 0 0 0 0 0 Kellogg 88 65 94 68 98 70 / 0 0 0 0 0 0 Moses Lake 101 65 104 68 108 72 / 0 0 0 0 0 0 Wenatchee 101 74 105 76 107 77 / 0 0 0 0 0 0 Omak 102 70 105 72 107 73 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Heat Advisory from noon today to 10 PM PDT Friday for Central Panhandle Mountains-Northern Panhandle. Excessive Heat Warning until 10 PM PDT Friday for Coeur d`Alene Area-Idaho Palouse-Lewis and Southern Nez Perce Counties- Lewiston Area. WA...Heat Advisory from noon today to 10 PM PDT Friday for Northeast Mountains-Okanogan Highlands. Excessive Heat Warning until 10 PM PDT Friday for Central Chelan County-Lower Garfield and Asotin Counties-Moses Lake Area- Northeast Blue Mountains-Okanogan Valley-Spokane Area-Upper Columbia Basin-Washington Palouse-Waterville Plateau- Wenatchee Area-Western Okanogan County. Heat Advisory until 10 PM PDT Friday for Western Chelan County. && $$