Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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863 FXUS66 KOTX 060952 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 252 AM PDT Sat Jul 6 2024 .SYNOPSIS... Weather conditions are expected to be hot and dry the next seven days. Northerly winds will be breezy on Saturday, otherwise light through next Tuesday. Next threat for increased winds will be Wednesday next week. && .DISCUSSION... ...SIGNIFICANT HEATWAVE TO IMPACT THE INLAND NW THIS WEEK... Today through Friday: A significant heatwave is poised to impact the Inland Northwest this week delivering widespread triple digit heat. Confidence remains high in the upcoming forecast with very little spread in the models. The upper-level ridge responsible for the upcoming heat wave remains centered off the Western US Coast but will make the trek inland beginning Sunday and remain anchored overhead through midweek. Given its placement this morning, one last shortwave is dropping down its eastern flank into Western MT and skirting far North Idaho. This has resulted in some shower activity in proximity of Bonners Ferry eastward into Troy, MT. While no precipitation has been reported, breezy northerly winds from the rain cool air are being felt in the northern Purcell Trench. A few lightning strikes have also been observed in NW MT. Much of the region will contend with light to locally breezy north to northwest winds today in the wake of this system. The breeziest winds will channel down the Okanogan Valley with speeds of 10-20 mph. The good news is these winds will peak before midday then begin to weaken during the warmest and driest part of the day, thus no fire weather highlights are anticipated. Another area that will be breezy, especially in the afternoon will be far SE WA and into the L-C Valley. The light gradient winds will align with the typical diurnal winds of this direction resulting in speeds near 15 mph at times with gusts up to 25 mph. Temperatures today will be within a degree of those experienced on Friday topping out in the 90s for most communities; a few low 100s in the deep Basin and upper 80s in the cooler northeastern valleys. The airmass will remain very dry with afternoon RH values in the teens. As the ridge migrates inland Sunday into early next week, increasing subsidence will result in a net warming of the air mass with 850mb temperatures surging from 23C on Saturday to nearly 30C Tue- Wed. This will equate to 3-4 degrees of warming each consecutive day and widespread triple digit heat. Overnight lows will follow suite and struggle to cool out of the 60-70s. This compounding effect will result in moderate to major heatrisk with some areas likely coping with extreme conditions. At this time, Tuesday and Wednesday look to be the peak of the heat wave as for the hottest temperatures however the reprieve will be dismal Thursday-Saturday with temperatures only backing off into the 90s. Please consider those vulnerable to the heat (elders, children, pets) and check on them frequently. Be sure to take proper precautions when working in the heat such as taking frequent breaks, staying hydrated, and finding times to cool off in air condition when applicable. The incoming heat will also result in increased fire danger with dry fuels becoming extremely volatile to ignition. Although winds will be light, the hot and unstable weather conditions could allow for rapid fire spread, especially where sloped terrain plays a role. Current models are indicating the first blow to the upper-ridge coming around Wednesday. If this comes to fruition, this will be the first concern for increased winds and potential for critical fire weather conditions. There is a lot of uncertainty on the magnitude of these winds but any winds when it is 100 degrees with RH values in the teens will be a major concern. Would not rule out some local breeziness bleeding through the Cascade Gaps prior to the more widespread breeziness. Once the ridge begins to flatten, winds will become a more common nuisance for the Cascade Gaps and when the next shortwave arrives, on a more widespread basis. Fire danger indices will be on a new level following this incoming heat wave. At this time, there are little to no signs of precipitaiton throughout the next week. There is a ghost of a chance for an isolated t-storm to form in the higher terrain in the N Cascades SUN-MON coming with a 5% chance. The next threat for any lightning would be around the Blue Mountains WED-THU yet this only has support from around 15% of a 100 member ensemble and remains out of the forecast at this point. The latest National Blend of Models gives Spokane International a 12% chance for hitting 108F or warmer on WED. The current all time record is 109F set back in the June 29th heatwave of 2021. /sb && .AVIATION... 00Z TAFS: Smoke at the Pioneer Fire on the north end of Lake Chelan has become more active. As the night time inversion sets up, drainage winds are expected to push smoke down the lake toward Chelan and onto the Waterville Plateau each evening the next several days. A band of hazy conditions is forecast for the Waterville Plateau to Ritzville and then up to Spokane. Do have mention of haze for GEG, but not expecting large visibility issues. A weak dry cold front will bring a push of stronger winds down the east slopes of the Cascades through 08z. Gusts up to 30 mph will be possible at Wenatchee, Chelan, Entiat, and on the Waterville Plateau. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in VFR conditions. Low confidence for localized visibility reductions due to smoke. ----------------------- 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 92 62 97 65 100 66 / 0 0 0 0 0 0 Coeur d`Alene 89 61 92 64 96 66 / 0 0 0 0 0 0 Pullman 88 58 93 61 96 62 / 0 0 0 0 0 0 Lewiston 99 67 102 70 105 71 / 0 0 0 0 0 0 Colville 89 54 94 57 98 60 / 0 0 0 0 0 0 Sandpoint 88 56 91 57 95 61 / 0 0 0 0 0 0 Kellogg 84 62 89 65 92 68 / 0 0 0 0 0 0 Moses Lake 98 64 102 67 105 68 / 0 0 0 0 0 0 Wenatchee 99 69 102 71 105 74 / 0 0 0 0 0 0 Omak 99 65 102 68 105 70 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Heat Advisory from noon Sunday to 10 PM PDT Friday for Central Panhandle Mountains-Northern Panhandle. Excessive Heat Warning from noon today to 10 PM PDT Friday for Coeur d`Alene Area-Idaho Palouse-Lewis and Southern Nez Perce Counties-Lewiston Area. WA...Heat Advisory from noon Sunday to 10 PM PDT Friday for Northeast Mountains-Okanogan Highlands. Excessive Heat Warning from noon today to 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 from noon today to 10 PM PDT Friday for Western Chelan County. && $$