Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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213 FXUS66 KOTX 090458 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 958 PM PDT Sat Jun 8 2024 .SYNOPSIS... A weak weather system will pass through on Sunday with a chance of showers and thunderstorms. Above normal temperatures will continue though much of the week, with cooler temperatures by late next week. && .DISCUSSION... Tonight through Monday: Mid and high clouds will continue to move in tonight ahead of a short wave trough. The trough will push east across the region on Sunday, drawing up increased moisture from the southwest. Initially, a lack of large scale forcing and mostly cloudy skies will limit instability through early to mid afternoon with most areas only receiving light showers or sprinkles. This could change in the late afternoon and evening on the back side of this system as sun breaks help destabilize the atmosphere. Most unstable CAPE values increase to 300-800 J/KG, with the NBM painting the area with the best chances for thunderstorms (30%) over the North Cascades, Methow Valley, and Okanogan Highlands. This is where there will be a combination of afternoon sun breaks, and cooling aloft with the passing mid level trough. Elsewhere there will be a 10-20% chance of thunderstorms as the atmosphere briefly destabilizes. Drying aloft combined with a short wave ridge will bring quieter weather on Monday, except for a 20% chance of showers or a stray thunderstorm over the north Idaho Panhandle mountains in the afternoon. JW Monday night to Saturday: The Inland NW will find itself in a somewhat progressive flow, with periodic breezy conditions and limited shower chances. A shortwave ridge tracks from the Cascades to the Continental Divide Monday evening into Tuesday morning, while a shortwave trough moves in from the west Tuesday. That shortwave trough will bring some clouds and it will bring shower chances to the Cascade crest, expanding to the northeast WA and north ID mountain zones in the afternoon. Some showers may slip by the Spokane/CdA area then too, but these would be isolated in nature. The system also comes with breezy/gusty winds as a 110kt+ jet streams pushes over the top of the region. The winds increase for the afternoon and evening hours, with speeds of 10-20 mph and gusts of 20-40 mph. The higher range of those will be around the lee of the Cascades to central WA. While RH values will not be critical values, they will still be dry and the whole area is starting to dry out so this may be of concern to the fire weather community. Winds decline through the late evening and especially the overnight. Wednesday and Thursday the area see the precipitation chances wane with a shortwave ridge moving back into the region, though look for breezy conditions again Wednesday with gusts near 15-25 mph. Friday and next Saturday another trough moves into the region, though models disagree over the precise timing and track. It will bring some precipitation chances again. However at this time 60-70% of the ensembles keep the system more focused near the Cascades and northern mountains, while 30-40% bring it more directly across the CWA with broader precipitation chances and t-storm chances. I trended PoPs a bit higher on next Saturday to account for that uncertainty but keep the higher PoPs over the Cascades and closer to the Canadian border. This system will also come with another increase in the breezy conditions, especially Friday with gusts near 20-30 mph. Temperatures fluctuate through this period, holding above normal Tuesday, dropping closer to normal Wednesday, rebounding toward the mid to upper 70s to mid-80s Thursday and Friday, before cooling closer to normal again next Saturday. /Solveig && .AVIATION... 00Z TAFS: VFR conditions will prevail. An incoming weather system will bring an increase in mid to high level clouds from the south tonight. This will bring a 20 to 30 percent chance for showers and thunderstorms over the Cascades and far southeast Washington and the southern Panhandle around 18-19Z. These chances will spread east and north through the mid to late afternoon as the weather system moves across region. The main concern with thunderstorms that develop will be gusty outflow winds with gusts of 25-35 kts, brief downpours, and small hail. The probabilities for showers or thunderstorms to move over a TAF site are too low (less than 25% probability) to include in the TAFs at this moment. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Confidence remains high for VFR conditions through Sunday afternoon, except for localized restrictions under any thunderstorms that develop. ----------------------- 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 55 78 54 80 54 82 / 0 10 20 0 0 10 Coeur d`Alene 53 77 53 76 52 77 / 0 10 20 10 0 20 Pullman 53 73 53 74 51 78 / 0 10 10 0 0 10 Lewiston 61 84 59 86 58 88 / 0 20 10 0 0 0 Colville 49 78 48 78 49 81 / 0 20 30 10 0 30 Sandpoint 50 77 52 77 51 74 / 0 10 40 20 0 20 Kellogg 54 76 56 73 55 75 / 0 20 30 10 0 10 Moses Lake 58 84 55 86 54 86 / 0 20 20 0 0 0 Wenatchee 63 84 58 87 59 80 / 10 20 10 0 0 0 Omak 59 81 53 84 54 86 / 0 30 20 0 0 10 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$