Chelan Falls, WA 98858 Weather

Key messages

- Patchy fog overnight.

- Cool temperatures, light winds, and a slight chance (15-30%) for sprinkles or very light rain Saturday evening.

- Rain chances increasing 20-60% late Saturday night into Sunday. Light rain accumulations up to a tenth of an inch expected over Southeast WA and the southern Idaho Panhandle.

- Dry conditions Sunday evening through Wednesday.

Synopsis

Mid and high clouds increase Saturday bringing a small chance of sprinkles and showers to eastern Washignton and north Idaho in the evening. Dry air filters in Sunday and conditions remain seasonal and dry through Wednesday.

Discussion

Saturday and Sunday: The upper low offshore continues to fill in and slide to the south towards the northern California coastline Saturday evening. This will bring weak synoptic ascent into the region Saturday afternoon and evening, bringing small chances for light rain (5-15% chance over central WA, 10-30% chance for eastern WA and north ID). PWATs increase to 110-130% of normal Saturday afternoon and evening but dry air near the surface will only allow for sprinkles to a light drizzle mainly east of Ritzville. Rain amounts will be very light around a trace to a tenth of an inch through Saturday night. Light rain continues into Sunday for southeast WA and the central and southern ID Panhandle ahead of drier air filtering in from the west. Clouds will erode in the late morning and early afternoon Sunday in central and eastern WA and the late afternoon around sunset in north ID. The chances of a tenth of an inch or more of rain from Saturday afternoon to Sunday are around 20-50% south of I-90 and east of US-395.

Monday through Saturday: High pressure builds into the region Monday bringing dry conditions and seasonal temperatures in the upper 40s to mid 50s. This ridge will be slightly disrupted Monday night into Tuesday by a shortwave moving through central BC and AB, bringing a small chance for snow showers in the Cascades above 3500 feet. Impacts look very minimal from this system. The ridge strengthens behind this weak wave Wednesday but chances for precipitation increase Wednesday night as troughing approaches the region. Models are in some disagreement with the position and strength of the placement of this trough but the overall message is there is a signal for unsettled conditions to return mid to late next week. Global ensembles continue to show a 60/40 split towards dry conditions continuing but this will change in the coming days as confidence increases. /DB

Aviation

06Z TAFS: The HREF has miserably failed with the evolution of fog and low stratus this evening over the Palouse and Spokane area this evening. The model that has the best handle on the current situation for KGEG-KSFF-KPUW fog and low stratus is the high resolution Canadian model HRDPS. There is low confidence what happens but a flow reversal to east-northeast is expected tonight in the next few hours. The strength of this flow does not appear strong enough to make a huge difference in eroding the fog and low stratus through at least 15Z or so and actually reinforces the potential for it to continue at KGEG with upslope flow from downtown Spokane. NBM transport winds for KPUW are around 5 kt from the east which is most likely not strong enough to erode it before sunrise. By 15-18Z, day time heating will commence and at least lift this layer into an MVFR stratus and eventually erode. A low stratus deck developing north of KMWH has a 20% chance to bring degraded ceilings to KMWH around 12Z as boundary layer winds pick up out of the north. Once the fog and low stratus are gone Saturday morning, the area will be left with a layer of mid to high clouds. Top down moistening will occur late Saturday afternoon as weak synoptic ascent overspreads the region. There is a 15-30% chance of sprinkles to light rain at KGEG-KSFF-KCOE-KPUW-KLWS from 00Z-06Z Sunday with the highest chance for KPUW. Ceilings are forecasted to stay VFR through this period but models indicate potential to drop to MVFR after 6Z Sunday.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Very low confidence in the fog and low stratus through 18z. High confidence in VFR conditions from 18z Saturday to 06Z Sunday.

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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 52 33 52 37 51 32 / 0 0 0 20 0 0 Coeur d'Alene 53 33 52 37 52 33 / 0 0 0 20 10 0 Pullman 52 32 47 34 48 30 / 0 0 0 40 40 0 Lewiston 55 37 52 42 53 38 / 0 0 10 50 50 0 Colville 52 27 54 27 51 22 / 0 0 0 10 10 0 Sandpoint 52 30 51 33 50 29 / 0 0 0 10 10 0 Kellogg 54 33 51 36 51 33 / 0 0 0 20 20 0 Moses Lake 54 28 55 32 54 26 / 0 0 0 0 0 0 Wenatchee 51 34 54 37 52 34 / 10 0 0 0 0 0 Omak 51 31 54 34 51 29 / 0 10 0 10 0 0

Watches, warnings and advisories

WA: None. ID: None.