Lewiston, ID 83501 Weather

Key Messages

- Dry weather continues through Wednesday with mild afternoon temperatures.

- Breezy winds down the Okanogan Valley on Tuesday.

- Cooler weather with increased precipitation chances Thursday night through the weekend.

Synopsis

Dry weather is expected through Wednesday, with variable cloud cover and mild temperatures. Cooler weather and increasing precipitation chances arrive Thursday through the weekend.

Discussion

Today through Wednesday: The Low has finally reached the California coastline and still pushing upper level clouds across the Pacific Northwest. Dry, warm conditions are expected over the Inland Northwest through most of Wednesday. Precip chances across the region remain near 0 percent through Wednesday. Winds will be generally calm except a brief period of breezy winds down the Okanogan Valley on Tuesday morning with gusts into the upper 20 mph range. Omak has a 30-50 percent probability of gusts near 30 mph. The midweek highs will be in the 60s and low 70s. Overnight lows will be in the upper 20s and 30s. Overnight patchy frost could impact any remaining gardens and sensitive seasonal plants.

Late Wednesday through Friday: The Low finally ejects northeast toward Montana as a trough moves into the Pacific Northwest overnight Wednesday into Thursday. A wrap around band of moisture will bring increased shower chances to Southeast WA and the Idaho Panhandle on Thursday and Friday with a 40-80 percent probability of at least a tenth of an inch. A trough pattern will be over the Pacific Northwest behind the exiting Low. Friday will have mountain showers with breezy winds across the Basin. Wind speeds will be teens with gust into the 25-35 mph range for most. Waterville Plateau and Southeast WA have a 20-40 percent probability of reaching 40 mph gusts. Temperatures will trend cooler. Thursday and Friday highs will be in 50s to low 60s. Overnight lows will be in the 30s.

Saturday through Monday: Through the weekend, models are struggling on the incoming low and precip chances. The 3-7 day cluster analysis shows a near 50/50 split on whether the Inland northwest will be under a flat ridge or widespread precip Low. The consensus is keeping the precip on the west side of the Cascades. Current forecast keeps the small chance of showers across the Inland Northwest. If the drying trend continues, the precip chances will likely start to decline. Snow levels dropping down to around 4000 feet through the weekend. Back country trekkers should prepare for cold, possibly light snow conditions. Highs will be in the 50s to low 60s. Overnight lows will be in the upper 20s and 30s. /JDC

Aviation

12Z TAFS: Mid and high clouds will continue to stream across the region under southwest flow aloft. This will promote VFR conditions through the period with ceilings well above 10k ft AGL. Winds will increase from the north through the Okanogan Valley and northeast through the Purcell Trench of north Idaho this morning. Gusts up 25-30 mph are expected at KOMK before 20z. Lighter wind gusts of 15-20 mph will reach KMWH-KCOE. The midlevel clouds will decrease Tuesday afternoon but scattered to broken high clouds will remain in place. Lighter winds return region-wide Tuesday evening and night.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in VFR conditions. High confidence in breezy north winds through the Okanogan Valley Tuesday morning. Moderate confidence for a few hours of gusts around 15kts at KCOE, KGEG, and KMWH.

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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