Lewiston, ID Weather

Key Messages

- Rain will taper off through Friday morning.

- Dry and windy Friday Okanogan Valley/Highlands, Waterville Plateau, and Upper Columbia Basin leading to elevated fire weather conditions, potential for patchy blowing dust, and isolated tree damage.

- Cooler temperatures Friday into next week.

Synopsis

Rain continues through Friday morning. Central Washington will miss out on the rain, which combined with dry and windy conditions on Friday will lead to elevated fire weather conditions and the potential for patchy blowing dust. Cooler weather is expected Friday, through the weekend, and into the following week.

Discussion

Today: The weeks closed Low will push north as a upper level trough dips in from the Gulf of Alaska. The Low center will pass over Western MT and swing a cold front through the Inland Northwest during the morning hours. Rain chances will diminish west to east as the front passes. Short term ensembles have a 25-75 probability of an additional 0.1-0.3 of an inch of precip through Friday. Most will fall through the morning hours. As the backside of the trough moves into the region, a low level jet of 50-60 kts will bring push breezy north to south low level winds through the Okanogan Valley and across the Western Columbia Basin. Wind speeds in the low to mid level (800-750mb) are in the 30-40 kt range. Surface winds in aforementioned areas can expect sustained winds in the upper teens-20 mph and gusts into the upper 30-40 mph range. The Waterville Plateau has a near 50 percent probability of isolated gusts into the 50s. A wind advisory has been issued for the areas of concern. Winds will start to decrease mid afternoon as A ridge starts to fill in behind the exiting trough. Highs will be in the 50s to low 60s. Overnight lows will be 20s to low 30s.

Saturday through Thursday: Saturday will be be mainly dry as the region is under a dry slot between the exiting Low and another one located off the coast of BC. Models continue to show a low dropping along the coast. The discrepancy comes with the track of the low. Around 60 percent of the ensembles have the Low pushing through the North Oregon and bringing another round of light precip to the region. The other 40 percent have the Low fizzling out along the coast line with a stronger ridge over the region. Highs for the period will be in the upper 40s and 50s. Overnight lows will be in the upper 20s and 30s. /JDC

Aviation

12Z TAFS: West to northwest winds are increasing at all terminals as a cold front slides through. This is ushering drier air in to the region with moderate to high confidence for ongoing IFR/MVFR conditions to quickly lift between 12-14z in Washington and 14-16z in the Idaho Panhandle. This will also bring a decrease in rain from west to east with the band of precipitaiton shifting east of the ID-MT border by 18z. Gusty winds will become the main aviation impact. Most terminals will experience gusts 15-25kts with locally 35kts around Omak, Grand Coulee, and Moses Lake. There is a small risk for blowing dust between Omak and Grand Coulee though this comes with very low confidence.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate to high confidence for IFR/MVFR conditions to lift but moderate uncertainty for precise hour. One scenario would be for a slowly evolution of low ceilings lifting from 900 ft AGL to 3000 ft AGL between 12-17z for terminals such as KGEG-KSFF-KCOE-KPUW. A second scenario would be for the IFR/MVFR ceilings to become scattered quickly as the drier air punches in. /sb

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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