Otis Orchards-East Farms, WA Weather

Key Messages

- Light rain chances through Tuesday morning with the first of two weather systems moving through. Lingering showers in mountains through Tuesday afternoon.

- On Tuesday night, another colder system moves in, with snow levels lowering to 2500 to 4000 feet. Mountain snow will start Tuesday night and continue through Thursday, bringing winter travel over mountain passes in the Cascades.

Synopsis

The first of two weather systems moved across the area today and brought light precipitation, especially across southeast WA and the ID Panhandle. A second, colder weather system moves in on Tuesday night through Thursday night. This will drop snow levels to 2500 to 3000 over the Cascades and north- central WA and down to around 4500 feet in the ID Panhandle. Valley rain and mountain snow is expected, with winter travel conditions over mountain passes.

Discussion

Today through tomorrow afternoon: An upper-level low off the Washington coast is moving southeastward, and will bring a few rain bands through the forecast area as the day goes on. Snow levels are 5000 to 6000 feet, and little to no snow accumulations are expected. Precipitation totals will overall be low across the Inland Northwest, with 0.05-0.10 inches expected. Higher rainfall totals will be confined to far SE Washington and the central ID Panhandle, where rainfall totals could reach 0.3-0.35 inches. Though the low will move out of the area by late tonight, residual moisture will keep showers across the mountains, WA/ID Palouse, and ID Panhandle. For the Spokane to Wenatchee area and southward, there will be a break in precipitation Tuesday morning through afternoon.

Tuesday evening through Thursday: On Tuesday evening, another stronger low pressure system will move southward down into the forecast area. This will be a colder system, with snow levels lowering to 2000 to 3000 feet. Snow will start late Tuesday night in the Cascades, then will start in the northern mountains and ID Panhandle early Wednesday morning. Stevens and Washington Passes have the highest probabilities of receiving 6 inches or more of snow over 48 hours, with a 35-40% chance. Other passes, including Sherman, Lookout, and Blewett Passes, have a 15% chance or less of 4 inches. This will create winter driving conditions at Stevens and Washington Pass, and a Winter Weather Advisory has been issued for these passes from Tuesday afternoon through Wednesday afternoon. Elsewhere, expect light precipitation. Temperatures will be cooler after the low moves through, with highs in the 40s and low 50s and lows in the 30s.

Friday through Monday: The low will remain just off the Washington coast for Friday and Saturday, weakening each day. As it weakens, chances for precipitation decrease. Main chances for showers are in the mountains due to orographic lift. Long-range models show snow levels dropping to 2000 feet over north central Washington, but given the decrease in precipitation chances, snow accumulations are not expected at this elevation. Any lingering showers will be light. Sunday into monday, the low will shift southward and a ridge will build into the area, prompting warm-up into Monday. Ensemble clusters show 80% support for this pattern, favoring a warming trend into Monday. /AS

Aviation

00Z TAFS: The band of steady rain has lifted north of KGEG/KSFF/KCOE wit isolated to scattered shower activity behind it which will linger into Tuesday mainly over the ID Panhandle and eastern third of Washington. Rain has moistened the boundary layer considerably, with high resolution model data suggesting an increase in IFR and MVFR stratus over Northeast Washington and the Idaho Panhandle tonight including KGEG/KSFF/KCOE, and eventually KPUW/KLWS later tonight (around 12z). Drier air in the boundary layer in Central WA has a better potential for continued VFR conditions including KEAT/KMWH. Stratus will linger into Tuesday morning before increasing southwest winds in the boundary layer help lift and break up the stratus.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is high confidence in increasing IFR and MVFR stratus over Northeast Washington into the Idaho Panhandle tonight into Tuesday morning including KGEG/KSFF/KCOE. Confidence in restrictions is lower for KPUW/KLWS as the boundary layer is moist but boundary layer winds not as favorable for low ceilings. Shallow ground fog could also form in the LC Valley with any breaks in the cloud cover tonight. JW

-----------------------

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