St. John, WA 99171 Weather

Key messages

- Light snow in the east slopes of the Cascades into Friday morning above 3000 feet. Less than half of an inch of new snow expected.

- A chance (20-50%) of rain primarily over Southeast WA and the southern ID Panhandle late Saturday night into Sunday. Light rain accumulations up to a tenth of an inch expected.

Synopsis

Low pressure will remain off the coast through Friday, then will eject inland over the weekend. Valley rain and mountain snow is forecast at times on Friday and through the weekend with periods of very light snow impacting the Cascade passes. The incoming low pressure system will also bring increasing chances for light rain late Saturday night into Sunday across Southeast WA and the southern ID Panhandle.

Discussion

Friday through Sunday: The upper level trough off coast continues to weaken and fill in, but will leave cool and unsettled conditions present in the region through this weekend with temperatures near average to slightly below average. Shower chances Friday will be limited to the east slopes of the Cascades. Snow levels will be around 3000-4500 feet, so there is a small chance (10%) for 1" or more at Washington Pass.

The forecast for Saturday evening looks drier than it was looking last night but there are still a small chance for sprinkles (5-20% chance), mostly in central/eastern Washington and the southern ID Panhandle. Evening temperatures will fall into the low to mid 40s, accompanied by light northeast winds around 1-4 mph. The chance of seeing 0.25 inches or more of rain from 4 AM Saturday to 4 AM Monday has drastically dropped to less than 5 percent outside of the lower Palouse and L-C valley. The chances are around 10-20% with the highest on the Camas Prairie.

Shower chances Sunday will be limited to southeast Washington east of US-395 and the southern ID Panhandle as the trough moves ashore. The best dynamics appear to be trending southward in the model runs so the chances of a quarter inch or more of rain through Monday morning have dropped off significantly to less than 5 percent outside of the lower Palouse and L-C valley. The chances are around 10-20% with the highest on the Camas Prairie.

Monday through Thursday: Models are still in good agreement of a building ridge Monday which will bring dry conditions and slightly above normal temperatures in the low to mid 50s. High temperatures could under perform if stratus/fog layers develop but confidence is low at these lead times. Ensembles are trending towards unsettled conditions returning towards late next week (into Thursday) with potential for showers and high mountain snow. /DB

Aviation

12Z TAFS: VFR conditions are expected to prevail through the 24-hour period at all TAF sites except for KEAT, where there is a 20 percent chance of MVFR ceilings developing between 12Z and 18Z. This is due to easterly flow in the boundary layer pooling moisture up against the east slopes of the Cascades. For the rest of Eastern WA and North ID, the boundary layer will trend drier. Mid and high level clouds will thicken through the period. Winds will generally be less than 10 kts except for at KCOE, where breezy northerly winds coming down the Purcell Trench will bring potential for sustained speeds of 15-20 kts and gusts up to 25 kts.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for VFR conditions prevailing except for at KEAT. There is low confidence that low stratus with MVFR ceilings will develop at KEAT this morning.

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

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 50 33 51 36 50 30 / 0 0 0 20 10 0 Coeur d'Alene 50 33 53 36 50 32 / 0 0 0 10 10 0 Pullman 50 32 50 33 44 29 / 0 0 0 10 30 0 Lewiston 54 37 54 41 49 36 / 0 0 0 30 50 0 Colville 49 27 52 25 53 22 / 0 0 0 20 0 0 Sandpoint 49 30 52 31 50 29 / 0 0 0 0 10 0 Kellogg 51 33 54 36 50 32 / 10 10 0 10 10 10 Moses Lake 53 28 53 32 54 27 / 0 0 0 20 0 0 Wenatchee 50 34 49 37 55 34 / 10 0 30 10 10 0 Omak 48 31 49 34 52 31 / 0 0 10 10 0 0

Watches, warnings and advisories

WA: None. ID: None.