Sprague, WA 99032 Weather

Key messages

- Patchy fog overnight.

- Cool temperatures, light winds, and a slight chance (5-15%) 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 Monday through Wednesday.

Synopsis

An influx of mid and high clouds over the region through Saturday night with an increasing risk for sprinkles or light rain Saturday evening into Sunday morning across Southeast WA and the southern ID Panhandle. Seasonal temperatures with dry conditions Monday through Wednesday.

Discussion

Tonight-Sunday: The deep low spiraling off the WA Coast will become stretched and slowly limp through the region. Mid and high clouds will continue to stream inland ahead of the low with periods of sprinkles and/or light rain showers Saturday evening through Sunday as the remnants of the system passes through. As mentioned in the previous discussion, rain probabilities for Saturday evening 5-11PM have come down quite a bit given the weakening nature of the passing wave. Precipitation chances vary anywhere from 5-30% for North Idaho and the eastern third of WA with mean QPF amounts between a trace and 0.02". This leads to increasing confidence for very light precipitation if any at all for most of the trick-or-treaters in these areas. Central WA will remain dry. Rain chances will increase closer to 40-70% for extreme southeastern WA around Asotin County and into the Camas Prairie and lower Idaho Palouse Saturday night with a 20% chance for picking up a wetting rain (0.10"). Winds through the period will be light from the north and northeast through Sunday morning then shift around to the west and northwest. For the most part, speeds will be less than 10 mph though some localized channeling tonight and Saturday morning will lead to winds of 10-15 mph for the Okanogan Valley and Purcell Trench of North Idaho.

Monday-Wednesday: A ridge of high pressure builds into the region starting Sunday night, anchors overhead on Monday then begins to receive some blows from Pacific waves on Tuesday and Wednesday. This is shaping up to be a dry period for most areas of the Inland NW. There are several variations of the waves coming into the ridge Tuesday and Wednesday which has some potential to bring passing mountain showers but little in the way of impacts or appreciable precipitation and NBM PoPs are around 15% or less. Temperatures will remain close to seasonal averages or slightly warmer. The greatest weather impact will likely be areas of dense morning fog impacting travel each morning commute.

Thursday-Sunday: Ensembles are in fairly good agreement of a deeper Pacific trough swinging toward the PacNW coastline during this time but evolution of this system inland comes in many variations. This leads to lower confidence regarding the details of the forecast for this period. 40% of the solutions indicate widespread precipitation while 60% are dry. There is also a lot of uncertainty with the progression of this through the region and whether this will deliver windy conditions or not. At this time, there is moderate to high confidence for another cool trough to settle toward the PacNW Coastline but moderate to high uncertainty when precipitation will return to the Inland NW, precise snow levels, and how this could impact winds. Stay tuned. /sb

Aviation

00Z TAFS: VFR conditions will most likely prevail outside of KLWS-KPUW. An MVFR to IFR could deck has formed in the past half hour at KLWS-KPUW. Models have a very poor handle on this, but would expect it to erode as winds turn easterly at KPUW and southerly at KLWS when downsloping dries out the boundary layer around 05-07Z. There is a small chance of sprinkles at KEAT from 00Z-04Z Saturday. There is a 10-20% chance of fog for KGEG- KMWH from 12Z-18Z. Models have performed poorly with the fog so far this fall so it would not surprise me to see some river fog form at KSFF as well. Some degree of mid to high clouds will help hamper radiative cooling to a degree but surface dewpoints running in the upper 30s and low temperature forecasts in the mid 30s suggest surface RHs will approach 100 percent. Confidence is very low but it will make the difference between VFR and LIFR conditions.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Low confidence for fog tonight for KSFF-KGEG-KMWH between 12Z-18Z.

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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 34 53 38 52 33 51 / 0 10 10 10 0 0 Coeur d'Alene 34 55 38 51 33 52 / 0 0 10 10 0 0 Pullman 32 53 36 44 32 49 / 0 20 40 30 0 0 Lewiston 38 55 43 50 37 53 / 0 20 40 60 0 0 Colville 31 54 31 55 27 50 / 0 0 10 0 0 0 Sandpoint 33 53 35 50 31 49 / 10 0 10 0 0 0 Kellogg 35 55 38 49 33 51 / 0 10 20 30 0 0 Moses Lake 30 54 35 55 29 53 / 0 0 10 0 0 0 Wenatchee 33 51 38 56 35 51 / 0 0 10 0 0 0 Omak 32 52 35 55 31 50 / 10 10 0 0 0 0

Watches, warnings and advisories

WA: None. ID: None.