Clarkston, WA 99403 Weather

Key Messages

- Dry weather continues today with mild afternoon temperatures.

- Medium to high confidence for rain across far eastern Washington and north Idaho Thursday afternoon through Friday morning.

- Breezy to gusty west to northwest winds across central Washington and southeast Washington Thursday night through Friday afternoon.

Synopsis

Dry weather and mild temperatures are expected again today. Precipitation chances increase across far eastern Washington and north Idaho Thursday afternoon through early Friday morning. This comes with stronger west to northwest winds across central and southeast Washington through Friday afternoon.

Discussion

Wednesday: Another warm and dry day is on tap for the Inland NW as a dry southwest flow continues. Highs will reach the mid 60s to low 70s which is around 10 degrees above normal.

Thursday and Friday Night: Changes arrive as a low off the California coast ejects northeast into California, Nevada and southern Idaho. While the system is passing well to our south, some of this moisture gets picked up by an incoming upper trough from the west, with precipitable water values increasing to near 150 percent of normal across the eastern third of Washington and as much as 200 percent of normal in North Idaho. This will translate to a 60-80 percent chance of rain over the Central Panhandle Mountains down through the LC Valley, Camas Prairie, Blue Mountains, and Palouse and a 30-50 percent chance of rain from Ritzville up through Spokane, Newport, and the North ID Panhandle. Yet with the incoming trough from the west this moisture increase is short lived which will likely keep precipitation amounts to less than a tenth of an inch across Eastern Washington with a tenth to quarter inch over the Central Panhandle Mountains and Camas Prairie. Drier air associated with this trough will result in much drier air coming into Central WA on Friday as precipitable water values plummet to 25-50 percent of normal. This combined with breezy north- northwest winds (locally windy down the Okanogan Valley and Waterville Plateau) behind a cold front will promote elevated fire weather conditions and the potential for patchy blowing dust. Winds ease Friday Night, and with the very dry air over the region radiational cooling will be strong, with freezing temperatures for most (except locally around Wenatchee), with the colder pockets such as Republic and Deer Park falling into the low 20s.

Saturday through Tuesday: Ensembles to continue to struggle with a low that strengthens off the southern BC coast on Saturday and then what happens after that. 40 percent of the clusters move the low near or over the region for cooler and showery weather while the other 60 percent maintain ridging over the region. Given the uncertainty not too many changes to this part of the forecast which currently provides a middle ground of the model solutions with near seasonal temperatures with highs mainly in the 50s and a 20-30 percent chance of showers. But with a 10-15 degree range between the NBM 10th and 90th percentiles there is low confidence in the forecast details. If the cooler and showery scenario pans out snow could fall as low as 3500 to 5000 feet in the Cascades and northern mountains but again confidence is low. JW

Aviation

18Z TAFS: Expect VFR conditions through the 24 hr TAF period with any ceilings above 12k ft AGL. Light wind are expected today. Increasing winds and chances for showers to develop after 18Z Thursday.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in VFR conditions. KD

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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