Area Forecast Discussion

KEY MESSAGES

- Friday: Scattered showers and isolated thunderstorms over the Northeast Mountains into North Idaho through early evening. - Friday: Dry and breezy Okanogan Valley with elevated fire weather conditions through early evening

- Warming well above normal over the weekend into early next week. Minor HeatRisk into the weekend and increasing threat for moderate HeatRisk Monday into Tuesday.

- Tuesday: Very warm and dry conditions and gusty westerly winds with a dry cold front passage will bring the potential for critical fire weather conditions.

SYNOPSIS

Temperatures will warm above normal through the weekend into next week. The warm up will be muted on Friday with a low pressure system clipping the northeast portion of the region. The weather system will bring breezy northerly winds down the Okanogan Valley along with scattered showers and isolated thunderstorms primarily over the mountains of northeast Washington into North Idaho. Then a strong ridge of high pressure brings warmer temperatures for Sunday and Monday. Fire weather will be a concern Tuesday with warm, dry conditions and gusty westerly winds with a cold front passage.

DISCUSSION

Tonight: A mid level wave dropping into NE Washington and the ID Panhandle will continue to promote scattered showers and isolated thunderstorms through early this evening. A dry low level air mass initially with temperature-dewpoint spreads of 25-35F will contribute to enhanced downdrafts from the convection with brief gusts of 30-40 MPH. Storms will be also capable of producing pea sized hail and brief downpours. A combination of the mid level wave exiting North Idaho this evening and loss of daytime heating will lead to a quick end to the convection after sunset with clearing skies overnight. This wave has also ushered in breezy north winds down the Okanogan Valley, which combined with warm temperatures and low relative humidity will lead to continued elevated fire weather conditions into the early evening.

Saturday: The flow aloft turns northerly as an upper ridge builds off the coast. Another mid level wave is progged by the models to clip north Idaho, but is not as strong as the wave that went through today. Still, there is just enough boundary layer moisture and afternoon instability for a 20 percent chance of afternoon showers over the mountains of the ID Panhandle.

Sunday and Monday: An upper ridge moves over the region providing warmer temperatures and dry conditions. High temperatures increase into the 80s on Sunday, and then mid 80s to mid 90s on Monday.

Tuesday: A dry cold front passage will lead to at least elevated, if not critical, fire weather conditions in dry grass along the East Slopes of the Cascades into the Columbia Basin. The NBM has trended towards more cooling in Central Washington (5-10 degrees cooler compared to Monday) while Eastern Washington and North Idaho experience similar temperatures. Temperatures in the 80s to low 90s combined with low relative humidity are forecast. The ECMWF ensemble mean has been pretty consistent with wind gusts of 30-40 MPH, locally up to 45 MPH along the East Slopes into the Columbia Basin, West Plains, and Palouse.

Wednesday through Friday: Drier air behind the front from Tuesday lingers over the region supporting dry conditions for Wednesday and Thursday along with high temperatures cooling into the mid 70s to mid 80s. On Friday an upper trough nosing closer to the region will bring a 20 percent chance of showers to the northern mountains otherwise dry conditions are expected to prevail. JW

AVIATION

00Z TAFs: Scattered showers and isolated thunderstorms will continue over Northeast Washington into the Idaho Panhandle through 02-03z this evening. Gusty outflow winds and short bursts of heavy rain will be the primary hazards with these showers/tstms before they begin to dissipate. Outflow wind gusts of 25-35 kts are near showers and thunderstorms including KGEG/KSFF/KCOE.

Following the shower activity, winds will decrease and turn more north-northeast with the exception of KEAT which will remain northwest. VFR conditions are expected to prevail during the TAF period except for brief restrictions in showers or thunderstorms early this evening.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is a 30 percent chance of showers, and a 20 percent chance of thunderstorms impacting KGEG/KSFF/KCOE through 01-02z. JW

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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 47 77 49 83 54 87 / 20 0 0 0 0 0 Coeur d'Alene 47 75 49 81 54 85 / 30 0 0 0 0 0 Pullman 44 75 47 79 49 85 / 10 0 0 0 0 0 Lewiston 51 83 52 86 56 91 / 0 0 0 0 0 0 Colville 42 79 45 85 52 88 / 20 0 0 0 0 0 Sandpoint 45 74 48 81 52 84 / 40 0 0 0 0 0 Kellogg 45 74 47 81 52 84 / 40 0 0 0 0 0 Moses Lake 52 84 54 89 57 95 / 0 0 0 0 0 0 Wenatchee 57 84 60 89 64 94 / 0 0 0 0 0 0 Omak 51 84 55 90 60 93 / 10 0 0 0 0 0

OTX WATCHES / WARNINGS / ADVISORIES

WA...None. ID...None.