Area Forecast Discussion

KEY MESSAGES

- Breezy winds will result in elevated fire danger Saturday, albeit cool afternoon highs will dampen the threat.

- Showers and isolated storms possible Saturday (40-70% Cascades/Northern Mountains, 10-20% Basin)

- Frost possible across the Northern Valley's Saturday night and early Sunday.

DISCUSSION

An upper low is currently sitting just off the NW Coast and will make its way across the region this weekend. This will result in showers and thunderstorms mainly to the Cascades and Northern Mountains and even light snow to the highest mountain areas Saturday. Additionally, moist 700mb southwesterly flow may combine with marginal instability (150 J/kg) and steep mid level lapse rates to produce a few showers or an isolated thunderstorm or two across the basin into E WA and N ID (10- 20% chance).

Elevated fire concerns will continue Saturday primarily due to wind speeds remaining elevated in the 10-20 mph range including wind gusts of 25- 30 mph. However, cooler afternoon high temperatures in the 50-60s will help dampen the fire threat.

The next period of concern will be Saturday night into early Sunday where low temperatures will fall to the low and mid 30s (65-90+% probability of occurrence) across the Northern Valley's. A frost advisory has been issued for these areas. Take action to cover sensitive plants/crops. Upper troughing will continue to push east Sunday which will leave the door open for a few lingering showers (30% chance) and an isolated storm mainly across far NE WA and the N ID Panhandle.

As we head into next week, yet another system will be on the doorstep ready to move across the forecast area and provide intermittent chances for shower and storm activity. Best chances (30-80%) of showers are expected in the Tuesday/Wednesday timeframe. At this time, there is fairly good agreement across ensemble data that the region remains under troughing Tuesday and Wednesday, however, uncertainty increases in the later half of the week. Solutions diverge to either 1-remain under troughing or 2-begin to be influenced by an offshore ridge as soon as Thursday with the potential for riding to remain overhead though next weekend.

AVIATION

18Z TAFs: Another breezy day is on tap across the Inland Northwest with prevailing VFR conditions expected. Wind gusts up to 25-30 kts expected into the afternoon through the Cascade gaps into KEAT, across the exposed areas of the Columbia Basin (KEPH/KMWH), into the Spokane/Coeur d'Alene areas (KGEG/KSFF/KCOE), and Palouse to Lewiston/Clarkston Valley (KPUW/KLWS). Conditionally unstable today with diurnal heating resulting in convective showers through the day. Showers will be more widely scattered across the northern mountains with isolated thunderstorms (15-25 percent chance), and isolated showers with a only a 10 percent chance for thunderstorms in the Columbia Basin. Convection is expected to wane between 03-06Z this evening.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in prevailing VFR conditions at all TAF sites through the period. Low confidence in shower or thunderstorm developing over a given TAF site. /SVH

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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 63 40 65 43 68 45 / 20 20 0 0 0 50 Coeur d'Alene 62 41 63 42 67 47 / 20 20 10 0 0 50 Pullman 60 39 62 41 66 44 / 10 10 0 0 0 60 Lewiston 68 47 69 47 73 50 / 20 0 10 0 0 60 Colville 65 32 67 36 68 40 / 40 40 10 0 10 50 Sandpoint 61 39 60 41 65 45 / 20 30 30 0 0 50 Kellogg 60 41 59 40 68 47 / 20 20 20 0 0 50 Moses Lake 68 38 72 45 71 44 / 20 10 0 0 0 30 Wenatchee 66 46 71 51 69 51 / 10 10 0 0 30 50 Omak 66 38 72 44 70 46 / 60 10 0 0 10 40

OTX WATCHES / WARNINGS / ADVISORIES

WA...Frost Advisory from 10 PM this evening to 11 AM PDT Sunday for Northeast Mountains-Okanogan Highlands-Okanogan Valley- Western Okanogan County. ID...Frost Advisory from 10 PM this evening to 11 AM PDT Sunday for Northern Panhandle.