Area Forecast Discussion

KEY MESSAGES

- Gusty northwest winds continue through Thursday evening.

- Weather trends drier with cold overnight lows Friday through the weekend.

SYNOPSIS

Gusty northwest winds continue through Thursday. Dry conditions and partly cloudy skies will prevail Friday through the weekend. Overnight lows will trend colder with temperatures dropping below freezing Thursday night through Saturday night for much of the region.

DISCUSSION

Thursday through Friday: The low pressure system that brought widespread rain and gusty winds to the Inland Northwest is slowly moving eastward. This low pressure system will begin interacting with another low pressure system in central Canada. This second low will dip down into the far northeastern part of Washington. Orographic lift and dry air moving in from the northwest will keep precipitation confined to eastern Washington and the central Idaho Panhandle. Precipitation amounts will be light, with high end totals near 0.25 inches. Additionally, a vorticity band associated with the low pressure system will pass through these areas with precipitation chances. Combined with CAPE values of 100-200 J/kg, there is a 10- 20% chance of thunderstorms Thursday afternoon and evening. Main impacts will be gusty outflow winds and small hail.

With a frontal passage moving in through the day, winds will remain gusty and out of the northwest. Areas that will see the highest wind gusts include the Western Okanogan County and Okanogan Valley and highlands areas alongside the Northeast Blue Mountains. For these areas, wind gusts will peak at around 35-40 mph. Elsewhere in the forecast area, expect wind gusts 15-20 mph. These winds remain elevated through Friday evening.

The cold frontal passage will result in chilly overnight low temperatures to the forecast area. As the growing season has started for low elevation areas, these temperatures will be monitored for frost impacts.

Saturday through Wednesday: The two lows mentioned above will combine and strengthen while moving into the north central U.S. The placement of this low will keep any light precipitation chances through the week confined to far eastern Washington and the Idaho Panhandle. The boundary layer for the rest of the forecast area remains dry. As the low moves farther away and a trough off the Canadian coast brings higher heights to the state of Washington, temperatures will gradually increase through the week. By mid-week, maximum temperatures will be in the mid to high 60s and low temperatures will be above 40 degrees in most areas. Clusters are in decent agreement with this setup, as are other long range models, especially once the low has migrated further enough east. Bottom line: expect a warming and drying trend for much of the forecast area through mid-week. /AS

AVIATION

12Z TAFS: Drier northwesterly flow aloft into the Inland Northwest has resulted in primarily VFR conditions across the Inland Northwest. The exception is at KCOE where IFR stratus is struggling to clear. Models continue to suggest it to gradually lift through the early morning, but confidence in the exact timing is low.

Showers will develop late this morning across far eastern Washington and north Idaho. With the best instability along the Idaho/Montana border, there ie a very small chance these will develop into thunderstorms over a TAF site. Breezy west to northwest winds will continue through the afternoon with gusts 20-30 knots.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is high confidence for widespread VFR conditions across the Inland Northwest later this morning through the period. However, there is low confidence in the exact timing of ceiling improving at KCOE and if showers will move over any TAF sites.

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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 57 34 53 32 56 34 / 30 10 0 0 0 0 Coeur d'Alene 53 32 53 31 54 32 / 50 20 10 0 0 0 Pullman 53 32 50 29 53 31 / 50 30 10 0 0 0 Lewiston 58 36 55 33 58 35 / 50 30 10 0 0 0 Colville 59 31 57 29 58 31 / 20 10 10 0 0 0 Sandpoint 49 32 50 31 52 31 / 80 40 10 0 10 10 Kellogg 49 31 49 29 51 30 / 90 50 20 0 10 0 Moses Lake 64 38 60 34 61 36 / 10 10 0 0 0 0 Wenatchee 64 41 59 39 61 41 / 10 10 0 0 0 0 Omak 64 36 60 34 61 37 / 0 0 0 0 0 0

OTX WATCHES / WARNINGS / ADVISORIES

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