DISCUSSION

Tonight: Rain wrapping around low pressure in Montana will gradually exit the Idaho Panhandle tonight. By midnight, the surface low associated with these rain bands will lift into Saskatchewan and the NAM, GFS, and ECMWF have the majority of the rain out of north Idaho. Our westerly pressure gradient driving gusty west winds will also diminish through the night. Sustained 15 to 25 mph over the Palouse, foothills of the Blue Mountains, and Waterville Plateau will diminish to 10 mph or less overnight.
Rain soaked valleys in north Idaho will likely develop patchy fog overnight.

Friday: Morning clouds and fog over north Idaho will lift into a cumulus deck. Other than a 20 percent chance of showers over the ridges along the Idaho/Montana border, the Inland Northwest will experience a dry day. Afternoon highs will be in the 70s with southerly winds in the 5 to 15 mph range. Clouds will increase late in the day across central Washington ahead of our next system. By the evening, light rain will spread into the Cascades and a 30 to 50 percent chance of rain will reach the Okanogan Highlands, and mountainous terrain of northeast Washington by the pre-dawn hours of Saturday.

Saturday and Sunday: The weekend will feel like early fall with highs in the upper 60s to mid 70s. On Saturday, a broad upper level trough off the coast will send clouds inland along with the chance for showers. Mid-level westerly flow will limit chances for measurable rain to less than 10 percent or less for our typically dry areas impacted by the Cascade rain shadow like Wenatchee, Moses Lake, Grand Coulee and Omak. The mountainous terrain along the Canadian border will have the best opportunity for showers Saturday with a 50 to 70 percent chance of measurable rain for Republic, Metaline, Bonners Ferry, and Sandpoint. The trough along the coast will sharpen on Sunday as a low digs toward California. The morning runs of the operational GFS, NAM, and ECMWF keep the majority of the Inland Northwest dry Sunday and Sunday evening, but there are enough ensemble members generating light rain showers to have a 20 to 30 percent chance of showers across our mountainous terrain of north Idaho and northeast Washington.

Monday through Thursday: The ensembles are in good agreement that the trough over the Western U.S. will bottom out on Monday with the upper low reaching central Nevada by the evening. With the low so far south, Monday should be a mainly dry day for the Inland Northwest with the exception of a 20 to 30 percent chance of showers for the Blue Mountains, Palouse, Camas Prairie, and the central Idaho Panhandle. It is possible that these probabilities could trend down if the ensembles lock down on keeping the low well to our south.

The pattern becomes somewhat complex Tuesday, Wednesday, and Thursday as another shortwave dives into the West Coast trough and the low that bottoms out in Nevada Monday is kicked into southern Idaho Tuesday and eventually central Canada by Wednesday. Similar to our ongoing wrap around rain, the Idaho Panhandle will have the best shot of significant rainfall in this scenario. The National Blend of Models (NBM) generates a 50 to 70 percent chance of rain for the Panhandle on Tuesday with less than a 20 percent chance for central Washington. Tuesday and Wednesday look to be the coolest days of next week with highs in the 60s and low 70s under the cool trough axis. /GKoch

AVIATION
06Z TAFS: Exiting system will continue to push moisture North to South over the Idaho Panhandle. Any shower is expected to miss TAF sites but impact Bonners Ferry and Sandpoint areas. Drier air behind the system will decrease cloud cover and keep concern of low ceilings limited to areas of North Idaho. VFR conditions are expected for the TAF sites.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is 30% probability of MVFR ceiling over GEG-SFF-COE Friday 12-15Z. There is moderate to high confidence for VFR conditions.



PRELIMINARY POINT TEMPS/POPS
Spokane 50 74 52 72 48 71 / 10 0 20 20 10 10 Coeur d'Alene 48 71 51 69 47 70 / 20 0 10 40 20 20 Pullman 46 70 47 69 45 67 / 10 0 0 10 10 20 Lewiston 54 77 56 77 55 73 / 10 0 0 10 10 20 Colville 44 75 41 71 38 70 / 10 0 40 50 30 20 Sandpoint 47 69 47 67 45 67 / 40 10 20 60 30 30 Kellogg 48 67 52 68 50 67 / 40 20 10 30 20 30 Moses Lake 49 76 52 76 47 72 / 0 0 10 10 0 0 Wenatchee 52 76 57 74 52 71 / 0 0 20 10 10 0 Omak 49 80 52 74 49 74 / 0 0 30 10 10 10

OTX WATCHES/WARNINGS/ADVISORIES
ID...None.
WA...None.