Marine Weather and Tide Forecast for Manson, WA

SYNOPSIS
Isolated strong to severe storms this afternoon in southeast Washington and southern Idaho Panhandle. Cooler and wetter weather pattern sticks into early next week with several opportunities for showers and afternoon thunderstorms.

DISCUSSION

Today: A conditionally unstable airmass will favor the development of a few strong, possibly severe thunderstorms in southeast Washington and the central/southern Idaho Panhandle this afternoon.
Thunderstorms will be capable of large hail (up to quarters) and gusty winds (up to 50 mph). The main timing threat appears to be around 3-8 PM this afternoon.

A strong upper trough and surface low will approach the Oregon coast this afternoon leaving the inland northwest in a strongly sheared conditionally unstable airmass, particularly southeast washington and the central/Southern Idaho panhandle. Expecting several cells to develop early this afternoon in northeast Oregon thanks to forcing aided by height falls/upper level divergence and surface heating of the terrain. With surface based capes around 300-800 J/kg and 0-6 km shear values around 50-70kt, there could be a couple high based supercells if storms stay isolated enough and not grow upscale. The high resolution models actually show a tightly clustered area of cells possessing some mid-level updraft helicity (a measure of rotation in strong thunderstorms) around the L-C valley/Camas Prairie area to as far northeast as Lookout Pass this afternoon. This would be a higher end scenario where strong cells may need severe thunderstorm warnings.
Temperature/dewpoint spreads are very large (20+ degrees) so not looking at a tornado threat. Besides the wind and hail threat, another threat is flooding for the Cougar Creek and Gwen burn scars. 1 hour max rainfall rates will be around an inch but cell motions around 30-40 mph will limit the flood threat. If cells start to train, the flood threat would increase for those burn scars.

Tonight and tomorrow: Behind the stronger storms, a band of mostly stratiform rain will move through eastern Washington and north Idaho bringing much needed rains to the area this evening and tonight.
Rain amounts look fairly light around 0.05" near Ritzville to as high as 0.30" for Bonners Ferry. Lows tonight will be fairly mild in the 40s thanks to lots of clouds. By tomorrow morning, most of the area will be rain free expect near the Canadian border where light showers remain. As the upper low moves inland tomorrow, there is another threat for afternoon showers and thunderstorms, especially southeast Washington and the southern Panhandle. Shear looks weaker tomorrow, but with capes around 200-500 J/kg storms will be capable of producing a few lightning strikes, especially near the Camas Prairie. Rain amounts look fairly light around a quarter inch or less under showers tomorrow. db

Tuesday through Friday: The Inland Northwest will remain under the influence of the northern branch of a deep upper-level trough on Tuesday as it shifts southeast into the Great Basin, while subtle ridging builds into western Washington. Ensemble cluster analysis shows good agreement on these synoptic-scale features, but highlights some disagreement among global models regarding the exact placement and strength of the trough from through Thursday. For Tuesday, model agreement is good enough to support higher confidence in continued showers across much of eastern Washington and north Idaho through the afternoon with shower thunderstorm and coverage shrinking in size for Wednesday.

Whether this showery pattern persists into Thursday is less certain.
Around 60 percent of ensembles favor a slightly weaker trough, which would allow for continued mountain showers on Wednesday with a distinct dry period on Thursday as a ridge builds in. The remaining 40 percent suggest a stronger and more broad trough that would keep the ridge more offshore, allowing for another wave to clip the Inland Northwest from the northwest on Thursday bringing showers to northeast Washington and the Idaho Panhandle. Temperatures in both scenarios only differ by a few degrees, with the the weaker trough pattern resulting in slightly warmer conditions. Regardless of the outcome, continued onshore flow would support breezy afternoon winds through the Cascade gaps and into the western Columbia Basin.

For Friday through Sunday, ensemble guidance is in good agreement for a pattern of unsettled weather with several systems moving through the Inland Northwest. /vmt



AVIATION
00Z TAFs: VFR conditions will prevail in central Washington over the next 24 hours. There is a threat for thunderstorms that could impact KLWS-KPUW-KCOE between 0-3z. The best chances (20%) for thunderstorms are closer to KLWS. Thunderstorms could bring gusty southwest outflow winds up to 30 kt. Under the rain bands in the eastern third of WA and north Idaho around 0-12z, expecting a 20-50% chance of MVFR cigs (KGEG-KSFF-KCOE-KPUW).

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Low confidence in thunderstorms at GEG/SFF/COE/PUW.LWS.

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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 44 61 43 59 44 64 / 80 30 10 40 10 10 Coeur d'Alene 44 61 41 59 43 62 / 90 40 20 50 20 30 Pullman 42 56 39 56 41 59 / 90 50 20 50 20 20 Lewiston 49 64 46 64 47 67 / 90 70 20 40 10 20 Colville 40 61 38 62 40 65 / 70 80 50 60 30 30 Sandpoint 45 58 43 58 43 60 / 90 60 30 70 30 50 Kellogg 46 56 43 54 45 55 / 90 60 20 70 20 60 Moses Lake 42 69 44 67 43 72 / 30 20 10 20 0 0 Wenatchee 44 66 48 69 48 69 / 20 10 20 10 0 0 Omak 44 65 43 69 43 72 / 50 50 30 20 10 0

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