Marine Weather and Tide Forecast for Skykomish, WA

SYNOPSIS
Winds will be breezy Monday and Tuesday afternoon across parts of central Washington. A weather system moving through Monday Night into Tuesday morning will bring rain to the region, except Cascade valleys that will be shadowed out. Warmer and drier weather returns Wednesday and Thursday. Rain returns toward next weekend.

DISCUSSION
Today through Tuesday Night: The ridge will nose into the region today and flatten as the next weather system moves into BC.
Another warm day with temps 5 to 8 degrees above average-in the upper 60s to low 70s. Winds will increase in the afternoon across portions of central WA, mainly the Wenatchee valley onto the Waterville Plateau and parts of the Columbia Basin. Winds will not be as strong as yesterday, but there is a 50-70% chance of gusts to 25 mph for the areas mentioned above. Gusts above 30 mph are possible, but mainly in the mountains and a 30-40% chance on the Waterville Plateau. Clouds will begin to increase in the afternoon as the weather feature nears. Through the evening there is a 20-30% chance of light rain at the Cascade crest and along the WA/Canadian border.

Overnight precipitation will spread west to east through the region. Precipitation totals will generally be light. The Cascade valleys into the Okanogan Valley and Waterville Plateau will be lucky to see a hundredth. The Columbia Basin will see less than a tenth of an inch. While most areas will see the rain overnight and Tuesday morning, extreme eastern WA and the ID Panhandle will continue the threat of rain in the afternoon. Storm totals will generally be a tenth to a quarter of an inch in the valleys with a quarter to half an inch in the mountains. There could be some partial clearing in the afternoon across NE WA and the N ID Panhandle. Cannot rule out some afternoon showers with graupel or perhaps a lightning strike. Another breezy afternoon and evening across the Cascade gaps, onto the Waterville Plateau and parts of the Columbia Basin and Okanogan Valley. Probabilities of gusts to 25 mph are 60-80%, and gusts above 30 mph are 40-50% in the mountains, Waterville Plateau and the southern Okanogan Valley.

Clouds will continue to dissipate into the evening and overnight hours Tuesday. Have lowered temperatures several degrees, especially across the Cascade valleys and portions of the northern Columbia Basin. Have also added some patchy fog across valleys of northeast WA and the ID Panhandle. /Nisbet

Wednesday to Friday: High pressure builds into the area through the end of the week, amplifying ahead of a deepening offshore trough with dry and warmer weather. First, however, Wednesday morning will see an ending shower threat near southeast Shoshone county, along with patchy fog across the sheltered northeast WA and ID Panhandle valleys. Chilly temperatures start the day, with low in the 30s to mid-40s. Patchy frost is expected around the sheltered northern valleys, in the higher Cascades valleys and even the upper Columbia Basin to West Plains early.
Otherwise look for mostly clear to partly cloudy skies most of the period. Some cloud start to increase later Friday with a chance of showers coming to the Cascade crest in the afternoon.
Winds do increase Friday, turning from southeast to east to southwesterly by afternoon. Gusts of 15-30 mph are possible by afternoon, strongest near the lee of the Cascades to Upper Columbia Basin.

Highs will be in the upper 60s to mid-70s Wednesday, 70s to low 80s Thursday and upper 70s to mid-80s on Friday. A few spots in the L-C Valley and deeper basin could be in the upper 80s Friday. Overnight lows will be largely be in the 40s through Friday night, with some lows 50s in lee of the Cascades, deeper basin and L-C Valley.

* Warm temperatures confidence: confidence in the warming trend is high, but confidence in the precise numbers is lower.
There is some uncertainty as to how warm it will get; ensembles and the NBM diverge on this matter.The NBM is mildest, showing a 60-90% chance of 80 degrees over the Columbia Basin and even up to the Spokane area and some of the northern valleys, with about 90% chance in the L-C Valley. On the other hand the ensembles have about 40-60% chance of reaching 80 only over the deeper Columbia Basin and only 5-10% chance elsewhere. Given the amplitude of the ridge and EFI showing 70-90% chance of anomalously warm temperatures, I kept with the milder NBM. The Heat Risk reaches the minor category Thursday and especially Friday, which means those with sensitive to heat could be impacted.

Friday night to Sunday: The pattern turns cooler, wetter and breezy. A long-wave trough sits off the coast at the start of the period. Models show this feature to be highly meridional (south to north flow). Features of this type can be challenging for models to accurately depict, especially when it comes to how quickly it moves inland and how it evolves as it does. That basically is to say the precise details about the timing and coverage of precipitation heading into this period has lower confidence.

Precipitation chances increase to likely across the Cascades and near the southeastern CWA Friday night. They also increase to medium to high chances elsewhere, which is about 40-50%.
Chances continue to increase through Saturday. Yet here is where models diverge. Some increase them quickly in the morning, then start to shift the higher potential to the mountains in the afternoon. If this was a quicker and cleaner system passage that may be okay, but models are tending to stretch and split this system and are not that quick to move it through and even as it starts to move out some moisture may wrap around it. (PWATs increase to around 140-180% of normal).I diverged from the raw NBM and kept PoPs high Saturday afternoon, except in the lee of the Cascades and deeper basin where I start to show them decreasing. Where PoPs remain high I have a 50-80% probability, with the highest of that range near the Cascade crest and the NE WA and ID Panhandle mountains and southeast WA.

The forecasted PoPs do start to decline Saturday night into Sunday, retreating to the mountains, but not ending entirely over the east third of WA and lower ID. If the system trends slower or moisture wraps back PoPs would need to be raised to hold onto a higher precipitation potential Saturday night into Sunday, but it looks like QPF amounts decrease.

I do have some t-storms chances over the northern mountains and central Panhandle mountains to Camas Prairie Saturday afternoon/early evening, but confidence is low. Most of the best instability is shifting east of the area by then.

* Precipitation amounts: Overall between Friday night and Saturday night the forecast has about 0.10 to 0.30” of precipitation, locally higher over the southeast CWA and north- central WA. The best chance of wetting rain will be on Saturday, with ensembles and the NBM showing a 50-70% chance of >=0.10” over all but the lee of the Cascades and deeper basin where the potential there is about 20-40%. The EFI table shows a 50-70% chance for anomalously higher QPF amounts near the Blues and Camas Prairie and over north- central WA Saturday. I did blend the raw WPC QPF with some the models showing higher QPF amounts in those areas.

* High mountain snow: This will be mostly in the form of rain, but models do have some high mountain snow around the Cascades. This is largely above pass level, except perhaps Washington Pass which could see a half inch. I also point this out for any recreationists who might head into the higher back country areas, especially above about 5000 feet.
Snow amounts are not expected to amount to much, but some of the highest peaks could see a couple inches.

* Winds: additionally, the incoming system will bring breezy conditions. Wind remain gusty Friday night and continue to increase and peak into Saturday afternoon but still remain gusty through Sunday. So overall this will be breezy/gusty period. Winds gust near 15-30 mph, peaking between 20-35 mph Saturday afternoon, The sheltered mountain valleys will, however see lighter winds.

Temperatures will reach the upper 50s and 60s through the weekend, with some areas near 70 in the deeper basin. Overnight lows will be in the mid-30s to mid-40s. The coldest of those readings are in So some patchy frost is not out of the question. /Solveig



AVIATION
12Z TAFS: Primarily VFR conditions expected, but a system will be moving toward the area and starting in late tonight into Tuesday AM. This morning some localized fog/low clouds will be found in some sheltered mountain valleys over ID and some lower clouds are noted east of Moses Lake this morning, but these are expected to remain away from TAF sites. Middle to high clouds today, with gusty afternoon winds. Gusts near 15-25kt possible.
Late tonight into early Tuesday, clouds thicken and start to lower with the system. A chance for rain showers develops between 06-12Z. Chances will be found near EAT/MWH starting near 05-08Z and toward GEG/SFF/COE toward 08-10Z. The better risk develops after 12Z Tuesday.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in VFR conditions. Low confidence in MVFR/IFR fog/low clouds over MWH and COE.

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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 68 47 65 40 68 42 / 0 40 80 0 0 0 0 Coeur d'Alene 66 45 61 39 66 40 / 0 40 90 30 0 0 0 Pullman 63 44 58 40 63 40 / 0 20 100 10 0 0 0 Lewiston 72 51 66 45 70 44 / 0 20 90 10 0 0 0 Colville 70 43 66 35 71 38 / 10 60 50 10 0 0 0 Sandpoint 65 46 58 39 65 40 / 10 40 80 30 0 0 0 Kellogg 65 46 54 42 62 43 / 0 40 100 40 10 0 0 Moses Lake 74 49 72 39 73 43 / 0 30 40 0 0 0 0 Wenatchee 71 51 68 44 73 48 / 10 30 20 0 0 0 0 Omak 73 46 71 40 74 44 / 10 20 10 0 0 0 0

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