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PZZ135 Puget Sound And Hood Canal- 232 Pm Pst Sat Dec 2 2023
.small craft advisory in effect until 10 pm pst this evening...
.small craft advisory in effect from Sunday morning through Sunday afternoon...
Tonight..S wind 10 to 20 kt. Wind waves 1 to 3 ft. A chance of rain in the evening then rain after midnight.
Sun..SE wind 10 to 20 kt becoming S 15 to 25 kt in the afternoon. Wind waves 2 to 4 ft. Rain.
Sun night..S wind 10 to 20 kt becoming 5 to 15 kt after midnight. Wind waves 1 to 3 ft. Rain.
Mon..SE wind 5 to 15 kt becoming S 10 to 20 kt in the afternoon. Wind waves 1 to 3 ft.
Mon night..S wind 15 to 25 kt becoming 20 to 25 kt after midnight. Wind waves 2 to 4 ft.
Tue..S wind 15 to 25 kt easing to 10 to 20 kt in the afternoon. Wind waves 2 to 4 ft subsiding to 2 ft or less in the afternoon.
Tue night..S wind 5 to 15 kt in the evening becoming light. Wind waves 1 ft or less.
Wed..SW wind to 10 kt. Wind waves 1 ft or less.
Thu..S wind to 10 kt. Wind waves 1 ft or less.

PZZ100 232 Pm Pst Sat Dec 2 2023
Synopsis for the northern and central washington coastal and inland waters..A series of frontal systems will make their way across the waters through Tuesday. Windy conditions are expected across all waters at times into next week. Seas will remain above 10 feet into next week and could approach 20 feet Tuesday.

FXUS66 KPDT 030428 AFDPDT

Area Forecast Discussion National Weather Service Pendleton OR 828 PM PST Sat Dec 2 2023

SHORT TERM UPDATE
It will be an active weather week with various forecast challenges. Currently, the forecast area is under a strong northwest flow aloft and between two frontal systems.
There is a brief break in precipitation for most of the area, although a Puget Sound Convergence Zone (PSCZ) has set up and is bringing continuous precipitation north of I-90 in Kittitas County. Doppler Radars on the west side of WA/OR are showing increasing returns associated with an approaching warm front.
Precipitation will soon redevelop over the OR Cascades and central OR then will spread north to the rest of the CWA overnight and early Sunday morning.

Winter highlights remain in effect for the east slopes of the WA Cascades and the eastern mountains. Because the break in precipitation is temporary, the highlights will remain as is. The warm front will cause snow levels to rise rapidly tomorrow. Based on current observations, snow levels are around 4000 feet in central OR, 3500 feet over the Blues and Wallowas, and 2000 feet over south central WA. The warm front will push snow levels as high as 6500-7500 feet on Sunday. Any cold air remaining in the valleys along the east slopes of the WA Cascades will result in light freezing rain (-FZRA). The NBM probability of -FZRA is around 35% for the WA Cascade east slopes and 20% in isolated spots east of the Blue Mountains. The upcoming shift may decide to take the Winter Storm Warnings for the WA Cascades east slopes that are set to expire Sunday morning and follow it with an advisory for the mixed precipitation.

Tomorrow's warm front will have an atmospheric river associated with it, although there are varying degrees on the IVT of the deterministic models. On average the inland IVT is around 500 kg/m/s--not extreme but definitely worth mentioning. The ECMWF Extreme Forecast Index has a large area of 0.8-0.9 on the QPF over central and northeast Oregon. Looking at the 24-hour precipitation amounts of the HRRR, only 2 of the 10 members show less than 1 inch of QPF for the northern Blue Mountains from midnight to midnight on Sunday. QPF for the Cascade crest, mainly south of Mt.
Adams, will show 2-3 inches on Sunday and Sunday night. Previous shift issued a Hydrologic Outlook that discusses the hydrologic concerns from Sunday through the mid week.

Today was a windy day with numerous gusts of 40-55 mph. Even though surface winds have decoupled from winds aloft, tomorrow's front will cause gusty winds aloft to resurface. Winds will not be as strong tomorrow, but there will be a few areas pushing the 45 mph gust, particularly over the southern Blue Mtn Foothills as well as central and north central OR. Mountain waves will set up along the Cascades. A lee side trough just east of the OR Cascades raises concerns on whether any mountain waves will propagate to the surface. Cross-sections using the 4-km ARW keep the strong winds along the ridgetops, therefore any confidence for damaging downslope winds associated with mountain waves is low (around 20%). Wister/85

PREV DISCUSSION
/issued 256 PM PST Sat Dec 2 2023/

SHORT TERM
Tonight through Monday
The short term forecast remains messy, as although we have started to see a decrease in some highlight worthy weather with wind advisories and one winter storm warning ending, many winter products continue through Sunday alongside a risk of freezing rain now possible in some locations thanks to a warm nose above the surface trapping colder valley air, along with another round of breezy winds tomorrow, followed by the beginning of hydrological concerns on Monday as snow levels rise and a weak atmospheric river moves into the region.

With the cold front now mostly across or directly over our region, the strongest activity in terms of winds has occurred while heavier precipitation for the Oregon Cascades has moved further down into Southern Oregon, helping to end both the winter storm warning here as well as the high wind warning/wind advisories that were ongoing. This boundary is expected to lift back as a warm front during the nighttime into morning hours tomorrow, bringing our snow levels up as it progresses through. Although we get further chances of precipitation, much of this will fall as rain for Central and North-Central Oregon, with the Cascades and Blue Mountains/Ochoco-John Day Highlands expected to see further snow amounts that will continue to fuel advisories or warnings through tomorrow. Of note though is the valleys in the region, particularly across the Washington Cascades, where colder air may become trapped thanks to the warm nose overspreading across. If this does occur, the risk for freezing rain does increase, though current forecast amounts generally remain around a glaze to under a tenth of an inch. This will require further analysis during the evening and nighttime model runs to see how much cold air remains in the region. Have elected to not extend the winter storm warning at the lower slopes of the Washington Cascades as frozen precipitation amounts are not expected to reach warning criteria, though a quick advisory after the warning ends may be needed.

With the lifting of the boundary and the pressure gradients remaining strong, breezy winds expected again tomorrow from a more southerly to southwesterly direction, but keeping most of the region outside of wind advisory levels. One exception might be the lower Columbia Basin/Foothills of the Blues in Oregon, another trouble spot to monitor through tonight. Snow levels rise above 5-7k feet by late tomorrow morning, bringing the bulk of the snowfall to an end with rain then becoming more prominent as moisture continues to stream in under a southwesterly flow. This leads into Monday, with models indicating a weak atmospheric river beginning. This leads into concerns for our rivers and streams as rain then falls onto the already fallen snow, alongside any hydrophobic soils nearby as well. Heaviest QPF totals on Monday expected in the Washington Cascades and foothills of, with 0.5-1.5 inches possible, heavier along the crests and peaks. The Blue Mountains also expected to see around 0.5-0.75 inch. Current river forecasts place the area rivers possibly entering bankfull stage into Tuesday, but will have to monitor closely as the overall snowpack becomes more defined once snowfall actually ends into Sunday. This warmth translates to highs and lows across the region as well, with high temperatures on Monday in the upper 40's to 50's for many of our population centers, with lows in the 30's to upper 40's.

LONG TERM
Tuesday through Saturday
The extended forecast start out wet, with the area feeling the effects of an ongoing atmospheric river, Tuesday into Wednesday before rain lessens later Wednesday into Thursday.

QPF amounts through Wednesday look to be 2 to 2.5 inches in the Blue Mountains and over 3 inches in the Cascades. These amounts have come down this model run. QPF will be generally 1 inch or less in most other locations and 1/2 inch or less in the Basin.

Temperatures will be quite warm Tuesday, with highs in the 50s to approach 60 degrees and lows Tuesday morning in the 40s. These highs are 15 to 20 degrees above normal in many locations. Wednesday will be a bit cooler, ranging from the mid to upper 40s to around 50 degrees with overnight lows in the 30s.

The ECMWF EFI is quite astounding for early December! It keys in on 0.7 to 0.8 probabilities for high temperatures centered on the Columbia Basin, with an embedded area of 0.8 to 0.9. Even more impressive is the EFI for low temperatures almost the whole region is indicated in 0.8 to 0.9, with the Basin and nearby locations in 0.9 to 0.95 and portions of the Columbia Basin in 0.95 to 0.99.
Tuesday morning looks to be very warm. Wednesday is a bit cooler with 0.7 to 0.8 over much of eastern Oregon.

With the warm temperatures, snow levels will be on the rise, peaking at over 9000 feet on Tuesday, before falling again through Wednesday and Thursday. As a result all of the precipitation falling Tuesday into Wednesday, will be rain, which will fall into the newly fallen snow. from earlier in the week. Therefore we expect significant rises on most rivers and streams, several of which are forecast to reach or exceed action stage, but no mainstem river flooding is expected at this time. Highest QPF in the EFI in the time is focused in the Washington Cascades, where 0.9 to 0.95 is indicated.
There could also be locally breezy winds on Tuesday, especially in the Columbia Basin and Grande Ronde Valley.

By Thursday morning, snow levels will be back to 3000-3500 feet in the Washington Cascades and 4000-4500 feet elsewhere. By Friday morning, snow levels should return to 2000 feet or below in the Washington Cascades sn 2500-3000 feet elsewhere. This will also help slow down any rises.

Beyond that, there will be a short break, then a trough will move onshore Thursday night into Friday, bringing another shot precipitation, this time mainly lower elevation rain and mountain snow.

By the end of the week, there is considerable uncertainty in the forecast. After the trough moves out, the ECMWF and NBM bring a ridge over the Pacific Northwest while the GFS brings in more systems and more precipitation. The ensemble clusters don't shed a ton of light, and ultimately the upstream pattern could be an artifact of a low that drops into the southern plains and how deep it is and its speed.

High temperatures Thursday will still be in the 50s. Highs on Friday will be in the the low to mid 40s and in the upper 30s to around 40 degrees on Saturday. Overnight lows will be in the 20s and 30s THursday night and 20s Friday night.

AVIATION
00Z TAFS
TAFS are generally VFR this afternoon, though an isolated MVFR is still possible through the late afternoon and evening. Then, conditions will deteriorate overnight to MVFR and IFR in some locations as the next system brings rain to the area on Sunday.

Winds will likely remain elevated with gusts in the 20 to 30 kt range through for at least the next few hours and possible into the overnight, depending on location, then decrease to 10 kts or less on Sunday.

PRELIMINARY POINT TEMPS/POPS
PDT 36 52 42 54 / 50 100 30 80 ALW 37 53 44 54 / 40 100 40 90 PSC 38 51 39 48 / 30 90 20 80 YKM 27 44 30 45 / 40 100 30 90 HRI 39 54 42 54 / 50 100 30 80 ELN 27 44 29 44 / 20 90 10 80 RDM 35 54 41 57 / 90 90 50 50 LGD 31 46 38 47 / 60 100 50 80 GCD 32 48 37 52 / 100 100 50 70 DLS 40 54 45 54 / 90 100 80 100

PDT WATCHES/WARNINGS/ADVISORIES
OR...Winter Storm Warning until 10 AM PST Sunday for ORZ502.

Winter Weather Advisory until 4 AM PST Sunday for ORZ503-506.

WA...Winter Storm Warning until 10 AM PST Sunday for WAZ030-522.

Winter Storm Warning until 4 AM PST Sunday for WAZ523.

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Des Moines
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Sat -- 01:39 AM PST     -0.57 feet Low Tide
Sat -- 07:36 AM PST     Sunrise
Sat -- 09:31 AM PST     12.44 feet High Tide
Sat -- 12:15 PM PST     Moonset
Sat -- 03:16 PM PST     7.64 feet Low Tide
Sat -- 04:20 PM PST     Sunset
Sat -- 06:59 PM PST     8.87 feet High Tide
Sat -- 09:22 PM PST     Moonrise
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