Sunrise 5:49 AM   Sunset 8:09 PM Moonrise 11:58 PM   Moonset 6:33 AM

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PZZ135 Puget Sound And Hood Canal- 301 Am Pdt Sat Apr 27 2024
.small craft advisory in effect from 5 am pdt early this morning through this afternoon - .
Today - S wind 15 to 25 kt easing to 10 to 20 kt in the afternoon. Wind waves 2 to 4 ft. Tonight - S wind 10 to 20 kt. Wind waves 1 to 3 ft. Sun - SW wind 10 to 20 kt. Wind waves 1 to 3 ft. Sun night - SW wind 15 to 25 kt becoming S 10 to 20 kt after midnight. Wind waves 2 to 4 ft. Mon - SW wind 5 to 15 kt. Wind waves 2 ft or less. Mon night - SW wind 5 to 15 kt. Wind waves 2 ft or less. Tue - S wind 5 to 15 kt becoming sw to 10 kt. Wind waves 2 ft or less. Wed - Light wind. Wind waves less than 1 ft.

PZZ100 301 Am Pdt Sat Apr 27 2024
Synopsis for the northern and central washington coastal and inland waters - The next frontal system will move across the area later this evening high pressure will build over the waters Tuesday night and Wednesday with breezy southerly winds. Active weather continues with the next frontal systems poised to move over the area waters Monday and Thursday.

FXUS66 KPDT 271113 AFDPDT

Area Forecast Discussion National Weather Service Pendleton OR 413 AM PDT Sat Apr 27 2024

Updated Aviation Discussion

SHORT TERM
Today through Monday...Overnight satellite imagery shows relatively clear skies around the forecast area outside of our mountain zones. Synoptically, we find ourselves under the axis of a low currently digging down towards the Four Corners region. Saturday will serve as a transition day as the exiting low will invite mild zonal flow over the forecast area, before a stronger low begins to move towards the region by Sunday. Expecting a relatively quiet Saturday, with precip chances isolated mainly to the Cascade crests, however winds will pick up as amplified flow aloft mixes down into the lower elevations ahead of the aforementioned low.

Weather becomes a bit more active Sunday into Monday as the oncoming low's influence becomes more apparent. Guidance depicts a jet max overhead Sunday associated with the southern flank of the low, which centers itself over BC, before easing southward and inviting more WSW winds aloft and thus more moisture into the lower elevations by Monday. End result will be precip chances both days, especially across the Cascades, and breezy winds. Guidance generally shows sub- advisory level winds, with Monday being the strongest day, however the strongest belt of winds looks to shift just to our south that day. Still, models suggest wind gusts up to 35 mph through the Oregon Basin, Gorge, and Simcoe Highlands, with 40 mph gusts along exposed ridgetops. CAMs may pick up Monday's winds a bit better once they go out long enough, but am not anticipating headlines at this time.

As far as precip is concerned, these patterns of amplified zonal flow are often conducive for heavy precip along the Cascade crests.
QPF guidance has picked up on this, and has trended upward over the last 24 hours. With this oncoming low stemming from the Gulf of Alaska, colder air will intrude in and drop snow levels down into the 2500-3000 ft range overnight Sunday into Monday. This, combined with the recent upward trend in precip amounts, suggest that accumulating snow is possible for the Cascade passes. Confidence is on the lower end, however (30-40%), as it is the last week of April after all. Road temps will be warm, and the zonal flow preceding the cold air intrusion will make for more mild conditions before snow levels really begin to drop. Will see how guidance evolves over the next 24 hours, but cannot rule out advisories so as to prevent motorists from being caught off guard despite the time of year. The more southerly component of the winds aloft Monday could also invite storm chances across our mountain zones, however confidence in this occurring is also low (10-15%).

High temps over the period will dip down towards the 50s as this colder air advects into the region by Monday. Elevated winds may keep the atmosphere well-mixed enough to prevent overnight lows from bottoming out too much, but if this Alaskan low lingers about for long enough, freezing temperatures could materialize (confidence 20- 30%) across some of our lower elevation Zones by the start of the oncoming work week. Evans/74

LONG TERM
Tuesday through Saturday...The long term forecast will start off active as an upper trough continues to impact the PacNW. However, there is much uncertainty in the progression of the synoptic pattern Wednesday into next weekend, and therefore uncertainty in temperature and precipitation forecasts.

Ensemble cluster solutions start in great agreement Tuesday that an upper low will continue to slide east across the northern tier states, resulting in continued mountain precipitation chances and breezy west winds in the lower elevations. Across the mountains, NBM probabilities for 0.1 inches of QPF peak between 50-60% through Tuesday, and though much of this precip will be falling as snow, there is moderate confidence (60%) in only up to 1 inch of snow in the eastern mountains and WA Cascades and 2-3 inches along the OR Cascade crest. While winds won't be as strong as Monday, NBM probabilities suggest there is 60-70% chance of wind gusts exceeding 35mph in the OR Columbia Basin, and along the exposed ridges across Klickitat, Yakima, and Kittitas counties.

Wednesday through Saturday, uncertainty in the synoptic pattern grows into the weekend, as ensemble members disagree on the progression of ridging/troughing over the PacNW during this period. Late Tuesday into Wednesday, ~60% of ensemble cluster members from the GFS, ECMWF, and Canadian ensemble suites want to push a developing upper ridge over the PacNW, resulting in a drying and warning trend; meanwhile the other 40% favor some form of troughing into the PacNW, keeping persistent chances of mountain precipitation and cooler afternoon temperatures(mid 50s to mid 60s). Late Wednesday into Thursday, 36% of the cluster members favor troughing moving into the area for increased precipitation chances across the Cascades and eastern mountains, while 30% have a weaker shortwave trough overriding a ridge over the region for light mountain precip and comparatively mild temperatures(upper 50s to mid 60s), and lastly 34% of members favor the upper ridge over region with dry conditions and comparatively warmer temperatures(60s to low 70s). Late Thursday into Friday, 55% of members favor upper level ridging with a continued dry and warm trend while the remainder 45% of members bring a trough into the PacNW with cooler temperatures and continued precip chances across the mountains. Finally, late Friday into Saturday contains the most disagreement, with solutions ranging from ridging offshore or centered over the PacNW, and/or an upper level trough setting up offshore with southwest flow aloft. Throughout the midweek to next weekend, confidence is low (25-30%) in the going forecast due to high uncertainty day to day, as well as great variability in shift to shift trends. That said, NBM guidance depicts only a 20-40% chance for 0.1 inches of QPF in the mountains each day; as for afternoon temperatures, the NBM suggests that there is a 70-80% chance of exceeding 70 degrees across the Columbia Basin/Gorge and adjacent valleys Thursday through Friday, suggesting the ridging solution is favorable. Lawhorn/82

AVIATION
12Z TAFs...VFR conditions to prevail through the period. CIGS of bkn-ovc will be AOA 5kft to 12kft AGL throughout the period, with CIGS exceeding 12kft AGL after 4Z-5Z. Westerly winds will be increasing after 16Z-18Z to 12-17kts with gusts up to 25kts at sites DLS/PDT/BDN/YKM/ALW/PSC, while site RDM is expected to see winds less than 12kts. Winds will become less than 12kts at all sites generally after 1-3Z, except at site PSC where winds will decrease by 9Z. Lawhorn/82

PRELIMINARY POINT TEMPS/POPS
PDT 59 40 61 38 / 10 10 0 10 ALW 64 45 63 41 / 10 10 0 10 PSC 66 46 66 45 / 10 0 0 0 YKM 62 38 63 37 / 10 0 0 10 HRI 64 43 65 41 / 10 0 0 0 ELN 58 38 58 35 / 10 0 0 10 RDM 54 34 58 32 / 10 10 0 10 LGD 57 39 59 37 / 10 10 10 10 GCD 57 36 61 34 / 10 20 0 10 DLS 61 45 62 41 / 10 10 0 20

PDT WATCHES/WARNINGS/ADVISORIES
OR...None.
WA...None.

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Des Moines
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