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PZZ135 Puget Sound And Hood Canal- 216 Am Pdt Mon Apr 29 2024
Today - SW wind to 10 kt. Wind waves 1 ft or less. Tonight - SW wind 5 to 15 kt. Wind waves 2 ft or less. Tue - S wind to 10 kt becoming N in the afternoon. Wind waves 1 ft or less. Tue night - NW wind to 10 kt becoming S after midnight. Wind waves 1 ft or less. Wed - S wind 5 to 15 kt. Wind waves 2 ft or less. Wed night - SW wind 5 to 15 kt becoming S to 10 kt after midnight. Wind waves 2 ft or less. Thu - S wind to 10 kt becoming w. Wind waves 1 ft or less. Fri - Light wind becoming S to 10 kt. Wind waves less than 1 ft becoming 1 ft or less.

PZZ100 216 Am Pdt Mon Apr 29 2024
Synopsis for the northern and central washington coastal and inland waters - A weak surface low will pass across the southern offshore waters this morning with rough seas and breezy conditions continuing. Another weak surface low will cross the area waters on Tuesday. High pressure will build across the region Tuesday and Wednesday before yet another weak surface low and attendant cold front move across the region Wednesday night into Thursday.

FXUS66 KSEW 291048 AFDSEW

Area Forecast Discussion National Weather Service Seattle WA 348 AM PDT Mon Apr 29 2024

SYNOPSIS
A cool low pressure system from Canada will continue to track south into Washington today. Showers with the chance of thunderstorms will be possible across western Washington today.
Moderate mountain snow will continue in the Cascades, with accumulations greatest at elevations greater than 3,500 feet.
There will be a break in activity late Tuesday into early Wednesday before another disturbance passes through. Temperatures will increase from the 50s to the 60s by the end of the week.

SHORT TERM /TODAY THROUGH WEDNESDAY/
Complex weather picture next 36 hours with a system passing through. An upper level low is tracking southward from B.C. Canada southward into Washington today. This is driving a jet streak with upper level divergence/low level convergence over the state, which combined with a 500 mb vorticity max. provides a lifting mechanism for precipitation. The temperatures with this low at the mid levels are unusually cool for this time of year, with 500 mb temperatures at -30 to -35 C. Satellite also shows a surface low over Haida Gwaii, with an associated surface trough boundary tracking southeastward with the previously mentioned upper-level features.

From this morning, convergence zone showers over Skagit/Whatcom counties dissipated. Radar shows an apparent meso-low rotating convective showers inland from Clearwater to Chehalis. Hi-res model guidance shows this feature tracking into Puget Sound during the early morning hours, which will cause a wet commute for most areas in the sound. Coverage of showers will increase this morning into the afternoon with multiple rounds making their way through the coverage area.

SPC has all of western Washington in a general thunder risk for Monday (as well as Tuesday in the Southwest Interior). With the cool air aloft and upper air dynamics, this will cause the atmosphere to become unstable throughout the day. Given CAPE values up to 200 J/kg (with little CIN), 0-6 km shear 35-40 kt, and SRH 80-100 m2/s2, a couple organized thunderstorm cells are possible with the shower activity that develops. Exact location of the thunder activity is hard to pinpoint at this time, but Hi-res guidance suggests a convergence zone developing Monday afternoon over Island/Snohomish/King counties, with some additional cells forming in south Puget Sound, and the coast/Southwest Interior.
The strongest cells may be capable of producing small hail and gusty winds, as well as lightning. Activity is expected to last through Monday night/Tuesday morning.

For the mountains, moderate snow remains on track to fall in the Cascades today. A couple of rounds of snow are expected in the morning and afternoon/evening. Based on snow levels dropping quickly to around 2,000-2,500 ft, and above freezing temperatures from these snow levels to around 3,500 ft, snow is not expected to be impactful at these levels (including Snoqualmie Pass). Below freezing surface temperatures at 3,500 ft and higher will cause snow to stick to surfaces. Snowfall rates are expected to range from a quarter of an inch to half an inch an hour (with any convective banding capable of brining rates to 1 inch an hour).
With confidence that snowfall will last through Monday evening, the winter weather advisory was extended to 2 AM PDT (for elevations greater than 3,500 ft - including Snoqualmie Pass).
Snow totals are expected to range from 4 to 8 inches, with heavier amounts possible with any convective snow banding that materializes.

Shower activity will continue through first part of Tuesday. As the low departs, a weak upper level ridge will dry the region out late Tuesday/early Wednesday. A weakening surface system/upper level trough will return the chance of showers Wednesday afternoon. High temperatures will range from the 50s in the lowlands, to the 30s and 40s in the mountains. Lows will dip down into the upper 30s and 40s in the lowlands, and the 20s/30s in the mountains. Winds will remain light around 5 to 10 mph.

LONG TERM /THURSDAY THROUGH SUNDAY/
Still a lot of disagreement between ensemble/deterministic models with the long-term pattern.
With most models showing troughing in the extended, a chance of showers will be possible Thursday into the weekend. Heavy precipitation in the Southwest Olympic region is possible Thursday and Sunday, but confidence is low due to variations in the models.
Temperatures return into the mid 60s by Friday into the weekend.
Winds are expected to be light.

HPR

AVIATION
Broad upper-level troughing remains anchored across the Pacific Northwest with a pair of shortwave impulses pivoting through the main trough axis-the first this morning and the second Tuesday morning. Each of these are driving weak surface low pressure centers, traveling across southern Washington and northern Oregon.

A variety of flight restrictions this morning, though conditions have largely improved as more organized showers have moved onshore.
A mix of MVFR and low-end VFR through 18Z before CIGs lift into more solid VFR levels. An organized complex of showers will move across the southern Puget Sound terminals this morning through 12Z, with more VCSH through the remainder of the day. Once again, cannot rule out a lightning strike or two given modest instability and anomalously cold air aloft, though confidence is too low to include mention in any TAFs at this time.

Winds have shifted more to the south-southeast early this morning, but are expected to shift back to the south-southwest by 12Z with westerly winds at CLM and HQM. Mesoscale guidance has been pushing the convergence zone southward through PAE around 16Z, though how far south this area of convergence shifts remains uncertain. Winds should largely favor the southwest after 03Z through the overnight.

KSEA...VFR conditions this morning as an more organized area of light rain moves over the region through 13Z. A 60% chance for MVFR CIGs by 12Z, which have been observed in this area of rain to our west. A return to VFR is expected after 14Z through the evening with MVFR CIGs developing after 10Z Monday night. Scattered showers with a lightning strike possible this afternoon. Winds have shifted to the southeast ahead of this area of showers, but should back to the southwest later this morning from 8 to 12 kt, where they are expected to hold through early tonight. The convergence zone looks to shift south towards BFI after 16Z, but only a 25% chance for winds to shift to briefly shift to the north after 20Z.

Davis

MARINE
Active and unsettled weather continues as we move into the new workweek. Showers, some convective in nature with isolated lightning strikes, will continue to skirt across the area waters today into tonight as a pair of mid-level disturbances pivot southeast beneath a longwave trough, driving a pair of weak surface lows across the southern Washington offshore zones this morning and Tuesday.

Small Craft Advisories continue over the coastal waters for steep seas around 8 to 10 feet with a dominant period around 9 to 10 seconds through 5 AM. Breezy winds will continue today, though opted to issue Small Craft Advisories through the central and eastern Strait of Juan de Fuca, where confidence is highest for wind gusts over 21 kt (80%). Brief and more isolated advisory-level wind gusts cannot be ruled out elsewhere with the convective showers today, though confidence is too low for additional advisories.

Seas from 8 to 10 feet this morning will drop closer to 7 to 9 feet later today, then rise back to 8 to 10 feet into Tuesday as the next weak surface low traverses the area waters. Seas then look to subside to 4 to 7 feet Wednesday into the latter half of the week.

Davis

HYDROLOGY
No river flooding expected over the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES
WA...Winter Weather Advisory until 2 AM PDT Tuesday for West Slopes North Cascades and Passes-West Slopes North Central Cascades and Passes-West Slopes South Central Cascades and Passes.

PZ...Small Craft Advisory from 11 AM this morning to 10 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 1 PM this afternoon to 10 PM PDT this evening for East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 5 AM PDT early this morning for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.

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Tacoma
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Mon -- 01:58 AM PDT     Moonrise
Mon -- 03:45 AM PDT     7.95 feet Low Tide
Mon -- 05:55 AM PDT     Sunrise
Mon -- 07:47 AM PDT     9.87 feet High Tide
Mon -- 09:36 AM PDT     Moonset
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