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PZZ210 Columbia River Bar- 905 Am Pst Mon Dec 4 2023
.gale warning in effect through Tuesday morning...
.small craft advisory in effect from Tuesday morning through Tuesday afternoon...
In the main channel..
General seas..13 to 17 ft subsiding to 12 to 14 ft Tuesday morning.
First ebb..Ebb current of 2.44 kt at 951 am Monday. Seas 13 to 17 ft.
SEcond ebb..Ebb current of 3.39 kt at 934 pm Monday. Seas 11 to 16 ft.
Third ebb..Ebb current of 2.75 kt at 1050 am Tuesday. Seas 12 to 14 ft.

PZZ200 905 Am Pst Mon Dec 4 2023
Synopsis for the southern washington and northern oregon coast.. Strengthening system to persist through Tuesday. Increased southerly winds Monday night through Tuesday. Deepening low pressure system moves from the gulf of alaska over vancouver island on Thursday.

FXUS66 KPQR 041814 AAA AFDPQR

Area Forecast Discussion...UPDATED National Weather Service Portland OR 1014 AM PST Mon Dec 4 2023

Updated public and aviation discussion...

SYNOPSIS
Rain showers continue today before yet another atmospheric river will bring periods of moderate to heavy rain to the area tonight through at least Tuesday night with showers and thunderstorm chances Wednesday. As such, river flooding and urban flooding will remain a concern through at least Wednesday afternoon. A colder frontal system immediately behind the atmospheric river will bring more rain Thursday, albeit relatively lighter, as well as Cascade snow. Signals indicate the potential for another weaker atmospheric river Friday into the weekend.

SHORT TERM
Today (Monday) through Wednesday...UPDATE: Current radar imagery and observations as of 10am PST show rain showers continuing over southwest WA, the Cascades, the Coast Range as a warm front lifts over southwest WA. Since 7am PST, most locations in the Willamette Valley have received less than two to three hundredths of an inch. Meanwhile, a few RAWS stations in the north Oregon Coast Range, Willapa Hills, south WA Cascades, and north OR Cascades near Mt. Hood (all above 2500-3000 ft) have received around 0.40-0.60 in of precipitation. Expect mostly light showers to continue today before the next atmospheric river arrives this evening.

Most of the rivers that rose rapidly yesterday along with smaller creeks and streams have peaked or are near their peaks and will be lowering through today. Urban flooding concerns have also decreased as widespread rain diminished, though roads will likely remain wet and slippery. This period of limited to no rainfall will be short lived as the next weather system approaches the region. A stationary front currently stalled along the OR/WA border will transition into a warm front later this morning. Showers will increase spatially near and long this boundary this morning as well as over the terrain due to orographics as a cold front approaches, though rain rates will remain fairly limited through this afternoon.

Urban flooding and river flooding concerns will increase again tonight through Tuesday night as yet another atmospheric river (AR) takes aim at southwest WA and northwest OR and brings more moderate to heavy rain to the area. A Flood Watch remains in effect for locations west of the Cascades through Wednesday afternoon to cover this threat. The GEFS/EPS continue to suggest this will be a strong atmospheric river with IVT values peaking around 850-900 kg/ms. That being said, the GFS/EURO continue to show very weak synoptic scale and mesoscale forcing. This means rain rates may not get as high as the strength of the AR would suggest, which could result in total rain amounts that are less than expected. Latest forecast has slightly lowered total rain accumulations, though not enough to limit flooding concerns. In addition, confidence is moderate regarding the exact duration of the heaviest rainfall with this system. Right now, most model guidance suggests a prolonged period of moderate to heavy rain for 36-48 hours from around late tonight through Tuesday night as the cold front slowly pushes inland and is slated to very slowly move through the region. There remains uncertainty in how long it will take the cold front to move through, with most guidance showing it stalling throughout Tuesday before pushing east of the area sometime on Tuesday night or Wednesday morning.

Post frontal showers will persist through the day Wednesday as the remnants of the AR continue to shift eastward. Will mainly be showery, but will still see additional accumulations. Overall the flow is fairly messy and unorganized, though some bands of increased vorticity advection paired with the region having upper air support from the jet stream indicates thunderstorm potential in the late afternoon and evening, especially along the coast.

Despite the ongoing uncertainty in specifics of the next three days, river levels will already be elevated going into this next AR event. This means river flooding will remain a concern through Wednesday, even if observed rain amounts wind up a bit less than the current forecast. Forecast rain amounts and expected impacts for the system are discussed below in the hydrology discussion. -HEC/TK/Muessle

LONG TERM
Thursday through Sunday...Thursday a weaker cold front will move in bringing yet another round of showers. This system is not an AR, but rather a true airmass shift. A cold air wrapped low aloft will move over Vancouver Island through the day. This cold front will also bring cooler temperatures in comparison to what we will experience early this week. 850 mb temperatures will be around -3 deg C which will drop daytime temperatures into the 40s for the lowlands and 30s for the mountains. WPC 500 mb cluster analysis indicates uncertainty in the exact track of the low, which will impact the area of heaviest precipitation along the West Coast. Either way, snow levels will be dropping due to colder temperatures, so snow at the passes is likely, though uncertainty remains in exactly how much snow will fall. Latest forecast indicates 6-14 inches of snow above 3000-3500 feet, which is much higher than the previous forecast. NBM v4.1 indicates 50-90% probability of 4+ inches of snow for all of the Cascades from central OR to southern WA. Additionally, it indicates 50-80% probability of 8+ inches of snow and 12+ inches of snow for the Cascades south of Clackamas County and northeastern Skamania County.

On Friday through Saturday, there is a 50-70% probability for another weak to moderate AR based on GEFS/EPS guidance.
However, the pattern is not necessarily "text book" as in that guidance shows a warm airmass converging with a much cooler airmass from the north. Expect precipitation to continue Friday through the weekend, but at this point, confidence is low in specific amounts. -Muessle/HEC

HYDROLOGY
Periods of moderate to heavy rain will continue through Wednesday, with the heaviest tonight through Tuesday night as a strong atmospheric river aims at southwest Washington and northwest Oregon. This is also when flooding concerns are highest. Additional rain amounts expected between 4am PST Monday and 4am PST Wednesday (48 hour rain totals): 3 to 5 inches along the south Washington coast, north Oregon coast, and central Oregon coast, 3 to 5 inches with localized amounts up to 7.5 inches over the Coast Range and Willapa Hills (highest amounts in higher terrain), 1.25 to 2.5 inches across the interior lowlands of southwest Washington and northwest Oregon (highest from Salem northward), 1 to 7 inches across the south Washington and north Oregon Cascades, 0.25 to 1.5 inches for the Lane County Cascades, 2 to 4 inches for the Columbia River Gorge, and 1 to 2 inches for the Upper Hood River Valley.

River levels following the heavy rain yesterday morning have peaked and are lowering. Given the forecast rainfall amounts expected through the middle of the week, river levels will rise again late tonight through Wednesday. Forecasts for most rivers indicate a higher peak than the previous peak Tuesday afternoon into Wednesday morning since river levels will remain elevated.

Most coastal rivers show a 15-40% chance of reaching minor flood stage at some point within the next 10 days. This includes the Naselle River near Naselle, the Nehalem River near Foss, the Nestucca River near Beaver, the Grays River near Rosburg, and the Siletz River at Siletz. The Wilson River near Tillamook has the best chance of reaching minor flood stage as the probability has increased to 65%. Probabilities for major flooding along coastal rivers are around 15% or less.

Additionally, many other rivers across northwest OR and southwest WA are showing anywhere from a 5-35% chance of reaching at least minor flood stage in the next 10 days, except for the mainstem Columbia and Willamette Rivers where the chance of reaching minor flood stage remains lower at 5% or less. While these probabilities have decreased from previous forecasts, there is the potential for probabilities to increase again if QPF amounts increase with future model runs. To view current and forecast river stages for any river gage location across southwest WA and northwest OR, visit https://water.weather.gov/ahps2/index.php?wfo=pqr

Lastly, urban flooding is possible Monday night through Wednesday, especially in low-lying areas with poor drainage. Significant ponding of water and localized roadway flooding is expected on roads. Any motorists with travel plans should also allow extra time for their commute as hydroplaning will be a risk. Never drive through flooded roads. -TK/HEC

AVIATION
18Z TAFs: Radar imagery shows post frontal showers continuing on the leading edge of yet another atmospheric river (AR) which will move over the area after 00Z Tuesday. The AR will shift from north to south with the southern portions of Washington experiencing the wind and rain first, then it will weaken as it moves southward. This AR will bring gusty winds, and heavy rain which will impact visibility and LLWS. CIGs are less of a concern about drastic drops to IFR levels. Rain rates will be high enough to potentially cause some pooling water on area runways or lower lying areas around terminals. Winds will be southerly, and will amplify after 05Z Tuesday. Gusts as high as 40 kt along coastal terminals due to the strong southerly flow. Will note that at about 1000 ft, winds could be as high as 50 kt along coastal terminals and at around 1000 ft. Inland sites will see less wind, though airports are not out of the woods. In the Willamette Valley, those southerly winds will be amplified due to the terrain. LLWS is likely over inland sites. At 1000-2000 ft, winds are around 45 kt, and at 3000-4000 kt closer to 55 kt.

KPDX AND APPROACHES...A mix of MVFR and VFR conditions through the day. The atmospheric river will bring increased winds and rain.
E-W aligned runways will experience higher rates of wind shear, especially when the system passes between 09-15Z Tuesday. This will be the period of heaviest rain and strongest winds. Below 1000 ft, gusts are around 35-40 kt. Not necessarily expecting surface winds to gust to 40 kt, but will still be quite windy.
Pooling water is possible during the periods of heaviest rain.
-Muessle

MARINE
Gales have redeveloped overnight into Monday morning across the waters. Gales may be prolonged as the tight pressure gradient remains over the waters into Monday night before the front move ashore Tuesday morning. May even see a brief period of storm force winds Monday evening but latest models have backed off slightly on that idea. These storm force winds are not wide spread enough to issue a storm warning at this point.

Seas approaching 20 ft on Monday. GWES probabilistic guidance shows about a 50% chance for seas exceeding 20 ft Tuesday morning.
There is another batch of swell arriving Tuesday afternoon. GWES probabilistic shows about 90% seas exceed 20 ft, but less than 10% for exceeding 25 ft.

Also with the elevated seas continuing through mid-week, will maintain the threat of sneaker waves along our coast. -JH

PQR WATCHES/WARNINGS/ADVISORIES

OR...Flood Watch through Wednesday afternoon for Cascade Foothills in Lane County-Central Coast Range of Western Oregon-Central Oregon Coast-Central Willamette Valley-Coast Range of Northwest Oregon-Greater Portland Metro Area-Lower Columbia- North Oregon Coast-Northern Oregon Cascade Foothills-South Willamette Valley.

WA...Flood Watch through Wednesday afternoon for Greater Vancouver Area-I-5 Corridor in Cowlitz County-South Washington Cascade Foothills-South Washington Coast-Willapa Hills.

PZ...Flood Watch through Wednesday afternoon for Coastal waters from Cape Shoalwater WA to Cape Falcon OR out 10 NM.

Gale Warning until 10 AM PST Tuesday for Coastal waters from Cape Shoalwater WA to Florence OR out 60 NM.

Hazardous Seas Warning from 10 AM to 4 PM PST Tuesday for Coastal waters from Cape Shoalwater WA to Florence OR out 60 NM.

Gale Warning until 8 AM PST Tuesday for Columbia River Bar.

Small Craft Advisory from 8 AM to 4 PM PST Tuesday for Columbia River Bar.

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Astoria (Port Docks)
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Mon -- 06:44 AM PST     6.67 feet High Tide
Mon -- 07:40 AM PST     Sunrise
Mon -- 12:25 PM PST     3.90 feet Low Tide
Mon -- 12:57 PM PST     Moonset
Mon -- 04:30 PM PST     Sunset
Mon -- 05:39 PM PST     6.32 feet High Tide
Mon -- 09:51 PM PST     Last Quarter
Mon -- 11:45 PM PST     Moonrise
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Astoria (Port Docks), Columbia River, Oregon, Tide feet

Astoria (Tongue Point)
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Mon -- 06:52 AM PST     7.17 feet High Tide
Mon -- 07:40 AM PST     Sunrise
Mon -- 12:28 PM PST     3.90 feet Low Tide
Mon -- 12:57 PM PST     Moonset
Mon -- 04:29 PM PST     Sunset
Mon -- 05:47 PM PST     6.82 feet High Tide
Mon -- 09:51 PM PST     Last Quarter
Mon -- 11:45 PM PST     Moonrise
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Astoria (Tongue Point), Oregon, Tide feet

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