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PZZ110 Grays Harbor Bar- 236 Am Pdt Sat May 4 2024
combined seas 2 to 4 ft. Bar conditions light. Maximum ebb currents will occur around 215 pm today and 300 am and 315 pm Sunday. The Sunday morning ebb will be strong.

PZZ100 236 Am Pdt Sat May 4 2024
Synopsis for the northern and central washington coastal and inland waters - A frontal system will move through the southern portion of the waters today. Another system will move across the waters Sunday night into Monday morning. High pressure will build back over the area Monday night and Tuesday with the ridge remaining in place Wednesday.

FXUS66 KPQR 041740 AFDPQR

Area Forecast Discussion National Weather Service Portland OR 1040 AM PDT Sat May 4 2024

UPDATED AVIATION DISCUSSION

SYNOPSIS
Steady light to moderate rain will continue across the lowlands of SW Washington and NW Oregon, while snow levels lower to just below the Cascade passes later this morning then remain there through Sunday. Low pressure off the Pac NW coast will move onshore near the OR/CA border this evening, with wraparound precip persisting through Sunday for much of the forecast area. Travel impacts in the Cascades will largely occur tonight into Sunday morning. Another round of rain and Cascades snow is expected Monday as the next system moves onshore, with post-frontal showers lingering into Tuesday. A significant warming and drying trend is expected later in the week as high pressure builds aloft over the region.

SHORT TERM
Now through Monday Night...Latest GOES-West infrared and water vapor imagery reveal broad low pressure aloft just off the Pac NW coast. An associated frontal band has tapped into some subtropical moisture with blended total precipitable water (TPW) values of around 1 inch associated with the front. The frontal zone will more or less pivot over northern Oregon as the upper low drifts SE and moves onshore near the OR/CA coast through this evening. As a result, expect fairly steady light to moderate precipitation through this evening. This may continue all the way through Sunday if most of the deterministic models are correct in maintaining deformation precipitation over much of the CWA NBM median QPF shows weekend precip totals of 0.4 to 0.8 inch over the lowlands with 1-2 inches still to come over the Cascades.

Snow levels have been lowering a bit slower than expected overnight, so we postponed the start time of the Winter Wx Advisory for our Oregon Cascades until 10 AM. The temperature at Timberline Lodge actually rose to 38 deg F at 3 AM, indicating there is still a ways to go before snow levels lower to the Cascade passes. This delay could be very beneficial for those with plans to travel across the Cascades today - if the transition to snow occurs later this morning or during the midday hours, the roads may just remain wet or occasionally slushy due to the strong May solar energy (even with cloud cover). 09z RAP analysis suggests wet bulb zero heights below 5000 ft remain offshore, adding confidence to the delay in the lowering of snow levels.

Despite 1-2 inches of QPF for the Cascade passes through Monday morning, snow accumulations should only amount to a few inches for the passes due to the marginal thermal profile and resulting low snow-to-liquid ratios. By far, the most significant deviations our forecast makes from NBM were in the snow-to-liquid ratios (SLRs). Our SLRs were largely based on the more reasonable WPC guidance, though we lowered the SLRs 10-15% from even the WPC guidance (and 30-40% below NBM guidance). This was necessary to get the SLRs below 10:1 for the passes, where NBM was showing SLRs in the 13:1 to 16:1 for the passes and even higher than that for higher elevations. Such SLRs would be difficult to achieve for the passes even in the middle of winter, much less the middle of spring.

A relative lull in precipitation is possible Sunday night as the upper low and its deformation zone shift into the Rockies. However the next system and reinforcing cold front are likely to move onshore Monday morning, with post-frontal showers persisting through Tuesday.
Temperatures and snow levels will remain below seasonal normal, with lowland highs stuck in the 50s through Tuesday. Weagle

LONG TERM
Tuesday through Friday...The long term forecast is highlighted by a rapid change in the weather pattern from cool and showery conditions Monday through Tuesday to much warmer and drier conditions late in the week. Models and their ensembles continue to show a shortwave trough moving across Washington and Oregon Monday into Tuesday, bringing a shift from westerly flow aloft to northwesterly behind the trough axis. This trough will bring the continuation of cool and showery weather with high temps mainly in the 50s and snow levels around 4000 ft on Monday falling to 3000 ft on Tuesday.

Beyond Tuesday, confidence is high for a rapid shift in the weather pattern from cool and wet to warm and dry. This abrupt shift is the result of an upper level ridge that is set to build over the region, and all four clusters shown in WPC's cluster analysis depict this ridge with varying amplitudes. The deterministic NBM currently suggests highs in the 60s Wednesday, 70s Thursday (except 60s at the coast), and 80s Friday (except low 70s at the coast). The coolest model solutions are similar to the NBM 10th percentile, showing inland high temps only peaking in the mid 70s on Friday. Meanwhile, the warmest model solutions show highs near 90 degrees from Portland to Eugene. Either way, temps will be running above normal for this time of year. The probability for high temps at or above 80 degrees on Friday is already at 70-80% across the interior lowlands, which is quite high for a forecast that is seven days out. Overall, the warmest temps of the year so far are likely to occur next weekend.
This may draw some people to area rivers and/or lakes, but keep in mind water temps are still very cold and river currents will be swift with mountain snowmelt. We plan on actively messaging cold water safety tips late next week in preparation for the warm weather ahead, as cold water shock and hypothermia will be a very real risk for anyone who decides to take a swim. -TK

AVIATION
Widespread rain continues across the area today into tonight. Flight conditions remain quite variable ranging from VFR to IFR, although most locations currently sit at MVFR. At least there is high confidence (65-95% chance) for mainly MVFR conditions through the overnight hours for both the coastal and inland areas. If there is any trend, later this afternoon will transition to more westerly flow with chances for MVFR/IFR slightly decreasing and chances for VFR increasing, but probably not enough to see prevailing VFR conditions at any point during the TAF period.

Wind generally less than 5-10 kts inland but coastal areas a little breezier with westerly winds 10-15 kt.

PDX AND APPROACHES...MVFR conditions expected to prevail through the rest of the day and overnight, but with around 20-30% chance for IFR conditions into the midday hours and again after ~09z through Sunday morning. Thus brief periods of IFR cigs will need to be monitored but chances for IFR appear too low to include as prevailing in the 18z TAF package. Winds generally light, variable early becoming southwest less then 10-15 kt.
-Schuldt/mh

MARINE
Active weather pattern continues into early next week with series of troughs moving through the waters. Currently in between systems with weak high pressure over the waters. However with relatively short wave period and seas around 6 to 8 ft will have steep seas later this morning through this evening. So have issued a Small Craft Advisory for hazardous seas. Next front arrives Sunday and bring gusts to 25 kt as well as steep seas across most of the waters Sunday morning through Sunday night.
Following this front high pressure over the northeast Pacific will build over the waters and bring breezy west to northwest winds (gusting 20-25 kt) across the waters later Monday into Tuesday.
The high pressure shifts closer to the waters later next week. /mh

PQR WATCHES/WARNINGS/ADVISORIES
OR...Winter Weather Advisory until 6 PM PDT Sunday for ORZ126>128.
WA...None.
PZ...Small Craft Advisory until 10 PM PDT this evening for PZZ251>253-271>273.

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Willapa City
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