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PZZ210 Columbia River Bar- 255 Pm Pdt Wed Apr 24 2024
.small craft advisory in effect from late tonight through Thursday evening - .
In the main channel -
General seas - 3 to 5 ft building to 6 to 8 ft Thursday evening.
First ebb - Ebb current of 3.55 kt at 558 pm Wednesday. Seas 5 ft.
SEcond ebb - Strong ebb current of 5.7 kt at 604 am Thursday. Seas 6 to 7 ft.
Third ebb - Ebb current of 3.3 kt at 629 pm Thursday. Seas 6 to 7 ft.

PZZ200 255 Pm Pdt Wed Apr 24 2024
Synopsis for the southern washington and northern oregon coast - The next frontal system arrives Thursday, returning gusty southwesterly winds and steep seas across the waters.

FXUS66 KPQR 242221 AFDPQR

Area Forecast Discussion National Weather Service Portland OR 321 PM PDT Wed Apr 24 2024

SYNOPSIS
Our stretch of drier weather finally comes to an end - wetter April weather had to return at some point. A pacific frontal system is slated to arrive Thursday morning bringing widespread rainfall to the region and heralding the start cooler, showery, and unsettled conditions through the weekend into next week. It’s worth noting Friday into Saturday snow will also once again be possible down to the highest Cascade passes above ~4,500ft, however, any appreciable snowfall impacts likely remain confined to the mountain tops above 5,500ft.

SHORT TERM
Tonight through Sunday...This afternoon and evening we continue to wait on the arrival of our next weather disturbance in the form of any upper-level trough and accompanying frontal boundary currently moving over the eastern Pacific towards the Pacific Northwest. Latest high resolution guidance like the HRRR has pushed back the arrival of this feature by an hour or two late tonight into Thursday morning but in general expect rainfall to reach the I-5 corridor by 4-6am with periods of steady light rain through the day before breaking to showers Thursday evening. The upper-level forcing associated with this disturbance leaves much to be desired but it’ll at least come with a decent moisture plume highlighted my model PWAT values pushing 0.8-1” which is around 0.3” inches above normal. Thursday night into Friday morning the axis of the aforementioned trough moves overhead pushing snow levels near 4,500-5,000ft. While some wet snow likely makes it down to the higher pass areas like Santiam and Willamette pass, the warmer antecedent conditions should help to limit any pavement accumulation before daytime heating takes hold later Friday morning. This daytime heating and cooler temperatures aloft will allow for some additional instability come Friday afternoon which could support locally moderate to heavy showers, although after interrogating deterministic model soundings from the GFS, ECMWF, and NAM the available CAPE doesn’t appear deep enough to support T-storms and is held below the mixed phased(lightning generation) portion of the atmosphere(-10 to -20c). As far as precipitation totals are concerned Thursday through Friday, the NBM projects rainfall amounts of 0.6-0.9 inches across the Willamette Valley/SW Washington, and 1-2.5 inches for the coast/coast range and Cascades - locally the highest along the coast range in Tillamook/Clatsop County.

Late Friday into Saturday the upper-level trough feature amplifies and quickly progress southeastward into the four corners region of the Great Basin while heights briefly rise over the region due to the passage of a weak transient shortwave ridge. Confidence is high this will help to consolidate lingering shower activity to primarily the elevated terrain of the coast range and Cascades leaving the valley with 10-25% PoPs. That said, guidance indicates the arrival for an upper- level shortwave and weak warm-frontal boundary extending southward off a parent low parked over the gulf of Alaska increases chances for precipitation Saturday afternoon through Sunday. Temperatures late week through the weekend remain near to slightly below normal for mid to late April. /Schuldt


LONG TERM
Sunday Night through Wednesday...Pattern is rather progressive, with fronts moving off the northeast Pacific into the Pacific NW. Yet another front will push across the region Sunday night, with post-frontal showers on tap for Monday. Still a bit cooler than that expected for late April, with overall temperatures in the lowlands in the 50s to lower 60s. Snow levels will run 2500 to 3500 ft, which will maintain some snow at times for the higher terrain of the foothills, as well as most of the Cascades.

Broad upper low over the southeast Gulf of Alaska will gradually drop southeastward off the Pac NW coast, moving to north Calif/southwest Oregon by Thu. As it does, it will maintain rather baggy upper trough over the region, with main trough axis just offshore. As such, look to remain coolish with showers. But, ,think system may stay far enough offshore that will have some dry periods mixed in that timeframe for Tue to Thu. Some differences with long range models, as GFS holds more southerly flow aloft (better for showers), but ECMWF being more southwesterly (favoring less showers and GFS). Either way, still coolish as will see plenty of clouds about the area. Does appear that the whole upper trough will push inland Fri/Sat, with more showers.
/Rockey



AVIATION
Marine stratus continues to sit along the coast, and as of 21z Wed, KAST has already dropped to MVFR ceilings, with most other terminals sitting somewhere between 3500-6000 feet.
KONP is just barely at VFR thresholds, and sees a 60-70% chance of ceilings dropping to MVFR within an hour or two (23z-00z Wed/Thu).
Once MVFR conditions develop at the coast, there is an additional 60-70% chance of IFR conditions developing later, around 03-06z Thu.

At inland terminals, VFR conditions continue until later tonight, when a more major front moves in around 11-13z Thu. All inland terminals can expect around a 80-90% chance of MVFR ceilings and rain. Chances of IFR ceilings at inland terminals is only around 10-20%, so have not included in the TAF.

Notes: The ASOS at KTTD is only available via the dial in option.
The AWOS at KMMV is still out of commission and there is still no estimated time of repair.

PDX AND APPROACHES...VFR thresholds remain in place until Thursday morning, when a front arrives and lowers ceilings to high end MVFR. 80% confidence in MVFR ceilings by 15z Thu, but only 10% confidence in IFR ceilings. Winds become southerly and gust up to around 10-12 kts after the front passes. /JLiu

MARINE
A warm front associated with a low well off the B.C.
coast moves across the waters this evening. The following cold front moves across the waters Thu afternoon. Expect to see gusts 25 to 30 kt across the waters in the afternoon, with a brief period with gusts to 35 kt for zones PZZ272,273,252,253 as the front moves through the waters. High resolution guidance also suggests a 30-50% chance of occasional gale force gusts to around 34 kt the frontal passage between 12-4 PM PDT Thursday. Wind forecast is a bit higher then previous forecast Thursday night so will extend the Small Craft Advisory into Friday evening. In addition to the wind seas will be steep and choppy.

Looking ahead into the weekend and early next week, marine conditions will be characterized by a series of relatively weak frontal systems.
NBM guidance suggests a less than 5% chance of wind gusts exceeding 34 kt across the waters in the long term forecast. /mh

PQR WATCHES/WARNINGS/ADVISORIES
OR...None.
WA...None.
PZ...Small Craft Advisory from 5 AM to 8 PM PDT Thursday for PZZ210.

Small Craft Advisory from 5 AM Thursday to 2 AM PDT Saturday for PZZ251>253-271>273.

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