Marine Weather and Tide Forecast for Willapa, WA

SHORT TERM
Now through Sunday Night...It takes a fairly specific set-up for Western Oregon and Southwestern Washington to see widespread thunderstorm activity, and for those aching to see a little lightning (much like this meteorologist), today and Saturday are shaping up to be best chances we've seen so far this year. Although, as with most of our thunderstorm potential here in the Pacific Northwest, it's not without a potential pitfall or two - nuances in variables like sky-cover can make or break storm development.

As far the overall set-up is concerned, one of the most important pieces is already in place early this morning in the form of an upper-level closed low off the far northern California coastline currently circulating mid to high clouds overhead and indicative of increasing moisture aloft while void of any Pacific marine influence. As the days goes on, this low pressure is expected to ever so slowly drift northward and transition to more of an open wave feature while placing the region beneath further strengthening southerly to southeasterly flow accompanied by broad upper-level divergence. These over- arching synoptics combined with increasing moisture values (PWATs near the 90-95% percentile for this time of year), and daytime heating should provide the ingredients to facilitate deeper convection. Most CAMs and deterministic models depict around 400-800 j/kg of MUCAPE by the mid to late afternoon hours. Assuming this amount of CAPE is truly available and activity is able to initiate (mainly along terrain features like the Cascades at first), effective shear values of ~25 knots could allow a storm or two to organize beyond your basic pop-up thunderstorm - an isolated and longer lived multicellular storm or two are possible mainly south of the Portland Metro where CAPE is maximized. Lightning, small hail, locally gusty winds, and heavy rain would be the primary impacts from any thunderstorm activity. While the overall set-up is decent for west of the Cascades crests, would place the chance of a severe T-storm at around ~5% - for additional context the aforementioned convective parameters don't hold a candle to common set-ups east of the Rockies. Would be a bit more excited if MUCAPE values were 1000-1500+ j/kg and effective shear was 35+ knots but I digress.

As far as timing is concerned, based on the latest 00z HRRR and UW-WRF, showers and thunderstorms would most likely begin around Lane County in the early to mid afternoon hours (1-3pm)
before working northward along the Cascades and I-5 corridor towards the Portland metro by the late afternoon/early evening (5-8pm). After this point due to the loss of daytime heating we'd likely transition back to just lingering showers for Friday night. Now there is one variable alluded to earlier which will play a pivotal role as to whether thunderstorms remain more isolated and pinned to the Cascades, or if modest convection is widespread and infiltrates westward into the I-5 corridor: cloud cover. Almost all of the high resolution guidance which is more bullish on thunderstorm activity (HRRR, UW-WRF, etc.) has mid to high level cloud cover clearing by the late morning and midday hours allowing us to enhance our daytime heating, while the 00z NAMNEST (bearish regarding storms) keeps added clouds overhead effectively capping our instability and limiting activity. This'll be a key facet of the forecast to watch both today and this weekend.

By Saturday, ensemble guidance indicates continued broad cyclonic flow over the Pacific Northwest as the previous closed low turned open wave ejects northward while weakening and a secondary upper-level low swings just off the coast of California effectively stalling the pattern. Shower chances peak area-wide in the afternoon with thunderstorm probabilities ranging from 15-35%, highest over the Oregon Cascades and foothills. While overall instability on Saturday afternoon appears a touch less than the day prior, only 300-600 j/kg of MUCAPE, the strongest cells may once again produce lightning, small hail, gusty winds, and moderate to heavy rain.

Confidence is moderate to high come Sunday the upper-level low pressure previously off the California coast moves inland turning our flow more westerly and thus effectively ending any additional chances for thunderstorms outside of the Lane County Cascades (15% chance here). Still, wrap-around moisture on the northern periphery of the broader circulation will maintain showers chances, especially during the afternoon. Precipitation probabilities range from 60-90% over the Oregon Cascades and foothills to 30-60% for the rest of the region. High temperatures deflate back into the upper 50s to low 60s across the inland Valleys Sunday afternoon placing us close to normal for this time of year. A ho-hum end to a rather interesting couple of days. -Schuldt

LONG TERM
Monday through Thursday...To start the week ensemble models indicate the return to broad WNW-NW flow aloft with a weak embedded shortwave likely moving overhead on Monday maintaining shower chances (50-90%, highest Cascades).
Temperatures stay near to slightly below seasonal normals as well. Shower coverage is expected to decrease Monday night into Tuesday morning thanks to a transient ridge briefly build overhead. Our attention then turns to the next Pacific frontal system expected to arrive sometime between late Tuesday and Wednesday while dropping out of the Gulf of Alaska. While timing differences persist among ensemble members, confidence continue to increase in the return of widespread precipitation during this mid-week timeframe. It's worth noting cooling temperatures along and behind the frontal boundary will likely push snow levels to or just below the Cascade passes sparking renewed snowfall concerns for these areas, primarily during the overnight hours. The NBM shows a 50-70% chance for the Cascade passes to see 6+ inches of snowfall from 5pm Tuesday to 5pm Thursday with a 10-30% for 12+ inches during that same period.
This'll be something to keep an eye on as we get into next week in addition to the return of marginal frost concerns mid to late week as well. -Schuldt

AVIATION
Generally VFR conditions are in place across the region with mid to high level clouds slowly moving from south to north across the airspace. The lone exception is KEUG where patchy fog has developed on the far southern end of the Willamette Valley - IFR to LIFR conditions possible until 15-16z. Expect the airspace to remain relatively dry through around 18Z-20Z Friday.
After this point showers and thunderstorms likely develop around Lane County before pushing northward along and east of the I-5 corridor the remainder of the afternoon into the early evening.
Given decent model consistency, have maintained PROB30 groups mentioning thunderstorms for for KEUG, KSLE and KUAO as those sites currently have the highest chance to see activity.
Confidence remains lower for terminals in the immediate Portland Metro but the period to watch will be 00-04z Sat for this area - did not include a mention of thunder with the 12z Fri TAF package.
Thunderstorm chances regionally rapidly decrease Friday evening.

It should be noted locations that do see stronger showers or thunderstorms will have the potential for lightning, small hail, moderate to heavy rain, and gusty/erratic outflow wind gusts up to 35-45 knots. This activity would also result in intermittent MVFR/IFR conditions if it moves directly overhead.

KPDX AND APPROACHES...Expect predominately VFR flight conditions through the TAF period with mid to high cloud cover at times.
Locally, shower (50-70%) and thunderstorm (25%) chances ramp up around 00-01z Saturday before diminishing by 05-06z. Stronger showers or thunderstorms will have the potential for lightning, small hail, moderate to heavy rain, and gusty and erratic outflow wind particularly at the onset of activity in the late afternoon hours if it occurs. -99/42

MARINE
Overall conditions remain rather benign the next several days as north to northwest winds switch southerly today into tonight before shifting more westerly by the start of next week.
Confidence is high wind gusts hold below 20 kt through the Monday into Monday night. Seas around 4 to 7 ft persist through the middle of next week as well. It's worth quickly noting there is a ~10% chance of thunderstorms today through Saturday across all waters rotating in from the southeast. Any thunderstorms that do develop could produce lightning hail, gusty and erratic winds as well as a less than 2% chance for a funnel cloud or waterspout.
Our attention turns to the arrival of a decently strong frontal boundary the second half of Tuesday into Wednesday likely bringing the return of Small Craft Advisory wind gusts and seas around 7-10 ft. -99/42

PQR WATCHES/WARNINGS/ADVISORIES
OR...None.
WA...None.
PZ...None.