Marine Weather and Tide Forecast for Kalama, WA

SHORT TERM
Now through Friday...A weak upper-level shortwave exiting eastward through this morning will see light rain dwindling through the day. Areas of steadier rain early will give way to scattered shower coverage into the afternoon as the modest trailing mid-level cold pool passes overhead. By late this afternoon into the evening, showers will become even more isolated in nature as low-amplitude shortwave ridging begins to arrive from the west, with the Cascades and coastal areas the most likely to see lingering precipitation. Rainfall totals are expected to be light, with portions of the Cascades north of Santiam Pass favored to see the highest amounts, namely a 40-60% chance of 0.25" or more through this evening, while those chances drop below 25% elsewhere across the region as expected amounts remain around 0.05-0.15". The lowest totals of less than 0.05" are likely across northern portions of Pacific County, WA which will remain farthest from the shortwave forcing. Elevated cloud cover and persistent onshore flow will see temperatures remain seasonably cool with afternoon highs in the 50s and 60s and overnight lows largely in the 40s.

Another weak and progressive trough will pass over the region early on Friday with most areas remaining dry. The Cascades will again be the most likely to see precipitation, but chances of even 0.01" are only 40-60%. Elsewhere, there is less than a 20% chance of any accumulating rain. By the afternoon, heights aloft will begin to rise in earnest as longwave ridging begins to builds over much of the western CONUS. Temperatures will begin to trend warmer into the 60s and 70s Friday afternoon.


LONG TERM
Friday Night through Wednesday...There remains high confidence in high-amplitude ridging centered over the Interior West persisting into Sunday. Mid-level temperatures rapidly rising to around 10-12C at 850 hPa through the weekend will support surface temperatures some 5-10 degrees above normal, reaching afternoon highs in the mid to upper 70s along the I-5 corridor and 60s to low 70s elsewhere. Areas along I-5 will see generally a 30-50% chance of reaching 80F or higher each day through the weekend. Overnight low will similarly trend toward milder temperatures in the mid 40s to mid 50s each night.

Late Sunday into Memorial Day, chances begin to increase for a brief breakdown in upper ridging as an increasing number of ensemble members favor a negatively-tilted shortwave trough undercutting the ridge, before becoming cutoff over California.
Locally, this pattern would yield cooler but still above normal temperatures on Monday with increased chances for rain showers. Given the warm antecedent conditions and depending on the timing of shortwave forcing, convective weather remains a possibility Sunday or Monday afternoons, most likely within the Cascades. Resurgent ridging into Tuesday would then see a quick return to warm and dry weather across the region. Confidence rapidly decreases Wednesday and beyond as ensemble spread increases dramatically. Persistent ridging could see a prolonged period of warm to hot temperatures and dry weather continue, while a breakdown of the ridge could instead see a return to cooler and wetter conditions. -Picard

AVIATION
A weak disturbance moving over the PacNW will continue to produce light showers across NW Oregon and SW Washington, tapering out by 15-18z Thursday except for over the Cascades where showers could continue through 00z Friday. There's a 10-25% chance of MVFR ceilings within the showers. Otherwise, predominately VFR conditions are expected inland through the TAF period with mid to high level cloud cover. However, latest guidance suggests some clearing of these mid to high level clouds might occur over the southern Willamette Valley by daybreak, which is producing a 30-40% chance of MVFR ceilings at KEUG from 12-18z Thursday.
Additionally, coastal sites have a 40-70% chance of MVFR ceilings through 18-20z Thursday. Winds remain onshore and generally less than 5-10 kts. -HEC

PDX AND APPROACHES...Predominately VFR conditions expected through the TAF period with overcast mid to high clouds as a disturbance produces scattered showers through 15-19z Thursday.
There's a 20-30% chance of MVFR conditions from 15-19z Thursday.
Light and variable winds less than 6 kts. -HEC

MARINE
Pressure gradients continue decreasing across the waters early Thursday morning as surface high pressure ridge axis sets up right over the coastal waters off of Oregon and Washington. Winds continue to decrease, falling below 10 kts by Thursday afternoon.
This high pressure remains over the waters through Saturday, with winds remaining mainly below 10 kts through this period, though inland daytime heating will drive the diurnal strengthening of the pressure gradient, allowing winds to increase to 15-20 kts along the nearshore waters. Seas of 4-6 kts Thursday morning will decrease below 5 kts by the afternoon, continuing through Saturday. -HEC

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