Marine Weather and Tide Forecast for Altoona, WA

SHORT TERM
Now through Tuesday Night...Weak onshore flow through the next few days with a few shortwave troughs moving within the flow. Tonight the first shortwave will arrive which will bring a slight chance (15-30% chance) of rain - especially along the coast. Forecast simulated reflectivity shows very showery conditions so some areas may receive accumulating precipitation while others will be rain free. Accumulation will be minimal, though higher terrain along the coast will see the most with up to 0.2 inch possible. Due to a slight rain shadow effect, inland areas will stay drier.

Seasonable temperatures and partly cloudy skies. With westerly flow through the column, there will be minimal change in the overall forecast. Temperatures will remain in the 70s inland, while in the upper 50s to mid-60s along the coast. Will see highs increase by a degree or two on Tuesday, but clouds through the day may dampen those temperatures slightly.

The second shortwave arrives on Tuesday night into Wednesday which increases chance for rain once again. More details to follow. -Muessle

LONG TERM
Wednesday through Sunday...ECMWF and GFS Ensemble guidance are both in agreement that there is potential for shortwave- troughing on Wednesday. Following this trough, a stronger area of low pressure brings in heavy showers Friday through the weekend. Onshore flow will increase as pressure gradients tighten with the introduction of troughing onshore.
Increasing winds, decreasing temperatures, and heavy showers will increase the probability for 0.25 inch of rain or more each day. Based on NBM ensemble guidance there is strong agreement that the probability for 0.25" of rain or more within a 24-hour period over the weekend is 40-50%, while the Coast, Coastal Range, and Cascades is 65-75%. Given the showery nature of this system, cannot rule out thunderstorms. There is currently a 15-20% chance of thunderstorms on Friday and Saturday, with the highest probability on Friday being in the Willamette Valley, and Saturday focuses on the Cascades. The initial shortwave trough will only drop maximum temperatures in the Willamette Valley about 5 degrees F, bringing temperatures from low-80s to mid-70s. Temperatures fall even farther as the stronger low pressure moves in. Highs along the Willamette valley will range from near 60s degrees F in the south Valley, to the mid-70s in the north Valley. The coast will remain "normal" in the high 50s/low 60s. -Ruhl/Muessle



AVIATION
Currently VFR conditions and clear skies, expected to continue through the TAF period for inland terminals. For coastal terminals, CIGs will likely deteriorate to MVFR around 09Z Tuesday (with probabilities around 30-60%, highest to the north and lowest to the south). Expect west to northwesterly winds around 5-10 kt this evening, becoming light and southwesterly by 06-09Z Tuesday.

*KTTD ASOS is currently INOP except for altimeter and will be AMD NOT SKED.

PDX AND APPROACHES...VFR conditions continue through the TAF period. Northwest winds around 5-10 kt by the afternoon, then becoming light and southwesterly around 09-10Z Tuesday.
-Hall

MARINE
A weak disturbance is expected to cross the region this evening, supporting a wind shift from northwesterly flow to southerly flow late this evening and through Tuesday. A westerly swell is also expected to move into the waters this evening, increasing seas from around 3 feet to around 6 ft at 10 seconds.
Combined seas still look to remain 7 ft or less through the week.
Winds remain southerly through Tuesday, gradually turning back to the west/northwest on Wednesday. Another disturbance arrives Monday, bringing mostly westerly winds through the weekend.
-Hall/Batz

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