Marine Weather and Tide Forecast for Elgin, OR

DISCUSSION
Satellite imagery shows an upper-level low over the Pacific Northwest, with a distinct low-pressure center over northwest Oregon. Through evening, the low will track inland and weaken into an open wave trough. At the surface, daytime heating coupled with partial clearing has facilitated steepening low- level (0-3 km) lapse rates -- steepest of which are in excess of 8.5 C/km per latest SPC Mesoanalysis. Meanwhile, aloft, cooling temperatures behind this morning's cold frontal passage have led to steepening mid-level (700-500 mb) lapse rates (6.5-7.5 C/km). Radar shows showers over the Blue Mountains and their foothills, and while most convection has been shallow (15 kft or lower echo tops), a couple cells have managed to extend upward of 20-25 kft and exhibited stronger cores (45-50 dBz).
Have only observed one lightning strike (western Grant County), but chances of thunder (5-15 percent) will remain present through evening across the majority of our forecast area.

Breezy to windy southwesterly to northwesterly winds will persist this afternoon through Thursday as steeper lapse rates enable stronger winds aloft to mix to the surface. Have not issued any wind headlines for today or tomorrow due to medium (40-70 percent) confidence in meeting advisory criteria (sustained winds of 30-39 mph and/or gusts of 45 mph or greater)
over widespread areas of the Columbia Gorge/Basin, Blue Mountain foothills, and Kittitas Valley. That said, have seen isolated gusts of 45-50 mph along US 97 in north- central Oregon this afternoon. Thinking some of these winds may be associated with mountain wave activity to the lee of the Cascades, and do not have sufficient confidence in duration and spatial extent to justify an advisory so have handled with a Special Weather Statement for now.

Snow showers are forecast to continue (70-95 percent chance)
across the mountains through Thursday. Have extended the existing Winter Weather Advisory for the East Slopes of the Oregon Cascades above 4500 feet through 4 AM PST Thursday morning due to anticipated shower activity during near- or sub- freezing temperatures. Confidence is medium (60 percent) in an additional 6 inches of snowfall for the Cascade crest in the vicinity of Santiam Pass.

Farther east, have issued a new Winter Weather Advisory for the Northern Blue Mountains of Oregon and Northwest Blue Mountains (Washington), valid 7 PM PST this evening through 10 PM PST Thursday. Confidence is medium-high (50-90 percent) in reaching or exceeding 6 inches of snowfall above 4000 feet for the northern Blues, with lower confidence (20-50 percent) in reaching or exceeding 12 inches of snowfall in heavier snow showers.

Confidence in forecast details becomes a bit more shaky by Thursday night and Friday. Some high-resolution NWP guidance is suggesting another round of near-advisory mountain snow accompanied by lowland rain as a warm front moves through, but the majority of ensemble members indicate only light mountain snowfall and lowland rain; the forecast currently reflects the more likely latter scenario.

Periods of precipitation, breezy winds, and above-normal temperatures are then forecast through the weekend as ensemble guidance shows a nearly zonal 500-mb pattern persisting. 86

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
VFR conditions are expected through the TAF period. Te main story will be gusty winds, which should decrease at all sites expect PDT overnight then increase again on Thursday to the 20 to 30 kt range before decreasing after sunset.

There is a chance (generally less than 30 percent) of -RA at PDT and ALW into Thursday, so did not include in the TAFs. All other sites shave even lower probabilities.

Preliminary Point Temps/PoPs
PDT 37 51 34 53 / 60 30 20 30 ALW 38 52 37 53 / 80 40 30 30 PSC 38 58 36 59 / 30 10 10 10 YKM 34 54 34 57 / 10 0 10 10 HRI 39 56 37 58 / 30 10 10 20 ELN 35 47 34 52 / 20 10 10 10 RDM 30 45 28 50 / 30 10 10 10 LGD 35 44 30 48 / 100 60 50 40 GCD 32 42 29 46 / 70 50 30 40 DLS 41 53 41 55 / 40 30 30 40

PDT WATCHES/WARNINGS/ADVISORIES
WA...Winter Weather Advisory until 10 PM PST Thursday for WAZ030.
OR...Winter Weather Advisory until 10 PM PST Thursday for ORZ502.
Winter Weather Advisory until 4 AM PST Thursday for ORZ509.