Marine Weather and Tide Forecast for Milton-Freewater, OR

DISCUSSION
Isolated snow showers across the Cascade and Blue mountains will taper off this evening as weak instability wanes. Breezy to locally windy westerly winds will continue through this afternoon. Most areas have remained below advisory thresholds so the Wind Advisories that were in effect earlier today were cancelled. That said, particularly wind-prone areas have, and likely (80 percent confidence) will reach advisory thresholds this afternoon.

Overnight through Friday, another round of light precipitation is forecast as a surge of moisture arrives from the Pacific.
Ensemble NWP guidance yields high confidence (80 percent) in light rain amounts of a trace to a quarter inch for the lowlands, with snowfall amounts ranging from a trace to a few inches for the mountains. Advection of warmer air into the region will push snow levels above mountain passes by Friday morning (Cascades) through Friday evening (Blues).

The 500-mb pattern is then expected to turn zonal over the weekend into next week. Precipitation chances taper off Saturday east of the Cascade crest, but a moist zonal jet will keep at least a chance (30-50 percent) of precipitation along the Cascades through Sunday morning.

By late Sunday, clusters of like-solutioned ensemble members all indicate a return to a more active weather pattern to the forecast area. That said, there is still significant uncertainty in pattern details. We are currently keeping a watch on potential widespread windy conditions for the lowlands and advisory- or warning-level mountain snowfall for the Washington Cascades. The NBM indicates high (75-95 percent) chances of advisory-level wind gusts Sunday for the Kittitas Valley with medium (40-60 percent) chances elsewhere in the lower elevations. There is some potential (40-60 percent) for reaching High Wind Warning thresholds (50 kt wind gusts) for the Kittitas Valley as well.

Jumping forward in time to Tuesday through Wednesday, the ECMWF EFI is signaling decent ensemble agreement (EFI values of 0.5-0.8) for anomalous precipitation and snowfall relative to model climatology for the Cascades and their adjacent eastern slopes as well as the northern Blues. Shift of Tails (SoT)
values of 2 show some members are forecasting an extreme solution.

Taking a look at probabilities of snowfall amounts from the NBM for the 48-hr period ending 00Z Thursday, there is a 10-30 percent chance of reaching or exceeding 1 inch of snowfall for the Kittitas and Grande Ronde valleys, with lower chances (up to 10 percent) for the Blue Mountain foothills. The Oregon Cascade passes have a medium-high (50-70 percent) chance of reaching or exceeding 6 inches of snowfall, while the Washington Cascades have a high (80-95 percent) chance and the northern Blue Mountains have a low-medium chance (20-60 percent). 86

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
VFR conditions continue to prevail with mostly dry weather persisting. Conditions may (30 percent confidence) deteriorate to MVFR in BDN/RDM during the later morning hours tomorrow.
Confidence is a bit low on impacts, so kept it at PROB30 for now, but will adjust later on based on guidance later today.
Winds will remain breezy to locally windy through the rest of the afternoon and evening hours. Winds will decrease to 10-15 knots heading into the morning and afternoon tomorrow.

Preliminary Point Temps/PoPs
PDT 34 54 44 63 / 10 40 30 10 ALW 37 53 45 62 / 20 30 50 20 PSC 37 59 45 66 / 0 40 20 0 YKM 35 57 41 63 / 10 10 20 0 HRI 37 58 45 65 / 0 40 20 0 ELN 34 51 42 57 / 10 20 30 0 RDM 26 50 34 62 / 0 20 10 0 LGD 32 48 40 59 / 40 40 50 20 GCD 29 46 38 58 / 20 40 30 20 DLS 41 55 46 62 / 20 50 40 10

PDT WATCHES/WARNINGS/ADVISORIES
WA...None.
OR...None.