textproduct: Pendleton

KEY MESSAGES

- Mountain snow and lowland rains Tonight

- Mountain snow and lowland rains redeveloping Monday afternoon onto Tuesday Morning

- More Mountain snow and and lowland rains Wednesday through Friday

DISCUSSION

The Oregon Cascades should receive the most snow for Todays period into Tonight, however, largely sub advisory amounts. The NAM and other models have far higher, overdone numbers compared to the HRRR which caps out about 6 inches of snow across the higher elevations of OT509 though 8z Sunday (midnight local).

HRRR also shows show accumulations overspreading the lower elevations around the DLS however the expected snow levels do not match up with the local elevations and NBM members offer only a probabilistic 10% of snowfall of 2 inches or more Tonight across OR510. Santiam Pass has about a less than 10% chance of reaching or exceeding advisory criteria snowfall of about 5 inches through Sunday morning based on NBM and about 50% based on HREF alone. This points to relatively high confidence on lower end impacts, however slick roads should still be planned on even with as little as one inch of snow.

Snow amounts pick up again Monday afternoon through Tuesday morning, which is another target of opportunity for winter weather impacts. However the confidence for advisory level snows still remains not high, as the main NBM (expected) forecast only reaches 2-4 inches up to about 5000 ft. For this period the WSSI-P (probabilistic impacts) indicates only about a 20-40% chances for minor impacts (occasional inconveniences/winter driving conditions) for the eastern slopes of the Oregon and Washington Cascades.

NAEFS ESAT tables point toward a southward trajectory for the IVT/IWV on Tuesday across central CA which does not support a high impact snow event for the PDT area, nevertheless, a prolonged duration for snow accumulation is anticipated for the time window between Tuesday Night and and Friday where amounts could be high enough to require Winter Weather headlines.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Conditions have begun to deteriorate across the region. While some sites remain VFR, some MVFR and even LIFR at BDN and RDM have moved in. Expect further lowering overnight to MVFR/IFR at most sites and those conditions will remain through much of the day Sunday before some improvement is possible later Sunday.

Preliminary Point Temps/PoPs

PDT 36 46 35 44 / 80 40 30 70 ALW 38 46 37 45 / 90 60 40 80 PSC 37 49 35 48 / 70 20 20 60 YKM 34 45 32 44 / 40 10 10 30 HRI 37 49 35 47 / 80 20 20 60 ELN 30 41 28 39 / 20 20 10 30 RDM 29 49 30 42 / 50 10 20 50 LGD 37 51 35 47 / 80 70 40 90 GCD 34 51 34 46 / 50 20 30 70 DLS 39 48 37 45 / 70 30 20 60

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...Dense Fog Advisory until noon PST Sunday for ORZ511.