textproduct: Pendleton

KEY MESSAGES

1. Drier and cooler temperatures through the weekend

2. Freeze Warning for Saturday morning

3. Mountain precipitation returns Sunday

DISCUSSION

Current radar shows the returns to have moved out pf the region and to the southeast. Ground observations show trace amounts of rainfall occurred since 5 PM. No more precipitation is expected through the the weekend until the next system moves across the region beginning Sunday.

Models are in form agreement with the upper level flow for the northwest. This pattern is brining in drier and cooler air which is leading to below average seasonal temperatures through the weekend. In house seasonal calculations show that Friday and Saturday high temperatures will be between 5 to 10 degrees below seasonal normal with some isolated 15 degrees below normal along the ridgelines. Temperatures over the weekend are expected to be in the mid 50s with some isolated locations in the Basin seeing low 60s with 70-90% of the NBM raw ensembles in agreement.

Models show the region to be influenced by colder air, coupled with dry air and clear skies, temperatures are expected to dip into very cold temperatures across the region. So much so that a freeze warning has been issued for the Kittitas Valley, lower Columbia Basin and the foothills of the northern Blue Mountains of OR and WA. Guidance shows temperatures through the aforementioned areas to be at or below freezing Saturday morning. 70-90% of the NBM raw ensembles are in agreement with these cold temperatures. In house seasonal comparisons show these areas to be 10-15 degrees below seasonal average.

Models show a shift in the pattern as an upper level low coming out of B.C. clips the region. This will bring chances of mountain precipitation Sunday with very little accumulations. By Monday, precipitation amounts will be more prevalent, especially across the eastern mountains and OR Cascades Sunday with rain amounts between 0.01-0.02 along the foothills and 0.04-0.07 along the crests with 50- 70% probabilities. Very light mountain showers will persist through Tuesday before dry and warmer temperatures make it way back into the region under an incoming upper level ridge. 90

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

VFR conditions will persist through the forecast period. Cigs will be 25kft to SKC through the period with winds below 12 kts. 90

Preliminary Point Temps/PoPs

PDT 55 31 59 34 / 0 0 0 0 ALW 57 35 60 38 / 0 0 10 0 PSC 61 31 64 35 / 0 0 0 0 YKM 61 34 63 36 / 0 0 0 0 HRI 60 31 63 34 / 0 0 0 0 ELN 56 31 58 34 / 0 0 0 0 RDM 57 24 57 27 / 0 0 0 0 LGD 51 28 55 31 / 10 0 10 0 GCD 52 28 55 30 / 0 0 10 10 DLS 63 37 66 39 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Freeze Warning from midnight tonight to 8 AM PDT Saturday for WAZ026-028-029. OR...Freeze Warning from midnight tonight to 8 AM PDT Saturday for ORZ044-507.