textproduct: Pendleton

KEY MESSAGES

- Potential for near to below freezing morning lows this morning and Saturday morning

- Dry and warming trend into this weekend

- Unsettled weather returns next week, but uncertainty remains in details

DISCUSSION

Today through Sunday: Satellite imagery this early morning shows clear skies across much of the forecast area, with stratus mostly confined to the Blues and the Cascade crest. Winds have lightened across much of the region, though a few areas along the Blue mountain foothills and the Kittitas valley remain under locally breezy conditions. Areas if the forecast area are already seeing impacts from radiative cooling processes, but those under the breezy conditions are staying well mixed for the moment. Winds are expected to decrease over the next hour or so, and as good radiative cooling takes place, expect many locations in the lower elevations to see temperatures reach or go below freezing.

An upper ridge in the northeast Pacific will move over the PacNW today, reinforcing the trend in light winds and clear skies into this afternoon. As the ridge axis moves inland this afternoon, bands of cirrus will develop over the region which will persist into early Sunday.

The upper ridge over the region will push east Sunday as an upper closed low develops in the Northeast Pacific, which is advertised to set up offshore the PacNW and northern CA. There is good agreement amongst ensemble and deterministic model guidance that precip will remain west of the Cascade crest through Sunday. The only uncertainty will be if enough instability will be present under a southerly flow aloft to allow an isolated shower to develop over the OR Cascade crest Sunday afternoon (probability of ~15%).

Monday through Thursday: Uncertainty in the evolution of the upper low offshore remains through next week. There has been better agreement amongst ensemble cluster members (~65%) that the low will approach the region but remain centered offshore Monday. As the low inches further east Monday, the OR Cascades will see increasing chances of showers, but the southerly flow ahead of the low will also bring increasing instability, and therefore at least low chances (10-20%) of isolated thunderstorms to develop. Per these members, these chances may redevelop again Tuesday afternoon when the low starts inland. In the solution of the other 35% of members, any convective shower chances may diminish as these members bring the low directly over the PacNW by Tuesday afternoon.

Ensemble cluster guidance is in good agreement that unsettled weather conditions will continue late Tuesday through Thursday (confidence 60-70%). However, disagreement remains on the timing, position, and strength of the upper low as it moves across the region, resulting in low confidence (20-25%) in details of precipitation amounts/type and the strength of winds during the middle of next week. Lawhorn/82

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

VFR conditions to prevail through the period. Winds will be light, 12kts or less, and diurnally/terrain driven through the period. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 57 35 69 42 / 0 0 0 0 ALW 58 38 68 46 / 0 0 0 0 PSC 63 36 72 43 / 0 0 0 0 YKM 61 37 67 43 / 0 0 0 0 HRI 61 35 71 42 / 0 0 0 0 ELN 56 33 63 39 / 0 0 0 0 RDM 58 28 70 38 / 0 0 0 0 LGD 54 33 61 40 / 0 0 0 0 GCD 55 32 64 39 / 0 0 0 0 DLS 64 40 71 47 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Freeze Warning until 9 AM PDT this morning for WAZ026>029. OR...Freeze Warning until 9 AM PDT this morning for ORZ044-507.