textproduct: Pendleton

KEY MESSAGES

- Cold, dry air mass continues to bring near freezing morning temperature this morning into early next week

- Light rain-snow showers for the Wallowa Mountains and Southern Blue Mountains tonight into Monday morning

- Dry conditions, light winds, and above normal temperatures prevail middle of next week through Friday

DISCUSSION

Sunday through Tuesday: Cold, dry air continues to push through the area as strong northwesterly flow aloft associated with an upper-level trough digging southeastward brings near freezing temperatures to the Central Oregon,Grande Ronde Valley, and Wallowa Valley forecast zones this morning. Throughout today, afternoon temperatures should be in the mid 40s to mid 50s, with temperatures gradual cooling to near freezing overnight into Monday morning. Elsewhere, minimum temperatures will be in the mid 30s. Tonight and overnight into early Monday morning, there is a chance for light rain-snow showers (confidence 55-60%), primarily confined to the Wallowa Mountains. Lower chance (confidence 25%) for the Southern Blue Mountains.

Per model guidance of the HREF and HRRR, confidence is fairly high (confidence 80%) to see freezing temperatures Monday morning, especially for Central Oregon and Kittitas Valley as members are showing relatively clear skies and light winds early Monday morning. There is still some uncertainty in just how clear the Grande Ronde and Wallowa Valleys will see Monday morning, but winds will still be fairly light in support for freezing temperatures (confidence 50- 60%). Elsewhere, minimum morning temperatures will be in the mid 30s, low 40s.

Per probabilistic model guidance, clear skies and light winds are supportive of freezing morning temperatures Tuesday morning (60- 70%). Central Oregon, Kittitas Valley, Grande Ronde Valley, and Wallowa County zones could see temperatures in the mid 20s. As the upper-level trough/low pushes eastward out of the region, we see a return of zonal flow aloft associated with a building ridge pattern that will bring a slight warming trend for the forecast area in the afternoon, bringing temperatures back into the mid 60s, light winds, and relatively dry conditions (confidence 65-70%).

Wednesday through Saturday: Mostly dry conditions with above normal temperatures will prevail Wednesday through Friday (confidence 65-85%). Ensemble guidance continues to show an upper level low pushing east across the Rockies, allowing upper level ridging to build over western CONUS during this period. A weak shortwave is still expected to slide over the upper ridge Tuesday into Wednesday, however impacts from this system passage only amount to increasing cloud mid to upper level cloud cover over the forecast area (confidence 75-85%). Thursday and Friday, upper level ridging will slowly move east across the PacNW while it amplifies poleward (confidence 65-80%). This will result in dry conditions and afternoon temperatures in the lower to mid 70s across much of the forecast area by Friday afternoon. By Saturday, ensemble cluster guidance is in good agreement of the upper ridge axis pushing further east, allowing an upper trough to lift northeast across WA through Saturday. Confidence is moderate (60-65%) that light showers will at least develop along the WA Cascade crest/east slopes Saturday, however there is low-mod confidence (25-40%) in light showers extending along the OR Cascade crest. Lawhorn/82

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

DLS/PDT/RDM/BDN: VFR conditions to prevail through this TAF period at these sites. Winds will generally be light of 12 kts or less. CIGS and VIS remain VFR through the period. Ames/01

YKM/ALW/PSC: VFR conditions to prevail through the period at these sites. Winds will increase to 12-17kts with gusts 18-25kts at sites YKM/PSC late this morning, then becoming light by the evening hours. Winds will otherwise be light through the period. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 54 31 57 31 / 10 10 10 0 ALW 55 35 57 36 / 10 10 20 0 PSC 60 35 62 31 / 0 0 0 0 YKM 59 34 62 34 / 0 0 0 0 HRI 58 34 61 30 / 0 0 0 0 ELN 55 29 59 30 / 0 0 0 0 RDM 48 22 55 21 / 0 0 0 0 LGD 50 31 54 26 / 10 30 40 0 GCD 50 29 54 25 / 0 10 10 0 DLS 63 38 67 36 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Freeze Warning until 10 AM PDT this morning for WAZ029. Freeze Watch from this evening through Monday morning for WAZ026. OR...Freeze Warning until 10 AM PDT this morning for ORZ507.