textproduct: Pendleton

KEY MESSAGES

- Cold air mass expected to move through the area this weekend and next week

- Breezy conditions this weekend along the Eastern Oregon Cascades, Washington Cascades, Lower Columbia Basin and Yakima Valley

- Return of mostly dry conditions, light winds, and above normal temperatures middle of next week

DISCUSSION

Saturday through Monday: An upper-level trough with a closed low is forecast to track southeastward over the PacNW bringing a stream of cold, dry air into the region this morning and through the weekend (confidence 99%). Per probabilistic guidance of the GFS, GEPS, and ECMWF ensemble guidance, analyzing the 700 and 850 mb frontogenesis, a pronounced cold air advection is forecast to move over the area this morning through the weekend into next week bringing near sub-freezing temperatures for Central Oregon and Wallowa Valley (confidence 85%). Currently, freeze warnings are in effect for those areas. Colder air is expected to remain over the area through the weekend into early next week. Breezy conditions are forecast for Sunday afternoon as this system and cold air advection progresses through bringing gusts up to 25-40 mph along the Cascades, Lower Columbia Basin and Yakima Valley (confidence 55%).

As this system pushes through the area this weekend and remains relatively stagnant over our forecast area, most of the region will see cooler than normal temperatures. Due to relatively low cloud cover and light north-northwesterly winds, Sunday and Monday morning have the potential to see sub-freezing temperatures in the low 20s. Lower elevation areas in the area are forecast to see temperatures in the mid 20s and mid 30s (confidence 85%). Ames/01

Tuesday through Friday: Mostly dry conditions and above normal temperatures will redevelop Tuesday through the remainder of the work week (confidence 55-85%). Ensemble cluster guidance favors upper level ridging building sliding into the region as the upper closed over the Great Basin pushes east. Tuesday into Wednesday, a weak shortwave will track through BC and clip the WA Cascades with isolated light showers (confidence 60-70%). That said, about 20% of ensemble cluster members depict a stronger shortwave passage that will bring isolated showers to the northern Blue mountains/foothills and Wallowas Tuesday night into Wednesday.

Thursday and Friday, upper level ridging will slowly move east across the PacNW while it amplifies poleward (confidence 55-65%). This will result in dry conditions and afternoon temperatures in the lower to mid 70s across much of the forecast area by Friday afternoon. Behind the upper ridge, ensemble guidance does depict upper level troughing developing in the northeast Pacific that will slowly approach the region then slowly move inland next weekend with the next potential round of unsettled weather (confidence 40-55%). Lawhorn/82

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

VFR conditions are expected at all TAF sites through this TAF period. DLS can expect to see gusts up to 23 kts later in the morning to afternoon hours, otherwise winds will generally be light through the period with winds 12 kts or less at other sites. VIS is expected to be 6SM, while CIGS are expected to be 3500 ft or greater at all sites. 82/01

Preliminary Point Temps/PoPs

PDT 58 32 56 33 / 0 0 10 0 ALW 58 36 57 36 / 0 0 10 0 PSC 63 35 62 35 / 0 0 0 0 YKM 61 38 60 34 / 0 20 0 0 HRI 61 34 60 34 / 0 0 10 0 ELN 55 31 56 29 / 20 30 0 0 RDM 54 23 50 22 / 0 0 10 0 LGD 54 30 51 30 / 0 0 10 10 GCD 54 27 51 28 / 0 0 0 10 DLS 62 39 64 37 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...Freeze Warning until 10 AM PDT this morning for ORZ050-511.