textproduct: Pendleton

KEY MESSAGES

- Light to moderate mountain showers across the WA Cascades and Northern Blues with breezy low elevation winds Tuesday

- Near to above normal temperatures throughout the week

- High uncertainty in return of light mountain showers Thursday or Friday, with better agreement of dry conditions and above normal temperatures over the weekend

DISCUSSION

Little to talk about on satellite tonight as much of the PacNW is under clear skies. At the surface, weak diurnally winds have developed, while areas of central OR and the Kittitas valley have seen temperatures drop into the 30s. If winds become calm, there is a potential for radiative cooling processes to drop temperatures to at or just below freezing tonight (confidence 30-60%).

Today through Wednesday: Dry and quiet conditions will prevail across the forecast area for much of today as zonal flow will develop over the PacNW while an upper trough drops through the Great Basin into the Desert Southwest. While winds will remain light across much of the area, winds will increase through the eastern Columbia Gorge ahead of an approaching cold front.

Monday night into Tuesday, flow aloft will remain zonal, however an upper shortwave trough passing through BC will clip the WA Cascades and northern Blue mountains. This will result in light to moderate rain showers developing across these areas, with a 35-45% chance of 0.1 inches in the Northern Blues and a 55-95% chance of 0.25 inches along portions of the WA Cascades and east slopes (highest chances in central WA Cascades, lowest south central WA Cascades). In the Columbia Basin and Gorge, a cold front passage will result in breezy west to southwest winds (15-25mph with gusts 25-40 mph) developing throughout the day, with light to locally breezy winds elsewhere.

Flat upper level ridging in the eastern Pacific will build into the western CONUS by Wednesday morning, resulting in a return to dry conditions and light winds.

Thursday through Sunday: High uncertainty amongst deterministic and ensemble guidance in the evolution of the synoptic pattern Thursday through Friday, however there is good consensus amongst the most recent ensemble members for low impacts during this period. Overall, disagreement surrounds the eventual passage of a shortwave trough that will bring light mountain showers. Ensemble members are in disagreement if the trough comes through sometime Thursday or sometime Friday, so confidence in precipitation timing/extent is very low (15-20%).

After Friday, agreement grows in upper level ridging building over the PacNW through the weekend, resulting in dry and quiet conditions with above normal temperatures. (confidence 45-60%). Lawhorn/82

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

VFR conditions to prevail through the period. Winds will increase to 12-15kts with gusts to around 22kts at site DLS this afternoon, then becoming light later in the evening and overnight. Otherwise, light diurnally driven winds will prevail at all other sites. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 70 44 75 51 / 0 0 0 0 ALW 71 51 75 55 / 0 0 0 10 PSC 75 45 77 49 / 0 0 0 0 YKM 73 46 73 48 / 0 0 0 0 HRI 74 48 76 51 / 0 0 0 0 ELN 68 43 64 44 / 0 0 20 20 RDM 71 36 75 40 / 0 0 0 0 LGD 71 39 75 47 / 0 0 0 10 GCD 72 40 76 45 / 0 0 0 0 DLS 76 48 73 53 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...None.