textproduct: Pendleton

KEY MESSAGES

- Near- to below-normal temperatures through the weekend.

- Periodic showers through the week, then medium-high (40-80%) chance of precipitation for central/eastern Oregon and southeast Washington over the weekend.

DISCUSSION

Satellite imagery shows a broad low-pressure system located just west of Vancouver Island. This low is responsible for isolated showers across the forecast area, which radar reveals are predominantly confined to the mountains (especially the Cascades). Aside from some patchy dense fog in valley locations this morning, there is little else to note.

Ensemble NWP guidance is in excellent agreement that the aforementioned upper-level low will continue to churn offshore through the week, and produce low-medium (5-40%) chances of showers, mainly over the mountains and highest along the Cascade crest.

Over the weekend, the low is expected (90% confidence) to move inland. Chances of precipitation are medium-high (40-80%) across the majority of central/eastern Oregon and southeast Washington Saturday afternoon through Sunday morning. The best chance of significant precipitation will be over the northeast Blue Mountains where the NBM places a 30-60% chance of 0.25" and 10-40% chance of 0.50" of QPF.

Ensemble spread grows Sunday into Monday with regard to how quickly the low will exit to the east and upper-level ridging will build in from the Pacific. Regardless, dry conditions are forecast to return Monday, and this presents the best chance (75% or less) of a season-ending freeze for remaining eligible forecast zones.

Uncertainty in the 500-hPa pattern then grows Tuesday through the remainder of the week. Mostly dry conditions are forecast to continue until Thursday when ensemble guidance hints at the return of some more active weather.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Main aviation concerns will revolve around the potential for periods of low CIGs/VSBYs due to low stratus and/or fog this morning (DLS/RDM/BDN) and again tonight (low possibility at all sites, highest chances at RDM/BDN). Confidence is low-medium (30-50%) in timing/duration of any sub-VFR conditions. Predominantly light winds of 10 kts or less are forecast.

Preliminary Point Temps/PoPs

PDT 53 32 49 30 / 0 0 0 0 ALW 55 34 50 34 / 0 0 0 10 PSC 55 32 53 29 / 0 0 10 0 YKM 52 31 53 28 / 0 10 20 0 HRI 54 31 51 28 / 0 0 0 0 ELN 46 24 47 23 / 10 20 30 0 RDM 52 22 51 21 / 0 0 0 0 LGD 57 31 58 30 / 0 0 0 10 GCD 58 31 57 31 / 0 0 0 0 DLS 54 35 54 33 / 10 10 10 0

PDT WATCHES/WARNINGS/ADVISORIES

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