textproduct: Pendleton

KEY MESSAGES

- Chances of showers and thunderstorms will continue today, albeit chances are not as great as yesterday.

- A secondary system will continue the experienced wet pattern, with a short dry break on Tuesday.

- Cooling trend continues for the next few days, bringing temperatures 5-10 degrees below seasonal average.

DISCUSSION

The upper level low that is associated with the unsettled weather pattern is at/near the northern California coast, continuing the wet pattern we've experienced the past few days. Overnight radar shows light pop-up showers through the Columbia Basin with a more widespread band area just southeast of the region in the Baker City area. Guidance continues to show a large swath of precipitation will continue to move north into the region, increasing PoP chances across the region by 50-70% Sunday going into Monday. This will be a more rain dominated system, with light to moderate snow falling in the Cascade crest, and parts of the Southern Blues.

Chances of thunderstorms will be greatest in the eastern part of the region, specifically in the Wallowas in the afternoon to late afternoon hours Sunday. While there's enough CAPE (250-500 J/kg) is available, sufficient heating is less compared to yesterday and HREF ensemble paintballs don't support widespread thunderstorm activity. Thus, thunderstorm chances were capped at 15-20 percent chances to account for uncertainty in widespread development. Any convection chances will drop out going into Tuesday as we go into a quick dry break.

NBM clusters are in great agreement that the trough will pass by Monday, allowing a weak ridge to bring zonal flow into the area. Afterwards, general consensus will bring a trough from the British Columbia/Gulf of Alaska region down into the PacNW late Tuesday/early Wednesday. Looking at clusters for the Tuesday evening timeframe, 100% of members keeps the Basin/Blue Mountains dry, but 75% want to introduce light to moderate snow fall rates into the Washington Cascades.

Clusters are remaining in good agreement with the second trough will continue to bring moderate snow falls to the Cascades and Northern Blue Mountains along with light rain across the valley through Wednesday. Snow total via the NBM advertise 7-10" of snow in Snoqualmie and other general passes, while displaying 5-8" in Northern Blue Mountains. Chances of issuing an advisory in parts of the Cascades and Northern Blue Mountains increase, but will be reassessed over the next 24-hours.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

A band of precipitation is likely (60-80 percent chance) to bring light rain to RDM/BDN/PDT/ALW today into tonight with lower (30-50 percent) chances at DLS/PSC/YKM. Within the band, sub-VFR CIGs/VSBYs will be possible, but confidence in occurrence was too low (less than 50 percent) to include a mention in the 18Z TAFs.

Winds will increase in magnitude from the west this afternoon and persist through the period at climatologically windy locations such as PDT and DLS.

Preliminary Point Temps/PoPs

PDT 59 44 59 37 / 80 80 40 0 ALW 61 46 59 41 / 80 80 50 10 PSC 69 48 67 41 / 30 50 10 0 YKM 69 43 64 36 / 30 30 0 0 HRI 64 46 63 39 / 60 60 10 0 ELN 65 42 56 36 / 20 20 0 0 RDM 53 34 54 28 / 70 50 10 0 LGD 55 40 53 34 / 100 100 80 20 GCD 51 37 51 31 / 100 100 80 10 DLS 63 46 60 41 / 50 30 10 0

PDT WATCHES/WARNINGS/ADVISORIES

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