textproduct: Pendleton

KEY MESSAGES

- Areas of thunderstorms today through Central OR and Foothills of the Blues.

- Cooler trend continues through the week.

- Return of wetter pattern through the second half of the week.

DISCUSSION

Current radar shows shower activity from the upper level trough continuing to bring pop-up showers across the region. A few heavy showers are developing near the Kittitas region continuing to drift north, which will eventually head over into Ellensburg. As the trough continue to drift eastward, showers and thunderstorm chances will continue to be medium to high (40-70%) while thunderstorm chance (15-30%) develop along Central Oregon through the John Day Highland and Foothills of the Blues. NBM develops 250-350 J/kg of CAPE by the early afternoon Saturday with HREF paintballs supporting T-storm development in the late morning through afternoon hours. How widespread convection initiation happens remains uncertain due to the general overcast conditions that will prohibit the convection to its fullest potential. In areas of more general breaks in the clouds through the day will see the greatest chance of t-storm development and widespread erratic wind gusts from embedded storms. Regardless, heavy rain is expected for areas across Central Oregon and the John Day Highlands and, to a slightly lesser extent, the Foothills of the Blues. The strongest storms will see a slight chance (15-25% chance) of pea size hail falling.

Ensemble guidance is in good agreement that after this trough departure, the upper level pattern will turn more zonal Tuesday to give us dry weather before becoming more unsettled the following day on Wednesday. Guidance is in good agreement that a secondary trough drops from the British Columbia/Gulf of Alaska region, bringing widespread precipitation chances across the region. Things become a bit uncertain going into day 5 on Wednesday regarding snowfall amounts in the Cascade and Northern Blue Mountain region. About 30% of members brings a much weaker trough, while 49% develops a stronger trough with a wetter solution that would bring 4-7 inches of snow across the Cascades and Wallowas which would bring winter weather highlights. Regardless, there is still plenty of time to monitor for trends in the forecast and see if winter highlights are warranted.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Areas of pop up showers continue overnight that will eventually impact all sites through Sunday. PROB30 chances of thunderstorms possible, especially sites in Central OR and sites along the Foothills of the Blues. Although there's no sub-VFR conditions expected in dominant lines, the PROB30 chances include temporary MVFR/IFR conditions in the heaviest storms that will develop.

Preliminary Point Temps/PoPs

PDT 65 42 60 42 / 50 30 70 70 ALW 65 46 60 45 / 70 30 80 80 PSC 71 44 66 46 / 40 10 40 50 YKM 67 42 68 44 / 40 10 20 30 HRI 69 44 63 45 / 40 10 50 60 ELN 60 39 63 42 / 50 10 20 20 RDM 61 37 54 34 / 70 70 60 50 LGD 62 41 55 39 / 90 60 100 90 GCD 61 40 52 37 / 70 70 100 80 DLS 67 47 64 46 / 60 30 40 40

PDT WATCHES/WARNINGS/ADVISORIES

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