textproduct: Pendleton

KEY MESSAGES

- Ridging continues to promote warm and dry conditions through the next couple of days.

- Weather system pushes through mid-week, enabling slight chances (15-25%) of thunderstorms across the Wallowas and parts of the Blue Mountains, wetting rains, and breezy winds.

- Uncertainty with the pattern through the weekend going into early next week.

DISCUSSION

Satellite shows mid to upper level broken to overcast skies across the region with light radar returns not reaching the ground. Surrounding soundings from Spokane and Medford recorded mid-level dry air, evaporating any precipitation before it has a chance to reach the surface. Upper level ridging will continue to influence the synoptic pattern, allowing max temperatures to climb up to 10-15 degrees above seasonal average across the region. Current guidance suggests high temperatures will reach the upper 60s to low 70s by Wednesday (70-80% chance) as the ridge continues to travel east. Winds in the short term with the upper ridge will be light in general with standard diurnal cycles.

A low pressure system associated with a trough currently resides just off in the Pacific moving in a south/south south-west motion, which will continue until sometime late Tuesday through mid Wednesday. Guidance is in good agreement that the cut-off low will then move onshore into California bringing wrap around precipitation into the region with PoP's up to 30-70% through Thursday and into early Friday. Heavier/greater chances of that range will be mostly in the Wallowa's and parts of the Southern Blues down into Central Oregon. Current NBM estimates advertise up to a tenth of an inch of rain in the Foothills of the Blues and gradually increases up to a half inch when you get into the Eastern Mountains (50-70% chance for all QPF's). Confidence is only medium with the widespread of 6-hour 25th-75th percentiles across the area due to the .15-.25 inch differences between the quartiles. Confidence is high (70-90% chance) we see wetting rains (>.1") over a 24-hour period in some locations along the eastern mountains, Grand Ronde Valley, and parts of the John Day Basin through Friday.

Up to 150-200 J/kg of CAPE will develop Thursday across Wallowa and parts of the Southern Blues bringing slight thunderstorm potential (15-25% chance). Storms are not expected to last long and be more pulsey with no severe weather expected. A cold front will bring tight pressure gradients across the region Thursday and Friday, enabling breezy to locally windy conditions to occur across most of the region. NBM advertises 50-80% chances of wind gusts 30 mph or greater across much of the region (except for Central Oregon). Upping the threshold to 45 mph or greater (wind advisory criteria) lowers the chances exclusive to the Dalles and the Cascade gaps at 20-40%. Overall, not too concerned for wind advisories as of yet, but will see how this evolving forecast changes and will see if highlights are needed later this week.

Another shortwave is expected to move down from British Colombia down into the PacNW (70-80% chance) with uncertainty with how clusters handle the shortwave. In fact, 29% of clusters want to bring ridging over the area with area wide dry conditions by Sunday. On the flip side, 54% close the low and bring chances (30-40%) of moderate to heavy snow in the Cascades. Still a while to monitor but the potential for some impacts is possible as we head closer to the weekend. Stay tuned!

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

VFR conditions and predominantly light, diurnally and terrain- driven winds of 10 kts or less are expected (95% confidence or higher) through the period. There is a low chance (30% or less) of light rain at BDN/RDM through this evening, with even lower chances (20% or less) elsewhere.

Preliminary Point Temps/PoPs

PDT 36 63 36 67 / 0 0 0 0 ALW 41 64 43 67 / 0 0 0 0 PSC 36 68 36 68 / 0 0 0 0 YKM 40 70 40 70 / 0 0 0 0 HRI 36 66 35 67 / 0 0 0 0 ELN 36 67 38 68 / 0 0 0 0 RDM 29 62 27 70 / 10 0 0 0 LGD 36 70 39 74 / 0 0 0 0 GCD 38 72 40 75 / 0 0 0 10 DLS 44 71 42 73 / 10 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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