textproduct: Pendleton

KEY MESSAGES

- Cooler temperatures today, with warmer temperatures this week.

- Chances of isolated to scattered thunderstorms through the Blue Mountains and Eastern Mountains through mid-week.

- Elevated fire weather conditions persist due to dry lightning and potential low RH/breezy winds in other places.

DISCUSSION

Satellite shows an area of mid to high clouds across the eastern portion of the region with radar returning light echoes with general spotty light rain. Rain will continue to move east with most of the area drying out through the rest of the afternoon. A shortwave off the coast of Washington state is bringing southwest flow with marginal mid-level moisture transportation.

Going forward, a ridge situated over the lower-48 will continue to influence the synoptic pattern, along with a trough/low pressure system off-shore in the Pacific. Going through this week, monsoonal moisture transportation along with southwest flow from an offshore low will allow chances of isolated to scattered thunderstorms to develop across the Blue Mountains and Eastern Mountains (up to 30% chance). Guidance is a bit shaky with how the off-shore flow will behave Tuesday onwards, with a spread of location and intensity amongst the clusters. Wednesday guidance shows about 54% of clusters bringing in a stronger shortwave, while 11% shows a much weaker trough. Uncertainty grows more going into Thursday with 17% of members bringing stronger trough and 27% bringing in a weaker system. How close the trough gets to shore will determine the amount of precipitation and strength (or number) of thunderstorms developing through the next few days. A closer/stronger trough will bring better chances of strong thunderstorms than the opposite scenario. Current RRFS guidance advertises multiple rounds of light to moderate showers with isolated chances of thunderstorms across Central to Northeastern Oregon Tuesday, with isolated to scattered thunderstorms on Wednesday. Notably, this solution brings the low pressure system just offshore as the heavier thunderstorms develop late Wednesday afternoon.

Temperature wise, high temperatures across the Columbia Basin and Kittitas Valley will rise to low to high 90s with the ridge suppressing. Temperatures remain somewhat fluctuant regarding confidence with the position/strength of the low Thursday through the rest of the week as meteograms show box-and-whisker 25th and 75th ranging 10-20 degrees. Overall confidence points to a warming trend through at least Thursday.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

VFR conditions are forecast at all sites for the next 24 hours. There is low confidence (30% or less) in smoke from area wildfires affecting CIGs/VSBYs at BDN/RDM.

Winds will be mostly 10 kts or less, except for periodic afternoon/evening gusts, especially at DLS.

Preliminary Point Temps/PoPs

PDT 56 91 61 94 / 0 0 0 0 ALW 60 93 65 96 / 0 0 0 0 PSC 57 94 62 98 / 0 0 0 0 YKM 56 94 61 98 / 0 0 0 0 HRI 58 93 64 97 / 0 0 0 0 ELN 53 91 58 94 / 0 0 0 0 RDM 52 92 55 92 / 0 0 0 0 LGD 58 93 63 94 / 0 0 0 10 GCD 57 93 60 93 / 0 0 0 20 DLS 58 93 62 97 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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