textproduct: Pendleton

KEY MESSAGES

1. Dry and warm conditions will persist through the week

2. Breezy to windy through the gaps Sunday

3. Pattern shift midweek will bring cooler temperatures and chances of mountain showers and thunderstorms

DISCUSSION

Current satellite shows some high clouds lingering over central an north central OR. Otherwise, clear skies everywhere else. Even with the lack of cloud cover, overnight temperatures will continue to be 5 degrees above seasonal normal with temperatures in the upper 40s across much of the region with some isolated 30s (80-90% confidence).

Models show the upper level ridge to remain parked over the region. This will keep the area under dry and warm conditions. Models show Tuesday will be the warmest day of the period. In house comparison tools show that temperatures will be upwards of 5 to 10 degrees above normal increasing to 10-20 degrees above seasonal normal by Tuesday. Saturday and Sunday HREF shows temperatures to be in the upper 70s to low 80s with 80-90% of the HREF raw ensembles in agreement. Moving into Monday, NBM raw ensembles show there to be 80- 90% confidence in temperatures remaining in the upper 70s to low 80s across the region again. By Tuesday, ECMWF and GFS ensembles as well as NBM ensembles all show 80-90% probabilities of temperatures in the mid to upper 80s with isolated locations in central OR and the Basin seeing u to near 91 degrees. This is 20-25 degrees above seasonal normal.

An upper level shortwave will make its way across the forecast area again Sunday with models showing another day of breezy to windy conditions through the mountain gaps. 60-80% of the NBM raw ensembles show Kittitas Valley and the Gorge seeing sustained winds between 20-30 mph with gusts of 40-45 mph Sunday starting after 2 PM and persisting through 9 PM. After the front passes, winds will turn to typical diurnal winds under the ridge.

Lastly, a shift in the pattern midweek will lead to chances of mountain showers and thunderstorms. Models show an upper level system making its way on shore. Cluster ensembles show there to be a bit of a timing and positing variance within the models. GFS has the system coming in as a cutoff low to the south of the region while the ECMWF and Canadian models have it coming in as a nit of a deeper trough and over the area. Each scenario will lead to the breakdown of the ridge and southwest winds aloft that will bring in warm air advection. This will increase the chances of orographic precipitation as well as thunderstorms. As of now, models are showing 20-25% probabilities of thunderstorms over the OR Cascade Wednesday before shifting to the eastern mountains and into Wallowa County. NBM raw ensembles also show there is a 20-30% probability of rain showers as well. Temperatures are also expected to decrease by nearly 5 to 10 degrees as the system moves overhead. With the uncertainty of the models and ensembles, confidence in the outcome is low (20-30%). 90

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

VFR conditions with light diurnally driven winds (less than 12kts) to prevail through the period. Lawhorn/82

FIRE WEATHER

Continued high pressure over the region has kept the region dry an warm. These conditions will remain through midweek. Models show a breakdown in the ridge Tuesday which will lead to increased instability across the area. Breezy conditions will return Sunday with Kittitas Valley and the Gorge seeing winds of 20-30 mph and gusts between 40-45 with 60-80% confidence. Tuesday is expected to be the driest day with widespread RHs in the teens to low 20s with areas in central OR seeing single digits.

Preliminary Point Temps/PoPs

PDT 76 48 78 46 / 0 0 0 0 ALW 76 51 79 50 / 0 0 0 0 PSC 80 50 84 50 / 0 0 0 0 YKM 80 51 83 46 / 0 0 0 0 HRI 80 49 82 48 / 0 0 0 0 ELN 76 48 75 43 / 0 0 0 0 RDM 83 45 81 38 / 0 0 0 0 LGD 76 44 84 43 / 0 0 0 0 GCD 80 43 89 43 / 0 0 0 0 DLS 83 53 77 48 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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