textproduct: Pendleton

KEY MESSAGES

1. Dry and warm conditions will persist through the weekend

2. Breezy to windy through the gaps Saturday and again Monday

3. Pattern shift Monday will bring chances mountain showers becoming more widespread Tuesday onwards

DISCUSSION

Current satellite shows mostly clear skies over the vast majority of the region with some fair weather cumulus accumulating over the ridgelines of some of the mountains. Today will be the hottest day of the week with 80-90% of the NBM raw ensembles showing the majority of the region in the low to mid 80s with pockets of high 80s in the Basin. By Sunday temperatures will be in the upper 70s low 80s with 70-90% probabilities. In office difference calculations from climate shows temperatures to be 10-15 degrees above normal by today and Sunday.

As mentioned above, the breakdown of the ridge from northwest flow to westerly flow will cause a slight increase in the winds, especially through the mountains gap areas. With the westerly or zonal flow, winds will be breezy with models showing sustained winds speeds nearing 20 mph with gusts near 30 mph with 80-90% of the NBM raw ensembles in agreement. The locations of the winds will primarily be through the mountain gaps of the Gorge and Kittitas Valley with 50-70% in agreement that the southern foothills of the Blues will see these winds as well. There will be a brief settling of the wind ahead of the next system that will be rolling through on Monday. Winds will then shift to the southwest as the upper level trough/low makes its way into the region. As the front moves inland, models and in house calculations show a tightening of the pressure gradients at the surface across the Cascades. This will bring increased winds back to the region leaning more towards windy conditions on Monday through the Gorge, Kittitas Valley and the southern Blue foothills. NBM raw ensembles are again in 60-80% agreement of sustained winds of 25-35 mph with gusts of 45-50 mph. Will be keeping an eye on the winds to watch for the need of a possible advisory for those areas.

Mondays cold front will bring cooler temperatures and precipitation with Tuesday being the coolest day of the period. In house calculations show temperatures will drop to nearly 10-15 degrees below seasonal averages with the NBM ensembles showing temperatures in the upper 50s to low 60s with a few isolated Basin locations seeing near 70s with high confidence of 70-90%. Precipitation is expected to return to the Cascades Monday afternoon with 0.05 inches of rain possible over the 24 hours with 70-80% confidence. Models show the rain to become more widespread Tuesday with precipitation expected across a vast majority of the region. Tuesdays 24 hour rain total are near 0.05 inches in the mountains with 70-80% confidence on 0.01-0.03 for some of the lower elevations. As the system steadily moves southeast, rain amounts will slightly decrease to 0.01-0.03 inches with 60-80% confidence and steadily decrease thereafter with mainly light showers expected through the remainder of the week.

Models are in agreement with the system moving through. Looking at the clusters, the biggest difference between the models is where the low will go. Many models show the upper level system to cutoff and move to the south of the region. This will lead to wrap around precipitation as well as the potential for isolated thunderstorms beginning as early as Tuesday. Other models show the upper level cut off low tracking northeast only clipping the eastern portion of the region. Regardless, NBM 12 hr probabilities of thunder show 20% probabilities of thunderstorms along the OR Cascades, Cascade foothills and across central OR into the Ochco-John Day highlands Tuesday. By Wednesday the chance drop to 15% probabilities and shift mainly over the eastern mountains and portions of Wallowa.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

VFR conditions currently at all sites, which will stay the course through the period. Breezy 20-30 kt wind gusts are occurring at KDLS, which will continue into the overnight period. Winds will also increase at KPDT/KRDM/KBDN this evening as a system approaches with gusts of 15-25kts likely. 25kft ceilings will persist, clearing behind the system by mid-morning. 75

FIRE WEATHER

Dry and warm zonal flow through Sunday and then southwest flow Monday as an upper level trough/low moves into the region. Daytime RHs will be at their lowest over weekend with the lowest RHs will be Sunday with widespread teens and low 20%. RHs tomorrow will be in the low to mid teens through central or and the Ochco-John Day highland with pockets along the southern Blues and in the Basin. Sunday is the highest day of concern, especially in the Kittitas Valley where RHs will be in the low to mid 20% and winds will be between 15-25 mph as well as the Basin with 15-20 mph winds. This puts this area of the region in elevated fire weather concerns where the overall fire environment suggests a moderate high risk for significant fires (5-19% probabilities).

Preliminary Point Temps/PoPs

PDT 50 82 50 82 / 0 0 0 0 ALW 55 81 56 84 / 0 0 0 0 PSC 52 86 53 85 / 0 0 0 0 YKM 50 85 52 77 / 0 0 0 0 HRI 53 84 52 83 / 0 0 0 0 ELN 48 76 48 72 / 0 0 0 0 RDM 41 83 44 80 / 0 0 0 0 LGD 46 82 47 86 / 0 0 0 10 GCD 43 84 45 88 / 0 0 0 0 DLS 53 82 53 77 / 0 0 0 10

PDT WATCHES/WARNINGS/ADVISORIES

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