textproduct: Pendleton

KEY MESSAGES

1. Ridge of high pressure overhead will keep temperatures above seasonal normal through Wednesday

2. An upper level low approaching the region will bring increased winds Wednesday increasing fire weather concerns.

DISCUSSION

Current night time satellite shows little to no cloud cover over the region. Looking at overnight temperatures to be inn the upper 50s to low 60s through the Basin, Gorge and along the foothills of the Blues. Elsewhere will see low 50s.

Models show a ridge of high pressure building over the region today and persisting through early Wednesday bringing with it dry and above seasonal average temperatures. Looking at in house calculations, temperatures are expected to be anywhere from 5 to 10 degrees above seasonal average today, increasing to near 15 degrees tomorrow and Wednesday. Looking at HeatRisk probabilities, Tuesday?wednesday will be the peak with 70-80% probabilities of areas reaching Moderate HeatRisk (level 2 of 4) across the Columbia Basin and Central OR. There is also a low to medium risk of areas in the Columbia Basin seeing Major HeatRisk (3 of 4) with 20-40% probabilities. Moderate HeatRisk affects those who are sensitive to heat, especially those without cooling/hydration, while Major HeatRisk affects anyone without cooling/hydration.

Wednesday models show the upper level low off the coast of the PacNW begin to push its way onshore. By Wednesday afternoon, models show the leading edge of the low beginning to move towards the Cascades. As the leading edge of the low approaches the Cascades, short term deterministic models show a tightening of the pressure gradients along the crests. Looking at raw ensembles, there is 60-80% confidence for winds of 15-25 mph with gusts to 35 mph possible through the Columbia River Gorge, Kittitas Valley and along the foothills of the Blue Mountains.

With the increased winds and NBM showing relative humidities being in the teens to low 20% across the region, there is elevated to locally critical fire weather concerns that could develop across the lower elevations zones (65-75%).

Thursday onwards, models show the upper level low to continue to persist just to the west of the Cascades bringing persistent southwesterly flow to the region. This will keep the region under dry and breezy conditions.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

VFR conditions to prevail through the period. Low confidence (15-20%) in smoke impacts at sites, but have included HZ FU at sites ALW/PDT due to proximity to area wildfires. Winds will be light, 12kts or less, through the period. Lawhorn/82

FIRE WEATHER

Fire weather concerns are moderate through the forecast period as only relative humidity is low with no winds. The next day of concern for elevated to locally critical fire weather concerns will be Wednesday as an upper level low brings increased winds of 15-25 mph winds and gusts to 35 mph with relative humidities in the teens to low 20s.

Preliminary Point Temps/PoPs

PDT 91 55 94 59 / 0 0 0 0 ALW 93 62 95 66 / 0 0 0 0 PSC 93 57 96 61 / 0 0 0 0 YKM 90 61 95 63 / 0 0 0 0 HRI 92 58 95 63 / 0 0 0 0 ELN 86 57 93 61 / 0 0 0 0 RDM 91 50 94 50 / 0 0 0 0 LGD 93 56 98 58 / 0 0 20 20 GCD 95 57 96 58 / 0 0 10 10 DLS 93 65 95 65 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Air Quality Alert until noon PDT Wednesday for WAZ026-028>030- 522-523. OR...Air Quality Alert until noon PDT Wednesday for ORZ044-502-503- 507.