textproduct: Pendleton

KEY MESSAGES

- Above-normal temperatures and mostly dry conditions through this week into next week

- Periods of low relative humidity (10-20 percent) coupled with breezy to windy westerly winds Thursday and Friday through the Cascade gaps and across the Columbia Basin and Blue Mountain foothills

DISCUSSION

Breezy conditions are forecast to continue Thursday as a shortwave exits to the east over the Rockies and upper-level ridging rebuilds over the Pacific Northwest. Relative to Wednesday, a drier air mass (ensemble-advertised PWATs of 0.25-0.50") is forecast to be present in the wake of the shortwave, and areas of low relative humidity (10-20 percent) are forecast. Fuels are not yet ready for Red Flag Warnings, so no fire weather headlines have been issued.

By Friday, ensemble mean 500-hPa heights and vorticity show another shortwave from the Pacific tracking across the Pacific Northwest from late morning to the evening. Confidence is very high (90 percent) in another round of widespread breezy to windy westerly winds through the Cascade gaps and across the Columbia Basin and Blue Mountain foothills. NBM probabilities of reaching or exceeding advisory-level wind gusts are medium-high (40-80 percent) for wind-prone areas within the region outlined above. Similar to today, the dry air mass coupled with sufficient downward mixing during the daytime should facilitate areas of low relative humidity (10-20 percent).

Taking a glance at the weekend into the middle of next week, ensemble NWP guidance shows little to no signal for organized precipitation through Wednesday as upper-level ridging remains the favored scenario for the bulk of the West. Breezy westerly winds are likely (70 percent confidence) Sunday as the ridge axis shifts inland and ensemble guidance shows potential for yet another shortwave to ride over the top of the ridge. By Tuesday, pattern details are a bit unclear based on scenarios presented in ensemble clusters, but above-normal heights are strongly favored (at least 90 percent of ensemble members) through Wednesday.

To briefly touch on forecast temperatures, for most of our population centers high temperatures in the upper 70s to upper 80s coupled with lows in the upper 40s to lower 60s will present predominantly Minor (level 1 of 4) HeatRisk. This level of heat primarily affects those who are extremely sensitive to heat and without cooling/hydration.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

VFR conditions to prevail through the period. Breezy winds 12-17kts with gusts to 25kts will continue at sites DLS/PDT into the late afternoon and early evening, while winds will increase around 21Z at sites RDM/BDN and persist into the evening. Breezy winds will remain at site DLS overnight, with light winds prevailing elsewhere. Lawhorn/82

FIRE WEATHER

Areas of low (10-20 percent) relative humidity are forecast to accompany breezy (Thursday) to windy (Friday) westerly winds across the Columbia Basin and surrounding lowlands. Poor to moderate overnight relative humidity recovery is anticipated Thursday night for ridgetop, mid-slope, and some basin locations. Above-normal temperatures are forecast for the next week, and significant precipitation is unlikely (90 percent confidence).

HYDROLOGY

The Naches River near Naches is forecast to remain above action stage for the next week. Above-normal temperatures are forecast to continue, and significant precipitation is unlikely (90 percent confidence) for the next week.

Preliminary Point Temps/PoPs

PDT 76 49 75 47 / 0 0 0 0 ALW 76 52 75 50 / 0 0 0 0 PSC 82 54 82 49 / 0 0 0 0 YKM 83 50 79 45 / 0 0 0 0 HRI 79 52 77 48 / 0 0 0 0 ELN 77 46 70 42 / 0 0 0 0 RDM 80 41 76 38 / 0 0 0 0 LGD 75 42 73 41 / 0 0 0 0 GCD 78 43 76 41 / 0 0 0 0 DLS 79 49 75 48 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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