textproduct: Pendleton

KEY MESSAGES

- Chances of thunderstorms for Central Oregon Today with more widespread coverage on Thursday. Hail and gusty winds are possible embedded in these storms.

- Minor heat risk for Today, Moderate heat risk on Thursday.

- Breezy to windy conditions develop on Friday.

DISCUSSION

An upper low intermediate south of the forecast area and a weak ridging to the north will influence sensible weather over the next 2 to 3 days across the PDT forecast area. HeatRisk will increase from Today to Tomorrow forming widespread limited risk (level 1) to Level 2 in the the lower elevation valleys and and Columbia basin as high temperatures climb into the upper 80s and low 90s through the Columbia Basin and Yakima Valley. Afternoon thunderstorms across central Oregon a cross the John Day Basin and southern Blues are possible by late afternoon and early evening and will largely diurnally driven (weakening after sunset). For Thursday, steep mid level lapse rates in excess of 8.5 deg C/km will result from cooling air aloft and surface heating creating water loaded inverted v soundings, with enough mid level flows to create wind shear capable of long sustained TSRA/CB and down burst wind threat. A glance across the HREF CAMs vary temporally; initiating and spreading northeast over the Blue Mountains between 22z and 01z for the initial broken line of storms, which may linger farther north into the Columbia Basin as the evening progresses given ample PWATS (1.00"+) and mean CAPE (1000-1500 J/kg). Much of the forecast area has been upgraded from 5% chances for severe weather from a point to 15% chances for Thursday afternoon (slight risk).

Friday looks windy through the Kittitas Valley, Simcoe Highlands, Eastern Columbia River Gorge and the Columbia Basin of Oregon, as the pressure gradients increase behind a cold front associated with the eastward propagating upper low. NBM mean wind gusts average 40 to 49 knots in these areas, indicating high end wind advisory criteria.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

VFR conditions and winds of predominantly 10 kts or less (outside of any gusty outflow winds at RDM/BDN in showers and thunderstorms until roughly midnight) are forecast overnight through Thursday morning. There is a 30-50 percent chance of thunderstorms Thursday afternoon and evening across all TAF sites, which will be capable of producing sub-VFR conditions along with severe (50 kts or greater) outflow winds, hail, and frequent cloud-to-ground lightning.

HYDROLOGY

A glance at the PWATs for Thursday afternoon indicate about 1.00 inch average through the Blue Mt foothills and Lower Columbia Basin, which is in the 75th to 99th percentile for late May compared to climatology. At about 0.8 PWAT on average along the eastern Cascades Crest, are also elevate at around the 75th percentile. A marginal excessive rainfall outlook is highlighted across the Eastern Slopes of the Cascades, as well as into the adjacent Washington valleys into Central Oregon.

Preliminary Point Temps/PoPs

PDT 50 85 51 69 / 10 10 60 10 ALW 56 86 57 71 / 0 10 60 10 PSC 53 93 55 75 / 0 0 60 10 YKM 56 93 57 73 / 0 0 80 40 HRI 52 89 54 70 / 0 0 60 10 ELN 54 89 54 65 / 0 0 80 50 RDM 44 80 42 61 / 30 80 90 50 LGD 48 84 49 71 / 20 40 60 50 GCD 43 81 43 68 / 30 60 40 60 DLS 59 91 56 67 / 0 10 70 40

PDT WATCHES/WARNINGS/ADVISORIES

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