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 Ochoco 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 /00Z TAFS THROUGH 00Z FRIDAY/

VFR conditions currently across all sites, which will stay the course through the period. Breezy 20-30kt wind gusts are occurring for KRDM/KBDN and persist through the evening, subsiding later tonight. These terminals will experience a potential for isolated thunderstorms this evening. Any thunderstorms that develop will include breezy and erratic winds, brief hail, and periods of heavy rainfall. All remaining terminals will stay dry with winds of 10kts or less. 75

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 70 / 0 10 50 10 ALW 56 86 58 73 / 0 20 50 10 PSC 53 92 55 78 / 0 0 50 10 YKM 56 93 56 75 / 0 10 70 40 HRI 52 88 54 72 / 0 0 60 20 ELN 54 89 53 66 / 0 10 70 50 RDM 44 80 42 62 / 30 80 90 40 LGD 48 85 49 70 / 20 30 60 40 GCD 43 81 44 68 / 40 60 50 60 DLS 59 90 56 69 / 0 10 90 20

PDT WATCHES/WARNINGS/ADVISORIES

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