textproduct: Pendleton

KEY MESSAGES

- Breezy winds and dry conditions Today - Elevated Fire Weather

- Isolated thunderstorms Saturday

- Widespread showers Saturday through Sunday morning

DISCUSSION

Zonal flow was developing with an increasing mid level heights gradients Today. HiRES models show a weak trough forecast/placed across the Interior and Pacific NW by about 7 am Friday. This is the initial mass adjustment in advance of a more robust upper low poised to move onto the PAC NW coast on Saturday. Both of these features will have weather implications, with a chance for thunderstorms being the highest risk element on Saturday.

Winds Today will increase though the late afternoon across the eastern Columbia River Gorge, the Columbia Basin of Oregon/Blue Mt foothills as well as though the Kittitas Valley, with speeds from the HRRR showing about 15 up to locally 20 knots./ Gust potential in these areas is in the 20 to 25 knot range and locally higher around Dallesport. LAV guidance maintains breezy winds through the evening hours as the upper wave moves into the region spreading light showers across the area. The best forcing for these showers as typical is across the Blue Mts where trace to a few hundredths of an inch of rain is forecast by the HREF. Most of the area will just see clouds whereas a Trace to a few hundredths of an inch area possible around midnight along the Blue Mts of Oregon.

The aforementioned system will leave Friday cooler (post cold front), in the 60s and 70s. Breezy conditions very early Friday morning will gradually ramp down to light (under 10 knot) through the morning.

Saturday look quite low risk for convection given the sub 50 J/kg SBCapes developing and probability of thunder under 10% now by the NBM mean. The 75th percentile NBM only averages 50 to 150 J/kg CAPE across the higher terrain with no improved ts chances, which really do not start to register until the early evening and overnight hours. With the later start now being shown, the Cascades and the Blue Mts of Oregon are showing about a 15-20% chance of a wetting rain (0.10) by 5 pm, while much greater probability (50-70%) exists though midnight over the Cascade eastern slopes, the central Oregon Mts through the Blue Mts of Oregon. Sunday remains wet based on these trends. With a 48 hour expected precipitation around a quarter of an inch over central Oregon to three quarters of an inch to one inch across the highest mountain zones. Considering uncertainty in outcomes, the ranges in this highest amounts could be from around a quarter inch on the low end (25th percentile) to an inch and a half (at the 75th percentile).

The balance of the week looks dry with a gradual warming trend peaking Thursday with still seasonable 70s and low 80s across the region.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

VFR conditions prevail at all TAF sites through the period. On going light showers over PDT and the Blue Mountains and are forecasted to end at 12Z. Winds are slated to move to calmer conditions as the day progresses with the largest changes occurring in wind direction rather than speed.

Preliminary Point Temps/PoPs

PDT 48 72 46 72 / 30 0 0 10 ALW 53 74 52 74 / 30 0 0 0 PSC 53 77 49 77 / 10 0 0 0 YKM 51 74 52 73 / 0 0 0 20 HRI 53 76 47 76 / 10 0 0 0 ELN 47 70 48 69 / 0 0 0 10 RDM 46 74 39 66 / 0 0 0 40 LGD 49 73 46 76 / 40 0 0 30 GCD 49 75 46 77 / 0 0 0 30 DLS 52 76 53 74 / 0 0 0 20

PDT WATCHES/WARNINGS/ADVISORIES

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