textproduct: Pendleton

KEY MESSAGES

- Cool and breezy conditions through the midweek.

- Warming trend returns above normal high temperatures Friday.

- Heat and low humidities peak Saturday through Monday.

DISCUSSION

Current radar and infrared satellite imagery shows a broken line of showers extending across Union and Wallowa counties under mostly clear to partly cloudy skies. This is in response to a weak upper level shortwave slowly passing through the region, which will lead to the potential for isolated thunderstorms over these areas through the afternoon and early evening. The Storm Prediction Center has placed Wallowa county in their general thunderstorms (0 out of 5) category for the day, highlighting the likelihood of sub-severe storms. Precipitable water values are between 0.75-0.9" or 140-160% above normal, so any storm cells that do develop should include a wetting rain (>0.10"). This shortwave feature has also attributed to a pressure gradient developing along the Cascades to bring breezy winds across the Lower Columbia Basin/Gorge, east slopes of the Cascades, and the Kittitas Valley. Sustained west winds of 20-27 mph with gusts of 30-35 mph are expected in these areas, but the NBM does suggest there to be a 25-45% chance of advisory level wind gusts (+45 mph) for the Dalles and Ellensburg areas - peaking around 5 PM. This will continue to be monitored through the afternoon in case an advisory is needed.

A second upper level shortwave passes through the area Wednesday, broadening out the upper level trough and leading to another breezy day across the Lower Columbia Basin, Simcoe Highlands, Eastern Gorge, and Kittitas Valley with similar sustained winds and gusts as today. This broadening of the overall trough feature that is draped across the Pacific Northwest will again be stretched late Thursday as yet another shortwave moves into the region. This third shortwave will lead to flow aloft turning from the northwest to the west to intensify the gradual warming trend experienced earlier in the week. As a result, high temperatures will be near to above normal Friday before becoming above normal through the weekend with highs in the low to mid-90s across the Lower Columbia Basin.

A building upper level ridge across the Desert Southwest, and surface high pressure to our east will stall a cold front across Central WA/OR over the weekend which will further enhance warming and drying. Afternoon humidities will drop into the single digits over portions of Central Oregon, and in the low to mid-teens across the Lower Columbia Basin on Saturday. Very slight improvement is expected through Monday, but overnight humidity recoveries will continue to decrease and eventually reach values between 35-55% by Tuesday morning. 75

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

VFR conditions to prevail through the period. Breezy winds (15-25kts with gusts up to 35kts) will continue at site DLS through the period. Breezy winds (12-17kts with gusts up to 25kts) at sites PDT/RDM/BDN/YKM/ALW will become 12kts or less overnight, with light winds prevailing at most sites tomorrow. Site PDT will see breezy winds redevelop after 17Z. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 44 76 46 79 / 0 0 0 0 ALW 51 77 52 81 / 0 0 0 0 PSC 49 81 50 83 / 0 0 0 0 YKM 49 82 50 83 / 0 0 0 0 HRI 47 79 49 82 / 0 0 0 0 ELN 45 74 46 77 / 0 0 0 0 RDM 34 75 38 79 / 0 0 0 0 LGD 43 76 45 81 / 0 0 0 0 GCD 40 78 43 83 / 0 0 0 0 DLS 50 73 51 79 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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