textproduct: Pendleton

KEY MESSAGES

- Warmer through Tuesday

- Breezy with chances for shower and Thunderstorms Tuesday into Wednesday

DISCUSSION

The synoptic pattern features an upper ridge that will slide east over the region over the next 12-24 hours, bringing high mid level (500 mb) relative humidity and plenty of mid level cloud cover. This pattern should relegate temperatures to above freezing across all of the low lands areas for early Saturday morning. Afternoon highs will trend warmer over the next 3 days, peaking on Monday. An initial push of weak moisture/instability might lead to isolated showers and thunderstorms (less than 10% lightning risk) across the Oregon Cascades, followed by a more robust push of moisture aloft and lending to higher thunderstorm chances (15 to 20 %) centered across the Foothills of the northern Blue mountains on Tuesday afternoon and Tuesday night. Surface based CAPEs are modeled as high as around 400 j/kg across these mountain zones. NBM mean wetting rains on the 6 hourly basis following the initial onsets of precipitation are limited to the higher elevation of the mountain zones. On the 24 hour basis wetting rains will be around 50% across the lower Columbia Basin. Driest areas at this time look to be central Oregon from Madras to Bend and the Yakima and and Kittitas Valley areas from Ellensburg to Yakima where chances for wetting rains of 0.10 or more are only 25 to 30%. A fair amount of uncertainty exists with respect to all of these features as the the Day 5 cluster analysis shows a balanced distribution of clusters ranging from a heavily weighted GEPS showing the upper low right over the coast Apr 21/22 to heavily weighted GEFS that is much farther offshore. As an alternative scenario, the latter of these might lead to a slower progression of then pattern during the week or even more more of a a dry slotting across central Oregon. Assuming the mean of these scenarios develops, temperatures are expected to be cooler from Wednesdays into Thursday following the precipitation maker, with NBM mean highs limited to the low and mid 60s across the Yakima, Kittitas valleys and Lower Columbia Basin/Eastern Gorge zones, and the mid 50s across central Oregon. Wednesday might be the most breezy/windy of the day as well across the foothills of the northern Blues and the Simcoe Highlands.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

VFR conditions will persist through the forecast period. CIGs will remain mostly 25kft and above with winds remaining below 6 kts at all TAF sites except PDT where winds will be around 9 kts through 18Z then becoming light after. 90

Preliminary Point Temps/PoPs

PDT 36 69 41 74 / 0 0 0 0 ALW 40 69 45 74 / 0 0 0 0 PSC 36 71 40 77 / 0 0 0 0 YKM 37 68 41 74 / 0 0 0 0 HRI 36 71 40 76 / 0 0 0 0 ELN 34 63 38 71 / 0 0 0 0 RDM 28 70 37 74 / 0 0 0 0 LGD 32 61 37 69 / 0 0 0 0 GCD 32 64 38 72 / 0 0 0 0 DLS 40 71 45 75 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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