textproduct: Pendleton

KEY MESSAGES

- Warming trend through Monday, followed by cooler air moving in midweek via a cold frontal boundary.

- Chances of showers and thunderstorms increase Tuesday through Wednesday.

- Breezy conditions going into Wednesday as the frontal boundary passes through.

DISCUSSION

More mild overnight temperatures are expected as the airmass modifies and thicker cloud cover overspreads the Interior NW Tonight. Lows in the upper 30s and low 40s will warm efficiently Sunday morning, reaching highs in the upper 60s to 70s across all non mountain zones. An amplifying upper level ridge and sw boundary layer flow will continue to modify the airmass by Monday with even warmer lows in the 40s and low 50s, reaching highs approaching 80 degrees in the Eastern Columbia River Gorge, central Oregon, Lower Columbia Basin and John Day Basin. The days 4 and 5 LREF, centered on Tuesday seem to indicate slightly slower and southward (offshore) solutions shared by the clusters 1 through 4. By Wednesday general agreement in the clusters show the low moving inland as an open 500 mb trough. ESAT suggests about a +2 to 3 standard deviation of specific humidity as compared to model climatology at 500 mb but only normal to about 1 SD at 700 mb. A marginal increase in confidence in thunderstorm chances is with respect to timing as the NBM ensemble continues to focus and initial 10% chance of Thunderstorms across the Oregon Cascades late afternoon and early evening Monday followed by more broad chances Tuesday afternoon, with less than 10% chances across the lowlands, about 10-15% chances across the Cascades and Northern Blues, and a maximum of 25% chances across the rest of the eastern mountains, with sbcape values between 150-400 J/kg. Increasing expectations of wetting rains with the current ensembles, as chances for 0.10 or higher rainfall by Tuesday evening range from 60 to 80% for the Oregon Cascades and central Oregon (Bend/Redmond) and across the John Day Basin and southern Blues. The wetting rain chances become widespread at 60 to 80% chances by Wednesday morning with the expectation of the Columbia river Gorge and Lower Columbia basin and Yakima Kittitas valleys where probability is around 50-60% for wetting rains.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

VFR conditions with winds less than 10 kts will prevail through Sunday.

Preliminary Point Temps/PoPs

PDT 68 41 74 45 / 0 0 0 0 ALW 68 45 74 51 / 0 0 0 0 PSC 71 40 77 46 / 0 0 0 0 YKM 67 40 74 47 / 0 0 0 0 HRI 70 39 76 45 / 0 0 0 0 ELN 63 38 71 44 / 0 0 0 0 RDM 70 36 74 41 / 0 0 0 0 LGD 61 36 69 41 / 0 0 0 0 GCD 64 38 72 44 / 0 0 0 0 DLS 72 45 75 51 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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