textproduct: Pendleton

KEY MESSAGES

1. Dry conditions will persist through the week

2. Instability with slight Chances of dry thunderstorms Thursday

3. Breezy to windy conditions and low RHs return Saturday *Fire Weather Watch*

DISCUSSION

Current satellite shows clear skies over the region tonight. Ground observations show some smoke over the region but not enough to impact visibility. However, air quality is still poor and advisories have been issued. This will continue to be an issue through the remainder of the week.

The upper level low off the cost and the ridge sitting in the Four Corners has the region wedged between the two systems. Southwest flow aloft continue to usher in dry air and current satellite shows very dry air at the surface. This will keep the region dry with humidities remaining in the upper teens to low 20%. Diurnally driven winds 10-15 mph will also persist through Friday. This will keep fire weather concerns elevated but not critical through Friday.

A shortwave will make its way across the region allowing for more instability to return to the region again today. While thunderstorm chances are very low, instability could cause active behavior around fires already on the landscape. NAM forecast soundings show MUCAPE values between 250-500 J/kg, lapse rates of 8.0 C/km, LI of -2 and bulk shear of 34 knots. This show clearly that the atmosphere is unstable and cumulus fields will likely build. With this, one can also not rule out a thunderstorm or two. Confidence in thunderstorms is low (>10%) while confidence in the instabiity is high (70-90%). Especially along the southern and eastern mountains of Oregon.

Saturday will be the next day of concern in the period. Models show the upper level low to begin making its way onshore and ahead of it is a surface cold front. This will bring elevated winds to the region on Saturday. NBM raw ensembles show 50-70% probabilities of wind advisory (>45 mph) criteria being met through the Kittitas Valley, Simcoe Highlands, the Gorge and the Columbia Basin. The winds coupled with the continued dry conditions has will elevate the fire weather concerns for Saturday. Relative humidities will hover in the upper 20% to low 30% with some ares seeing a high as 35% (70- 80% confidence). The low RHs and elevated winds could lead to critical fire weather concerns on Saturday, therefore a fire weather watch has been issued.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

VFR conditions currently, which is expected to stay the course through the period. Breezy winds for KDLS through the the day today with sustained 15-20kts and gusts of 20-25kts. KRDM/KBDN will also experience breezy winds this afternoon as gusts hover between 15-20kts. Elsewhere, winds will stay light (<10kts) under clear skies. 75

FIRE WEATHER

Fire weather concerns remain elevated through Friday with low RHs and diurnally driven winds. Saturday is the next major fire weather concerns day with incoming winds exceeding advisory criteria of gusts greater than 45 mph or sustained winds of 30 mph. NBM raw ensembles show a 50-60% probability of occurrence of winds exceeding criteria. Daytime RHs will remain low in the upper 20% to low 30%. The winds could override the RHs creating critical fire weather concerns Saturday. A Fire Weather Watch has been issued for the Lower Columbia Basin of OR and WA and for the canyon grasslands of Wallowa County.

Preliminary Point Temps/PoPs

PDT 87 55 92 62 / 0 0 0 0 ALW 90 60 95 66 / 0 0 0 0 PSC 92 56 95 62 / 0 0 0 0 YKM 91 57 95 61 / 0 0 0 0 HRI 90 57 94 64 / 0 0 0 0 ELN 86 56 92 59 / 0 0 0 0 RDM 88 47 93 51 / 0 0 0 0 LGD 92 55 98 59 / 0 0 0 0 GCD 94 54 100 57 / 0 0 0 0 DLS 85 58 95 63 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Fire Weather Watch from Saturday morning through Saturday evening for WAZ691-693. OR...Air Quality Alert until noon PDT Friday for ORZ041-049-050-502- 503-505-506-509>511. Fire Weather Watch from Saturday morning through Saturday evening for ORZ691-693.