textproduct: Pendleton

KEY MESSAGES

- Dense fog in the Grande Ronde Valley this morning, with patchy fog elsewhere.

- Near-normal temperatures and mostly dry conditions until late Wednesday.

- Periods of more active weather, breezy winds, and predominantly above-normal temperatures late week into next week.

DISCUSSION

GOES-18 water vapor imagery shows ample moisture aloft spreading across the region, north of a closed low-pressure system which is located near 40N, 128.5W. Radar reveals some light returns over the forecast area, but 00Z observed soundings upstream of the forecast area at SLE and MFR showed a very dry sub-cloud layer. Thus, little in the way of precipitation is anticipated with this system; PoPs are generally 5-15% for our population centers today.

At the surface, dense fog has been present in the Grande Ronde Valley since late yesterday evening, and a Dense Fog Advisory remains in effect this morning. Elsewhere, patchy fog has developed in portions of the Columbia Basin, but has not yet become widespread enough to warrant any headlines.

The aforementioned area of low pressure is expected (99% confidence) to move inland over southern Oregon and northern California by later today. Mostly dry conditions (PoPs of 20% or less) are forecast to continue until late Wednesday. Ensemble guidance is in very good agreement that a shortwave trough will arrive from the Pacific late Wednesday, and subsequently track inland through Thursday. Aside from some light precipitation and locally breezy winds, little in the way of impactful weather is anticipated with the shortwave. Near-normal temperatures are expected to continue until late week.

Friday into early next week, ensemble guidance is showing likely (80%) periods of wet weather for the Washington Cascades, with significantly lower chances (10-30%) for wet weather east of the Cascades. East of the Cascades, especially across eastern Oregon and southeast Washington, above-normal temperatures and periods of breezy southerly winds are expected (70% confidence).

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

VFR conditions are forecast at most sites for the next 24 hours; notable exceptions are at PDT/ALW (50-80% confidence), and possibly PSC (30% confidence) where fog is developing or anticipated to develop into the morning hours. Otherwise, A low-pressure system tracking south of the forecast area will bring ample cloud cover to the region today, and very low (5-15%) chances of precipitation. Clearing skies are forecast by later afternoon and evening. Winds of 12 kts or less are forecast at all sites.

Preliminary Point Temps/PoPs

PDT 50 29 54 36 / 10 0 0 40 ALW 50 33 53 39 / 0 0 0 20 PSC 53 29 55 34 / 10 0 0 40 YKM 56 31 55 36 / 10 0 0 30 HRI 52 28 55 35 / 10 0 0 50 ELN 52 26 53 29 / 10 0 0 50 RDM 51 20 57 30 / 0 0 0 40 LGD 56 29 57 34 / 0 0 0 20 GCD 58 30 58 35 / 0 0 0 30 DLS 57 33 58 41 / 10 0 0 70

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...Dense Fog Advisory until 10 AM PST this morning for ORZ049.