textproduct: Pendleton

DISCUSSION

Traffic cams are showing dense fog over Central OR with surface observations observing visibilities of a quarter mile or less. This led to issuing a Dense Fog Advisory for that area until 12 PM PST today. While the advisory is out until 12 PM today, the HRRR does show the fog dissipating a little early. However, it can't be ruled out due to expected oscillating visibilities. Otherwise, current radar and satellite imagery shows a band of light precip continuing to move across portions of the Foothills-Northern Blue Mountains from west to east.

The aforementioned shortwave trough will continue its way over to the PacNW with persistent precip activity through Monday with the associated weak atmospheric river (IVT of 100-200 kg m/s). Storm Total QPF amounts from late this morning through Tuesday morning (18Z Sun to 12Z Tues) for the lower elevations will be exceeding 0.10 inch with a 40-70% 24 hr NBM precip probability and >60% prob for 0.35 inch for the Northern Blues, southern parts of Wallowa County and OR Cascades crest. The QPF amounts may slightly exceed 0.10 inch for the WA Cascades (25-45% confidence). Along with QPF amounts, snow accumulations have increased to 2-6 inches for the mountain areas (Northern Blues, East Slopes of WA Cascades and OR Cascades) through Tuesday morning. Snow levels will gradually drop below pass levels through Tuesday morning.

After seeing snow accumulations trending downward from the past two nights, we may see moderate to heavy mountain snow Tuesday night through Thursday morning with another shortwave approaching. Snow ratios will be high enough to indicate moderate snow amounts. Snow levels will drop below 1.5kft. It could warrant Winter Weather Advisories for the WA/OR Cascades seeing a 3-day Storm Total Snow exceeding 5 inches (>50% confidence) and possibly a Winter Storm Watch for the Northern Blues exceeding 8 inches (30-50% confidence). Thursday night into Friday, mountain snow will still linger over the Northern Mountains and WA/OR Cascades (30-40% confidence). Feaster/97

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

KRDM/KBDN will be in LIFR due to dense fog with visibilities of 1/2 mile or less. Conditions may improve during afternoon hours, but expect oscillating visibilities. Light rain will continue through morning hours for KDLS/KPDT/KALW. Otherwise, flight categories may vary between VFR and MVFR through the day for most sites with the exception of KALW becoming IFR with CIGs at 900 ft. Feaster/97

Preliminary Point Temps/PoPs

PDT 34 44 28 45 / 40 90 40 40 ALW 37 44 30 45 / 50 90 50 50 PSC 34 47 29 48 / 30 70 20 20 YKM 31 45 24 41 / 10 30 10 10 HRI 35 47 28 46 / 30 80 30 20 ELN 28 40 23 37 / 10 30 10 30 RDM 30 42 21 38 / 30 50 20 20 LGD 34 47 24 41 / 40 90 70 80 GCD 34 46 24 39 / 20 80 60 70 DLS 38 47 30 45 / 30 70 30 50

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...Dense Fog Advisory until noon PST today for ORZ511.