textproduct: Pendleton

DISCUSSION

Current satellite shows a very predominant stratus deck in place over the CWA with only the eastern mountains seeing a slight reprieve from the clouds. This has aided in keeping temperatures cool. Highs today across much of the region, with the exception of central OR south and southeast of Bend, will be below 35 degrees while the aforementioned areas will be in the low to mid 40s.

Models are in form agreement that there upper level high pressure system will remain overhead through Friday ahead of a weak shortwave. That shortwave is expected to move over the region Thursday night into Friday. However, guidance shows this to be mostly dry with no expected precipitation (80+% confidence). Also, 700-500 mb guidance shows very little instability and the omega field shows little to no mixing. With that, fog and low stratus will likely continue even with the disturbance coming through Friday.

After Friday, models remain in relatively good agreement that another high pressure ridge and dry northwest flow will set up over the region. This will continue to keep the stratus decks low and allow for fog to reform. Especially in the valley areas with pattern recognition allowing confidence in the forecasted decks and fog to be relatively high (60-80% confidence). With this, temperatures will remain cooler under the stratus deck with temperatures averaging in the mid to upper 30s with a few locations seeing low 40s by the end of the weekend.

By the beginning of the week, models diverge a bit with the ECMWF keeping the ridge over head but weakening, while the GFS breaks down the ridge and shifts the flow to the west. Guidance shows winds to remain calm through the transitions as well. With that said, confidence in how next week will shake out is low/moderate (40-60% confidence) in which way the models swing. If we keep the ridge overhead, fog and stratus will remain the concern. If we turn westerly, warmer temperatures could be in store if the system can scour out the cold pool. 90

AVIATION...00Z TAFS

Not much change expected across the area with continued low clouds and areas of fog. Generally MVFR conditions currently, with IFR/LIFR in a few areas. Some decrease in CIGS/VSBYS is possible overnight. WInds are expected to be light.

PRELIMINARY POINT TEMPS/POPS

PDT 24 32 21 33 / 0 0 0 0 ALW 27 29 23 33 / 0 0 0 0 PSC 26 33 23 39 / 0 0 0 0 YKM 23 34 21 37 / 0 0 0 0 HRI 26 36 23 37 / 0 0 0 0 ELN 22 32 20 33 / 0 0 0 0 RDM 18 29 17 32 / 0 0 0 0 LGD 21 33 20 35 / 0 0 0 0 GCD 21 32 22 37 / 0 0 0 0 DLS 29 38 26 39 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

OR...Freezing Fog Advisory until 10 AM PST Thursday for ORZ050.

WA...None.