textproduct: Portland

SYNOPSIS

High pressure builds through the middle of the week, which will bring cold mornings along with fog/frost development overnight with light winds. A pattern shift is likely for the latter part of the week.

LONG TERM...Wednesday through Saturday

Looking into the middle and latter part of the upcoming week, models are suggesting a pattern change for the region. However, there continues to be a great level of uncertainty in the long-term pattern due to the aforementioned ridge talked about in the short term discussion above. Deterministic models are showing a low pressure system attempting to build off the southern California coast as well as within the Gulf of Alaska, and these systems could break down the ridge over the Pac NW. We will continue to monitor these scenarios as models are slowly coming into better and better agreement. While we are well into winter and these systems are typically colder, the systems looking to push out the ridge of high pressure are showing 850 mb temperatures around 4C to 8C. So, no low level snow at this point is not in the cards. /42

AVIATION

Current radar and satellite imagery, along with terminal observations show widespread VFR conditions with intermittent pockets of MVFR to LIFR conditions. High pressure will be the dominant feature over the region through at least late Wednesday/early Thursday. This will result in slowly clearing skies, relatively light east/northeast winds and drying conditions. Therefore, expect predominately VFR conditions during the daytime with mostly VFR conditions expected overnight. However, with the aforementioned conditions, this will result in favorable frost/fog development within the Willamette Valley each night as overnight temperatures are expect to fall towards freezing or a few degrees below. Currently, conditions are favoring fog development, but cannot rule out some frost development. Guidance suggests a 40-60% chance for LIFR/IFR conditions across the Willamette Valley developing between 12Z-18Z Sunday. Any fog/frost that does develop should scour out and any lowered flight conditions should return to VFR after 18Z-20Z Sunday. Along the coast, conditions remain VFR as light offshore flow prevails.

KPDX AND APPROACHES...VFR conditions until around 12Z Sunday. 50-70% chance for LIFR/IFR conditions developing as a result of fog between 12Z-18Z Sunday. With freezing/near freezing overnight temperatures, frost could develop over fog. Any fog/frost that does develop should scour out and any lowered flight conditions should return to VFR after 18Z-20Z Sunday. /42

MARINE

High pressure builds over the waters along with a weak thermal trough along the coast, bringing east-northeasterly winds under 15 kt through Tuesday. Seas 3 to 4 ft, with seas re-building towards 6 to 8 ft Monday/Tuesday as a fresh west-northwest swell moves in. A more active pattern looks to return to all waters towards the latter part of this week. /42/10

PQR WATCHES/WARNINGS/ADVISORIES

OR...Dense Fog Advisory until 10 AM PST this morning for ORZ108>118.

WA...Dense Fog Advisory until 10 AM PST this morning for WAZ204>207.

PZ...None.