textproduct: Portland

SYNOPSIS

A weak frontal system continues to push eastward this evening with scattered showers throughout the area. Showers will dissipate overnight as high pressure builds through next week. Cold mornings will be accompanied by fog and frost with light winds. A pattern shift is likely late in the week.

LONG TERM...Wednesday through Saturday

Transitioning into later in the week, conditions will begin to shift. There continues to be a great level of uncertainty in the long-term pattern due to the pervasive ridge while a low pressure system attempts to build near the surface. As has been the trend, the frontal band associated with a low forming along the Alaska Panhandle has delayed another day further and deterministic models suggest it now making landfall on Friday. This outcome is slightly more supported aloft but dynamic features, but overall it is very messy. Being a typical winter time pattern, the coast and Coast Range will receive a brunt of the precipitation. Now I know one thing that is on many people's mind is snow at lower elevations. A colder several days followed by a frontal system may seem like a favorable set up. However, in this case the frontal system coming in is still warm enough and the overall ambient temperatures are not cold enough during the day to set the stage for a low-elevation snow. So, that's one less thing to worry about at this point. -27

AVIATION

Radar imagery and terminal observations as of late Saturday evening depicts decreasing showers and VFR conditions as high pressure re-builds over the area. Mostly SCT/BKN high clouds across the area, but increasing cloud breaks overnight will bring potential for fog/frost development across the Willamette Valley. Guidance suggests a 40-60% chance for LIFR/IFR CIGs/VIS across the Valley between 12-18z Sun. Moderate confidence for fog development since temperatures are going to drop to the low to mid 30s. Could see widespread frost development instead, especially over grasses and metal surfaces. This would limit the amount of fog/stratus that forms. Any fog that develops Sunday morning should scatter out and return VFR conditions after 18-20z Sun. Along the coast, conditions remain VFR as light offshore flow prevails. Light and variable winds elsewhere overnight, becoming northerly under 10 kt on Sunday.

KPDX AND APPROACHES...VFR conditions until around 12z Sun. 50-60% chance for LIFR/IFR conditions due to fog between 12-18z Sun. Clearing skies, light winds and temperatures near or below freezing could result in frost formation, especially over grasses and elevated metal surfaces. If frost develops, then fog may be limited. -10

MARINE

Buoy observations as of late Saturday evening are showing seas falling to 10 feet or less. Therefore, the Small Craft Advisory across the waters has been cancelled. Seas will continue to subside overnight and fall to 4-5 ft on Sunday. High pressure will build over the waters along with a weak thermal trough along the coast, bringing east-northeasterly winds under 15 kt through Tuesday. Seas re-build to 7-8 ft Monday-Tuesday as a west-northwesterly swell moves in. -10/27

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...None.