textproduct: Portland

SYNOPSIS

Drizzle remains this morning as an area of weak high pressure builds over the region. The next frontal system arrives on Sunday bringing another round of rain to the area, then it is followed by a moist cold front and strong zonal flow. Cold air filters into the region on Monday night into Tuesday bringing chances of low-elevation snow and high probabilities for much needed Cascade snow though confidence remains very low.

LONG TERM...Tuesday Night through Friday

As quick as the cold air moved in, it exits and a warmer airmass fills in behind it. A high pressure system off of the California Coast is interacting with the Gulf of Alaska low. The compression of the two is pushing a stronger frontal system over the region. Heaviest precipitation again appears to be within Washington and British Columbia but as the low advects into Washington, that precipitation will spread further south. While this system has some of the dynamics of an atmospheric river, it will generally behave much like a typical March rainy system and will have minimal if any impacts. One challenge will be the timing of the precipitation of this system to any lingering cold air. If there remains cooler air in the area we cannot rule out another low- confidence snow type scenario. However with the warmer air trailing quickly, any snow that would fall at the lower elevations will melt. Additional moderate to heavy snow is possible in the SW Washington Cascades Thursday into Friday, but not much else south of this.

In terms of other impacts, rain amounts will be steady through the remainder of the week but there are no concerns for flooding or rapid snow melt. This is a dynamically changing forecast with many components to consider so even a slight shift will completely change the outcome. -27/03

AVIATION

High pressure with onshore flow. Drizzle remains this morning with localized IFR/LIFR conditions along the coast and VFR inland. Looking at minimal improvement along the coast as the chances for IFR CIGs remains around 80-90%. Inland, high resolution models are suggesting increasing chances for MVFR CIGs this morning, however, based on current observations and the high pressure moving in decided to trend towards VFR stratus. Overnight as conditions cool and the ridge breaks down, will see a decline of inland terminals. Will see a return to widespread MVFR CIGs with some ares of fog (though not expected to be widespread).

KPDX AND APPROACHES...VFR through the early part of the forecast then MVFR as stratus backbuilds off of the Cascades and fills the terminal. There is a 30% chance that conditions remain VFR through the day though if there is enough mixing or if winds amplify. -27

PQR WATCHES/WARNINGS/ADVISORIES

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