textproduct: Portland

SYNOPSIS

Warm and sunny conditions continue through Monday as high pressure builds over the region. This will result in localized Moderate HeatRisk across the inner Portland Metro, Columbia River Gorge, and Upper Hood River Valley. An upper- level trough moving into British Columbia Tuesday to Wednesday will cool temperatures a few degrees and a 15-20% chance for light rain along the south Washington and north Oregon coast. Late in the week, persistent onshore flow will maintain seasonable temperatures. Make sure to practice water safety when swimming in area rivers.

LONG TERM...Tuesday through Saturday

Tuesday to Wednesday, ensemble guidance continues to show an upper-level trough from the Gulf of Alaska moving east/southeastward into British Columbia. This system is expected to stay northward, keeping northwest Oregon and southwest Washington predominately dry. However, could see a 15-20% chance for precipitation along the north Oregon and south Washington coast. Despite the lack of precipitation, this system will still maintain onshore flow and keep temperatures near seasonal normals. West-northwesterly winds are generally expected to be light for most areas during this time. However, will see locally breezier winds along the central Columbia River Gorge and Upper Hood River Valley, where there is a 35-45% chance for at least isolated wind gusts exceeding 40 mph Tuesday and Wednesday.

Thursday, most ensemble members show the aforementioned trough weakening as it moves eastward through British Columbia and returning dry, zonal flow over the Pacific Northwest. By Friday- Saturday, ensemble members are showing additional troughing moving down from the Gulf of Alaska into the northeast Pacific/British Columbia. There still remains uncertainty with the exact placement and magnitude of this additional troughing, but generally this system remains far enough north to keep us dry. If this pattern does pan out, this would support continued onshore flow with seasonable temperatures and little to no precipitation. -10

AVIATION

Largely VFR conditions continue across the airspace. At inland terminals, prevailing VFR is very likely (85% chance or higher) throughout the period. Highest chances for low clouds (10-15% chance of MVFR cigs) are limited to the immediate Cascade foothills from 12-18z Mon. Diurnal winds north to northwest winds will ease below 5 kt tonight, then build to 5-10 kt Monday afternoon.

At coastal terminals, chances for MVFR to LIFR cigs beneath marine stratus are much higher, although confidence in the coverage of low clouds is only moderate. As of 0530z, LIFR cigs are limited to the central OR coast, with short-range guidance and satellite trends supporting continued erosion of the cloud deck, favoring a return to MVFR cigs at KONP by 08-09z Mon. Resurgent stratus coverage is then expected beyond 12z Mon, returning cigs near 500 ft at KONP and raising chances for MVFR cigs at 1.5-2.5 kft to 60-80% at KAST. Some clearing is expected by Monday afternoon before further marine stratus arrive after 00-03z Tue. Diurnal north to northwest winds will ease to around 5 kt tonight, then build to 10-15 kt with gusts near 20 kt Monday afternoon.

KPDX AND APPROACHES...High chances (greater than 90%) of VFR conditions persisting throughout the period. Largely high cloud cover expected overnight before skies clear Monday. Diurnal northwest winds ease below 5 kt tonight, then build to 5-10 kt after 18z Mon. -36

MARINE

High pressure over the region is leading to the formation of a thermal trough over the waters. The typical summertime pattern means that we are seeing gusty northerly winds over all of the outer and inner waters, with wind waves increasing. Seeing anywhere from 20-25 kt gusts over the waters, with buoy 46050 reporting gusts up to 27 kt this afternoon. This will be the trend over the next several hours for the northern waters, then will slowly dissipate. Have extended all of the small craft advisories, maintaining a staggered cancellation moving from north to south. The northern waters will ease first, following by the central and lastly the southern. Seas will generally remain around 7 to 9 ft at 10 seconds but it's not uncommon for northerly winds like this to compound with the primary northwesterly swell direction. Thus, the wind wave may bring isolated 10 ft seas - though not expected to be widespread or long lasting.

Conditions will ease on Monday as a long wave trough and associated shortwave energy surges move over the region on Wednesday. -27

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.

WA...None.

PZ...Small Craft Advisory until 5 AM PDT Monday for PZZ251-271.

Small Craft Advisory until 11 AM PDT Monday for PZZ252-253-272- 273.