textproduct: Portland

SYNOPSIS

Cool and moist onshore flow will continue through Friday, maintaining below average temperatures with highs in the mid 60s to low/mid 70s each day. Light rain showers will continue on Sunday, however most of the day will be dry west of the Cascade foothills. Trending mainly dry Monday through Wednesday aside from a few light showers in the mountains. Chances for light showers increase slightly to 15-35% on Thursday, however measurable rain is unlikely to occur for most locations. A gradual warming trend is likely Friday into next weekend.

DISCUSSION...Sunday through Saturday night

The latest suite of model guidance continues to suggest cool and moist onshore flow will continue through Friday with predominately northwest flow aloft. This will maintain below average temperatures with highs ranging from the mid 60s to low/mid 70s each day, coolest at the coast and in the Cascades and warmest in the Willamette Valley and Portland metro. Expect mostly cloudy to overcast skies during the overnight and morning hours each day, with some breaks of sun during the afternoon hours. For reference, average high temperatures for this time of year are around 77-79 degrees for inland valleys and mid 60s at the coast. Average highs for inland valleys increase to around 80 degrees by the Fourth of July.

Chances for rain showers remain in the forecast on Sunday, however showers will be much lighter and more isolated today when compared to yesterday. In fact, much of the day will be dry at any given location, except in the Cascades and Cascade foothills where showers will be more frequent due to moist upslope flow. Conditions will trend mainly dry Monday through Wednesday aside from isolated light showers in the Cascades from time to time. Chances for light showers increase slightly to 15-35% on Thursday per the latest NBM guidance, highest in the Cascades. However, QPF amounts from model ensemble guidance are very low on Thursday. Even the NBM 90th percentile for 24-hr QPF from 5am Thursday through 5am Friday is near zero, except 0.05-0.25 inches southwest WA, the north Oregon Cascades, and along the north Oregon coast. This suggests showers will be very light and isolated on Thursday if they do occur with most locations staying dry.

Conditions begin to gradually warm Friday into the upcoming holiday weekend with dry weather expected. However, it is unclear exactly how much warmer temperatures will get and whether the warming trend will begin on Friday or on the 4th of July. Model spread for high temperatures is large on both Friday and the 4th of July, ranging from around 65-80 degrees on Friday for inland valleys and from 70-87 degrees on the 4th of July per the NBM 10th-90th percentile. The most likely outcome is for highs in the mid 70s on Friday, warming to the upper 70s to lower 80s on the 4th of July. Meanwhile, the coast is likely to remain in 60s for high temperatures. -23

AVIATION

Radar and surface obs as of 18Z Sun depicts light rain showers continuing to move southeastward through the airspace, along with VFR conditions except for MVFR CIGs at KVUO, KKLS, and coastal terminals. While MVFR CIGs at coastal terminals are expected to persist through the TAF period (30-70% chance of MVFR, highest at KAST), expect any remaining MVFR CIGs inland to improve to VFR by 19-20Z Sun. There is a 20-40% chance of MVFR CIGs after 06-12Z Mon for inland terminals. Westerly to northwesterly flow will continue through the period, with sustained winds generally 5-10 kt inland and 7-12 kt at the coast, strongest during the afternoon. Gusts up to 20 kt possible at a few terminals along the coast and inland during the afternoon.

KPDX AND APPROACHES...VFR conditions through at least 08Z Mon. There is a 20-40% chance of MVFR CIGs after 08-12Z Mon. Westerly winds around 5 kt will shift more northwesterly by 00Z Mon and increase close to 10 kt with gusts up to 18 kt. A few light rain showers are possible today, especially from now until 21Z Sun when probabilities for showers increase to 40-45%. ~12

MARINE

Buoy observations from early Sunday morning showed persistent northwest winds around 10 to 20 kt with steep seas near 8 to 9 ft at 9 seconds driven mainly by a fresh northwest swell. Expect these conditions to hold steady through Sunday night.

Weak high pressure builds over the coastal waters on Monday, however northwest winds will continue to build the ongoing northwest swell with significant wave heights increasing to 8 to 11 ft. Seas will be highest over the outer waters. There is a 20-40% chance significant wave heights will peak over 11 ft beyond 30 NM offshore on Monday, mainly to the north of Cape Falcon. Northwest winds and a fresh northwest swell then continues Tuesday through Wednesday, maintaining steep seas and hazardous conditions for small craft. Winds and seas will ease significantly Wednesday night into Thursday.

Given steep seas and wind gusts upwards of 20 kt, a Small Craft Advisory is in effect through Monday evening, except through Sunday evening for the central and southern inner waters where winds and seas are relatively lower. -23

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 11 PM PDT Monday for PZZ251-271>273.

Small Craft Advisory until 11 PM PDT this evening for PZZ252-253.