textproduct: Portland

UPDATE

Thunderstorms along the Cascades appear to be over performing in the way of lightning and potential hail. CAPE values are higher than what we normally see for this region, and we cannot rule out quarter inch to half in hail in some locations near the Cascade Crest and the higher elevations of the Cascade foothills. Continuing to watch radar this afternoon, but with these storms over performing, there may be more widespread thunder than previously thought and what the probabilities may suggest. -27

SYNOPSIS

Warm temperatures feed into an evening of showers and thunderstorms. Thunderstorm activity will be highest this evening over the Cascades and Cascade foothills, then will progress westward impacting the north coast by early Thursday morning. Around a 20-30% chance of thunderstorms throughout the area though this afternoon they have initiated a bit earlier than previously forecast. Cooler on Thursday, then heating up and drying out over the weekend into Tuesday.

LONG TERM...Saturday through Wednesday

Ridging over the central CONUS is expected to rebuild into the PacNW, supporting a warming trend Saturday and into early next week. The interior lowlands can expect highs in the mid to upper 80s on Saturday, building into the low 90s for Sunday and Monday. In this pattern, marine stratus is likely, especially along the coast though it could transition down the Columbia River into the interior lowlands. If cloud cover becomes pervasive, it will have an impact on high temperatures and minimum humidity. There is some spread among the NBM in exact high temperatures, ranging from the mid 80s to upper 90s in the 10th-90th percentiles so could see adjustments moving forward. Moderate HeatRisk is currently forecast across the interior lowlands, including the Cascade foothills, for both of these days. Chances for major HeatRisk are generally 10-30% for the Portland metro and Columbia River Gorge. Warm temperatures are expected to continue into the middle of next week as models continue to anchor the ridge over the CONUS. -19/27

AVIATION

Southerly flow aloft will continue as an upper level low spins offshore. Predominately VFR conditions through Wednesday. Marine stratus is forecast to return along the coast this evening and produce MVFR/IFR cigs, as early as 01-03z Thu at KONP and 03-06z Thu at KAST. A stronger marine push tonight is producing a 25-45% chance of MVFR cigs at most inland sites, higher at 50-70% at KEUG, after 10-12z Thu. Any lowered cigs inland should improve to VFR by 18-21z Thu. Winds generally north to northwest and light, increasing to 8-10 kts after 21-23z Wed. The except is KONP where winds are 11- 13 kts with occasional gusts up to 20 kts. Winds decrease after 03- 06z Thu.

The upper level low will approach the coast tonight through Thursday, bringing increasing chances for showers or elevated thunderstorms north of Salem. Initially, thunderstorm chances of 15- 20% will be limited to the Cascades between 20z Wed - 12z Thu. Then chances spread west to the coast and increase to 15-25% from 12- 21z Thu, with best chances along the Coast Range and Coast between 12-18z. Main impact with any thunderstorms is abundant lightning and brief erratic and gusty winds. Since probabilities are low at each terminal, have not added to the TAFs at this time.

Smoke aloft is moving north into NW OR and SW WA from a wildfire in southern OR north of KMFR. This may at times produce a BKN layer around 15-25 kft.

KPDX AND APPROACHES...VFR expected to continue through Wednesday night. Northwest winds 7-10 kt decrease after 06z Thu then shift southerly by 12-14z Thu. There's a 20-30% chance of MVFR cigs due to marine stratus developing between 12-16z Thu. If this does occur, conditions should improve to VFR by 18-21z Thu. There's a 15-20% chance of elevated showers or thunderstorms between 12-18z Wed with main concern frequent lightning and brief gusty and erratic winds. -03

MARINE

Benign conditions with a typical summertime pattern expected through the week. Northerly winds 10-15 kt expected with afternoon gusts reaching to around 20 kt each day. Seas could be choppy at times with heights 4-6 feet but could see some 7 foot seas at 8-10 seconds. There is a 30-60% chance for Small Craft Advisory (SCA) criteria winds for all waters Saturday afternoon into Sunday.

A SCA is in effect Thursday morning from 4 AM to 10 AM for rough seas within the Columbia River Bar due to a very strong ebb current leading to seas of 6 to 8 ft. -19/03

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 4 AM to 10 AM PDT Thursday for PZZ210.