textproduct: Portland

SYNOPSIS

A frontal system will bring widespread rain, breezy winds from the south, and a 15-20% chance for thunderstorms today. Rain continues tomorrow with a 20-30% chance for thunderstorms. Any passing thunderstorms may produce lightning, heavy rain, gusty erratic winds, small hail, and/or a funnel cloud. Chances for lingering showers continue through the weekend with cooler than average temperatures. Drier conditions early next week.

LONG TERM...Saturday through Tuesday

Over the weekend, the majority of ensemble members continue to show broad upper-level troughing over the Pacific Northwest. However, there is uncertainty with whether or not we remain dry or continue with lingering showers. While 60% of ensemble members suggest showers continuing over the region Saturday-Sunday, the other 40% keep us dry. What we can say with higher confidence is that this upper-level low will maintain below-average 500 mb heights and keep high temperatures slightly cooler than average for this time of year. Early next week, the majority of ensemble members show the upper low weakening and beginning to move eastward. This would favor drier conditions, but there remains uncertainty with how much high pressure will re-build over our area, and how warm/dry we get. -10

AVIATION...Through 06Z Friday

Rain has mostly stopped across the area as of 05Z Thu, however expect shower activity to increase towards 08-13Z Thu as post-frontal showers drift northeastward into the airspace. Rain showers will gradually return from north to south, with the latest arrival around 13Z Thu at KEUG. Any stronger showers could temporarily knock conditions back to MVFR or lower through Thursday morning. Probabilistic guidance currently suggests a 15-40% chance of MVFR conditions at any given hour during the TAF period. Additionally, there is a 20-35% chance for thunderstorms Thursday afternoon at all terminals, with the highest chances along the coast. Any thunderstorms that develop will have the potential to produce lightning, small hail, and gusty/erratic winds.

Southerly winds will continue through the TAF period, expected to ramp up to around 9-15 kt sustained winds with gusts around 20-25 kt between 08-23Z Thu. Winds will weaken beyond 00Z Fri and potentially shift more southwesterly at some terminals.

KPDX AND APPROACHES...Expect rain showers and VFR conditions to continue through the TAF period. There is a 10-30% chance of MVFR CIGs between 09-23Z Thu, with the highest chances around 12-17Z Thu. Expect an isolated thunderstorm threat Thursday as well, mainly during the afternoon hours (most likely between 17Z Thu and 00Z Fri). ~12

MARINE

Current seas around 9-11 ft at 8-10 seconds will continue into Thursday as a fresh west/northwest swell overnight into Thursday maintains conditions. Due to the continued sea state and breezy winds, a Small Craft Advisory is in effect through Thursday afternoon into the evening. There'll also be 15-30% chance for thunderstorms tonight through Thursday with the best relative chances Thursday afternoon. Any of these storms will be capable of producing gusty/erratic winds, small hail, and lightning.

While relatively active weather with lingering rain showers will continue into the weekend, marine conditions will subside by Friday with seas holding in the 4-6 ft range by Friday afternoon. Similar conditions persist into early next week while winds occasionally gust to 15-20 knots. ~12/99

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 5 PM PDT Thursday for PZZ210-251-252- 271-272.

Small Craft Advisory until 11 PM PDT Thursday for PZZ253-273.