Sunrise 5:46 AM   Sunset 7:56 PM Moonrise 11:24 PM   Moonset 6:47 AM

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FXUS66 KPQR 262234 AFDPQR

Area Forecast Discussion National Weather Service Portland OR 334 PM PDT Fri Apr 26 2024

SYNOPSIS
Showery and unsettled conditions continue through the weekend into next week as the Pacific Northwest remains under the influence of a rather progressive spring-time weather pattern. Beyond the more persistent chances for rainfall going forward, snow levels are expected to fall as low as 2500-3000ft on Monday with good chances(65-95%) light snow accumulation(>1")
across the the Cascades through Tuesday morning. Model uncertainty increases significantly by the middle to end of the week, however, latest runs continue to trend towards the potential(60%)
for at least a brief period of drier conditions centered around Wednesday.

SHORT TERM
Tonight through Monday...The axis of the upper- level trough overhead responsible for our ample shower activity around the region this afternoon has begun shifting east into the Cascades. Expect showers to gradually decreasing later tonight, as the airmass begins to stabilize in response to weak transitory ridge of high pressure currently offshore shifting inland. That said, the arrival of fast moving frontal boundary extending southward off a parent low located over the gulf of Alaska increases chances for precipitation Saturday late morning and afternoon.With the rather fast movement of this feature, overall rainfall amounts will not be all that much with the NBM still indicating around 0.10 to 0.25 inch, with heaviest along the coast. As usual, bit higher amounts over the higher terrain, with 0.25 to 0.50 inch in spots of the Coast Range/Willapa Hills and Cascades.

Saturday night through Sunday we'll return back to a cooler and showery weather pattern under broad zonal flow. The airmass filtering in aloft likely drives snow levels back around 4500ft by Sunday afternoon although the timing of this decrease likely means a lack of impacts for the Cascade passes, at least initially - this changes come Monday. It's worth mentioning dropping upper-level temperatures and daytime heating has a slight chance(15-25%) to produce convective showers robust enough to produce a lightning strike or two Sunday afternoon as indicated by deterministic model soundings. Come Sunday night into Monday a quick moving upper-level shortwave trough races into the Pacific Northwest accompanied by a cold- frontal boundary leading to yet another increase in precipitation chances and snow- levels lowering further by Monday morning to 2500-3000ft. While the current thinking is snowfall at this elevation will largely be slush in the grass, if anything sticks at all, higher locations around and above 4000ft including our mountain passes have a much better chance(75-95%) to see wet snow accumulation and potential minor travel impacts through Monday night. -Schuldt

LONG TERM
Tuesday through Thursday...Overall confidence is low to moderate the pattern stays rather progressive into late next week - deterministic and ensemble guidance struggle resolving the longitudinal placement of ridge/trough features going forward. Showers are expected to linger on Tuesday as snow levels hold somewhere between 2500-3500ft. Wednesday guidance has continued to trend a little drier nudging a larger scale upper-level low further north while a transient ridge glides over the region. Out of all the ensemble solutions available, this scenario is present in roughly 60% of them in addition to the latest deterministic ECMWF and GFS. Past this point model uncertainty becomes truly significant with nearly a 50/50 split between maintaining a ridge feature overhead or bringing a potent trough into the region by Thursday. Hopefully in the coming forecast runs guidance begins to show better agreement resolving the pattern mid to late week. Current confidence in the forecast by Thursday is low. -Schuldt

AVIATION
Showers weaken going into Friday night as the last trough pushes through the area. The majority of the night should generally see VFR conditions inland and MVFR at the coast. Inland areas only see around a 20-30% chance of brief MVFR ceilings during this time. The next front arrives Saturday morning around 13z, though prefrontal rain could begin dropping ceilings back to MVFR thresholds as early as 03z. Winds slowly turn westerly, with top gusts up to around 15 kt for the rest of the TAF period.

Notes: The ASOS at KTTD is only available via the dial in option.
The AWOS at KMMV is still out of commission. There is no estimated time of repair.

PDX AND APPROACHES...Brief break in precipitation has allowed for mostly VFR conditions at the moment. MVFR conditions return around 03z, with 50-60% chance of MVFR ceilings between 03-13z.
Afterwards, higher confidence (80%+) in MVFR ceilings as the next front pushes in. /JLiu

MARINE
Post-frontal conditions persist resulting in steep and choppy seas. Winds are slowly shifting southwesterly, with weaker winds between 10 to 20 kts expected this evening. Winds will briefly dip in the latter half of Friday night, and the Small Craft Advisory for the rest of Friday will primarily be for steep and choppy seas around 7 to 10 ft at 8 to 10 seconds. Winds will begin rising again and turning southerly Saturday morning with the next front. Gusts up to 25-30 kt will be possible throughout Saturday daytime hours. Model guidance continues to decrease the chance of gales on Saturday, and is currently <10%. /JLiu



PQR WATCHES/WARNINGS/ADVISORIES
OR...None.
WA...None.
PZ...Small Craft Advisory until 8 PM PDT Saturday for PZZ210-251>253- 271>273.

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