National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Portland, OR

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-- Discussion containing changed information from previous version are highlighted. --783FXUS66 KPQR 132232AFDPQRArea Forecast DiscussionNational Weather Service Portland OR332 PM PDT Thu Jun 13 2024.SYNOPSIS...
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High pressure today will give way to a low pressuresystem this weekend. Friday will be the transition day withstrengthening onshore flow and a slight chance (20%) of thunderalong the north coast. This low pressure system will be the nextweather maker bringing showers, and southwesterly flow. Cannotrule out another round of thunder north of Salem on Saturdayinto Sunday. Persistent showers through early next week..SHORT TERM...Now through Friday Night...High pressure shiftsinland tonight and low pressure system drops down from thenortheast Pacific. The combination of these two features willincrease onshore flow in the evening. The pressure gradientbetween Troutdale and the Dalles is around 5 mb which isindicative of strong westerly flow. Based on today`s windspeeds and how that pressure gradient compares to the forecasttomorrow, have increased wind speeds through the Columbia RiverGorge around Cascade Locks and the Upper Hood River Valley.Ultimately, weather on Friday will be uneventful with nearnormal temperatures - though on the cooler side.Friday night the low will begin it`s advection inland whichcoincides with an upper level jet streak. The NBM is suggestingaround a 20% chance of thunder over the north Oregon/southWashington coast and Coast Range in the afternoon. Very fewmodels are showing a true sign of this with minimal CAPE andinstability. However, the orographic lift with a slightsouthwesterly flow will enhance convective potential. Showerchances look to be generally confined to areas along and northof a Lincoln City- Portland-Mt St Helens line through Fridayevening before more widespread shower activity spreads acrossthe area Friday night. Model QPF remains on the light sideFriday through Saturday morning. -Muessle.LONG TERM...Saturday through Wednesday...Minimal change in thelong term forecast as models appear to be generally inconsensus. On Saturday, the onshore flow intensifies from thesouthwest which may promote more convective potential. Thistime, the convection could be more widespread. The NBM broughtin a 30-40% chance for thunderstorms in southwest Washington onSaturday. However, areas aside from the Cascades wills struggleto see enough "oomph". Decided to lower chances forthunderstorms. Even if they do occur, not looking at any majorimpacts. Ensembles show broad troughing from Sunday nightthrough Tuesday. Cool temperatures and isolated scatteredshowers through mid-week.Once we make it through this troughing and showery weather,ridging is possible which will bring warmer and drier weatherour way. -Muessle
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VFR conditions persist under mostly clear skies.North/northwesterly flow with winds generally below 10 kt forinland locations. Winds along the coast are slightly stronger withgusts through the evening up to to 20 kt through around 03ZFriday. A weak frontal passage around 10Z Friday will bringsoutherly winds to the coast along with a the 25%-35% probabilityfor MVFR/IFR conditions to develop along the coast. Could also seesome very light rain showers as well.Guidance is also suggesting that this weak front could push marinestratus around the Coast Range as well as down the ColumbiaRiver. If this happens could see some MVFR conditions (15-20%probability) stating around 12Z-15Z Friday for KPDX and KEUG.Will be leaving the MVFR conditions for inland locations out atthis time as the probability is minimal.PDX AND APPROACHES...VFR under clear skies. Northwesterly windsup to 10 kts. Weak frontal passage around 12Z-14Z Friday willresult in a 10-20% probability MVFR marine stratus, pushed alongthe Columbia River impacting areas on or near the terminal.However, will be leaving the MVFR conditions out of the currentTAF package as the probability is minimal. -42
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Small Craft Advisory linger through this evening forzones PZZ252, PZZ253, PZZ272 and PZZ273 with northerly wind gustsup to 25 kt. Seas around 4 to 6 ft at 9 to 11 seconds throughSaturday afternoon. A weak front, late tonight/early Friday willbe the signal for an upcoming pattern change late Friday and intothe weekend. Expect southerly winds tonight and into Fridaymorning, before the stronger front late Friday will bring a returnto relatively stronger, westerly winds across all waters. Seaswill slowly build through Saturday towards 5 to 7 ft on Sunday,before subsiding again towards 4 to 6 ft by the start of theupcoming week. -42
-- End Changed Discussion --&&.PQR WATCHES/WARNINGS/ADVISORIES...OR...None.WA...None.PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ251>253-271>273.&&$$www.weather.gov/portlandInteract with us via social media:www.facebook.com/NWSPortlandwww.twitter.com/NWSPortland