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Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
144 FXUS66 KSEW 112203 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 303 PM PDT Sun Aug 11 2024 .SYNOPSIS...Upper level troughing over the region will promote onshore flow and cooler temperatures the next several days. Isolated thunderstorms will be possible across the North Cascades this evening and again Monday. More widespread chances of precipitation may return to western Washington by next weekend. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Current satellite imagery does show stratus still draped across portions of the interior this afternoon. Stratus has been slow to scatter, but will continue to do so through the afternoon hours to make way for some spots of sun across the interior lowlands. Stratus does not look to clear near the coast, however. Temperatures this afternoon have been trending in the 60s to near 70 across the majority of the region and look to top out in the mid 60s to low 70s for most spots. Slight chances of thunderstorms remain possible across portions of the North Cascades this afternoon and evening. Upper level troughing will persist over the area through the first half of the week, generally promoting cooler and cloudier conditions across western Washington. Expect additional rounds of marine stratus to push inland during the overnight and early morning hours the next few days. Afternoon high temperatures will generally top out in the 60s and 70s. Some isolated thunderstorm chances will still be possible for portions of the North Cascades on Monday afternoon and evening, with probabilistic guidance indicating a 10-15% chance of thunderstorm development across the far northern areas near the Cascade crest and border. Chances across the Cascades really wane heading into Tuesday as the threat shifts further off to the east. .LONG TERM /THURSDAY THROUGH SUNDAY/...Upper level troughing will remain the dominant influence across the Pacific Northwest through the long term period. Another low dropping down into the region from Canada late in the week could bring more widespread shower chances back to western Washington by the weekend, however will need to see how guidance continues to trend with this over the coming days. High temperatures on Thursday look to trend closer to normal for right now (in the mid to upper 70s), with temperatures dipping to below normal (upper 60s to low 70s) again Friday into the weekend. && .AVIATION...West to southwest flow aloft with upper level troughing over western Washington. Marine stratus has been very slow to evaporate today with MVFR to IFR conditions continuing at all the area terminals. Satellite shows evaporation progressing northward from the south, but has not budged through the North Interior. At this rate, is it a possibility that some areas may not clear out at all today. However, expecting slow ceiling improvement in the interior continuing through 00Z Monday and into the early evening for a brief return to VFR conditions. The is not expected to clear out tonight. Stratus will redevelop again tonight for a return to IFR and locally lower ceilings through Monday morning. Improvement again tomorrow looks to be slow and ceilings linger into the afternoon. Winds will remain west-southwesterly 5 to 10 kt throughout the TAF period. KSEA...Conditions are now VFR at the terminal with marine stratus slowly evaporating from south to north as it lingers near the area. VFR conditions should remain through this afternoon and evening. Marine stratus and IFR ceilings look to return overnight and remain through the morning, slowly lifting and evaporating by the afternoon Monday. Winds remain southwesterly 5 to 10 kt. LH && .MARINE...Broad high pressure over the East Pacific with low pressure inland will maintain northwesterly onshore flow over the area waters. Diurnally driven pushes down the Strait of Juan de Fuca will occur each evening. Currently winds look to remain below any thresholds through the upcoming week. Seas 6 to 8 ft at 8 seconds will ease tonight, which will allow the Small Craft Advisory to expire later this afternoon. Seas subside Monday back to 3 to 5 ft and remain like so through the week. LH && .FIRE WEATHER...Elevated fire weather conditions will persist through this evening across portions of the North Cascades as another shortwave trough brings the potential for thunderstorm development. Coverage across the western slopes looks to be less than that of the previous days, however any thunderstorms that do develop may produce frequent lightning, brief heavy downpours, hail, and gusty and erratic winds. Isolated thunderstorms will be possible across the North Cascades on Monday afternoon and evening again, however probabilities continue to wane as the greatest threat moves off to the east. Broader troughing setting up over the region this week will promote increased onshore flow and good relative humidities across the region. Apart from the isolated thunderstorm threat in the far northern Cascades on Monday, this overall trend will help to alleviate fire weather conditions through at least midweek. 14 && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory until 5 PM PDT this afternoon for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From James Island To Point Grenville 10 To 60 Nm. && $$