Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
797 FXUS66 KSEW 281516 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 816 AM PDT Tue May 28 2024 .UPDATE...Widespread rainfall will continue to move onshore throughout the morning as a weak front crosses western Washington. Conditions will destabilize in the afternoon with precipitation becoming more showery, with Puget Sound convergence zone activity continuing into the evening and early morning hours Wednesday. The current forecast is on track with no updates to the forecast this morning. && .SYNOPSIS...A cold front will cross western Washington today with a quick round of widespread rainfall, which will decrease into showers through the day Wednesday. A shortwave ridge and surface high to our south will bring warmer and drier conditions. A warm front will slowly lift across the Pacific Northwest late Saturday into Sunday with another series of weak frontal systems looking to move across the region into early next week. && .SHORT TERM /TODAY THROUGH THURSDAY/...Rain continues to move towards the coast this morning on radar in association with an incoming cold/occluded front. This will bring a brief period of stratiform rain to most of the area as the front passes across western Washington today. High temperatures on the cool side in the mid to upper 50s, some 10 degrees below normal for late May. This front continues to skirt eastward into Wednesday morning with rain transitioning to showers, favoring the typical Puget Sound Convergence Zone-affected areas in central Snohomish County. HREF member consensus redevelops this PSCZ along the King and Snohomish County line early Wednesday afternoon. Low-topped convection is possible once again thanks to the upper-level trough axis moving overhead with anomalously cold 500 mb heights around -25C. The best chance for any thunder will be in the convergence zone over this area, though the probability for thunder only tops out around 20% with maximum SB CAPE only at 200 J/kg. Primary hazards with any isolated thunderstorms that do form will be small hail and brief gusty winds. High temperatures Wednesday once again in the upper 50s to near 60 into the Southwest Interior. Shortwave ridging builds inland Thursday with surface high pressure centered well off the northern California coast. Drier conditions return Thursday with highs warming into the low to mid 60s. .LONG TERM /FRIDAY THROUGH MONDAY/...High pressure keeps dry and mild conditions in place Friday with highs finally returning to seasonal normals. The ridge axis shifts to our east through the weekend as a deep vertically-stacked low forms over the Gulf of Alaska, ejecting a series of shortwaves northeastward across the Pacific Northwest into early next week. Long range ensemble consensus keeps wet pattern in place into early next week with the several inches of QPF possible across the Olympics and Cascades Sunday and Monday (60% chance for 2 inches or more of liquid precipitation accumulation). High temperatures look to favor the mid to upper 60s into early next week as well. Davis && .AVIATION...An upper level trough will pass through today with a weakening cool front/surface trough. Flow aloft is southwesterly and will transition to west/northwesterly once the trough passes early Wednesday. Light rain bands are currently present with this disturbance already this morning, and will continue to spread across the terminals this morning and afternoon. This will bring ceilings down to MVFR this morning through early this afternoon. Additionally, post-frontal convergence zone activity is possible this afternoon and evening from Snohomish county northward. This may cause a change in wind direction to the west/northwest for terminals around and north of KPAE. At this time, the wind shift is not expected to track any further south (based on guidance) - but will continue to monitor in case the convergence zone develops further south. Winds for remaining terminals will remain out of the southwest to day at 8 to 12 kt (gusts to 20 kt possible with the precipitation). KSEA...Broken/overcast ceilings have lowered to MVFR this morning ahead of rain showers. Expect a return to VFR after the the disturbance passes late this afternoon/evening. Winds will remain out of the southwest 8 to 12 kt (gusts to 20 kt possible late this morning/afternoon). HPR && .MARINE...A weak front will move onshore late this morning with increasing onshore flow in its wake. This will lead to small craft advisory westerlies in the central/east strait this afternoon and evening. Broad surface ridging builds over the coastal and offshore waters on Wednesday with a likely repeat of afternoon and evening small craft advisory westerlies in the strait. The combination of surface ridging offshore and lower pressure inland will maintain onshore flow through the remainder of the week. The onshore flow will weaken somewhat by Friday as high pressure aloft moves over the area. Another weak front is expected to arrive on Saturday. 27/HPR && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory from 2 PM this afternoon to 2 AM PDT Wednesday for Central U.S. Waters Strait Of Juan De Fuca- East Entrance U.S. Waters Strait Of Juan De Fuca. && $$