Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
609 FXUS66 KSEW 251044 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 344 AM PDT Wed Sep 25 2024 .SYNOPSIS...A weather system will move across the region today, bringing more widespread rain, breezy winds, and chances of isolated thunderstorms to western Washington. Another system will move into the region Thursday evening into Friday, bringing another round of rain and gusty winds. Conditions will then dry out over the weekend. Additional, weaker systems may move into the area early next week. && .SHORT TERM /TODAY THROUGH FRIDAY/...A fall-like weather system will move across western Washington today. Radar shows a pre- frontal band of rain already making its way inland along the coast and pushing into portions of the Northern Interior early this morning. Expect rain to continue to make its way inland through the morning and afternoon hours as the main frontal system moves through the area. Rain will taper to showers by this evening, with increased onshore flow in the wake of the front allowing for a convergence zone to develop across King/Snohomish counties. Southerly winds will become breezy across the region in the vicinity of the front. The airmass will also be slightly unstable, so some isolated thunderstorms will be possible throughout the day. Rainfall amounts generally look to range from a quarter of an inch to half an inch across the interior lowlands, half an inch to three quarters of an inch for the coast, and 1-2 inches for the mountains. High temperatures will be in the 60s area-wide. Expect a brief break in the weather on Thursday before the next system moves in Thursday night into Friday. Rainfall amounts generally look to trend lighter than that of the system today, with most areas across the lowlands expected to receive a few tenths of an inch to a quarter of an inch. Amounts look to be higher along the North Coast, Olympics, and North Cascades- where amounts of half an inch to an inch will be possible. This system looks to bring more widespread breezy southerly winds to the region, with the highest gusts likely being along the North Coast and areas north of Everett - where gusts to 35 mph will be possible. Temperatures will generally trend in the 60s to low 70s both Thursday and Friday. .LONG TERM /SATURDAY THROUGH TUESDAY/...Weak upper level troughing looks to set up over the region over the weekend. With not much in the way of moisture or forcing, the weekend generally looks to remain cool and mostly dry. Cannot rule out a few light isolated showers, however, so will need to continue to monitor how guidance trends throughout the week. High temperatures generally look to trend in the 60s, with overnight lows expected to be in the 40s and 50s. Additional weak disturbances may move across the region early next week and bring additional chances of showers at times. 14 && .AVIATION...Southwest flow aloft will increase into early Wednesday as a frontal system moves across the area. Generally a mix of flight conditions this morning with the approaching front. Expect mostly IFR conditions along the coast as the front approaches with VFR ceilings across the interior continuing to lower. Expect rain to increase as the front pushes inland with visibilities decreasing to 2-5 miles in rain. A convergence zone is also expected to develop over Snohomish and King counties into Wednesday evening. Increasing south/southwest surface winds through the day, with gusty conditions especially along the coast and far north. KSEA...VFR conditions this morning with gradually lowering ceilings as the front approaches. Still some potential (around 25%) for brief IFR ceilings around 13z for a few hours, but the more likely scenario is steadily lowering MVFR ceilings through the morning. The front will bring rain across the terminal area 17-22z with a developing PSCZ to the north of the terminal into Wednesday evening. This should maintain southerly surface winds at the terminal most of the day, with gusts increasing late morning through afternoon. Currently not expecting a significant shift to northerly winds with the convergence zone remaining north this evening. Cullen && .MARINE...An approaching front will continue to advance across the coastal waters this morning. Expect breezy southerly winds ahead of the front to increase, followed by northwest winds behind the front as it pushes inland. Winds gusts ahead of the front may occasional gusts around 20-25 kt, but these aren`t expected to be frequent or widespread enough for an advisory. However, an advisory has been issued for the outer coastal waters with seas increasing to around 9 to 11 feet through the day today as this system pushes eastward. The next disturbance will then be quick to follow, with a deeper low strengthening and curling north toward Haida Gwaii on Thursday. Expect a more widespread swatch of gusty southeasterly winds ahead of the front as the cold front sweeps through the coastal waters and inland, following by a stronger round of west winds through the Strait of Juan de Fuca. This will bring around a 40% chance of gales through the Strait as the onshore flow surges through. Meanwhile, seas over the coastal waters will increase more significantly into the 13 to 16 ft range (highest over the outer coastal waters) on Friday. Cullen && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory from 9 AM this morning to midnight PDT tonight for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 4 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-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm. && $$