Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version |  Previous Version |  Text Only |  Print | Product List |  Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
934 FXUS66 KSEW 241055 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 355 AM PDT Fri May 24 2024 .SYNOPSIS...
-- Changed Discussion --
Cooler and unsettled conditions return today and will persist into Saturday as an upper level trough moves across the region. Upper level ridging then looks to build into the Interior West early next week, however troughing over the northeastern Pacific will continue and will bring additional chances of precipitation across western Washington at times.
-- End Changed Discussion --
&& .SHORT TERM /TODAY THROUGH SUNDAY/...
-- Changed Discussion --
Cooler and unsettled conditions return today as the next upper level trough drops down into the region from British Columbia. Radar this morning shows showers moving inland along the coast ahead of a surface low and its associated frontal system. Expect showers to continue to push inland throughout the day and persist into Saturday. Onshore flow will increase in the wake of the frontal system Friday night into Saturday and high-resolution models continue to hint at a convergence zone developing across the central Sound overnight into Saturday. Overall, expect precipitation amounts to remain rather light as this system moves across the region, with most lowland locations looking to receive a tenth to a quarter of an inch. A few spots, primarily in the vicinity of the convergence zone and across the northern Sound, may see some higher rainfall amounts -most likely towards half an inch in any heavier showers. Amounts across the mountains are generally expected to be 0.50-1.25 inches through Saturday. High temperatures today and Saturday will be below normal, likely topping out in the mid to upper 50s for much of the area. Upper level ridging will start to build across the Interior West on Sunday, however western Washington will continue to be influenced from upper level troughing over the northeastern Pacific. A warm front moving into British Columbia looks to brush the region, likely bringing another round of showers to portions of the coast and areas from Snohomish County northward. Areas across the central and southern Sound look to remain drier and afternoon highs look to warm a few degrees, generally topping out in the upper 50s to low 60s. Highs along the coast will remain cooler and look to remain in the 50s. Precipitation amounts generally look to remain light, with most spots only looking to receive a few hundredths of an inch of rain. The exception is the Northern Coast, which could pick up 0.25 to 0.50 inches of rain. .LONG TERM /MONDAY THROUGH THURSDAY/...Ensembles and deterministic guidance are in good agreement that upper level ridging will continue to build across the Interior West early next week. Meanwhile, upper level troughing over the northeastern Pacific will continue to influence western Washington and will keep shower chances in the forecast, especially for portions of the coast and Northern Interior. Precipitation chances then look to increase Tuesday as another cold front moves across western Washington. Uncertainty increases mid to late week as guidance continues to struggle with the position of the upper level ridge and trough. Have kept mention of slight chances of showers in the forecast for now, though will have to see how guidance trends going forward. High temperatures look to trend in the 60s.
-- End Changed Discussion --
&& .AVIATION...
-- Changed Discussion --
Westerly flow aloft turning more northwesterly through the day Friday with onshore flow at the surface. Some lowering clouds from west to east ahead of an approaching front, with a mix of MVFR and VFR conditions expected toward daybreak. Rain pushing onshore 13-16z before slowly reaching Puget Sound toward 21z. KSEA...Southerly surface winds and increasing clouds this morning. Expect lower VFR ceilings giving way to MVFR conditions toward 16z. Shower chances increase from 21z onward, with mostly MVFR conditions and southerly winds continuing through the remainder of the period.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
An approaching front will bring increasing winds and steep seas over the coastal waters later today. Expect the most widespread advisory strength winds beyond 10 nm from shore, but occasional gusts to 25 kt are possible into the inner waters. Meanwhile, expect seas to build into the 7 to 10 ft range by tonight with dominant periods generally 8 or 9 seconds. As a result, a small craft advisory has been issued to cover the coastal waters. A modest push down the Strait of Juan de Fuca this evening will be followed by a stronger push of westerlies Saturday morning. This may need an advisory with more solid winds expected. The next frontal system will move into B.C. on Sunday with increasing southerly winds. Seas over the coastal waters generally hold around 5 to 6 feet during the early part of next week.
-- End Changed Discussion --
&& .SEW WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
WA...None. PZ...Small Craft Advisory from 7 PM this evening to 8 AM PDT Saturday for Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. Small Craft Advisory from 2 PM this afternoon to 8 AM PDT Saturday 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.
-- End Changed Discussion --
&& $$