Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
430 FXUS66 KSEW 291040 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 340 AM PDT Sat Jun 29 2024 .SYNOPSIS...Southwesterly flow aloft today with upper level ridge well to the east and a weakening front moving into the area late in the day. Front dissipating tonight. Upper level trough moving through Sunday keeping a chance of showers in the forecast. Upper level ridge building offshore Monday will drift slowly eastward moving over the area Thursday and Friday. Warmest day of the year possible Friday. && .SHORT TERM /TODAY THROUGH MONDAY/...Satellite imagery shows middle and high level clouds moving across Western Washington early this morning. Front offshore near 130W. Cloud cover keeping temperatures on the mild side at 3 am/10z, in the mid 50s to lower 60s. Middle and high level clouds continuing to stream over the area this morning. Clouds thickening up this afternoon with the front close enough for a chance of showers west of Puget Sound in the afternoon. Air mass somewhat unstable over the Cascades and with increasing middle level moisture ahead of the front could see a shower there as well in the afternoon. Highs in the mid 60s along the coast and upper 60s to mid 70s inland. What is left of the front moving inland tonight giving most of the area a chance of showers this evening. With the front lifting to the northeast the chances for showers will linger over the northern portion of the area after midnight. Like this morning, with plenty of cloud cover low temperatures will be mild, in the mid 50s to lower 60s. Weak upper level trough behind the front moving through Sunday keeping at least mostly cloudy skies and a chance of showers in the forecast. Trough axis moving through midday. Increasing onshore flow behind the trough axis with a convergence zone developing over Snohomish county in the afternoon. Little change in the high temperatures with mid 60s coast and upper 60s to mid 70s inland. Upper level trough continuing to move east Sunday night. Chance of showers becoming confined to the Cascades and the convergence zone over Snohomish county in the evening. Convergence zone will last into the morning hours Monday. Outside of the Cascades and convergence zone some clearing Sunday evening but with the low level onshore flow clouds will fill back in overnight. Lows in the 50s. Weak trofiness over Western Washington Monday morning with 500 mb heights rising in the afternoon as an upper level ridge begins to build offshore. The combination of weak trofiness and a dying convergence zone will keep a chance of showers in the morning from about Snoqualmie Pass northward. Morning clouds over the lowlands giving way to afternoon sunshine with the subsidence from the upper level ridge building taking care of the morning marine layer. Highs once again in the mid 60s along the coast and upper 60s to mid 70s inland. .LONG TERM /TUESDAY THROUGH FRIDAY/...Extended models in good agreement with what looks like the beginning of the summer pattern setting up over the Pacific Northwest through the period. Upper level ridge offshore slowly drifting east ending up over Western Washington Thursday and Friday. Low level onshore flow Tuesday and Wednesday weakening Thursday and Friday. Low level flow never really turns offshore late in the week. 500 mb heights peaking around 590 dms Thursday into Friday. 850 mb temperatures in the single digits Tuesday warming to near plus 20C by Friday. With temperatures aloft this warm even without offshore flow warmest locations will be pushing 90 degrees Friday. Areas of morning clouds with afternoon sun Tuesday and Wednesday. Mostly sunny Thursday and Friday. Highs Tuesday in the mid 60s along the coast with upper 60s to mid 70s inland. Highs a couple of degrees warmer Wednesday and Thursday. By Friday, highs in the 70s along the coast and upper 70s to near 90 inland. Felton && .AVIATION...Southwesterly flow aloft today with upper level ridge well to the east and a weakening front moving into the area late in the day. Front dissipating tonight. Upper level trough moving through Sunday. Just some middle and high clouds this morning. Ceilings lowering this afternoon along the coast down to around 5000 feet early afternoon and to 1000-1500 feet by early evening. For the interior ceilings lowering to around 5000 feet in the early evening and down to 1000-2000 feet by midnight. MVFR ceilings continuing into Sunday morning. KSEA...Just some middle and high level clouds through 00z this afternoon. Ceilings lowering to around 5000 feet this evening and to 1000 to 2000 feet 05z-08z. MVFR ceilings continuing into Sunday morning. Light northerly winds, less than 6 knots, becoming south southwesterly 15z-18z. Felton && .MARINE...A weak frontal system will move through the coastal waters today reaching the inland waters late. The front will dissipate over the inland waters tonight. High pressure building offshore Sunday. High pressure over the coastal waters with lower pressure inland will continue into mid week. Small craft advisory westerlies possible Sunday evening in the Central and Eastern Strait of Juan de Fuca with a better chance for small craft westerlies Monday evening. Felton && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$