Preview of NWS' New Version of Forecast
This preview is not operational and should not be used for support decisions.

Area Forecast Discussion (AFD)

Issued by Seattle/Tacoma, WA (SEW)

FXUS66 KSEW 192216

Area Forecast Discussion
National Weather Service Seattle WA
315 PM PDT Tue Mar 19 2019

.SYNOPSIS...A strong upper level ridge and offshore surface flow 
will give one more sunny and warm day. Record highs are likely 
Wednesday. Offshore flow will weaken on Thursday resulting in lower 
temperatures. A front will spread light rain northeast across the 
area on Friday. There will be a chance of showers next weekend with 
near normal temperatures.


.SHORT TERM /TONIGHT THROUGH FRIDAY/...More high temperature records 
fell today under sunny skies and a brisk east wind. Mid 70s to low 
80s were pretty common. It's a real scorcher, for March. SeaTac
reached 79 by 3 PM, making it the hottest March 19, hottest March 
day, and hottest winter day, ever.

Offshore surface flow will keep things toasty Wednesday with the 
thermal trough right over Puget Sound. The forecast high is 76, 
another record. On Wednesday the coast will have a bit of onshore 
surface flow, and highs there will be around ten degrees lower than 

As offshore flow decreases Wednesday night into Thursday, a weak 
southerly surge will develop over the Oregon coast and move north. 
This will give some late night and morning stratus to the coast and 
portions of the interior and will result in lows dropping more 
uniformly into the 40s. Southerly flow aloft may allow isolated 
showers over southern sections in the afternoon and evening. Highs 
on Thursday will still be well above normal in the interior, in the 
mid 60s, but nearer normal on the coast, in the mid 50s.

On Friday a negatively tilted trough, meaning one that is weakening, 
will move inland. This will spread light rain onto the coast in the 
afternoon and inland Thursday evening. Burke

.LONG TERM /SATURDAY THROUGH TUESDAY/...Showers will follow on 
Saturday. Models are generally dry on Sunday, then more weak systems 
arrive Monday and Tuesday. Have generally followed the models as far 
as pops. Temperatures will still be a few degrees above normal each 
day, with highs generally 55-60. Burke


.AVIATION...Low level offshore flow continue into tonight as an area 
of surface high pressure resides east of the Cascades. The air mass 
will be dry and stable with southeasterly flow aloft. VFR 
conditions. Gusty easterly surface winds will persist across 
portions of the southern Sound through this evening, breezy 
elsewhere. Gusts generally up to 28 knots at KSEA and KHQM with 
offshore flow.

KSEA...VFR conditions continue. Easterly winds 10-20 knots through 
this evening with gusts generally up to 28 knots. Winds will subside 
into the overnight hours after 05z with northeasterly winds 5-15 
knots. JD


.MARINE...Offshore flow will persist into Wednesday afternoon with 
an area of high pressure east of the Cascades. Breezy winds near the 
gaps of the coastal terrain. Strongest easterly winds will be along 
the Central Strait of Juan de Fuca. Light onshore flow developing on 
Thursday ahead of a weakening front spreading into the region on 


.HYDROLOGY...River flooding is unlikely over the next seven days.


PZ...Small Craft Advisory until noon PDT today for Coastal Waters 
     From James Island To Point Grenville 10 To 60 Nm-Coastal 
     Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater Out 
     10 Nm.

     Small Craft Advisory until 8 PM PDT this evening for Central 
     U.S. Waters Strait Of Juan De Fuca-Coastal Waters From Cape 
     Flattery To James Island Out 10 Nm-West Entrance U.S. 
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 2 PM PDT this afternoon for Coastal 
     Waters From Cape Flattery To James Island 10 To 60 Nm.