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Area Forecast Discussion (AFD)

Issued by Seattle/Tacoma, WA (SEW)

                            
000
FXUS66 KSEW 242159
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
259 PM PDT Fri May 24 2019

.SYNOPSIS...An upper level low will bring isolated showers to the
region tonight. Another low drops south for Saturday with more 
widespread chances for showers. Drier and warmer weather expected 
for the lowlands for next week with chances for showers and 
isolated thunderstorms in the mountains through Memorial Day. 

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...Strong onshore flow
resulted in a much cooler air mass across western Washington
today. Temperatures were mostly in the 50s to lower 60s this
afternoon, compared to the 70s we saw on Thursday. An upper level
low will cross the region this afternoon and evening for a chance
of showers, mainly in the interior and Cascades. 

Cool and showery weather will continue on Saturday as another
upper level low spins over the region. Temperatures will be
similar to what we are seeing today - highs near 60 degrees. 

The upper level low will exit south on Sunday, but we may see some
wrap-around showers clipping the Cascades. Otherwise, onshore 
flow is weaker for less cloud cover and warmer temperatures. 

We're looking warmer for Memorial day as temperatures reach the
low to mid 70s in the interior. The coast will remain cooler and
in the 60s. There's a chance of showers and isolated thunderstorms
in the Cascades, where instability is the greatest. 33

.LONG TERM /TUESDAY THROUGH FRIDAY/...Weak high pressure will
provide dry weather as we move through next week. At the surface,
low level onshore flow will prevail. We'll likely see morning
clouds each day then some clearing and sunbreaks in the afternoon.
The pattern breaks down late in the period, next Friday and
Saturday, as the flow turns more zonal and a trough moves in. 33

&&

.AVIATION...Upper level low over the area will keep winds generally 
northerly through tonight as the upper low swings to the south. 
Onshore flow will continue through Saturday. MVFR cigs across 
portions of the northern Sound and coast this afternoon with some 
VFR across the south Sound. Any VFR cigs this afternoon will lower 
again late tonight through Saturday morning. IFR cigs possible in 
spots Saturday morning. A few showers will be around this afternoon 
but most sites will stay dry. Southerly winds 7 to 14 knots with a 
few gusts up to 23 knots along the coast. 

KSEA...Some improvement to cigs across south Sound this afternoon 
with VFR cigs into this evening. MVFR conditions will return early 
tonight and continue into Saturday afternoon. Few showers arrive 
late Saturday morning and continue into the afternoon. Southerly 
winds 5 to 12 knots. JD

&&

.MARINE...Onshore flow through Saturday with strong northwesterly 
flow present over the coastal waters. Gale warnings continue for the 
outer coastal waters with SCA level winds for the inner coastal 
waters into Saturday. Surface flow will become lighter later 
Saturday into Sunday. Onshore flow will increase on Monday and 
continue through Tuesday. JD

&&

.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Warning until 2 PM 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.

     Small Craft Advisory for hazardous seas from 2 PM to 10 PM 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.

     Small Craft Advisory for rough bar from 6 PM this evening to 6 
     PM PDT Saturday for Grays Harbor Bar.

     Small Craft Advisory until 6 PM 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 until 6 PM PDT this evening for West 
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 8 AM to 2 PM PDT Saturday for West 
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$

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