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Area Forecast Discussion (AFD)

Issued by Seattle/Tacoma, WA (SEW)

                            
000
FXUS66 KSEW 201539
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
839 AM PDT Sat Jul 20 2019

.SYNOPSIS...Warm and dry weather returns for the weekend into early 
next week. A weak weather system will bring cooler temperatures 
later Tuesday into Wednesday before high pressure rebuilds over the 
region for warmer and drier conditions Thursday and Friday.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...High pressure will give dry 
and stable conditions across western WA today. Skies are mostly 
sunny with just a few patches of stratus along the north coast. 
Temperatures will be close to normal today with highs in the 
interior in the mid to upper 70s. The coast will be cooler, mainly
in the 60s, with NW onshore flow. The current forecast is on 
track. 33

Previous discussion...Low level flow remains only weakly onshore 
through midday Sunday and 850 mb temperatures suggest about 5 to 7
degrees of warming for the interior. That translates to some mid 
80s for the Seattle area southward. Onshore flow will increase 
Sunday night with low clouds pushing at least partially inland. 
Stratus could make it as far as south Puget Sound by daybreak 
Monday. With lower heights and a little more marine air in place, 
temperatures will cool a few degrees on Monday (but still remain 
above normal). 27

.LONG TERM /TUESDAY THROUGH FRIDAY/...Previous discussion...Upper
ridging continues to weaken on Tuesday as an upper trough digs 
into the offshore waters. Stronger onshore flow will likely keep a
marine layer in place at the coast with morning clouds and some 
afternoon partial sunshine for the interior. A chance of showers 
was added to north Cascades for Tuesday night as models are 
advertising some instability near and east of the Cascade crest 
ahead of the trough. The upper trough shifts onshore on Wednesday.
It's sharper and stronger in the 00Z GFS than the Euro. There's 
not much moisture with it in either solution, but it warrants a 
chance of showers in the mountains and a slight chance for the 
lowlands. The trough quickly lifts out by Wednesday night with 
upper ridging rebounding over the area for dry conditions and 
temperatures near or little above normal for Thursday into Friday.
27

&&

.AVIATION...Sunny skies currently reside across most TAF sites this 
morning, and this will continue to remain the case through the day. 
A few residual clouds and some fog linger near PWT and HQM but 
current obs indicate these specific terminals have seen noticeable 
improvements over the last few hours and are generally clear at this 
hour /15z/. Not expecting much of an onshore push overnight so 
should see generally the same conditions overnight tonight into 
Sunday morning with mostly clear skies the rule for most. Calm to 
light and variable winds will pick up from the W/NW this afternoon 
between 5-10 kt and drop back down overnight.

KSEA...Clear skies with winds N/NW 5-10 knots. 

Kovacik

&&

.MARINE...Waters are tranquil this morning as shortwave ridging 
allows for clear skies and light winds. Light gradients within this 
weather pattern will preclude the need for any headlines today. 
Onshore flow is expected to continue to remain weak overnight 
tonight into Sunday morning so conditions will largely mimic those 
of today. Guidance still suggests that onshore flow will strengthen 
Sunday afternoon through Monday, in which case small craft advisory 
headlines will likely return to the Strait of Juan de Fuca.

Kovacik

&&

.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...None.
&&

$$

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