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Area Forecast Discussion (AFD)

Issued by Seattle/Tacoma, WA (SEW)

                            
000
FXUS66 KSEW 142335
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
335 PM PST Mon Jan 14 2019

.SYNOPSIS...An upper ridge over the Intermountain West will allow 
for dry conditions to continue into tomorrow with daytime 
temperatures expected to remain above normal. Rain will return from 
the south Wednesday with temperatures falling closer to normal. 
Unsettled conditions will persist into the weekend.

&&

.SHORT TERM...Clear skies this afternoon with morning fog finally 
dissipating over Olympia...Chehalis and points in between. Afternoon 
temperatures over the area are currently meeting morning 
expectations with most observations sites reporting upper 40s to 
lower 50s. The exception would be the aforementioned fog prone areas 
that are still down in the mid to upper 30s due to lack of daytime 
solar radiation.

Models remain a broken record over the short term as they remain in 
lockstep keeping the upper level ridge in place into Tuesday. Still 
progged to start to see some gradual weakening in said ridge as an 
upper level trough starts to affect portions of CA. While this 
trough is the next system of concern for W WA...it takes its time 
getting here as the area will still be under hashtag ridgelife for 
Tuesday also. The ridge however will be pushed further and further 
east throughout the day Tuesday allowing for precip to creep into 
OR. 

First portion of incoming system expected to move in from the south 
starting Wed morning...although will weaken as it approaches. Models 
seem to be slowing this down a bit though and as such have adjusted 
the forecast to be about 6 hours slower than what was inherited. So 
while precip is expected to finally return to the area...amounts 
expected to be generally light. Better pops and QPF values look to 
hold off until Thursday...as the upper low moves closer to the PNW. 
Consensus in the models persists...which feels a little unusual 
given their differences of opinion over the past few days. Both 
models now have the low center directly approaching WA Thursday 
allowing for wet conditions to persist.  SMR

.LONG TERM...The aforementioned low is progged to move eastward 
through the state Friday keeping conditions wet. Models also agree 
on an upper level ridge entering the area in its wake...but models 
also agree that this ridge is not going to bring much in the way of 
relief from precip...as systems will ride along the top of the ridge 
keeping rain in the forecast for W WA into the weekend. This ridge 
will exit late Saturday allowing for a frontal system to keep rain 
going into Sunday.  SMR

&&

.AVIATION...Strong high pressure, surface and aloft, over the 
Intermountain West will maintain dry and stable weather in Western 
Washington today and tonight. Moderate southeast flow aloft will 
continue. At the surface, offshore flow will continue with high 
pressure inland and lower pressure offshore, though gradients will 
generally be less than over the last several days.

Skies are clear over the vast majority of the area. However there 
are still a couple of big patches of fog/stratus over southern Puget 
Sound and the southern end of the Strait of Georgia. There is also a 
small patch of stratus near Port Angeles. These may not completely 
dissipate before the sun goes down, and they are likely to expand 
later tonight. Pressure gradients tonight will be lighter and fog 
will probably become more extensive on and near the water as the 
night wears on. Most places including the mountains will remain 
clear.

KSEA...Clear skies over the terminal. Will probably put at least a 
few hours of IFR fog in the terminal late tonight and early Tuesday 
morning. Northerly wind 5-10 kt. CHB


&&

.MARINE...Strong high pressure east of the Cascades will keep 
offshore flow going through Tuesday. Small craft advisory strength 
east winds are likely near the west entrance today and tonight. 
Otherwise winds will be less than 20 kt.

A strong Pacific frontal system will bring increasing southerly flow 
Wednesday and Thursday. Gales are possible Wednesday night through
Thursday night on the coast. Mesoscale models do not currently have 
gale force winds over the inland waters this week. CHB

&&

.HYDROLOGY...River flooding is unlikely over the next 7 days. 

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 10 AM PST Tuesday for Coastal Waters 
     From Cape Flattery To James Island Out 10 Nm-West Entrance 
     U.S. Waters Strait Of Juan De Fuca.


&&

$$

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