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Area Forecast Discussion (AFD)

Issued by Seattle/Tacoma, WA (SEW)

FXUS66 KSEW 121731

Area Forecast Discussion
National Weather Service Seattle WA
925 AM PST Mon Nov 12 2018

.SYNOPSIS...An upper ridge will keep the area dry through Tuesday. A 
front will bring light rain to the Washington coast by Tuesday 
afternoon, spreading inland Tuesday night and Wednesday. Another dry 
period with areas of night and morning fog is expected Thursday 
through Saturday. A front may bring some light rain to the area by 
late Sunday or early next week.


.SHORT TERM...A quick look at current conditions shows that fog has 
cleared out faster than anticipated in current forecast...nothing a 
few quick edits and a forecast update cannot handle. Speaking of 
current conditions...obs from the Wind Advisory area show that winds 
are easing there a bit. Will continue to monitor...but if current 
trend holds the noon expiration there looks to be fine. Models 
continue to suggest fairly decent gradients in that area throughout 
the day...although the NAM is proving a bit stronger than the 
GFS...so there is certainly a case that it may need to be extended 
as well. As already stated...will continue to monitor and act 

Covered the now so thoroughly mainly because there is not much in 
the way of activity expected over the next 24 hours...as high 
pressure continues its slow eastward progression over the area 
today. This will result in fair skies over the area and as 
such...not a whole lot worth writing about.

Next system progged to enter the area Tuesday evening with models in 
general agreement on timing and precip amounts/coverage. This system 
will linger into Wednesday before tapering off Wed evening. Falling 
to typical model characteristics...the GFS is quicker to move things 
along with activity tapering off Wed evening while the ECMWF hangs 
on to things a bit longer into the overnight hours and very early 
Thursday morning. Inherited forecast looks to be a split of these 
two solutions and currently see no argument to deviate from such 
thinking at this time.  SMR

.LONG TERM...From Previous Discussion...High pressure aloft begins 
to build offshore Thursday. This will lift the baroclinic band 
northward mostly across southern British Columbia. Weak systems 
moving along this storm track will brush northern Washington 
Thursday with some light rain possible. Areas around Puget Sound 
should stay dry.

The GFS/ECWMF amplify the ridge just offshore, then shifts it over
the region over the weekend. Some past model solutions were
bringing in some wet systems toward the end of the week and the
weekend. However, most global models now show dry weather through
the weekend. Kept some low pops in the forecast Sunday as
confidence in timing of the next system is low. Early next week
may bring wetter conditions. Mercer


.AVIATION...The air mass across Western WA will remain dry and 
stable today with high pressure aloft and offshore flow. VFR 
conditions expected. SCT-BKN cirrus clouds aloft. Rain will increase 
Tuesday night as the next frontal system approaches and moves 
inland. 33

KSEA...Dry weather today with VFR conditions. E/NE winds to 10 kt.


.MARINE...Offshore flow will persist through Tuesday with high
pressure east of the Cascades and low pressure over the NE Pacific. 
Highest wind and waves will be over the Coastal Waters and western 
Strait of Juan de Fuca - Small Craft Advisories are in effect. The 
flow will turn onshore late Tuesday into Wednesday as a weak front 
crosses the area. A second weak frontal system will clip the region 
on Thursday. Offshore flow will return over the weekend. 33


.HYDROLOGY...River flooding is not expected the next 7 days.


WA...Wind Advisory until noon PST today for East Puget Sound 

PZ...Small Craft Advisory until 4 AM PST Wednesday for Coastal Waters 
     From Cape Flattery To James Island 10 To 60 Nm-Coastal 
     Waters From Cape Flattery To James Island Out 10 Nm-Coastal 
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From James Island To Point Grenville Out 10 
     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 10 PM PST Tuesday for West Entrance 
     U.S. Waters Strait Of Juan De Fuca.