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)

                            
000
FXUS66 KSEW 230937
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
237 AM PDT Tue Apr 23 2019

.SYNOPSIS...Scattered showers will taper today as an upper trough
shifts inland. High pressure aloft will bring dry weather
Wednesday and Thursday. A weak upper trough will bring a slight
chance of showers on Friday. A stronger and wetter trough will
move through on Saturday followed by mainly dry weather Sunday and
Monday. 

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...A broad upper trough will
maintain a chance of showers today - mainly coast, mountains and 
in a loosely defined Puget Sound Convergence Zone this afternoon 
and evening. Highs will be near normal. 

An upper ridge will build over the area Wednesday and Thursday for
dry weather with highs warming a couple degrees each day.
Wednesday should be mostly sunny after areas of morning low 
clouds burn off. Mid and high clouds will be increasing again on 
Thursday as the next upper trough approaches. Schneider

.LONG TERM /FRIDAY THROUGH MONDAY/...A weak upper trough will
cross the area on Friday. An isolated shower is possible but
mostly it looks like another dry day. A stronger upper trough will
drop down from the northwest on Saturday for a good chance of
showers and low snow levels, at least for late April. 

The Saturday upper trough will shift inland on Sunday with shower
chances ending. Another weak upper trough will develop over the 
area on Monday for a slight chance of showers again. Temperatures 
will be seasonable through the period. Schneider

&&

.AVIATION...A weak frontal boundary will continue to make eastward 
progress across the state this morning. This front was responsible 
for shower activity earlier in the day, much of which has ended. A 
few scattered showers may linger today with a potential convergence 
zone developing mainly in the PAE to BLI area. Ceilings are low this 
morning, mostly in the MVFR category with some spotty IFR. These 
ceilings will carry thru sunrise where then gradual improvement is 
expected thru the afternoon back to VFR. Ceilings could drop back to 
MVFR tonight but it does seem likely there will be more clearing 
come Wednesday. Winds from the S/SW in the 10-15kt range with a few 
gusts near 20kt possible. Winds then turn to the E/NE for at least 
terminals near the South Sound tonight.

KSEA...MVFR cigs this morning with spotty periods of IFR possible. 
Cig lift back to VFR this afternoon. Spotty showers linger in the 
vicinity. Winds S 10-15 with a few gusts before turning NE tonight. 

Kovacik

&&

.MARINE...A weak cold frontal boundary will continue to push through 
Washington State this morning. Southerly wind out ahead of the 
airmass boundary will shift to the W/NW in the front's wake. 
Overall, light gradients will yield fairly tranquil winds across all 
waters through sunrise.

During the morning hours following sunrise today, winds out the W/NW 
behind the front will increase across the coastal waters, followed 
eventually by a rather strong push of westerly flow down the Strait 
of Juan de Fuca. Have issued a small craft advisory for the central 
and eastern portions of the Strait beginning 18z. Winds will likely 
bleed in to nearby Admiralty Inlet and Northern Inland Waters. Have 
opted to go SCA for the Inlet but omitted headlines in Northern 
Inland Waters, as majority of these waters should remain well below 
21kts.

By this evening, guidance suggests gradients increase substantially 
within the Strait to the 3.6-3.9 mb range with continued strong 
westerly flow. Nonetheless, even the most aggressive guidance 
suggest winds only in the upper 20 kt range. Despite this 
discrepancy, gales could become possible across the central and 
eastern Strait tonight so have issued a Gale Watch and will let day 
shift make the call. Winds finally die down in Strait for Wednesday 
but will need to watch Northern Inland Waters and Coastal Waters for 
another round of SCA wind.

Kovacik

&&

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

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Watch from this afternoon through late tonight for Central 
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. 
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 11 AM this morning to 5 PM PDT this 
     afternoon for Central U.S. Waters Strait Of Juan De Fuca-
     East Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 11 AM this morning to 5 AM PDT 
     Wednesday for Admiralty Inlet.

&&

$$

www.weather.gov/seattle