Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 240425
Area Forecast Discussion
National Weather Service Seattle WA
925 PM PDT SAT JUL 23 2016
.SYNOPSIS...High pressure will bring dry and mild weather this
weekend into Monday. A weak system will move by to the north
Monday night bringing some marine air into the interior for
Tuesday. The ridge will strengthen Wednesday into the end of the
week with the warmest temperatures of the month expected.
.SHORT TERM...Clouds have been decreasing this afternoon and
evening as high pressure aloft builds over the area and low level
onshore flow weakens. Many areas have cleared but some cloud
patches remain, mainly over the mountains, west of Puget Sound
and over parts of the Southwest interior.
There will likely be some increase in low clouds again later
tonight along the coast and for parts of the interior as onshore
flow continues but mostly clear areas as well. Clouds should burn
off all areas Sunday morning for a sunny afternoon. 850 MB
temperatures rise around 8 degrees Celsius Sunday which should
translate into highs warming several degrees over the interior,
even with continued northwesterly low level onshore flow.
Monday will be very similar to Sunday. Onshore flow is forecast to
increase slightly, probably in response to a weak upper short
crossing the area in westerly flow aloft. Low clouds will probably
penetrate a bit farther inland Monday morning but it will still be
a mostly sunny day for much of the interior. Highs will probably
cool a couple degrees which is pretty negligible.
There will be another uptick in the low level onshore flow Monday
night and Tuesday resulting in a bit more cloudiness Tuesday and
slightly cooler highs again. Schneider
.LONG TERM...Previous discussion...A strong ridge of high
pressure will keep Western WA warm and dry through the end of next
week. Temperatures will peak Thursday and Friday with highs in the
interior reaching the 80s to lower 90s. The low level flow will
remain onshore with a sharp temperature gradient along the coast -
60s on the beaches to lower 80s a few miles inland.
A trough will form over B.C. next weekend which will knock 500 mb heights
back down into the 570s over the Pac NW. Onshore flow will be stronger
with temperatures trending back toward normal. The current forecast
is dry but if the trough digs farther south we may see isolated
showers, mainly coast and mountains. 33
.AVIATION...A flat upper ridge will peak in strength over western
Washington on Sunday. Light NW flow aloft through Sunday AM,
becoming west on Sunday PM. Low marine stratus on Sunday morning
will be confined to the coast and parts of the Strait of Juan de
Fuca. The air mass will be stable and dry for the next 24 hours,
except for shallow low-level marine moisture.
KSEA...Clear skies through Sunday evening. Northerly component
winds persisting at the terminal. Haner
.MARINE...Onshore flow of varying strength will continue for the
next week, with northwest winds prevailing over the Pacific
coastal waters. Westerlies through the Strait are forecast to
reach gale-force on Monday night. Small craft westerlies will
prevail most other afternoons and evenings for the next week.
PZ...Small Craft Advisory until 3 AM PDT Sunday for Central U.S.
Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
Strait Of Juan De Fuca.
You can see an illustrated version of this discussion at