Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 232243
Area Forecast Discussion
National Weather Service Seattle WA
343 PM PDT THU JUN 23 2016
.SYNOPSIS...An upper level low will move across the area this
evening through Friday morning, bringing numerous showers, a
chance of evening thunderstorms, and lowering snow levels to 5000
to 6000 feet towards the morning hours. Showers will taper off
Friday as a ridging pattern sets in. Warmer and drier weather will
settle in over the weekend and into next week.
.SHORT TERM...Numerous showers are on the radar over Western
Washington, some of which may be heavy at times. Although there
has not been any lightning activity yet, more dynamic forcing will
be present this evening as an upper low moves directly overhead,
and a few lightning strikes is not out of the question. Have kept
the chance of thunderstorms in for this evening and expanded it a
bit northward to include the Strait of Juan De Fuca.
As the upper low moves over the Cascades and out of the area late
tonight into Friday morning, snow levels will drop to 5000 to 6000
feet for a brief period and some precipitation in the higher
recreational areas may fall as summer snow. Accumulations at
Rainy/Washington Passes and Paradise, if any, will not total more
than a few inches and will quickly melt off.
Showers will begin to taper off Friday as the upper low moves east
and an upper ridge settles in. Expect Saturday and Sunday to be
progressively warmer and drier with no precipitation expected as
the upper ridge pattern takes hold. Smith
.LONG TERM...The models are all in agreement that the ridging
pattern will be in place over Western Washington for the remainder
of the period for warm temperatures and dry weather. In the most
recent runs, models have also hinted at a weak shortwave trough
moving through late Monday, possibly bringing afternoon and
evening showers to the Cascades. Have edited the forecast for this
period accordingly. Smith
.AVIATION...Upper level low pressure will move east across
Washington tonight, then shift away from the area Friday. Light
westerly flow aloft tonight, then northwesterly Friday. Air mass
moist, especially in the mid and lower levels. Air mass weakly
unstable this evening, then somewhat stable overnight into Friday
morning. A few isolated thunderstorms are possible until sunset but
the probability is too low to include in TAFs.
KSEA...Showers through tonight, heaviest during the evening. A mix
of MVFR and VFR clouds will lower later tonight with widespread MVFR
by early Friday morning. There is a small threat of a thunderstorm
early this evening. South-southwest wind 8-12 g22 knots.
Cigs improving to VFR Friday afternoon with more showers.
.MARINE...Onshore flow behind a front will produce Small Craft
winds across most the interior waters through this evening.
The strongest westerly winds will be in the strait and areas
adjacent to the Eastern Strait. Winds easing after midnight.
High pressure builds offshore Friday into the weekend and early next
week. Expect varying degrees of onshore flow. Small Craft winds can
be expected in the Strait most late afternoon and evenings.
PZ...Small Craft Advisory until 3 AM PDT Friday for Central U.S.
Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
Strait Of Juan De Fuca.
Small Craft Advisory until midnight PDT tonight for Admiralty
Inlet-Northern Inland Waters Including The San Juan Islands.
Small Craft Advisory until midnight PDT tonight for Puget Sound
and Hood Canal.
You can see an illustrated version of this discussion at