FXUS66 KSEW 260305
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
805 PM PDT Sat May 25 2019

.SYNOPSIS...Showers will end this evening as an upper low moves
south of the area. Drier and warmer weather is expected most of
next week with afternoon and evening showers over the Cascades 
most days. 

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...Water vapor satellite 
imagery clearly tells the story this evening with drier air in the 
mid and upper levels being imported on easterly flow aloft. The 
upper level low that brought rainfall earlier today continues to 
push southward off the central Oregon coast. As of 02Z, most shower 
activity was south and west of the Chehalis area. Surface gradients 
will become northerly tonight, but they will be weak. Combined with 
surface moisture from the recent rainfall, there should be some 
redevelopment of low clouds overnight. It will scatter out 
by mid morning Sunday. Heights will rise somewhat on Sunday and, 
with partial sunshine, temperatures will rebound to close to normal 
with highs in the mid 60s to lower 70s for much of the region. Some 
instability over the mountains will contribute to showers and 
afternoon thunderstorms with northeast flow aloft bringing some of 
it into the foothills and, locally, the lowlands.  27

From previous discussion...The upper low will shift inland over the 
southwest U.S. Sunday and Monday with an upper ridge off the coast. 
Western Washington will be on the northern periphery of the upper 
low. There will be enough wrap around moisture and instability for a 
chance of afternoon and evening showers and thunderstorms over the 
Cascades each day with the aid of daytime heating. The low lowlands 
look mostly dry although a few showers could drift off the Cascades. 

A weak upper ridge will shift over the area on Tuesday but it 
won't make much difference for the weather. It should be another 
mostly sunny day. An isolated showers or thunderstorm could 
bubble up over the Cascades in the afternoon but the weak high
pressure aloft will probably cap things a bit.

Highs will warm several degrees on Sunday to slightly above 
normal and then warm a few more degrees on Monday with lower to 
mid 70s common. Highs will cool a few degrees on Tuesday due to
stronger low level onshore flow but remain a little above normal.
Schneider

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...It looks like a 
decidedly wishy-washy and uneventful pattern Wednesday through 
Saturday with a weak upper ridge on Wednesday giving way to a weak
upper trough Thursday and beyond. There won't be any organized 
weather systems but an isolated shower can't be ruled out at 
times. Temperatures will be a few degrees above normal each day 
with not much day to day variation. Schneider

&&

.AVIATION...Easterly flow aloft tonight as an upper level low slides 
south of the area. Flow aloft becoming northeasterly on Sunday. 
Light northerly flow at the surface has developed this evening as 
weak surface ridging pushes southward over the interior of British 
Columbia. The mid and upper levels have dried considerably over the 
past few hours, but lingering low level moisture from today's 
rainfall should contribute to the development of some low MVFR and 
IFR ceilings overnight. The low level moisture will scatter out by 
18Z Sunday. Daytime heating will contribute to some instability over 
the Cascades on Sunday with afternoon and evening showers and 
thunderstorms possible. The flow aloft could bring some of this 
activity locally into the foothills.

KSEA...VFR cigs this evening lowering to low MVFR again at 
times overnight. Confidence in the details between now and about 15Z 
are low. Surface gradients are light, but nights are short this time 
of year. Some stratus development is possible. Surface wind light 
becoming northerly less than 10 knots.    27

&&

.MARINE...Surface onshore flow will become light northerly tonight 
into Sunday. Small Craft Advisory winds over the coastal waters 
through this evening will ease to below 20 knots tonight. Flow will 
be light on Sunday with increasing onshore flow Monday and 
continuing through Wednesday. At least SCA level winds expected both 
Monday and Tuesday evening in the central and eastern Strait of Juan 
de Fuca. JD

&&

.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.

&&

$$

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