Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 231027

Area Forecast Discussion
National Weather Service Seattle WA
330 AM PDT Sun Apr 23 2017

.SYNOPSIS...An active weather pattern is expected for Western
Washington this week as a series of systems will bring rain
throughout the week. Occasional lulls in activity will allow for
brief dry periods. Temperatures are expected to remain cool with
daytime high temperatures remaining below seasonal normals.


.SHORT TERM...Satellite imagery this early morning shows some breaks
in the cloud cover...which may allow for some peeks of blue sky once
the sun rises. Switching to radar...W WA is generally quiet,
although some showers do linger along the coast and into the

Most recent model runs come in a bit more optimistic than 24 hours
ago...with more pronounced breaks in the action during this
cavalcade of weather systems. The first of these breaks is set up
over the area now and looks to persist at least into mid-morning.
Next round of rain looks to push inland affecting the coast by late
morning and into the interior by afternoon. Activity will transition
over to showers this evening. The upper level trough looks to push
into the area Sunday night with models keeping the bulk of moisture
associated with the system to the south of the area. As the low
tracks overhead however...there will still be prospect for showers
into Monday. Current precip signatures however keep best chances for
rain confined to southern portions of the CWA (except for the
Olympics)...with Seattle either right on or just a hair north of the
boundary. There is a minor spike in activity late Monday afternoon
which may allow for showers to pop up area-wide as the upper low
pushes further southeastward. A weak ridge is quick to follow this the increase in pops will be short-lived before
conditions dry out once more starting Monday evening. These dry
conditions look to extend into late Tuesday morning as the ridge
traverses the area.

Another day...another front as precip is expected to return by
Tuesday afternoon with showery conditions persisting into Wednesday
morning. Not much of a break...if expected before the next
front moves inland Wednesday afternoon and much like the previous
front...showery conditions are expected to linger into Thursday.

As would be expected from such an active period...temps do not look
like they are going to get much in the way of traction for climbing
back up to the 60 degree mark with current models keeping lowland
temperatures generally in the mid to upper 50s. In an attempt to
keep spirits up will say that certainly would not be surprised if
lull in activity on tap for Monday allows temps in some locations to
get tantalizingly close.  SMR

.LONG TERM...Upper level ridging progged to push into the area
Thursday night might be the first promising hint of having more than
24 hours of dry conditions. While models keep the initial onset of
this ridge a touch on the dirty side...which may allow for a shower
here or there...the bulk of the period from Thursday night at least
into Saturday morning looks mostly dry. Even better is the fact that
current progs also nudging next upper level low on a more northern
track...pushing it into northern portions of B.C.  If that ends up
being the case...dry conditions could persist for most of the CWA
(except the northern-most portions) into Sunday morning. Sunday
afternoon and evening may see some showers associated with this
system drift down into remainder of the apparently the
bullet can only be dodged for so long. Good news from that is
ridging builds in again overnight Sunday and may just persist into
the first half of next week.  SMR


.AVIATION...An upper trough will spread into Western Washington
today, bringing a resurgence of fairly widespread rain by late
this morning. The air mass will become even more moist this
morning, so cigs will lower into and persist in the 020-035
range. The air mass will be a bit unstable. Moderate southwest
flow aloft today will become weak tonight.

KSEA...Air mass will become increasingly moist through this morning,
so a gradual downward trend in cigs is expected. Cigs in the
020-030 range are expected to prevail this morning. Numerous light
to moderate rain showers are expected at the terminal from late
this morning through this afternoon, lowering cigs further at
times to below 020. Showers will ease this evening, but cig
improvements will wait until later tonight. Southerly winds will
persist until late tonight. Haner


.MARINE...A weak surface trough will move northeast across the
waters today. A 1002 mb surface low will move eastward onto the
far North Oregon Coast on Monday morning. A front will move
northeast across the area on Tuesday afternoon and Tuesday night,
preceded by southerly offshore flow, then followed by southerly
onshore flow. Westerly flow will increase on Wednesday and
Thursday, with westerly gales becoming possible in the central and
eastern Strait of Juan de Fuca.  Haner




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