Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 270420
Area Forecast Discussion
National Weather Service Seattle WA
920 PM PDT Sun Mar 26 2017
.SYNOPSIS...The front that brought rain to the area today has
moved into the Cascades and is weakening. An upper level trough
behind the front will give showers to the area through Monday
night. A warm front will move through the area on Tuesday giving
rain, mainly to the Olympic Peninsula. A stronger front associated
with a vigorous low pressure system will give rain and windy
conditions to the area Tuesday night and Wednesday. A trough will
likely give showers to the area on Thursday. Dry weather is
expected on Friday.
.SHORT TERM...The frontal system that gave a wet and cool day to
the region today is now moving into the Cascades. Precipitation
has become more showery behind the front. Satellite imagery shows
an upper level trough extending from a low in the central portion
of the Gulf of Alaska south-southeast into the southern Oregon
offshore waters this evening. This trough will push slowly
eastward across the area through Monday night. Enhanced clouds
within the trough at 46-48N 130W promises to bring some
enhancement to the shower activity on Monday.
It really does not appear that there will be much of a break
between Monday`s showery trough and the warm front that will
brush the Olympic Peninsula on Tuesday. Moderate precipitation
will most likely be focused on the northwestern Olympic Peninsula
and into Vancouver Island with this warm frontal feature
(consistent with previous model solutions and the going forecast).
Another wave will move into the area from the WSW Tuesday night
into Wednesday. Models are consistent in showing heavier rain with
this front and windy conditions across much of the area on
A update was issued this evening to refine POPS and forecast
wording through Tuesday. Changes were rather minor though.
.LONG TERM...From the previous long term discussion: The push of
onshore blustery weather behind the system on Wednesday will
settle down Wednesday night and Thursday. An upper trough moves
inland and surface high pressure builds across the region. An
upper ridge will be in place Friday for a dry day with some
sunshine. Clouds will likely increase Friday night with a chance
of rain by Saturday as a warm front pushes into the ridge.
.AVIATION...An upper level trof offshore will move over wrn WA
overnight. Strong sw flow aloft will weaken. The low level flow will
remain light sly. Expect wdsprd MVFR CIGs overnight with areas of
MVFR VSBYs (mainly with precipitation).
KSEA...Expect MVFR CIGs thru Monday morning. VFR conditions are
anticipated Monday afternoon but there will probably be occasional
MVFR CIGs with heavier showers. Winds will be sly 5-10 knots,
picking up slightly Monday afternoon.
.MARINE...High pres will prevail overnight for light southerly
flow. A trough will move across the area on Monday for continued
southerly flow. The flow will back to southeast Monday night in
response to falling pressure over the offshore waters ahead of a
weak cold front. This front will move across the area on Tuesday.
A strong frontal system will impact the region on Wednesday.
.HYDROLOGY...A wet frontal system will give rain to the area later
Tuesday through Wednesday. While precipitation amounts will only
be moderate, soils are quite saturated and there will be a good
deal of runoff. Most rivers will see rises, and a few could
The normally flood-prone Skokomish River increasingly appears that
it will go over flood stage early Wednesday and may see moderate
flooding. A Hydrologic Outlook was issued for the Skokomish River
in Mason County as a result and the forecast hydrograph was
PZ...Small Craft Advisories for hazardous seas are in effect for the
You can see an illustrated version of this discussion at