High Wind in Oregon, April 6 to 7, 2019

Area Forecast Discussion
National Weather Service Medford OR
915 PM PDT Sat Apr 6 2019

.DISCUSSION...

Rain has started to push into southern Oregon and northern
California this evening. The most notable location is the
southern Oregon coast at this time with Brookings reporting 0.5
inches and some sites in the southern coastal range reporting 1.5
inches already. However, the moisture plume seems to pushing north
as the warm front moves north. Therefore, the central Oregon
coast should really start seeing the precipitation rates increase
over the next 6 hours. Eventually, this front will stall and
linger over the forecast area on Sunday.

The only changes made to this update is increasing probability of
precipitation tonight and into tomorrow. The Rogue Valley could
stay dry until Sunday evening because of the strong south winds
surging into the valley for the majority of Sunday.

Read the discussion below, more specifically the 2nd and 3rd
paragraphs, for more information on flooding potential.

-Smith

&&

.AVIATION...For the 07/00Z TAFS...A cold front stalled along the
coast will continue a mix of IFR/MVFR from the coast to the coastal
range overnight with moderate to heavy rain, mountain obscuration,
and gusty, strong south to southwest winds. Conditions farther
inland will remain mainly VFR overnight, though with local MVFR
expected with showers. A brief diminishing in the surface winds is
expected tonight before the front pushes inland on Sunday, but
 will continue to be possible at KLMT and other airports east of
the Cascades. The strongest winds will be at the coast, the Shasta
Valley and areas east of the Cascades. During Sunday, cigs/vsbys
west and north of Medford will likely be MVFR/IFR depending on
rainfall intensity. Expect partial to full terrain obscurations to
develop on Sunday. Coverage will expand later in the day,
continuing into Sunday night with rain spreading across the area.

-Weygand

&&

.MARINE...Updated 800 PM PDT Saturday, 6 April 2019...
Winds have increased to gales once again this evening, and will
persist at gale force into Sunday afternoon. Very steep seas are
expected to continue through Sunday night with the combined wind
waves, fresh southwest swell, and longer period west swell each at
high levels. Improvement that begins Sunday night will be more
noticeable on Monday though seas are likely to remain steep into
Tuesday. A few weaker disturbances in a northwest flow will keep the
pattern active during the second half of the week. But, conditions
are likely to be below advisory conditions through Friday, with seas
expected to reach a minimum on Wednesday night.

-Weygand

&&

.PREV DISCUSSION... /Issued 312 PM PDT Sat Apr 6 2019/

DISCUSSION...A frontal system is in the process of stalling out
across the PacNW this afternoon. An atmospheric river (AR) will
set up over the area tonight and will continue through Monday
night as multiple areas of low pressure, all with origins in the
deep tropics, ride along this boundary and bring periods of heavy
rainfall to portions of the forecast area. Water vapor imagery
shows this corridor of deep moisture extending all the way back
across the tropics of the central Pacific north of Hawaii. Latest
model guidance is showing rainfall increasing along the coast this
evening, and really picking up in earnest around or just after
midnight and then continuing through Sunday. The main areas
affected during this time frame will be the immediate coast, the
coastal mountains and into the Umpqua Valley with areas farther
south and east seeing little or no precipitation. It may actually
be a breezy, mild day here Sunday in Rogue Valley with
precipitation mostly to the north and west.

The main focus for precipitation will be in Curry and western
Josephine County where 4-8 inches of rain are expected with local
amounts more than 10 inches in the Curry coast ranges through
Monday. The trend in the guidance over the last 24 hours has been
to bring more precipitation farther north, so we have expanded
the areal flood watches to include all of the west side from the
Douglas County Foothills westward. Rain amounts in these areas
should be 2 to 6 inches, with the highest amounts in the higher
terrain and the Foothills surrounding Toketee Falls. This will
bring rapid rises to most area streams, creeks and rivers with
some reaching bankfull. Some of the streams/creeks that respond
more quickly to runoff will likely flood at some point, so be on
the lookout for areal flood advisories/warnings. Confidence in
main stem river flooding is still on the low side. Our main source
of uncertainty remains with the exact location of the heaviest
rainfall and how fast this area will shift south and east. This
makes it difficult to know exactly which rivers stand the best
chance of flooding. For now, we have issued river flood watches
for those that stand the best chance at this time (S. Fork
Coquille at Myrtle Point and the lower Rogue at Agness).

At some point Sunday night into Monday, the AR will get a nudge
south and eastward as an upper trough well offshore approaches.
This will bring periods of moderate to heavy rain across the
remainder of the west side, western Siskiyou County, the Shasta
Region and portions of the East Side. We have maintained the flood
watches in these areas and added portions of Jackson County. The
upper trough will send the rain band associated with the AR to the
southeast of the area Monday night, but plenty of instability
behind it will keep showers going across much of the area. There
is a slight chance of a thunderstorm Monday afternoon and night,
mostly west of the Cascades as the upper trough offshore
approaches.

-Spilde

LONG TERM...Tuesday through next Saturday. The GFS and ECMWF
operational runs are in fairly good agreement starting Tuesday,
but with the upper trough offshore compared to over the region as
it showed yesterday. This trough shifts east later Tuesday with
another front slipping down the back side of the ridge well
offshore Tuesday night/Wednesday morning. The GFS and ECMWF then
vary on bringing a closed low down into the region, with the GFS
being faster in bringing the closed low over the region Thursday
afternoon, while the ECMWF bring a weaker closed low to the east
of the region Friday morning. The upper low continues to move to
the southeast with an upper ridge building in behind Friday. This
ridge shifts eastward with the GFS and ECMWF coming into agreement
again, with an upper trough moving in and bringing another front
into the region Saturday.

-Sven

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Flood Watch from Sunday afternoon through Monday evening for
     ORZ029>031.
     Wind Advisory until 10 PM PDT Sunday for ORZ030-031.
     High Surf Advisory until 5 AM PDT Sunday for ORZ021-022.
     Flood Watch through Monday morning for ORZ021>025.
     Flood Watch from Sunday afternoon through Monday morning for
     ORZ026.

CA...Flood Watch from Sunday afternoon through Monday evening for
     CAZ082-083.
     Flood Watch from Sunday morning through Monday afternoon for
     CAZ080.
     Wind Advisory until 5 PM PDT Sunday for CAZ081.

Pacific Coastal Waters...High Surf Advisory until 5 AM PDT Sunday for PZZ350-356.
     Gale Warning until 2 PM PDT Sunday for PZZ350-356-370-376.
     Hazardous Seas Warning from 2 PM Sunday to 2 AM PDT Monday for
     PZZ350-356-370-376.