Hazardous Seas Warning 10, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
922 AM PST Wed Feb 8 2017

.DISCUSSION...A powerful storm is on track to bring gale to storm
force winds to the coastal waters, with strong winds to the coast
this afternoon. Winds at 925 and 850mb have a strong onshore
component and damaging winds could spread beyond the immediate
coast to the coastal range. Damaging winds are expected to move
into the Siskiyous and Cascades this evening. This is in addition
to the Shasta Valley and east of the Cascades where winds are
normally strong with a frontal passage.

With snow levels rising above 7000 feet, runoff from snow melt
will contribute to hydrologic concerns. It will not be until
Thursday night before snow levels drop to around 4500-500 feet.

We have gone above guidance on QPF values in Curry and southern
Josephine Counties for tonight and early Thursday timeframe. This
has been a case with past atmospheric river events due to enhanced
orographic lifting. /FB

&&

.AVIATION...08/12Z TAF CYCLE...Areas of MVFR/IFR along the coast and
in the Umpqua Basin will clear to MVFR to VFR later this morning...
then areas of MVFR cigs/vsbys with higher terrain obscured will
develop late this afternoon into this evening as precipitation
becomes heavier. The lower conditions will persist through Wednesday
night. Over the remainder of the area...VFR conditions will prevail
initially...but areas of MVFR cigs with higher terrain obscured will
develop late this afternoon into this evening as precipitation
becomes heavier. The lower conditions will persist through Wednesday
night. Gusty winds will develop area wide which will lead to
turbulence inbound and outbound from the terminals. Low-level wind
shear is possible at KOTH, KRBG, KMFR, and KLMT after 18z
Wednesday.

&&

.MARINE...Updated 855 AM PST Wednesday 8 February 2017...Buoy
observations are on track with winds and seas coming in slightly
faster than originally forecast--but not enough to make any changes
to the previous forecast. Seas are steep this morning due to a
combination of wind waves and fresh south swell. A warm front will
move north through the area today. Confidence remains high that
south winds will increase to gale force, which will generate high
seas. Although models are easily showing hurricane force winds at
925 mb and the boundary layer with the coastal jet, the low is
occluding and the North Bend to Arcata gradient is only forecast
to reach 7 to 8 mb (albeit for a good amount of time). More times
than not, these two scenarios will keep winds from reaching
hurricane force. That being said, southerly storm force winds and
wind gusts will develop tonight into Thursday morning as a very
strong cold front moves through. Seas will become extremely
dangerous and mariners are urged to monitor the forecast for
updates--as we will be continuing to take a closer look at the
unfolding situation tonight. Afterwards, a couple of weaker fronts
will move onshore Thursday night and Friday with seas still
remaining hazardous. High pressure will then build offshore making
for a relatively quiet weekend with moderate northwest swell.
-Schaaf

&&

.HYDROLOGY...With the atmospheric river aiming at southern Oregon
and northern California this afternoon through tonight, rivers and
streams will be rising rapidly. Areal Flood Watches are in effect
and this includes the mountain zones for the potential for slides.
Many mainstem rivers will also go above flood stage. The Pit River
in NE California will be particularly high, reaching close to
Major Flood. See FLWMFR and FLSMFR for the list of flood products.

&&

.PREV DISCUSSION... /Issued 337 AM PST Wed Feb 8 2017/

DISCUSSION...Water vapor and precipitable water vapor imagery show
a stream of tropically-sourced moisture heading towards Southern
Oregon and Northern California. Low pressure will deepen to the
north of this moisture, and the forecast area is in store for
moderate to strong winds and heavy precipitation later today into
Thursday.

The tropical connection of this moisture will push snow levels up
sharply today, and heavy rain upon snowpack means the potential for
flooding. In fact, the Pit River in Modoc County is already in
flood stage, and this will only worsen as temperatures increase
and rainfall arrives today, but moreso late Thursday when rainfall
could be heavy at times. A Flood Warning has been issued for
this.

High winds will impact areas from the coastal waters to the East
Side. Winds really start cranking tonight into Thursday morning. The
modeled south to north component of the coastal low level winds
ranks in the top 1 percent for this time of year, so we expect
significant impacts at the coast including the potential for tree
damage and power outages.  Further inland, 700mb southwesterly winds
peak near 80kt and this will be sufficient to bring high winds to
the Shasta Valley, the high Cascades and Siskiyous, and portions of
the East Side. High Wind Warnings and Wind Advisories have been
issued at NPWMFR. Winds will taper off in most places by late
Thursday. It must be noted that the ECMWF has a significantly weaker
low pressure center over the Pacific waters in its forecast for
Thursday morning, at 988mb compared to the 06Z GFS 979mb, so our
forecast does represent the worst case scenario between those two
models.

Returning to the hydrological concerns, Areal Flood Watches cover
most of the forecast area due to the potential for sharp rises in
rivers and streams as well as potential for landslides where the
highest rainfall rates are forecast. The operational GFS and GEFS
solutions are remarkably similar in terms of Integrated Vapor
Transport (IVT), and have been so for the past 2 model runs, keying
in on Thursday morning for off-the-charts IVT values and the
heaviest rainfall rates. This is the time period we're most
concerned for urban flooding at coastal towns, but heavy rain could
occur at other times during the Areal Flood Watch. Heavy rain will
also impact wildfire burn scars in Western Siskiyou County, and
we have issued a Flash Flood Watch for these areas.

In addition to areal flooding, a host of main stem river points
will near flood stage over the next few days, and Flood Watches
have been issued for the Coquille River at Coquille, South Fork
Coquille at Myrtle Point, Klamath River near Seiad Valley, Scott
River near Fort Jones, and Sprague River near Beatty.

A cold upper trough swings through Friday and drops temperatures
sharply, and will bring snow to areas above 3000 feet.  There is
still some uncertainty in timing and precipitation amounts with this
feature, so we don't have specifics in terms of winter travel
impacts at this time.

Please see the previous discussion below for more details on the
weather pattern after the high winds and heavy rain.

Thursday Night through Tuesday...While the bulk of the
precipitation is expected to move out of the area by Thursday
Night, the upper level trough and surface low will remain just
offshore of the Pacific Northwest, producing southwest flow and
numerous showers over our forecast area. the trough will slowly
slide east, and pass onshore Friday afternoon. The models have
some varying ideas about how this will manifest at the surface,
with the GFS producing gusty winds and moving a bit quicker, the
ECMWF slower with little to no significant winds, and the NAM
somewhere in between. No matter the timing or the winds, there
will be another round of moderate precipitation Friday morning,
followed by showers in the evening and overnight. Snow levels
should stay above 4000 feet, but some light snow may make it down
to around 2000 feet as snow levels drop Friday night. With the
heavy rains from the previous days, flooding concerns will likely
continue into the weekend.

Ridging and surface high pressure will build in quickly behind the
departing trough on Saturday, and trends suggest that these will
keep the forecast dry through the remainder of the forecast term.
This should help dry the area form the extensive rains of the short
term, and allow the river levels to drop. Also, with mostly clear
skies and easterly flow, temperatures could warm to 5 to 10 degrees
above normal for the weekend and into early next week. Highs around
60 will not be out of the question for the valleys of the West Side,
but extensive snowpack in the mountains and East Side may limit
warming there. -BPN

AVIATION...08/12Z TAF CYCLE...Areas of MVFR/IFR along the coast and
in the Umpqua Basin will clear to MVFR to VFR later this morning...
then areas of MVFR cigs/vsbys with higher terrain obscured will
develop late this afternoon into this evening as precipitation
becomes heavier. The lower conditions will persist through Wednesday
night. Over the remainder of the area...VFR conditions will prevail
initially...but areas of MVFR cigs with higher terrain obscured will
develop late this afternoon into this evening as precipitation
becomes heavier. The lower conditions will persist through Wednesday
night. Gusty winds will develop area wide which will lead to
turbulence inbound and outbound from the terminals. Low-level wind
shear is possible at KOTH, KRBG, KMFR, and KLMT after 18z
Wednesday.

MARINE...Updated 200 AM PST Wednesday 8 February 2017...Seas will
be steep this morning due to fresh south short period swell. A warm
front will move north through the area today. South winds will
increase to gale force, which will generate high seas. South storm
force winds will develop tonight into Thursday morning as a very
strong cold front moves through. Seas will become extremely
dangerous and mariners are urged to monitor the forecast for
updates. Weaker fronts will move onshore Thursday night and Friday
with seas remaining hazardous. High pressure will then build
offshore making for a relatively quiet weekend with moderate
northwest swell.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning from 1 PM this afternoon to 4 PM PST Thursday
     for ORZ030-031.
     Flood Watch through Thursday evening for ORZ024>031.
     Wind Advisory from 1 PM this afternoon to 4 PM PST Thursday for
     ORZ030-031.
     High Surf Advisory from 3 PM this afternoon to 7 PM PST Thursday
     for ORZ021-022.
     High Wind Warning from 4 PM this afternoon to 1 PM PST Thursday
     for ORZ021-022.
     Flood Watch through Thursday afternoon for ORZ021>023.
     Wind Advisory from 10 PM this evening to 4 PM PST Thursday for
     ORZ023>025.
     High Wind Warning from 10 PM this evening to noon PST Thursday
     for ORZ027-028.
     Wind Advisory until 10 AM PST Thursday for ORZ026-029.

CA...High Wind Warning from 1 PM this afternoon to 4 PM PST Thursday
     for CAZ085.
     Flood Watch through Thursday evening for CAZ080>085.
     Wind Advisory from 1 PM this afternoon to 4 PM PST Thursday for
     CAZ085.
     Wind Advisory until 10 AM PST Thursday for CAZ084.
     Flash Flood Watch through Thursday afternoon for CAZ080.
     High Wind Warning until 10 AM PST Thursday for CAZ081.
     High Wind Warning from 10 PM this evening to 4 PM PST Thursday
     for CAZ083.

Pacific Coastal Waters...Small Craft Advisory until 7 PM PST this evening for PZZ350-356.
     Storm Warning from 7 PM this evening to 7 AM PST Thursday for
     PZZ350-356-370-376.
     High Surf Advisory from 3 PM this afternoon to 7 PM PST Thursday
     for PZZ350-356.
     Gale Warning until 7 AM PST Thursday for PZZ350-356-370-376.

FJB/FJB/BMS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEDFORD OR
1243 PM PST WED FEB 8 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1000 AM     HEAVY RAIN       2 SSW OBRIEN            42.05N 123.71W
02/08/2017  M1.01 INCH       JOSEPHINE          OR   TRAINED SPOTTER

            TOTAL FROM MIDNIGHT TO 10 AM PST.

&&

MND

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEDFORD OR
1244 PM PST WED FEB 8 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1244 PM     HEAVY RAIN       5 NNW BROOKINGS         42.12N 124.32W
02/08/2017  M1.00 INCH       CURRY              OR   TRAINED SPOTTER

            TOTAL SINCE 5 AM PST.

&&

MND