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  Forecast Discussion for Southern Oregon and Northern California  

Forecast: Forecast Discussion | 7 Day Forecast

Forecast Discussion for MFR NWS Office

000
FXUS66 KMFR 240311
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
811 PM PDT Thu Mar 23 2017

.DISCUSSION...Updates were just sent, mainly to increase pops over
the west side. Light rain is spreading inland a little faster
than expected, and while we haven`t technically had measurable
rainfall at the Medford airport yet, it is definitely raining.
Cams and observations also show it raining over much of the rest
of the west side. Pops were already 100% most west side areas, but
the area from Medford to Grants Pass needed to be increased. That
said, we do expect southeast winds to increase overnight around
Ashland and Medford, which will try to dry things out.
Nevertheless, it seemed prudent to have high pops even if
precipitation amounts in the Rogue Valley aren`t impressive.

Wind-wise, things look on track. We`ve already had a gust to 49
knots on buoy 15, and winds are ramping up quickly over the
coastal ranges and capes. Winds are also picking up in Weed (gust
37 mph), and the east side won`t be far behind. Winds peak
overnight, and the current wind headlines look on track.

Cams show it is already snowing at Dead Indian Memorial Road
Summit and it`s starting at Diamond Lake. This evening`s sounding
in Medford had a snow level around 5000 feet, which is right about
where we expected it, so the winter headlines also look good. No
further updates are planned this evening. -Wright

&&

.PREV DISCUSSION... /Issued 500 PM PDT Thu Mar 23 2017/

DISCUSSION...

Short Term...Tonight through Sunday night...Two systems are set
to bring widespread rain, snow, and wind to our area through the
end of the weekend. The first will arrive late tonight and persist
into Friday, then a second will arrive Sunday. While there will
be a break between the events, it will be short lived, with
showers never really leaving the area completely before the next
front begins to push into the region. Models are in exceptionally
good agreement concerning this chain of events, so confidence
remains high.

The front edge of precipitation and clouds associated with the
first front are beginning to make their way onshore as of this
writing. These will spread up to the Cascade crest this evening,
but the main belt of precipitation will arrive later tonight.
Moisture amounts and inflows are healthy, but not overly strong,
so there are no significant hydro concerns. However, soils remain
saturated, and it will not take much for ditches and small creeks
to rise. Will monitor area gauges, but do not expect to issue any
flood headlines at this time. Winds will also increase through
this evening and tonight, but the parent low, remaining well to
our north, is beginning to fill and pressure gradients remain on
the low side. This should keep the strongest winds contained to
our usual trouble spots: higher terrain, the Shasta Valley, and
the Summer Lake basin. Wind advisories remain in place for these
areas.

Snow will be a concern, as snow levels during the event will
hover between 4000 and 5000 feet. Significant snow is expected
over the Cascades and the mountains of Western Siskiyou county.
Snow should also pile up along Mount Shasta and Highway 89, and
along Highway 97 east of the Cascades. These areas remain under a
Winter Weather Advisory, and more details can be found in the
winter Weather message at PDXWSWMFR.

Precipitation will transition to showers Friday afternoon, then
taper off through the night and into Saturday morning. but showers
will not fully come to an end before the next system lurking
offshore makes its way into the area on Sunday. Moisture inflows
and pressure gradients do not look to be as strong with this next
system, but snow levels should remain relatively similar. This
will produce some snow along the higher passes, and perhaps some
advisories will be necessary but confidence remains too low at
this time to issue. Widespread rain should begin to taper off from
west to east late Sunday, then post-frontal showers will continue
into the extended period. -BPN

Long Term...Mon March 27th through Thu night March 30th... GEFS
Integrated Vapor Transport (IVT) products and operational runs of
the GFS and ECMWF indicate that near normal temperatures and wetter
than normal conditions are likely to generally persist through this
long term period. Precipitation will be mostly showery and mostly in
a west to northwest flow, with the exception of one frontal system
focused on Wednesday, March 29th. There will be a bit of a leeward
downslope induced rain shadow over East Side much of the time
period, resulting less shower activity there.

Showers on Monday ride in on a west to even a northwest flow and
snow levels will likely be near 4000 feet. Showers look to be more
appreciable in the morning than the afternoon in terms of coverage
and intensity.

Models have trended drier for Tuesday, but it still does appear some
showers will occur on the coast and in the Umpqua. East of the
Cascades and south of the Umpqua Divide it will be a mostly dry day.

Models have come into better agreement in showing a frontal system
Wednesday both the ECMWF and the GFS dive in a frontal system under
northwest flow. While this system appears as if it will have some
cold air behind it, snow levels surge up to 6000 to 7000 feet on the
front side of it, and then down to near 5000 feet in showers on the
back side of it Wednesday night.

While there has been a clear trend over the past 5 days in both the
operational runs of the GFS and ECMWF as well as the CFSv2 toward
high pressure ridging building into the Pacific Northwest Friday
into next weekend there is one more shortwave trough riding in on
northwest flow that could bring more showers, mainly on the West
Side, on Thursday. -BTL

AVIATION...24/00Z TAF CYCLE...A strong frontal system will
move into the area tonight. Ceilings will gradually lower from west
to east across the forecast area this evening with terrain becoming
obscured. Ceilings will vary from VFR to MVFR with MVFR predominant
along the coast, in the Umpqua Valley and in the Shasta region.
Gusty south winds will occur along the coast, especially south of
Cape Blanco, and also inland over portions of northern California
and the East Side. Low level wind shear is possible at the terminals
west of the Cascades with turbulence expected near and over terrain
from the Cascades eastward. Periods of light to moderate
precipitation will accompany the front through the area overnight
into Friday morning. Expect conditions to improve a bit Friday
afternoon with ceilings becoming mostly VFR, though scattered
showers may occasionally lower ceilings to MVFR. -Spilde

MARINE...Updated 245 PM PDT Thursday 23 March 2017...A strong front
will bring widespread gales and very steep seas tonight into Friday
morning. Gales are most likely beyond about 5 NM from shore, but
also right up to shore near Cape Blanco. Winds will decrease Friday
into Saturday, but seas should remain steep due to a combination of
moderate westerly swell and fresh short period southwest swell. The
next front will arrive Sunday with another round of very steep seas
and possible gales. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 11 PM this evening to 2 PM PDT
     Friday for ORZ029-030.
     Wind Advisory from 2 AM to 2 PM PDT Friday for ORZ030-031.
     Winter Weather Advisory from 11 PM this evening to 2 PM PDT
     Friday for ORZ027-028.

CA...Winter Weather Advisory from 11 PM this evening to 2 PM PDT
     Friday for CAZ082-083.
     Winter Weather Advisory from 11 PM this evening to 2 PM PDT
     Friday for CAZ080.
     Wind Advisory until 2 PM PDT Friday for CAZ081.
     Wind Advisory from 2 AM to 2 PM PDT Friday for CAZ085.

Pacific Coastal Waters...Gale Warning until 4 AM PDT Friday for
     PZZ350-356-370-376.
     Hazardous Seas Warning until 11 AM PDT Friday for PZZ350-356.
     Small Craft Advisory for hazardous seas from 11 AM to 5 PM PDT
     Friday for PZZ350-370.
     Hazardous Seas Warning from 11 PM this evening to 11 AM PDT
     Friday for PZZ370-376.

$$

NWS MFR Office Area Forecast Discussion