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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 250206
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
607 PM PST Fri Feb 24 2017

The Marine and Aviation sections have been updated...

.DISCUSSION...

...Short Term...Tonight through Monday Night...The main focus of
efforts today revolved around the two systems that will bring
lower elevation snow to our area. Also of concern will be the cool
temperatures tonight, especially along the coast where a Frost
Advisory is in place through tonight.

The first system is beginning to arrive as this is being written,
with showers moving into the coast and snow levels dropping down
to sea level at times. Snow levels should stay above 1000 to 1500
feet for much of the time, but lower snow levels will not be
uncommon. The main burst of precipitation is expected later this
evening and tonight, as the trough and associated surface low
tracks south just offshore of the forecast area. The system is
tracking further west than in previous forecast cycles, and
normally, this would result in less precipitation amounts, but
moisture with the system has increased, and the end result is a
wider area where snowfall is expected to impact travel. The
advisory area now includes the entire coastal range from Douglas
to Curry and Josephine Counties and down into Siskiyou county, and
the foothills of the Cascades in Douglas and Jackson counties.

After a brief break Saturday afternoon and night, the next system
arrives Sunday morning. This low will track almost directly over
the forecast area, and should produce more widespread and
somewhat more intense snow. Snow levels will once again drop to
near 1000 feet, and suspect that snowfall will be rather
substantial above 2500 to 3000 feet. This would bring impactful
accumulations to nearly all passes, and perhaps even down into
some of the West Side valley floors. Have issued a Winter Storm
Watch for the Cascade Foothills, where the heaviest amounts are
likely, but will leave the more advisory-level areas covered
under the current SPS.

precipitation should wane, and cooler temperatures should
continue, as ridging builds in Monday behind the departing low.
High pressure will then remain in control as we head into the
extended term. -BPN

.Long Term...Tuesday through Friday...The operational models are
in pretty good agreement in this time period. The pattern will be
rather quiet with little or no chance of precipitation. A
northwest flow continues Tuesday with increasing 500 mb heights.
The models still show some QPF, but they are not as bullish as
they were yesterday. Even then suspect they are still overdone
given 500mb heights will be on the rise as the upper trough moves
east of our area. However the ECMWF shows weak pva moving in the
northwest flow during the day, so we`ll keep a slight chance
mention. Confidence is high it will be dry from next Wednesday
through the end of next week as the storm track shifts well north
of the area. Of note, the GFS shows more of a dirty ridge
scenario, but still keeps all of the QPF north of our area, but it
could mean more cloud cover and slightly cooler afternoon
temperatures.

We could be dealing with an increasing subsidence inversion next
Wednesday through Friday which means the valleys could stay cool and
the ridges milder. -Petrucelli

&&

.AVIATION...25/00z TAF CYCLE...
MVFR is expected along the coast and from the Umpqua Divide
northward this evening, including KOTH and KRBG, as low pressure
brings valley rain and mountain snow to those areas. Mountains in
those areas will be mostly obscured. CIG/VIS should improve in those
locations between 06Z and 12Z to VFR, but this will allow for a
period of clearing when fog and low clouds could form, mainly in the
09Z-18Z time frame. Elsewhere, VFR conditions are expected to be the
predominate condition through the overnight period, with mountain
obscurations across from the Cascades westward, and partial mountain
obscurations east of there. However, could not rule out brief MVFR
conditions in the valleys in snow showers through 12Z. VFR is
expected all areas by 18Z as skies become mostly clear. BTL

&&

.MARINE...Updated 300 PM PST Friday, 24 February 2017...
Low pressure centered west of the northwestern Oregon coast this
afternoon will sink southward over the area through Saturday
morning. This will bring breezy southerly winds that will become
northerly late Saturday afternoon. There is a slight chance of
thunderstorms as the core of the upper level low moves overhead
tonight into the pre-dawn hours of Saturday. Showers tonight will
taper off Saturday morning as high pressure builds in. Saturday
night through Monday another cold low pressure system will move
through from the northwest. Fresh swell will build Sunday through
Monday brining combined seas in the 9 to 12 foot range. BTL

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory from 10 PM this evening to 8 AM PST Saturday for
     ORZ021-022.
     Winter Weather Advisory until 10 AM PST Saturday for
     ORZ021-023-025.
     Winter Storm Watch from Sunday morning through late Sunday night
     for ORZ023-025-026.
     Winter Storm Warning until 10 AM PST Saturday for ORZ022-024.
     Winter Weather Advisory until 10 AM PST Saturday for ORZ024-026.

CA...Winter Weather Advisory until 10 AM PST Saturday for CAZ080.

Pacific Coastal Waters...None.

$$

BPN/MAP/BTL

NWS MFR Office Area Forecast Discussion