Weather Service Report


388 
FXUS66 KMFR 261500
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
800 AM PDT Sun Mar 26 2017

.DISCUSSION...26/12Z NAM in.

The northern hemispheric projection shows a wave number of four
around the globe and occasionally hints at a five over the next
several days. This argues for a moderately progressive pattern. 
That is indeed what we will get over the next several days. 
Overall the pattern looks quite spring like...with weaker storms 
driven by low amplitude upper level troughs. The primary storm 
track will remain to the north of the area...but there will be 
some action down here. 

A weak long wave ridge is now moving out to the east. An upper 
level trough is approaching the coast...and it is ejecting short
waves short waves out ahead of it. The first of these short waves
is supporting a surface front which is now moving onshore. Light 
precipitation is being reported over the entire west side and 
near east side. Not much in the way of winds yet though. Winds 
have been gusty over the ridges...in the Shasta Valley...and east 
of the Cascades...but nothing impressive so far. With the cold 
core aloft...isolated thunderstorms are also possible today over 
the east side and tonight along the north coast. Snow levels will 
rise to 4500-6000 feet Sunday...then fall to around 3500-4500 feet
Sunday night. 

Subsequent short waves will support plenty of shower activity
Sunday night into Monday. The last of the short waves and the 
long wave trough will move through the area Monday. Showers will 
diminish in the wake of the trough. Snow levels will be 3000-4500
feet or so Monday.

After that, there will be a longer break in the action as a long
wave ridge moves toward the west coast. This will bring dry and
warmer weather to the area Monday night into Tuesday. The ridge 
axis will break to the east of the area Tuesday night and a strong
short wave riding up the back side of the ridge will move onshore
to the north of the area Wednesday. A warm front will move onshore 
Tuesday night...followed by a trailing cold front Wednesday
afternoon. With most of the upper level support remaining to the 
north...both fronts will be relatively weak this far south. Even 
so...most if not all of the Medford CWA will get some light 
precipitation Tuesday night into Wednesday. A stronger short wave
with a more southerly trajectory will move onshore Wednesday 
night with the long wave trough. This will support post-frontal 
showers lasting into Thursday.

&&

.AVIATION...26/12Z TAF CYCLE...A cold front will arrive at the coast 
early this morning and weaken as it spreads inland through the day. 
Ahead of this front, a stronger SW winds aloft could lead to low 
level wind shear at North Bend early this morning, then mid morning 
at Roseburg and Medford. Low level wind shear should not be a 
concern by this afternoon and kept it out of the TAF, but will need 
to be reevaluated. The front will also bring increased coverage of 
MVFR for areas west of the Cascades with local IFR over the coastal 
range. Snow levels will be around 5000 to 5500 feet MSL. 
-Petrucelli

&&

.MARINE...Updated 230 AM PDT Sunday 26 March 2017...South winds are 
already increasing and are approaching small craft ahead of the next 
front that is still west of the waters. South winds will ramp up 
further to Gales in the next few hours with gales expected to last 
into the afternoon. Steep seas are also expected. The models are in 
pretty good agreement pushing the front onshore this evening at 
which point winds will decrease and become southwest. However seas 
will remain steep through this evening. Seas will decrease tonight 
into early Monday morning, then a combination of a longer period and 
shorter period west swell is due to move in Monday afternoon 
resulting in combined seas between 10-13 feet. Steep seas could 
linger through at least Wednesday night. -Petrucelli  

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 11 AM PDT Monday for ORZ027-028. 

CA...Wind Advisory from noon today to 8 PM PDT this evening for 
        CAZ081. 

Pacific Coastal Waters...Gale Warning until 5 PM PDT this afternoon for 
        PZZ350-356-370-376. 
     Hazardous Seas Warning until 5 PM PDT this afternoon for 
        PZZ350-356-370-376. 

$$

15/15/15

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Western Regional Climate Center, wrcc@dri.edu