161 
FXUS66 KMFR 042314
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
314 PM PST Mon Mar 4 2019

.DISCUSSION...An active winter pattern returns Tuesday, with snow
levels generally above 4000 feet. Moisture begins to feed from 
the south tonight and wrap around, warm frontal precip moves in on
the nose of a 100 kt jet and moves north through the day on the 
nose of a 100 kt jet. The pressure gradient increases in the Mt. 
Shasta area and with it the winds from the south and the precip 
rates in that area. The increased rates will bring snow levels 
down below the prevailing 4500 feet in the Mt. Shasta area, and 
snow levels may drop to near 3500 feet at times in this area. The 
upper low moves on shore near Cape Mendocino Wednesday morning. 
Heavy snow rates at times continue in Siskiyou county, especially 
in the Mt. Shasta area, and Black Butte Summit may see as much as 
2 to 4 inches by Wednesday night. Cold air moves in on the tail of
the exiting front, dropping snow levels below 2000 feet by 
Thursday morning, but the bulk of the precipitation will have 
moved also, and only light amounts are expected at lower 
elevations. Sven

.EXTENDED DISCUSSION...Thursday night through Monday Night...A 
parent low pressure system in Washington will eject a few short-
wave disturbances which will create lingering showers into the 
weekend. Snow levels will have fallen back down to 2000 feet 
across most of the areas behind the front, and could dip to some 
of the west side valley floors, especially at night. The showers 
are not expected to be overly heavy, but some low pass snow will 
be possible across the west side valleys as well as for the valley
floors east of the Cascades. 

Overall precipitation amounts are not expected to be high--it will 
not be just like what we saw with the last front. After that, the 
low pressure system wants to retrograde westward and southward 
through our area in some of the models with other models taking a 
bit longer for this to occur. As a result, confidence is low for any 
part of the forecast late this weekend into next week and will need 
to be watched. The European model is showing this low dip into 
southern Oregon along the coast, and could produce some low 
elevation snowfall yet again. The GFS has the low move farther 
offshore with an overrunning ridge build in for more benign weather. 
Either way, another system approaches the Pacific Northwest on 
Tuesday, and the forecast will need to be monitored in the coming 
days as potential impacts become more clear. -Schaaf


&&

.AVIATION...For the 04/18Z TAFs...Stratus with IFR to MVFR ceilings 
remains over the Umpqua basin (including KRBG) this morning and will 
gradually recede from the edges through the afternoon. Elsewhere, 
VFR conditions will continue through this evening. Stratus will 
likely reform again in the Umpqua Basin (including KRBG) again late 
tonight. It is also possible at KMFR, but confidence is not high 
enough to put in the TAF just yet. -Wright

&&

.MARINE...Updated 200 PM PST Monday, March 4, 2019...North winds and 
choppy seas will continue through Tuesday night, however, conditions 
are not expected to reach advisory criteria. Models are in good 
agreement that low pressure will move by to our south Wednesday and 
bring increased north winds and seas. All guidance brings conditions 
(winds and wind waves) right to the edge of small craft advisory 
criteria, but there is also good agreement in the general lack of 
swell to further augment the sea state. Therefore, we will opt to 
not issue a small craft advisory for Wednesday at this time and just 
keep an eye on the models as we get closer. If advisory level 
conditions do not materialize on Wednesday, we are unlikely to need 
any headlines until Sunday at the earliest when a steep west swell 
is expected to arrive. -Wright


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Freeze Warning from 3 AM to 9 AM PST Tuesday for ORZ025. 
     Winter Weather Advisory from 4 PM Tuesday to 10 PM PST Wednesday 
     for ORZ027>030. 

CA...Winter Storm Warning from 4 PM Tuesday to 10 PM PST Wednesday 
     above 4500 feet in the for CAZ080-082-083. 

Pacific Coastal Waters...None.

$$

SBN/SBN/SBN