Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 280244
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
744 PM PDT Mon Mar 27 2017

.DISCUSSION...Upper troughing has moved east of the forecast area,
and upper ridging is now taking hold and drying things out
some. It`s a dirty ridge, meaning moisture is streaming overtop
the ridge and bringing plenty of high clouds across the area this
evening. Tomorrow will feature some sun peaking through the veil though
as the upper ridge axis moves overhead and mid and high cloud
thickness lessens. No precipitation is expected Tuesday over the
forecast area, and high temperatures will be right around normal.
I have bumped up temperatures a few degrees based on latest MOS
guidance and the expected thinning of mid and high clouds
tomorrow.

Dry conditions will be short-lived as another front and
associated precipitation arrives late Wednesday. Please see the
previous forecast discussion below for more details on this next
front and expected impacts.

&&

.AVIATION...28/00Z TAF CYCLE...A few Showers will linger at the
coast north of Cape Blanco and inland into Douglas County until
around 06Z this evening with local MVFR ceilings and mountain
obscuration. Otherwise, VFR ceilings are expected through Tuesday
afternoon. /DW

&&

.MARINE...Updated 200 PM PDT Monday 27 March 2017...With high
pressure building into the waters, winds have diminished but seas
will be at a peak this evening. Seas will be very steep in the outer
waters and steep in the inner waters. Seas are dominated by a west
swell at 12 seconds and another west swell at 18 seconds. Seas
diminish very slightly on Tuesday and remain high through Wednesday
night. An occluding front will then bring increasing southerly winds
Tuesday night into Wednesday morning with speeds reaching advisory
strength north of Cape Blanco beyond 8 NM from shore. Winds will
veer to north Wednesday night then may reach advisory strength in
the outer waters south of Gold Beach Thursday afternoon into
Saturday. Uncertainty in the forecast increases rapidly on Saturday
and is high into early next week. /DW

&&

.PREV DISCUSSION... /Issued 200 PM PDT Mon Mar 27 2017/

DISCUSSION...27/12Z NAM/GFS/EC 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 long wave trough has moved out to the east and a long wave ridge
is now building into the west coast. Shower activity is
diminishing and the heaviest activity is occurring from the
Cascades east.

The ridge 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 night. A stronger short wave with a more southerly
trajectory will move onshore late Wednesday night or early
Thursday morning with the long wave trough. This along with short
waves diving down the back side of the trough will support post-
frontal showers lasting into Thursday evening...but shower
intensity and coverage will diminish through the day Thursday.

After that...another long wave ridge will build into the west
coast and this will bring another round of dry and warmer weather
beginning Friday.

LONG TERM...Friday through Monday.

After a chilly morning, high pressure ridge is likely to bring a
warming and drying trend Friday into Saturday with the storm track
pushed northward into Canada. Model uncertainly continues to be high
for next weekend with the ECMWF being quicker to push the ridge east
and allow a trough to move into WA and northern Oregon. We have
introduced a slight chance of rain for Coos and NW Douglas County
for Saturday but confidence is not very high as the GFS continues to
maintain the ridge over our forecast area. Ensemble forecast high
temperature for SW Oregon points to a warm day so we are leaning
toward no mention of precipitation for the Rogue Valley. Confidence
is only slightly higher for precipitation Saturday night into Sunday
as the driest solution (EC) shows westerly flow instead of a ridge,
with a deep trough per the GFS. The GFS solution bears watching as
it develops a closed low near the Tahoe area. This would bring more
mountain snow to the Warners early next week. /FB

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.

CA...None.

Pacific Coastal Waters...Small Craft Advisory for hazardous seas until 5 AM PDT Thursday
     for PZZ350-356-370-376.
     Small Craft Advisory from 11 PM Tuesday to 1 PM PDT Wednesday
     for PZZ350-370.
     Hazardous Seas Warning until 11 PM PDT this evening for
     PZZ370-376.

$$

NSK/FJB/DW


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