Area Forecast Discussion
Issued by NWS Medford, OR

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570
FXUS66 KMFR 282341 CCA
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
200 PM PDT Fri Apr 28 2017

.DISCUSSION...28/12Z NAM/GFS/EC in.

A relatively quiet afternoon weatherwise over the Medford CWA. The
morning fog and low clouds are gone...but stratocumulus persists
over the north coast and Umpqua Basin as well as the far east
side.

A long wave ridge will persist offshore through Tuesday. Flow
aloft will be northwesterly most of the time until then...which is
usually a dry pattern for this area.

The one break in this pattern will occur Saturday night into
Sunday...when a short wave riding over the ridge will cause it to
flatten and flow aloft will become westerly. The short wave will
support a weak front which will move onshore Saturday night. The
bulk of the associated precipitation will fall along the
coast...in the Coast Range...the Umpqua Basin...and the Cascades.

The long wave ridge will build back in Saturday night. Post-
frontal showers will end by that time and the low level flow will
turn easterly. Low level flow will turn back onshore Monday.

As far as temperatures go...inland highs will warm to around 5
degrees above normal Saturday. It will be cooler Sunday over the
areas affected by the front...around 5 degrees below normal in the
Umpqua Basin and around normal over the rest of the Oregon zones.
Northern California will remain above normal for the most part.

However, the heat will return as the ridge rebuilds Monday into
Tuesday.

EXTENDED DISCUSSION...Tuesday through Friday...The models are in
good agreement showing dry conditions Tuesday through at least
Wednesday. Temperatures will be above normal with the warmest day,
at least in the Rogue valley occurring on Wednesday. After
Wednesday, the models show different solutions with the
progression of the upper trough in the eastern Pacific. The ECMWF
and Canadian are more progressive (although the Canadian is weaker
with the upper trough). The GFS shows a stronger ridge and the
upstream shortwave further north and weaker. Prior to the arrival
of the upper trough the ridge will be rather strong. Normally in
these type of situations the upper trough will tend to weaken as
it moves into the stronger ridge. Suspect the ECMWF is too strong
and the more plausible solution may be the Canadian. The forecast
will lean towards a drier solution, but we`ll still keep at least
a slight chance of showers and thunderstorms Thursday evening.
Confidence after Thursday is low and much will depend on the
progression or lack thereof of the upper trough. -Petrucelli

&&

.AVIATION...29/00Z TAF CYCLE...VFR conditions will continue through
the TAF period. The only concern will be gusty north to northwest
winds at the coast into early this evening. /FB

&&

.MARINE...Updated 100 PM PDT Friday, 28 April 2017...The thermal
trough along the coast will bring stronger north winds and
steepening seas to the coastal waters, highest south of Cape Blanco.
Seas may reach 10 feet in some areas in the expansion fan about 10
miles off the coast and south of Gold Beach. Farther north, winds
and seas won`t be as high, but seas could be steep enough to cause a
hazard to small craft. The thermal trough and the high pressure will
both weaken allowing winds and seas to subside Saturday, then a weak
cold front will slip through Saturday night into Sunday morning. The
main effect with this front will be stronger winds but still below
advisory level, mainly from Cape Blanco north. Another thermal
trough will set up next week with and extended period of small craft
advisory north winds and steep seas. Early indications are that the
thermal trough could become quite strong toward the end of next
week. /FB

&&

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

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 2 AM PDT Saturday
        for PZZ356.
     Small Craft Advisory for hazardous seas from 2 PM this afternoon
        to 2 AM PDT Saturday for PZZ350-356-370.
     Small Craft Advisory until 2 AM PDT Saturday for PZZ376.
     Small Craft Advisory for hazardous seas from 2 PM this afternoon
        to 8 AM PDT Saturday for PZZ376.
     Small Craft Advisory from 2 PM this afternoon to 2 AM PDT
        Saturday for PZZ350.

$$

25/10/08



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