Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 291224
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
524 AM PDT Thu Jun 29 2017

DISCUSSION... High pressure, centered about 300 nautical miles
offshore, continues to dominate weather conditions across the
forecast area. Northwest flow continues aloft due to the fringe
effects of an upper level trough centered over the northern
Rockies. Little change is expected in the weather through the
forecast period as high pressure generally remains in control.
However, subtle variations in the pressure pattern across the
Pacific Northwest due to a weak upper level trough slipping
through the ridge Friday into Saturday are expected to cause the
marine layer to surge inland to approximately the Cascades Friday
through Saturday and could bring isolated thunderstorms to a few
locations from the Trinity Alps and Oregon Cascades eastward.

Along the coast and in the Umpqua Basin some marine layer drizzle
is possible Friday and Saturday, mainly in the nighttime and
morning hours. Temperatures along the coast are likely to warm
the most Sunday and Monday.

Inland it will be very warm with temperatures about 5 degrees
above normal, yielding highs in the upper 80s and lower 90s today
and Friday. We expect a cool down, especially on the West Side,
Saturday due to an increased marine layer influence in the form of
morning cloud cover and cooler boundary layer temperatures.

Friday afternoon through Friday night an upper level trough
driving the inland surge of the marine layer will bring
instability and a trigger for thunderstorms from the Oregon
Cascades and Trinity Alps eastward. Numerical model guidance
indicates moisture will be either insufficient to marginal for
thunderstorms in the mentioned area. Due to there being potential
and due to run to run variations in the models, have elected to
continue with a slight chance of thunderstorms across portions of
central and eastern Siskiyou County and from Crater Lake north and
eastward and along and near Winter Rim.

Thereafter, Saturday through next week, a new warming trend is
expected as highs reach 5-10 degrees above normal. The GFS 00Z run
is very much indicating a heat wave next week, with highs possibly
reaching 100F in Medford next Thursday afternoon. The ECMWF is
slower to build higher amplitude ridging across the Pacific
Northwest, so decided to go with a somewhat slower heat up than
the GFS indicates. Nonetheless, summer is surely here to stay over
the next week with at to above normal temperature continuing
through the forecast period. BTL

AVIATION...29/12Z TAF CYCLE...
low clouds and fog are more patchy this morning west of I-5. The
low clouds and fog (mvfr/ifr) should continue to expand early this
morning in the Umpqua Basin and coast and then erode back to the
beaches during the late morning into midday. Elsewhere, VFR
conditions will continue.
Sandler

MARINE...Updated 300 AM Thursday, 29 June 2017...
Gusty north winds and steep to very steep seas are expected
through early next week mainly south of Cape Blanco. Winds and
seas will ease tonight into Saturday morning then build on Sunday
into early next week. There is a possibility of gales beginning
late Sunday into Monday south of Cape Blanco.
Sandler

&&

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

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT this evening for
     PZZ356-376.
     Small Craft Advisory for hazardous seas until 8 AM PDT Friday
     for PZZ350-356-370-376.

$$


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