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Area forecast discussion 
National Weather Service Medford or
139 PM PDT sun Apr 26 2015

Discussion...26/12z NAM/GFS in.

A long wave ridge is now building into the West Coast. It will
push a warm front north through the area today...and that is
bringing some cloud cover to the area...mostly from the Cascades
west. The coastal waters and coast will get some spotty very
light precipitation. One RAWS station...Charlotte Ridge...reported
0.01 inches as of 1208 PDT.

Sunday night and Monday will be dry with very warm inland
temperatures. At low levels...the thermal trough will swing inland
over the west side valleys...bringing the warmest day of the
coming week to those areas. High temperatures will be 15 to 20
degrees above normal.

The ridge will break to the east of the area Monday evening. The
thermal trough will move over the east side Tuesday...and that
will be the warmest day of the week there. High temperatures will
be 15 to 20 degrees above normal. The exception will be near the
Cascades where it will be about as warm as Monday...but still
10-15 degrees above normal. This will be due to increasing cloud
cover ahead of the next system.

Speaking of which...a short wave ejected from the upstream
trough will move onshore Tuesday night...followed by the weakening
long wave trough Wednesday. The weakening cold front associated
with the short wave will move onshore Tuesday. It will bring some
light precipitation to the west side and possibly some showers
east of the Cascades. The front associated with the long wave
trough will move onshore Wednesday...but the storm track will have
migrated to the north by this time and it will just brush the
northern portions of the Medford County Warning Area. Little precipitation is
expected and what does fall will be limited to the northern
fringes of the Medford County Warning Area. Wednesday will be the coolest day of
the week for many inland locations...but temperatures will still
be around 5 degrees above normal just about everywhere but the
Umpqua basin.

In the wake of the front...offshore low level flow will set up
Wednesday night. It will be a relatively weak event.

Long term...Thursday through Sunday night...over the past 24 hours,
models have been able to find a bit more agreement between them.
However, the solutions today are quite a bit different than
yesterday, which was quite different than the day before that.
Despite the differences, the trend is clear: a dry long term
forecast with slightly warmer than normal temperatures. Considering
the relatively close agreement between the GFS and European model (ecmwf) solutions,
have relied on a blend of the two for today's forecast package.

With upper level troughing over the East Coast, and ridging through
the middle of the country, the West Coast is set up to reside under
a weak, but rather persistent trough through the long term. There
appears to be little in the way of moisture flow, which stays well
to our north, and virtually no upper level dynamics. This leads ME
to keep things on the dry side, although some scattered cloudiness
is likely through each day. The exception will be Saturday and
Sunday afternoons, as the European model (ecmwf) resolves moisture moving north along
the eastern side of the sierras, and this could help produce some
thunderstorms over the east side, mostly over Modoc and lake
counties. Given the time range, and the weak trough overhead, have
limited precipitation to a slight chance of showers and left out
mention of thunder. -Bpn

&&

Aviation...for the 26/18z taf cycle... VFR ceilings are expected to
prevail at most locations as a warm front moves through this
afternoon, though there is a small chance for MVFR ceilings to
affect the coast north of Cape Blanco. Partial mountain obscuration
is possible from the Cascades westward...mostly in the Coast
Range.

Tonight...models suggest enough moisture in the low levels along the
coast and in Umpqua valley to produce MVFR ceilings near Roseburg
and North Bend. Elsewhere...VFR conditions will continue through
tonight. -Bpn/sk

&&

Marine...updated 100 PM PDT Sunday, Apr 26, 2015...the warm front
will lift north of the forecast area this evening. A brief and weak
thermal trough expands northward from California overnight but north
winds are likely to remain below advisory criteria. South winds are
likely to develop again on Tuesday ahead of the next fairly weak
cold front. Stronger northerlies are expected behind this front on
Wednesday. Small Craft Advisory conditions are likely late Wednesday
into Thursday south of Cape Blanco. The latest GFS model run
suggests gales are possible Thursday. /Fb

&&

Mfr watches/warnings/advisories...
or...none.

California...none.

Pacific coastal waters...none.

$$

15/11/08

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