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Area forecast discussion 
National Weather Service Medford or
801 PM PDT Friday Sep 19 2014

Discussion...20/00z NAM in.

Low level offshore flow is in place over the Medford County Warning Area with
clear skies everywhere...even over the coastal waters.

There is a weak Rex block along the West Coast with the ridge axis
over the Washington/Oregon/British Columbia coast and a cutoff low
just southwest of Point Conception. This setup will make for a hot
and dry Saturday over the area with near record high temperatures
over the inland areas.

The Block will break down Saturday night into Sunday as the ridge
moves east and the cutoff low begins to lift out as a strong long
wave trough approaches from the west. Fog will return to the
coastal areas beginning Saturday night. The cutoff low will be
near the Idaho/Oregon/Nevada triple point Sunday afternoon and a
short wave rotating around it will induce some instability over
Southern Lake and Modoc County...so a slight chance of
thunderstorms is in the forecast for that area Sunday afternoon
and evening. Model lifted indices indicate that there may be some
activity over the Cascades as well...and that will be looked at in
more detail later. Sunday will also be around 5 degrees cooler
than Saturday over the inland areas.

Extended discussion from the Friday afternoon afd...on Monday 500mb
heights will fall as a weakening cold front approaches the
coast...continuing a gradual cooling trend and bringing some
increasing winds to areas east of the Cascades. The European model (ecmwf) brings a
shortwave trough along the coast and just enough energy and
instability may exist over the Cascades for a thunderstorm or two.
Therefore...have kept that in the forecast. This weak front should
pave the way for a stronger frontal system arriving Tuesday night
into Wednesday. This system has the potential to bring wetting
rains to most of the forecast area...first from a cold front that
will likely affect areas along and west of the Cascades Wednesday.
Then...the upper trough axis swings over the area Wednesday night
into Thursday with enough moisture and instability to bring
showers to both the west and east side. This would be the first
significant rain east of the Cascades in more than a month...so
agricultural interests should take note if making decisions that
are based on rainfall potential. Its still early and confidence in
these transition season rain events is typically low...and
confidence in this system is low to moderate. Favoring the rain is
the fact that models are in generally good agreement with good run
to run consistency. Current projections suggest an inch of rain
possible at the coast with a half inch over high terrain areas
including the Cascades and western Siskiyou County...and a quarter
inch possible over valleys.

Model agreement falls away behind this system...with the GFS
suggesting upper ridging and the European model (ecmwf) showing another frontal
system moving in. The naefs shows considerable spread in ensemble
member solutions for Saturday and Sunday. Thus...we have trended
towards climatology for precipitation chances toward the end of
the week.

&&

Aviation...based on the 20/00z taf cycle...ceilings will remain
VFR through the next 24 hours. The combination of east winds and a
drier air mass is expected to prevent the return of cloud cover
tonight along the coast. Gusty north winds will continue through
this evening, but should weaken considerably overnight. Smoke from
area wildfires will increase again over the next 24 hours,
particularly near and west of Happy Camp, leading to localized
areas of reduced visibilities. -Bpn

&&

Marine...updated 230 PM PDT Friday 19 Sep 2014...a thermal trough
will continue to strengthen through this evening. Expect gusty
north winds through tonight, with the strongest winds over the
outer waters south of Cape Blanco. Winds should stay below gale
strength, but will be on the high end of Small Craft Advisory
criteria. Steep to very steep wind driven seas will also continue
into tonight. Winds will decrease and become southerly on Saturday
morning as the thermal trough weakens, but seas will remain steep
as northwest swell builds into the waters. Light to moderate
southerly winds and diminishing seas are forecast for Sunday into
Tuesday morning. A series of fronts will begin to impact the area
Tuesday, with periods of increased winds and heavy seas through
the remainder of the week. -Bpn

&&

Climate...this Summer continues to be on pace to be the hottest
Summer on record for Medford...when averaging high and low
temperatures from June 21 through today. In fact...right now the
average temperature so far this Summer is a significant 1.3
degrees above the previous record hottest Summer...which was
2013. With near-record heat expected tomorrow...its almost a
certainty that 2014 will Register as the hottest Summer on record
for Medford. Its not surprising that with the drought and this
record-heat...which are likely closely related...this has been an
active fire season with wildfires still ongoing.

&&

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

California...none.

Pacific coastal waters...Small Craft Advisory for winds until 2 am
PDT Saturday for pzz350-356.
Small Craft Advisory for hazardous seas until 5 am PDT Saturday
for pzz350-356-370.
Small Craft Advisory for winds until 11 am PDT Saturday for
pzz370-376.
Small Craft Advisory for hazardous seas until 11 am PDT Saturday
for pzz376.
Hazardous seas warning until 11 PM PDT this evening for pzz376.

$$

15/15/15

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