Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Medford or
309 PM PDT Wednesday Oct 22 2014

Discussion...the cold front is moving through the coastal waters
this afternoon. South winds are increasing across the Shasta
Valley and at the higher elevations. We are getting a lot of
downsloping across the Rogue Valley and this has kept rain our of
the area. A wave is expected to form on the front offshore and
this could delay the eastward movement further. As a result, gusty
winds will continue longer than expected and I have extended the
Wind Advisory overnight through Thursday morning. Unfortunately
this could also mean that rain may not move into the Rogue Valley
until midnight or so. The Klamath basin will see passing light

On Friday night..a strong low pressure will approach the coastal
waters from the southwest. This low pressure is forecast to move
northeast into the coastal waters on Saturday. Pressure gradients
increase significantly across the forecast area. Have increased
winds to high end gale in the coastal waters and in the Shasta
Valley. We may need to issue a high wind watch if next model run
continues with this trend. /Fb


Precipitation probabilities and amounts...
amounts in the coastal zones, thus far, this afternoon have mostly
been in the 0.25" to 0.75". Radar and satellite imagery indicate
that the moderate to heavy rain with the frontal boundary to be
moving onshore now, so expect precipitation amounts to be on the
increase over the next few hours. Rainfall amounts for this current
storm system have been adjusted down some today through Thursday
evening for areas inland from the coast, but have left 3 to 5 inch
amounts intact for the coast and coastal mountain areas, with most
of the rain there expected from now through 5am PDT Thursday. We
expect 1.3 to 2.3 inches across Douglas County, 1-3 inches across
Josephine County, and 0.50" to 1.5" across Jackson County. On the
low end, in the east side valleys, we expect 0.10" to 0.50", lowest
far eastern areas.

The front will push inland tonight through Thursday, with most of
the rain across the interior west side tonight through Thursday
morning, and most of the rain east of the Cascades expected on
Thursday. The front will dip to southeastern sections and weaken
later on Thursday, and then the front waves back north as a warm
front Thursday night through Friday. Friday afternoon through
Saturday morning looks to be a relative lull in the precipitation
for areas away from the coast and not in south flow favored
locations as a strong low form between 130 west and the Oregon
coast. This front will move onshore Saturday with showers behind it
even into Sunday, so the weekend looks generally wet. It should be
noted, however, that the timing of precipitation is a lower
confidence forecast parameter than the presence of it in the
forecast, so it will not be a washout of a weekend for all
locations. Precipitation on Sunday may wane over central and
southeastern sections.

Numerical models indicate about two frontal systems next week with
Monday being dry for most locations away from the coast. Timing of
the fronts next week is a bit in question, but suffice it to say
that the weather pattern does look to remain active with a frontal
system every 2-3 days. Also, the overall parent trough over the area
sinks southward next week, so expect snow levels will likely come
down some, into the 5000 to 7000ft range. Btl


Aviation...based on the 22/18z taf cycle...
a frontal system will continue to push toward the coast today with
increasing south and southwest winds at exposed locations and those
that channel winds from that direction. Low level turbulence is
likely for much of the area.

For areas along and near the Coast Range this wind will remain a few
thousand feet above the surface resulting in a high potential for
low-level wind shear, to include at koth, where the surface winds
will be relatively weak and of a somewhat different direction than
aloft through the late afternoon or early evening. Gusty southwest
winds are unlikely to reach the surface until the front moves
onshore late this afternoon and evening. Expect widespread MVFR ceilings
today in light to moderate rain along and near the Coast Range. Rain
will become moderate to heavy later this afternoon and into the
evening, with IFR expected as the front moves onshore this evening
and for a portion of the overnight. Total terrain obscuration is
expected along the Coast Range through the forecast period.

Inland, VFR will prevail through the daylight hours today east of
Interstate five. MVFR ceilings and terrain obscurations will increase
along and west of the Cascades this evening through Thursday as the
frontal boundary moves across the area. Btl


Marine...updated 1130 am PDT Wednesday 22 Oct 2014...
unsettled conditions will continue to impact the area through the
next week. The first of several frontal systems will continue to
pass through the coastal waters today, producing gales and very
steep and hazardous seas throughout the day. Although winds will
decrease behind the front this evening, seas will remain elevated
and steep as moderate swell continues. After a brief lull in winds
on Thursday, another strong front will impact the coastal waters
Friday night into Saturday, producing another round of strong winds
and choppy, steep seas. Models have backed off a bit on timing
and strength of this second system, so there have been a number of
changes to the forecast. Suspect that the front will produce gales,
but overall strength of the winds and height of the seas will be
less than today's event. Conditions will improve through the
remainder of the weekend, and after another brief round of calmer
winds and seas, another front is expected early next week.


Mfr watches/warnings/advisories...
or...Wind Advisory until 11 am PDT Thursday for orz031.

California...Wind Advisory until 11 am PDT Thursday for caz081.

Pacific coastal waters...Small Craft Advisory for winds until 5 am PDT Thursday for
Small Craft Advisory for hazardous seas until 8 am PDT Friday
for pzz350-356-370-376.
Gale Warning until 11 PM PDT this evening for pzz350-356-370.
Hazardous seas warning until 11 PM PDT this evening for
Small Craft Advisory for winds until 2 am PDT Thursday for
Gale Warning until 2 am PDT Thursday for pzz376.



National Weather Service Glossary of Abbreviations