Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Medford or
324 PM PDT Wednesday Apr 1 2015
Discussion...with the cold pool over the region showers are
building this afternoon. An upper level ridge builds in from the
west Friday...bringing a break in the showery pattern and shifting
the upper cold pool to the east. Stratus is expected to butt up
against the Siskiyous Thursday night...but with the clearing south
of the Siskiyous we are expecting similar low temperatures in
northern California and the east side. The upper level ridge
transitions east with a weak upper trough bringing another weak
system into the region Friday evening. The upper trough deepens
further Saturday with another...stronger and wetter system moving
in Saturday night.
Long term...Sunday through Wednesday night...after another 24 hours
of model runs since this time yesterday, it can still be said with
some confidence that conditions will be wetter and cooler than
normal for this time of year, at least during the long term
forecast. That being said, models have trended slightly warmer than
yesterday, but not by much, and with very little change in expected
impacts. Also like yesterday, the models are showing ridging and a
brief warming very late in the term. This still looks good for a
more Spring-like day next Wednesday, but if extended forecast models
are to be believed, more precipitation and cooler air can be
expected before next weekend. Until then, temperatures of 5 to 10
degrees below seasonal averages can be expected.
While confidence is above average for the wet and cool forecast,
there is still a good deal of uncertainty regarding timing and
strength of each individual wave of moisture and cooler air.
However, one event does stand out from the rest, and that would be a
deep trough and associated surface frontal system on Monday. With
snow levels of around 2000 feet, and a significant slug of moisture
moving onshore at the same time, this could amount to a rather
significant rain and snow event for our area, not to mention the
possibility of gusty winds along the coast and over the east side.
As mentioned before, there is little confidence in the details,
including precipitation amount and exact temperatures, but this is a
feature that should be closely monitored over the next several days.
Aviation...for the 01/18z taf cycle...mostly VFR conditions will
prevail through this evening, although showers and isolated
thunderstorms may bring localized areas of MVFR ceilings with terrain
obscuration along the coast and eastward to the Cascades this
afternoon. Gusty winds showers will diminish during the evening then
late night west side valley stratus is likely to produce MVFR ceilings
into Thursday morning. -Bpn/dw
Marine...updated 830 am PDT Wednesday 01 Apr 2015...current buoy
observations have shown that seas are building a bit quicker than
previously thought, so have adjusted the forecast accordingly, and
have bumped forward the start of the Small Craft Advisory to the
current time, rather than waiting until 18z. Numerous showers will
continue today, with a slight chance of afternoon thunderstorms.
Northerly winds increase through this evening, diminish slightly
late tonight, then increase again Thursday afternoon and evening.
The next cold front will arrive on Friday, with conditions remaining
unsettled through early next week. The strongest of multiple systems
expected this week is currently indicated to arrive Sunday night
California...freeze warning from 2 am to 9 am PDT Thursday for caz081-281.
Freeze warning from 1 am to 9 am PDT Friday for caz081-281.
Pacific coastal waters...Small Craft Advisory for winds until 11 PM PDT this evening for
Small Craft Advisory for hazardous seas until 5 am PDT Thursday