Scientific Forecaster Discussion
fxus66 kmfr 261028
Area forecast discussion
National Weather Service Medford or
328 am PDT Mon Jun 26 2017
Latest observations at this hour show some weak and isolated
convection over the coast and North Western portions of Douglas
County. Behind this convection, relatively drier air is starting
to push into southern Oregon and northern California. The
probability for additional thunderstorms this morning is quite
low with the elevated drier air moving in.
As for later today, no major changes to the forecast except for
removing the chance for thunderstorms in southern Modoc County.
Otherwise, we have high confidence that we will see convection
east of the Cascades today. The reason for this confidence is the
broad upper level destabilization as the low moves through in
addition to being positioned under the left exit region of the
upper level jet. These features should break down convective
inhibition during the day and allow surface heating to kick off
storms. Also, the cloud cover from the convection last night is on
the way out. The models handled this cloud cover quite well
giving US even more confidence in the probability of convection.
The only uncertainty that remains is the exact location of the
storms. It appears they will start out in the northern portions of
lake and Klamath counties before the storms dive a bit farther
south Monday evening. However, conceptual thinking should also
allow for some storms over Josephine and Jackson counties. Dew
points are also sitting in the upper 50's, which does suggest
there will be some potential instability over US tomorrow.
Regarding severity, the Storm Prediction Center has US in a
marginal risk, which seems fairly appropriate given the forecast
for 0-6km shear and moisture near the surface. Wouldn't be
surprised if one or two storms become severe tomorrow evening over
our entire County Warning Area. At this time, it seems more probable over the east
As for Tuesday evening, we have a slight chance for some
thunderstorms in southern Siskiyou County. Confidence is low for
this event as there appears to be a little upper level energy
pushing through. This appears to be enough for some of the models
to initialize convection.
Aside from thunderstorms, flow will turn generally zonal with
some northwest flow during the later part of the week. As a
result, look for partly cloudy skies with highs in the 80's.
Aviation...26/06z taf cycle...along the coast, expect MVFR/IFR
ceilings to continue through the next 24 hours. VFR conditions
will continue everywhere inland from the coast through the taf
period. Isolated thunderstorms are possible over inland areas
tonight, then scattered thunderstorms are expected tomorrow
afternoon along and east of the Cascades. Gusty winds are also
expected during the afternoon across much of the east side. -Bpn
Marine...updated 300 am Monday, 26 June 2017...south to
southwest winds and light seas will persist over the waters today
into tonight...becoming north late tonight. A disturbance moving up
from the south is bringing isolated thunderstorms and showers to
areas near the coast this morning. A thermal trough develops along
the coast Tuesday and strengthens on Wednesday. This is expected to
bring gusty north winds and steep to very steep choppy seas to the
waters. The strongest winds and seas are forecast from Cape Blanco
south but periods of small craft winds and seas are possible north
of the cape. These conditions may persist through late in the week.
Fire weather...updated 250 am Monday, 26 June 2017...isolated
thunderstorms are possible this morning as an upper trough
approaches, then storms will increase in coverage and intensity
in the afternoon and evening as the main trough arrives. The focus
for lightning is expected to be from the Siskiyous and western
slopes of the Cascades eastward. However isolated to scattered
storms are possible over western valleys in Jackson and eastern
Josephine County as well into western and central Siskiyou County
this afternoon and early this evening. It will be cooler today
compared to yesterday, but breezy west winds and continued low
humidities may fan any new fire starts. Gusty west winds with gusts
of 20 to 25 mph are expected to develop east of the Cascades this
afternoon and evening. Also of concern, is the potential for erratic
and gusty winds near storms today. Gusts of 40 to 50 kt are possible
near thunderstorms this afternoon and evening, especially for storms
that develop east of the Cascades.
Red flag warnings remain in effect for the potential of
increased initial attack activity. The rest of the week should be
quieter as cooler weather dominates. -Cc
or... red flag warning until 11 PM PDT this evening for orz621-623.
Red flag warning until 11 PM PDT this evening for orz624.
Red flag warning until 5 PM PDT this afternoon for orz620-622.
Red flag warning from 11 am this morning to 11 PM PDT this
evening for orz625.
California... red flag warning from 11 am this morning to 8 PM PDT this
evening for caz281.
Red flag warning until 11 PM PDT this evening for caz280.
Pacific coastal waters...none.