Scientific Forecaster Discussion
fxus66 kmfr 251906
Area forecast discussion
National Weather Service Medford or
1206 PM PDT sun Jun 25 2017
Aviation...25/18z taf cycle...VFR conditions will continue
everywhere inland from the coast through the taf period. Isolated
to scattered thunderstorms are expected to affect inland areas
this afternoon with the greatest threat over the mountains. Expect
gusty downdraft winds and lightning with any storms.
Thunderstorms may approach kmfr late this afternoon but are more
likely this evening into tonight. -Wright
Previous discussion... /issued 848 am PDT sun Jun 25 2017/
Discussion...morning temperatures are quite warm, about 5 degrees
higher than 24 hours ago. Afternoon high temperatures will be a
few degrees cooler than yesterday, but these readings will still
be dangerously hot. Please take precautions to stay safe in this
last day of serious heat. Dew point temperatures will rise
tonight, and low temperatures will still not offer a lot of
relief. Still, the heat wave for all practical purposes ends this
evening, and we transition towards a gradually cooling air mass.
Today we will spend time analyzing thunderstorm threat and
coverage. Morning data confirms the forecast for isolated to
scattered thunderstorms over much of the inland forecast area
today. Visible imagery and radar show a shower already formed this
morning at the southern edge of Siskiyou County, along broad
shortwave energy moving north into the forecast area this morning.
Additionally, latest hrrr forecast reflectivities show storms
forming mid afternoon over the Siskiyous and southern Cascades
then traveling north in the late afternoon.
We maintain generally a slight chance of thunderstorms tonight all
the way to the coast with upper level instability still showing
in the models and a hint of thunderstorms forming in Douglas
County tonight per the namnest output.
Tomorrow brings what will likely be the most lightning of the two
days to the forecast area, focused mainly from the Cascades
eastward. Please see the previous forecast discussion below for
more details on record temperatures, the thunderstorm threat, and
the eventual cooling trend.
Marine...updated 220 am Sunday, 25 June 2017...south winds will
persist over the waters today and Monday and bring continued fog
and low stratus. Seas will remain low through Monday. The thermal
trough returns Tuesday into Wednesday with gusty north winds and
steep to very steep choppy seas developing over 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. -Cc
Fire weather...updated 240 am Sunday, 25 June 2017...extremely
hot, dry weather conditions continue today and are helping to dry
fuels, setting the stage for possible fire starts as thunderstorms
develop late this afternoon through Monday evening. While heavier
fuels are still wet and do not necessarily support fire spread or
growth, finer fuels are near seasonal dryness levels. The
possibility of lightning caused fire starts may lead to increased
initial attack activity, and the fire weather watches and warnings
are primarily for this impact.
Models continue to show that thunderstorms are most likely over the
Siskiyous, southern Oregon Cascades, and eastward across northern
portions of Klamath County today into tonight. Over the west side
valleys models support the potential for scattered thunderstorms to
move into the valleys of Jackson and Josephine counties this evening
and tonight. The best chances for scattered storms to develop in the
western valleys is over Jackson County. Models show that storms may
be more isolated in Josephine County. While lightning may not be as
abundant over the western valleys, storms may be drier, especially
those that develop overnight, and valley fuels are drier. So
starts are possible. A red flag warning has been issued for
these western areas and is in effect from late this afternoon
through Monday. Red flag warnings also remain in effect for western
Siskiyou, the Siskiyous, southern Oregon Cascades and northern
Klamath County today through Monday.
Models continue to indicate that the best area for storms to develop
will shift northeastward by late Monday afternoon, mainly from
the Cascades eastward.
In addition to all this, gusty west winds will kick in as the system
moves through Monday afternoon and evening, especially east of the
Cascades. Thus, any new fires may be affected by winds. -Cc
Previous discussion... /issued 320 am PDT sun Jun 25 2017/
Discussion...two new record highs were set and two were tied
at our climate sites saturday: Roseburg new record of 103, old
record 97 in 1940, Mount Shasta new record of 97, old record 96
in 2006, Klamath Falls tied at 94, previously set in 2006, and
Montague tied at 101, previously set in 2006.
Little change has been made to the forecast this morning. Latest
model runs are on track with keeping the hot upper ridge over the
area but shifting it slightly east by afternoon. South flow
increases by then with the approach of an upper low off the
California coast. A broad short wave lifting north across
northern California can be seen well in a loop of the GOES-16 mid
level water vapor channel. This wave set off some storms over the
Sierra yesterday between Mammoth and Tahoe and will reach
Siskiyou and Modoc County this afternoon with increased
confidence to see developing thunderstorms of the isolated to
widely scattered variety. Precipitable water increases to over and
inch across the west side and instability strengthens with convective available potential energy
forecast to reach 1000 j/kg. With a hot dry boundary layer beneath
developing storms, some areas could see strong gusty storm
outflows today from the Cascades westward. Latest hrrr forecasts
have been consistent in targeting initial development in portions
of western Siskiyou County across the Siskiyous in the vicinity of
Mt. Ashland by around 3pm. Thereafter we should see some storms
develop across the east side and Cascades and things will be
moving south to north. Rain, wind, and locally heavy downpours
will likely accompany storms over the west side but things should
be mostly on the dry side out east where moisture will be thinner.
Looks like there is still the potential for activity to continue
in an isolated nature well into the evening but should die off
Monday the upper low moves across the region with cooler weather
and additional storms likely. Confidence is a little tricky here
because it appears the main forcing from the low may move through
earlier and this could result in less impressive afternoon
development. If things do align just right a few severe storms
will be possible over the Cascades and east side as instability
will continue to be high and an upper jet moves across providing
favorable wind shear.
An upper trough remains over the region through Wednesday with
mainly dry weather and seasonable temperatures. Then, warm and
dry weather should prevail through late week. There appears to be
another short wave from the west by around Friday night which
could provide an enhanced marine push and several degrees of
cooling for next weekend. -Stavish
or...red flag warning from 5 PM this afternoon to 11 PM PDT Monday
Fire Weather Watch from Monday morning through Monday evening
Heat advisory until 8 PM PDT this evening for orz023>028.
Excessive heat warning until 8 PM PDT this evening for
Red flag warning until 11 PM PDT Monday for orz621-623.
Red flag warning from 5 PM this afternoon to 5 PM PDT Monday for
California...heat advisory until 8 PM PDT this evening for caz080-081.
Excessive heat warning until 8 PM PDT this evening for
Red flag warning until 11 PM PDT Monday for caz280.
Fire Weather Watch from Monday morning through Monday afternoon