NWS Medford, OR wrote its last area forecast discussion before the first event at Sep 7, 7:42 PM PST, 1 hour 56 minutes earlier.
Area forecast discussion, Sep 7, 7:42 PM PST, 1 hour 56 minutes before
Area Forecast Discussion
National Weather Service Medford OR
842 PM PDT Mon Sep 7 2020
.UPDATE...A few changes were made this evening to further refine
the winds expected over the next 24 hours. The major changes
include the ending of the Excessive Heat Warning for Jackson,
Josephine and Siskiyou Counties, although heat Advisories will
continue along and wets of the Coastal Ranges through Tuesday.
Gusty winds in excess of 40 mph are now producing blowing dust
and lowered visibilities across much of the East Side. A Blowing
Dust Advisory and a Wind Advisory continue there through this
evening. North winds this evening will shift to the east tonight,
and winds will begin to increase over area ridgelines, especially
the Cascades and the Coastal Ranges. The winds will align roughly
with the southern Rogue Valley near Ashland, and wind gusts are
expected in excess of 35 mph from Ashland through Talent to
Phoenix and possibly Jacksonville. A Wind Advisory has been issued
there beginning tonight, and east winds could persist well into
Wednesday afternoon.
Very warm and exceptionally dry conditions will combine with gusty
winds to produce critical fire weather conditions as well. More
information on this can be found below in the Fire Discussion.
-BPN
&&
.AVIATION...For the 08/00Z TAFs...The main aviation impact during
this TAF period will be strong, gusty northeast through east winds
overnight into Tuesday morning leading to low-level wind speed shear
(LLWS) for most terminals. This includes the strongest winds over
ridges and across much of the east side. Wind gusts to 35kt are
possible at KLMT, where an airport weather warning is in effect
through this evening.
Marine stratus hugging the coast north of Cape Blanco will push well
offshore overnight into Tuesday. Wildfire smoke from all the fires
to the south is already getting pushed southward away from our area,
but smoke from the fires to the north will increase...especially
east of the Cascades as winds continue to shift.
A dry front will push through overnight with north winds becoming
northeast, then easterly. Enough of an inversion will develop around
1500 feet AGL for winds to decouple (ease) at the surface for most
valley locations, with the strongest winds expected over the higher
terrain. But, this will result in LLWS of 30-40 kt at that level
above KOTH, KRBG and KMFR. Some valleys oriented more to these wind
directions could see some significant wind gusts overnight into
Tuesday morning. Conditions should be mostly VFR aside from any
wildfire smoke visibility reductions. -Spilde/DW
&&
.MARINE...Updated 800 PM PDT Monday 7 September 2020....A thermal
trough near the coast will move offshore overnight into Tuesday
night bringing gusty northeast winds north of Cape Blanco with the
highest seas in the outer waters and fresh swell dominating south of
Cape Blanco. We've maintained a small craft advisory during this
time for most areas except the immediate coast due to a mix of fresh
swell and east winds creating a chaotic sea state, but this is
especially true beyond about 20 nm from shore.
The trough will remain offshore through Thursday, weakening with
time. Winds and seas will be relatively light Wednesday into
Saturday. -Spilde/DW
&&
FIRE WEATHER...Updated 800 PM PDT Monday 7 September 2020...A
critical fire weather pattern will remain in place into Wednesday.
Over the East Side, it will be a near constant, but porpoising
event with critical condition this afternoon and evening and again
Tuesday afternoon and evening due to gusty winds and low RH. From
the Cascades west, it will be a constant event into Wednesday
afternoon due to gusty winds combined with low RH during the day,
and gusty winds with poor RH recoveries at night. Red Flag
Warnings are in effect for the entire Medford forecast area. Winds
will diminish Wednesday, but conditions will still be critical
across the West Side. From Thursday on, it will remain hot and
very dry, but there will be a very gradual cooling and moistening
trend. Winds will diminish, and this will be the primary factor in
keeping overall conditions below Red Flag Warning criteria.
&&
PREV DISCUSSION... /Issued 257 PM PDT Mon Sep 7 2020/
DISCUSSION...On satellite a haboob with a mass of smoke can be
observed at the leading edge of the dry front of the approaching
dry front. Have added blowing dust to the forecast east of the
Cascades, mainly below 5k ft, above which it should be dispersed
by the higher wind speeds. The first instances of blowing dust
will arrive in NE Lake County in approximately two and a half
hours. Have visibility reduced to 2 1/2 SM in the forecast but,
observations from within the dust cloud reveal visibilities much
lower in the most concentrated pockets down to 1/2 SM.
Added a freeze warning for some valleys late Tuesday night east
of the Cascade crest north of Chiloquin in Klamath County,
surrounding the Fort Rock area in Lake County, and around Alturas
in Modoc County. Some MOS guidance shows temperatures higher than
what is currently forecast, but this seems the more reasonable
MinTs at the moment. This is also assuming that an inversion sets
up in these locations, which at the moment, model soundings are
showing. It is possible though for frost surrounding the above
mentioned areas on Tuesday night from Sprague River north in
Klamath County, and for a larger area surrounding Fort Rock. Did
not issue a frost advisory for similar areas tonight due to the
high wind speeds expected all night.
Wanted to message a caution associated with the high wind speeds
that hasn't been yet, and that is for the possibility of downed
power lines and/or power poles. Similarly, downed tree limbs,
especially along ridge tops where winds will be strongest, pose a
threat to hikers, campers, and those driving mountain roads.
Not much change to the temperature forecast for the area,
especially in the short term where heat risk remains for areas
west of the Cascades. Areas from the Cascades east will see a
significant cool down Tuesday, while the coast will observe some
of it's warmest temperatures all year. Brookings has the chance to
observe a particularly strong chetco effect, but have held off
going with the hottest temperatures in the guidance due to
uncertainty in the wind direction forecast.
Wednesday and Thursday hot temperatures move back inland and MaxTs
will reach into the upper 90s. However, overnight lows should be
better and this prolonged heat risk will finally subside. On
Thursday winds, mostly over the water, become southerly and cause
a surge of marine stratus to move north. This is expected to be
dense enough to cause trace and minimal measurable amounts of
precipitation along the coast. Also, it will create very foggy
conditions along the coast and over the marine waters at least
through friday and possibly into the weekend. -Miles
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Blowing Dust Advisory until 1 AM PDT Tuesday for ORZ029>031.
Freeze Watch from late Tuesday night through Wednesday morning
for ORZ029>031.
Wind Advisory until 11 AM PDT Tuesday for ORZ030-031.
Heat Advisory until 11 PM PDT Tuesday for ORZ021-023-024.
Red Flag Warning until midnight PDT Tuesday night for
ORZ624-625.
Red Flag Warning until 5 PM PDT Wednesday for ORZ616>623.
Heat Advisory until 11 PM PDT Tuesday for ORZ022.
Red Flag Warning from 11 AM Tuesday to 11 AM PDT Wednesday for
ORZ615.
Wind Advisory from 5 AM Tuesday to 2 PM PDT Wednesday for
ORZ026.
CA...Blowing Dust Advisory until 1 AM PDT Tuesday for CAZ084-085.
Freeze Watch from late Tuesday night through Wednesday morning
for CAZ085.
Wind Advisory until 11 AM PDT Tuesday for CAZ085.
Red Flag Warning until midnight PDT Tuesday night for
CAZ284-285.
Red Flag Warning until 5 PM PDT Wednesday for CAZ280.
Red Flag Warning from 11 AM Tuesday to 11 AM PDT Wednesday for
CAZ281.
Red Flag Warning until 5 PM PDT Wednesday for CAZ282.
Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT Tuesday for PZZ350-356.
Heat Advisory until 11 PM PDT Tuesday for PZZ356.
Small Craft Advisory until 5 AM PDT Wednesday for PZZ370-376.