Strong high pressure aloft combined with a hot air mass already in place made for very hot conditions over southern Oregon.
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The episode as NWS MFR wrote it up.
Strong high pressure aloft combined with a hot air mass already in place made for very hot conditions over southern Oregon.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Medford, OR wrote its last area forecast discussion before the first event at Sep 5, 9:38 PM PST, 2 hours 22 minutes earlier.
Area Forecast Discussion
National Weather Service Medford OR
1038 PM PDT Sat Sep 5 2020
.UPDATE...A few updates were made this evening, primarily to
upgrade the Heat Advisories to Excessive Heat Warnings, and to raise
some additional Heat Advisories. Also, the marine discussion has
been updated.
With smoke expected to push farther east by tomorrow, daytime
temperatures are expected to easily push triple digits and beyond
for much of Jackson and Josephine Counties, and western Siskiyou
County. Portions of Curry County and even the Siskiyou and southern
Cascades will also see much warmer than normal highs, with many
locations expected to meet or break daily record highs. Smoke may
still linger in some areas, and temperatures will remain slightly
cooler there, but heat will be the general rule for the area. More
details on the heat headlines can be found at PDXNPWMFR.
Speaking of smoke, the latest runs of our smoke models have the
smoke tilting more to the east tomorrow, eventually leading to
clearing for much of Oregon's West Side, but no such luck for
northern California or the East Side, where smoke may actually
become worse than it has been for the past day or two. Air Quality
Advisories remain in place to account for this.
Lastly, there have been significant upgrades to the Fire weather
forecast, leading to extensive Red Flag Warnings. More on this
can be found in the fire discussion below, and at PDXRFWMFR. -BPN
&&
.AVIATION...For the 06/00Z TAFs...Smoke will remain thick from
northern California into Jackson, Klamath, and Lake Counties and
eastward through Sunday evening. This will continue to reduce
visibilities down to MVFR over most of northern California and
locally around southern Klamath County, possibly IFR in western
Siskiyou County near the Red Salmon fire.
Also, IFR is expected late tonight into early Sunday morning over
the coastal waters and near shore north of Cape Blanco. Elsewhere,
VFR with clear skies will continue into Sunday evening. -DW
&&
.MARINE...Updated 900 PM PDT Saturday 5 September 2020....A thermal
trough will build near the coast tonight. North winds will increase
into Sunday evening with seas high and very steep in the outer
waters south of Bandon. These very steep seas will be around 9 to 12
feet beyond 30 nm away from shore. Within 10 nm from shore, seas
will be around 5 to 7 feet. Localized gusts nearing gale strength
are expected Sunday afternoon and evening from near Cape Blanco
southwestward to 5 to 30 nm offshore from Gold Beach.
North Winds will decrease Monday morning with steep seas lowering to
around 7-9 feet across areas north of Cape Blanco and near shore
south of Cape Blanco, while seas remain very steep in the southern
outer waters.
The thermal trough will move offshore Monday night into Tuesday.
This will start a trend of diminishing seas but bring east winds to
areas north of Cape Blanco. This will generate cross seas with steep
seas likely continuing in the outer waters north of Cape Blanco
Monday night through Tuesday while lingering fresh swell in the
outer waters south of Cape Blanco results in steep seas Monday night
into Tuesday morning.
The thermal trough will remain offshore and weaken Wednesday with
weaker winds and lower seas likely for the remainder of the week.
-Miles/DW
&&
FIRE WEATHER...Updated 800 PM PDT Saturday 5 September 2020...The
Red Flag Warnings in effect for today have been allowed to expire.
There will be a brief break in the critical conditions across the
area, but it will remain hot, with numerous heat headlines in
effect.
All the ingredients are in place for a significant and widespread
east wind event starting Monday night and lasting into at least
Tuesday evening. The operational models and most, if not all,
ensemble members are in good agreement showing an upper level
trough (inside slider) moving south into northeast Oregon Monday
with a dry cold front moving into the area. This pattern is
expected to result in gusty north to northwest winds and low
relative humidity Monday afternoon east of the Cascades, followed
by steady moderate to strong east winds across the entire area
Monday night into Tuesday night. Winds will be strongest over the
higher terrain along the Cascades and West Side. Models all show
a very tight pressure gradient along the Cascades which is
usually a recipe for moderate to strong winds. Would not be
surprised if wind gusts exceed 40 mph for the mid slopes, ridges
and exposed areas along the Cascades and 30-35 mph in the higher
terrain and exposed areas west of the Cascades Monday night into
Tuesday morning.
Temperatures would remain quite hot west of the Cascades, but would
trend cooler on the East Side. However, humidities would suffer
greatly, dropping to minimums in the single digits to low teens
across nearly the entire area, and recoveries becoming poor for a
significant portions of the region. The timing of when we expect
critical conditions to develop have not changed much, so with
increased confidence, we have upgraded nearly the entire forecast
area to a Red Flag Warning, with various starting and ending
times based on expected conditions. See PDXRFWMFR for details on
each zone.
Some of the models suggest the gradient along the Cascades may relax
later Tuesday evening overnight Tuesday, so we could see east winds
beginning to diminish along and west of the Cascades during this
time. However, there is a chance that critical conditions could
linger along and west of the Cascades through Wednesday morning,
thus although the new Red Flag Warnings expire Tuesday evening, a
Fire Weather Watch is in effect for the Cascades and most points
west for Tuesday night into Wedensday morning.
Forecasts and Warnings will be updated as needed, so keep an eye
out for the latest products. -Petrucelli/BPN
&&
.PREV DISCUSSION... /Issued 200 PM PDT Sat Sep 5 2020/
DISCUSSION...05/12Z NAM/GFS/EC in.
A hot and dry forecast remains in place through next weekend,
though it may be a tad cooler Tuesday and again toward the end of
next week.
Strong high pressure is currently centered over Utah and will
remain there today. Flow aloft has become more southwesterly and
this has shunted off smoke from California wildfires to the east.
However, another wildfire closer by is now contributing more smoke
locally.
The high will retrograde back west Sunday into Monday, as a long
wave trough digs into the Great Plains and Intermountain states.
The ridge will set up shop offshore Monday.
Inland temperatures will respond accordingly. Today will be a bit
cooler, but still quite hot. At this time, it looks like the
hottest day will be Sunday, and Monday will only 1-3 degrees
cooler.
A Heat Advisory remains in effect through Monday. While the
daytime highs are very hot, the nights are getting longer and this
allows more overnight cooling, allowing some respite from the
heat. See PDXNPWMFR for more details.
The trough digging into the intermountain states will eventually
affect the area, bringing cooler northerly flow. The east side
will see quite a bit of cooling Tuesday, and the west side will
cool off a bit as well. This pattern will also bring low level
easterly flow to the ridges, and overnight humidity recoveries,
which won't be all that great to begin with, will get worse Monday
night and Tuesday night. While it will be cooler inland, this
pattern will bring warm and very dry conditions to the coast,
with temperatures above 90 degrees possible for much of the coast
Tuesday. With the dry conditions and gusty winds, a fire weather
watch is in effect for Monday night into Tuesday. See PDXRFWMFR
for details.
The trough will move off to the east Tuesday into Wednesday, and
the offshore ridge will build back in from the west, moving
onshore Thursday. This will bring another warming trend to the
area Wednesday into Thursday.
The ridge will then weaken in place Friday into Saturday as a weak
trough moves in from the west. Temperatures will cool during this
interval, but it will still be quite hot inland.
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 8 PM PDT this evening for ORZ624-625.
Red Flag Warning from noon to 11 PM PDT Monday for ORZ624-625.
Red Flag Warning from 10 AM Tuesday to midnight PDT Tuesday
night for ORZ615-618-624-625.
Excessive Heat Warning until 11 PM PDT Monday for ORZ024-026.
Heat Advisory from 11 PM this evening to 11 PM PDT Monday for
ORZ022.
Red Flag Warning from 11 PM Monday to midnight PDT Tuesday night
for ORZ616-617-619-620-622.
Fire Weather Watch from late Tuesday night through Wednesday
morning for ORZ616-617-619>623.
Red Flag Warning until 8 PM PDT this evening for ORZ623.
Red Flag Warning from noon Monday to midnight PDT Tuesday night
for ORZ621-623.
Heat Advisory from 11 PM this evening to 11 PM PDT Sunday for
ORZ028.
Red Flag Warning until 8 PM PDT this evening for ORZ622.
CA...Red Flag Warning from noon to 11 PM PDT Monday for CAZ284-285.
Red Flag Warning from 10 AM Tuesday to midnight PDT Tuesday
night for CAZ281-282-284-285.
Red Flag Warning from 11 PM Monday to midnight PDT Tuesday night
for CAZ280.
Fire Weather Watch from late Tuesday night through Wednesday
morning for CAZ280-282.
Excessive Heat Warning until 11 PM PDT Monday for CAZ080-081.
Red Flag Warning until 8 PM PDT this evening for CAZ285.
Pacific Coastal Waters...Small Craft Advisory from 11 PM this evening
to 5 PM PDT Monday for PZZ350-356-370.
Hazardous Seas Warning from 5 AM Sunday to 5 PM PDT Monday for
PZZ356-376.
Hazardous Seas Warning from 5 AM Sunday to 5 AM PDT Monday for
PZZ370.
Small Craft Advisory from 11 PM this evening to 5 AM PDT Sunday
for PZZ376.The national radar mosaic for the moment the first event began.
2 excessive heat. Local standard time, as filed.
Reported high temperatures in this zone ranged from 87 to 104 degrees, and the reported low temperatures ranged from 47 to 68 degrees.
Reported high temperatures in this zone ranged from 95 to 102 degrees, and the reported low temperatures ranged from 46 to 58 degrees.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2020Every state in 2020This day in weather historyWarnings in Oregon, September 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 909238, 909244.