NWS Medford, OR wrote its last area forecast discussion before the first event at Sep 7, 8:11 AM PST, 3 hours 13 minutes earlier.
Area forecast discussion, Sep 7, 8:11 AM PST, 3 hours 13 minutes before
Area Forecast Discussion
National Weather Service Medford OR
911 AM PDT Wed Sep 7 2022
.SYNOPSIS...A ridge of high pressure will give way to a weak
trough with elevated instability today. While we will see one last
day of hot temperatures across the inland portions of southern
Oregon, it is worth noting that this trough could bring some
elevated thunderstorms into the area from Siskiyou County
northeast across the Cascades and into the East Side. These storms
may not bring much in rainfall, but could bring gusty winds. This
trough will also bring about critical fire weather conditions to
many inland areas. The ridge of high pressure redevelops quickly
on Friday with east winds and additional hot temperatures and fire
weather concerns this weekend.
.UPDATE...
Convection continues this morning across the forecast area as a
plume of mid level moisture has kicked off a few thunderstorms.
Looking at some of the individual soundings this morning, we
decided to expand the slight chance of thunderstorm wording
westward to the coast. The KOTH BUFR sounding does show 100/200
j/kg of CAPE this afternoon, which is sufficient for some
lightning. Confidence is pretty low here given the HREF is not
showing reflectivity returns that far westwards. In any case, that
was the biggest change today. We're still forecasting a slight
chance of thunderstorms along and east of the Cascades today.
Thunderstorms should lean towards the dry side, although they may
be wet at times.
With regards to heat, we should be a bit cooler today given the
cloud cover. If we do mix down completely, then we should see 100
here in Medford. Heat impacts should be relatively lower today
given the cooler temperatures and cloud cover.
-Smith
&&
.DISCUSSION.../Issued 525 AM PDT Wed Sep 7 2022/
Radar continues to show some returns moving across
far eastern Lake County at the 4:30 AM hour. It is unlikely that
these returns are putting down any rain, but no lightning has been
recorded either. High resolution convection allowing models show
some mid level moisture meeting (PWats between 0.5 and 0.75
inches) with elevated instability and a weak trigger moving into
the area today. This could produce additional returns on the radar
with very little rain reaching the ground since cloud bases will
start around 10,000 feet today. With inverted V soundings and good
downdraft cape (~1200 J/KG), these thunderstorms could see some
gusty winds to 50 mph, particularly east of the Cascades in Lake
and Klamath Counties. It is possible that these downdraft winds
could travel several miles away from the parent thunderstorm.
While severe storms are not anticipated for our area, one or two
storms may overachieve, so stay tuned for any possible special
weather statements or severe thunderstorm warnings this afternoon
and evening.
Regarding the heat, we are on a downward trend with today being a
bit cooler than yesterday. Yesterday, we broke several records at
our climate sites, including at Medford (107/104 set in 1923),
Klamath Falls (99/95 Set in 2020), Montague (106/97 set in 1966),
and Mount Shasta City (103/94 set in 2021). Although today will be
hot once again, we are winding down. Our heat products will
continue today, please see the NPWMFR for more details. Expect
cooler temperatures for Thursday. However, this relief will be
brief as the ridge of high pressure and thermal trough quickly
redevelop. We could see additional periods of hot and dry
conditions Friday and Saturday.
Then, ensembles begin showing a cooler solution as a low pressure
system moves toward the Pacific Northwest. This low could combine
with moisture from Hurricane Kay in the eastern Pacific which
could generate additional thunderstorm chances beginning as early
as Sunday through Tuesday. Ensembles show quite a bit of spread,
so have gone with the National Blend of models as this seems to be
reasonable. Stay tuned to the forecast because this could be
another round of higher impact weather and will likely change as
ensembles begin to key in on the shift in pattern. -Schaaf
&&
.AVIATION...07/12Z TAFs...Over the coastal waters and along the
coast...VFR conditions prevail, but areas of IFR cigs/vsbys in low
clouds and fog will develop overnight into early Wednesday
morning. It will gradually clear to VFR along the coast Wednesday
morning, but the lower conditions will persist over the coastal
waters into Wednesday night. Over the remainder of the area...VFR
conditions will persist through Wednesday evening, except for
local MVFR vsbys in smoke near wildfires.
&&
.MARINE...Updated 800 AM PDT Wednesday 07 September 2022...A strong
thermal trough along the coast will weaken Friday. Strong north
winds and steep to very steep seas will persist into Friday. The
strongest winds and steepest seas will occur south of Cape Blanco in
the afternoons and evenings. Gale force winds will occur south of
Cape Blanco Wednesday afternoon through Thursday evening. Winds will
weaken Friday, but steep to very steep seas will persist through
Friday night, and areas of steep seas will persist through Sunday.
&&
.FIRE WEATHER...Updated 445 AM PDT Wednesday 07 September 2022...
An incoming upper trough today will bring moderate west southwest
winds to areas east of the Cascades with breezy to locally gusty
afternoon/evening winds from the Cascades east. Mid level
moisture will increase over the area from the south on Wednesday
while a dry lower level remains. This combined with daytime
instability and weak disturbances aloft will result in a chance
for thunderstorms Wednesday afternoon and evening, mainly across
northern California, far southern portions of the Cascades and
areas east of the Cascades. Overall, expect storms to be mainly
isolated but there is a potential for scattered storms especially
in northern/central Lake County. These storms are expected to have
higher bases and there will be a very dry sub cloud layer. As a
result, expect any thunderstorms that develop to have little or no
precipitation reaching the ground. These thunderstorms may
produce gusty, quickly shifting winds up to around 50 mph,
particularly in northern Klamath and Lake Counties. A red flag
warning for dry thunderstorms on dry vegetation remains in effect
for this afternoon and evening. Also areas east of the Cascades
will see gusty winds and low humidity Wednesday afternoon and
evening. Please see the RFWMFR for details.
As the upper trough moves eastward Wednesday night and Thursday,
expect a trend towards cooler daytime temperatures. However, there
will also be increased offshore northeasterly winds over the coastal
mountains Wednesday night, then gusty northerly winds for many
areas west of the Cascades on Thursday. These northerly winds
could funnel into the Illinois Valley and combine with dry
humidities bringing critical fire weather conditions there. Have
issued a fire weather watch for this area, but have not included
the Rum Creek Fire into the watch. However, will want a second
opinion to discuss with the incident meteorologists on site for
the final upgrade. It is also worth noting that on Friday and
Saturday west of the Cascades, hot, dry, breezy, and unstable
conditions are expected and could require additional fire weather
headlines, especially for the Rum Creek Fire.
Then, gusty offshore northeasterly winds are expected again
Thursday night and Friday morning, and may include areas in the
Southern Oregon Cascades as well as further west. Recoveries are
expected to be mainly moderate on the ridges during this period,
with isolated ridgetops seeing poor recoveries. However, north of
Crater Lake, we could see more widespread poor recoveries. These
winds continue to increase with very low daytime RHs. The
recoveries become poorer over a wider area on Friday night into
Saturday, and so have issued a fire weather watch for these area,
including for the Windigo Fire.
On Saturday, expect the hot, dry, and unstable conditions to
expand eastward, and the Windigo fire could see the need for
additional fire weather headlines as well. Lastly, fire weather
guidance is picking up on some gusty winds and low RHs for western
Siskiyou County on Saturday afternoon, however confidence is a bit
too low. This will bear watching as should this trend continue,
critical conditions could be possible for the Mountain and Mill
fires on Saturday.
Then beginning Sunday, monsoonal moisture and moisture from a
weakening tropical system will start to feed into the area with
thunderstorm chances develop by Sunday. Confidence is low in the
details of the forecast for this period and we will update as the
forecast confidence increases. -Schaaf
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR... Fire Weather Watch from late Thursday night through Saturday
morning for ORZ616-617-621>623.
Heat Advisory until 11 PM PDT this evening for ORZ024>028.
Heat Advisory until 11 PM PDT this evening for ORZ029>031.
Red Flag Warning from 2 PM this afternoon to 9 PM PDT this
evening for ORZ623>625.
Fire Weather Watch from Thursday afternoon through Thursday
evening for ORZ620.
CA...Excessive Heat Warning until 11 PM PDT this evening for CAZ080.
Red Flag Warning from 2 PM this afternoon to 9 PM PDT this
evening for CAZ280-281.
Heat Advisory until 11 PM PDT this evening for CAZ081-082.
Heat Advisory until 11 PM PDT this evening for CAZ083>085.
Red Flag Warning from 2 PM this afternoon to 9 PM PDT this
evening for CAZ284-285.
Pacific Coastal Waters...Small Craft Advisory until 2 PM PDT this afternoon for PZZ376.
Small Craft Advisory until 5 AM PDT Friday for PZZ350-356-370.
Hazardous Seas Warning from 2 PM this afternoon to 5 AM PDT
Friday for PZZ350-370.
Hazardous Seas Warning until 5 AM PDT Friday for PZZ356-376.
Gale Warning from 2 PM this afternoon to 5 AM PDT Friday for
PZZ356-376.
&&