NWS Medford, OR wrote its last area forecast discussion before the first event at Aug 13, 9:59 AM PST, 2 hours 1 minute earlier.
Area forecast discussion, Aug 13, 9:59 AM PST, 2 hours 1 minute before
Area Forecast Discussion
National Weather Service Medford OR
1059 AM PDT Sun Aug 13 2023
...New Aviation Section...
.AVIATION (13/18Z TAFs)...
VFR conditions are expected throughout the valid TAF period with
one caveat being ceilings at KOTH tonight. As it stands, we are
seeing the potential for some clouds, but these may only be
scattered at 1000 feet. That said, it wouldn't be out of the
question to see thicker clouds develop which would yield MVFR or
even IFR conditions at KOTH. However, confidence is not high
enough for this to come to fruition at this time. Otherwise, high
pressure strengthening overhead today will lead to slightly
calmer afternoon wind and plenty of sunshine across the area.
Guerrero
&&
.PREV DISCUSSION... /Issued 905 AM PDT Sun Aug 13 2023/
DISCUSSION... This morning's satellite shows the marine stratus
burning off close to North Bend. Satellite also shows smoke from
the Bedrock and Lookout fires moving west. Today's winds will be
north/northeasterly and will pick up slightly tomorrow afternoon.
The triple digit highs are still on track this afternoon and our
heat products continue through the middle of the week. This
afternoon will be spent reviewing the thunderstorm chances over
the next several days. Please review the previous discussion for
more information. -Hermansen
AVIATION...13/12Z TAFs...Along the coast and just offshore. Marine
stratus will continue to persist north of Cape Blanco, including
North Bend with IFR ceilings for most of the morning. The TAF at
North Bend shows improving conditions around 18z, but this could end
up being delayed by an hour or so. Gusty winds start to develop
again this afternoon through the evening.
Inland, expect VFR conditions to continue through the TAF period.
-Petrucelli
MARINE...Updated 800 AM PDT Sunday, August 13, 2023...Winds have
eased up a bit, but moderate to occasionally strong north winds will
continue today, with Hazardous Seas Warning conditions south of Port
Orford and small craft conditions elsewhere.
Moderate to occasionally strong north winds will continue Monday,
with the strongest winds over the northern waters and beyond 10 nm
from shore. However the combination of winds and a fresh northwest
swell will result in Small Craft Conditions for most of the waters.
Seas on Monday will be a mix of wind seas, fresh swell, and a
northwest swell at 13 to 14 seconds. North winds will diminish late
Monday night into Tuesday, but it is likely that steep seas will
linger across the waters. Moderate to strong north winds are
expected to return around mid week. -Petrucelli
PREV DISCUSSION... /Issued 433 AM PDT Sun Aug 13 2023/
Updated Aviation Discussion.
DISCUSSION...Satellite imagery shows marine stratus across
portions of Coos County and offshore. Elsewhere, the area remains
cloud-free. This is indicative of a ridge of high pressure
strengthening its influence over our area which is also creating a
thermal trough which will be the main driver of the weather for
southern Oregon and northern California for the next few days.
The main component of the forecast will be the long-duration
heatwave that will continue. Temperatures across inland areas west
of the Cascades will likely reach the triple digits today.
Meanwhile areas east of the Cascades will see temperatures in the
mid to upper 90s. Even at the coast, temperatures will be hot
today reaching the upper 70s to low 80s. Monday will likely be the
hottest day with temperatures possibly reaching 110 degrees across
many of the west side valleys. East of the Cascades, temperatures
will be in the mid to upper 90s, and at the coast, temperatures
will be in the 70s and 80s once again. These temperatures will
remain 10 to 15 degrees above normal through the remainder of the
week before conditions begin to cool off for the weekend. During
this time, overnight temperatures will remain warm -- above 70
degrees in the West Side valleys and near 60 across the East
Side. This will likely prevent folks without air conditioning to
see much relief at night. As a result, an excessive heat warning
begins this afternoon and will continue through Thursday. Please
see the NPWMFR for more details.
The secondary portion of the forecast involves thunderstorm
chances. It is worth noting that high pressure and the thermal
trough is not really a pattern that would generally be conducive
to thunderstorms. However, ensemble guidance continues to show
moisture filter into the area with a minor weakness in the ridge
appearing either Monday or Tuesday. On Monday, the general thought
will be that the chances will be confined to northern California.
However, on Tuesday, the chances will spread into Oregon, largely
along the Cascade crest and areas immediately east of the crest.
In general, the thunderstorm chances will be around 15 to 20% or
less, and most likely tied to the terrain, if they form at all.
Still, it is worth noting the possibility.
The other portion of this weakness in the ridge will be breezy
winds along with the extremely dry air with the heat. This will
lead to elevated fire concerns. More information on that in the
fire section.
The ridge is expected to break down over the weekend, as a low
pressure system drives northward across California. This low will
bring monsoonal moisture with it and will create additional
thunderstorm chances for most areas in northern California as well
as for areas along and east of the Cascades. This will need to be
monitored as these thunderstorms could be impactful as conditions
try to recover from the long-duration heatwave. -Schaaf
FIRE WEATHER...Updated 300 AM PDT Sunday, August 13, 2023... Our
fire weather will of increased concern during the next week due
to extreme heat and dryness, especially today through Friday, and
also due to increased thunderstorm chances Monday through
Saturday.
Due to increased certainty in a very hot air mass with dry lower
levels and instability aloft, the Fire Weather Watch for the Flat
Fire near Agness during Sunday afternoon and evening, and Monday
afternoon and evening has been upgraded to a Red Flag Warning.
A Fire Weather Watch remains in effect for California Fire Weather
Zone 280, and Oregon Fire Weather Zones 616, 617, 619, 620, 621,
622, and 623 for Monday afternoon through Monday evening for gusty
winds and low relative humidity. We will wait for another model run
or two to get insight from the higher resolution models regarding
wind speeds. Winds will be near or at the lower end of criteria west
of the Cascades, at around 6 to 12 mph with gusts up to 20 mph.
These gusty afternoon winds will be seasonable, but will be near or
exceed critical levels when combined with the hottest and driest
weather of this episode. There is higher certainty that extreme heat
and dryness will be present.
Detail has been added to the thunderstorm forecast, particularly to
Monday and Tuesday. Beyond Tuesday, variability increase in the
forecast track of the large scale features driving the risk of
thunderstorms. The risk on Monday looks to be relatively modest,
though with sufficient moisture in the 700 to 500 mb layer to
support isolated coverage into northern California. 700-500 mb
moisture will increase over a broader swath of our area Tuesday,
with the lowest risk for the coastal counties, and Lake and Modoc
counties. -DW
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 11 PM PDT Thursday for ORZ021>024-
026-028.
Fire Weather Watch from Monday afternoon through Monday evening
for ORZ616-617-619>623.
Red Flag Warning until 8 PM PDT this evening for ORZ619.
Red Flag Warning from 2 PM to 8 PM PDT Monday for ORZ619.
Excessive Heat Warning until 11 PM PDT Thursday for ORZ025-027.
Heat Advisory until 11 PM PDT Thursday for ORZ028-029.
CA...Excessive Heat Warning until 11 PM PDT Thursday for CAZ080>082.
Fire Weather Watch from Monday afternoon through Monday evening
for CAZ280.
Heat Advisory until 11 PM PDT Thursday for CAZ084-085.
PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT this
evening for PZZ350-356-370-376.
Hazardous Seas Warning until 11 PM PDT this evening for PZZ376.
&&