NWS Medford, OR wrote its last area forecast discussion before the first event at Jul 31, 9:35 PM PST, 2 hours 25 minutes earlier.
Area forecast discussion, Jul 31, 9:35 PM PST, 2 hours 25 minutes before
Area Forecast Discussion
National Weather Service Medford OR
1035 PM PDT Wed Jul 31 2024
Updated AVIATION and MARINE sections
.DISCUSSION...A "front" of smoke has traveled from the north and
is beginning to affect portions of the Umpqua and Rogue Valleys.
The Illinois Valley may not be far behind. Have updated the
forecast to account for this in the next couple of hours, but it
is worth noting that the HRRR smoke model is not seeming to
initialize very well. That being said, we may get a little relief
from the smoke tomorrow afternoon and evening. Otherwise, will
continue to monitor for any additional updates. For more
information on the forecast, please see the previous discussion
below. -Schaaf
&&
.AVIATION...01/06Z TAFS...Widespread IFR/LIFR marine stratus
will impact the coast overnight into Thursday morning, but also
pressing inland into the Coquille Valley at Coquille/Myrtle Point.
The lower conditions will last until 16-18Z Thursday before
clearing to VFR. Expect lower ceilings to return Thursday evening.
VFR will prevail inland for the next 24 hours, except wildfire smoke
will become much more widespread overnight into Thursday. Earlier
today, the smoke briefly lowered visibility to IFR at Roseburg
(along with an MVFR ceiling), before vertical mixing pushed the
smoke out to the south and east and eventually overcame the
Rogue/Illinois Valleys this evening. All of Roseburg, Medford
and Klamath Falls will likely see at least some visibility
reductions due to wildfire smoke/haze on Thursday, generally in the
3-5 mile range. Visibility due to smoke could even be IFR or
lower at times closer to the eastern Lane/Douglas fires and also in
portions of NE California due to smoke emanating from the Park
fire. -Spilde
&&
.MARINE...Updated 830 PM Wednesday, July 31, 2024...North winds
and steep seas gradually diminish tonight into Thursday. Expect
areas of low clouds, patchy drizzle and reduced visibility in fog
near the coast. Conditions remain fairly calm Friday and north
winds over the weekend are likely to remain below advisory levels.
A stronger thermal trough is possible next week. -Smith/Spilde
&&
.PREV DISCUSSION... /Issued 458 PM PDT Wed Jul 31 2024/
DISCUSSION...Current satellite shows the smoke from the fires in
Lane County has moved into Douglas County including Roseburg with
less than a mile visibility. This smoke will continue moving
south this evening, so parts of Jackson and Josephine counties,
including Medford, could see smoke impacts from this string.
Stratus is still present at the coast and offshore, but there is
some sunlight coming through.
This afternoon has a jump in heat with highs from the mid-70s at the
coast to near triple digits for west side valleys. Temperatures will
not recover much overnight, and there is only a 10-20% probability
for Medford to fall below 65 degrees, and a 30-40% probability for
Roseburg. This heat will only increase for inland locations Thursday
with highs in the 100-105 degree range for west side valleys
(including the Klamath River and Shasta valleys). With this in mind,
a Heat Advisory will be in effect tomorrow afternoon through
tomorrow afternoon for west side valleys. Friday morning's
temperatures will be similar to Thursday.
Checking back into cloud cover, there will be stratus once again at
the coast that will likely reach parts of the Coquille Basin. Being
in between the high pressure to the east and low pressure to the
west gives northern California and Southern Oregon the position to
gain southerly winds back tomorrow. There will be an increase in
high clouds that come from the south through the day tomorrow.
However, this southerly flow will bring smoke from the Park Fire in
Northern California to Siskiyou and Modoc counties tonight and it
will continue moving into southern Oregon through the day tomorrow.
Tomorrow afternoon and evening will be the worst for the Rogue
Valley and east into Klamath Falls. With the continued issue of
worsening air quality, an Air Quality Alert has been issued through
Friday for Klamath and Lake counties. Intermittent smoke is
possible in Jackson, Josephine and Eastern Douglas counties.
By the end of the work week, thunderstorms are in the forecast.
Starting Friday afternoon, the main area will be the Cascades,
northern Klamath County and parts of Siskiyou County. This trend
continues with more confidence on seeing thunderstorms in northern
Lake and Klamath counties Saturday afternoon with SPC guidance
showing a 40-50% probability of thunderstorms in the area. Ensembles
are showing that areas east of the Cascades could see a few
hundreths for rainfall, and overall less than a tenth of an inch is
in the forecast, although locally higher amounts are possible.
-Hermansen
AVIATION...01/00Z TAFS...IFR/LIFR marine stratus is affecting the
immediate coast near Cape Arago, just offshore of Bandon, near
Cape Blanco, and also south of Pistol River to Brookings. These
ceilings will press inland about 10 miles tonight (to include North
Bend), but a little farther than that into Coquille/Myrtle Point
over interior Coos County. These last until 16-18Z Thursday before
clearing to VFR.
VFR will prevail inland for the next 24 hours, except wildfire smoke
will become much more widespread overnight into Thursday. Earlier
today, the smoke briefly lowered visibility to IFR at Roseburg
(along with an MVFR ceiling), before vertical mixing pushed the
smoke out to the south and east. All of Roseburg, Medford and
Klamath Falls will likely see at least some visibility reductions
due to wildfire smoke/haze on Thursday, generally in the 3-5
mile range. Closer to the eastern Lane/Douglas fires and the Park
fire, visibility due to smoke could even be IFR or lower at times.
-Spilde
MARINE...Updated 230 PM Wednesday, July 31, 2024...North winds
and steep seas around 6 to 7 feet briefly return to an area between
Cape Blanco and Brookings through tonight. More low clouds and lower
visibilities are anticipated along the coast. Improved conditions
follow Thursday and Friday. North winds over the weekend are likely
to remain below advisory levels, although seas are anticipated to be
steep in the southern waters at times. Then, a stronger thermal
trough is possible early next week.
-Smith
FIRE...Issued 200 PM Wednesday July 31, 2024...High pressure builds
over the region resumes control today. This will bring the return
of hot temperatures and low daytime humidities, with triple
digits for West Side Valleys, and mid-upper 90s for East Side
likely lingering through the weekend and into early next week. The
peak of the heat is expected Thursday, and this is also when we
expect daytime humidities to bottom out. The flow turns southerly
on Thursday, and this will allow for an uptick in afternoon
breezes on Thursday, especially east of the Cascades and in the
Shasta Valley. Guidance has trended slightly stronger with
southerly winds, and this was enough to push conditions into the
critical category for portions of Siskiyou County and the southern
Oregon Cascades. This will mainly affect the Shasta and Scott
Valleys, but will include the eastern periphery of the Shelly fire
as well as the southern most portion of FWZ 623, south of Highway
140. Near critical conditions are possible for much of the East
Side and the rest of northern California on Thursday, but winds
won't quite reach criteria there. Recoveries will trend lower
Thursday and Friday mornings, with the poorest recoveries
(moderate to poor) expected Friday morning east of the Cascades
and across northern California. Recoveries improve Saturday and
Sunday mornings with the influx of monsoonal moisture.
This brings us to the thunderstorm potential for the weekend as
southerly flow pumps moist, unstable air into the region.
Thunderstorm chances enter the forecast first on Friday afternoon.
Moisture will just be entering the region, so chances (15-20%) are
limited to the higher terrain of western Siskiyou County, across the
Siskiyous and Cascades. Moisture and instability will be marginal
and there really isn't a clear trigger, but where the elements line
up best, which leads to the best chance for thunderstorms, is along
the Cascades from Crater Lake northward to areas eastward around
Chemult/Crescent.
Saturday and Sunday, however, moisture will be more widespread and
there is a more well defined trigger (moreso Saturday than Sunday).
These are the days we expect thunderstorm activity to peak,
including west of the Cascades, with slightly higher confidence for
Saturday being the more active day. Current guidance is increasing
confidence for scattered thunderstorms on Saturday, especially east
of the Cascades.
The nocturnal thunderstorm threat is not out of the question for
Friday night, it's just a matter of when the moisture arrives and
whether that lines up with any elevated instability and a trigger.
Instability looks muted on Friday night, but there is a fairly
decent trigger coming through late Friday night into early Saturday
morning and this raises the concern for nocturnal storms. In
addition, any lingering cloud cover Saturday morning could impact
thunderstorm potential for Saturday afternoon.
Subtle changes in these elements could lead to big changes in the
forecast, and at this point in the forecast, it's challenging to be
confident in any of the details. Stay tuned for updates, with
changes to the forecast likely over the coming days. /BR-y
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 2 PM to 8 PM PDT Thursday for ORZ623.
Heat Advisory from 2 PM Thursday to 8 PM PDT Friday for ORZ023-
024-026.
CA...Red Flag Warning from 2 PM to 8 PM PDT Thursday for CAZ280>282.
Heat Advisory from 2 PM Thursday to 8 PM PDT Friday for CAZ080-
081.
PACIFIC COASTAL WATERS...Small Craft Advisory until 2 AM PDT Thursday
for PZZ356-376.
&&