Special Weather Statement, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
857 AM PDT Fri Sep 10 2021

.DISCUSSION...A very moist air mass is over the area this morning
with a PW on the Medford balloon sounding this morning of 1.29
inches. This brought welcome rainfall to all areas east of the
Cascades overnight into this morning and even some wetting
rainfall on many area fires from the west side Cascade Foothills
southward into portions of western Siskiyou County. Rain amounts
east of the Cascades were largely 0.25-0.50 of an inch with local
amounts more than 0.75 of an inch. West side areas that got rain
last night mostly had 0.10-0.25 of an inch, but there was a sharp
cutoff to the rainfall - little or no rain occurred last night
mainly west of a line from Roseburg to Grants Pass to Brookings. A
brief look at web cams this morning even showed a covering of snow
on top on Mt. Shasta. Related to that, a landslide occurred on the
north side of the mountain again, which

The area of steadier rainfall is exiting Lake and Modoc counties
now. Still, there are plenty of upper dynamics (forcing) and
thermodynamics (instability) to generate isolated to scattered
showers and thunderstorms from the Cascades eastward today. Some
are already developing near the Cascades. This is due to an upper
trough swinging through. The axis of the trough will push east of
the area this evening and the thunder risk will end. West of the
Cascades, it should be mostly dry this afternoon with clouds and
sun. West winds should push low-level smoke out of the Rogue Valley
at least briefly this evening. Short wave ridging moves in Saturday.
Depending on how much smoke output remains, HRRRsmoke guidance is
showing low- level smoke returning to Jackson/Josephine counties
on Saturday. It should also be noted that smoke impacts will
likely persist for a large portion of the east side on Saturday.

A dry upper trough will swing by to the north of the area on
Sunday. Dry weather is expected most of next week, but, as the
night shift noted, ensemble guidance is showing the potential for
some rain again by next weekend. -Spilde

&&

.AVIATION...10/12Z TAFs...MVFR with areas of IFR/LIFR conditions
will persist at the coast this morning with gradual improving to VFR
in the afternoon. Then expect areas of MVFR/IFR cigs/vis to develop
along the coast this evening. Inland... MVFR cigs will spread into
the Umpqua this morning, including at KRBG, with conditions
improving to VFR in the early afternoon. Elsewhere, expect areas of
MVFR cigs in light rain this morning along with possible
thunderstorms. Also expect widespread MVFR visibilities along with
localized IFR visibilities from smoke through this afternoon. Smoke
is expected to improve this afternoon and evening. Thunderstorms are
expected for areas from the Cascades east this afternoon with MVFR
cigs and strong, gusty outflows possible. -CC

&&

.MARINE...Updated 830 AM PDT Friday 10 September 2021..North winds
and seas will continue to lower this morning, then expect light
winds and seas through tonight. Then the thermal trough will
redevelop Saturday and strengthen Sunday into early next week.
This will bring strong north winds and steep seas to the waters
south of Cape Blanco on Saturday. Winds and seas will increase
further Sunday and Monday and a west-northwest swell builds into
the waters and combines with building wind seas. By late Sunday
afternoon, steep to very steep seas may develop for areas south of
Cape Blanco with steep seas and gusty winds developing north of
Cape Blanco. Gusty winds and elevated seas may persist through the
middle of next week. -CC/Spilde

&&

.PREV DISCUSSION... /Issued 315 AM PDT Fri Sep 10 2021/

DISCUSSION...A significant upper trough is moving inland and
generating plenty of showers and a few thunderstorms over the
forecast area this morning. Precipitable water values of 1.05
inches are being observed, about 50% above normal, over much of
the area. We've observed a tenth of an inch in Western Siskiyou
County, no doubt beneficial to firefighting efforts in that area.
Only one cloud to ground lightning flash has been observed so far,
and that's been in Western Siskiyou County.

Models show precipitation continuing through this morning, with some
lightning expected, mainly from the Western Siskiyou County
northward to areas around the fires in Eastern Douglas County...and
points eastward. The most significant energy arrives this morning
between 4am to 7am and will likely deliver more in the way of
heavier rain and some lightning. Gusts to 40 mph have been
observed with some heavier showers this morning over the Siskiyou
Mountains, so we expect that potential to continue this morning. We've
examined whether current rainfall rates will warrant any flash
flooding concern for wildfire burn scars or otherwise, and we
don't expect any flooding concerns at this time. Rainfall rates
could reach about 0.25 inches per hour, and we expect totals to
get up to around 0.5 inches from the Cascades eastward. Lesser
amounts are expected west of the Cascades. There will be sharp
gradient from significant rainfall along the Cascades to little to
no rainfall from around Roseburg southward to the Illinois
Valley.

Later today, some daytime heating and instability will align with
the energy/dynamics moving southwest to northeast, and this
intersection looks most likely over Northern Klamath and Northern
Lake Counties. Instability peaks early this afternoon as the cool
pool of air aloft moves overhead, and there is a marginal risk for
severe thunderstorms due to this favorable environment for storms.
The energy moves north and east out of the forecast area this
evening, moisture decreases, and the chance for showers and storms
decreases.

Relatively quiet weather is expected from tonight through
much of next week. Smoke conditions should improve today for most
areas. Smoke could increase this weekend with warming
temperatures, but some of this rainfall could maintain improvement
in air quality for a bit longer into the weekend. Temperatures
will generally trend warmer this weekend into the middle of next
week, with one notable bit of energy moving through Sunday
afternoon, just enough to bring breezier conditions and maintain
westerly winds aloft. Ensembles continue to point towards
increasing chances for rain for much of the forecast area by
Saturday, Sep 18. Specifically, about 85% of European, Canadian,
and American ensemble members suggest some rainfall next weekend.
Aware of how these Sep fronts can often fizzle, with models
generally overforecasting rainfall late in the summer, we should
temper expectations with the models at this point. Still, rainfall
is in the forecast, and we expect the next chance to be next
weekend. Lightning isn't expected to accompany this rainfall, and
it could be more significant in amounts and coverage but more
focused from the Cascades westward. Keene

AVIATION...10/06Z TAFs...IFR/LIFR conditions will spread across the
coast and coastal valleys overnight, persisting into Friday morning.
Over inland areas...thick smoke from the fires will result in areas
of MVFR/IFR visibilities downwind of the fires into Friday morning,
including Medford and Klamath Falls. The lowest visibilities will
mostly be from the Cascades east and Siskiyous south. Scattered
showers will become more widespread across northern California and
southern Oregon through Friday morning along with isolated
thunderstorms. Sandler

MARINE...Updated 200 AM PDT Friday 10 September 2021..Winds
have decreased overnight and light north winds and  seas are expected
today through Friday night. Then the thermal trough will redevelop
Saturday and strengthen Sunday into early next week.  This will
bring strong north winds and steep seas to the waters south of Cape
Blanco on Saturday. Winds and seas will increase further Sunday and
Monday and a west-northwest swell builds into the waters and
combines with building wind seas. By late Sunday afternoon, steep to
very steep seas may develop for areas south of Cape Blanco with
steep seas and gusty winds developing north of Cape Blanco. Gusty
winds and elevated seas may persist through the middle of next week.
-CC

FIRE WEATHER...Updated 300 AM PDT Friday, 10 September
2021...The main concern through this morning will be moderate to
strong outflow wind gusts near thunderstorms and the potential
for new lightning-caused wildfire starts. A tenth to a quarter
inch of rain has accompanied showers this morning, and a handful
of cloud to ground lightning flashes have been observed in
Siskiyou and Modoc Counties. In short, more rain than lightning is
being observed so far with this system moving through. Still,
can't rule out lightning outside of heavier showers, and we
maintain a Red Flag Warning for most areas from the Cascades
eastward and Siskiyous southward.

Thunderstorm potential west of the Cascades will decrease later
in the morning, but more significant energy will arrive from the
south, bringing increased lightning (with significant wind gusts
and outflows possible) potential for areas east of the Cascades.
Most of Fire Weather Zone 625 and eastern through northern 624
will be fair game in thunderstorm potential through this
afternoon. For this reason, a Red Flag Warning will continue into
the afternoon for those areas, while the Red Flag Warning for
areas south and west of this area ends later this morning. Please
see the Red Flag Warning text for details.

Elsewhere, excellent RH recoveries are expected this morning
except the high terrain of Siskiyou County and in Modoc and
Eastern Lake County late tonight into Friday morning.

Thunderstorms will no longer be an issue this evening as the best
dynamics will be northeast of our area. We'll see a return to dry
and stable conditions Saturday through at least the middle of
next week with thunderstorms chances practically zero.
-Petrucelli/Keene

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 5 PM PDT this afternoon for
     ORZ617-623>625.

CA...Red Flag Warning until 5 PM PDT this afternoon for
     CAZ282-284-285.

Pacific Coastal Waters...Small Craft Advisory from 11 AM Saturday
     to 1 PM PDT Sunday for PZZ356-376.

MAS/NSK/CC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEDFORD OR
1035 AM PDT FRI SEP 10 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0800 AM     HEAVY RAIN       1 SW ALTAMONT           42.19N 121.74W
09/10/2021  M0.48 INCH       KLAMATH            OR   TRAINED SPOTTER

            24-HR TOTAL.

&&

MTS

Special Weather Statement
National Weather Service Medford OR
1151 AM PDT Fri Sep 10 2021

CAZ081-083-084-ORZ029>031-101930-
North Central and Southeast Siskiyou County CA-
Central Siskiyou County CA-
Northeast Siskiyou and Northwest Modoc Counties CA-
Central and Eastern Lake County OR-
Northern and Eastern Klamath County and Western Lake County OR-
Klamath Basin OR-
1151 AM PDT Fri Sep 10 2021

...Strong thunderstorms will impact portions of northeastern
Siskiyou, northwestern Modoc, southwestern Lake and southeastern
Klamath Counties through 1230 PM PDT...

At 1149 AM PDT, Doppler radar was tracking an area of developing
strong thunderstorms along a line extending from near MacDoel and
Tennant to Bly. Movement of storms was northeast at 30 mph.

HAZARD...Winds in excess of 30 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible. Dangerous lightning strikes.

Locations impacted include...
Klamath Falls, Tulelake, Dorris, Merrill, Beatty, Gerber Recreation
Site, Macdoel, Campbell And Dead Horse Lakes, North Fork Sprague
River Trailhead, Currier Spring Trailhead, Bly, Tennant, Miller
Island Klamath Wildlife Area, Worden, Lookout Rock Trailhead, Keno,
Sprague River Park, Sprague River, Moore Park and Mount Hebron.

This includes the following highways...
 US 97 in Oregon between mile markers 274 and 291.
 US 97 in California between mile markers 23 and 54.
 Klamath-Lakeview Highway 140 in Oregon between mile markers 3 and
63.
 Lake of the Woods Highway 140 in Oregon between mile markers 67 and
68.
 Highway 66 in Oregon between mile markers 50 and 59.
 Highway 70 in Oregon between mile markers 1 and 6.
 Highway 139 in Modoc County California between mile markers 47 and
50.
 Highway 139 in Siskiyou County California between mile markers 1 and
5.
 Highway 39 in Oregon between mile markers 1 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4259 12056 4149 12191 4178 12236 4286 12103
TIME...MOT...LOC 1849Z 233DEG 27KT 4258 12085 4177 12182

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...30 MPH

Stavish

Special Weather Statement
National Weather Service Medford OR
1234 PM PDT Fri Sep 10 2021

CAZ083-084-ORZ029>031-102015-
North Central and Southeast Siskiyou County CA-
Northeast Siskiyou and Northwest Modoc Counties CA-
Central and Eastern Lake County OR-
Northern and Eastern Klamath County and Western Lake County OR-
Klamath Basin OR-
1234 PM PDT Fri Sep 10 2021

...Strong thunderstorms will impact portions of northeastern
Siskiyou, northwestern Modoc, southwestern Lake and southeastern
Klamath Counties through 115 PM PDT...

At 1231 PM PDT, Doppler radar was tracking strong thunderstorms
along a line extending from near Macdoel to near Bly to near
Paisley. Movement of storms was northeast at 30 mph.

HAZARD...Winds in excess of 30 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible. Brief very heavy rain and dangerous lightning may
         also occur.

Locations impacted include...
Klamath Falls, Tulelake, Merrill, Paisley, Newell, Quartz Mountain
Snow Park, Beatty, Gerber Recreation Site, Campbell And Dead Horse
Lakes, North Fork Sprague River Trailhead, Chewaucan Crossing
Trailhead, Currier Spring Trailhead, Bly, Government Harvey Pass, Cox
Pass, Lookout Rock Trailhead, Barnes Valley At Gerber Reservoir,
Sprague River Park, Summer Lake and Dairy Point Campground.

This includes the following highways...
 Highway 31 in Oregon between mile markers 68 and 111.
 Klamath-Lakeview Highway 140 in Oregon between mile markers 6 and
70.
 Highway 70 in Oregon between mile markers 1 and 6.
 Highway 139 in Modoc County California between mile markers 44 and
50.
 Highway 139 in Siskiyou County California between mile markers 1 and
5.
 Highway 39 in Oregon between mile markers 1 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4259 12036 4162 12171 4171 12186 4198 12190
      4218 12172 4301 12076
TIME...MOT...LOC 1931Z 240DEG 28KT 4270 12044 4177 12169

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...30 MPH

Stavish