Wildfire in Oregon, June 1 to 5, 2023

Area Forecast Discussion
National Weather Service Medford OR
931 PM PDT Wed May 31 2023

.DISCUSSION...An evening update is not necessary. Day-to-day
coastal conditions will be seasonable through Tuesday, with areas
of mainly night and morning stratus, mainly north of Cape Blanco.
Inland, as expected, the radar was much less active today...just a
few stray showers in Lake and Modoc counties. Our region is now mostly
between two troughs. The second trough, now offshore, will track
east across the area Thursday. This will limit the extent of the
first degree of a warming trend, with high temperature readings
only higher by up to a few degrees. It will generate instability
ahead of it, with isolated thunderstorms expected Thursday
afternoon northeastward and eastward from the Mt. Shasta area,
with the highest probability for Modoc and southern Lake counties.

The models have been very consistent in indicating a brief episode
of ridging for Friday with several degrees of warming and a stable
air mass. Saturday will be a transition day, with another several
degrees of warming. The ridge will shift east while monsoonal
moisture makes its way northward up the spine of the Sierra
Nevada. The most likely scenario is that scattered capped/low
topped cumulus clouds will pop up over the higher terrain, but
there is around a 5% to 10% probability of thunderstorms over the
higher terrain of northern California and the Winter Rim near the
border of Klamath and Lake counties.

Sunday likely begins a lengthy episode of more active weather.
Very warm weather during the weekend is expected to lead into hot
weather Monday and Tuesday. An influx of mid-level moisture into
our area is expected as a closed low moves into and lingers over
California. Thunderstorms will mostly produce above average
amounts of precipitation. But, at least isolated to scattered
coverage of thunderstorms is forecast for day-to-day varying
portions of our area each day through mid-week.

&&

.AVIATION...01/00Z TAFs...VFR conditions will prevail across the
area through the TAF period. The only exception will be areas of IFR
in the southern Umpqua (south of Roseburg) and portions of the
Coquille valley late tonight and Thursday morning as well as a
potential (25% chance) for areas of IFR at the coast, including
KOTH. Confidence is low in IFR ceilings developing at KOTH at this
time and have kept VFR in the KOTH TAF, which is supported by high
resolution ensemble models. Will continue to monitor this. Chances
for thunderstorms are expected this afternoon and evening (10-20%)
in far E. Lake and Modoc Counties, with a similar pattern for
thunderstorm coverage tomorrow afternoon/evening, extending slightly
into E. Klamath County. -CC/CSP

&&

.MARINE...Updated 800 PM PDT Wednesday, May 31 2023...A thermal
trough pattern will continue through the week and into the weekend.
This will maintain strong gusty north winds and steep to very steep
wind driven seas. Gales with very steep and hazardous seas are
expected south of Gold Beach into tonight. For other areas south of
Bandon, conditions will remain hazardous to small craft into
tonight.

The thermal trough weakens late tonight into Thursday and this will
bring some improving conditions with gales easing for most areas
south of Gold Beach. Isolated gales are possible again Thursday
afternoon, however, but will remain south of Brookings and between 2
to 15 nm from shore. Seas will remain very steep and hazardous south
of Gold Beach through Thursday night, but conditions hazardous to
small craft will be limited to areas south of Cape Blanco by early
Thursday morning.

Winds and seas will continue to ease on Friday, but seas will remain
steep south of Cape Blanco during this time. The thermal trough
rebounds and strengthens over the weekend. Northerly winds could
reach gales for most of the waters and hazardous conditions will
return to all areas. -CC

&&

.PREV DISCUSSION... /Issued 242 PM PDT Wed May 31 2023/

DISCUSSION... Thunderstorm chances this afternoon will be concentrated
in the southeastern portions of the CWA in Modoc and Lake
counties. The stratus that was found on satellite this morning
across the Rogue Valley and Umpqua Basin has lifted and brought
plentiful sunshine this afternoon. Northern California and Modoc
and Lake counties have seen cumulus develop this afternoon.
Although this is where the cumulus will be concentrated, a few
cumulus clouds could be found for areas west of the Cascades.
Thursday will have similar areas for thunderstorms, although there
will be a 20-30% chance for thunderstorms added to western Lake
County and eastern Klamath County. The next few days will hold a
streak of light winds in the mornings and breezy conditions in the
afternoons.

After this cooler period, a ridge will build Friday over the
Rocky Mountain west, leaving us on the western periphery. This
will bring dry conditions to the CWA and there will be a warming
trend. By the weekend, high temperatures from Medford eastward
will be 5 to 15 degrees above normal for this time of year. Other
than a few spare 30s near Chemult and Crescent, lows will be in
the 40s Saturday morning. A trend of warmer mornings will continue
with more mid-40s/low 50s later this weekend and into the next
work week. These warming temperatures will expand a low heat risk
for most of the CWA this weekend. By Monday and Tuesday (June 5,
6), a moderate heat risk will be found for parts of the Rogue,
Klamath River and Shasta valleys.

Into early next week, a low that is offshore of southern California
will move inland. As explained in a previous discussion, this
will tear off monsoonal moisture and push it north. Thunderstorm
chances were kept in parts of Northern California for Sunday,
Monday and Tuesday. Sunday's 10-20% chance for thunderstorms will
be concentrated near the Cascades and Northern California. For
Monday and Tuesday, the thunderstorm chances (15-25%) will reach
eastern Jackson and Douglas counties. Overall, the area of concern
will be into the middle of the next work week with a low/moderate
heat risk and thunderstorm risk. -Hermansen

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT Friday
     for PZZ350-356-370-376.

Gale Warning until 2 AM PDT Thursday for PZZ356-376.

     Hazardous Seas Warning from 2 AM Thursday to 5 AM PDT Friday for
     PZZ356-376.

&&

DW/CSP