664
FXUS66 KMFR 030545
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1045 PM PDT Tue Jul 2 2024

.UPDATE...Updated aviation section for 06z TAFs.

&&

DISCUSSION...Clear skies and warm temperatures continue today under
a building upper level ridge. This ridge looks to remain in place
and guide conditions through the forecast period.

The immediate concern is for continued warming through the
weekend, and for lingering days of elevated heat into next week.
At their warmest, temperatures in Jackson, Josephine, and western
Siskiyou counties are forecast to reach between 110 and 115
degrees. NBM probabilistic guidance currently has a 40% chance for
temperatures in Medford to reach or exceed 115 degrees on Friday
and Saturday. Notably, 115 degrees is the highest official temperature
that Medford has ever seen. With constant additional daytime
heating, nighttime temperatures will rise to the mid to high 60s.
This combination of daytime heat and warmer nights will result in
conditions that may lead to heat-related illness for anyone in
these areas. An Excessive Heat Warning is in place from Thursday
at 8 AM through Monday at 9 PM to communicate these hazardous
conditions.

Central and eastern Douglas County will see temperatures between 95
and 110 degrees with nighttime lows in the low to mid 60s. Areas
east of the Cascades will see temperatures between 95 and 100 degrees
with nighttime lows in the high 50s. Conditions in these areas pose
a risk to individuals who have heat-related sensitivities. A Heat
Advisory is in place for from Thursday at 8 AM through Monday at
9 PM to communicate this hazard. Additionally, there are periods
of Warning-level heat around Klamath Falls and the Chemult-
Crescent area on Saturday. While this increased hazard is not
shown in these hazard products, people in these areas will want to
take additional care on Saturday.

While there are areas not under an official hazard, this should not
be interpreted as an absence of risk. NWS HeatRisk guidance does
show some amount of hazard anywhere that isn`t the peak of Mount
Shasta from Thursday through Monday. Being aware of proper hydration
and how you feel as well as being indoors during the hottest part of
the day is encouraged across the coverage area.

Fire weather is also a concern during this period. High temperatures
without additional moisture results in lower relative humidity
levels. RH values of 15% or below will be present over most inland
areas, which will help to dry out any fuels that are not already
dry. The combination of low RH values and gusty afternoon winds can
make any spark or ember a threat to travel and start a new fire. Any
activities that pose a fire threat should be avoided. Please see the
Fire Weather Discussion below for additional details.

Long-term guidance shows continuing stability, but with lower
temperatures. Temperatures in Medford only have a 30% chance of
being over 100 degrees on July 11th. Climate Prediction Center
guidance does keeps the areas under Above Average Temperatures and
Below Average Precipitation through July 26th. Long-term ECMWF and
GFS meteograms do not currently forecast any events like this one in
that timeframe. Small victories. -TAD

&&

.AVIATION...03/06Z TAFS...VFR will prevail through the TAF
period. Gusty afternoon winds will return tomorrow afternoon,
especially along the coast. Stratus is expected to build in along
portions of the coast tonight with IFR conditions possible.
Confidence is low that IFR conditions will build in at North Bend
due to persistent gusty north winds and a scattered ceiling
continues to be the most likely outcome tonight.
-Miles

&&

.MARINE...Updated 200 PM Tuesday, July 2, 2024...A strong thermal
trough will maintain strong north winds, reaching gales south of
Port Orford, and steep to very steep and hazardous seas for all
areas through late Wednesday. Winds will be strongest and seas
will be steepest during the afternoons and evenings. Conditions
improve somewhat late Wednesday night into Thursday as the thermal
trough pushes inland and expands northward. North to northeast
winds will ease some during this time, but seas and winds will
remain hazardous to small craft through the end of the week, with
hazardous warning level seas likely lingering through Thursday
night.

Conditions improve further over the weekend with sub-advisory
conditions possible. Strong high pressure aloft will disrupt the
thermal trough pattern, keeping winds in the 15 to 20 kt range with
about a 15% chance of winds approaching advisory criteria on
Saturday and Sunday. The thermal trough rebounds early next week,
with hazardous conditions likely returning at that time. /BR-y

&&

.FIRE WEATHER...Updated 200 PM Tuesday, July 2, 2024...

.Near critical fire weather possible today through the next week
for much of southern Oregon and northern California...

.RED FLAG WARNING IN EFFECT FROM WEDNESDAY EVENING THROUGH
THURSDAY MORNING FOR OREGON FIRE WEATHER ZONES 619/WESTERN 620 FOR
GUSTY NORTHEAST WINDS AND POOR HUMIDITY RECOVERY...

Fire weather concerns will remain elevated through the week, though
due to two different patterns. First, a strong thermal trough along
the coast will persist through Wednesday night. This will bring
moderate to locally poor overnight RH recoveries to ridges along
with gusty northeast winds of 15-25 mph with gusts to 30-40 mph to
the Coast Range/Kalmiopsis Wilderness tonight and again Wednesday
night. As is typical with this pattern, it tends to take a night or
two of persistent northeast winds to bring down RHs enough to
present critical conditions, and that will be the case this time as
well. Of the winds/RH combo required for critical conditions
tonight, gusty winds will meet the criteria, but RH recoveries won`t
quite be low enough (30-50%). The pattern starts to transition
Wednesday night, so winds will be weaker compared to tonight, but RH
recoveries will be lower (20-35%). Still, guidance suggested enough
of an overlap that critical fire weather conditions were identified
in these areas Wednesday night into Thursday morning. Have upgraded
the fire weather watch into a Red Flag Warning in effect 11pm
Wednesday through 8 AM Thursday.

In the meantime, this pattern will also lead to near critical
conditions for portions of the area this afternoon and again
Wednesday afternoon. Minimum humidities of 10-15% are expected in
western and central Siskiyou County with north winds of 10 to 15 mph
and gusts to 25 mph (strongest in the Shasta Valley near Montague).
Similarly, northeast winds also be near critical thresholds in the
Illinois Valley on Wednesday afternoon at 10-15 mph with gusts to 20
mph, and with minimum humidities of 10-15%. However, Intel on fuels
remains that the live fuels are not quite there while dead fuels
are. Therefore, will continue to headline the near-critical
conditions this week.

Strong high pressure aloft moves over the region for the latter half
of the week and through the weekend. The thermal trough will expand
northward, with weaker winds expected along the coast. Very hot
temperatures (100-110 degrees) and very low (low teens/single digit)
humidities are expected during this time away from the immediate
coast. While afternoon breezes won`t be quite as strong as today and
Wednesday, the extreme heat, and long duration of the heat will
allow even typically breezy afternoon conditions to result in
dangerous weather that is favorable for rapid spread of fire.

-Schaaf/BR-y

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning from 8 AM Thursday to 9 PM PDT Monday for
     ORZ024-026.

     Heat Advisory from 8 AM Thursday to 9 PM PDT Monday for ORZ023-
     025-029>031.

     Red Flag Warning from 11 PM Wednesday to 8 AM PDT Thursday for
     ORZ619-620.

CA...Excessive Heat Warning from 8 AM Thursday to 9 PM PDT Monday for
     CAZ080-081.

     Heat Advisory from 8 AM Thursday to 9 PM PDT Monday for CAZ084-
     085.

PACIFIC COASTAL WATERS...Gale Warning until 5 AM PDT Thursday for
     PZZ356-376.

     Small Craft Advisory until 5 AM PDT Thursday for PZZ350-370.

     Hazardous Seas Warning until 5 AM PDT Thursday for PZZ370.

&&

$$