848
FXUS66 KMFR 021547
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
847 AM PDT Tue Jul 2 2024

.DISCUSSION...The forecast is on track for today. Warmer
temperatures are forecast across northern California and southern
Oregon, with highs rising between 2 to 5 degrees from Monday`s in
most areas. Temperatures will continue to rise through the week,
with hazardous heat present at the end of the week and into the
weekend.

Please see the previous discussion for more details about the
short- and long-term forecast as well as for critical fire weather
concerns. -TAD

&&

.AVIATION...02/12Z TAFS...Areas of MVFR or IFR ceilings are present
in the Coquille Basin,and this will lift later this morning.
Elsewhere VFR will be present through the TAF period. Gusty
afternoon and evening winds will continue today, especially west of
the Cascades where gusts could reach 30 kt.
-Hermansen/CC

&&

.MARINE...Updated 845 AM 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 400 AM Tuesday, July 2, 2024...

...Elevated to critical fire weather possible today through the next
week...

...FIRE WEATHER WATCH 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%). This combination could lead to
critical fire weather conditions and a Fire Weather Watch remains in
effect for Wednesday night into Thursday morning.

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%.

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. /BR-y

&&

.PREV DISCUSSION... /Issued 434 AM PDT Tue Jul 2 2024/

DISCUSSION...A ridge is building and this will guide the short
and long term forecasts with warm temperatures and dry conditions.
The Chetco effect was present yesterday afternoon, and this was
not presented well in the forecast. With this in mind, the highs
for Brookings the next few days have been increased and now show
highs in the 80s and near 90.

The streak of 90+ degree days in Medford started Monday afternoon
with a high right at 90. The concern for dangerous afternoon
temperatures will begin Thursday as the thermal trough moves inland.
Thursday`s main areas for the heat will be in the Rogue Valley and
in Siskiyou County valleys with highs in the low 100s. After, the
heat expands to more west side locations including the Illinois
Valley and Umpqua Basin, which equates to highs in the 100-110
degree range.

The heat will be the worst Friday into the weekend. The probability
of reaching highs of 110 degrees in Medford is 70-80% Friday and
Saturday afternoons. There is even a 35% probability to reach 115
Saturday in Medford. There will also be a factor of low temperatures
west side only falling to the low to mid-60s Friday and into the
weekend. With this in mind, it is crucial that precautions are taken
to prepare and deal with the heat.

With the heat concerns in mind, an Excessive Heat Watch exists for
most locations (with an emphasis on valleys) Thursday morning
through Sunday evening. Will continue reviewing the heat risk this
week, but for now west side valleys are certain to be under an
Excessive Heat Warning by the end of the week.

Early next week the ridge will move inland and temperatures will
fall from the weekend peak, although it will still be warm with
highs in the triple digits for the Rogue and Illinois valleys. -
Hermansen

AVIATION...02/12Z TAFS...Areas of MVFR or IFR ceilings are present
in the Coquille Basin,and this will lift later this morning.
Elsewhere VFR will be present through the TAF period. Gusty
afternoon and evening winds will continue today, especially west of
the Cascades where gusts could reach 30 kt.
-Hermansen/CC

MARINE...Updated 200 AM 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 400 AM Tuesday, July 2, 2024...

..Elevated to critical fire weather possible today through the next
week...

..FIRE WEATHER WATCH 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%). This combination could lead to
critical fire weather conditions and a Fire Weather Watch remains in
effect for Wednesday night into Thursday morning.

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%.

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.
/BR-y

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Watch from Thursday morning through Sunday
     evening for ORZ023-024-026-029>031.

     Fire Weather Watch from Wednesday evening through Thursday
     morning for ORZ619-620.

CA...Excessive Heat Watch from Thursday morning through Sunday
     evening for CAZ080>082-084-085.

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.

&&

$$