248
FXUS66 KMFR 020503 AAA
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1003 PM PDT Mon Jul 1 2024

Updated Aviation discussion.

.DISCUSSION...An update is not needed for this evening. Please see
the previous discussion for detail`s on the upcoming heat wave
later this week into the holiday weekend.


&&

.AVIATION...02/06Z TAFS...Areas of MVFR or IFR ceilings are expected
along the coast into Tuesday morning, including at North Bend
(KOTH). Elsewhere expect VFR through the TAF period. Gusty afternoon
and evening winds will continue today and again on Tuesday.  -CC


&&

.MARINE...Updated 800 PM Monday, July 1, 2024...A very strong
thermal trough will persist towards the end of the week. The Gale
Warnings are in place for this event south of Cape Blanco, with
steep to very steep seas expected elsewhere. The peak should be
Tuesday, although very little drop off in intensity is expected
Wednesday. As for the wind speeds expected during the peak of the
thermal trough, the gale force gusts of 35 to 45 kt are still
expected south of Cape Blanco, but there is a 20-40% chance that
gusts reach or exceed 50 kt Tuesday or Wednesday evening. With the
chance for gale force gusts remaining below 50% between Cape Blanco
and Cape Arago, a Hazardous Seas Warning is in place, but that is
not to say an isolated gust of gale force strength is not possible. -
CC/Schaaf


&&

.PREV DISCUSSION... /Issued 425 PM PDT Mon Jul 1 2024/

DISCUSSION...Mostly clear skies, with interruptions from terrain-
influenced cumulus, continue across northern California and southern
Oregon today. Afternoon winds will increase for most areas, with
those winds calming into the evening.

A building upper ridge will be the main influence in conditions for
at least the rest of the week and possibly into the weekend. High
temperatures are going to increase across the area through at least
Friday and Saturday. Most west side valleys will be over 100 degrees
by Thursday, with a 50% chance of highs at or over 110 on Friday and
Saturday. East side areas will be between 95 and 100 degrees, and
the coast will stay in the low to mid 70s.

An existing Extreme Heat Watch has been extended through Sunday
evening for continuing elevated daytime and nighttime temperatures.
An official hazard product through this period is a near certainty
for the Rogue, Shasta, Scott, and western Siskiyou County valleys.
Other areas, like the Illinois and Umpqua valleys, only reach hazard
thresholds periodically. Making a full and accurate hazard product
will benefit from another day of information.

The fact is that everywhere in the area that isn`t the peak of Mount
Shasta will see some amount of unseasonable heat during this period.
Considering NWS HeatRisk guidance, even the Oregon coast will see
Minor HeatRisk, with broad areas of Moderate and Major HeatRisk for
inland areas. Anyone who is extremely vulnerable to heat will want
to be very careful through this week. Everyone should stay hydrated,
should avoid outside activities during the hottest time of the day,
and should give themselves extra concern to avoid heat related
illnesses.

Fire concerns will also be elevated during this time, given the hot,
dry, and windy conditions. Please see the Fire Weather discussion
below for the full details, but high temperatures and no additional
moisture will bring a drop in relative humidities. Lower RH values
will help any fuels that aren`t already dry to become dry. Single-
digit RH values are expected east of the Cascades as well as into
Siskiyou, Jackson, and Josephine counties on Friday and Saturday.
With the availability of additional fuels as well as gusty afternoon
winds, even a single spark could start a wildfire. Please use extra
care or even completely avoid any activities that may ignite a
wildfire.

Long-term guidance shows temperatures "cooling down" into next week.
Medford still has a 50% chance of seeing temperatures above 100
degrees for next Monday though Wednesday, and other areas look to
stay similarly warm. So even if hazard products don`t continue, heat
and fire awareness are worth observing as these conditions continue
into the future. -TAD


FIRE WEATHER...Updated 200 PM Monday, July 1, 2024...

..Elevated to critical fire weather Tuesday through the next
week...

High pressure builds in tonight with very hot and very dry
conditions, and gusty afternoon winds likely through the next week.
This will also bring moderate to locally poor overnight humidity
recoveries to ridges including gusty northeast winds of 20 to 30 mph
with gusts to 45 mp to the Coast Range/Kalmiopsis Wilderness during
Tuesday night and Wednesday night. Extreme heat and elevated to
critical fire weather conditions are the theme for the next week.

The first episode of near critical weather to develop will be
minimum humidities of 10-15% in western and central Siskiyou County
on Tuesday and Wednesday afternoons with north winds of 10 to 15 mph
and gusts to 25 mph. Winds will be strongest in the Shasta Valley
near Montague. Similarly, northeast winds also be near critical
thresholds in the Illinois Valley on Wednesday afternoon at 10 mph
with gusts to 20 mph, with minimum humidities of 10-15%.  In
general, the time and area spent near critical thresholds during the
next week looks to be much greater than the instances of reaching
them. But, the extreme heat, and long duration of the heat will
allow even typically breezy afternoon conditions to result in
dangerous weather, favorable for rapid spread of fire.

-DW

&&

.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.

&&

$$