643
FXUS66 KMFR 011027
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
327 AM PDT Mon Jul 1 2024

.DISCUSSION (Today through Sunday)...

Overview:

Impacts from both heat and fire weather remain at the forefront of
the forecast for at least the next week, but early indications
suggest we could be in for a rather dry and hot first half of July.
By middle of the week, the heat will be ramping up across the
forecast area, and there is a high likelihood for some sort of heat
risk. In fact, there is the potential for some records to be broken,
but not the kind of records some people hope for this time of year.
Unfortunately, with this heat comes low RH values that could be
coupled with breezy winds, so there is at least some risk for
elevated to critical fire weather conditions nearly every day
this week.

Further Details:

With the passing trough to our east that brought a dozen or so
lightning strikes (cloud to ground), a dome of high pressure to
the west will start to slide east today over the Pacific Ocean.
Models are progged to bring the center of this H5 high pressure
closer and closer to the western CONUS each day. This will start
ramping up our temperatures each day and our fire weather chances
through this week. Please see the fire weather discussion below
for more information on those specific fire weather hazards.

By Thursday, the aforementioned area of high pressure will be off
the coast (37N and 127W) of California, yet we will see
temperatures soaring to about 100 degrees for many locations
starting Fourth of July. The high meanders off the coast for
several days until it finally comes on shore Friday night. This is
going to result in several days with triple digits in the
forecast. Saturday is likely the warmest day by areal coverage and
overall high temperatures. The probabilities for 100 degrees or
more have gone up (again) for many westside locations. Areas in
the valleys on the westside have about a 80-90% chance for 100
degrees or more Thursday through Sunday. In fact, July 5th and
6th, the probability for 110 or greater is around 30-50% for both
the Rogue Valley and Shasta Valley and other areas of western
Siskiyou county. In other words, there is a high probability for
some sort of heat related hazard this week, and this is especially
concerning for those more susceptible to heat. Also of note is
the duration of this heat wave. The Rogue Valley could go about 9
days or more with 95+ degrees starting Wednesday, but 8 of those
days could possibly be 100+ degrees. Overnight low temperatures
might be in the mid 60s for some areas on the westside Fri-Sun,
which would not allow for much overnight relief from the heat.
This is all adding up to a very notable heat wave. The record for
100+ degree days in a row is 10 for Medford, and there are
indication we could go about 8 days in Medford starting the Fourth
of July. Maybe longer? Model data gets sparse and iffy that far
out, but it is something certainly worth mentioning at this point
because we could break the record for total 100 degree days in
July. Medford`s record for total number of 100 degree days (not
necessarily in a row) in July is 13 days set back in 2014. This
might not be the record some folks were hoping for this summer.

Potential Records:

--------
July 4th
--------

Medford:       103  in 2015 (Forecast: 102)
Roseburg:       98  in 2023 (Forecast: 95)
Brookings:      96  in 1931 (Forecast: 80)
Klamath Falls:  98  in 1981 (Forecast: 94)
Mount Shasta:   97  in 2007 (Forecast: 99)

--------
July 5th
--------

Medford:       102  in 1926 (Forecast: 106)
Roseburg:       98  in 2023 (Forecast: 101)
Brookings:      84  in 1993 (Forecast: 81)
Klamath Falls:  98  in 2007 (Forecast: 97)
Mount Shasta:  100  in 2007 (Forecast: 102)

--------
July 6th
--------

Medford:       104  in 1922 (Forecast: 107)
Roseburg:      102  in 1960 (Forecast: 103)
Brookings:      84  in 1998 (Forecast: 77)
Klamath Falls:  96  in 2021 (Forecast: 99)
Mount Shasta:   99  in 2007 (Forecast: 103)

--------
July 7th
--------

Medford:       102  in 2014 (Forecast: 105)
Roseburg:      100  in 2010 (Forecast: 99)
Brookings:      94  in 1937 (Forecast: 72)
Klamath Falls:  97  in 2014 (Forecast: 97)
Mount Shasta:  101  in 2014 (Forecast: 101)

Unfortunately, this potential record heat wave with above normal
temperatures will likely continue through mid July. The Climate
Prediction Center is forecasting a moderate/high chance for both
above normal temperatures and below normal precipitation through mid
month. This also doesn`t bode well for our fire weather conditions
as a prolong drying period appears slated for much of the area
through at least mid July.

-Guerrero

&&

.AVIATION (06Z TAFs)...

Low clouds with IFR and LIFR will spread into the coast tonight
and persist till late Sunday morning, then clear to VFR. This will
mainly affect areas from Cape Blanco northward and near
Brookings. Areas of IFR/LIFR in low clouds are likely again Monday
evening along the coast, mainly Cape Blanco northward. Elsewhere,
expect VFR across the area. Smoke from a few wildfires could
produce some locally low visibility near those fires, otherwise
the smoke will not be an issue near terminals. There is a 15
percent chance for an isolated thunderstorm east of the Cascades
this afternoon.

-CC

&&

.MARINE (Updated 100 AM July 1st)...

A very strong thermal trough is expected to develop today and
linger 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.

-Miles

&&

.FIRE WEATHER (Updated 300 AM July 1st)...

...Elevated to critical fire weather possible Tuesday through the
weekend...

A very strong combination of warming and drying will begin tonight
as high pressure starts to build in over the Pacific towards the
western CONUS. This will bring moderate to locally poor humidity
recoveries to ridges overnight for some westside areas. The poorest
recoveries and hottest temperatures are expected from Wednesday
morning into the weekend. Western Siskiyou County in particular
could experience critical fire weather conditions starting as early
as Tuesday afternoon, but much of the forecast area will
experience elevated to critical fire weather concerns through the
weekend. There is concern for both critically poor night-time
ridge top humidity recoveries (higher terrain of Curry and western
Josephine counties), and also gusty afternoon winds accompanying
a very dry airmass. The limiting factor is likely to be wind
speeds overnight, while the hot and dry aspect looks like a "slam
dunk" to occur both day and night. We held off tonight on
watches/warnings in hopes to gather further insight into where and
when we might see specific fire weather hazards. It may end up
being a combination of diurnally driven impacts and overnight
impacts from poor recoveries and breezy winds. That said, look for
some clarity later today after we can talk to our partners about
the best approach through this notable heat wave.

-Guerrero

&&

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

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

PACIFIC COASTAL WATERS...Gale Warning from noon today to 5 AM PDT
     Thursday for PZZ356-376.

     Small Craft Advisory from 5 PM this afternoon to 5 AM PDT
     Thursday for PZZ350-370.

     Hazardous Seas Warning from 5 PM this afternoon to 5 AM PDT
     Thursday for PZZ370.

&&

$$