913
FXUS66 KMFR 301115
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
415 AM PDT Sun Jun 30 2024

.UPDATE...Updated aviation discussion for 12z TAFs.

&&

DISCUSSION (Today through Saturday)...

Overview:

Potential impacts from both heat and fire weather are at the
forefront of the forecast for the next week, but early indications
suggest we could be in for a rather dry and hot first half of July.
By middle of next 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
as well. Unfortunately, with the heat comes low RH values that could
be coupled with breezy winds, so there is at least some risk for
elevated to perhaps critical fire weather conditions next week.
Lastly, there will be a small chance for thunderstorms today for
mainly areas on the eastside. Not expecting severe weather, but the
threat for lightning will exist.

Further Details:

Pieces of energy are expected to round the base of a passing trough
today. This may result in a chance for thunderstorms today, but the
problem is we have weak variables, especially the moisture aspect.
There is some indication the vorticity field might phase with some
limited moisture today, and this could kick off some
showers/thunderstorms over parts of Klamath and Lake counties. Not a
great chance, but also not a zero chance. Models are suggesting
upwards around a few hundred J/kg of MUCAPE could be present today.
Again, not expecting severe weather, but lightning may disrupt
outdoor activities this afternoon and early evening on the eastside.

The heat is coming! The probabilities for 100 degrees or more have
gone up (again) for some of the westside valleys with some areas
sitting around a 70-80 percent chance for 100 degrees or more on the
holiday (July 4th). In fact, by July 5th the probability for 110
or greater is around 30% for both the Rogue Valley and Shasta
Valley. In other words, there is a high probability for some sort
of heat related headline come next week to account for this threat
as the Rogue Valley could go about 7 days or more with 95+
degrees starting Wednesday. Overnight low temperatures might be
in the mid 60s for some areas on the westside Fri-Sun, which would
not allow for much relief from the heat overnight.

Some Potential Records:

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

Medford:       103  in 2015 (Forecast: 101)
Roseburg:       98  in 2023 (Forecast: 95)
Brookings:      96  in 1931 (Forecast: 78)
Klamath Falls:  98  in 1981 (Forecast: 94)
Mount Shasta:   97  in 2007 (Forecast: 99)

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

Medford:       102  in 1926 (Forecast: 103)
Roseburg:       98  in 2023 (Forecast: 98)
Brookings:      84  in 1993 (Forecast: 77)
Klamath Falls:  98  in 2007 (Forecast: 96)
Mount Shasta:  100  in 2007 (Forecast: 100)

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

Medford:       104  in 1922 (Forecast: 105)
Roseburg:      102  in 1960 (Forecast: 100)
Brookings:      84  in 1998 (Forecast: 74)
Klamath Falls:  96  in 2021 (Forecast: 97)
Mount Shasta:   99  in 2007 (Forecast: 101)

Unfortunately, the heat (above normal temperatures) may continue
into parts of mid July as the Climate Prediction Center is
forecasting the chance for above normal temperatures to continue
with below normal precipitation chances. This 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... 30/12Z TAFS...Low clouds and fog will will impact
areas along the coast this morning, clearing to VFR in the
afternoon. Low clouds with IFR and MVFR are likely to return to
the coast Sunday evening. Inland, areas of MVFR are expected to
spread into the Umpqua Basin to Roseburg early this morning. These
clouds will clear in the late morning to VFR. 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 low chance for an
isolated thunderstorm east of the Cascades this afternoon.
-Miles

MARINE...Updated 200 AM Sunday, June 30, 2024...Winds and seas
will remain low today. However, areas from Brookings south within
about 15 NM of shore could observe brief and isolated advisory level
seas as winds peak in the afternoon, generating a steep wind wave.
If in this area, watch Buoy 27 to monitor conditions to be safe
before heading out.

A very strong thermal trough is expected to develop next week
beginning Monday afternoon and lingering towards the end of the
week. A Gale Watch and other headlines have been put in place for
this event this morning. The peak should be either Tuesday or
Wednesday evening, and the guidance is trending towards 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 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 Watch was put in place instead of something for the
infrequent gale force gusts. Comparing this event to the past, this
is getting into the top end of events, standing out against
climatology. And to summarize, this occurrence of the thermal trough
northerlies will not be one to mess with.

-Miles

FIRE WEATHER (Updated 300 AM Sunday, June 30th)...

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

As mentioned above in the discussion, we have a small chance for
thunderstorms today mainly on the eastside. Not expecting widespread
thunder or severe weather, but isolated strikes could occur late
this afternoon and early evening.

A strong warming and drying trend will begin Monday night as high
pressure builds into the region. This will bring moderate to locally
poor humidity recoveries to ridges. 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 have at least elevated
concerns through the weekend. Additionally, 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, while the hot and dry aspect
looks like a "slam dunk" to occur.

-Guerrero

&&

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

PACIFIC COASTAL WATERS...Gale Watch from Monday afternoon through
     late Wednesday night for PZZ356-376.

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

     Hazardous Seas Watch from Monday afternoon through late
     Wednesday night for PZZ370.

&&

$$