865
FXUS66 KMFR 291119
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
419 AM PDT Sat Jun 29 2024

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

DISCUSSION (Today through Friday)...

Overview:

Overall, the forecast is still calling for potential impacts from
both heat and fire weather. 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 both today and tomorrow afternoon 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
this weekend. There is a chance for thunderstorms both today and
tomorrow afternoon. However, the problem both days are weak
variables, and these variables not entirely phasing together
correctly, especially the moisture aspect. The vorticity field might
phase with 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. Chances are slightly
better tomorrow as we might have an upper level jet streak helping
with additional forcing. CAPE is relatively weaker on Saturday, and
really only showing up in the NAM (typical with the wet bias), but
Sunday we have a few different models suggesting a couple to perhaps
a few hundred J/kg of MUCAPE. Again, not expecting severe weather,
but lightning may disrupt outdoor activities this weekend on the
eastside.

The heat is coming! The probabilities for 100 degrees or more have
gone up for some of the westside valleys with some areas sitting
around a 50-70 percent chance for 100 degrees or more. In fact, the
probability for 110 or greater is around 20% 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. 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: 94)
Brookings:      96  in 1931 (Forecast: 74)
Klamath Falls:  98  in 1981 (Forecast: 94)

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

Medford:       102  in 1926 (Forecast: 104)
Roseburg:       98  in 2023 (Forecast: 99)
Brookings:      84  in 1993 (Forecast: 73)
Klamath Falls:  98  in 2007 (Forecast: 96)

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. This doesn`t bode well for our
fire weather conditions as a prolong drying period appears slated
for much of the area.

-Guerrero

AVIATION 29/12Z TAFS...High clouds are blocking visual verification
that stratus is expanding inland towards the Umpqua Basin, but this
is still expected this morning. This stratus will continue to cause
IFR impacts along the coast and MVFR conditions across Douglas
County and at Roseburg. The remainder of the area will maintain VFR
conditions through the day today, although some mid-level clouds
will move into 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.
-Miles

MARINE...Updated 145 AM Saturday, June 29, 2024...Winds and seas
will lower this afternoon into Sunday for most of the area. 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. These conditions will
likely be too short lived and localized to warrant needing an
advisory, but you`ll want to watch Buoy 27 to monitor conditions in
this area to be safe before heading out.

Then, a very strong thermal trough is expected to develop next week
beginning on Monday and lingering towards the end of the week. 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 chance for gale force
wind gusts south of Cape Blanco is 80% or greater (90% plus south of
Pistol River) and this will drive very steep waves. There is also a
moderate (20-50%) chance that gale force winds develop over the
waters north of Cape Blanco and south of Cape Arago. Confidence is
low if these gusts will be frequent enough to warrant any sort of
Warning north of Cape Blanco, however. Comparing this event to the
past, this is getting into the top end of events, and to summarize,
this occurrence of the thermal trough northerlies will not be one to
mess with.

-Miles

&&

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

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT early
     this morning for PZZ356-376.

&&

$$