156
FXUS66 KMFR 131237
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
535 AM PDT Sat Jul 13 2024

Updated Aviation Discussion.

.DISCUSSION...

Chalk up another warmer than normal day for southern Oregon and
northern California for this July. Today will be a bit warmer with
highs pushing a bit above 100 and testing records in the Shasta
Valley. Right now, we`re forecasting 102 degrees in Mt. Shasta
City, which would break the old record of 99 set in 2021. The NWS
HeatRisk algorithm does pick up on some major heat risk in a few
of the southern valleys today, so heat illness is a risk for those
that don`t adequately hydrate or find adequate cooling
facilities. As for the heat hazards, our heat advisory and
excessive heat warnings go on through this evening, and that will
likely be the end of this heat wave. Although, it`s worth
mentioning that the above normal temperatures continue into the
end of next week.

Shifting to air quality and smoke, fires will likely burn
actively with the plumes heading towards the north east. However,
the low level flow(0-1km) remains out of the west to northwest.
The result is the Scott and Shasta Valleys still seeing plenty of
smoke from the Shelly Fire as that fire keeps burning with some
intensity. The Klamath Basin should also see some smoke as it
mixes down from higher elevations in the afternoon and evening.

As for thunderstorms, some moisture will push in from California
today. There is a very low risk of cloud to ground lightning
around Modoc and southern Lake and Klamath Counties. The High
resolution ensemble forecast system shows a few 40 dbz echos
sliding through the area this afternoon. With such high bases,
these storms will likely be dry.The upper level wave bringing in
this moisture will push a little farther north Saturday night into
Sunday. It`s really hard to see storms persisting overnight,
although it`s not out of the question.

By Sunday, the amount of moisture increasing in the region is more
notable as the upper level wave moves up the California coast.
The confidence in storms is higher as the probability of thunder
from the NBM also increases. In addition, the coverage of storms
should be higher compared to Saturday.

Jumping into next week, the four corners high will remain in place
with some warmer than normal temperatures continuing. It`s not
excessively hot, just warmer than normal. Thunderstorms will
probably remain in the forecast on Monday or Tuesday as the upper
level wave moves through our region around that time.

-Smith

&&

.FIRE WEATHER...Issued 330 AM Saturday July 13, 2024...

...RED FLAG WARNING IN EFFECT FROM 2 PM TO 8 PM PDT TODAY FOR
STRONG GUSTY WIND AND LOW RH AND LIGHTNING ON DRY FUELS FOR FIRE
WEATHER ZONES 624 AND 625...

...RED FLAG WARNING IN EFFECT FROM 2 PM TO 8 PM PDT TODAY FOR
LIGHTNING ON DRY FUELS FOR FIRE WEATHER ZONES 284 AND 285...

...FIRE WEATHER WATCH NOW IN EFFECT FROM SUNDAY MORNING THROUGH
SUNDAY EVENING FOR ABUNDANT LIGHTNING ON DRY FUELS FOR FIRE WEATHER
ZONES 280...284...285...624 AND 625...

...Complex fire weather environment evolves this weekend...

Hot, breezy, low humidities, and unstable afternoon conditions will
persist this afternoon across the region, but especially east of
the Cascades. Mixed with a little bit of wind, the fire weather
risk will hit critical conditions east of the Cascades today. This
is shown in the Hot Dry Windy Index with values exceeding
climatological norms for this time of year around Chemult and Fort
Rock. The good news here is that winds are not exceptionally
strong with sustained winds around 20 mph with gusts to 35 mph in
northern Klamath and Lake counties. However, humidities are
anticipated to drop into the single digits, which is lower than
what we usually see in this area during the summer.

On the other hand, there is some moisture arriving from the south
today and this can be seen by the cloud cover over sections of
California and Nevada. There is a low threat for some cloud to
ground lightning. We wouldn`t consider this abundant lightning on
the other hand. However, if cloud to ground lightning does occur, it
has a high probability of being dry given the very dry boundary
layer and lack of moisture in the mid layers. In addition, models
are showing storm outflows in the wind fields, which suggests the
storms are drier than what we usually see in our region. The
argument against storm development this afternoon is the forcing
to get storms going in addition to the high level of free
convection of ~13000 feet.

As we head into Sunday, the potential for thunderstorms shifts north
and westward. It`s not out of the question we see some isolated,
elevated convection continue Saturday night into Sunday morning, but
Sunday afternoon and evening looks like the day for the most
coverage of storms as the moisture field shifts north and westward.
Have left the Fire Weather Watch in place for FWZ 624, 625, 284, 285
and FWZ 280, which also includes the Shelly Fire. For now,
confidence is higher for the zones covered by a watch, but it`s not
out of the question for an isolated storm along the Cascades or
Siskiyous. Once this timeframe is covered by the high resolution
models, will make further decisions on upgrading or adding more
zones. Storms should trend wetter on Sunday, but still be a mix of
dry and wet storms, with lightning strikes outside of precipitation
cores a real possibility and cause for concern.

/BR-y/Smith

&&

.AVIATION...13/12Z TAFS...Marine stratus will impact the coast north
of Cape Blanco (including at North Bend) and near Brookings this
morning with IFR and LIFR conditions. Expect the stratus to push back
to the beaches or just offshore again later this morning (16-18Z) with
VFR returning to North Bend. Gusty north winds develop again in the
afternoon, with gusts of 25-30kt. IFR and LIFR will return again to
the coast by early this evening.

Inland, VFR conditions will continue through the TAF period, except
for MVFR visibility between 4-5 miles in the vicinity of the Shelly
Fire. Visibility could briefly lower to 5 miles near the Salt Creek
Fire, but the prevailing visibility should remain 6 miles or
greater.

Mid and upper level moisture will move into southern and eastern
sections of the area Saturday which could initiate convection during
the afternoon and evening in portions of Siskiyou, Modoc,
southeastern Klamath and southern Lake counties. Isolated t-storms
could produce lightning and gusty outflows. -Spilde/CC

&&

.MARINE...Updated 200 AM Saturday, July 13, 2024...Moderate to
strong winds will continue, with the strongest winds beyond 5 nm
from near Port Orford southward. Very steep wind driven seas up to
13 feet will persist in roughly the same area. Winds will ease some
Saturday night into Sunday, but very steep seas and areas of gales
will remain over the southern. For the waters from Cape Blanco
north, gusty winds and steep seas are expected through Sunday. Winds
and seas will lower some Sunday night in Monday but expect continued
gusty north winds and steep seas across much of the waters. Then
winds and seas are expected to gradually diminish Tuesday through
Wednesday with calmer conditions. -CC

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Fire Weather Watch from Sunday morning through Sunday evening
     for ORZ624-625.

     Heat Advisory until 9 PM PDT this evening for ORZ024-026-
     029>031.

     Red Flag Warning from 2 PM this afternoon to 8 PM PDT this
     evening for ORZ624-625.

CA...Excessive Heat Warning until 9 PM PDT this evening for
     CAZ080>082.

     Fire Weather Watch from Sunday morning through Sunday evening
     for CAZ280-284-285.

     Heat Advisory until 9 PM PDT this evening for CAZ083>085.

     Red Flag Warning from 2 PM this afternoon to 8 PM PDT this
     evening for CAZ284-285.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 PM PDT Sunday
     for PZZ350-356-370-376.

     Gale Warning until 5 PM PDT Sunday for PZZ356-376.

&&

$$