674
FXUS66 KMFR 140405
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
905 PM PDT Sat Jul 13 2024

.DISCUSSION...Satellite imagery is showing clouds across much of
the East Side and in northern California as well. Radar is
confirming some showers across portions of the East Side with a
few lightning strikes. Also of note is the Shelley Fire is very
visible via satellite and RADAR, particularly in the aloft slices
of the RADAR imagery. This suggests that the unstable nature of
the Atmosphere that is causing the showers and thunderstorm
chances has caught the Shelley fire and allowing for some extreme
plume-dominated growth. This is confirmed by the incident
meteorologists on the fire who we are working with in order to
keep firefighters abreast of the weather in order to keep them
safe.

In other news, temperatures will not be as hot tomorrow; albeit
still a few degrees above normal. Therefore we allowed the
Excessive Heat Warning and Heat Advisory to expire at 9pm. A red
flag warning for lightning on dry vegetation will continue
overnight into tomorrow through 11pm as this unstable airmass will
allow for dry thunderstorms to be possible overnight. Tomorrow
still seems on track to be our big thunderstorm day; so will
continue to monitor the forecast. For more information about the
forecast, please read the previous discussion below. -Schaaf

&&

.MARINE...Updated 830 PM Saturday, July 13, 2024...We have
cancelled the gale warning. Observations are showing weaker winds
compared to yesterday at this time and we expect further weakening
of the thermal trough tonight through Monday. Even so, conditions
will remain hazardous due to a continuation of moderate north winds
and steep to very steep seas, dominated by wind waves. We have
issued a hazardous seas warning to account for the very steep wind
seas from around Gold Beach southward and beyond about 10 NM from
shore (southern half of PZZ376). Models are showing a slight
coastward push to around 8 NM for seas near 10 feet between Gold
Beach and Port Orford Sunday afternoon, but it`s a small area and
not representative of the entire zone. Even so, a small craft
advisory remains in effect for the southern inner zone (PZZ356) for
gusty north winds and steep seas. The same is true for areas north
of Cape Blanco, where north winds and seas will produce conditions
hazardous to small craft. Eventually, though, winds and seas are
expected to gradually subside Tuesday into Thursday. -Spilde


&&

.PREV DISCUSSION... /Issued 545 PM PDT Sat Jul 13 2024/

DISCUSSION...Satellite is creating a beautiful picture with the
stratus banking the coast. Some stratus was reaching into the
Coquille Basin this morning, but that has been burning off, albeit
stubbornly. Inland, cumulus is starting to creep up into Modoc,
Lake and Siskiyou counties. The Shelly Fire is the main smoke
producer in the area today, with most of the smoke staying in
Siskiyou County with haze across more areas in Southern Oregon and
Modoc County.

Highs this afternoon will be in the 90s or low 100s widespread
besides the coast. It will also be the last day in the forecast for
record watching. The record high for Alturas is 102 from 2014 with a
forecast of 101 and Mount Shasta has a record of 99 from 2021 with a
forecast of 103. This afternoon is also the last afternoon where a
Heat Advisory will be in effect for Jackson and Josephine counties
with an Excessive Heat Warning for most of Siskiyou County. Overall,
temperatures will be near 5-10 degrees above normal the next few
days, which will mean temperatures will still range from 50s and 60s
in the mornings to 90s/low 100s in the afternoons inland. The trend
of warmer than normal conditions will continue through the rest of
the week. Please still take precautions when having to be out in the
heat this next week.

The main smoke concerns lie in Siskiyou County with the Shelly Fire
while haze is present in other parts of Southern ORegon and Northern
California. Into tomorrow morning the smoke will come across
southerly flow which will move lower concentrations to Jackson,
Klamath and Lake counties.

The cumulus that is building is indicating that there is more
moisture in the air. This afternoon there is a 15-20% chance for
lightning from central Siskiyou County east into Modoc County and in
portions of southern Klamath and Lake counties. A 5-15% chance for
lightning continues tonight that includes Callahan, Lakeview and
Alturas. Tomorrow is looking more favorable for lightning with a 15-
30% chance with a line from western Siskiyou County and up into
eastern Jackson County and Crescent that continues eastward.

Dry conditions are favored to return Wednesday. From Thursday
through the weekend, the probability for reaching 100 degrees in
Medford lowers to 25-45% while highs and lows are forecast to be 5-
10 degrees above normal. -Hermansen

AVIATION...14/00Z TAFS...VFR prevails over most of the CWA, but
marine stratus (IFR/LIFR) has already moved into North Bend and will
remain there (and along the rest of the coast north of Cape Blanco)
the remainder of the night through about 17-18Z on Sunday. Fog/low
clouds will also return to Brookings overnight into Sunday morning.
Gusty north winds (up to 25kt) in North Bend will ease this evening,
but develop again as conditions break to VFR Sunday
morning/afternoon. Expect stratus/fog to return to the same coastal
areas again Sunday evening.

Meanwhile, isolated thunderstorms are developing in NE California
and pushing into south-central Oregon this evening. These storms are
very high-based, so little or no precipitation is reaching the
ground. However, gusty outflows (40-45kt) are possible along with
cloud to ground lightning. These are primarily in Siskiyou and Modoc
counties, but also portions of southeastern Klamath and southern
Lake counties. Coverage of storms should diminish tonight, though
may not go away completely. Expect another round of isolated to
scattered storms Sunday afternoon/evening with a larger coverage
area from western Siskiyou County northward up to the Siskiyou Mtns,
southern Cascades (south of Crater Lake) and then over to the east
side again.

Smoke from the Shelly fire in western Siskiyou County could bring
visibility reductions in the immediate vicinity of the fire with
MVFR visibility 15-25 miles away, especially to the NE (toward
Montague) as SW winds carry the main plume in that direction.
-Spilde


FIRE WEATHER...

...RED FLAG WARNING IN EFFECT UNTIL 8 PM THIS
EVENING FOR STRONG GUSTY WIND AND LOW RH FOR NORTHERN FIRE
WEATHER ZONES 624 AND 625...

..RED FLAG WARNING IN EFFECT UNTIL 11 PM PDT SUNDAY FOR LIGHTNING
ON DRY FUELS FOR FIRE WEATHER ZONES 284...285..624 AND 625...

..RED FLAG WARNING IN EFFECT FROM 2 AM TO 11 PM PDT SUNDAY FOR
LIGHTNING ON DRY FUELS FOR FIRE WEATHER ZONES 280...281...282... AND
621...

..FIRE WEATHER WATCH IN EFFECT FROM SUNDAY EVENING THROUGH MONDAY
EVENING FOR LIGHTNING ON DRY FUELS FOR FIRE WEATHER ZONES
280...281...282...284...285...624 AND 625...

Hot, breezy, low humidities, and unstable afternoon conditions will
persist through this weekend. The focus of today`s efforts was to
fine tune the thunderstorm forecast for this weekend and to glean
any details for the Monday/Tuesday timeframe as well. Strong high
pressure will linger over the Great Basin region into next week and
a weak low pressure will move northward just offshore of the
California coast. This is a pretty classic thunderstorm pattern for
this area as the flow turns more southerly and moist unstable air
moves into the region.

For today, we expect isolated thunderstorms to be focused over our
southeastern zones (284, 285, southern 624 and 625) and this is
covered by the current Red Flag Warning (RFW). Storms are already
moving into Modoc County this afternoon, so the forecast remains on
track for today. Meanwhile, the RFW for FWZs 624 and 625 is actually
a combination of critical concerns. Gusty southwest winds have
shifted northward today and humidities will remain very low across
the northern portions of those zones. So north of a line from
roughly Chiloquin to Paisley, we expect critical fire weather
conditions due to gusty winds and low RH, while south of there the
concern is due to lightning on dry fuels. Though confidence is
higher for isolated coverage vs scattered, any lightning in the area
right now should be highly efficient fire starters thanks to the
recent prolonged stretch of very hot and very dry conditions.
Additionally, any storms that develop today into tonight will be
high based and have very little to no precipitation with them.

As we head into tonight and Sunday, the potential for thunderstorms
shifts 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 mid-level moisture field shifts westward.
Have upgraded the Fire Weather Watch for FWZ 624, 625, 284, 285, 280
to a Red Flag Warning and have also added FWZs 281, 282 and 621 to
the warning. Additionally, to cover the potential for isolated dry
thunderstorms for the overnight period, have basically just
stretched out the current Red Flag Warning to continue overnight
tonight through late Sunday evening. The exception being FWZs
280/281/282/621 where that Red Flag starts at 2 am tonight and
carries through late Sunday evening. Storms should trend wetter on
Sunday, but will still be a mix of dry and wet storms, with
lightning strikes outside of precipitation cores a real possibility
and cause for concern.

The focus of today`s efforts has largely been on the weekend setup,
but it looks like we`ll maintain at least isolated thunderstorm
chances Monday into Tuesday. There is some uncertainty due to model
differences regarding where these chances are focused, which could
include west of the Cascades or even nocturnal thunderstorms at some
point. We`ve gone ahead and issued a Fire Weather Watch for late
Sunday night through Monday evening where confidence is highest for
the continued thunderstorm threat, and this includes FWZs
280/281/282/284/285/624/625.

We`ll have to monitor model trends closely as each day
passes, but we`ll be in a thunderstorm pattern through Tuesday, and
subtle shifts in model trends could lead to big changes in the
forecast. /BR-y

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 2 AM to 11 PM PDT Sunday for ORZ621.

     Red Flag Warning until 11 PM PDT Sunday for ORZ624-625.

     Fire Weather Watch from Sunday evening through Monday evening
     for ORZ624-625.

CA...Red Flag Warning from 2 AM to 11 PM PDT Sunday for CAZ280>282.

     Fire Weather Watch from Sunday evening through Monday evening
     for CAZ280>282.

     Red Flag Warning until 11 PM PDT Sunday for CAZ284-285.

     Fire Weather Watch from Sunday evening through Monday evening
     for CAZ284-285.

PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT Monday
     for PZZ356-370-376.

     Small Craft Advisory until 8 PM PDT Sunday for PZZ350.

     Hazardous Seas Warning until 8 PM PDT Sunday for PZZ376.

&&

$$