274
FXUS66 KMFR 130345
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
845 PM PDT Fri Jul 12 2024

.DISCUSSION...Satellite imagery is showing some coastal stratus in
Coos County and offshore with clear skies elsewhere. Well to the
East and the South of southern Oregon and northern California
cloud cover associated with monsoon moisture is visible, and this
will be one of the main concerns over this weekend as it pushes
our way. As the ridge slowly breaks down, area observations remain
breezy with very low humidity values being recorded for a lot of
inland locations. While the red flag warning was allowed to expire
for this evening, another red flag is in effect for the eastside
on Saturday and a fire weather watch on Sunday.

In other news, temperatures were also hot once again today, with
the Medford Airport reaching 100 degrees. Tomorrow will be hot as
well, so will continue the Excessive Heat Warning for Siskiyou
County and the heat advisory for Jackson, Josephine and most areas
east of the Cascades.

In all, this forecast is going to be relatively dynamic. For more
information, including on the thoughts on thunderstorms, please
read the previous discussion below. -Schaaf

&&

.PREV DISCUSSION... /Issued 457 PM PDT Fri Jul 12 2024/

DISCUSSION...High pressure remains in place over the region with
an upper level four corners high the dominant weather feature
through at least mid next week. Temperatures continue to be
generally 10 or so degrees above normal for the middle of July.
Breezy northwest winds are expected west of the Cascades...while
stronger southwest winds are impacting areas east of the Cascades.
We are currently seeing wind gusts near 30 mph...with the short
term high res models indicating wind gusts nearing 35 kts across
the southern half of Klamath and Lake counties through this
evening. These breezy and hot conditions are continuing to lead to
fire weather concerns. Please see below for more information
regarding a red flag warning. Otherwise...a heat advisory and an
excessive heat warnings remain in effect through Saturday evening.
Please see our webpage at weather.gov/medford for more detailed
information regarding the heat.

Otherwise...our main area of concern will be the potential for
thunderstorms over the weekend. Mid level monsoonal moisture is
slated to move into the southeastern portion of the forecast
area...with the best chance (around 20% chance) for thunderstorms
over southeastern Modoc county. A slight chance (10% to 15%
chance) of thunderstorms will be present across the eastern half
of Siskiyou county through far southern Klamath county and the
southern half of Lake county. Thunderstorm coverage will expand
Sunday afternoon into the evening hours as the monsoonal moisture
stretches a bit more north and west through much of
Siskiyou...Klamath...and Lake counties. The chance for
thunderstorms on Sunday is generally 15% to 25%. Please see below
for a very detailed and well written fire discussion regarding
this weekend.

We are not expected to experience any major changes in the upper
level pattern through much of next week. Our challenge will be
subtle differences in the location of the upper ridge and a
general trough pattern over the Gulf of Alaska. Please continue to
monitor the forecast closely as fine detail will be added in daily
to especially the 24 to 48 hour forecast.

-Riley

FIRE WEATHER...Issued 200 PM Friday July 12, 2024...

..Near critical fire weather conditions possible through at least
this weekend...

..RED FLAG WARNING REMAINS IN EFFECT UNTIL 8 PM PDT THIS EVENING
FOR STRONG GUSTY WIND AND LOW RH FOR FIRE WEATHER ZONES
624...625...284...285...

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

..RED FLAG WARNING IN EFFECT FROM 2 PM TO 8 PM PDT SATURDAY FOR
ABUNDANT 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...

Hot, breezy, low humidities, and unstable afternoon conditions will
persist through this weekend. For today, a weak upper level wave
will bring some strong gusty winds to the area this afternoon and
evening, especially east of the Cascades. Daytime humidities will
continue to be in the low teens and single digits, and with the
stronger winds expected today, this will result in critical fire
weather conditions for portions of Fire Weather Zones (FWZ) 624,
625, 284 and 285. Breezy west to northwest winds are expected west
of the Cascades with a potential for brief or local critical
conditions, especially in portions of central and western Siskiyou
County.

After today, the focus turns to the potential for thunderstorms
Saturday and Sunday, and potentially into early next week. 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 Saturday, we expect isolated
thunderstorms to be focused over our southeastern zones (284, 285,
southern 624 and 625). We upgraded the Fire Weather Watch to a Red
Flag Warning (RFW) for these zones for abundant lightning on dry
fuels. It should be noted that the RFW for FWZs 624 and 625 is
actually a combination of critical concerns. Gusty southwest winds
will shift northward on Saturday and humidities will remain a 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 on Saturday will be high based
and have very little to no precipitation with them.

As we head into 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 moisture field shifts westward. Have left
the Fire Weather Watch in place for FWZ 624, 625, 284 and 285, but
have also included FWZ 280, to include 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.

The focus of today`s efforts has largely been on the weekend setup,
but it`s possible we see isolated thunderstorm chances continue into
Monday or even 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`ll have to monitor model trends closely as each day
passes, but we`ll be in a thunderstorm pattern Saturday through at
least Monday, and subtle shifts in model trends could lead to big
changes in the forecast. /BR-y

AVIATION...13/00Z TAFS...Marine stratus along the coast north
of Cape Blanco will edge inland this evening with IFR/LIFR at North
Bend. North winds with gusts of 30-35 kt will ease overnight. Expect
stratus to push back to the beaches or just offshore again Saturday
morning (16-17Z) with VFR returning to North Bend. Gusty north winds
develop again in the afternoon, with gusts of 25-30kt. Another area
of LIFR is expected tonight into Saturday morning near Brookings.

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. -Spilde

MARINE...Updated 200 PM Thursday, July 11, 2024...Moderate to
strong winds will continue, with the strongest winds 10 to 20 nm
away from shore from Gold Beach. Steep wind driven seas up to 14
feet will persist in roughly the same area and locations farther
south. Winds will ease some Saturday into Sunday, but gales will
remain over the southern waters due to the expansion fan southwest
from Port Orford, therefore the Gale Warning has been extended, but
the coverage area will be small than it is currently.

Moderate north winds will continue into Monday with small Craft
conditions likely for the southern waters, then winds and seas will
diminish Tuesday through Wednesday with calmer conditions.
-Petrucelli

&&

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

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

     Red Flag Warning from 2 PM to 8 PM PDT Saturday for ORZ624-625.

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

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

     Heat Advisory until 9 PM PDT Saturday for CAZ083>085.

     Red Flag Warning from 2 PM to 8 PM PDT Saturday 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.

&&

$$