219
FXUS66 KMFR 052323
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
423 PM PDT Sat Jul 5 2025

...Updated AVIATION discussion for 00Z TAFs...

.SYNOPSIS...

An upper level low will bring a chance for thunderstorms across
our forecast area between Monday and Wednesday. Temperatures will
then trend warmer towards the end of the week.

.DISCUSSION...

Plenty of cumulus buildup east of the Cascades and along the
Cascades this afternoon as there is still some lingering moisture
and weak synoptic lift across the region. The weather will remain
fairly quiet tonight as some cooler temperatures in the mid 50`s
settle into most locations overnight.

By Sunday, A cutoff low will settle right along the central
California coastline by mid day. Temperatures trend a bit warmer
with highs in the mid 90`s here in Medford. Brookings should be on
the warmer side as well with 10 to 15 knot north east winds over
the southern Coastal range. That will result in highs between the
mid 70`s to perhaps mid 80`s over spots in Curry County. We should
see more cumulus buildup during the day, although we`re not
expecting any thunderstorms at this time.

This will change by Monday as a small chunk(~30%) of ECMWF ENS
members are predicting some precipitation, which should come in
the form of thunderstorms given the pattern and surface
temperatures anticipated Monday. The NAMnest and NAM soundings
show about 400 j/kg of convective available potential
energy(CAPE) with little convective inhibition(CIN). Some of these
storms could be elevated and again hedge towards the dry side.
Storms are anticipated to be isolated.

The upper level low nudges just a bit farther north giving us some
pretty good upper level divergence on Tuesday afternoon. The
environment shouldn`t change much frankly and the ECMWF ENS
members are again picking up on thunderstorms a little farther
north on Tuesday in our Oregon zones. Again, it`s looking more
isolated on Tuesday.

Finally by Wednesday, the upper level low begins to move
eastwards and we should see some more thunderstorms around the
region. Locations in northern California and east of the Cascades
will see thunderstorm activity during the day yet again.
Essentially, we should see some cloud to ground lightning
somewhere in out forecast area between Monday through Wednesday.

After the low finally departs the region, Temperatures will
likely warm towards the 100`s on Friday and Saturday. It will be a
warm period and there are hints a thermal trough could build over
us during next weekend, which usually leads us to some hot, dry
and unstable weather.

-Smith

&&

.AVIATION...06/00Z TAFs...VFR levels persist across northern
California and southern Oregon this afternoon and evening. Cumulus
clouds are developing over area terrain, but these pose no threat.
Marine stratus looks to return to the Oregon coast tonight, with IFR
or LIFR levels possible. This layer looks to clear on Sunday
morning, with gusty winds developing along the coast just before the
afternoon. Inland areas will remain under VFR levels with normal
diurnal winds. -TAD

&&

.MARINE...Updated 200 PM PDT Saturday, July 5, 2025... Winds will
continue to increase into this evening as the thermal trough
rebuilds. Winds and seas will be hazardous to smaller crafts south
of Cape Blanco this evening. These hazardous conditions will then
expand northward with steep seas across the waters by Sunday
evening. However, gales are anticipated south of Port Orford by
Sunday evening through Monday. Conditions improve slightly by
Monday evening.

-Smith

&&

.FIRE WEATHER...Updated 200 PM PDT Saturday, July 5, 2025...An
upper ridge will continue to move in over the area the remainder of
this weekend. This will bring dry, stable conditions the rest of
today and through Sunday with temperatures getting back above normal
levels. A few fair-weather cumulus are out there this afternoon,
but no thunderstorms. On Sunday, there can be a few buildups over
the SE mountains (Warners) during the afternoon/evening, but
there doesn`t appear to be enough instability/moisture to produce
deep convection. As such we`ve kept thunder out of the forecast.
Otherwise, the forecast will be for continued near to slightly above
normal temperatures, seasonal humidities, and the typical diurnal
wind patterns, although general east flow late this weekend into
early next week leading to drying, especially across the ridgelines,
where poor to moderate recoveries are possible.

Heat builds further Monday and Tuesday with high temperatures
in the mid to upper 90s and even some readings in the West
Side/NorCal valleys exceeding 100F.

Low pressure will then develop off the California Coast setting up
just west of SF Bay Sunday night into Monday. This is a similar set
up to the pattern that brought convection to the area for several
days this past (last) week. One difference though is that the deep
southerly flow of moisture available during the last event appears
to be less with this one and, as such, a limiting factor for
convection. That said, latest guidance continues to show
at least a slight chance (15 to <25%) of thunderstorms each pm/eve
beginning Monday and continuing through Wednesday. NorCal seems to
be favored, but also portions of the Cascades and East Side. It
should be noted that model PWs with this potential convection are
around 0.50-0.75" (esp southern and eastern areas, where values
could be below 0.50" at times), so any high-based convection that
does develop might not produce any rainfall. We`ll continue to
monitor the guidance to hone in on lightning potential and areas
that stand the best chance over the coming days. The low will get a
kick onshore Wednesday and move through NorCal and into NW Nevada
during the afternoon/evening. Still could be activity in NorCal and
east of the Cascades then, but do expect drier westerly flow to move
in Wednesday night and the thunder risk to end. Expect slight
cooling Wed/Thu, but a return of hotter weather again by Friday.
There also could be a period of weak offshore E winds Wednesday
night through Friday morning.

-Spilde

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory from 11 PM this evening
     to 8 AM PDT Monday for PZZ350-370.

Small Craft Advisory until 8 AM PDT Monday for PZZ356-376.

     Gale Watch from Sunday morning through Monday morning for PZZ356-
     376.

&&

$$