403
FXUS66 KMFR 072151
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
251 PM PDT Mon Jul 7 2025

.DISCUSSION...Temperatures will be warm this afternoon with
temperatures already in the 90s in west side valleys. More locations
in west side valleys will reach the triple digits this afternoon.

This afternoon`s thunderstorm chances were expanded last night and
now include more portions of Douglas, Josephine and Jackson
counties. Sunnier skies are still present west of the Cascades with
cumulus building east, especially in Modoc County. The
shower/thunderstorm chances will come later this afternoon and into
the evening, mainly between 4-9 PM. Cloud-to-ground lightning, gusty
winds nearing 50 mph and small hail will be possible.

Also wanted to note some models are indicating a few returns at the
coast tonight that track north. There is a less than 10% chance of
thunder for areas near the coast and slightly inland (into western
Josephine and western Douglas counties), but wanted to bring this
possible outcome to light.

Tomorrow morning will be warmer with more west side locations seeing
lows in the 60s. Tomorrow afternoon will not be as warm as today. An
upper low near San Francisco will be moving towards Southern Oregon
later tomorrow into Wednesday, and this will bring breezier
conditions in the afternoons. Another thunderstorm chance comes
tomorrow afternoon. This will be focused on northern Klamath and
Lake counties at a 25-35% chance while a line of 15-25% chances
extends to the southwest into Siskiyou County.

The last thunderstorm chance of this string comes Wednesday and
is concentrated in central Lake County and eastern Klamath County.
Forecast CAPE values in this region will be near 250-350 J/kg.
Surrounding areas have CAPE up to 200 J/kg, so will look at this
as the CAMs come in to see if the coverage needs to be extended.

In the long term ridging will start to build into the weekend, and
this will bring a return of heat the area. There is currently a 40-
60% probability to see 100 degrees in Medford from Friday through
early next week. For now, dry conditions are forecast during that
time frame. -Hermansen

&&

.AVIATION...07/18Z TAFs...Marine stratus peeled back to the
immediate coast north of Cape Blanco this afternoon (North Bend
is VFR currently). The stratus (MVFR/IFR) persists over most of
the coastal waters, where areas of fog may also limit visibility.
Expect the marine layer (IFR/LIFR) to move back inland this evening
into far western Douglas and Coos counties, including North Bend,
then persist through most of Tuesday morning.

Across interior SW Oregon and NorCal, conditions are VFR.
Cumulus are beginning to develop in Modoc County and expect
further development through this afternoon with isolated
thunderstorms that will mostly move from SE to NW. These high-
based cells are possible from western Modoc up Winter Rim and
westward to the Cascades, as well as across Siskiyou County and the
Siskiyou Mountains. Latest guidance suggests enough mid-level
steering flow that a cell or two could drift off the mountains into
the west side valleys of Jackson, Josephine and eastern Douglas
counties this evening. Main risks with thunderstorms this
afternoon/evening will be cloud to ground lightning and gusty
outflows. Thunderstorm activity should decrease after
04Z with VFR through Tuesday morning. -Spilde

&&

.MARINE...Updated 845 AM PDT Monday, July 7, 2025...A thermal
trough pattern will maintain hazardous seas south of Port Orford
this morning, with small craft conditions elsewhere. Conditions
begin to improve this afternoon as the thermal trough weakens and
north winds ease, but seas will remain steep to very steep through
this evening and steep through tonight. Conditions further
improve for all areas Tuesday and Wednesday, then the thermal
trough returns for the latter half of the week. -DW/Hermansen

&&

.FIRE WEATHER...Updated 200 PM PDT Monday, July 7, 2025...Upper
ridging over the area this afternoon is bringing hot weather
over the interior with some triple digit readings expected in the
west side valleys and temperatures in the 90s for most locations
east of the Cascades. This is resulting in low RH values over the
East Side with some already in the 10-15% range. For late this
afternoon/evening, with low pressure off the NorCal coast, expect
cumulus to build over the higher terrain, first across NorCal and up
along Winter Rim, but then over the Siskiyous and the Cascades.
Since we`re still under the influence of the upper ridge, forcing
for thunderstorm development and moisture is fairly weak. Even so,
model guidance is showing isolated thunderstorms popping up this
afternoon and evening with storm motions generally off toward the
NW. Model PWs with this potential convection continue to be shown
around 0.50-0.75" (esp southern and eastern areas, where values
could be below 0.50"). So, any high-based convection (10-12k ft or
so) that does develop might not produce any rainfall. For this
reason, we`ve indicated "dry" thunderstorms in the official
forecast. Mid-level steering flow appears strong enough (~15-20 kt)
that should cells get going across the southern Cascades/Siskiyou
Mtns, they may be able to drift off the terrain and over portions of
the Rogue and/or Illinois valleys or even into eastern Douglas
County (probably S&E of Roseburg) this evening. Gusty outflow winds
are possible in the stronger cells. Elevated instability
persists tonight across portions of NW Cal and even SW Oregon.
While probabilities are low (generally less than 15%), we have
seen in the past, nocturnal activity that migrates toward or even
off the coast in these situations. Would not be be surprised
if a stray thunderstorm develops in those areas tonight.

Isolated to widely scattered thunderstorms (15 to 35%) continue
Tuesday afternoon/evening as the low edges closer to the coast.
East Side areas north of the Sprague River Valley and NW of Abert
Rim (northern sections of FWZs 624/625) have the highest
probabilities of thunderstorms (25-35%), so we have upgraded the
Fire Weather Watch to a Red Flag Warning (2-11 pm PDT) there, but
isolated activity could extend back to the SW across the Cascades to
northern and western Siskiyou County. Models show the convection
beginning in our area, then lifting north into Deschutes County, so
there are some uncertainties in quantity of lightning prior to the
storms exiting to the north.

By Wednesday, an upstream "kicker" trough will cause the low off the
Cal coast to move onshore. This will maintain a slight chance to
chance of thunderstorms across SE portions of the forecast area,
but especially from Modoc County northeastward into southern Lake
County. We have added a Fire Weather Watch to the SE portion of FWZ
624 and southern part of FWZ 625 (2-8 pm PDT) for abundant
lightning on dry fuels. The trough axis pushes east of the area
fairly quickly Wednesday evening, so felt confident enough that
convection would be ending earlier in the evening.

Following the trough passage, drier westerly flow aloft moves in
Wednesday night and the thunder risk ends. Expect slight cooling
Wed/Thu over inland areas, but northeast winds provide warmer
weather to the south coast. A return of hotter weather is expected
Friday into the weekend with fairly typical late-day summertime
breezes, but also dry afternoon humidity and poor to moderate RH
recovery at night. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 2 PM to 11 PM PDT Tuesday for ORZ624-625.

     Fire Weather Watch from Wednesday afternoon through Wednesday
     evening for ORZ624-625.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 2 AM PDT Tuesday
     for PZZ350-356-370-376.

     Hazardous Seas Warning until 8 PM PDT this evening for PZZ356-
     376.

&&

$$