Grants Pass, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

408
FXUS66 KMFR 130213
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
713 PM PDT Tue Aug 12 2025

....Updated the Aviation and Marine sections...

.AVIATION...13/00Z TAFs...Thicker, more persistent LIFR/IFR marine
stratus is expected along the coast tonight through Wednesday
morning, with only partial improvement during the afternoon. The
marine layer is expected to thicken again early Wednesday
evening, and continue to deepen Wednesday night.

Inland areas will see VFR levels through the TAF period. Gusty,
breezy afternoon westerly winds are expected to be slightly stronger
than typical again during Wednesday afternoon.
-DW

&&

.MARINE...Updated 700 PM PDT Tuesday, August 12, 2025...Advisory
level seas will linger in outer waters through tonight, due to
ongoing north winds and residual steep seas. The thermal trough
rebuilds briefly Wednesday into Thursday, spreading gusty north
winds and steep seas to all of the coastal waters, with the
strongest winds and steepest seas south of Cape Blanco. Broad
upper level troughing arrives Friday, disrupting the thermal
trough pattern and allowing conditions to become relatively calm
through the weekend, and likely into early next week. -BPN

&&

.PREV DISCUSSION... /Issued 224 PM PDT Tue Aug 12 2025/

DISCUSSION...An upper level ridge remains in control of conditions
over northern California and southern Oregon this afternoon,
supporting another day of hazardous daytime high temperatures in low-
lying areas. Extreme Heat Warnings remain in place for the Shasta,
Scott, and Klamath River valleys in Siskiyou County as well as for
the Rogue, Applegate, and Illinois valleys in Jackson and Josephine
counties. Heat Advisories remain in place across parts of Douglas,
Modoc, southern Klamath, and eastern Siskiyou counties. These
products remain in place through tonight. Other areas continue to
see above seasonal temperatures as well.

Wednesday brings a pattern change to the area. An upper trough will
help to cool daytime highs by 5 to 10 degrees for most areas, ending
hazardous levels of heat. Temperatures remain above seasonal norms,
so individuals sensitive to heat may still want to remain cautious
when going outside. Upper instability moving with the trough is
expected to cause breezy conditions, especially over elevated
terrain.

Dry and breezy conditions today and on Wednesday are bringing
elevated fire weather concerns. Please see the Fire Weather
discussion for additional details.

Daytime highs cool to seasonal levels on Thursday, and look to
remain there through the weekend and into next week. A low pressure
system settling into the Gulf of Alaska will bring zonal flow to end
the week, with flow turning southwest through the weekend. An
atmospheric river looks to point at the area on Friday and Saturday,
bringing possible precipitable water values of 1.5-2.0". In the
absence of a significant forcing mechanism, this moisture and
onshore flow will bring rainfall chances to the Oregon coast and
lesser chances to inland areas. Amounts are overall expected to be
light, with 0.1 to 0.3 inches of rainfall over the coast through
both Friday and Saturday. Inland rainfall will generally be measured
in the hundreths through those two days.

For Sunday and beyond, the atmospheric river moves to the south and
upper flow turns more southwesterly. Rainfall chances across the
area will decrease, but chances of afternoon and evening
thunderstorms may be in the forecast. Forcing beyond convective
heating is not currently in the forecast, so any activity would
likely be isolated and is unlikely to be severe given current
guidance. -TAD

FIRE WEATHER...Updated 200 PM PDT Tuesday, August 12,
2025...Another day of hot temperatures, though slightly cooler than
the last two days, and dry conditions is expected today. Extreme
Heat Warnings and Heat Advisories remain in effect through late
tonight. A cooling trend is expected from Wednesday onward as the
pattern transitions back to being dominated by an upper level trough.

The pattern begins transitioning today as the upper ridge moves
westward and allows a dry front to pass through the region today
into Wednesday. This will bring gusty winds to the region both today
and Wednesday, and with low daytime RHs, this will lead to critical
fire weather conditions across portions of the area. A Red Flag
Warning is in effect from 2p-8p today for gusty winds/low RH for
portions of Fire Weather Zones (FWZs) 620/622/624. Similar
conditions are expected again on Wednesday, and the Fire Weather
Watch has been upgraded to a Red Flag Warning for the same areas and
same time. Isolated critical conditions are possible across FWZs
280/285/625, but at this time, it looks like winds will remain just
below criteria for those zones. While breezy winds will continue
into Thursday, improving trends in temperatures and RHs will limit
the extent of critical fire weather conditions.

Friday into the weekend, low pressure in the Gulf of Alaska will
maintain gusty winds in the region, but also send a wetter front
through the area. This system looks quite similar to the one that
moved through the Pacific Northwest early last week, but
precipitation chances extend farther south comparatively so. Our
region will still be on the tail end of this front so we don`t
expect much precipitation for inland locations. That said, there are
fairly high chances (40-70%) for measurable precipitation along the
coast and into the Umpqua Basin, with around a 20-30% chance for the
Rogue/Illinois/Applegate Valleys. Precipitation chances drop off
considerably for areas farther south and east. Again, we don`t
expect a soaking rain, but there`s currently a 40-60% chance for
0.10" and 20-30% chance for 0.25" along the coast north of Cape
Blanco and into the Umpqua Basin for late Friday into Saturday.
South of the Umpqua Divide, chances for even a 0.10" drop to 20-30%.
At the very least, we`ll see increased cloud cover, increased
daytime humidities and below normal temperatures over the weekend
which will limit fire weather concerns.

There`s some indications for thunderstorm concerns on Saturday and
Sunday along/east of the Cascades and across northern California. At
this time, convective parameters don`t look overly impressive, but
we`ll continue to monitor model trends and make adjustments to the
forecast as needed. /BR-y

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Extreme Heat Warning until 2 AM PDT Wednesday for ORZ024-026.

     Heat Advisory until 2 AM PDT Wednesday for ORZ023-029.

     Red Flag Warning until 8 PM PDT this evening for ORZ620-622.

     Red Flag Warning until 8 PM PDT this evening for ORZ624.

CA...Extreme Heat Warning until 2 AM PDT Wednesday for CAZ080-081.

     Heat Advisory until 2 AM PDT Wednesday for CAZ082>085.

PACIFIC COASTAL WATERS...Small Craft Advisory from 2 AM Wednesday to
     11 PM PDT Thursday for PZZ356.

     Small Craft Advisory from 2 AM Wednesday to 5 AM PDT Thursday
     for PZZ350.

     Small Craft Advisory until 5 AM PDT Thursday for PZZ370.

     Small Craft Advisory until 11 PM PDT Thursday for PZZ376.

&&

$$