Wildfire in Oregon, August 1 to 6, 2023

Area Forecast Discussion
National Weather Service Medford OR
831 PM PDT Mon Jul 31 2023

.DISCUSSION...The current trend remains for temperatures to
gradually warm into the weekend when near-triple digit highs are
possible in west side valleys. The main updates for this evening
were to show the chance of smoke in haze for the short- term
forecast. With the northerly winds today, there was more smoke
from the Bedrock fire spotted in Medford. There is now haze in
parts of Jackson County for Tuesday afternoon/evening with support
from the earlier observations. The trend of afternoon gusts near
20-25 knots has been kept in the grids east of the Cascades.
Please review the previous discussion for more details on the
forecast and the late week thunderstorm chances. -Hermansen

&&

.AVIATION...01/00Z TAFs...Inland areas (including KRBG, KMFR, and
KLMT) can expect VFR conditions to continue through the TAF period,
with periods of normal breezy summer winds this afternoon. After an
afternoon of gusty northerly winds, the marine stratus is again
expected to develop later this evening for the coast into the Camas
Valley. This will continue through the overnight hours before
returning to MVFR conditions later in the morning.
-Schaaf/Hermansen

&&

.MARINE...Updated 800 PM PDT Monday, July 31, 2023...Gusty north
winds and steep, wind-driven seas will persist south of Cape Blanco
into Wednesday morning, with the strongest winds expected south of
Gold Beach. Isolated gales are possible in this area through Tuesday
afternoon, but the thermal trough will weaken later Tuesday into
Wednesday and north winds will trend lower. The thermal trough is
likely to strengthen again at the end of the week, with steep to
very steep seas likely returning. /BR-y

&&

.PREV DISCUSSION... /Issued 241 PM PDT Mon Jul 31 2023/

DISCUSSION...An upper level ridge centered over the southern United
States is deepening, keeping lower pressure systems in the Gulf of
Alaska away from the area.  This will support slightly warmer
temperatures today, with highs reaching the high 80s to mid 90s.
Coastal areas will stay in the low to mid 70s. Skies will be clear
tonight with the exception of some east side development over higher
terrain and marine stratus returning this evening. HRRR smoke
guidance is showing some accumulation in southern Curry and
Josephine counties this evening from the Flat Fire and across Lake
and Klamath counties from the Bedrock Fire, but should clear out as
winds pick up on Tuesday.

With the stability of the southern ridge, conditions are expected to
be steady through the week. One exception to the consistency will be
chances of thunderstorms east of the Cascades on Thursday and Friday
afternoon and evening. Movement in the center of the ridge's high
pressure will let moisture move over the western United States,
bringing precipitable water amounts in the region to 0.7 to 1.0
inches through the second half of the week. Convective instability
and upper level vorticity could provide uplift to that moisture that
could allow thunderstorms to develop. Activity is expected to be
isolated, but could potentially occur anywhere across the east side.
Future guidance may allow for more specific areas to be considered.
Slight changes in wind or moisture patterns could change the
thunderstorm chances, either making them more or less likely.

This weekend, that southern high pressure center looks to move west
to the California/Baja California area. This would put northern
California and southern Oregon firmly under the ridge. Future model
guidance does show a further warming trend this weekend, with west
side valleys forecast to be in the high 90s to low 100s this weekend
into early next week. The upper ridge does look to flatten quickly,
which would result in zonal flow and more seasonal temperatures.
-TAD

FIRE WEATHER...Updated 200 PM PDT Monday, July 31, 2023...A ridge
of high pressure is expected to sneak into our CWA over the next few
days, leading to warmer overall temperatures which will decrease the
minimum relative humidity values to below critical thresholds for
Northern California and east of the Cascades. Winds will be more
relaxed, keeping many regions out of red flag criteria. However, in
FWZ-280 there will be a concentrated area of red flag conditions
Tuesday afternoon in the Salmon Mountain range, but these do not
meet the duration criteria. In addition, as a result of the building
high pressure the marine push extent into Douglas County and other
coastal valleys should trend weaker as there is less onshore wind.

The next focus will be on the increased chance for thunderstorms
east of the Cascades later next week. These storms will start on
Thursday afternoon (15-30% chance), peak on Friday (20-40% chance),
and be more isolated on Saturday (10-20%). There is high confidence
that storms will start off dry on Thursday, even under the storm
cores (10% chance that more than 0.1" falls). By Friday, storms may
begin to moisten up, with the chance of a wetting rain increasing up
to 20-40% (higher to the east). Storms Thursday and Friday should
have a northbound storm motion at about 15 mph, and on Saturday,
storms are forecasted to move south at around 10mph.

-Danny/Kilometers

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 8 AM PDT
     Wednesday for PZZ356-376.

&&