893
FXUS66 KMFR 252154
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
254 PM PDT Tue Jun 25 2024

.DISCUSSION...Hot and dry weather continues today under a
shortwave ridge, with temperatures running about 5 to 10 degrees
warmer than this time yesterday. Fairly typical summer weather is
expected during the forecast period with periods of ridging
alternating with upper level troughs that bring mostly dry fronts
through the region. As a result we`ll see periods of above normal
temperatures give way to brief periods of cool downs as these
troughs swing through the area accompanied by gusty afternoon
breezes.

One such trough swings through late tonight through Wednesday. Ahead
of this trough, however, an area of mid-upper level clouds is moving
over the region this afternoon. Radar is showing some returns
associated with these clouds, but very little, if any, precipitation
is making it to the ground. Any lightning associated with this area
of clouds and virga showers (evaporating before rain makes it to the
ground) is well to the southeast just east of Lake Tahoe. We do
expect this elevated moisture to continue to stream into the area
this evening and overnight. Models continue to show an area of
elevated instability (~50-100 J/KG in the 600-300mb layer) as this
moisture axis swings through tonight into the wee hours of Wednesday
morning. This is likely to maintain some elevated showers/virga
given a very dry sub-cloud layer. A few sprinkles could reach the
ground. While there isn`t much forcing for convection, and model
ensemble probabilities of thunder are generally 15% or less, there
have been isolated lightning flashes off the California coast this
morning. So, it certainly wouldn`t be surprising to see a flash or
two overnight, especially from around the Modoc northeast into
southern and eastern Lake County. The overall forecaster confidence
in lightning remains low, but the official forecast includes this
low probability of occurrence for those areas tonight.

We expect this moisture axis to shift to the north and east away
from the area by early Wednesday morning as another upper trough
approaches from the west. The implication of the nocturnal
lightning, however, is that if it occurs and fire starts result, a
period of dry and windy conditions would provide the weather
variable to support the rapid spread of any new fires. This happens
to be the case Wednesday afternoon in this area. We expect some
pretty gusty winds Wednesday afternoon as the upper level trough
swings through and west to southwest gusts of 25-35 mph will be
common east of the Cascades. These winds will combine with low
humidities and lead to critical fire weather conditions. A Red Flag
Warning is in place for this and more details can be found in the
Fire Weather Discussion below.

For the rest of the area, temperatures will trend quite cooler
compared to today`s values, by about 10 degrees lower than today.
This will continue Wednesday night into Thursday morning as the
cool, upper trough pushes inland through the PacNW. During that
time, there is a chance (20-30%) of light rain showers along the
Coos/Douglas/Curry Coasts and into northern Douglas County, but most
everywhere else will remain dry. Temperatures inland on Thursday
will be about 5-8F below normal for highs.

The cool down will be brief, however, as short wave ridging on
Friday brings dry, sunny weather and temperatures back to near or
slightly above normal levels. The next upper trough offshore will
approach the coast Friday night into Saturday and this will lead to
an uptick in afternoon/evening breezes again, especially over the
east side. Shower chances increase (20-40% chance) along the coast
and into Douglas County Saturday night into Sunday as the upper
trough moves onshore yielding yet another cool down for inland
sections. There is also a chance of showers in portions of northern
Klamath and Lake counties (15-25% chance) Sunday afternoon.

Aside from late night and morning stratus along the coast, dry
weather will prevail early next week. -Spilde/BR-y

&&

.AVIATION...18Z Tuesday, June 25, 2024...IFR conditions in marine
stratus are north of Cape Blanco and south of Brookings this
morning. This is starting to slowly dissipate today.

Otherwise, VFR conditions are expected to prevail through the TAF
period for inland locations, with breezy afternoon and evening
westerly winds. Winds will be strongest east of the Cascades with
gusts up to 25 kt. /DW/Hermansen

&&

.MARINE...Updated 230 PM Tuesday, June 25, 2024...The thermal
trough pattern gets disrupted today as an upper level trough
approaches the region. Sub-advisory conditions expected through at
least Thursday. A weak front will push through the region later
today into Wednesday, bringing a deep layer of low clouds and a
chance of showers Wednesday night. A return of the thermal trough
pattern is expected Thursday into Friday night, with steep seas
possible south of Cape Blanco. Another front and deep marine layer
are likely to disrupt the pattern, with improved conditions for the
weekend. /BR-y/Hermansen

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 8 PM PDT this evening for ORZ624.

     Red Flag Warning from noon to 8 PM PDT Wednesday for ORZ624-625.

CA...Red Flag Warning until 8 PM PDT this evening for CAZ285.

     Red Flag Warning from noon to 8 PM PDT Wednesday for CAZ285.

PACIFIC COASTAL WATERS...None.

&&

$$

MNF/BMS/ANH