National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KMFR 230531
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1030 PM PDT Mon Apr 22 2024

Updated AVIATION Section

.DISCUSSION...Satellite imagery is showing some higher clouds
across southern Oregon and northern California this evening. This
is ahead of the next system which will cause a subtle shift in the
weather beginning tomorrow with the threat of showers and
thunderstorms for portions of northern California and the East
Side of Oregon. Overall, the forecast is reasonably on track.
Please read the previous discussion for more details. -Schaaf

&&

.AVIATION...23/06Z TAFs...Other than some high clouds, conditions
remain VFR area wide late this evening. This will continue overnight
into Tuesday for most areas.

Hi-res models/soundings are showing a southerly surge of
stratus/lower ceilings and also some fog reaching the SW coast,
including Brookings ~12z, then up to around Gold Beach (Port
Orford?) by around 18z Tuesday morning. This could result in coastal
IFR/LIFR and also over the marine waters off Pt. St. George out to
about 30 NM from shore. Soundings also show a low-level moist layer
pushing into the Coquille Basin/North Bend area Tuesday morning
(around 14z), so have maintained a few hours of IFR ceiling in KOTH,
though confidence in this occurring is low to moderate.

Inland, Tuesday remains VFR, though cumulus buildups are expected to
develop in the afternoon/evening roughly south and east of a line
from the Oregon Siskiyou Mountains to Lake of the Woods (probably
southeast of Medford) to Winter Rim. In these areas, there can be
isolated to scattered showers and thunderstorms. Highest thunder
probabilities (25-40%) are in NorCal. And, given a very dry sub-
cloud layer, some stronger cells could produce gusty winds.

IFR/MVFR ceilings may return to the coast Tuesday evening. -Spilde


&&

.MARINE...Updated 830 PM Monday, April 22, 2024...A thermal
trough will maintain moderate north winds and steep to very steep
wind driven seas tonight. The strongest winds and steepest seas are
expected beyond 10 NM and south of Cape Blanco. The thermal trough
will weaken and winds will gradually ease through Tuesday, but seas
will remain steep and hazardous to small craft. A southerly surge of
stratus (with potential for lower visibilities) could reach up to
around Gold Beach late Tuesday morning. Conditions improve Tuesday
night into Wednesday, but a series of fronts will bring unsettled
weather late this week. -Spilde


&&

.PREV DISCUSSION... /Issued 519 PM PDT Mon Apr 22 2024/

DISCUSSION...Aside from some high level cirrus clouds streaming over
the region, skies are clear across the area this afternoon and
temperatures are running about 5 degrees warmer than this time
yesterday. Gusty north winds have kicked in along the coast due to
a thermal trough. This thermal trough has induced east to
northeasterly flow and is resulting the Chetco Effect, which is
bringing warm temperatures to Brookings. It`s currently 78 degrees
in Brookings, which is warmer than the Medford Airport where it`s
currently 66 degrees! Overall, it`ll be a tranquil spring
afternoon for the area, though high temperatures this afternoon
will make it feel more like late June than late April -- upper 70s
West Side and upper 60s/low 70s East Side. Dry conditions will
continue across the region today before a subtle shift in the
weather occurs Tuesday and Wednesday, and a more notable change in
the pattern occurs for the latter half of the week and into next
weekend.

Tuesday into Wednesday, the upper level pattern will transition with
low pressure developing out near 130 W west of the California coast
and low pressure pushing toward the British Columbia Coast. This
will put our region in southwest flow and some mid level moisture
will move into the area. This combined with some model indicated
instability (-2 to -4 LIs, 300-500 J/kg CAPE) is boosting confidence
in thunderstorm potential for Tuesday and Wednesday. Right now,
Tuesday looks to be the bigger day in terms of thunderstorm
coverage. The best chances (40%-70%) look to be over western
Siskiyou County and Modoc County with some potential (20%-40%)
extending into the southern portions of Jackson/Klamath/Lake
Counties. Storm motion will be from the southwest, but current
thinking is that any storms that develop over the Siskiyous would
likely stay stuck on the terrain and not really drift into the Rogue
Valley...though it`s not out of the question (10% chance) a storm
skates by Ashland Tuesday afternoon. The focus for storms on
Wednesday shifts a bit farther east on Wednesday over eastern
Siskiyou, Modoc and southern Lake Counties and the trigger looks
weaker for Wednesday, so thunderstorm coverage looks less overall.
For the remainder of the area, conditions will remain dry, though
expect an uptick in afternoon winds and cloud cover with
temperatures trending cooler.

The pattern turns cooler and wetter as we head into the extended
period. /BR-y

Extended Discussion (Thursday through Monday)...Generally it will
be cool and unsettled during the forecast period. A stronger front
will approach the coast Thursday morning, then moving inland during
the day. The bulk of the precipitation will be along the coast,
coastal mountains, Cascades and north of the Umpqua Divide. The
front will move east of the Cascades Thursday afternoon with
precipitation becoming scattered. Snow levels will also lower to
around 5500 feet along the Cascades late Thursday afternoon and
hover around that elevation Thursday night. This in combination with
a higher mid-late April sun angle, will put a cap on snow concerns
due to warm road surface temperatures, and should be mainly confined
to Crater Lake and Diamond Lake areas Thursday night.

Upper troughing remain over the area Friday, although the upper
trough axis will shift east late Friday afternoon and we could see
showers gradually diminish in coverage.

The operational ECMWF and GFs show different solutions Saturday
with the GFS showing more ridging and a relative break in the
action. The ECMWF brings another upper trough and front into the
area Saturday morning. No surprise the majority of the respective
ensemble members also show varying solutions. Even taking the
operational GFS at face value the ridding is weak and with a weak
upper trough just offshore, but still hints at a progressive
pattern. Therefore we`ll keep showers and cool afternoon
temperatures in the forecast.

Upper troughiness remains over our area Sunday through Monday, and
possibly through the middle of next week which will result in cooler
temperatures and high chance for showers over a good portion of the
forecast area. -Petrucelli

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 PM PDT Tuesday
     for PZZ350-356-370-376.

Hazardous Seas Warning until 5 AM PDT Tuesday for PZZ376.

&&

$$