Area Forecast Discussion Issued by NWS Medford, OR
000
FXUS66 KMFR 112317
AFDMFR
Area Forecast Discussion
National Weather Service Medford OR
301 PM PDT Thu Apr 11 2024
.UPDATE...Updated aviation discussion.
&&
.SHORT TERM...This afternoon will be the warmest of the week with
temperatures warming to the mid to upper 50s at the coast with
60s and 70s inland, including for east side locations!
Temperatures are already well into the 60s in east side locations.
Temperatures are in the low 70s currently in the Rogue Valley.
Temperatures tomorrow afternoon will be near to slightly below
normal for west side with east side still near to slightly above
normal.
The next low pressure system is moving closer from the northwest
today with a cold front that will bring rain/snow to the area.
Satellite has been showing the increase in mid/upper level clouds in
the area since this morning. The coast and western Douglas and
Josephine counties will see increasing rain chances tonight,
although the heaviest rain through Friday morning will be offshore
with less than a quarter of an inch expected in these areas. West
side locations west of Medford will see their heaviest rain Friday
afternoon with 0.25-0.50 possible. The main area of concern for
thunderstorms the next two days will be east into parts of Lake,
Modoc and Klamath counties. The European Extreme Forecast Index
shows that strong cape and a strong shear environment will be
present in the areas described above. With that, these areas will
hold a chance for gusty winds and small hail the next two
afternoons. However, Friday afternoon`s thunderstorm potential
has been expanded to include more of the Rogue Valley as
thunderstorm chances have increased to 15-25% there. East side
will start to see stronger winds in the afternoons with winds of
10-20 mph possible.
Saturday night into Sunday morning snow levels will drop to 4,500`-
5,500`, bringing snow to areas in Northern California with 4"-7"
possible in the Warner Mountains Saturday night through Sunday
night. Precipitation continues through parts of Sunday, so please
review the long term to see when the impacts from this system
will end. -Hermansen
.LONG TERM...Sunday through Thursday, April 14-18, 2024...The
cooler, active weather pattern will continue into Sunday across
southern Oregon and northern California. The upper level low
spinning near or just offshore of the San Francisco Bay area will
pivot inland by Sunday morning, eventually shifting into the Great
Basin during the late afternoon/evening. A colder air mass will
arrive and be in place Sunday morning across NorCal such that snow
levels will drop to 4000-4500 feet. This will allow remaining
precipitation to change to snow in some areas, especially SE
Siskiyou and Modoc counties. Given preceding mild weather, winter
impacts are expected to be mostly minor. Right now, most likely/
preliminary snow amounts by Sunday morning (11 am) look to be in the
1-3 inch range above 4500 feet in Siskiyou/Modoc, with some of the
higher passes, like Cedar Pass on Highway 299 east of Alturas
getting up to 6 inches. Other passes that may be impacted by wet
snow Sunday morning -- Highway 97 near Grass Lake, Highway 89 near
Snowman Summit/Pondosa and Highway 139 south of Tionesta to Adin.
The higher pass on Sawyers Bar road west of Etna could also see a
little snow accumulation, but I-5 should be OK.
Shower chances diminish (to 10-30%) Sunday afternoon west of the
Cascades as heights begin to rise, but fairly high PoPs (40-70%)
linger over the East Side, where there is still a slight chance
(20%) of thunderstorms. Isolated showers probably linger into Sunday
evening over the far East Side due to the proximity of the low. High
temperatures Sunday will be at least a few degrees below normal in
most cases, but 10-15F below normal in NorCal.
There should be a break Sunday night through Monday night for most
areas, though onshore flow may bring just enough moisture in the 925-
850mb layer to squeeze out some sprinkles near the coast/western
Douglas County or sprinkles/flurries in eastern portions of Douglas
County. Other areas remain dry with temperatures moderating but
still remaining at least a few degrees below the seasonal norms
Monday afternoon. If skies remain mostly clear Monday night, low
temperatures could be in the low to mid 30s in the valleys west of
the Cascades.
The next upper trough will drop southward from western Canada into
the PacNW Tuesday resulting in a bout of gusty NW winds (not too
unusual though). While we expect an increase in PoPs, shower chances
are highest across the north (in Oregon) and near the Cascades (30-
50%). Snow levels near or even a bit below 2500 feet Tuesday morning
will rise to 3500 feet or higher Tuesday afternoon. This will bring
a reinforcing shot of cooler air with another cold night expected
Tuesday night.
Broad upper troughing will linger over the area Wednesday into
Thursday. While there is a chance (15-30%) of showers each
afternoon/evening due to instability, moisture is lacking so much of
the time/area will be dry. Best chance of showers will be in the
mountains. Temperatures should return closer to normal. -Spilde
&&
.AVIATION...12/00Z TAFs...VFR prevails in all areas through early
this evening. Westerly breezes are expected over the next couple
hours this afternoon/evening in Medford and Klamath Falls. Strongest
winds will be near higher terrain and east of the Cascades. Isolated
showers/a stray thunderstorm could pop up in southeastern Siskiyou
and Modoc counties up to around Lakeview in the 03-15z time frame.
Meanwhile, a weak cold front will approach the coast with lower
ceilings moving into North Bend around or just after 06z along with
areas of light rain/drizzle. These lower ceilings/light rain will
spread into the coast ranges/Umpqua Basin through the overnight, but
probably stop short of the Rogue Valley/Medford. Conditions will
remain VFR elsewhere through the majority of the TAF period.
The character of precipitation changes Friday afternoon as the low
pressure follows the front and the atmosphere becomes more
convective. Precipitation will move into the area in waves as the
low spins southeast-wards. Scattered showers are most likely near
and west of the Cascades, but also over portions of the east side
(especially from the Warner Mtns in eastern Modoc County northward
into Lake County). There is also a slight chance (~20%) of
thunderstorms. In between those areas, there will be a relative
minimum in shower potential (though not zero). More gusty winds out
of the south are expected over and eastwards of the Cascades late
Friday afternoon into the evening. -Spilde/CSP
&&
.MARINE...Updated 130 PM Thursday, April 11, 2024...Improving
conditions this morning continue through Friday afternoon, though
low pressure moving south is likely to bring rain late tonight into
Friday. Meanwhile, stronger, gusty northerly winds are likely in the
offshore waters, beyond 60 nm from shore.
As this low moves inland into central California, these stronger
north winds are likely to move into the coastal waters Friday night
and persist through the weekend. Hazardous conditions are likely to
return Friday night as gusty north winds build steep to very steep
wind driven seas through the weekend. Have issued a small craft
advisory to account for this, but a hazardous seas warning may be
needed. -Schaaf/BR-y
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.
CA...None.
PACIFIC COASTAL WATERS...Small Craft Advisory from 5 PM Friday to 5
PM PDT Saturday for PZZ370-376.
&&
$$