NWS Medford, OR wrote its last area forecast discussion before the first event at Feb 29, 9:20 PM PST, 2 hours 40 minutes earlier.
Area forecast discussion, Feb 29, 9:20 PM PST, 2 hours 40 minutes before
Area Forecast Discussion
National Weather Service Medford OR
920 PM PST Thu Feb 29 2024
...New Aviation...
.AVIATION (06Z TAFs)...
Unfavorable flying conditions will be one way to describe the next
24 hours as a strong upper level system continues to impact the
Pacific Northwest with rain, snow, and gusty winds. Timing on
precipitation is likely to be difficult in nailing down, but
generally expecting showers (or showers in the vicinity) at the
terminals throughout this cycle. Medford may see a rain snow mix
through the morning and early afternoon hours before transitioning
back to rain. Otherwise, expecting clouds to be generally around
2000-5000 feet through a good portion of this cycle. Gusty winds
on the eastside may lead to a airport weather warning for strong
gusts.
-Guerrero
&&
.PREV DISCUSSION... /Issued 508 PM PST Thu Feb 29 2024/
..Updated Aviation and Long Term Sections...
SHORT TERM...The continuation of a multi-day, high impact winter
weather storm continues. Winds are continuing gusty, but have
decreased below advisory strength west of the Cascades, but will
continue at higher elevations, and from the Cascades eastward.
Showers will continue through early evening, picking up as snow
levels continue to drop to around 1500 by late evening. High
resolution guidance continues to show precipitation intensity
driving the snow level down quickly such that rain mixes with or
even changes to snow by Friday morning morning, and with a strong
short wave moving across early through late Friday morning that is
indicated even stronger than the one that moved through this
morning, the chances that snow will drop to the valley floors west
of the Cascades is high. With the very narrow valleys in western
Siskiyou county snow is expected to the valley floors overnight
through the day tomorrow. Winter weather advisories are in effect
above 1500 feet, including in the Illinois Valley on Highway 199
(including Hayes Hill), for the passes north of Grants Pass on I-
5 and also Camas Mtn on Highway 42. Most likely times for the
changeover: this evening on Camas Mtn, 4-6 am for the passes
north of Grants Pass, 6-8 am for parts of the Illinois Valley
(Hayes Hill). Places like Jacksonville Hill, and maybe even
Ashland could see a changeover to wet snow late this evening into
early morning. With the heavier snow at lower elevations like the
Illinois and Camas valleys, and the valleys of western Siskiyou
county, snow could take a while to melt, if at all before even
colder low temperatures set in Saturday morning.
With cold air in place, there will be optimal conditions for snow to
accumulate on West Side valley floors (outside of the Illinois
Valley where it is highly likely; more below) over the next
handful of mornings; Friday, Saturday and Sunday. The showery
nature of the pattern beginning this afternoon makes it
challenging to pinpoint exact amounts over valley floors, however,
the best chance for lingering accumulations will be with showers
that pass through after sunset and through the early morning
hours. There could be brief periods of snow accumulations during
the daylight hours, but the late Feb/early March sun angle will
likely melt roadway accumulations fairly quickly during the
daylight hours, especially if there are any breaks in the clouds.
The place that seems to be most susceptible to major impacts from
snow, however, at least in terms of lower elevations west of the
Cascades, is the Illinois Valley and also the passes north of
Grants Pass. This is because precipitation will continue to stream
in from the Pacific on SW flow aloft right into the colder air
mass and these places could have several inches of snow by
Saturday morning. In the end, this long duration event will bring
feet (yards?) of snow to the mountains, but also impactful wintry
conditions to the East Side, northern Cal and at times to the
valleys west of the Cascades. Additional headlines and updates for
this winter storm event are likely over the next 24 hours,
especially for lower elevations, so stay tuned for updates. -Sven
LONG TERM...(Sunday 3/3 through Thursday 3/7)...The pattern will
active during this time period with an upper trough pretty much
parked over the area with a series of shortwaves moving through
resulting in periods of enhanced showers through Sunday. Snow
levels will remain near the valley floors Sunday morning and the
window of opportunity for road snow exist into at least the mid
morning hours Sunday. During the day, snow levels will come up,
and snow showers are still possible because we'll still be in a
convective environment. The convective environment typically
results in snow levels varying usually briefly lowering in heavier
showers which will be the case during the day. However with a
higher sun angle, road temperatures should warm up enough where
snow showers will likely melt.
Precipitation will continue Sunday night with a moist onshore flow
and continued shortwave energy moving through. The difference is
showers are more than likely will be on the light side with road
snow accumulations less likely for the Rogue Valley, but trace
amounts are still possible in the Illinois Valley, with up to an
inch near Hays Hill Summit.
The active pattern will continue through the first half of next
week. The operational models differ in solutions, but the ensemble
members suggest the chance for precipitation will continue Monday
through Wednesday, although precipitation amounts will generally be
light. Snow levels will also be higher during this time with most of
the concerns confined to the mountains.
AVIATION...01/00Z TAFs...Showers are occurring across southern
Oregon and northern California this afternoon and will occur
through the TAF period. Snow levels will fall again overnight,
this time to around 1400 feet MSL or so by Friday morning. As
areal coverage of precipitation is decreases from west to east
post front during the evening, and become convective. This will
result in ceilings flipping between VFR and MVFR, with MVFR
ceilings with partial terrain obscuration expected in showers
through the TAF period. A few lightning strikes may be possible at
the coast with accumulating small hail in those showers.
Moderate to strong winds will also continue through the TAF period.
Gusts up to 30 kts along the coast, 40 to 45 kts east of the
Cascades, including Klamath Falls are likely through at least 3z.
Roseburg and Medford will also have gusty winds, but they are not
expected to be as strong compared to the other terminals noted
above. -Schaaf/Petrucelli
MARINE...Updated 100 PM Thursday February 29, 2024...Winds have
shifted to the west and diminished. However, they will pick up
again this afternoon and becoming southwest, with few gusts
approaching gales. Especially where isolated thunderstorms are
present. Westerly swell will increase late this afternoon and will
continue into Saturday morning. The combination of moderate winds
and swell will result in chaotic seas in all waters through early
Saturday morning. West swells are expected to increase to 14 to
17 feet at 14 to 15 seconds late tonight through Friday evening.
Currently, a Hazardous Seas Warning is in effect through Friday at
10 PM, but it's possible this could get extended beyond this time.
However, issued a small craft advisory at the conclusion of the
hazardous seas warning because seas will remain steep through most
of the weekend. These steep swell-built seas are expected to
continue through the weekend and into next week. Winds and swell
will stay westerly as both gradually decrease. -Schaaf/Petrucelli
BEACH HAZARDS...Updated 100 PM Wednesday February 27, 2024...A
large long-period west swell will move in causing breakers in the
surf zone of 22 to 25 feet Thursday afternoon through Friday. Have
issued a high surf advisory for all beaches along the Coos, Curry,
and Douglas County beaches. Beaches could become inundated by the
waves, and the large waves will knock off anyone standing on
jetties. Never turn your back on the ocean. -Schaaf
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning until 10 AM PST Saturday for ORZ031.
High Surf Advisory until 10 PM PST Friday for ORZ021-022.
Winter Storm Warning until 10 AM PST Saturday above 2500 feet
for ORZ023>026.
Winter Weather Advisory until 10 AM PST Saturday above 1500 feet
for ORZ023-025.
Winter Weather Advisory until 10 AM PST Saturday above 1500 feet
for ORZ024-026.
Winter Storm Warning until 10 AM PST Saturday for ORZ027-028.
Winter Storm Warning until 10 AM PST Saturday for ORZ029-030.
CA...Winter Storm Warning until 10 AM PST Saturday above 3000 feet
for CAZ080.
Winter Weather Advisory until 10 AM PST Saturday for CAZ080-081.
Winter Storm Warning until 10 AM PST Saturday above 3500 feet
for CAZ081.
Winter Storm Warning until 10 AM PST Saturday for CAZ082-083.
Winter Storm Warning until 10 AM PST Saturday for CAZ084-085.
PACIFIC COASTAL WATERS...High Surf Advisory until 10 PM PST Friday
for PZZ350-356.
Hazardous Seas Warning until 10 PM PST Friday for PZZ350-356-370-
376.
Small Craft Advisory from 10 PM Friday to 4 AM PST Sunday for
PZZ350-356-370-376.
&&