Altamont, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

237
FXUS66 KMFR 220555
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
955 PM PST Fri Feb 21 2025

.DISCUSSION...Updated Aviation and Marine sections...

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.AVIATION...22/06Z TAFs...VFR conditions are present across the
area. Mid-level clouds will lower tonight as a frontal system
offshore approaches. Light rain is moving east that is currently in
Douglas County, but rain chances at both Medford and Klamath Falls
are 20% or less. Largely, conditions will stay VFR, but it`s
conceivable that ceilings lower to MVFR in some areas from the
Cascades westward with partial obscuration of higher terrain.

Starting tomorrow afternoon there could be wind shear at the coast
through 2000 feet nearing 30 to 40 knots. This has been added to the
OTH TAF, and this is expected to continue into Sunday morning. LLWS
will build in more locations, especially the Cascades and east.
-BR-y/Hermansen

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.MARINE...Updated 845 PM PST Friday, February 21, 2025...An active
weather pattern will cause hazardous conditions this weekend into
next week. Increasing south winds and building seas with conditions
hazardous to small craft will continue tonight. Winds increase to
gales tomorrow into Sunday with very steep, hazardous seas,
especially from around Cape Blanco northward. Another strong frontal
system will move through Monday with another round of gales
possible. Additionally, guidance shows a high west swell (14-17 ft
at 12 -14 seconds) building into the waters Monday into early
Tuesday, with seas possibly peaking in the 16 to 20 ft range Monday
afternoon/evening. Steep to very steep seas persist into Tuesday,
then things should calm down from Wednesday onward.
-BR-y/Hermansen

&&

PREV DISCUSSION... /Issued 216 PM PST Fri Feb 21 2025/

DISCUSSION...

Plenty of high clouds on satellite as of this afternoon as some
upper level energy moves through the region. We`are anticipating
little to no precipitation from this wave as it runs through the
Pacific Northwest.

The leading edge of an atmospheric river(AR) will hit southern
Oregon and northern California by mid day Saturday. This plume of
warm moist air will raise snow levels up to 7000 feet by Saturday
evening and bring widespread wetting rain to the region.
Precipitation rates really pick up by Saturday evening into Sunday
morning as model guidance is showing rain rates of about 1.5-2"
over 6 hours around Curry County.

Integrated water vapor transport(IVT) is also on the stronger
side around 500 to 750 for about 24 hours. Ensemble situational
awareness tools suggest these IVT values lie in the 98th percent
for this time of year, which is notable and suggest a strong AR.
The other thing that stands out is how much moisture is in the
air. Precipitable water is anticipated to reach 1 inch by Saturday
night. This would lie in the 99th percentile for this time of
year based on sounding climatology for SPC and ensemble situation
awareness tool. Our record values are right around 1.2 inches.

Between Sunday into Monday, another upper level disturbance in
this AR event will swing through region pushing the bulk of the
precipitation farther north, although we`ll still see rain
accumulate through Monday morning with a lighter rain continuing
into Tuesday.

The flooding risk is still expected to be minor/limited as this
AR hits the region through Tuesday. Main stem rivers and streams
will rise rapidly through Sunday, although none of the rivers are
anticipated to reach action stage or minor flood. The one concern
that we do have is snow melt east of the Cascades in south central
Klamath and Lake Counties. That area got the brunt of snowfall
from the event a few weeks ago. However, not much rain is
anticipated to fall east of the Cascades. Plus, overnight lows
will fall very close to freezing east of the Cascades, so the
contribution of snowmelt overnight will be very limited. However,
there have been events in the past of some small stream flooding
east of the Cascades due to snow melt, so it`s just something to
watch out for.

Aside from flooding concerns, winds will be strong on Monday
evening in the Shasta Valley. Models are anticipating a low to
form off the British Columbia coast with southwest flow at 45
knots developing over southern oregon and northern California.
Areas east of the Cascades will be breezy with the typical 45 mph
south to southwest wind gusts around Summer Lake and other exposed
locations. The GFS seems to be a little too strong with this low,
but we anticipate some strong south winds in the Shasta Valley
Monday.

Tuesday evening will be the end of this AR event with high
pressure building over the area. This quiet weather will persist
into Wednesday with temperatures continuing to remain on the
warmer side. Highs will be pushing the mid 60`s west of the
Cascades with some upper 60`s in the river valleys closer to the
coast. Temps will be a bit cooler east of the Cascades on
Wednesday with highs in the mid 50`s. A low chance of rain returns
on Thursday as an upper level wave quickly swings through the
region.

-Smith

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 10 AM PST Sunday
     for PZZ356-376.

Small Craft Advisory until 10 AM PST Saturday for PZZ350-370.

     Gale Warning from 10 AM Saturday to 10 AM PST Sunday for PZZ350-
     370.

&&

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