Helm, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

870
FXUS66 KMFR 240612
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1012 PM PST Sat Nov 23 2024

.UPDATE...Updated Aviation Discussion.

&&

.AVIATION...24/06Z TAFS...The weak short wave disturbance east of
the Cascades earlier this evening will continue to push eastward out
of the area overnight. Still a few isolated showers out there around
the Mt Shasta region southward to around Redding, but these are more
the exception than the rule. Most areas remain dry overnight.

Residual VFR ceilings are breaking up this evening (but local MVFR
and higher terrain obscuration persist). This continues to present a
tricky forecast with fog potential given all the recent moisture of
the past few days. With enough clearing and winds decoupling from
the boundary layer, fog seems likely in some wet side valleys,
including the Rogue, Illinois, Umpqua and other coastal valleys. In
fact, recent observations from both Grants Pass and here in Medford
have shown reduced visibility at times. However, some of these
places keep the cloud deck most of the night (Roseburg) and guidance
indicates VFR prevailing. We maintain LIFR fog in the Medford TAF
toward Sunday morning since we`ve already seen quick radiational
cooling this evening. We`ve left it out of Roseburg, but we`ll
continue to monitor and amend, if needed.

Meanwhile, another front will be approaching the coast from the
Pacific and this will bring the potential for low level wind speed
shear to North Bend, Roseburg and Medford overnight or Sunday
morning. Wind speeds 1500-2000 feet above the ground are 25-30kt
greater than surface winds (light just below the inversion). So,
we`ve included this in the TAFs for those terminals. The front will
bring some rain and MVFR ceilings beginning late Sunday morning to
the coast, spreading inland during the afternoon. Isolated
thunderstorms are possible over the coastal waters. Breezy to gusty
S-SE winds are possible Sunday afternoon in the Shasta Valley,
southern Rogue Valleys and over the East Side. -Spilde


&&

.MARINE...Updated 830 PM PST Saturday, November 23, 2024...South
winds increase to gales overnight and continue through Sunday with
very steep, hazardous seas. Isolated thunderstorms are also
possible. Low pressure moves onshore Sunday evening and winds will
decrease, but conditions remain unsettled through at least Tuesday
morning. Then, high pressure builds for the remainder of the week
with relatively low seas. -Spilde/Smith

&&

.PREV DISCUSSION... /Issued 859 PM PST Sat Nov 23 2024/

UPDATE...We`ve addressed the incoming windy event for the Shasta
Valley by hoisting a Wind Advisory for them between 7am and 8pm
Sunday. Winds look to increase in the Rogue Valley as well
tomorrow but we have low confidence in a significant impact here
and gust values reaching criteria. Stavish

PREV DISCUSSION... /Issued 428 PM PST Sat Nov 23 2024/
DISCUSSION...An upper low off the southern British Columbia
coastline continues to bring unsettled weather to the area. The
upper low is forecast to shift slowly south along the Pacific
Northwest coastline...bringing rounds of steady precipitation
mixed with showers through at least the first part of next week.

The first round of steady precipitation will begin impacting
southern Siskiyou county Sunday morning...impacting the west side
by Sunday afternoon. The activity will spread east through the
day. Another round of precipitation spreads from west to east
early Monday morning into the afternoon hours.

Snowfall along the southern Siskiyou passes will be the biggest
impact of the storm...and a Winter Storm Warning was issued to
account for this hazard. Please see the warning for additional
information.

Scattered showers linger through much of Tuesday before the upper
low moves southeast into northern California allowing for upper
level ridging to set up over the area Wednesday into Thanksgiving.

Unfortunately with high pressure building over the area...there is
the possibility of dense fog over the valley locations...so
warm days aren`t expected.

One thing we do have confidence in regarding this pattern change
mid next week...dry weather through at least the holiday weekend.
In fact...only 1 ensemble member...so about 3% of the models...are
showing any precipitation from Saturday through the following
Tuesday after Thanksgiving. -Riley

AVIATION...24/00Z TAFS...A weak short wave disturbance east of
the Cascades this evening will push eastward out of the area
overnight. As a result, isolated to scattered showers early this
evening will gradually diminish and end late this evening/overnight.

Residual VFR ceilings (local MVFR and higher terrain obscured)
should also gradually break up. This presents a tricky forecast with
fog potential given all the recent moisture of the past few days.
With enough clearing and winds decoupling from the boundary layer,
fog seems likely in some wet side valleys, including the Rogue,
Illinois, Umpqua and other coastal valleys. However, some of these
places keep the cloud deck most of the night (Roseburg) and guidance
indicates VFR prevailing. We have gone with LIFR fog in the Medford
TAF toward Sunday morning since clearing is expected there this
evening which would maximize radiational cooling and the potential
for fog later tonight. We`ve left it out of Roseburg for now, but
will re-evaluate this evening.

Meanwhile, another front will be approaching the coast from the
Pacific and this will bring the potential for low level wind speed
shear to North Bend, Roseburg and Medford overnight or Sunday
morning. Wind speeds 1500-2000 feet above the ground are 25-30kt
greater than surface winds (light just below the inversion). So,
we`ve included this in the TAFs for those terminals. The front will
bring light rain and MVFR ceilings beginning late Sunday morning to
the coast, spreading inland during the afternoon. Breezy to gusty S-
SE winds are possible Sunday afternoon in the Shasta Valley,
southern Rogue Valleys and over the East Side. -Spilde

MARINE...200 PM PST Saturday, November 23, 2024...Gusty south winds
will continue today, with seas remaining high and steep. Another
front will approach the area this evening, bringing south gales and
very steep wind driven seas tonight through Sunday. Conditions
remain unsettled the upper level low finally moves eastwards between
Monday and Tuesday. High pressure builds for the remainder of the
week with relatively low seas. -Smith

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...Wind Advisory from 7 AM to 8 PM PST Sunday for CAZ081.

Winter Storm Warning from 10 AM Sunday to 4 AM PST Tuesday for
     CAZ082.

PACIFIC COASTAL WATERS...Gale Warning until 7 PM PST Sunday for
     PZZ350-356-370-376.

&&

$$

MAS/MAS/MAS