Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 300605
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1104 PM PDT Wed Jun 29 2022

.Updated aviation discussion.

.DISCUSSION...An update is not necessary this evening. The focus
for the next forecast issuance will remain upon the details of a
shift to a more active, cooler, potentially wet and unstable
pattern late Friday through Monday.

Patchy stratus has lingered near shore north of Cape Blanco,
otherwise skies are nearly clear. The pattern of increasing
stratus at the coast north of Cape Blanco into Douglas County will
repeat overnight into Thursday morning, then also similarly
dissipate during the day. Otherwise, temperatures across the area
will be similar to those of today. One of the few signs of the
pattern beginning to change will be some low topped cumulus
buildups expected late Thursday in the Scott Valley and far
northern portions of south central Oregon. Instability will still
be weak on Friday and a trigger will be lacking, but those same
areas (and also the southern Oregon Cascades) will have the
probability of a late day thunderstorm nudge up to 5 to 10%.

Temperatures will be around 5 to 10 degrees below normal Saturday
through Tuesday. Trough positioning will be a major factor in the
probability and coverage of showers and thunderstorms. But, the
probability is likely to generally be highest Saturday afternoon
and evening. The 18Z GFS maintains a forecast with scattered to
overcast cloud coverage during Monday night with bases around
7000 to 9000 feet msl.

&&

.AVIATION...30/06Z TAFS...MVFR ceilings have moved back into the
coast and coastal valleys (generally Cape Blanco northward),
persisting into Thursday morning before clearing to VFR. IFR
conditions will be possible near Brookings Thursday morning too,
before clearing in the afternoon. Additionally, MVFR conditions are
also expected to reach the Umpqua Basin at KRBG by Thursday morning
before clearing out Thursday afternoon. Elsewhere, VFR conditions
are expected through Thursday. Gusty winds along the coast and east
of the Cascades will diminish tonight and are expected again
Thursday afternoon. Keene

&&

.MARINE...Updated 800 PM PDT Wednesday 29 June 2022...A thermal
trough near the coast will peak tonight into Thursday, then weaken
Friday. This will bring strong north winds and steep to very
steep seas to the area, peaking in the afternoons and evenings.
The strongest winds and highest seas will occur from Cape Blanco
southward. Lower winds and seas are expected this weekend as low
pressure moves in.

&&

.PREV DISCUSSION... /Issued 530 PM PDT Wed Jun 29 2022/

SYNOPSIS...Warm and dry conditions will persist through late in
the week for inland areas. Then as an upper low gradually moves
down the PacNW coast late Friday into Saturday, there will be a
slight chance for showers and thunderstorms to develop across
inland areas. On Sunday, the chance for showers and thunderstorms
continues across most inland areas as the low remains off the
coast and an upper level disturbance is forecast to move into the
region. For Monday, this low is forecast to begin to shift north.
However, we may see some lingering light showers during the day
across the area.

* Warm and dry across inland areas into Friday.

* A slight chance (15-20%) for showers and thunderstorms across
  inland areas on Saturday. This pattern continues into Sunday
  with additional chances for showers and thunderstorms.

* On Monday, there may be some lingering showers, with shower
  activity tapering off in the evening and night except at the
  coast where light showers or drizzle are possible.

DISCUSSION...Through Friday, warm and dry weather will persist
across inland areas with daytime temperatures slightly above
normal. Morning lows may drop into the upper 30s for valleys east
of the Cascades, especially in northern Klamath and northern Lake
Counties. Otherwise, expect valley low temperatures in the 40s
east of the Cascades and generally in the 50s west of the
Cascades. Along the coast and into the Umpqua Basin, areas of low
clouds are expected during the nighttime/morning hours, with the
greatest coverage north of Cape Blanco. Additionally, a surface
thermal trough along the coast will result in gusty north winds
along coastal areas in the afternoons/evenings.

Of note, on Friday, models continue to show a slight increase in
mid level moisture from the southwest ahead of an upper trough.
This along with some weak daytime instability is expected to
result in some cumulus development over the Siskiyous, S. OR
Cascades and for areas to the northeast. Models support generally
dry weather though and are indicating only a 5-10% chance for any
showers or thunderstorms in this area.

On the weekend, an upper low will move down the PacNW coast on
Saturday. The track of this low will play a role in how much
showers or thunderstorms may develop over the area. Models and
ensembles continue to show a chance (15-25%) for showers and
thunderstorms to develop ahead of this low Saturday afternoon and
evening, with showers or thunderstorms developing initially over
the S. Oregon Cascades, Siskiyous and mountains in western
Siskiyou County then moving northeastward. So we have included a
slight chance for thunderstorms across Siskiyou, Jackson, eastern
Douglas, Klamath and northern Lake Counties. Some lingering
showers are possible Saturday night with the National Blend of
Models also indicating a 10% chance for a few thunderstorms
overnight.

Then, models and ensembles continue to indicate that the upper
low will remain just off the PacNW coast and a shortwave
disturbance will move around the low and inland on Sunday bringing
chances for showers and a slight chance for thunderstorms. There
remains variability in the model forecasts with the exact track
and timing of the upper level shortwave  which will factor into
when and how much showers and thunderstorms  develop on Sunday.
So, have used a blend of models and included a chance for showers
and thunderstorms (15-20%) across Siskiyou, Jackson, eastern
Douglas as well as for areas from the Cascades eastward.

On Monday, the upper level low shifts north. However there
remains variability in how much influence there will be with a
lingering trough or additional upper level shortwaves. This will
factor into how much lingering showers may occur on Monday. The
current National Blend of Models is favoring a slight chance to
chance (15-35%) for showers over much of the area, except Modoc
County. Showers are forecast to decrease Monday evening and
night, especially across inland areas.

FIRE WEATHER...Dry weather will continue through the end of the week
with afternoon temperatures gradually trending lower and relative
humidities higher. Were also not expecting anything unusual in terms
of winds, ,other than the typical diurnal afternoon and evening
breezes in the Rogue and Shasta Valley`s and east of the Cascades
into this evening, and again Thursday and Friday afternoon and
evening.

This weekend, we`ll be under the influence of an upper trough that
will work it`s way into the area from the northwest. This will
increase the chance for showers and thunderstorms, especially in the
afternoons and evenings. The current thinking is the best chance for
storms are expected to be from about central Siskiyou County,
portions of the Rogue Valley, Cascades and northern Klamath, and
Lake County Saturday afternoon and early evening. However, there`s a
good chance any storms will be rain producers, and there will also
be showers.

Sunday could end up being similar to Saturday, except showers could
be more widespread. Thunderstorm coverage is expected to be similar
to Saturday, except it will include all of the east side and most of
northern California. Storms that form will generally move from
southwest to northeast, so any that form along the Siskiyous could
slip over into southeast Fire zone 622 Saturday afternoon and early
Saturday evening.

Monday (The 4th of July) the overall picture is better with most, if
not all of the action (storms) shifting out of our area. Still could
not rule out isolated showers, but there`s some evidence of subtle
ridging moving into the area which could result in dry conditions
for most locations.

Looking into next week. The ensemble members point to dry weather
after the 4th. However the upper trough will still have a presence
just offshore leaving the area under a southwest flow. This pattern
typically will keep us dry and mostly stable with afternoon
temperatures near, or just a tad below seasonal norms. -Petrucelli

&&

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

Pacific Coastal Waters...
     Small Craft Advisory until 11 AM PDT Saturday for
     PZZ350-356-370.
     Small Craft Advisory until 5 PM PDT Saturday for PZZ376.
     Hazardous Seas Warning until 11 PM PDT Thursday for PZZ376.

$$

DW/Keene


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