224
FXUS66 KMFR 052139
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
239 PM PDT Wed Jun 5 2024

.DISCUSSION...

The low stratus that was covering most of the Umpqua Basin has
burnt off for the most part by this afternoon. We`re also
watching some mid level moisture and clouds move over the forecast
area this afternoon. The only concern for this afternoon with be
some a thunderstorm kicking off around Modoc County in the
Warners. Satellite data has shown some cumulus building as of
writing this AFD, so the threat of some cloud to ground lightning
is there, yet the probability of anything form is low based on
the latest observation and model forecast.As for tonight,
temperatures will fall to near normals for overnight lows with
plenty of clear skies.

Conditions will trend slightly warmer into Thursday as high
pressure remains in control. Model guidance is painting a larger
area of 15% chance of cloud to ground lightning across locations
east of the Cascades and within northern California. We have
better confidence for thunderstorms activity on Thursday as a
shortwave moves in off the coast of northern California. This wave
appears to bring more moisture to the area with convective
available potential energy increasing up to 1000 J/kg across
larger sections of the forecast area. Upper level shear also looks
good for some thunderstorm sustenance with 0-6km shear values
around 25 to 35 knots. Overall, we think we`ll see some cloud to
ground lightning across the area on Thursday, although the chances
near a specific point is around 15%-25%.

Friday should be the warmest day with high temperatures pushing
into the upper 90`s here in Medford with lower 90` east of the
Cascades, which is definitely on the warmer side for early June.
High temperatures east of the Cascades will be about 20 degrees
warmer than normal on Friday and we could be testing high
temperature records for some of those sites. The record high for
Klamath Falls and Alturas is 91 and 93 both set in 1996. We`re
currently expecting to tie both of these records.

As for heat risk and impacts on Friday, there will be a period of
high heat risk on Friday afternoon as this will be one of the
warmer days so far this summer. However, given the brief period of
warmer temperatures over multiple days, heat risk is more
moderate in our forecast area. Low temperatures drop down to their
respective normals, which will allow those at risk to recover
from the warmer daytime temperatures. Therefore, we opted to stay
away from a heat advisory given the brevity of warm temperatures
and the cooler overnight lows.

An upper level trough and some deeper south west to west flow
will bring in a little more moisture and cooler temperatures to
kick off the weekend. However, temperatures will remain warm east
of the Cascades. The upper level trough should swing through the
forecast area by Saturday afternoon or evening. As a result,
showers and thunderstorms should kick off east of the Cascades
around Lake County. The NBM currently has a 20% chance of
precipitation Saturday evening and Sunday evening east of the
Cascades. The probability of thunder actually shows some values
higher than that and peaks up to 40% Saturday evening near
Chemult.

Towards the start of next week around Monday and Tuesday, the ENS
is keeping a weak ridge over the region and the NBM is keeping
PoPs near 0%. There doesn`t appear to be any weather impacts
except for some stronger north winds in the Marine waters.
Temperatures will remain warmer than normal, although heat risk is
anticipated to be low.

-Smith

&&

.AVIATION...05/18Z TAFs...VFR conditions prevail across the area
this afternoon, although some isolated pockets of MVFR are possible
along the coast until this morning`s marine layer stratus deck fully
burns off this afternoon. Gusty northerly winds will blow along the
coast this afternoon before calming in the evening. MVFR/IFr
conditions are possible along the coast again tonight into early
Thursday morning, but should not be as extensive as it was this
morning.

Other inland areas will remain at VFR levels under clear skies.

-TAD/BPN

&&

.MARINE...Updated 200 PM Wednesday, June 5, 2024...Long period
westerly swell will gradually diminish through tonight. As the long-
period swell starts to decrease, a thermal trough will develop and
produce gusty north winds across most area waters. The strongest
winds and steepest seas will be south of Cape Blanco. Steep seas
will continue in waters north of Cape Blanco, while very steep and
hazardous wind-built seas will develop south of Cape Blanco by this
evening. Currently, these conditions are expected to continue
through at least Friday morning. Winds are forecast to peak on
Thursday evening, with gale gusts possible south of Gold Beach.

Please see MWWMFR for more detail about Small Craft Advisories and
Hazardous Seas Warnings in place through Friday morning.

Seas start to calm on Friday, although some amount of steep seas
will continue through the morning. Active seas are expected to
return on Saturday evening as a thermal trough rebuilds over area
waters and remains into next week. -TAD/BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Beach Hazards Statement until 8 PM PDT this evening for ORZ021-
     022.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT Friday
     for PZZ350-356-370-376.

     Hazardous Seas Warning from 5 PM this afternoon to 11 AM PDT
     Friday for PZZ356-376.

&&

$$