Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 081047
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
347 AM PDT Sat May 8 2021

.DISCUSSION...

Skies remain mostly clear across the region tonight with some high
clouds off the Oregon coastline. Some of those high clouds will
move in later this morning, but it should remain clear for the
majority of the night until sunrise as the clouds move in.
Temperatures are expected to come close to freezing in many
locations west of the Cascades tonight prompting the freeze
warning. We`ll keep the freeze warning going since we`ll be so
close to freezing over some locations, but most locations will
probably remain above freezing for tonight. In addition, we`re
expecting a fair amount of frost on vegetation by sunrise.


By sunrise, more upper level cloud cover will build in with
temperatures trending warmer compared to Friday. Winds will still
remain rather breezy around 10 to 15 miles per hour out of the
Northwest as a strong surface pressure gradient forms over the
region.

By tonight into Sunday morning, models continue to show an upper
level disturbance moving into the region bringing cloud cover and
perhaps a bit of precipitation over central Oregon. The
probability of precipitation is around 10 percent over the
northern portions of our forecast area. If any rain does fall, it
will be light since there isn`t much moisture to work with.
Average RH in the lower layers of the atmosphere is around 60 to
70 percent with modest atmospheric lift.

By Monday and Tuesday, a thermal trough and high pressure will
build along the Oregon coastline. Monday will be warmer than
normal, but we`re looking at temperatures around 10 to 15 degrees
warmer than normal on Tuesday and Wednesday as the thermal trough
moves back inland. We are not forecasting any high temperature records
as temperatures are forecast to be 5 degrees too cool. However,
the NBM shows a 50% chance to break Mount Shasta`s record of 87
set back in 1976 on the 12th. In any case, it will be a warm day
for the middle of May as the ridge centers over southern Oregon
and northern California.

The last topic worth discussing is when the 500 mb ridge axis
shifts east towards the end of the week with some troughing off
our coastline. The NBM is forecasting a 10 to 15 percent chance of
rain along our coastline with lower probabilities farther inland.
This seems reasonable given the synoptic pattern and inherent long
range forecast uncertainties. Like everything else we`ve seen
these last few weeks, the precipitation will likely be light as
ensembles are not forecasting a lot of moisture or high values of
integrated water vapor transport in the region late next week.

-Smith

&&

.AVIATION...For the 08/06Z TAF Cycle...VFR is expected to persist
through Saturday evening, with the exception of patches of late
night into early morning MVFR both from around Cape Arago northward
including the Coquille and lower Umpqua valleys, and at the north
facing slopes near Canyonville and Ashland. Also, IFR may spread to
the coast north of Cape Blanco, including KOTH, after 03Z Saturday
evening. DW


&&

.MARINE...Updated 3 AM PDT Saturday 8 May 2021...A thermal trough
will persist near the coast into the middle of next week. Gusty
north winds and steep seas are expected south of Cape Blanco through
Sunday afternoon. Winds and seas are then likely to build with steep
seas expanding north of Cape Blanco late Sunday. South of Cape
Blanco seas will likely become very steep and northerly gales are
possible late Sunday into the first part of next week at least.

Latest data suggests Small Craft Advisory could end late in the week
as the thermal trough weakens. Keene


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Freeze Warning until 10 AM PDT this morning for ORZ024-026.

CA...None.

Pacific Coastal Waters...Gale Watch from Sunday afternoon through Monday afternoon for
     PZZ356-376.
     Small Craft Advisory until 5 PM PDT Monday for PZZ356-376.
     Small Craft Advisory from 5 PM Sunday to 5 PM PDT Monday for
     PZZ350-370.

$$


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