Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 220535
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1035 PM PDT Sat May 21 2022

Updated AVIATION Section

.DISCUSSION...22/00Z NAM in.

Some cumulus managed to pop over higher terrain from the Cascades
east this afternoon and evening. There were light showers embedded
amongst them, and three east side Agrimet stations did report some
measurable precipitation, although one of them looks like a false
report. The other two reported 0.02 and 0.01 inches of
precipitation. The clouds should be dissipating soon as the air
mass stabilizes.

While inland areas are clearing, marine stratus is returning to
the coastal waters. Expect the stratus to move onshore along the
north coast and into the Umpqua Basin tonight, clearing back to
the coast Sunday. The south coast will also see clouds return, but
coverage will initially not be as thick as the nearshore air mass
is dry from recent low level easterly flow.

The next several days will be relatively quiet weatherwise with no
systems expected through Wednesday night. Dry northwest flow aloft
is in place over the Pacific Northwest with a long wave ridge
offshore. That ridge will gradually move east with the ridge axis
moving onshore Sunday, but another broader flatter ridge will
replace it offshore, keeping the northwest flow in place over the
area. That ridge axis will move onshore Tuesday night.

So, expect dry weather through Wednesday with a warming trend over
the inland areas. A thermal trough will remain near the coast,
with moderate to strong northerly winds along the coast and over
the coastal waters, especially south of Cape Blanco, peaking in
the afternoons and evenings.

The one exception to the warming trend will be along the coast and
in the Umpqua Basin. Initially, the marine layer will keep those
areas cooler. However, all but the north coast will join the
warming party Tuesday into Wednesday.

The thermal trough will swing inland Wednesday. Winds will
diminish over the coastal waters, but will raise temperatures
inland. Wednesday looks to be the hottest day of the upcoming
week with inland highs 5 to 15 degrees above normal.

Long term discussion from the Saturday afternoon AFD...Thu 26 May
through Sat 28 May 2022. And just as summer seems to be settling
in for the season, a blast from the recent past is expected as a
deepening low moves in from the west, displacing the ridge, and
bringing a front onshore Thursday. A slow progression to this
system was expected due to the preceding ridge and this expectation
was resolved in the models and the arrival time has been delayed
to the Thursday evening and overnight hours. The slowing of the
system did not seem to impact precipitation amounts though, with
totals in the mountains forecast to be less than half an inch
(minimal if any new snow is expected). Given that the front is
forecast to pass at night, during the period of poorest mixing, we
are not anticipating strong surface winds outside of the higher
mountain terrain.

A slight chance of showers should remain along the western slopes of
the coast ranges and Cascades as moisture wraps around the low
through Saturday. We should also observe normal to a few degrees
below normal temperatures for this time of year. Otherwise, the
Friday and Saturday timeframe should be on the quiet side,
weather wise. -Miles

&&

.AVIATION...22/06Z TAFs...VFR will persist through Sunday evening,
with the exception of IFR/MVFR low clouds and fog expected over the
coastal waters and near shore from Cape Blanco northward, into the
Coquille Valley (including KOTH/North Bend) until around 17Z
Sunday morning. There is a chance for some IFR/MVFR stratus in
portions of southern Douglas County/near Roseburg briefly around or
just after sunrise; otherwise, VFR prevails there too. -Spilde

&&

.MARINE...Updated 800 PM PDT Saturday 21 May 2022...Offshore high
pressure and a thermal trough near the coast will persist through
Wednesday. North winds will gradually weaken tonight into Sunday,
increase Monday, then weaken again on Tuesday. Winds and seas will
remain highest within the southern portion of the waters, especially
south of Nesika Beach.  A cold front is likely to arrive on Thursday
with a series of weaker disturbances to follow late in the week.
-DW/Spilde

&&

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

Pacific Coastal Waters...
     Small Craft Advisory until 11 PM PDT Sunday for PZZ356-376.
     Hazardous Seas Warning until 11 PM PDT this evening for
        PZZ356-376.
     Small Craft Advisory until 11 PM PDT this evening for
        PZZ350-370.

$$

15/15/18


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