Area Forecast Discussion
Issued by NWS Medford, OR

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144
FXUS66 KMFR 262158
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
258 PM PDT Thu Apr 26 2018

.SHORT TERM...

Showers and some rumbles of thunder are possible this evening as
the low to the west continues to approach the coast line. However,
the exact area where they may form is still up for discussion.

We`re watching some moisture and what appears to be an elevated
cold front move towards the coast line this evening. This
should provide some weak vertical motion to get storms started.
Most of the potential instability appears to be maxamized along
the Cascades. Looking at satellite again, we can see some cumulus
clouds forming under these elevated clouds. This situation
suggests that convection will really have a hard time kicking off.

With all that being said, most of the models seem the most bullish
of some lightning and stronger convective activity near the
Crater Lake area and locations near Chemult and Crescent around 3Z.
After we move past the activity this evening, rain showers should
pick up along that cold boundary. We`ll see scatted to widespread
rain showers then move north towards along this boundary into
Portland`s area.

The potential for showers and some thunder will continue through
the weekend. The colder temperatures in the low aloft and warmer
surface temperaures will naturally create a convective
environment. The best chance for lightning for all these days will
be east of the Cascades. Most of the BUFR soundings suggests just
some rumbles of thunder instead of organized thunderstorms with
only 200-400 j/kg of skinny CAPE.

The last story here is the colder temperatures for this weekend
and the start of the work week. High temperatures are expected in
the lower 60`s for valleys west of the Cascades. These high
temperatures are roughly 5 degrees below normal for this time of
year. However, the roller coaster ride of Spring will continue as
we rise back into the 70`s towards the tail end of next week.

-Smith

.LONG TERM...Monday through Thursday Night..The region will be on
the back side of the trough on Monday with residual low level
moisture in a cool to cold northerly flow. Very light lingering
showers and mountain snow showers Monday will be diminishing and
mainly west and north of the Rogue Valley. The next ridge will build
in from the west Tuesday into Wednesday with a strong warming and
drying trend.

-Schaaf/Weygand


&&

.AVIATION...26/18Z TAF CYCLE...Low clouds are pulling back from the
RBG area but satellite still shows widespread MVFR/IFR in NW Douglas
County back to the coastal counties. There could be occasional
improvement to MVFR cigs at the coast but conditions are expected to
lower to IFR again tonight.

VFR continues elsewhere but there will be some cumulus buildups this
afternoon. Showers and thunderstorms are possible over the Cascades
and Siskiyous but OTH RBG and MFR are less favorable. There is
enough instability in the Klamath Basin that LMT could see more
cumulus buildups in the afternoon.

-Bunnag


&&

.MARINE...Updated 200 PM PDT Thursday 26 April 2018...Conditions
will continue to be relatively calm through Friday with weak surface
low pressure over the waters. Upper level low pressure will approach
the area tonight and move overhead Friday into Saturday. Scattered
showers are expected from this, beginning late this afternoon and
diminishing by Sunday afternoon. Winds and seas are expected to
remain below small craft conditions through this time.

Behind the upper level low, surface high pressure will build to the
west and northerly winds will increase Sunday night into Monday,
possibly bringing small craft conditions early next week.

-Bunnag


&&

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

CA...None.

Pacific Coastal Waters...None.

$$

Smith/Schaaf/Weygand/Bunnag



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