Area Forecast Discussion
Issued by NWS Medford, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
000
FXUS66 KMFR 292127
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
227 PM PDT SUN MAY 29 2016

.DISCUSSION...

.Short Term...Tonight through Wednesday Night...As yesterday`s
weak trough moves off to the east, upper level ridging is building
in over the forecast area and the thermal trough has started to
nudge toward us to the north. The result will be clearing skies and
warming temperatures persisting through nearly the entire short
term. By Tuesday and Wednesday, the steady warming will produce high
temperatures of 5 to 10 degrees above normal along the north coast
and up to 20 degrees above normal along the south coast and for all
areas inland. While the current forecast does not produce any triple
digit temperatures in the area, it would not be altogether out of
the question for some isolated areas to reach 100 degrees,
particularly in the western valleys of Siskiyou county, and perhaps
into the Rogue and Illinois valleys as well. There will be a slight
cooldown west of the Cascades on Wednesday as the thermal trough
shifts east, but the difference will be only barely noticeable for
most locations.

Despite the warm temperatures and mostly clear skies, there is the
possibility for some convection to develop Wednesday afternoon.
Model solutions are suggesting that enough moisture and instability
will be present over the Trinity, Siskiyou, and Cascade mountains to
perhaps produce some convection. There is the slightest hint of a
weak upper level shortwave crossing the area at some point
Wednesday, but the timing and location are different between each
individual model and each individual run, and this leaves some doubt
as to the possibility that such a lifting mechanism will be present
to get the process started. Therefore, confidence remains low, but
have kept the slight chance of thunder in the forecast, with some
modification of areal coverage to more coincide with the latest
model guidance. -BPN

.Long Term...Thursday through Sunday...Models continue to show a
broad upper level ridge over the region Thursday and Friday with
shortwave trough moving over the ridge well to the north. Models
then show agreement that the ridge will strengthen over the area
next weekend while a closed low well to the south gradually moves
inland into south central California coast. This pattern is
expected to bring continued warm temperatures to the area Thursday
and Friday with additional warming on Saturday. For Sunday, the
GFS and ECMWF models as well as the GEFS ensemble mean solution
show agreement with the closed upper low to the south gradually
shifting into the south central California coast. This pattern is
forecast to send southerly mid level moisture into the area as
well as shortwave activity. Daytime heating will provide plenty of
instability. So have leaned towards a chance to slight chance for
thunderstorms over inland areas on Sunday. Of note, the track of
this low will be the main factor in determining the chance for
thunderstorms over the area and model ensemble solutions continue
to show variability with how far south the low will be as it moves
into the California coast. Have leaned towards the mean solution
at this time. Also on Sunday, trended high temperatures slightly
lower due to the expected increase in clouds. /CC


&&

.Aviation...For the 29/18Z TAF cycle...Along the coast...MVFR
stratus deck north of Cape Blanco will remain in place through the
afternoon, gradually lifting to VFR by 21z. Guidance is showing the
deck lowering back down to IFR by this evening, before scattering
out around 10-12z as the flow turns offshore. Cigs may lower again
down to IFR temporarily during that time, but it`s too late in the
TAF cycle to have confidence in the exact timing. Elsewhere, VFR
conditions will continue through the TAF period. /BR-y

&&

.Marine...Updated 725 AM PDT Sun 29 May 2016...Small craft
conditions will continue over portions of the southern waters due to
the presence of the thermal trough, which will strengthen again late
this afternoon and evening resulting in an increase in winds and
seas, especially from Cape Blanco south. Winds will increase further
across all the coastal waters on Monday. In the late afternoon and
evening, gusts could occasionally approach Gale, especially south of
Gold Beach beyond 10 nm from shore. Winds and seas are forecast to
lower on Tuesday. -CC

&&

.Fire Weather...Next week will be warm and dry with a rapid warming
from Tuesday onward. Confidence is high that the valleys W of the
Cascades will see high temperatures in the 95 to 100 degree range as
the thermal trough shifts inland and remains W of the Cascades on
Tuesday and Wednesday. Expect minimum RH for western valleys to be
in the mid teens with fair to poor recovery Tuesday night and
Wednesday night. The thermal trough is expected to shift east of the
Cascades Wednesday but onshore push will be confined mainly to
Douglas County of Oregon.

Around Wednesday we will have to contend with thunderstorm chances
as southerly flow aloft strengthens and allows more moisture and
instability to spread north. Right now we see only the higher
terrain such as the Cascades/Siskiyous, Marble Mountains, the
mountains of the Fremont-Winema Forest being the most likely area
to see lightning strikes. Confidence is not high on how much rain
these storms will produce. By Friday instability appears to be
shunted to central California and we have removed thunderstorm
chance from the forecast. Hot temperatures inland will continue into
the end of the week. /FB


&&

.MFR Watches/Warnings/Advisories...
OR...None.

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT Monday for
     PZZ350-356-370-376.
     Gale Warning from 11 AM to 11 PM PDT Monday for PZZ376.
     Hazardous Seas Warning until 11 PM PDT this evening for PZZ376.
     Hazardous Seas Warning from 11 AM to 11 PM PDT Monday for
     PZZ376.

$$

BPN/CC/BRy/FB



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.