Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 241558
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
858 AM PDT Wed Apr 24 2019

.DISCUSSION...12z sounding showing a deep marine push into the
Rogue Valley this morning with stratus layer around 3000 feet.
Even had a few reports of light sprinkles/drizzle, but these are
few and far between. Morning clouds west of the Cascades will
erode with mostly sunny skies expected this afternoon. Expect
gusty northerly breezes north of the Umpqua Divide this afternoon
and especially along the coast where it will be windy with gusts
exceeding 35 mph at times. Overall, high temperatures will be
within a couple of degrees of where they were yesterday, though
it`ll probably be slightly cooler in areas where the clouds are
this morning.

A weak surface trough will remain over the SE portion of the
forecast area this afternoon, and with some instability present,
expect some cumulus to develop from the Shasta region eastward to
the Modoc. The new 12z (GFS) shows lots of showers developing in
this area. But, as we saw yesterday, it was significantly overdone
in its depictions of convection, likely due to parameterization
and other factors. Meanwhile, 00z ECMWF/12z NAM and convection
allowing models (HRRR, HREF) are not showing much happening at all.
We have left a slight chance of afternoon showers in the forecast
there, but the vast majority of the time will be dry. -Spilde

&&

.AVIATION...For the 24/12Z TAFS...Marine stratus continues to result
in IFR conditions near Brookings with MVFR from about Cape Blanco
north and into the southwest Oregon valleys. The inland valleys will
be fastest to clear with gradually improving conditions during this
morning. There also will be gusty northerly low level winds (as high
as 40 KT) over the coastal waters to the coast into this evening.
Otherwise, VFR is generally expected to prevail through this
evening. Late tonight into Thursday morning, a mix of IFR/MVFR
stratus over the coastal waters is expected to expand along the
coast north of Cape Blanco. -DW

&&

.MARINE...Updated 800 AM PDT Wednesday, 24 April 2019...A thermal
trough along the coast will continue to strengthen  through this
evening bringing moderate to strong north winds and steep to very
steep seas across the area. Very steep seas are expected from Coos
Bay south and Gales are expected across areas south of Cape Blanco.
North of Coos Bay, expect mainly steep seas and small craft winds.
Winds and seas will lower early Thursday and into early Friday but
expect some continued steep seas and small craft advisory level
winds. The thermal trough is likely to re-strengthen late Friday
through the weekend bringing another round of strong north winds
that are expected to reach gale force south of Cape Blanco. Models
indicate this second round of gales will peak late Saturday into
Sunday and may be stronger than today`s event.

Uncertainty in the  forecast increases beyond the weekend, as a
trough may arrive with showers and weakening winds. But, it is
slightly more probable that the trough will remain farther east and
allow northerly winds to remain gusty and stronger than normal. -CC

Note:  Buoys 46027 and 46015 are both out of service. According to
the National Data Buoy Center, 46015 is scheduled to be redeployed
in August. Redeployment of 46027 has not been scheduled. Buoy 46229
is the only operational buoy in the coastal waters between Newport
and Eureka.

&&

.PREV DISCUSSION... /Issued 659 AM PDT Wed Apr 24 2019/

UPDATE...Updated the aviation and marine sections.

AVIATION...For the 24/12Z TAFS...Marine stratus continues to result
in IFR conditions near Brookings with MVFR from about Cape Blanco
north and into the southwest Oregon valleys. The inland valleys will
be fastest to clear with gradually improving conditions during this
morning. There also will be gusty northerly low level winds (as high
as 40 KT) over the coastal waters to the coast into this evening.
Otherwise, VFR is generally expected to prevail through this
evening. Late tonight into Thursday morning, a mix of IFR/MVFR
stratus over the coastal waters is expected to expand along the
coast north of Cape Blanco. -DW

MARINE...Updated 400 AM PDT Wednesday, 24 April 2019...A thermal
trough along the coast will continue to strengthen  through this
evening bringing moderate north winds and steep to very steep seas
south of Cape Blanco. The stronger winds will spread north of Cape
Blanco today and then weaken some Thursday into early Friday,
especially north of the Cape. The thermal trough is likely to re-
strengthen Friday through the weekend bringing another bout of
strong north winds that may reach gale force, at times, south of
Cape Blanco. Uncertainty in the forecast increases beyond the
weekend, as a trough may arrive with showers and weakening winds.
But, it is slightly more probable that the trough will remain
farther east and allow northerly winds to remain gusty and stronger
than normal.

Note:  Buoys 46027 and 46015 are both out of service. According to
the National Data Buoy Center, 46015 is scheduled to be redeployed
in August. Redeployment of 46027 has not been scheduled. Buoy 46229
is the only operational buoy in the coastal waters between Newport
and Eureka.

PREV DISCUSSION... /Issued 255 AM PDT Wed Apr 24 2019/

DISCUSSION...Today will feature similar weather conditions compared
to Tuesday. High temperatures will be 10 to 15 degrees above
climatological norms for this time of year. Mostly sunny skies are
expected in the afternoon. One notable feature is the expected
gusty north winds at the coast and over the coastal waters.
Morning clouds that are pooled in the valleys west of the Cascades
will clear out later this morning. After reviewing all the latest
data, we`ve kept thunderstorms out of the forecast another day.
No convection-allowing models are suggesting storms today, and
post-processed thunderstorm guidance is showing the same thing.
Additionally, the synoptic upper ridge pattern doesn`t support
storms. We`ve maintained shower chances over Eastern Siskiyou and
Modoc Counties.

On Thursday the flow aloft will be more southerly and will support
greater instability over mainly Eastern Siskiyou and Modoc Counties,
so we maintain a slight chance of thunderstorms there. Elsewhere,
Thursday will be the warmest day of the week, just a few degrees
warmer than today. A dry cold front will approach the forecast area
from the west on Thursday afternoon, and this will help tighten
pressure gradients and result in gusty winds over most of the
forecast area.

A cooler air mass will result in Friday afternoon high temperatures
about 5 degrees cooler than Thursday but still 5 to 10 degrees above
normal for this time of year. Dry northwesterly flow aloft continues
on Saturday, and high temperatures will be similar to Friday.
The following long-term discussion is from Tuesday`s dayshift.
Keene

Saturday through Tuesday night...The extended continues the
conditions expected after a dry cold front: windy, and somewhat
cooler than earlier this week. Temperatures will be closer to
normal for this time of year, but will continue to be a few
degrees warmer than normal. Winds will be quite breezy on Saturday
as well.

A ridge of high pressure begins to slowly build back into the
Pacific Northwest and northern California, but it will only be a
weak high pressure at best. This will keep temperatures on the
somewhat cooler side, but we`ll also remain dry. That being said,
the thermal trough will try to build in on Sunday and possibly
briefly Monday, which could bring weak easterly winds and slightly
warmer temperatures to most of southern Oregon and northern
California. Then another front digs in from the north bringing the
next shot of rain and high elevation snow Tuesday night into
Wednesday. -Schaaf

&&

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

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT Friday
     for PZZ350-356-370.
     Hazardous Seas Warning until 5 AM PDT Thursday for
     PZZ350-356-370-376.
     Small Craft Advisory from 5 AM Thursday to 11 PM PDT Friday for
     PZZ376.

$$

MAS/NSK/DW


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