Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 062138
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
238 PM PDT Thu May 6 2021

.DISCUSSION...The latest surface analysis shows the cold front
positioned just inland away from the coast. Pressure rises are being
observed at the coast with winds shifting from the south to
southwest. The front will continue to march it`s way east west of
the Cascades this afternoon and this evening east of the Cascades.
Winds are already increasing in several locations east of the
Cascades and Shasta Valley. Precipitation has occurred with many
locations along the coast and coastal mountains getting some
measurable rain. In fact, the highest totals so far have been these
areas. The big winner so far has been Gold Beach with 0.23 of an
inch, followed by Quail Prairie with 0.22 of an inch, Red Mound
0.20 of an inch and Flynn Prairie with 0.18 of an inch.

Unfortunately, as is typical with these narrow bands of
precipitation and frontal systems, the front will lose it`s steam
with respect to precipitation coverage and amounts as it pushes
further inland. Despite this, spotty light precipitation is still
likely for portions of Josephine, Douglas and north to northwest
Jackson county, but amounts will be less compared to the coast and
coastal mountains.

Gusty winds are likely into this evening east of the Cascades with
700mb winds between 25 ad 35 kts with even stronger winds above
700mb that could mix down near the surface and a wind advisory
remains in effect. Gusty breezes are also expected in the Rogue
Valley and Shasta Valley into early this evening, before
diminishing.

Tonight, the upper trough will approach, north of the area with the
best chance for precipitation remaining north of the Umpqua Divide
and northern Cascades. Elsewhere its expected to remain dry with
gusty breezes near and at the ridges east of the Cascades. Upslope
flow along the west facing slopes of the Cascades and Siskiyous will
result in cloud cover, with a sprinkle or two possible due to the
upslope flow, but probably not enough to measure.

The upper trough will swing east of the of the area Friday
afternoon. Still could not rule out spotty light precipitation north
of the Umpqua Divide in the morning, otherwise the trend is for
drying conditions. We`ll have another day of breezy winds Friday
afternoon and evening for most locations with winds a bit stronger
east of the Cascades, but were not expecting them to reach advisory
criteria.

Dry weather and near normal temperatures are expected over the
forecast area as upper level northwest flow dominates the region.
A few showers are expected to pass just to the north of the area
on Sunday morning. This will result in a temperature drop of a
few degrees between Saturday afternoon and Sunday afternoon.

An upper level ridge of high pressure extending from the CA
coastline up to the Gulf of Alaska will nudge east over the PacNW
resulting in a significant warming trend over the region Monday
through mid week. As of now...Wednesday looks to be the warmest
day of the week...with temperatures generally 10 to 15 degrees
above normal for the middle of May.

Along with a warming trend...the region is expected to remain
dry...with no rain in sight. In fact...according to the Climate
Prediction Center`s 6 to 10 day outlook...valid from May 12th
through the 16th...the area is expected to remain dry with above
normal temperatures. All hope is not lost however...as quite a few
ensemble members from both the GFS and the ECMWF are indicating a
change in the weather pattern by next weekend. Additionally...the
Climate Prediction Center`s 8 to 14 day outlook is also keying on
this...calling for below normal temperatures and normal
precipitation. We will continue to watch this closely over the
next week or so! -MAP/CCR


&&

.FIRE WEATHER...Updated 200 PM PDT Thursday 06 May 2021...The
latest surface analysis shows the cold front positioned just inland
away from the coast. Pressure rises are being observed at the coast
with winds shifting from the south to southwest. The front will
continue to march it`s way east west of the Cascades this afternoon
and this evening east of the Cascades. Winds are already increasing
in several locations east of the Cascades where relative humidities
are lower. Precipitation has occurred with many locations along the
coast and coastal mountains getting some measurable rain. In fact,
the highest totals so far have been these areas. The big winner so
far has been Flynn Prairie with 0.17 of an inch of rain.

However, as is typical with these narrow bands of precipitation
and frontal systems, the front will lose it`s steam with respect to
precipitation coverage and amounts as it pushes further inland.
Unfortunately, no precipitation is expected in the Rogue Valley and
east of the Cascades.

Temperatures will trend cooler across the region, with humidities
higher over the West Side. The latest guidance continue to show
higher relative humidities east of the Cascades compared to
yesterday. The increase may not be as much as the west side, but it
may be just enough to prevent critical conditions from developing.
With that said, we still can not rule out brief critical conditions
for the eastern portions of fire zone 624 and 285 into early this
evening.

Winds across the East Side are expected to be stronger ahead of the
front due to a combination of a tighter pressure gradient and
stronger winds aloft (700mb winds between 25 and 35 kts) into this
evening. Green up has occurred in fire zones 625 and 285 due to
recent precipitation and as a result their fuels are in the moderate
category. However fire zone 624 did not benefit nearly as much and
fuels are still receptive below 5,000 feet. Therefore, given the
above mentioned reasoning regarding winds and relative humidities,
we`ll continue to headline. A Wind Advisory remains in effect,
however, with wording to illustrate increased fire weather concerns.

Cooler temperatures, higher humidities, and even a few showers north
of the Umpqua Divide and northern Cascades, are expected Friday as
an upper level trough swings through. Breezy winds are likely east
of the Cascades once again Friday afternoon and evening, but should
not be near as strong as those of Thursday, and relative humidities
will also be much higher.

Dry but cooler weather is  expected Saturday, then a warming and
continuing drying trend is expect through the middle of next week as
upper level ridging and the coastal thermal trough return.
-BPN/Petrucelli

&&

.AVIATION...For the 06/18Z TAF Cycle...A weak narrow cold front will
traverse southern Oregon and norther California during the day
today.  At 18Z the front was along the coastal mountains getting
ready to move over the Illinois Valley and Umpqua Basin. Ceilings
associated with this front are mostly MVFR with scattered IFR cigs.
Mountain obscurations are a given with the front also.  The front
will slowly weaken as it pushes inland but these MVFR cigs with
mountain obscuration will persist as it moves slowly eastward today.
 Expect the front to affect the Cascade Range between 21Z and 00Z.
Numerous rain showers will also accompany the front.  After the
front passes the Cascades, it will weaken considerably such that
areas east of the Cascades should see mostly broken cigs with some
MVFR cigs but may not see any IFR conditions at all. Only scattered
rain showers are expected by then.  Winds will be gusty this
afternoon and evening, especially east of the Cascades.  A fire near
Chiloquin is producing smoke that may bring local vsbys down a bit.
However windy conditions this afternoon should help to spread out
the smoke. -Sargeant


&&

.MARINE...Updated 200 PM PDT Thursday 06 May 2021...A weak front
that moved onshore this morning has left behind west to northwest
winds of 10 to 20 kts.  These winds are not expected to change much
during the next 24 hours.  A thermal trough will develop near the
coast Friday afternoon, bringing gusty north winds and choppy seas
to areas south of Cape Blanco through the weekend and most of next
week. -Sargeant


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 11 PM PDT this evening for ORZ030-031.

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 2 PM PDT this afternoon for
     PZZ350-356-370-376.

$$


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