067
FXUS66 KMFR 011204
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
504 AM PDT Sat Jun 1 2024

.Updated Aviation Discussion.

.SHORT TERM...A shortwave trough will move across the area today
bringing a general increase in cloudiness, slightly cooler
temperatures, and breezy afternoon winds. Moisture is limited with
this system, so expect dry weather. Along the coast, this trough
will result in a deeper marine layer and models support a 10%
chance of drizzle along the immediate coast, especially in the
afternoon and evening. Northwest winds will pick up in the
afternoon and evening today for most inland areas, but especially
east of the Cascades and in the Shasta Valley (with gusts to
around 25 mph).

On Sunday and into Monday, a stronger and very moist frontal
system arrives. This front is associated with a strong plume of
moisture (precipitable water values of 1.5 or higher and moisture
transport values (IVT) of 500-750 kg/ms). This is an unusually
moist system for June. Model Extreme Forecast Index (EFI) of QPF
from the ECMWF shows values approaching 1 in the Cascades to our
north, but also healthy values along the Southern Oregon coast and
into the Cascades. This is a strong indication that the front
will be considerable for its rain production for this time of
year.

Precipitation will gradually move south and eastward across
the area Sunday through Monday morning. Rain will begin along the
coast and across much of Douglas County Sunday morning, spreading
inland across areas from the Cascades west Sunday afternoon, then
increasing and spreading across the area Sunday night and Monday
morning. Wetting rainfall is likely for areas from the Cascades
westward late Sunday through early Monday, with moderate to heavy
rainfall along the coast, across the coastal mountains, Douglas
County and the Southern Oregon Cascades (especially Crater Lake
north). Areas that see the heaviest rain, may experience localized
ponding of water on roadways, especially in urban areas or areas
of poor drainage. Otherwise, expect the rain to be largely
beneficial. Some showers are expected to linger Monday afternoon
then taper off by Monday evening.

Models continue to support storm total rain amounts of 1-2 inches
along the coast, and locally up to 3 inches in some of the coast
ranges. 0.50-1.50 inches of rain is expected in the rest of
Douglas County and into portions of the Illinois Valley. Here in
the Rogue Valley, most likely amounts will range from 0.20-0.40 of
an inch. Over the Southern Oregon Cascades, rainfall totals of
0.5 to 1.5 inches is expected, mainly from Highway 140 northward.
East of the Southern Oregon Cascades and from the Shasta Valley
eastward in Northern California, amounts will be mostly 0.10 of an
inch or less with little or nothing in southern Modoc County.

As this system moves through late Sunday and Monday, gusty west
winds are also likely, highest from the Cascades east. Gusts of
around 20-25 mph are expected from the Cascades east Sunday
afternoon/evening, increasing to 25-35 mph (and up to 40 mph
across higher terrain east of the Cascades) Monday afternoon.



&&

.AVIATION...01/12Z TAFs...VFR conditions will prevail through the
TAF period for most locations. The exception being along the coast
where MVFR ceilings are being observed north of Cape Blanco and into
the Coquille Basin. The lower conditions will improve in the
Coquille basin towards 17z as the marine stratus burns off, but it
may not improve at all along the coast, north of Cape Blanco. Expect
some gusty afternoon breezes, especially for inland terminals this
afternoon into early this evening. -Petrucelli

&&

.MARINE...Updated 200 AM Saturday, June 1, 2024...Calmer conditions
are expected through this evening.

A front will arrive on Sunday morning, bringing gusty south winds
and an increasing west swell. Conditions hazardous to small craft
are expected Sunday morning to areas north of Gold Beach due to
increasing winds and swell. Additionally, a period of moderate to
heavy rainfall is expected Sunday afternoon into Monday morning.

The front will move inland Sunday afternoon, but another front is
expected to move into the waters Sunday night which will result in
increasing southwest winds. This front will move inland Monday
morning with winds diminishing. However, westerly swell will
increase during the day resulting in continued Small Craft
conditions.

Hazardous conditions are likely to continue through the week, though
due to varying weather patterns. An upper level trough will remain
to the northwest, and this will send another, heavier, longer period
swell (9 to 12 ft at 12 to 14 seconds) into the waters on Wednesday.
Meanwhile, the thermal trough will likely return, bringing the
return of strong north winds and steep to very steep wind driven
seas for the latter half of next week. -Petrucelli


&&

.PREV DISCUSSION... /Issued 229 PM PDT Fri May 31 2024/

LONG TERM...Monday afternoon (6/03) through Thursday night(6/06)...

Post frontal showers will persist through Monday afternoon, but will
quickly diminish through the evening as strong ridging builds into
the region behind the departing system. The model suites in previous
runs have depicted the ridge well in control of the area, with
steadily warming temperatures and no chances for rain throughout the
extended term.

The recent runs, however, have started to show a more complicated
pattern, with an area of swift zonal flow, mainly lying just to our
north, with ridging to the south and troughing to the north. This
would keep our area mostly dry and hot, just as previously thought,
although maybe not quite as warm. Also, with the zonal flow in the
vicinity, a stray impulse could brush by southern Oregon, producing
some light rain chances along the coast and the upper Umpqua Basin
through Tuesday night. That being said, the most likely scenario
remains dry.

Wednesday and Thursday, the ridge builds north in response to a
deepening trough upstream over the eastern Pacific. Depending on how
far east that trough is, the ridge axis will remain overhead keeping
the area dry and very warm for this time of year (about 10 to 15
degrees above normal), or just to our east, allowing for some
southwesterly flow aloft. This southwesterly flow solution is also
very warm, but typically produces a chance for convection,
particularly over northern California and along and east of the
Cascades in Oregon, so there is a low chance, around 15%, for
afternoon thunderstorms somewhere in the area mid to late next week.
Details on the timing and exact locations will need to wait until
the models better resolve the situation. -BPN

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory from 5 AM Monday to 5
     PM PDT Tuesday for PZZ350-356-370-376.

&&

$$

CC