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000
FXUS66 KMFR 261022
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
322 AM PDT Fri Apr 26 2024

.DISCUSSION...Waves of showers are passing through the area this
morning as an upper level trough moves onshore. Rainfall amounts
have been heaviest along the coast and in the Cascades, with
around 0.75"- 1.25" over the last 24 hours. Elsewhere, amounts
over the last 24 hours range from a few hundreths to a tenth for
areas east of the Cascades and 0.10"-0.50" for areas west of the
Cascades. Snow levels are hovering around 5000 ft this morning, so
winter weather impacts are limited to the higher passes. Amounts
of 8 to 10 inches are forecast with the highest amounts expected
for the back county and highest peaks. As these waves of showers
pass through the region, there will likely (70%-90%) be periods of
1"/hr snowfall rates in the Cascades through this morning. Though
recent warm temperatures will significantly limit snow
accumulations on roadways, those traveling around Crater Lake,
Diamond Lake, and Willamette Pass should be prepared for reduced
visibilities. The highest peaks of the Siskiyou Mountains, Warner
Mountains, and Siskiyou County can also expect to receive
measureable accumulations. A Winter Weather Advisory remains in
effect above 5000 ft through this afternoon, and details can be
found at WSWMFR.

Showers will continue into the afternoon hours today as the upper
level trough moves overhead, and this combined with some daytime
heating will lead to thunderstorm chances (20%-30%) across the
southern and eastern areas (eastern Siskiyou/southern Lake/Modoc
Counties). In addition, expect some gusty winds across the region
this afternoon, especially near any of the heavier
showers/thunderstorms.

Shower activity diminishes this evening and overnight. Then after a
short break Saturday morning, another shortwave arrives Saturday
afternoon. This will be a quick moving and weakening wave, but it
will be the leading edge of sustained zonal onshore flow that will
persist into early next week. This pattern is known to produce
ongoing light showers, although most precipitation will remain
confined along and west of the Cascades with the best chances for
accumulating precipitation after Saturday night expected along the
coast, Cascades and north of the Rogue-Umpqua Divide. Ensembles are
in good agreement with regards to precipitation chances outside of
these locations and chances really drop off for these areas after
Saturday night.

Snow levels are expected to remain fairly consistent, throughout
this time, hovering roughly around 5000 feet. Given the light
snowfall amounts in the forecast, we aren`t expecting any wintry
weather impacts during this time. Additionally, given the zonal flow
expected into early next week, we don`t expect any sharp warm ups or
cool downs during this time. Continued cloud cover will result in
some cooler than normal daytime highs (upper 50s/low 60s West Side,
low to mid 50s East Side) and near normal overnight lows with no
freeze concerns for areas west of the Cascades.

Tuesday into Wednesday of next week, temperatures trend a bit warmer
with a few upper level disturbances expected to pass nearby and
bring additional chances of precipitation. More details can be found
in the previous shift`s long term discussion below:

Heading into Tuesday,  500 mb heights appear more zonal over Oregon
as another short wave swings through the state of Washington.  This
appears to be the driest day as the chance of rain is generally
below 15% everywhere except along the coast near Cape Blanco and
Coos Bay. Given this drier trend, temperatures should push into the
70`s in Medford, Grants pass and the upper 60`s in other locations
across our forecast area.

Eventually, an upper level low out of the Gulf of Alaska will likely
push into the Pacific Northwest around Wednesday. This should result
in another round of wetting rain, although the NBM probability of
precipitation of 0.01 inches over 12 hours only show a 50 to 60%
chance of rain. Therefore, some of the ensemble members might show
different times of arrival of the front on Wednesday night and
Thursday morning or it is drier than what some of the deterministic
data show.

The other thing that this low will bring is some cooler more
unstable air behind the cold front. This can be seen in the snow
levels falling down to 4000 feet behind the front, which should
eventually pass through sometime around Thursday.  Even with plenty
of solar heating, high temperatures are still anticipated to push
into the lower 60`s in many cities east and west of the Cascades.

Overall, the extended forecast looks active yet with little to no
impacts. We`re lacking significant moisture or forcing to bring
impactful rain or snow to the region. One may say it is very Spring
like for our forecast area.

-Smith

&&

.AVIATION...(25/06Z TAFs) MVFR ceilings are expected to continue
along the coast through this TAF cycle and likely areas of IFR
ceilings overnight, too. For all other areas, VFR will be the more
dominate category with areas of MVFR in heavier showers. Cloud
cover continue to cause mountain obstructions across the region,
too. Friday afternoon, winds at least east of the Cascades are
expected to become gusty. -Miles/CC

&&

.MARINE...Updated 200 AM Friday, April 26, 2024...Moderate west
to northwest winds and steep fresh seas will continue today. While
wind speeds gradually diminish late this afternoon and evening,
steep west swell will result in seas hazardous to small craft. These
conditions are likely to last into late tonight. Another front will
move into the waters late Saturday morning, then onshore later
Saturday afternoon. Seas may become chaotic once again during this
time and winds could approach small craft north of Cape Blanco.
Additionally, we are going into a rainy pattern with chances over
the waters nearly every day in the forecast through middle next
week. -Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 2 PM PDT this afternoon above 5000
     feet for ORZ027-028.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 2 AM PDT Saturday
     for PZZ350-356-370-376.

&&

$$

MNF/MAP