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000
FXUS66 KMFR 222114
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
214 PM PDT Mon Apr 22 2024

.DISCUSSION...Aside from some high level cirrus clouds streaming over
the region, skies are clear across the area this afternoon and
temperatures are running about 5 degrees warmer than this time
yesterday. Gusty north winds have kicked in along the coast due to
a thermal trough. This thermal trough has induced east to
northeasterly flow and is resulting the Chetco Effect, which is
bringing warm temperatures to Brookings. It`s currently 78 degrees
in Brookings, which is warmer than the Medford Airport where it`s
currently 66 degrees! Overall, it`ll be a tranquil spring
afternoon for the area, though high temperatures this afternoon
will make it feel more like late June than late April -- upper 70s
West Side and upper 60s/low 70s East Side. Dry conditions will
continue across the region today before a subtle shift in the
weather occurs Tuesday and Wednesday, and a more notable change in
the pattern occurs for the latter half of the week and into next
weekend.

Tuesday into Wednesday, the upper level pattern will transition with
low pressure developing out near 130 W west of the California coast
and low pressure pushing toward the British Columbia Coast. This
will put our region in southwest flow and some mid level moisture
will move into the area. This combined with some model indicated
instability (-2 to -4 LIs, 300-500 J/kg CAPE) is boosting confidence
in thunderstorm potential for Tuesday and Wednesday. Right now,
Tuesday looks to be the bigger day in terms of thunderstorm
coverage. The best chances (40%-70%) look to be over western
Siskiyou County and Modoc County with some potential (20%-40%)
extending into the southern portions of Jackson/Klamath/Lake
Counties. Storm motion will be from the southwest, but current
thinking is that any storms that develop over the Siskiyous would
likely stay stuck on the terrain and not really drift into the Rogue
Valley...though it`s not out of the question (10% chance) a storm
skates by Ashland Tuesday afternoon. The focus for storms on
Wednesday shifts a bit farther east on Wednesday over eastern
Siskiyou, Modoc and southern Lake Counties and the trigger looks
weaker for Wednesday, so thunderstorm coverage looks less overall.
For the remainder of the area, conditions will remain dry, though
expect an uptick in afternoon winds and cloud cover with
temperatures trending cooler.

The pattern turns cooler and wetter as we head into the extended
period. /BR-y

.Extended Discussion (Thursday through Monday)...Generally it will
be cool and unsettled during the forecast period. A stronger front
will approach the coast Thursday morning, then moving inland during
the day. The bulk of the precipitation will be along the coast,
coastal mountains, Cascades and north of the Umpqua Divide. The
front will move east of the Cascades Thursday afternoon with
precipitation becoming scattered. Snow levels will also lower to
around 5500 feet along the Cascades late Thursday afternoon and
hover around that elevation Thursday night. This in combination with
a higher mid-late April sun angle, will put a cap on snow concerns
due to warm road surface temperatures, and should be mainly confined
to Crater Lake and Diamond Lake areas Thursday night.

Upper troughing remain over the area Friday, although the upper
trough axis will shift east late Friday afternoon and we could see
showers gradually diminish in coverage.

The operational ECMWF and GFs show different solutions Saturday
with the GFS showing more ridging and a relative break in the
action. The ECMWF brings another upper trough and front into the
area Saturday morning. No surprise the majority of the respective
ensemble members also show varying solutions. Even taking the
operational GFS at face value the ridding is weak and with a weak
upper trough just offshore, but still hints at a progressive
pattern. Therefore we`ll keep showers and cool afternoon
temperatures in the forecast.

Upper troughiness remains over our area Sunday through Monday, and
possibly through the middle of next week which will result in cooler
temperatures and high chance for showers over a good portion of the
forecast area. -Petrucelli



&&

.AVIATION...22/18Z TAFs...VFR will prevail for the next 24 hours,
albeit with some high cirrus. Gusty north winds will redevelop this
afternoon along the coast (up to 30 kt) and in the Umpqua Basin (up
to 20 kt), then gradually subside this evening. Tonight/Tuesday
morning as north winds subside, stratus could move up the coast from
the south bringing IFR/LIFR conditions as far as Gold Beach along
the coast and over the marine waters. However, probabilities are
less than 30% and cirrus clouds are expected to stay near the
coast so have not added that. -Miles/Hermansen


&&

.MARINE...Updated 215 PM Monday, April 22, 2024...A thermal
trough will maintain moderate to strong north winds and steep to
very steep wind driven seas through this evening. The strongest
winds and steepest seas are expected south of Cape Blanco. The
thermal trough will weaken tonight into Tuesday with Hazardous Seas
introduced this evening through tomorrow morning. Weaker north winds
will persist in most areas on Tuesday, but a southerly surge of
stratus could reach up to around Gold Beach, limiting visibility.
However, probabilities of this is less than 30%. Conditions will
improve with lighter winds and lower seas on Wednesday. The next
period of unsettled weather is expected Wednesday night through
Friday as a front moves through the region bringing rain showers, a
low chance for isolated thunderstorms; and behind the front, swell
dominated seas. -Miles/Hermansen


&&

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

PACIFIC COASTAL WATERS...Gale Warning until 5 PM PDT this afternoon
     for PZZ350-356-370-376.

Small Craft Advisory until 5 PM PDT Tuesday for PZZ350-356-370-
     376.

     Hazardous Seas Warning until 5 AM PDT Tuesday for PZZ376.

&&

$$