Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 211723

Area Forecast Discussion
National Weather Service Medford OR
923 AM PST Tue Nov 21 2017

.DISCUSSION...Most, if not all of the significant rainfall has
shifted north of the area this morning. The radar is still picking
up on some light returns, so still cannot rule out a off/on light
rain the rest of the morning. This afternoon odds are we`ll see
more dry time than not. Still a shower or two could not be ruled
out. Made some adjustments to the forecast to reflect this and
have adjusted pops and rainfall amounts lower for this afternoon.
An upper ridge centered in southern California should be strong
enough to deflect most of the rainfall north of our area the rest
of today through tonight. However occasional rain is still
expected along the coast and northwest Douglas County.

Snow levels will remain high for the rest of the week. This will
be good news for those who plan on traveling today or tomorrow.


.PREV DISCUSSION... /Issued 420 AM PST Tue Nov 21 2017/

DISCUSSION...The warm frontal precip has moved to the north of
the region. The cold front approaches the coast this afternoon,
with winds increasing through the day. The pressure gradient in
the Shasta valley continues to indicate advisory winds later this
morning into the evening, and strong southwest 700 mb winds over
the east side should bring winds at the higher elevations up to
advisory strength. With the strong southerly flow up the Shasta
Valley spilling down into the Rogue valley temperatures taken
down dry adiabatically from 850 mb would indicate high
temperatures in the upper 60s. However, the low fog and stratus
underneath the strong surface inversion will slow the heating and
the decoupled flow aloft will take a while to finally reach the
surface and have hedged down the high temperatures a bit to
account for this. if the skies clear and winds mix down by mid to
late morning, then we could see a high temperature near 70 this
afternoon at the Medford airport. The front stalls offshore and
the bulk of the precip falls near the coast as this system is
shunted the north as it hits the upper level ridge over the Pac

With a strong atmospheric river event indicated precip will
continue on and off near the coast ahead of the next system that
moves in Wednesday. This front will bring precip much farther
inland as the upper level ridge shifts to the east and flattens
as we head towards the end of the week, bringing precip across the
east side into Friday morning. This active pattern remains and
intensifies through the weekend as an upper level trough moves
through, with snow level remaining high until Monday when a cooler
air mass moves in behind a front Monday. Sven

AVIATION...21/12Z TAF CYCLE... A warm frontal wave moving across
the forecast area from the south tonight will continue to bring
CIG/VIS reductions through this morning, but winds will also be
increasing aloft. This will result in concerns for low level wind
shear at all TAF sites centered on, but not confined to, this
morning. Most valley locations will experience IFR to MVFR
conditions early morning, but local VFR and LIFR will also occur
due to fluctuations in wind and precipitation. Expect widespread
mountain obscurations decreasing this afternoon, and then
increasing again in the evening. Tuesday afternoon ceilings and
visibilities are expected to improve to VFR at all valley
locations. This evening the next frontal wave is likely to bring
another round of deteriorating conditions to the Coastal Mountains
westward. BTL/Sven

MARINE...Updated 300 AM PST Tuesday, 21 November 2017...
A prolonged period of advisory to gale force southerly winds and
building seas is expected today into Thursday yielding steep to very
steep seas. Remaining northwest swell and southerly fresh swell from
yesterday`s frontal system will combine with south wind seas to
result in very steep and chaotic seas over much of the area. South
winds are likely to peak around midday today, and seas are expected
to peak this evening through Wednesday morning. Seas will then
remain hazardous into Thursday. A brief break is expected Friday
before the next frontal system arrives this weekend. BTL/Spilde


OR...Wind Advisory until 10 PM PST this evening for ORZ030-031.

CA...Wind Advisory until 10 PM PST this evening for CAZ085.
     Wind Advisory until 10 PM PST this evening for CAZ081.

Pacific Coastal Waters...Small Craft Advisory until 4 AM PST Wednesday for
     Gale Warning until 4 AM PST Wednesday for PZZ350-356-370-376.

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