Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 111016
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
216 AM PST THU FEB 11 2016

.SHORT TERM...A SHORTWAVE RIDING UP THROUGH THE SOUTHWEST FLOW
ALOFT HAS KICKED OFF A FEW SHOWERS OVER OUR AREA THIS MORNING. NO
RAIN HAS HIT ANY OF THE OBSERVING SITES YET, BUT RADAR SHOWS
ISOLATED SHOWERS DRIFTING THROUGH RIGHT NOW. SHOWER COVERAGE WILL
INCREASE THIS MORNING AS THE MAIN PART OF THE SHORTWAVE ARRIVES,
AND RADAR IS SHOWING A LOT MORE SHOWERS OFF THE NW CALIFORNIA
COAST MOVING OUR WAY. MODELS SHOW THESE SHOWERS BEING CONFINED
MOSTLY TO THE CASCADE CREST AND WEST SIDE, BUT SOME SHOWERS
CERTAINLY COULD DRIFT OVER ONTO THE EAST SIDE. POPS HAVE BEEN
RAISED THIS MORNING.

WE WILL PROBABLY SEE AT LEAST SOME LINGERING SHOWERS THIS
AFTERNOON AND EVENING AS A WEAK COLD FRONT APPROACHES. THIS COLD
FRONT WILL MOVE ONSHORE TONIGHT AND FRIDAY MORNING AND BRING LIGHT
RAIN TO MOST WEST SIDE LOCATIONS AS IT MOVES INLAND FRIDAY. WE`RE
NOT EXPECTING A LOT OF RAIN WITH VALLEY LOCATIONS PROBABLY ONLY
SEEING A FEW HUNDREDTHS OF RAIN. HOWEVER, MOUNTAIN LOCATIONS COULD
SEE UP TO A QUARTER OF AN INCH OF RAIN. SNOW LEVELS WILL BE HIGH
(ABOVE 8000 FEET MOST OF THE DAY), SO IT WILL BE RAIN EXCEPT AT
THE HIGHEST PEAKS. SNOW MAY MAKE IT DOWN TO CRATER LAKE AND MT
ASHLAND BY DAY`S END, BUT MOST OF THE PRECIPITATION WILL HAVE
ALREADY FALLEN BY THEN. POPS WERE RAISED TO AT LEAST LIKELY ON THE
WEST SIDE FOR FRIDAY.

SATURDAY SHOULD BE A BIT OF A BREAK WITH LEFTOVER MORNING SHOWERS
OVER THE NORTH DECREASING THROUGH THE DAY. ELSEWHERE, THE DAY
OUGHT TO BE DRY. THE PREVIOUS SHIFT`S THINKING REGARDING SUNDAY`S
SYSTEM STILL LOOKS REASONABLE AND THE PREVIOUS LONG TERM
DISCUSSION FOLLOWS. THE ONE CHANGE MADE TO THE EXTENDED FORECAST
THIS MORNING WAS TO RAISE POPS ON SUNDAY. -WRIGHT

.LONG TERM...SUNDAY THROUGH WEDNESDAY...A WARM FRONT WITH GOOD
ISENTROPIC ASCENT WILL RIDE OVER THE TOP OF A FLAT RIDGE ON
SUNDAY. THIS COMBINED WITH DEEP ONSHORE WEST-NORTHWEST FLOW WILL
RESULT IN RAIN, FOCUSED ON NORTH AND WEST FACING TERRAIN ALONG
AND WEST OF THE CASCADES WITH LIGHTER RAIN IN THE VALLEYS. RAIN
CHANCES DIMINISH SOUTH AND EAST OF THE MOUNTAINS. SNOW LEVELS WILL
BE WELL ABOVE THE MAJOR PASSES AND LIKELY ABOVE 8000 FEET IN MOST
AREAS. THE WARM FRONT WILL SHIFT NORTHWARD IN THE AFTERNOON AND
ISENTROPIC LIFT WILL EASE...EFFECTIVELY SHUTTING OFF RAINFALL
FROM SOUTH TO NORTH ACROSS THE CWA LATE SUNDAY AFTERNOON AND
NIGHT.

MODELS INDICATE THE RIDGE WILL STRENGTHEN A BIT OVER THE AREA
MONDAY WITH MOST, IF NOT ALL PRECIPITATION REMAINING TO THE
NORTH OF THE CWA. MODELS DIFFER A BIT WITH RESPECT TO ANOTHER
SHORTWAVE RIDING OVER THE RIDGE MONDAY NIGHT INTO TUESDAY. THE GFS
KEEPS IT WAY TO THE NORTH WHERE IT WOULD HAVE NO IMPACT ON OUR
WEATHER. THE ECMWF THOUGH HAS IT FARTHER SOUTH. DUE TO THE
UNCERTAINTY, WE HAVE INDICATED SLIGHT CHANCE TO CHANCE POPS FROM
THE COAST TO THE CASCADES AND NORTH OF THE UMPQUA DIVIDE. IT
SHOULD STAY DRY IN THE ROGUE VALLEY.

CONFIDENCE IS FAIRLY HIGH THAT THE NEXT SIGNIFICANT UPPER TROUGH
TO IMPACT THE AREA WILL ARRIVE TUESDAY NIGHT INTO WEDNESDAY. THE
SURFACE COLD FRONT WILL BE JUST OFFSHORE LATE TUESDAY NIGHT, THEN
MOVE ACROSS THE AREA WEDNESDAY INTO WEDNESDAY NIGHT. RAIN IS
LIKELY FROM THE COAST TO THE CASCADES WITH HIGH CHANCES EVEN OVER
THE EAST SIDE. SNOW LEVELS START OUT HIGH AHEAD OF THE FRONT, BUT
COULD DROP DOWN TO 3000 FEET BEHIND THE FRONT BY THURSDAY MORNING.
-SPILDE

&&

.AVIATION...FOR THE 11/06Z TAF CYCLE...VFR CONDITIONS WILL PREVAIL
INTO THURSDAY EVENING THOUGH WITH VFR CEILINGS THROUGH THURSDAY
MORNING. THROUGH THE MORNING THERE WILL ALSO BE LOCAL MVFR
CIGS/VSBYS IN LIGHT RAIN OR DRIZZLE WITH HIGHER TERRAIN OBSCURED
NEAR THE COAST AND IN THE COAST RANGE. -DW

&&

.MARINE...UPDATED 1000 PM PST WED FEB 10 2016...MODERATE LONG
PERIOD WEST SWELL WILL BECOME HIGH THURSDAY EVENING AND INCREASE
INTO EARLY FRIDAY THEN REMAIN HIGH BUT STEEPEN INTO SUNDAY. A WEAK
COLD FRONT WILL MOVE ONSHORE THURSDAY NIGHT THEN ANOTHER WEAK
FRONT WILL MOVE ONSHORE FRIDAY NIGHT. A STRONGER FRONT WILL MOVE
ONSHORE SATURDAY NIGHT INTO SUNDAY. OFFSHORE HIGH PRESSURE WILL
BUILD EARLY NEXT WEEK. -DW

&&

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

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS
     UNTIL 10 PM PST SUNDAY FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 4 AM PST
     FRIDAY FOR PZZ370-376.

$$


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