Frost Advisory 61, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
902 AM PST MON DEC 2 2013

.SHORT TERM...A COLD FRONT IS LOCATED ACROSS THE NORTHERN PORTION
OF THE CWA AND WILL SHIFT SOUTH ACROSS THE AREA THIS MORNING AND
AFTERNOON, THEN MOVE SOUTH OF THE AREA IN THE EVENING. THIS FRONT
WILL BRING RAIN AND SNOW. MODELS REMAIN ON TRACK WITH SNOW LEVELS
LOWERING FROM NORTH TO SOUTH OVER THE AREA TODAY. CURRENTLY SNOW
LEVELS AROUND AT 5000 FEET OR HIGHER. HOWEVER SNOW LEVELS WILL
QUICKLY LOWER TO AROUND 2500 TO 3500 FEET IMMEDIATELY BEHIND THE
FRONT. SNOW ACCUMULATIONS ARE EXPECTED TO BE GREATEST WITH THIS
FRONT IN THE SOUTHERN OREGON CASCADES WHERE HIGHER PRECIPITATION
RATES WILL COMBINE WITH LOWERING SNOW LEVELS TODAY TO BRING
MODERATE SNOW, ESPECIALLY TO AREAS NEAR DIAMOND LAKE AND CRATER
LAKE. AREAS FURTHER SOUTH SUCH AS NEAR LAKE OF THE WOODS AND
SISKIYOU SUMMIT ARE EXPECTED TO INITIALLY HAVE RAIN, CHANGING TO
LIGHT SNOW DURING THE AFTERNOON. AREAS EAST OF THE CASCADES WILL
SEE MAINLY RAIN WITH SOME MOUNTAIN SNOW. IN THE AFTERNOON INTO
TONIGHT EXPECT SOME LIGHT SNOW  OVER EASTERN AREAS.

STRONG WESTERLY WINDS WILL CONTINUE AHEAD OF AND WITH THIS
FRONTAL PASSAGE OVER SOME HIGHER MOUNTAINS AND INTO THE SUMMER
LAKE AREA. WINDS IN THE SUMMER LAKE AREA ARE CURRENTLY GUSTING TO
AROUND 60 MPH. EXPECT THESE WINDS TO CONTINUE THIS MORNING THEN
DECREASE LATE THIS AFTERNOON AS THE 700 MB JET BEGINS TO SHIFT
SOUTH TO THE AREA.

SHOWERS ARE FORECAST BEHIND THE FRONT THIS EVENING AS MOIST WEST
TO NORTHWEST FLOW CONTINUES, MAINLY FROM THE CASCADES WEST IN
OREGON. ALSO EXPECT SHOWER INTO TONIGHT AS THE UPPER TROUGH AXIS
SHIFTS SOUTH INTO THE AREA. ON TUESDAY THESE SHOWERS WILL DIMINISH
ON THE WEST SIDE AS DRIER NORTH TO NORTHEAST FLOW DEVELOPS WITH
MAINLY ONLY ISOLATED SHOWERS CONTINUING OVER THE AREA, MAINLY IN
THE MOUNTAINS AND FROM THE CASCADES EAST.

OF CONCERN IS EXACT AMOUNT OF PRECIPITATION IN SHOWERS THIS
EVENING AND TONIGHT FROM THE CASCADES WEST. MODELS SHOW GOOD
AGREEMENT THAT THE SOUTHERN OREGON CASCADES AND FOOTHILLS MAY
RECEIVE AND INCH OR TWO OF SNOW ACCUMULATION, MAINLY FOR
ELEVATIONS ABOVE 2000 FEET. HAVE ADDED A SNOW ADVISORY TO ZONE 25
IN THE CASCADE FOOTHILLS FOR TONIGHT, WHICH INCLUDES AREAS AROUND
TOKETEE FALLS. SNOW LEVELS WILL LOWER TO 1000 TO 1500 FEET
TONIGHT. WESTERN VALLEYS WILL LIKELY SEE SOME SHOWERS THIS EVENING
AND TONIGHT BUT EXPECT SHOWER ACTIVITY TO BE LIGHT AND SCATTERED.
ALSO EXPECT LITTLE ACCUMULATION IN SHOWERS BELOW TO 2000 FEET DUE
TO THE LIGHT SNOW INTENSITY AND WARMER GROUND TEMPERATURES IN
THESE AREAS.

THIS UPPER TROUGH WILL BRING COLD TEMPERATURES TO THE AREA
BEGINNING TUESDAY WITH A COLD ARCTIC AIR MASS SETTLING OVER THE
REGION TUESDAY AND WEDNESDAY. THIS COLD AIR WILL LINGER THROUGH
THE END OF THE WEEK AND BRING WELL BELOW NORMAL TEMPERATURES.

LATE IN THE WEEK, OF CONCERN IS A MODERATE SHORTWAVE FORECAST TO
MOVE INTO THE AREA THURSDAY NIGHT THROUGH FRIDAY NIGHT.
PRECIPITATION FROM THIS SHORTWAVE ALONG WITH LINGERING AND
ADDITIONAL COLD TEMPERATURES MAY BRING ADDITIONAL SNOW TO THE
AREA, WITH SNOW ACCUMULATIONS POTENTIALLY DOWN TO LOWER VALLEY
FLOORS. CURRENTLY, JUST HAVE A SLIGHT CHANCE FOR PRECIPITATION IN
THE FORECAST BUT MAY NEED TO INCREASE THIS, GIVEN CURRENT MODEL
FORECASTS.

&&

.AVIATION...BASED ON THE 02/12Z TAF CYCLE.

A COLD FRONT IS PUSHING THROUGH THE AREA THIS MORNING...RESULTING IN
WIDESPREAD PRECIPITATION...GUSTY WINDS...AND MVFR/IFR CEILINGS AND
VISIBILITIES. THE FRONT IS FORECAST TO EXIT TO THE SOUTH LATE THIS
AFTERNOON. UNTIL THAT TIME...EXPECT LOWERED FLIGHT CONDITIONS AND
RAIN TO CONTINUE AT ALL TERMINALS WEST OF THE CASCADES...WITH
MOUNTAIN OBSCURATIONS AND STRONG WESTERLY LOW LEVEL WINDS. THE EAST
SIDE WILL SEE THE STRONGEST WESTERLY WINDS INTO THIS
AFTERNOON...WITH MOUNTAIN WAVE TURBULENCE AN ONGOING
CONCERN...AS EVIDENCED BY NUMEROUS PIREPS THUS FAR. FREEZING LEVELS
WILL DROP CONSIDERABLY WITH THE PASSAGE OF THE FRONT...REACHING TO
GROUND LEVEL AT ALL BUT THE LOWEST VALLEYS AND THE COAST BY TONIGHT.
ALTHOUGH CEILINGS MAY LIFT BRIEFLY AFTER FRONTAL PASSAGE...EXPECT
PRECIPITATION TO BECOME SHOWERY AND CHANGE TO SNOW IN MOST
AREAS...FURTHER REDUCING VISIBILITY. VFR CONDITIONS ARE NOT EXPECTED
DURING THE NEXT 24 HOURS.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WARNING UNTIL 4 PM PST THIS AFTERNOON FOR ORZ030-031.
     WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 4 AM PST
     TUESDAY ABOVE 2000 FEET FOR FOR ORZ025.
     WINTER WEATHER ADVISORY UNTIL 1 PM PST THIS AFTERNOON FOR
     ORZ027-028.

CA...HIGH WIND WARNING UNTIL 4 PM PST THIS AFTERNOON FOR CAZ085.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 7 AM PST TUESDAY
     FOR PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 7 AM PST TUESDAY
     FOR PZZ350.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 AM PST WEDNESDAY
     FOR PZZ370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 7 AM PST WEDNESDAY
     FOR PZZ376.

CC