Gale Watch 2, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
833 AM PST THU FEB 6 2014

.DISCUSSION...MORNING UPDATE. TEMPERATURES ARE IN THE MID 30S SOUTH
OF THE UMPQUA DIVIDE IN THE WEST SIDE VALLEYS. BUT WITH DEW POINTS
IN THE UPPER 20S THE PRECIP IS WET BULBING DOWN TO THE SURFACE AS
SNOW. HAVE UPDATED TO ACCOUNT FOR THIS.

.PREVIOUS DISCUSSION...A HELPFUL AND LONG OVERDUE PERIOD OF RAIN AND
SNOW WILL BEGIN TODAY AND CONTINUE AT LEAST INTO SUNDAY. A SHORTWAVE
RIDGE IS EXPECTED EARLY NEXT WEEK WITH A DECREASE IN ACTIVITY THEN
A NEW SERIES OF DISTURBANCES IS EXPECTED LATER TUESDAY THROUGH THE
REMAINDER OF NEXT WEEK.

THE MOST COMPLEX ASPECT OF THE FORECAST IS SNOW LEVELS WHILE THE
TIMING AND STRENGTH OF PRECIPITATION ALSO POSES A CHALLENGE. THE
FREEZING LEVEL FROM THE MFR SOUNDING AT 12Z/4 AM PST WAS 4900 FEET
WHICH TYPICALLY RESULTS IN A SNOW LEVEL AROUND 4000 FEET. BUT,
THERE ARE POCKETS OF MUCH COLDER AIR IN VALLEYS...ESPECIALLY NORTH
OF A STATIONARY FRONT...FROM THE UMPQUA VALLEY NORTHWARD INTO THE
WILLAMETTE VALLEY. IT IS ALSO COLD ENOUGH FOR SNOW IN THE ILLINOIS
VALLEY IN JOSEPHINE COUNTY. THOSE AREAS MAY INDEED RECEIVE A FEW
SNOW FLURRIES THIS MORNING AND SNOW HAS BEEN REPORTED AT MT SHASTA
CITY. BUT, THE MAIN ACTIVITY THIS MORNING WILL BE A GRADUAL
MOISTENING OF THE LOWER AND MID LEVELS OF THE AIR MASS...PRIMING
THE PUMP AHEAD OF A COLD FRONT THAT IS NOW OFFSHORE AROUND 129W.

SNOW LEVELS WILL RISE SLIGHTLY AHEAD OF THIS FRONT WITH AN AID
FROM DAY-TIME HEATING AND INCREASING SOUTHERLY WINDS. THERE WILL
STILL BE A WIDER THAN NORMAL DISPARITY IN SNOW LEVELS ACROSS OUR AREA
BUT THEY WILL GENERALLY RISE TO AROUND 2500 TO 3500 FEET AS
PRECIPITATION INTENSIFIES THIS AFTERNOON INTO THE EVENING. THE 00Z
NAM WAS THE WETTEST SOLUTION, WITH THE 00Z GFS AND ECMWF IN CLOSER
AGREEMENT WITH EACH OTHER. THE INHERITED FORECAST LOOKED LIKE IT
WAS STILL A REASONABLE BLEND OF ALL 3 SOLUTIONS, BUT THE FORECAST
WAS UPDATED IN ACCORDANCE WITH THE NEW DATA. THE MOST NOTABLE
SHORT TERM CHANGE WAS TO BUMP UP THE QPF, WHICH WAS ENOUGH TO
WARRANT ISSUING WINTER WEATHER ADVISORIES AT ELEVATIONS ABOVE 2500
FEET.

PRECIPITATION WILL LINGER LATE TONIGHT INTO FRIDAY MORNING THEN A
STRENGTHENING FRONT WILL ARRIVE FROM THE WEST ON FRIDAY. SNOW
LEVELS WILL RISE ON FRIDAY MORNING AHEAD OF THE FRONT, BUT THAT
WARMING WILL BE MUTED SOMEWHAT BY THE INTENSITY OF THE
PRECIPITATION WITH DOWNDRAFTS OF COLDER AIR. THUS, THERE IS STILL
UNCERTAINTY ON JUST HOW HIGH SNOW LEVELS WILL BE ABLE TO RISE. THE
FORECAST IS FOR THE SNOW LEVEL TO RISE TO AROUND 3500 FEET ON
FRIDAY THEN RISE FURTHER ON FRIDAY NIGHT INTO SATURDAY. RAIN AND
SNOW WITH THIS SECOND FRONT WILL BE MOST INTENSE DURING LATE
FRIDAY MORNING THROUGH FRIDAY EVENING. BOTH OF THESE STORMS WILL
AFFECT ALL OR NEARLY ALL OF THE AREA. BUT, WITH THE WESTERLY FLOW
ALOFT, PRECIPITATION AMOUNTS WILL BE HIGHER FROM THE CASCADES
WESTWARD.

A THIRD FRONT LOOKS TO BE AIMING FOR NORTHERN CALIFORNIA ON
SATURDAY INTO SUNDAY...FOCUSED ON THE REGION FROM EUREKA TO SAN
FRANCISCO AND EASTWARD TO THE SIERRA NEVADA. THERE IS MODEL
DISAGREEMENT ON JUST HOW MUCH PRECIPITATION WILL OCCUR FROM OUR
AREA NORTHWARD AND THUS ALSO JUST HOW HIGH SNOW LEVELS WILL RISE.
THERE IS CONFIDENCE THAT THEY WILL RISE ABOVE 4500 FEET. THE GFS
KEEPS MORE PRECIPITATION SOUTH OF OUR AREA WHILE THE 00Z ECMWF HAS
WIDER AND FARTHER NORTHWARD COVERAGE OF MODERATE PRECIPITATION.
THE ECMWF ALSO LINGERS PRECIPITATION LONGER...INTO SUNDAY NIGHT...
WHILE THE GFS SHOWS MUCH LESS ACTIVITY ON SUNDAY COMPARED TO
SATURDAY AND BEGINS THE PERIOD OF RIDGING ON SUNDAY NIGHT.

POPS WERE LOWERED SLIGHTLY FOR MONDAY INTO TUESDAY MORNING WITH
THE GFS AND ECMWF BOTH INDICATING ONLY A WEAK FRONT MOVING INTO
WASHINGTON AND NORTHERN OREGON OVER THE TOP OF A BUILDING RIDGE
OVER THE EASTERN PACIFIC. LIGHT RAIN MAY OCCUR DURING THAT TIME IN
COOS AND DOUGLAS COUNTIES.

THE STORM DOOR LOOKS TO SWING OPEN AGAIN TUESDAY WITH A NEW SERIES
OF MODERATE TO STRONG STORMS AND WARMER/HIGHER THAN NORMAL SNOW
LEVELS INTO THE END OF THE WEEK.

&&

.AVIATION...BASED ON THE 06/12Z TAF CYCLE.
A COOL, DRY AIR MASS REMAINS IN PLACE ACROSS THE REGION THIS
MORNING.
A LOW PRESSURE SYSTEM WILL APPROACH THE COAST THIS MORNING AND MOVE
ACROSS SOUTHWEST OREGON THIS AFTERNOON AND EVENING. THIS WILL SPREAD
PRECIPITATION ACROSS THE REGION THE REGION TODAY. WE MAY SEE A MIX
OF RAIN AND SNOW OR JUST SNOW BEGINNING ON THE WEST SIDE THIS
MORNING, THEN TRANSITIONING TO RAIN LATE MORNING AS SNOW LEVELS
RISE. IT WILL BE ALL SNOW IN THE MOUNTAINS AND EAST SIDE. CIGS AND
VIS SHOULD BE GENERALLY VFR THIS MORNING WITH LOCAL MVFR AT THE
COAST AND UMPQUA. CIGS AND VIS WILL DETERIORATE TO MVFR ALL AREAS
TODAY AS PRECIPITATION MOVES IN. LOCAL IFR IS POSSIBLE IN SNOW EAST
OF THE CASCADES THIS AFTERNOON AND EVENING. THE MOUNTAINS WILL BE
OBSCURED THROUGH TONIGHT AND MOUNTAIN WAVE TURBULENCE WILL INCREASE
ON THE EAST SIDE THIS EVENING AS THE LOW JUMPS THE CASCADES AND THE
FLOW BECOMES WESTERLY AT ALL LEVELS. -WRIGHT

&&

.MARINE...A SERIES OF LOW PRESSURE SYSTEMS WILL MOVE THROUGH THE
WATERS OVER THE NEXT SEVERAL DAYS. THE FIRST WILL MOVE THROUGH TODAY
AND WHILE WINDS WON'T BE PARTICULARLY STRONG, THEY WILL BE SHIFTING
AROUND TO THE SOUTH THIS MORNING AND THEN TO THE WEST THIS AFTERNOON
AS THE LOW MOVES INLAND. ANOTHER LOW COMES FROM THE SOUTHWEST FRIDAY
AND MOVES ACROSS THE WATERS. THIS WILL PRODUCE A PERIOD OF NEAR GALE
FORCE SOUTHERLIES OVER THE SOUTHERN WATERS, THEN WINDS SHIFT WEST
AGAIN. YET A THIRD LOW WILL MOVE BY TO THE NORTH ON SUNDAY. WINDS
WILL NOT BE VERY STRONG WITH THIS ONE BUT IT WILL BRING MORE RAIN
AND SHIFTING WINDS. THE STORM TRACK REMAINS AIMED AT OUR AREA INTO
NEXT WEEK AS WELL WITH ANOTHER STRONG LOW POSSIBLE ON TUESDAY WITH
SOUTHERLY GALES AND RAIN EXPECTED. -WRIGHT

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 4 AM PST
     FRIDAY FOR ORZ029>031.
     WINTER STORM WATCH FROM LATE TONIGHT THROUGH FRIDAY EVENING FOR
     ORZ029>031.
     WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 4 AM PST
     FRIDAY ABOVE 2500 FEET FOR FOR ORZ023>026.
     FREEZE WARNING UNTIL 8 AM PST THIS MORNING FOR ORZ021.
     WINTER STORM WATCH FROM LATE TONIGHT THROUGH FRIDAY EVENING
     ABOVE 2500 FEET FOR FOR ORZ024>026.
     WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 4 AM PST
     FRIDAY FOR ORZ027-028.
     WINTER STORM WATCH FROM LATE TONIGHT THROUGH FRIDAY EVENING FOR
     ORZ027-028.

CA...WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 4 AM PST
     FRIDAY FOR CAZ082-083-085.
     WINTER STORM WATCH FROM LATE TONIGHT THROUGH FRIDAY EVENING FOR
     CAZ082>085.
     WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 4 AM PST
     FRIDAY ABOVE 3000 FEET FOR FOR CAZ080-081.
     WINTER STORM WATCH FROM LATE TONIGHT THROUGH FRIDAY EVENING
     ABOVE 3000 FEET FOR FOR CAZ080-081.

PACIFIC COASTAL WATERS...NONE.

DW/TRW