Gale Watch 2, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
902 PM PST TUE FEB 12 2013

.DISCUSSION...JUST A MINOR UPDATE THIS EVENING TO INCREASE CLOUD
COVER TO REFLECT THE STRATUS THAT HAS ALREADY BEGUN TO FORM AND
FILL THE UMPQUA VALLEY AND SOUTHERN PORTIONS OF THE ROGUE VALLEY.

THE INITIAL ANALYSIS OF THE 00Z GFS AND 00Z NAM MODELS IS THAT
THEY SHOW QUITE A BIT OF CONSISTENCY WITH THE 12Z RUNS FROM THIS
MORNING. OVER THE NEXT FEW DAYS...A FEW WEAK DISTURBANCES WILL RIDE
OVER THE TOP OF THE UPPER LEVEL RIDGE. THERE IS A SLIGHT CHANCE OF
LIGHT SHOWERS BRUSHING NORTHERN COOS AND NORTHERN DOUGLAS COUNTIES.
BUT...MOST AND PERHAPS ALL OF THE RAIN WILL OCCUR NORTH OF OUR
AREA. BY THURSDAY...THE RIDGE WILL BUILD TOWARD THE COAST AND PUSH
THE SHORTWAVE TRACK FARTHER NORTH OF OUR AREA.

A WEAK COLD FRONT AND SUBSEQUENT SHORTWAVE IMPULSES WILL BRING A
CHANCE OF LIGHT RAIN...MAINLY NORTH OF THE UMPQUA DIVIDE SATURDAY
AND SATURDAY NIGHT. THE MORE SIGNIFICANT THING IS THAT THIS FRONT
WILL BEGIN A CHANGE IN THE UPPER LEVEL PATTERN. ANOTHER VERY WEAK
SHORTWAVE IS LIKELY TO BRUSH OUR NORTHERN AREAS SUNDAY THEN A
SHORT-LIVED PERIOD OF RIDGING IS LIKELY MONDAY. A COUPLE OF
NOTICEABLY COLDER AND WETTER FRONTS ARE EXPECTED TUESDAY AND
THURSDAY. BY THAT TIME...IT WILL HAVE BEEN JUST ABOUT THREE WEEKS
SINCE THE LAST FRONTAL SYSTEM OF SIMILAR STRENGTH AFFECTED OUR AREA.

&&

.AVIATION...STRATUS HAS FORMED AT THE COAST AND IS BEGINNING TO
EXPAND IN THE UMPQUA AND ROGUE VALLEYS AS WELL. STRATUS WILL
LIKELY LOWER AGAIN TONIGHT RESULTING IN WIDESPREAD IFR CIGS ACROSS
THE WEST SIDE AS WELL AS SOME BR/FG WITH IFR/LIFR VIS. THE EAST
SIDE OF OREGON AND ALL OF NORCAL REMAINS VFR AND WILL THROUGH
TONIGHT. WITH CONDITIONS VERY SIMILAR TO TODAY...I AM EXPECTING A
SIMILAR TIMING OF INLAND VALLEYS BREAKING OUT OF THE LOW MVFR TO
IFR CONDITIONS. -SVEN

&&

.PREV DISCUSSION... /ISSUED 201 PM PST TUE FEB 12 2013/

DISCUSSION...A WEAK AND NEARLY STATIONARY FRONTAL BOUNDARY IS
EXPECTED TO REMAIN NEAR OR JUST NORTH OF THE FORECAST AREA OVER THE
NEXT 30 TO 36 HOURS. THIS WILL MAKE FOR A TRICKY FORECAST MAINLY
NORTH OF THE UMPQUA DIVIDE AND NORTHERN CASCADES. GIVEN THAT THE
FRONT IS WEAK WITH NO STRONG FORCING...EXPECT ANY PRECIPITATION IN
THE ABOVE MENTIONED AREAS TO BE INTERMITTENT AND VERY LIGHT. MOST OF
THE ABOVE LOCATIONS PROBABLY WILL NOT HAVE ANY MEASURABLE
PRECIPITATION AND THUS THE REASON FOR LOW POPS AND SLIGHT CHANCE
MENTION. ALTHOUGH IT'S POSSIBLE A FEW LOCATIONS IN NORTHERN
COOS...NORTHWEST DOUGLAS COUNTY AND NORTH CASCADES COULD PICK UP
0.01 OF AN INCH.

THE AMOUNT OF CLOUD COVER WILL ALSO VARY TONIGHT THROUGH WEDNESDAY.
GENERALLY CLOUDS WILL BE MORE EXTENSIVE OVER THE NORTHERN PART OF
THE REGION WHERE IT WILL BE OVERCAST TO MOSTLY CLOUDY. IN CONTRAST
SKIES SHOULD BE PARTLY CLOUDY IN NORTHERN CALIFORNIA. THE ROGUE
VALLEY IS CLOSE TO THE DIVIDING LINE BETWEEN MOSTLY CLOUDY AND
PARTLY CLOUDY. MODELS SUGGEST THERE SHOULD BE SUFFICIENT LOW AND MID
LEVEL MOISTURE TONIGHT AND THURSDAY. THIS SHOULD LIMIT OR KEEP FOG
FROM DEVELOPING.

THE FRONTAL BOUNDARY IS EXPECTED TO LIFT NORTH AS THE UPPER RIDGE
STARTS TO NUDGE INTO SOUTHWEST OREGON ON THURSDAY. SO WERE LIKELY TO
BE DRY WITH LESS CLOUD COVER AND MILDER TEMPERATURES.

REGARDING THE AIR STAGNATION ADVISORY...THE MODELS INDICATE MIXING
HEIGHTS WILL BE AT OR ABOVE 200 FEET THE NEXT COUPLE OF DAYS WEST OF
THE CASCADES...THEREFORE WE'LL CANCEL THE AIR STAGNATION ADVISORY
FOR THE WESTSIDE. IT'S LESS CERTAIN MIXING HEIGHTS WILL BE HIGH
ENOUGH EAST OF THE CASCADES SO WE'LL LET IT CONTINUE.

A THERMAL TROF DEVELOPS THURSDAY NIGHT THROUGH FRIDAY WITH OFFSHORE
FLOW DEVELOPING. THIS WILL RESULT IN WARMER TEMPERATURES AT NIGHT
AND DURING THE DAY OVER THE RIDGES. THE OFFSHORE FLOW MAY BE
SUFFICIENT FOR A CHETCO EFFECT TO DEVELOP RESULTING IN WARMER
TEMPERATURES IN BROOKINGS. INVERSIONS ARE EXPECTED IN THE VALLEYS SO
MAX TEMPERATURES WILL BE COOLER. -PETRUCELLI

EXTENDED...(SATURDAY THROUGH TUESDAY)...WHILE THE INDIVIDUAL
ELEMENTS AND SOLUTIONS OF THE MODELS HAVE SHOWN VARIATION OVER TIME
OVER OUR AREA, THE MODEL TRENDS HAVE ALL BEEN TOWARD A PATTERN SHIFT
AWAY FROM A RIDGE-DOMINATED REGIME TO A MORE PROGRESSIVE AND WET ONE
STARTING NEXT WEEK. AT THIS TIME, THE MODELS HAVE COME INTO FAIRLY
GOOD AGREEMENT, AND THE OPERATIONAL RUNS ARE WELL SUPPORTED BY THE
ENSEMBLES, THUS THE CONFIDENCE IN THE EXTENDED FORECAST IS ABOVE
AVERAGE.

THE BIG RIDGE FINALLY GIVES WAY ON SATURDAY, AND THE FIRST IN A
SERIES OF SYSTEMS COMES ASHORE IN THE PACIFIC NW. THIS FIRST SYSTEM
LOSES SOME OF ITS ENERGY PROBABLY BY VIRTUE OF HAVING TO DISPLACE
THE RIDGE, AND THUS IT PROBABLY WON'T DO A LOT. BUT IT WILL BRING
RAIN TO THE COAST AND MUCH OF THE WEST SIDE, BUT IT'S LIKELY A
LITTLE TOO FAR NORTH TO BRING RAIN TO MEDFORD PROPER. SNOW LEVELS
WILL START OUT FAIRLY HIGH, ABOVE MOST PASS LEVELS, BUT THEY WILL
LOWER TO AS LOW AS 2000 FEET BY SATURDAY NIGHT. MOST OF THE
PRECIPITATION WILL FALL IN THE WARM SECTOR, SO AM NOT EXPECTING
IMPACTS FROM SNOW OVER THE WEEKEND. SHOWERS COULD LAST INTO SUNDAY,
BUT A TRANSITORY RIDGE WILL APPROACH SUNDAY, BRINGING AN END TO
PRECIP LATER SUNDAY, WITH MONDAY LIKELY BEING DRY.

THE NEXT SYSTEM MOVES IN MONDAY NIGHT AND TUESDAY AND LOOKS PRETTY
STRONG, WET, AND COLD. MODEL CONSISTENCY IS REMARKABLY GOOD FOR DAY
7 AND I FELT COMFORTABLE RAISING POPS QUITE A BIT, ESPECIALLY ON
THE WEST SIDE AND MOUNTAINS. SNOW LEVELS WILL START OUT AT ONLY
3000-4000 FEET ON MONDAY, AND THEN LOWER RAPIDLY AS THE SYSTEM COMES
IN. THIS SYSTEM HAS THE LOOK OF ONE WHICH WOULD PRODUCE IMPACTS FROM
SNOW IN THE MOUNTAINS. ALL INDICATIONS ARE THAT THE PATTERN WILL
REMAIN PROGRESSIVE OVER THE PACIFIC NW WITH ADDITIONAL SYSTEMS
POSSIBLE WELL INTO NEXT WEEK. -WRIGHT

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL 4 AM PST SATURDAY FOR ORZ029>031.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 AM PST
     FRIDAY FOR PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 AM PST FRIDAY
     FOR PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM PST THIS
     EVENING FOR PZZ356.

DW/SBN