High Wind Watch 4, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
840 PM PDT THU SEP 26 2013

.DISCUSSION...SKY IS CLEARING ACROSS MOST OF THE FORECAST AREA
TONIGHT WITH THE EXCEPTION OF DOUGLAS COUNTY. WHERE THE SKY IS
PARTLY CLOUDY OR LESS..DEW POINTS ARE RUNNING ABOUT 3 DEGREES
LOWER THAN THE SAME TIME YESTERDAY. AS A RESULT EXPECT COLD NIGHT
FOR AREAS EAST OF THE CASCADES AND PART OF THE MOUNT SHASTA
CORRIDOR. ROGUE..APPLEGATE AND ILLINOIS VALLEYS CAN ALSO SEE
TEMPERATURES TONIGHT DROPPING INTO THE FROST POTENTIAL RANGE. HIGH
PRESSURE WILL KEEP THE AREA DRY FRIDAY BUT NEW MODEL SPEEDS UP
THE WARM FRONT INTO THE COASTAL WATERS FRIDAY AFTERNOON. WE COULD
SEE A FEW SPRINKLES AT THE COAST FRIDAY NIGHT. /FB

&&

.AVIATION...VFR CONDITIONS AREA-WIDE THIS EVENING. THERE ARE A FEW
STRAY LIGHT SHOWERS ROAMING AROUND BUT THOSE WILL DISSIPATE
QUICKLY AND REMAINING CUMULUS WILL ALSO DISSIPATE, LEAVING CLEAR
SKIES, BY LATE EVENING. WE MAY SEE SOME STRATUS WITH MVFR TO IFR
CIGS DEVELOP AT THE COAST AND IN THE UMPQUA LATE TONIGHT. PATCHY
STRATUS AND FOG IS POSSIBLE OVER INLAND VALLEYS AS WELL, BUT LESS
LIKELY. ANY STRATUS THAT DOES FORM WILL CLEAR OUT BY MID MORNING
FRIDAY, LEAVING VFR. WE WILL SEE INCREASING MID AND HIGH CLOUD
OVER THE NORTH COAST THROUGH THE DAY FRIDAY AND PERHAPS EVEN A
LITTLE LIGHT RAIN TOWARD DAY'S END AS A WARM FRONT APPROACHES.
-WRIGHT

&&

.PREV DISCUSSION... /ISSUED 144 PM PDT THU SEP 26 2013/

DISCUSSION...26/12Z NAM/GFS IN.

A BREAK BETWEEN SYSTEMS TODAY. WEAK LOW LEVEL OFFSHORE FLOW IS IN
PLACE...BUT IN SITU MOISTURE HAS MADE FOR LOTS OF CLOUD COVER OVER
THE AREA...BUT ANY SHOWERS EMBEDDED IN THE CLOUDS ARE VERY LIGHT...
AND MOSTLY FROM THE CASCADES EAST.

AN UPPER RIDGE IS NOW BUILDING INTO THE AREA WITH NORTHERLY FLOW
ALOFT. ONE LAST SHORT WAVE SLIDING DOWN THE BACKSIDE OF THE
DEPARTING TROUGH WILL MOVE THROUGH THE AREA TODAY...BUT IT WILL
BE OF LITTLE CONSEQUENCE AS IT IS A DRY "INSIDE SLIDER". THE MAIN
CONCERN IN THE NEAR TERM IS COLD OVERNIGHT TEMPERATURES. SEE THE
LIST BELOW FOR FROST AND FREEZE ADVISORIES AND WARNINGS CURRENTLY
IN EFFECT.

A SHORT WAVE RIDING OVER THE TOP OF THE RIDGE WILL MOVE ONSHORE
FRIDAY. ASSOCIATED PRECIPITATION WILL BE LIGHT AND LIMITED TO THE
COAST...COAST RANGE...AND UMPQUA BASIN. IT WILL JUST BRING SOME
CLOUDS TO PARTS OF THE REST OF THE AREA...AS THE ASSOCIATED ENERGY
WILL BE DIRECTED MOSTLY TO THE NORTH OF THE MEDFORD CWA. IT WILL
FLATTEN THE RIDGE OUT...SO FLOW ALOFT WILL GO ZONAL.

SATURDAY THROUGH MONDAY IS SHAPING UP TO BE A WET PERIOD WITH A
STRONG TROUGH SETTING UP OFFSHORE FOR THE WEEKEND BEFORE MOVING
ONSHORE MONDAY. TROPICAL MOISTURE FROM A DYING TYPHOON WILL GET
CAUGHT UP IN THIS SYSTEM BEFORE IT MOVES ONSHORE. DEBRIS FLOWS
IN BURNED AREAS WILL BE A CONCERN WITH THE COPIOUS AMOUNTS OF
PRECIPITATION ASSOCIATED WITH THIS SYSTEM. DUE TO THE TROPICAL
CONNECTION...SNOW LEVELS WILL BE HIGH AS WELL.

THE FIRST IMPULSE EJECTING FROM THIS TROUGH WILL MOVE ONSHORE
SATURDAY...BUT THIS WAVE WILL BE PRETTY WEAK...LIKE THE FRIDAY
SYSTEM...SO ANY ASSOCIATED PRECIPITATION WILL BE LIGHT AND
LIMITED TO THE COAST...COAST RANGE...AND UMPQUA BASIN.

THE NEXT MUCH STRONGER WAVE WILL MOVE ONSHORE SUNDAY. THIS WILL
PUSH A VERY WET FRONT ONSHORE SATURDAY NIGHT INTO SUNDAY
MORNING...WHICH WILL TAKE AROUND 24 HOURS TO PUSH THROUGH THE
ENTIRE CWA. EXPECT QUITE A BIT OF RAIN WITH THE FRONT AND MORE IN
POST-FRONTAL SHOWERS. AT THIS POINT THE MAIN CONCERN IS POSSIBLE
DEBRIS SLIDES NEAR BURN AREAS AND STRONG WINDS ALONG THE
COAST...OVER RIDGES...IN THE SHASTA VALLEY...AND EAST OF THE
CASCADES. WINDS MAY REACH HIGH WIND WARNING LEVELS EAST OF THE
CASCADES AND ADVISORY LEVELS IN THE SHASTA VALLEY. THERE IS A
LOWER CHANCE OF HIGH WINDS ALONG THE COAST BUT IT STILL MAY OCCUR.
FLOODING IS NOT LIKELY ANYWHERE DUE TO CURRENT LOW RIVER LEVELS AND
THE DEARTH OF SNOW AT HIGHER ALTITUDES TO MELT AND ADD TO THE
RUNOFF. RIVERS WILL RISE SIGNIFICANTLY THOUGH.

THE LONG WAVE TROUGH WILL KICK THROUGH THE PACIFIC NORTHWEST
MONDAY...AND SHOWERS WILL DIMINISH MONDAY EVENING. THERE WON'T BE
MUCH IN THE WAY OF RIDGING BEHIND THE TROUGH...JUST A TRANSITION
TO FAST ZONAL FLOW WITH THE STORM TRACK TO THE NORTH OF THE AREA.
THE GFS BRINGS THE NEXT UPSTREAM TROUGH ONSHORE WEDNESDAY. THE
ASSOCIATED FRONT WILL MOVE ONSHORE WEDNESDAY MORNING AND IT LOOKS
TO BE DRIER THAN THE SUNDAY SYSTEM...BUT STILL SIGNIFICANT.
MEANWHILE...THE EC GOES WITH A FARTHER NORTH STORM TRACK FOR THIS
TIME PERIOD WITH MOSTLY DRY CONDITIONS OVER SOUTHERN OREGON.

BOTH THE GFS AND EC BUILD A STRONGER OFFSHORE RIDGE INTO THE AREA
AFTER THE WEDNESDAY SYSTEM. POST-FRONTAL SHOWERS WILL END
WEDNESDAY EVENING AND THURSDAY AND FRIDAY LOOKS TO BE DRY WITH A
WARMING TREND.

AVIATION...BASED ON THE 26/18Z TAF CYCLE.

FAIR WEATHER CUMULUS ABOUND THIS AFTERNOON. PARTIAL MOUNTAIN
OBSCURATION EXIST OVER HIGHER TERRAIN...AND MOSTLY AROUND NORTH
FACING SLOPES. ANY CEILINGS THAT EXIST IN LOWER ELEVATIONS ARE VFR.
LATE TONIGHT...SOME CLEARING AND LINGERING MOISTURE WILL BRING THE
POTENTIAL FOR A PERIOD IFR TO LOW MVFR CEILINGS TO THE COAST AND
UMPQUA BASIN. ANY EARLY MORNING CEILINGS WILL LIFT AND CLEAR BY LATE
MORNING. SK

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FREEZE WARNING FROM 2 AM TO 9 AM PDT FRIDAY FOR ORZ029.
     FROST ADVISORY FROM 3 AM TO 8 AM PDT FRIDAY FOR ORZ024-026.

CA...FREEZE WARNING FROM 2 AM TO 9 AM PDT FRIDAY FOR CAZ084.
     FROST ADVISORY FROM 2 AM TO 9 AM PDT FRIDAY FOR CAZ081-082.
     FREEZE WARNING FROM 2 AM TO 9 AM PDT FRIDAY FOR CAZ081-082.

PACIFIC COASTAL WATERS...GALE WATCH FROM SATURDAY MORNING THROUGH SUNDAY AFTERNOON FOR
     PZZ370.
     HAZARDOUS SEAS WATCH FROM SATURDAY MORNING THROUGH TUESDAY
     AFTERNOON FOR PZZ370.
     GALE WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY AFTERNOON FOR
     PZZ350.
     HAZARDOUS SEAS WATCH FROM SATURDAY AFTERNOON THROUGH TUESDAY
     AFTERNOON FOR PZZ350.
     GALE WATCH FROM SATURDAY EVENING THROUGH SUNDAY EVENING FOR
     PZZ356-376.
     HAZARDOUS SEAS WATCH FROM SATURDAY EVENING THROUGH TUESDAY
     AFTERNOON FOR PZZ356-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 AM PDT FRIDAY
     FOR PZZ376.

FJB/FJB/TRW