Hazardous Seas Warning 9, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
902 PM PDT THU APR 4 2013

.DISCUSSION...RAIN SHOWERS CONTINUE INTO THIS EVENING. THE
ATMOSPHERE CONTINUES TO BE UNSTABLE AND A FEW LIGHTNING STRIKES
PERSIST INTO LATE EVENING. HAVE UPDATED THE GRIDS TO EXTEND
ISOLATED THUNDERSTORM TO 06Z. RAIN SHOWERS COVERAGE WAS LESS THAN
EXPECTED AND HAVE ALSO UPDATED POPS DOWNWARD IN THE ROGUE VALLEY
AND SHASTA VALLEY WHERE GROUND TRUTH INDICATES VERY LITTLE
RAINFALL WITH PLENTY OF VIRGA.

THE LATEST GUIDANCE CONTINUES TO SHOW THE LONG WAVE TROUGH JUST
OFFSHORE SENDING A SERIES OF SHORTWAVES INLAND. COOL AND UNSETTLED
WEATHER CONTINUES INTO THE WEEKEND. /FB

&&

.AVIATION...SHOWERS BEHIND A COLD FRONT WILL CONTINUE THROUGH THE
EVENING AND OVERNIGHT MOST PLACES. A FEW THUNDERSTORMS ARE
POSSIBLE THIS EVENING BUT THUNDERSTORMS ARE NOT EXPECTED AFTER
MIDNIGHT. MOUNTAIN OBSCURATION WILL CONTINUE THROUGHOUT THE
FORECAST AREA WITH PLENTY OF LOW LEVEL MOISTURE. A MIX OF MVFR AND
IFR CONDITIONS WILL CONTINUE OVERNIGHT FOR THE UMPQUA
BASIN...ILLINOIS VALLEY AND COAST...WHILE FURTHER INLAND VALLEYS
AND THE EAST SIDE SHOULD CONTINUE TO HAVE MOSTLY VFR CONDITIONS.
FREEZING LEVELS WILL CONTINUE TO TREND DOWNWARDS OVER THE NEXT
COUPLE DAYS AS MORE COLD FRONTS PASS THROUGH THE AREA.

&&

.PREV DISCUSSION... /ISSUED 130 PM PDT THU APR 4 2013/

DISCUSSION...04/12Z NAM/GFS IN.

THE TRANSITION TO A WET PATTERN IS NOW OCCURRING. SIGNIFICANT
PRECIPITATION HAS BEEN REPORTED ALONG THE COAST...COAST
RANGE...AND IN THE UMPQUA AND ILLINOIS VALLEYS. IT IS ALSO RAINING
OVER WESTERN AND SOUTH CENTRAL SISKIYOU COUNTY. A FEW LOCATIONS
EAST OF THE CASCADES ARE ALSO REPORTING PRECIPITATION.

THE PRECIPITATION IS ASSOCIATED WITH A SHORT WAVE WHICH WAS
EJECTED FROM AN OFFSHORE LONG WAVE TROUGH. THIS WAVE IS PUSHING A
WEAK FRONT THROUGH THE AREA AT THIS TIME. EXPECT THE RAIN TO SPREAD
OVER THE REST OF THE CWA THIS AFTERNOON WITH SNOW LEVELS BETWEEN
7000 AND 8000 FEET. INCREASING INSTABILITY WILL MAKE FOR LOTS OF
SHOWERS AND MAYBE A THUNDERSTORM THIS AFTERNOON AND EVENING. IT
WILL ALSO BE BREEZY OVER THE COAST AND COASTAL WATERS...IN THE
SHASTA VALLEY...AND EAST OF THE CASCADES.

THE LONG WAVE TROUGH WILL WEAKEN AND MOVE ONSHORE TONIGHT...
SUPPORTING CONTINUED SHOWER ACTIVITY INTO TONIGHT. SNOW LEVELS
WILL DROP TO 5000 TO 6000 FEET LATE TONIGHT...STILL ABOVE PASS
LEVELS.

ANOTHER LONG WAVE TROUGH WILL REPLACE THE CURRENT ONE FRIDAY AND
THIS ONE WILL CONTINUE TO EJECT SHORT WAVES OVER THE PACIFIC
NORTHWEST BEGINNING FRIDAY EVENING. THEREFORE...THE RELATIVE BREAK
LATE TONIGHT INTO FRIDAY MORNING WILL BE BRIEF. A WARM FRONT WILL
MOVE THROUGH THE AREA FRIDAY AFTERNOON AND EVENING...FOLLOWED BY
THE TRAILING COLD FRONT FRIDAY NIGHT. SNOW LEVELS BEHIND THE FRONT
WILL DROP TO AROUND 4000 FEET OVER THE NORTHWEST PORTIONS OF THE
FORECAST AREA...MOSTLY COOS AND DOUGLAS COUNTIES...BUT THE COLDEST
AIR WILL NOT PENETRATE FARTHER INLAND.

THE MEDFORD CWA WILL REMAIN UNDER THE STORM TRACK THROUGH THE
WEEKEND...WITH SUBSEQUENT SHORT WAVES DRIVING WARM FRONTS FOLLOWED
BY COLD FRONTS THROUGH THE AREA. THESE SYSTEMS WILL BE SPACED
CLOSELY SUCH THAT IT WILL BE DIFFICULT TO TELL WHEN ONE ENDS AND
THE NEXT BEGINS. SNOW LEVELS WILL REMAIN IN THE 4000 TO 6000 FOOT
RANGE INTO MONDAY MORNING.

EXTENDED DISCUSSION...MONDAY THROUGH THURSDAY. THE EC AND GFS ARE
IN FAIRLY GOOD AGREEMENT MONDAY AND TUESDAY...THEN DIVERGE FROM
WEDNESDAY INTO THE END OF NEXT WEEK. MONDAY WILL BE A TRANSITION
DAY WITH THE UPPER TROF EXITING OUT OF THE FORECAST AREA AND AN
UPPER RIDGE BUILDING IN FROM THE WEST. THE RIDGE AXIS MOVES
OVERHEAD TUESDAY. AFTER TUESDAY...THE EC SHOWS THE RIDGE
FLATTENING OUT FOLLOWED BY A STRONGER SHORTWAVE WEDNESDAY NIGHT
THROUGH THURSDAY WITH THE MEAN RIDGE RETROGRADING TOWARDS 150W. IN
CONTRAST...THE GFS FLATTENS OUT THE RIDGE...BUT KEEPS THE STORM
TRACK MAINLY NORTH OF THE FORECAST AREA DURING THE SAME TIME
PERIOD. GIVEN THE STRENGTH OF THE RIDGE...SUSPECT THE GFS SOLUTION
IS ON THE RIGHT TRACK AND THE EXTENDED FORECAST WILL LEAN IN THAT
DIRECTION. SO IN SUMMARY KEPT THE HIGHEST POPS IN THE NORTHWEST
PART OF THE CWA...BUT KEPT THEM BELOW CLIMO. -PETRUCELLI

AVIATION...A COLD FRONT MOVING INTO THE AREA WILL BRING A CHANCE
FOR WIND SPEED SHEAR IN THE UMPQUA BASIN UNTIL 22Z. MVFR CIGS ARE
EXPECTED TO PERSIST ALONG THE COAST THROUGH THIS EVENING. HOWEVER
THERE IS A CHANCE BRIEF VFR CIGS TO DEVELOP BETWEEN 21-23Z.
ELSEWHERE VFR CONDITIONS ARE EXPECTED THROUGH THIS EVENING WITH
BRIEF MVFR CIGS IN SHOWERS LATE THIS AFTERNOON AND TONIGHT WITH
PARTIAL MOUNTAIN OBSCURATION. THE EXCEPTION WILL BE THE UMPQUA
BASIN WHERE IT'S MORE LIKELY MVFR WITH OCCASIONAL IFR CONDITIONS
DEVELOP TONIGHT. SOME TURBULENCE IS EXPECTED ALONG AND EAST OF THE
CASCADES AND SISKIYOUS.

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS FROM 11 AM FRIDAY TO 5 AM PDT
     SATURDAY FOR PZZ350-356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM PDT MONDAY
     FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR WINDS FROM 11 AM FRIDAY TO 2 AM PDT
     SATURDAY FOR PZZ370.
     SMALL CRAFT ADVISORY FOR WINDS FROM 11 AM FRIDAY TO 5 AM PDT
     SATURDAY FOR PZZ376.

FJB/DW/FJB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEDFORD OR
1122 PM PDT THU APR 4 2013

...TIME...  ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
...DATE...  ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1122 PM     HEAVY RAIN       2 SSW OBRIEN            42.05N 123.71W
04/04/2013  M1.02 INCH       JOSEPHINE          OR   TRAINED SPOTTER

            HEAVY RAIN DURATION 24 HOURS

&&

IRIS SYSTEM