Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 041027
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
327 AM PDT WED MAY 4 2016

.DISCUSSION...THE CLOSED LOW PRESSURE MAY STILL BE LOCATED OFF
CENTRAL CALIFORNIA COAST BUT ITS REACH WILL BE FELT INTO SOUTHERN
OREGON. THE ATMOSPHERE IS ALREADY UNSTABLE AND A FEW LIGHTNING
STRIKES HAVE BEEN OBSERVED IN DEL NORTE COUNTY. SHORT TERM MODEL
BRINGS A FEW STRIKES INTO THE KALMIOPSIS BY 0600 WITH
THUNDERSTORMSPOSSIBLE INTO THE ONION MOUNTAIN AREA. LIGHTNING
FREQUENCY SHOULD ONLY BE ISOLATED THIS MORNING.

ELSEWHERE ACROSS OUR FORECAST AREA...THE MOST UNSTABLE AREA WILL
BE FROM THE WEST SLOPE OF THE CASCADES EASTWARD. A SHORT WAVE
DISTURBANCE IS EXPECTED TO ROTATE NORTH INTO EASTERN SISKIYOU
COUNTY AND MODOC COUNTY THIS AFTERNOON AND CROSSING INTO KLAMATH
AND LAKE COUNTY TOWARD THE END OF THE DAY. WE COULD SEE QUITE AN
ACTIVE DAY TODAY. SATELLITE READING OF PRECIPITABLE WATER SHOWS
AROUND AN INCH FROM WESTERN DOUGLAS COUNTY SOUTH THROUGH JOSEPHINE
COUNTY AND THE TREND IS FOR MOISTURE TO EXPAND EAST. AS A RESULT
CONFIDENCE IS HIGH THAT WE WILL SEE MEASURABLE RAIN WITH THESE
SHOWERS AND THUNDERSTORMS...IN THE ORDER OF A TENTH TO A QUARTER.

ON THURSDAY THE CLOSED LOW IS FORECAST TO COME ASHORE OVER CENTRAL
CALIFORNIA. CONFIDENCE ON THE TRACK OF THIS LOW IS NOT VERY HIGH
DUE TO THE NATURE OF THE CLOSED LOW IN GENERAL. HOWEVER BOTH THE
NAM12 AND THE GFS20 ROTATE TWO MODERATELY STRONG SHORT WAVE
COUNTERCLOCKWISE FROM EAST TO WEST INTO OUR EAST SIDE ZONES. WITH
THE ATMOSPHERE REMAINING UNSTABLE INTO THURSDAY NIGHT...ANY STORMS
THAT MOVE INTO THE CASCADES COULD HOLD TOGETHER AND DRIFT INTO
JACKSON COUNTY. WHILE THIS IS A COMMON OCCURRENCE..THE THREAT IS
THERE AND WE HAVE EXPANDED THUNDERSTORM COVERAGE TO INCLUDE MOST
OF JACKSON COUNTY ON THURSDAY EVENING.

ON FRIDAY...MODELS PULLS THIS LOW FURTHER SOUTH. AT FIRST THIS
WOULD SEEM TO PULL INSTABILITY AREA SOUTH BUT SINCE CONFIDENCE ON
THE TRACK OF THIS LOW IS NOT VERY HIGH..WE HAVE KEPT SHOWERS AND
THUNDERSTORM CHANCES SIMILAR TO THURSDAY. THE EXCEPTION IS THE
COAST AND MOST OF THE UMPQUA VALLEY AND NW JOSEPHINE COUNTY WHERE
THE ATMOSPHERE SHOULD BE LESS UNSTABLE FOR ONLY SHOWER COVERAGE.

SOUTHWEST OREGON AND PART OF THE KLAMATH BASIN SHOULD BE DRY ON
SATURDAY AS THE LOW MOVES OUT OF THE AREA. WRAPPED AROUND MOISTURE
COULD KEEP SHOWERS AND THUNDERSTORM CHANCE IN EASTERN
SISKIYOU..MODOC AND LAKE COUNTIES. BY SUNDAY THE ONLY THREAT OF
THUNDERSTORMS SHOULD BE TO THE RIGHT OF THE LINE FROM MOUNT SHASTA
TO LAKEVIEW. /FB


&&

.AVIATION...FOR THE 04/06Z TAF CYCLE...ALONG THE COAST...MVFR CIGS
WITH AREAS OF IFR CIGS ARE EXPECTED TO PERSIST INTO WEDNESDAY
EVENING WITH ISOLATED TO SCATTERED SHOWERS. INLAND...SCATTERED
SHOWERS ARE EXPECTED THROUGH THE MORNING WITH MAINLY VFR CIGS AND
LOCAL MVFR CIGS AND TERRAIN OBSCURATIONS. MVFR CIGS ARE EXPECTED TO
BE LIKELY IN THE UMPQUA VALLEY TONIGHT INTO WEDNESDAY. FOR INLAND
AREAS, WEDNESDAY AFTERNOON AND EVENING, EXPECT NUMEROUS SHOWERS WITH
ISOLATED TO SCATTERED THUNDERSTORMS. THIS WILL RESULT IN ISOLATED TO
AREAS OF MVFR CIGS ALONG WITH AREAS OF MOUNTAIN OBSCURATIONS DURING
THE AFTERNOON AND EVENING. /CC


&&

.MARINE...UPDATED 200 AM PDT WED 4 MAY 2016...OFFSHORE HIGH
PRESSURE AND INLAND LOW PRESSURE WILL PRODUCE PERSISTENT GUSTY
NORTHERLY WINDS AND STEEP TO VERY STEEP SEAS THROUGH FRIDAY
EVENING...WEAKENING SLIGHTLY THIS WEEKEND. THE STRONGEST WINDS AND
HEAVIEST SEAS WILL OCCUR OVER THE OUTER WATERS SOUTH OF CAPE BLANCO.

MODIFICATIONS TO THE WARNINGS AND ADVISORIES THIS MORNING WERE
DRIVEN PRIMARILY BY A LARGER AREAS OF HAZARDOUS SEAS THAN PREVIOUSLY
FORECAST.


&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 11 PM PDT FRIDAY FOR PZZ350-356.
     HAZARDOUS SEAS WARNING FROM 11 AM THIS MORNING TO 11 PM PDT
     FRIDAY FOR PZZ350-356-370-376.
     GALE WARNING FROM 11 AM THIS MORNING TO 11 PM PDT FRIDAY FOR
     PZZ356-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM PDT THIS
     MORNING FOR PZZ350-356-376.
     SMALL CRAFT ADVISORY UNTIL 11 AM PDT THIS MORNING FOR
     PZZ370-376.

$$

FJB/FJB/JRS


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