Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 260301
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
801 PM PDT MON MAY 25 2015

.DISCUSSION...26/00Z NAM IN.

SOME THUNDERSTORMS DEVELOPED MONDAY AFTERNOON OVER SOUTHEAST
SISKIYOU AND SOUTHERN MODOC COUNTIES. THOSE ARE NOW DISSIPATING
WITH ONE LAST THUNDERSTORM LINGERING OVER SOUTHWEST MODOC COUNTY.
LIGHT SHOWERS WILL PERSIST A BIT LONGER.

THE SYNOPTIC PATTERN OVER THE WEST COAST REMAINS BLOCKY THIS
EVENING. CURRENTLY A WEAK REX BLOCK IS IN PLACE WITH THE RIDGE
OVER THE YUKON TERRITORY AND THE LOW ALONG THE BRITISH COLUMBIA
AND WASHINGTON STATE BOUNDARY. THE PATTERN WILL BE SIMILAR TUESDAY
WITH THE LOW JUST A BIT FARTHER EAST. DRY NORTHERLY FLOW ALOFT
WILL KEEP MOST OF THE MEDFORD CWA WARM AND DRY...BUT THE FLOW OVER
NORTHERN CALIFORNIA IS MORE WESTERLY...ALLOWING SOME MOISTURE IN.
EXPECT SHOWER AND THUNDERSTORM LOCATION AND COVERAGE TO BE
SIMILAR TO MONDAY...BUT MODEL LIFTED INDICES INDICATE THEY WILL
NOT BE AS STRONG.

THE LOW WILL MOVE OUT EAST WEDNESDAY AND DRY NORTHWEST FLOW WILL
SET UP OVER THE CWA. MODEL LIFTED INDICES SHOW DRY CONDITIONS
OVER THE AREA AS THE BEST INSTABILITY SETS UP SOUTH OF THE CWA.
THE LOW WILL BE REPLACED BY ANOTHER LOW FARTHER NORTH AS THE
BLOCKING HIGH PERSISTS IN THE SAME LOCATION.

THE OFFSHORE RIDGE WILL BUILD IN MORE STRONGLY THURSDAY. DRY
CONDITIONS WILL CONTINUE WITH A WARMING TREND...AND MEDFORD MAY
SEE THE FIRST 90 DEGREE DAY OF THE YEAR.

LONG TERM DISCUSSION FROM THE MONDAY AFTERNOON AFD...FRIDAY
THROUGH MONDAY...THE STRONG RIDGE WILL PERSIST OVER CALIFORNIA ON
FRIDAY WHILE A TROUGH MOVES INTO BRITISH COLUMBIA. THIS WILL BRING
A MODEST INCREASE OF 700-500 MB MOISTURE WHILE HIGH TEMPERATURES
WILL AGAIN BE MUCH ABOVE NORMAL...ABOUT THE SAME AS ON THURSDAY.
THIS WARRANTS INCLUDING A SLIGHT CHANCE OF AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS FROM THE SISKIYOU AND CASCADE MOUNTAINS
EASTWARD WITH THE STRONGEST LIFT LIKELY EAST OF THE KLAMATH BASIN.
LITTLE CHANGE IS EXPECTED ON SATURDAY. THE REGION OF FOCUS FOR
THUNDERSTORM ACTIVITY WILL DEPEND LARGELY UPON THE POSITIONING OF
THE TWO MAIN UPPER LEVEL FEATURES. THE 700MB STEERING FLOW WILL
LIKELY BE FROM THE SOUTH OR SOUTHWEST.

MODEL DIFFERENCES INCREASE BY SUNDAY. ANOTHER TROUGH WILL BE
APPROACHING OUR COAST FROM THE WEST OR SOUTHWEST. THE POSITION OF
THIS LOW IS UNCERTAIN. IF IT IS FASTER/MORE PROGRESSIVE, WHICH IS
CLOSER TO THE GFS SOLUTION, THEN SOUTHERLY FLOW ALOFT AND
INSTABILITY ARE LIKELY TO BE ENHANCED ON SUNDAY. BUT, THERE IS ABOUT
AN EQUAL PROBABILITY THAT RIDGING WILL STRENGTHEN ON SUNDAY AND LEAD
TO A LOWER PROBABILITY OF SHOWERS AND THUNDERSTORMS THAN ON
SATURDAY. BY MONDAY, IT IS MORE LIKELY THAT THE LOW WILL BE
SUFFICIENTLY NEAR OUR REGION TO BRING AN INCREASE OF CLOUDS, LOWER
TEMPERATURES AND A MORE WIDESPREAD SLIGHT CHANCE TO CHANCE OF
SHOWERS AND THUNDERSTORMS. THE EARLY OUTLOOK IS FOR HOT AND DRY
WEATHER TO FOLLOW ON DAY 8 THROUGH 10.

&&

.AVIATION...FOR THE 26/00Z TAF CYCLE...ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS OVER SISKIYOU AND MODOC COUNTIES IS NOW DIMINISHING
WHILE AREAS OF IFR CIGS REDEVELOP ALONG THE COAST. A MIX OF IFR AND
MVFR STRATUS WILL SURGE INTO THE COASTAL AND UMPQUA VALLEYS
OVERNIGHT THEN PERSIST UNTIL AROUND 18Z TUESDAY MORNING. THUNDERSTORMS
COULD DEVELOP AGAIN TUESDAY AFTERNOON OVER SISKIYOU AND MODOC
COUNTIES. MND/DW

&&

.MARINE...UPDATED 300 PM PDT MONDAY 25 MAY 2015...HIGH PRESSURE
OFFSHORE AND A THERMAL TROUGH NEAR THE COAST WILL PEAK IN STRENGTH
MONDAY EVENING...THEN GRADUALLY WEAKEN MONDAY NIGHT THROUGH
THURSDAY. THIS WILL CREATE MODERATE TO STRONG NORTHERLY WINDS OVER
THE WATERS RESULTING STEEP TO VERY STEEP WIND DRIVEN SEAS THROUGH
MONDAY EVENING, ESPECIALLY IN THE VICINITY OF CAPE BLANCO AND
SOUTH. WINDS WILL WEAKEN AS THE PRESSURE PATTERN WEAKENS, HOWEVER
NORTH WINDS WILL CONTINUE TO BE GUSTY IN THE AFTERNOONS AND
EVENINGS KEEPING SMALL CRAFT CONDITIONS GOING THROUGH THE
WEEK...MOSTLY IN THE SOUTHERN OUTER WATERS. -MND

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM
        PDT THIS EVENING FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 AM PDT THURSDAY
        FOR PZZ356-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THIS
        EVENING FOR PZZ350-370.
     GALE WARNING UNTIL 11 PM PDT THIS EVENING FOR PZZ376.
     HAZARDOUS SEAS WARNING UNTIL 11 PM PDT THIS EVENING FOR PZZ376.

$$

15/15/15



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