Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 192146
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
246 PM PDT SAT APR 19 2014

.SHORT TERM...BEHIND A WEAK FRONT EXPECT COOL TEMPERATURES TONIGHT
FOLLOWED BY A BRIEF PERIOD OF RIDGING AND WARM AND DRY CONDITIONS
SUNDAY. THEN A MORE ACTIVE AND MOIST PATTERN IS EXPECTED BEGINNING
EARLY NEXT WEEK.

CURRENTLY, A WEAK FRONT HAS MOVED INLAND TO THE CASCADES
AND WILL DISSIPATE OVER THE AREA THIS EVENING. PERIODS OF LIGHT
RAIN WILL CONTINUE MAINLY FOR THE COASTAL AREAS AND ACROSS DOUGLAS
COUNTY. BEHIND THIS FRONT EXPECT CLEARING SKIES, ALTHOUGH LOW
CLOUDS WILL LIKELY REDEVELOP IN THE COQUILLE AND UMPQUA VALLEY
LATE TONIGHT. COOLER TEMPERATURES ARE EXPECTED TONIGHT AND SUNDAY
MORNING FOR WEST SIDE VALLEYS ALONG WITH LIGHT WINDS. HAVE ISSUED
A FROST ADVISORY FOR PORTIONS OF JOSEPHINE AND JACKSON COUNTY DUE
TO COLD TEMPERATURES IMPACTING AGRICULTURAL INTERESTS.

ON SUNDAY EXPECT WARM TEMPERATURES AND DRY CONDITIONS ACROSS THE
AREA WITH AN UPPER LEVEL RIDGE BUILDING INLAND AND AN UPPER TROUGH
DEVELOPING OFFSHORE. LOW CLOUDS AND PATCHY FOG IN COOS AND DOUGLAS
COUNTIES IS EXPECTED TO CLEAR IN THE LATE MORNING ON SUNDAY.
OTHERWISE EXPECT MOSTLY CLEAR TO PARTLY CLOUDY SKIES OVER THE AREA
ON SUNDAY.

MONDAY AND TUESDAY...MODELS FORECAST A CHANGE IN THE WEATHER
PATTERN. ON MONDAY...MODELS CONTINUE TO INDICATE THAT A FRONT WILL
MOVE TOWARDS THE AREA...THEN PUSH INLAND MONDAY EVENING AND
NIGHT. AHEAD OF THE FRONT, MODELS INDICATE SOME SOUTHERLY MOISTURE
WILL MOVE INTO THE AREA AND WEAK INSTABILITY WILL DEVELOP ALONG
THE CASCADES AND INTO NORTHERN KLAMATH COUNTY. CURRENTLY HAVE KEPT
MENTION OF THUNDERSTORMS OUT OF THE FORECAST GIVEN THE VERY WEAK
INSTABILITY VALUES BUT KEPT MENTION OF A SLIGHT CHANCE TO CHANCE
FOR SHOWERS ACROSS INLAND AREAS DURING THE DAY MONDAY.
INLAND...EXPECT TEMPERATURES TO REMAIN RELATIVELY WARM ON MONDAY
WITH HIGHS IN THE MID 60S TO LOW 70S ACROSS INLAND AREAS. BREEZY
AND GUSTY SOUTH TO SOUTHWEST WINDS ARE EXPECTED TO DEVELOP IN THE
AFTERNOON AND EVENING HOURS, ESPECIALLY ACROSS NORTHERN CALIFORNIA
AND FROM THE CASCADES EAST.

THEN MONDAY EVENING AND NIGHT, A COLD FRONT WILL MOVE INLAND
BRINGING LIGHT TO MODERATE PRECIPITATION ACROSS THE AREA. SNOW LEVELS
WILL GRADUALLY LOWER WITH THE FRONTAL PASSAGE FROM AROUND 6000 TO
7000 FEET MONDAY EVENING DOWN TO 5000 FEET MONDAY NIGHT...WITH
SNOW LEVELS EXPECTED TO LOWER FURTHER TO AROUND 4000 FEET TUESDAY
MORNING AS SHOWERS CONTINUE. ON THE BACKSIDE OF THE FRONT AND IN
SHOWERS EXPECT SOME LIGHT SNOW ACCUMULATIONS OVER THE HIGHER
TERRAIN.

A COLD SHOWERY AIR MASS IS FORECAST BEHIND THE FRONT ON TUESDAY AS
A LARGE UPPER TROUGH MOVES INTO PLACE. ALSO THE NAM AND GFS SHOW
INCREASED INSTABILITY WITH COLD AIR ALOFT OVER AREAS EAST OF THE
CASCADES TUESDAY AFTERNOON. SO HAVE EXPANDED THE SLIGHT CHANCE OF
THUNDERSTORMS TO EXTEND FROM THE CASCADES EASTWARD ON TUESDAY.
ALSO, THE NAM SHOWS INCREASED INSTABILITY ALONG THE COAST AND INTO
COOS AND DOUGLAS COUNTIES TUESDAY MORNING AND HAVE ADDED A SLIGHT
CHANCE FOR THUNDERSTORMS FOR THESE AREAS.

MODELS SHOW INCREASED VARIABILITY CONCERNING HOW MUCH SHOWERS ARE
EXPECTED TUESDAY NIGHT AS THE UPPER TROUGH SHIFTS EAST OUT OF THE
AREA. THE OPERATIONAL GFS SHOWS A STRONGER RIDGE DEVELOPING OFFSHORE
AND A BRIEF PERIOD OF DRIER WEATHER POSSIBLE TUESDAY NIGHT WHILE
THE ECMWF INDICATES A WEAKER RIDGE WITH MOIST ONSHORE FLOW AND
ADDITIONAL SHOWERS OVER THE AREA. GIVEN THE PROGRESSIVE PATTERN
WITH A STRONG UPPER LEVEL JET OFFSHORE, HAVE LEANED MORE TOWARDS
THE ECMWF SOLUTION WITH SHOWERS LIKELY WEST OF THE CASCADES IN
OREGON AND SLIGHT CHANCE TO CHANCE OF SHOWERS ELSEWHERE IN THE
CWA.

.LONG TERM...THE OPERATIONAL EC AND GFS REMAIN IN FAIRLY GOOD
AGREEMENT WITH THE OVERALL PATTERN THROUGH THE PERIOD. CONFIDENCE IS
MODERATE TO HIGH THAT WE`LL BE COOLER AND UNSTABLE MOST OF THE TIME.
A HIGH AMPLITUDE TROUGH WILL MOVE EAST OF THE FORECAST AREA
WEDNESDAY WITH WEAK RIDGING BUILDING IN AND WE COULD CATCH A
RELATIVE BREAK IN THE WEATHER, BUT CONFIDENCE IS NOT HIGH. THIS IS
BECAUSE THE EC SHOWS WARM FRONT AHEAD OF DEVELOPING SURFACE LOW THAT
COULD SPREAD STEADY MODERATE PRECIPITATION TO THE NORTHWEST PART OF
THE AREA. IN CONTRAST THE GFS HAS THE WARM FRONT POSITIONED FARTHER
OFFSHORE AND THERE`S MORE RIDGING. FOR NOW WENT WITH A BLEND BETWEEN
THE TWO. A COLD FRONT WILL MOVE TOWARDS THE AREA THURSDAY, BUT IT
MAY BE SLOW TO MOVE IN BECAUSE IT`S IT`S NEARLY PARALLEL WITH THE
UPPER FLOW. HOWEVER THE UPPER TROUGH WILL DIG SOUTH AND A SHORTWAVE
WILL ROTATE AROUND THE BASE OF THE UPPER LOW, THUS DRIVING THE FRONT
INTO THE AREA, BUT THAT MAY NOT HAPPEN UNTIL FRIDAY. NEXT WEEKEND IS
LIKELY TO BE COOL AND UNSETTLED. OF NOTE THE RMOP CONTINUES TO SHOW
A HIGH PROBABILITY (67%) OF A DEEPENING TROUGH IN THE EASTERN
PACIFIC FRIDAY EVENING, MOVING TOWARDS THE OREGON COAST SATURDAY
EVENING (56%), OVER OUR AREA NEXT SUNDAY AND MONDAY (49% AND 43%),
THESE ARE CONSIDERED PRETTY HIGH VALUES THIS FAR OUT AND ARE HIGHER
THAN WHAT WAS SHOWN YESTERDAY. THE GOOD NEWS IS THAT THE MOISTURE
WILL BE MUCH NEEDED AND THERE IS A CHANCE WE COULD ADD TO THE
SNOW PACK OVER THE HIGHER ELEVATIONS IN THE CASCADES AND SISKIYOUS.
-PETRUCELLI


&&

.AVIATION...BASED ON 19/18Z TAF CYCLE...VFR CONDITIONS ARE EXPECTED
THROUGH THIS EVENING FOR ALL TERMINALS. THE MAIN CONCERN WILL BE
MODERATE TURBULENCE ALONG AND ON THE LEE SIDE OF THE CASCADES AND
GUSTY WINDS AT KLMT THROUGH THIS EVENING. IFR CIGS RETURN ALONG THE
COAST TONIGHT AND IT`S POSSIBLE IT COULD DEVELOP IN THE UMPQUA
BASIN TOWARDS DAYBREAK SUNDAY. GUIDANCE DOES NOT SHOW IFR CIGS AT
KRBG, BUT IT DIDN`T SHOW IT YESTERDAY EITHER AND LOW CIGS FORMED
AROUND 13Z. FOR NOW KEPT IT IN THE TAF, BUT LATER SHIFTS WILL WANT
TO TAKE ANOTHER LOOK AT THIS. -PETRUCELLI


&&

.MARINE...WINDS WILL CONTINUE TO DECREASE OVER THE WATERS THROUGH
THE EVENING AS A COLD FRONT MOVES INLAND. SEAS WILL DECREASE BRIEFLY
THIS EVENING AS WIND WAVES SUBSIDE, HOWEVER, A VERY HEAVY LONG
PERIOD WESTERLY SWELL WILL ENTER THE REGION LATE TONIGHT...AND SEAS
WILL BECOME VERY STEEP AND HAZARDOUS SUNDAY. SWELL WILL DECAY SOME
PRIOR TO REACHING THE INNER WATERS...SO THE HAZARDOUS SEAS WARNING
DOES NOT EXTEND ALL THE WAY TO THE COAST...BUT HIGH END SMALL CRAFT
CONDITIONS ARE EXPECTED OVER THE INNER WATERS. THE HEAVY SWELL WILL
ALSO SUPPORT HEAVY BREAKERS OVER BARS AND WITHIN THE SURF ZONE.
FISHING GEAR LOCATED AT DEPTHS OF AROUND 750 FEET OR LESS COULD BE
RELOCATED OR DAMAGED. SEAS WILL GRADUALLY SUBSIDE THROUGH EARLY NEXT
WEEK...BUT WILL REMAIN AT SMALL CRAFT ADVISORY LEVELS THROUGH AT
LEAST WEDNESDAY AS SEVERAL MORE SWELL TRAINS PROPAGATE THROUGH THE
REGION. ALTHOUGH NUMEROUS SYSTEMS WILL PASS OVER THE AREA NEXT
WEEK...WINDS WILL REMAIN RELATIVELY LIGHT. -WRIGHT


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY FROM 11 PM THIS EVENING TO 11 AM PDT SUNDAY
     FOR ORZ021-022.
     FROST ADVISORY FROM 2 AM TO 8 AM PDT SUNDAY FOR ORZ024-026.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 2 PM PDT THIS AFTERNOON FOR
     PZZ350-356-370-376.
     HAZARDOUS SEAS WARNING FROM 11 PM THIS EVENING TO 11 AM PDT
     SUNDAY FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 PM PDT TUESDAY
     FOR PZZ350-356-370-376.

$$

CC






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