Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 240404
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
904 PM PDT THU OCT 23 2014

.SHORT TERM...A FRONTAL BOUNDARY IS LOCATED JUST EAST OF THE
CASCADES EXTENDING SOUTHWEST INTO NORTHERN CALIFORNIA. AS A LOW TO
THE WEST APPROACHES THE REGION, THIS FRONTAL BOUNDARY  WILL
GRADUALLY LIFT NORTHWARD TONIGHT AND FRIDAY MORNING. AS IT DOES
SO, EXPECT WESTERN AREAS WHICH ARE CURRENTLY GETTING LITTLE
RAINFALL, TO ONCE AGAIN RECEIVE LIGHT TO MODERATE RATE TONIGHT
INTO FRIDAY MORNING. AS THE FRONT CONTINUES TO LIFT NORTH DURING
THE AFTERNOON ON FRIDAY...EXPECT RAIN TO TAPER OFF FROM SOUTHEAST
TO NORTHWEST OVER THE AREA WITH MOST INLAND AREAS BEING DRY BY
EARLY FRIDAY EVENING. MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE
TIMING OF THE FRONTAL BOUNDARY AS IT LIFTS NORTH TONIGHT AND
TOMORROW MORNING. SO HAVE INCREASED POPS OVER PORTIONS OF
SOUTHWEST OREGON, INCLUDING THE MEDFORD AREA, DURING THE OVERNIGHT
PERIOD.

THEN, MODELS CONTINUE TO SHOW THAT A STRONG SURFACE LOW, AROUND
992MB, WILL APPROACH THE COAST OF NORTHERN CALIFORNIA AND SOUTHERN
OREGON FRIDAY NIGHT AND MOVE NORTH-NORTHEAST ALONG THE OREGON
COAST SATURDAY MORNING...THEN INLAND NORTH OF THE AREA ON
SATURDAY. AS THIS LOW APPROACHES THE COAST INSIDE OF 130W LATE
FRIDAY NIGHT AND INTO SATURDAY, EXPECT STRONG AND GUSTY WINDS TO
DEVELOP OVER THE AREA. HIGH WIND WATCHES FOR STRONG SOUTH WINDS
GUSTING TO 60 MPH OR GREATER REMAIN IN EFFECT FOR THE SHASTA
VALLEY, SUMMER LAKE AREA, AND OVER THE SISKIYOUS MOUNTAINS AS WELL
AS FOR MOUNTAINS EAST OF THE CASCADES. THE 00Z NAM CONTINUES TO
SHOW HIGH WIND POTENTIAL FOR THESE AREAS WITH A 70 KT 700 MB JET
MOVING ACROSS THE AREA FRIDAY NIGHT AND SATURDAY. IN ADDITION THE
NAM INDICATES THAT A STRONG SURFACE PRESSURE GRADIENT WILL DEVELOP
ALONG WITH 35 TO 45 KT SOUTH WINDS AT 850 MB FOR AREAS WEST OF THE
CASCADES IN SOUTHERN OREGON FRIDAY NIGHT INTO SATURDAY. THIS IS
EXPECTED TO BRING GUSTY WINDS INTO WESTERN VALLEYS, ESPECIALLY FOR
THE SOUTHERN ROGUE VALLEY. ALONG THE COAST, WINDS ARE EXPECTED TO
REMAIN BELOW HIGH WIND WARNING LEVELS BUT COASTAL HEADLANDS MAY
EXPERIENCE HIGH WINDS WITH GUSTS TO 60 MPH LATE FRIDAY NIGHT AND
SATURDAY.

IN ADDITION, TO WIND IMPACTS, THIS STRONG LOW WILL BRING RAIN
INTO THE AREA ON SATURDAY. ALSO COLD AIR ALOFT IMMEDIATELY BEHIND
THE FRONT AND ASSOCIATED INSTABILITY WILL BRING A CHANCE FOR
THUNDERSTORMS TO THE AREA AS WELL ON SATURDAY. OF NOTE IS THAT ANY
THUNDERSTORMS THAT OCCUR MAY BRING STRONG GUSTY  WINDS DUE TO THE
STRONG WINDS ALOFT.

&&

.AVIATION...BASED ON THE 24/00Z TAF CYCLE...
A STALLED FRONT FROM SOUTHERN SISKIYOU COUNTY NORTHEASTWARD TO
SOUTHERN LAKE COUNTY WILL BE THE FOCUS FOR PRECIPITATION AND REDUCED
CEILINGS AND VISIBILITY THIS EVENING. THE REST OF THE AREA WILL BE VFR
THIS EVENING, BUT WITH SOME TERRAIN OBSCURED WEST OF THE CASCADES. THE
FRONT WILL LIFT BACK TO THE NORTH AS A WARM FRONT OVERNIGHT INTO
FRIDAY MORNING, LIKELY RESULTING IN CIGS/VIS LOWERING TO MVFR/IFR
WITH TERRAIN OBSCURED ALONG AND WEST OF THE CASCADES. IMPROVEMENT
WILL OCCUR FROM SOUTHEAST TO NORTHWEST ACROSS THE AREA FRIDAY.
CONFIDENCE IN CIGS/VIS OVERNIGHT INTO FRIDAY MORNING IS LOW DUE TO
THE SIGNIFICANT VARIATIONS EXPECTED. SPILDE

&&

.MARINE...UPDATED 515 PM PDT THU 23 OCT 2014...
SEAS WILL REMAIN ELEVATED AND HAZARDOUS TO SMALL CRAFT TONIGHT, BUT
MODERATE WEST SWELL WILL EASE BY FRIDAY MORNING. THERE WILL BE A
LULL IN BOTH WINDS AND SEAS THROUGH MUCH OF FRIDAY. MODELS CONTINUE
TO SHOW A SURFACE LOW DEEPENING NEAR 40 NORTH AND 130 WEST FRIDAY
NIGHT THEN MOVING NORTHEASTWARD INSIDE 130 WEST INTO NORTHERN OREGON
AND WASHINGTON BY SATURDAY AFTERNOON. HISTORICALLY, THIS IS A
FAVORABLE SURFACE LOW TRACK FOR HIGH-END GALES AND EVEN POTENTIAL
STORM FORCE WINDS OVER THE OREGON COASTAL WATERS. THE GFS/HI-RES
ARW/GEM MODELS ARE SHOWING MORE OF A COMPACT LOW WITH PRESSURES AS
LOW AS 985MB, WHILE THE EC/NAM HAVE MORE OF AN ELONGATED LOW WITH
PRESSURES DOWN TO 993MB. TAKING AN AVERAGE OF THE MODEL BL AND
SURFACE FLOW, HAVE SUSTAINED WINDS IN THE 35-45 KT RANGE FOR MOST OF
THE AREA WITH SOME GUSTS POTENTIALLY REACHING 60 KT NEAR CAPE BLANCO
AND OVER THE OUTER WATERS BY SATURDAY AS THE ASSOCIATED SURFACE
FRONT MOVES ONSHORE. HAVE ISSUED A STORM/GALE WATCH FRIDAY NIGHT
INTO SATURDAY FOR ALL ZONES WITH THE BEST POTENTIAL FOR STORM FORCE
GUSTS OVER THE OUTER WATERS AND IN THE VICINITY OF CAPE BLANCO.
THESE WINDS WILL LEAD TO VERY DANGEROUS CHAOTIC SEAS OF UP TO 23
FEET DURING THIS TIME FRAME. CONDITIONS WILL IMPROVE THROUGH
THE REMAINDER OF THE WEEKEND, AND AFTER ANOTHER BRIEF ROUND OF
CALMER WINDS AND SEAS, ANOTHER FRONT IS EXPECTED EARLY NEXT WEEK.
SPILDE

&&

.PREV DISCUSSION... /ISSUED 518 PM PDT THU OCT 23 2014/

DISCUSSION...THE FRONTAL BOUNDARY IS SLOWLY SAGGING SOUTH AND
RAIN SHOWERS WILL CONTINUE TO MOVE SOUTH THROUGHOUT THIS EVENING.
THIS MEANS THE PRECIPITATION SHOULD TAPER OFF SIGNIFICANTLY IN THE
ROGUE VALLEY THIS EVENING BUT MOST OF SISKIYOU COUNTY WILL
CONTINUE TO SEE RAIN OVERNIGHT. WITH PLENTY OF LOW LEVEL MOISTURE,
UPSLOPE FLOW WILL CONTINUE TO PRODUCE SHOWERS INTO THE CASCADES
AND SISKIYOUS.

THE CONCERN THEN SHIFTS TO THE NEXT LOW PRESSURE THAT IS FORECAST
TO MOVE ACROSS THE COASTAL WATERS FRIDAY AFTERNOON. MODELS ARE IN
A BETTER AGREEMENT ON THE TRACK AND TAKE THE LOW NORTHEAST TOWARD
ASTORIA. BOTH THE NAME AND THE GFS SHOW VERY STRONG PRESSURE
GRADIENTS FROM ARCATA TO NORTH BEND WITH THIS SYSTEM. COASTAL
WATERS COULD SEE STORM FORCE WINDS WITH THIS SYSTEM. HOWEVER WIND
DIRECTION WILL BE OUT OF THE SOUTHEAST AND THIS IS NOT AS
FAVORABLE FOR VERY STRONG WINDS AT THE COAST EXCEPT AT THE
HEADLANDS. THE STRONG GRADIENTS WILL GENERATE STRONG WINDS ACROSS
THE SHASTA VALLEYS WHILE 700MB WINDS WILL BE IN THE 50-60 MPH
RANGE. I HAVE ISSUED THE HIGH WIND WATCH FOR THE SHASTA VALLEY AND
THE HIGHER ELEVATIONS OF EASTERN OREGON AND NE CALIFORNIA. IN
ADDITION THE SISKIYOU MOUNTAINS COULD ALSO SEE A VERY STRONG SOUTH
WINDS IMPACTING THE SISKIYOU PASS AND MOUNT ASHLAND AREA.

RAIN ASSOCIATED WITH THIS NEXT SYSTEM WILL BE MODERATE TO HEAVY
AGAIN AT THE COAST WITH SOUTHEAST DOWNSLOPE FLOW SLOWING DOWN THE
ARRIVAL OF RAIN IN THE ROGUE VALLEY UNTIL SATURDAY. THERE IS SOME
INSTABILITY WITH THE FRONT ON SATURDAY AND A FEW LIGHTNING STRIKES
ARE POSSIBLE. IN ADDITION FORECAST SOUNDING SHOWS POTENTIAL FOR
GUSTING WINDS AS WELL.

BOTH THE GFS AND THE ECMWF DIVERGE SIGNIFICANTLY FROM TUESDAY
FORWARD WITH THE GFS MAINTAINING THE RIDGE AND WARMER
TEMPERATURES; WHEREAS THE ECMWF BRINGS A LOW PRESSURE INTO
NORTHERN CALIFORNIA WITH COOLER TEMPERATURES AND LOWER SNOW
LEVELS FOR NEXT WEEK. HAVE CONTINUED WITH CLIMATOLOGY POPS IN THE
EXTENDED. /FB

AVIATION...BASED ON THE 24/00Z TAF CYCLE...
A FRONT STALLING FROM SOUTHERN SISKIYOU COUNTY NORTHEASTWARD TO
SOUTHERN LAKE COUNTY WILL BE THE FOCUS FOR PRECIPITATION AND
REDUCED CEILINGS AND VISIBILITY THIS EVENING. THE REST OF THE AREA
WILL BE VFR THIS EVENING, BUT WITH SOME TERRAIN OBSCURED ALONG AND
WEST OF THE CASCADES. THE FRONT WILL LIFT BACK TO THE NORTH AS A
WARM FRONT OVERNIGHT INTO FRIDAY MORNING, LIKELY RESULTING IN
ANOTHER ROUND OF LIGHT TO MODERATE RAINFALL ALONG AND WEST OF THE
CASCADES WITH CIGS/VIS LOWERING TO MVFR/IFR. TERRAIN OBSCURATIONS
WILL BECOME TOTAL. IMPROVEMENT WILL OCCUR FROM SOUTHEAST TO
NORTHWEST ACROSS THE AREA FRIDAY. CONFIDENCE IN CIGS/VIS OVERNIGHT
INTO FRIDAY MORNING IS LOW DUE TO THE SIGNIFICANT VARIATIONS
EXPECTED. SPILDE

MARINE...UPDATED 515 PM PDT THU 23 OCT 2014...
SEAS WILL REMAIN ELEVATED AND HAZARDOUS TO SMALL CRAFT TONIGHT, BUT
MODERATE WEST SWELL WILL EASE BY FRIDAY MORNING. THERE WILL BE A
LULL IN BOTH WINDS AND SEAS THROUGH MUCH OF FRIDAY. MODELS CONTINUE
TO SHOW A SURFACE LOW DEEPENING NEAR 40 NORTH AND 130 WEST FRIDAY
NIGHT THEN MOVING NORTHEASTWARD INSIDE 130 WEST INTO NORTHERN OREGON
AND WASHINGTON BY SATURDAY AFTERNOON. HISTORICALLY, THIS IS A
FAVORABLE SURFACE LOW TRACK FOR HIGH-END GALES AND EVEN POTENTIAL
STORM FORCE WINDS OVER THE OREGON COASTAL WATERS. THE GFS/HI-RES
ARW/GEM MODELS ARE SHOWING MORE OF A COMPACT LOW WITH PRESSURES AS
LOW AS 985MB, WHILE THE EC/NAM HAVE MORE OF AN ELONGATED LOW WITH
PRESSURES DOWN TO 993MB. TAKING AN AVERAGE OF THE MODEL BL AND
SURFACE FLOW, HAVE SUSTAINED WINDS IN THE 35-45 KT RANGE FOR MOST OF
THE AREA WITH SOME GUSTS POTENTIALLY REACHING 60 KT NEAR CAPE BLANCO
AND OVER THE OUTER WATERS BY SATURDAY AS THE ASSOCIATED SURFACE
FRONT MOVES ONSHORE. HAVE ISSUED A STORM/GALE WATCH FRIDAY NIGHT
INTO SATURDAY FOR ALL ZONES WITH THE BEST POTENTIAL FOR STORM FORCE
GUSTS OVER THE OUTER WATERS AND IN THE VICINITY OF CAPE BLANCO.
THESE WINDS WILL LEAD TO VERY DANGEROUS CHAOTIC SEAS OF UP TO 23
FEET DURING THIS TIME FRAME. CONDITIONS WILL IMPROVE THROUGH
THE REMAINDER OF THE WEEKEND, AND AFTER ANOTHER BRIEF ROUND OF
CALMER WINDS AND SEAS, ANOTHER FRONT IS EXPECTED EARLY NEXT WEEK.
SPILDE

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WATCH FROM FRIDAY EVENING THROUGH SATURDAY EVENING FOR
     ORZ029>031.
     HIGH WIND WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY EVENING
     FOR ORZ028.

CA...HIGH WIND WATCH FROM FRIDAY EVENING THROUGH SATURDAY EVENING FOR
     CAZ081>083-085.

PACIFIC COASTAL WATERS...GALE WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY AFTERNOON FOR
     PZZ350-356.
     STORM WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY AFTERNOON
     FOR PZZ350-356.
     HAZARDOUS SEAS WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY
     AFTERNOON FOR PZZ350-356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM PDT FRIDAY
     FOR PZZ350-356-370-376.
     GALE WATCH FROM FRIDAY EVENING THROUGH SATURDAY AFTERNOON FOR
     PZZ370-376.
     STORM WATCH FROM FRIDAY EVENING THROUGH SATURDAY AFTERNOON FOR
     PZZ370-376.
     HAZARDOUS SEAS WATCH FROM FRIDAY EVENING THROUGH SATURDAY
     AFTERNOON FOR PZZ370-376.

$$

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