701  
FXUS66 KMFR 200302  
AFDMFR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEDFORD OR  
802 PM PDT THU OCT 19 2017  
   
DISCUSSION
 
20/00Z NAM IN.  
 
A STRONG FRONT IS NOW MOVING THROUGH THE MEDFORD CWA, BRINGING  
AREAS OF STRONG WINDS AND HEAVY RAIN. THE STEADY PRECIPITATION  
WILL CHANGE TO SHOWERS BEHIND THE FRONT. SNOW LEVELS ARE  
CURRENTLY QUITE HIGH, AROUND 7500 FEET, BUT THEY WILL DROP TO 4000  
TO 4500 FEET FRIDAY MORNING, WHICH IS AFTER THE HEAVIEST  
PRECIPITATION IS OVER WITH. SHOWER ACTIVITY WILL CONTINUE INTO  
FRIDAY, BUT THEY WILL BE LIGHTER IN INTENSITY WITH LESS COVERAGE.  
 
THE UPPER TROUGH DRIVING THE FRONT WILL BREAK TO THE EAST OF THE  
AREA FRIDAY AND A BROAD AND FLAT LONG WAVE RIDGE WILL BUILD IN  
FROM THE SOUTHWEST. THIS WILL PUSH A WARM FRONT NORTH THROUGH THE  
AREA SATURDAY. THE MODELS ARE INDICATING THAT THIS SYSTEM WILL BE  
QUITE WET WITH PLENTY OF OVERRUNNING. GIVEN THE LOW SNOW LEVELS  
THAT WILL BE IN PLACE AT THE BEGINNING OF THE EVENT, AROUND 4000  
FEET, SOME OF THE MOUNTAINOUS AREAS COULD GET A SIGNIFICANT SHOT  
OF SNOW LATE FRIDAY NIGHT INTO SATURDAY MORNING BEFORE THE SNOW  
LEVELS ROCKET BACK UP TO NEAR 10000 FEET SATURDAY AFTERNOON.  
PRECIPITATION WILL DIMINISH QUICKLY SATURDAY AFTERNOON INTO  
SATURDAY EVENING.  
 
THE RIDGE WILL BREAK TO THE EAST OF THE AREA SATURDAY EVENING, AND  
FLOW ALOFT WILL TURN WESTERLY RATHER THAN SOUTHWESTERLY, BECAUSE  
THE UPSTREAM TROUGH IS RELATIVELY WEAK. THAT TROUGH WILL RIDE UP  
AND OVER THE RIDGE, MOVING ONSHORE SUNDAY NIGHT. THE ASSOCIATED  
FRONT WILL BE WEAK THIS FAR SOUTH, AND WON'T AMOUNT TO MUCH IN  
TERMS OF WIND AND PRECIPITATION. IT WILL BRING SMALL CRAFT  
SOUTH WINDS TO THE COASTAL WATERS.  
 
THE LONG WAVE RIDGE WILL BUILD IN MORE STRONGLY BEGINNING ON  
SUNDAY, AND THIS WILL BRING DRIER AND WARMER WEATHER TO THE AREA.  
 
LONG TERM DISCUSSION...MONDAY 23 OCT THROUGH THURSDAY 26 OCT 2017.  
HIGH PRESSURE WILL BUILD INTO THE AREA AND BRING DRY WEATHER  
EARLY NEXT WEEK. WARMER TEMPERATURES ARE EXPECTED MONDAY AND  
TUESDAY WITH HIGHS IN THE 70S FOR WESTERN VALLEYS AND IN THE 60S  
FOR EASTERN VALLEYS. THIS RIDGE IS FORECAST TO WEAKEN TUESDAY  
NIGHT AND WEDNESDAY AS A FRONT MOVES INLAND TO THE NORTH. A SLIGHT  
CHANCE FOR LIGHT PRECIPITATION IS EXPECTED ON WEDNESDAY FOR  
PORTIONS OF THE COAST AND THE UMPQUA VALLEY.  
 

 
   
AVIATION...20/00Z TAF CYCLE...FROM THE CASCADES WEST
 
A COLD FRONT  
IS NOW MOVING THROUGH THE AREA, BRINGING AREAS OF MVFR/IFR  
CIGS/VSBYS IN SHOWERS AND EXTENSIVE OBSCURATION OF HIGHER TERRAIN.  
THERE WILL ALSO BE LOW LEVEL WIND SHEAR AHEAD OF AND WITH THE FRONT.  
CONDITIONS WILL IMPROVE FRIDAY MORNING TO LOCAL MVFR CIGS IN SHOWERS  
WITH AREAS OF HIGHER TERRAIN OBSCURED. THIS WILL PERSIST INTO FRIDAY  
EVENING. EAST OF THE CASCADES...IT WILL BE QUITE WINDY WITH PLENTY  
OF TURBULENCE AHEAD OF THE FRONT, BUT CONDITIONS WILL BE MOSTLY VFR  
WITH SOME OBSCURATION OF HIGHER TERRAIN. AFTER THE FRONT PASSES,  
AREA OF MVFR CIGS/VSBYS WILL DEVELOP WITH MORE OBSCURATION OF HIGHER  
TERRAIN. CONDITIONS WILL IMPROVE TO ISOLATED MVFR CIGS BY FRIDAY  
AFTERNOON, BUT WINDS WILL PICK UP AGAIN FRIDAY AFTERNOON.  
 

 
   
MARINE...UPDATED 800 PM PDT THURSDAY 19 OCTOBER 2017
 
HEAVY LONG  
PERIOD NORTHWEST SWELL IS NOW BUILDING INTO THE WATERS. THIS IS  
CREATING VERY HIGH AND STEEP SEAS ALONG WITH DANGEROUS SURF AND  
BAR CONDITIONS. COMBINED SEAS WILL PEAK AT AROUND 21 FEET THIS  
EVENING, THEN SLOWLY SUBSIDE INTO FRIDAY NIGHT. HOWEVER, AROUND  
THAT TIME ANOTHER ROUND OF STRONG SOUTH WINDS WILL DEVELOP AS A  
WARM FRONT MOVES THROUGH THE AREA. GALE FORCE WINDS ARE LIKELY  
OVER MOST OF THE AREA. WINDS AND SEAS WILL SUBSIDE AGAIN SATURDAY.  
 
A THERMAL TROUGH WILL SET UP ALONG THE COAST EARLY NEXT WEEK, AND  
THIS WILL BRING STRONG NORTH WINDS AND STEEP SEAS SOUTH OF CAPE  
BLANCO BEGINNING MONDAY AND CONTINUING THROUGH TUESDAY.  
 

 
   
MFR WATCHES/WARNINGS/ADVISORIES
 
 
OR...HIGH WIND WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ030-031.  
WIND ADVISORY UNTIL 11 PM PDT THIS EVENING FOR ORZ029>031.  
FLASH FLOOD WATCH UNTIL 11 PM PDT THIS EVENING FOR ORZ022-024.  
HIGH SURF ADVISORY UNTIL 11 PM PDT FRIDAY FOR ORZ021-022.  
 
CA...HIGH WIND WARNING UNTIL 11 PM PDT THIS EVENING FOR CAZ085.  
WIND ADVISORY UNTIL 11 PM PDT THIS EVENING FOR CAZ084-085.  
FLASH FLOOD WATCH UNTIL 11 PM PDT THIS EVENING FOR CAZ080.  
WIND ADVISORY UNTIL 8 PM PDT THIS EVENING FOR CAZ081.  
 
PACIFIC COASTAL WATERS...HAZARDOUS SEAS WARNING UNTIL 11 PM PDT FRIDAY  
FOR PZZ350-356-370-376.  
 

 
 
15/18/15  
 
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