388  
FXUS66 KMFR 261500  
AFDMFR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEDFORD OR  
800 AM PDT SUN MAR 26 2017  
   
DISCUSSION
 
26/12Z NAM IN.  
 
THE NORTHERN HEMISPHERIC PROJECTION SHOWS A WAVE NUMBER OF FOUR  
AROUND THE GLOBE AND OCCASIONALLY HINTS AT A FIVE OVER THE NEXT  
SEVERAL DAYS. THIS ARGUES FOR A MODERATELY PROGRESSIVE PATTERN.  
THAT IS INDEED WHAT WE WILL GET OVER THE NEXT SEVERAL DAYS.  
OVERALL THE PATTERN LOOKS QUITE SPRING LIKE...WITH WEAKER STORMS  
DRIVEN BY LOW AMPLITUDE UPPER LEVEL TROUGHS. THE PRIMARY STORM  
TRACK WILL REMAIN TO THE NORTH OF THE AREA...BUT THERE WILL BE  
SOME ACTION DOWN HERE.  
 
A WEAK LONG WAVE RIDGE IS NOW MOVING OUT TO THE EAST. AN UPPER  
LEVEL TROUGH IS APPROACHING THE COAST...AND IT IS EJECTING SHORT  
WAVES SHORT WAVES OUT AHEAD OF IT. THE FIRST OF THESE SHORT WAVES  
IS SUPPORTING A SURFACE FRONT WHICH IS NOW MOVING ONSHORE. LIGHT  
PRECIPITATION IS BEING REPORTED OVER THE ENTIRE WEST SIDE AND  
NEAR EAST SIDE. NOT MUCH IN THE WAY OF WINDS YET THOUGH. WINDS  
HAVE BEEN GUSTY OVER THE RIDGES...IN THE SHASTA VALLEY...AND EAST  
OF THE CASCADES...BUT NOTHING IMPRESSIVE SO FAR. WITH THE COLD  
CORE ALOFT...ISOLATED THUNDERSTORMS ARE ALSO POSSIBLE TODAY OVER  
THE EAST SIDE AND TONIGHT ALONG THE NORTH COAST. SNOW LEVELS WILL  
RISE TO 4500-6000 FEET SUNDAY...THEN FALL TO AROUND 3500-4500 FEET  
SUNDAY NIGHT.  
 
SUBSEQUENT SHORT WAVES WILL SUPPORT PLENTY OF SHOWER ACTIVITY  
SUNDAY NIGHT INTO MONDAY. THE LAST OF THE SHORT WAVES AND THE  
LONG WAVE TROUGH WILL MOVE THROUGH THE AREA MONDAY. SHOWERS WILL  
DIMINISH IN THE WAKE OF THE TROUGH. SNOW LEVELS WILL BE 3000-4500  
FEET OR SO MONDAY.  
 
AFTER THAT, THERE WILL BE A LONGER BREAK IN THE ACTION AS A LONG  
WAVE RIDGE MOVES TOWARD THE WEST COAST. THIS WILL BRING DRY AND  
WARMER WEATHER TO THE AREA MONDAY NIGHT INTO TUESDAY. THE RIDGE  
AXIS WILL BREAK TO THE EAST OF THE AREA TUESDAY NIGHT AND A STRONG  
SHORT WAVE RIDING UP THE BACK SIDE OF THE RIDGE WILL MOVE ONSHORE  
TO THE NORTH OF THE AREA WEDNESDAY. A WARM FRONT WILL MOVE ONSHORE  
TUESDAY NIGHT...FOLLOWED BY A TRAILING COLD FRONT WEDNESDAY  
AFTERNOON. WITH MOST OF THE UPPER LEVEL SUPPORT REMAINING TO THE  
NORTH...BOTH FRONTS WILL BE RELATIVELY WEAK THIS FAR SOUTH. EVEN  
SO...MOST IF NOT ALL OF THE MEDFORD CWA WILL GET SOME LIGHT  
PRECIPITATION TUESDAY NIGHT INTO WEDNESDAY. A STRONGER SHORT WAVE  
WITH A MORE SOUTHERLY TRAJECTORY WILL MOVE ONSHORE WEDNESDAY  
NIGHT WITH THE LONG WAVE TROUGH. THIS WILL SUPPORT POST-FRONTAL  
SHOWERS LASTING INTO THURSDAY.  
 

 
   
AVIATION...26/12Z TAF CYCLE
 
A COLD FRONT WILL ARRIVE AT THE COAST  
EARLY THIS MORNING AND WEAKEN AS IT SPREADS INLAND THROUGH THE DAY.  
AHEAD OF THIS FRONT, A STRONGER SW WINDS ALOFT COULD LEAD TO LOW  
LEVEL WIND SHEAR AT NORTH BEND EARLY THIS MORNING, THEN MID MORNING  
AT ROSEBURG AND MEDFORD. LOW LEVEL WIND SHEAR SHOULD NOT BE A  
CONCERN BY THIS AFTERNOON AND KEPT IT OUT OF THE TAF, BUT WILL NEED  
TO BE REEVALUATED. THE FRONT WILL ALSO BRING INCREASED COVERAGE OF  
MVFR FOR AREAS WEST OF THE CASCADES WITH LOCAL IFR OVER THE COASTAL  
RANGE. SNOW LEVELS WILL BE AROUND 5000 TO 5500 FEET MSL.  
-PETRUCELLI  
 

 
   
MARINE...UPDATED 230 AM PDT SUNDAY 26 MARCH 2017
 
SOUTH WINDS ARE  
ALREADY INCREASING AND ARE APPROACHING SMALL CRAFT AHEAD OF THE NEXT  
FRONT THAT IS STILL WEST OF THE WATERS. SOUTH WINDS WILL RAMP UP  
FURTHER TO GALES IN THE NEXT FEW HOURS WITH GALES EXPECTED TO LAST  
INTO THE AFTERNOON. STEEP SEAS ARE ALSO EXPECTED. THE MODELS ARE IN  
PRETTY GOOD AGREEMENT PUSHING THE FRONT ONSHORE THIS EVENING AT  
WHICH POINT WINDS WILL DECREASE AND BECOME SOUTHWEST. HOWEVER SEAS  
WILL REMAIN STEEP THROUGH THIS EVENING. SEAS WILL DECREASE TONIGHT  
INTO EARLY MONDAY MORNING, THEN A COMBINATION OF A LONGER PERIOD AND  
SHORTER PERIOD WEST SWELL IS DUE TO MOVE IN MONDAY AFTERNOON  
RESULTING IN COMBINED SEAS BETWEEN 10-13 FEET. STEEP SEAS COULD  
LINGER THROUGH AT LEAST WEDNESDAY NIGHT. -PETRUCELLI  
 

 
   
MFR WATCHES/WARNINGS/ADVISORIES
 
 
OR...WINTER WEATHER ADVISORY UNTIL 11 AM PDT MONDAY FOR ORZ027-028.  
 
CA...WIND ADVISORY FROM NOON TODAY TO 8 PM PDT THIS EVENING FOR  
CAZ081.  
 
PACIFIC COASTAL WATERS...GALE WARNING UNTIL 5 PM PDT THIS AFTERNOON FOR  
PZZ350-356-370-376.  
HAZARDOUS SEAS WARNING UNTIL 5 PM PDT THIS AFTERNOON FOR  
PZZ350-356-370-376.  
 

 
 
15/15/15  
 
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