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FXUS66 KMFR 310429  
AFDMFR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEDFORD OR  
929 PM PDT SAT MAY 30 2020  
   
UPDATE
 
BANDS OF RAIN CONTINUE TO DIMINISH AND NARROW TOWARDS  
THE WEST SIDE CASCADE FOOTHILLS AND THE CASCADES TONIGHT. NO  
LIGHTNING HAS BEEN OBSERVED FOR THE PAST SEVERAL HOURS AS A  
STRONG INVERSION HAS SET IN OVER THE FORECAST AREA. HAVE ADJUSTED  
TO DECREASE THE AREA OF PRECIPITATION TONIGHT. SVEN  
 

 
   
PREV DISCUSSION
 
/ISSUED 502 PM PDT SAT MAY 30 2020/  
 
UPDATED AVIATION DISCUSSION.  
 
DISCUSSION...MODELS HAVE BEEN ADVERTISING THE POTENTIAL FOR  
STORMS FOR SEVERAL DAYS NOW, AND TODAY'S STORMS PANNED OUT GENERALLY  
AS EXPECTED. EARLY THIS MORNING ABOUT 200 CLOUD TO GROUND LIGHTNING  
FLASHES IMPACTED AREAS WEST OF I-5, IN THE KALMIOPSIS AND NORTHWARD  
INTO THE UMPQUA BASIN. THEN, ON THE NORTHERN PERIPHERY OF THE RAIN  
SHIELD MORE STORMS DEVELOPED LATER IN THE MORNING, IMPACTING  
JACKSON, DOUGLAS, AND CENTRAL AND EASTERN SISKIYOU COUNTIES. THESE  
LATER STORMS WERE STRONG AND FEATURED HEAVY RAIN AND PLENTY OF  
LIGHTNING. A FEW HOURS LATER, SEVERE STORMS IMPACTED AREAS ALONG AND  
JUST EAST OF HIGHWAY 97. GOLF BALL SIZED HAIL WAS REPORTED FROM ONE  
OF THE STORMS. IN TOTAL, ABOUT 900 CLOUD TO GROUND LIGHTNING FLASHES  
WERE OBSERVED OVER OUR 9-COUNTY WARNING AREA SINCE EARLY THIS  
MORNING. THE THREAT OF SEVERE STORMS IS DIMINISHING THIS AFTERNOON  
AS STABILITY INCREASES FROM WEST TO EAST THROUGH THE EVENING.  
 
ACTIVE WEATHER WILL BE ON THE DECREASE THIS EVENING WITH MOST, IF  
NOT ALL OF THE ACTION NORTH OF OUR FORECAST AREA. STILL COULD NOT  
RULE OUT ISOLATED STORMS IN NORTHERN KLAMATH AND LAKE COUNTY  
EARLY THIS EVENING WITH GUSTY WINDS, BUT WE DON'T THINK ANY OF  
THEM WILL BE SEVERE.  
 
THE UPPER TROUGH AXIS WILL SHIFT TO THE NORTH LATER THIS EVENING AND  
TONIGHT WITH SHOWERS DECREASING LATER THIS EVENING AND OVERNIGHT  
TONIGHT. LOW TEMPERATURES TONIGHT FOR INLAND AREAS WILL END UP  
COOLER.  
 
SUNDAY SHOULD BE A DRY DAY FOR MOST HOURS AND LOCATIONS AS WEAK  
SHORTWAVE RIDING BUILDS IN. HOWEVER THERE MAY BE ENOUGH INSTABILITY  
FOR A FEW ISOLATED SHOWERS LATE IN THE AFTERNOON AND EARLY EVENING  
IN PORTIONS OF THE CASCADES AND EASTSIDE. KEPT IN A SLIGHT CHANCE OF  
THUNDER NEAR AND OVER THE WARNERS IN EASTERN MODOC COUNTY WHERE  
INSTABILITY WILL BE A LITTLE GREATER.  
 
WEAK TROUGHINESS REMAINS OVER THE AREA TONIGHT INTO MONDAY AND COULD  
NOT RULE OUT ISOLATED SHOWERS ALONG THE CASCADES AND PARTS OF THE  
EAST SIDE. ISOLATED THUNDERSTORMS ARE ALSO POSSIBLE MONDAY AFTERNOON  
AND EVENING FOR THE EASTSIDE.  
 
THE GENERAL CONSENSUS IS FOR THE UPPER TROUGH OFF THE CALIFORNIA  
COAST TO BECOME SPLIT OFF FROM THE MAIN FLOW AND MOVE SOUTH OFF THE  
CALIFORNIA COAST MONDAY NIGHT THROUGH THURSDAY. THEREFORE, WE COULD  
CATCH A BREAK IN THE WEATHER TUESDAY, WEDNESDAY AND THURSDAY. IN  
ADDITION, THE MAJORITY OF THE INDIVIDUAL ENSEMBLE MEMBERS (GFS AND  
ECMWF) CONTINUE TO SHOW NO MEASURABLE PRECIPITATION WHICH HAS BEEN  
THE CASE FOR THE PAST SEVERAL MODEL RUNS. THUS, CONFIDENCE IS  
BECOMING HIGHER FOR DRIER CONDITIONS TUESDAY-THURSDAY. POPS HAVE  
BEEN REDUCED DURING THIS TIME PERIOD AND MAY NEED TO BE REDUCED EVEN  
FURTHER SHOULD ALL THE DATA CONTINUES TO SUPPORT DRY CONDITIONS.  
ALSO MAX TEMPERATURES WERE ADJUSTED HIGHER.  
 
FRIDAY, THE OPERATIONAL ECMWF AND GFS SHOW A DEEPER UPPER TROUGH  
APPROACHING FROM THE PACIFIC BUT DIFFER WITH THE STRENGTH (THE ECMWF  
DIGS THE UPPER TROUGH FURTHER SOUTH). EITHER WAY, IT WILL RESULT IN  
SOME COOLING AND A BETTER CHANCE FOR SHOWERS TOWARDS THE END OF THE  
WEEK MAINLY EAST OF THE CASCADES FRIDAY AFTERNOON AND NIGHT. NEXT  
SATURDAY LOOKS COOLER AND UNSETTLED WITH A BETTER CHANCE FOR SHOWERS  
ALMOST EVERYWHERE AND A SLIGHT CHANCE OF AFTERNOON AND EVENING  
THUNDERSTORMS FOR PORTIONS OF THE EASTSIDE. OF NOTE: THE MAJORITY OF  
THE INDIVIDUAL GFS AND ECMWF ENSEMBLE MEMBERS SHOW MEASURABLE  
PRECIPITATION NEXT FRIDAY AND SATURDAY. -PETRUCELLI  
 
AVIATION...FOR THE 31/00Z TAF CYCLE...ALONG THE COAST, LIGHT RAIN  
WILL RESULT IN MVFR CIGS AND LOCAL IFR CIGS TONIGHT. CEILINGS SHOULD  
IMPROVE TO VFR AROUND 18Z, BUT CONFIDENCE ON THE TIMING IS LOW TO  
MEDIUM.  
 
INLAND WEST SIDE. MVFR AND OCCASIONAL IFR CEILINGS WITH OCCASIONAL  
REDUCTION OF VISIBILITY IS EXPECTED THROUGH THIS EVENING AS  
STRATIFORM PRECIPITATION CONTINUE. THE GENERAL CONSENSUS IS FOR RAIN  
TO DECREASE AND END TONIGHT, BUT PLENTY OF LOW LEVEL MOISTURE AND  
STABLE CONDITIONS COULD RESULT IN MVFR AND OCCASIONAL IFR CEILINGS  
NORTH OF THE UMPQUA DIVIDE AND AND POSSIBLY THE ILLINOIS AND ROGUE  
VALLEY, INCLUDING MEDFORD. CONFIDENCE OF LOWER CEILINGS IN MEDFORD  
WAS NOT HIGH ENOUGH TO INCLUDE IN THE TAF, SO LATER SHIFTS WILL NEED  
TO TAKE ANOTHER LOOK AT THIS.  
 
EAST OF THE CASCADES, MODERATE TO STRONG WINDS ARE POSSIBLE NORTH  
AND EAST OF KLAMATH FALLS INTO THIS EVENING. KLAMATH FALLS AIRPORT  
ARE NOT EXPECTED TO HAVE GUSTY WINDS. VFR CEILINGS ARE EXPECTED  
TONIGHT, BUT WITH MOUNTAINS WILL BE PARTLY OBSCURED. MVFR CEILINGS  
ARE POSSIBLE LATE TONIGHT AND THEY WERE ADDED TO THE TAF.  
 
THE THREAT FOR THUNDERSTORMS HAVE MOVED NORTH OF THE AREA, BUT WE'LL  
STILL NEED TO MONITOR ANY THUNDER THREAT INTO THIS EVENING.  
-PETRUCELLI  
 
MARINE...UPDATED 200 PM PDT SATURDAY 30 MAY 2020...A LOW MOVING  
UP FROM THE SOUTH WILL SHIFT NORTHEASTWARD TONIGHT. SHOWERS WILL  
DIMINISH LATE THIS EVENING AND TONIGHT. SEAS WILL BE DOMINATED BY  
WEST SWELL THROUGH SUNDAY MORNING. GUSTY NORTH WINDS AND STEEP,  
SHORT PERIOD SEAS WILL DEVELOP ACROSS THE WATERS SUNDAY AFTERNOON  
AND EVENING THEN CONTINUE INTO EARLY NEXT WEEK. STRONG NORTH WINDS  
AND VERY STEEP SEAS MAY DEVELOP FOR AREAS SOUTH OF PORT ORFORD  
MONDAY AFTERNOON THROUGH TUESDAY. THEN GUSTY NORTH WINDS AND STEEP  
SEAS ARE EXPECTED TO CONTINUE THROUGH AT LEAST MID WEEK. -CC  
 
FIRE WEATHER...UPDATED 220 PM PDT SATURDAY, 30 MAY 2020...883 CLOUD  
TO GROUND LIGHTNING FLASHES HAVE BEEN OBSERVED SINCE EARLY THIS  
MORNING ACROSS THE FORECAST AREA. LIGHTNING PRODUCTION HAS SHARPLY  
DIMINISHED OVER THE PAST FEW HOURS AS STABILITY INCREASES FROM WEST  
TO EAST. THE AREA OF HEAVIER RAIN WILL CONTINUE THROUGH THE  
AFTERNOON WEST OF THE CASCADES AND THEN DIMINISH, LEAVING MANY 1-  
INCH RAINFALL TOTALS IN ITS WAKE. FROM THE CASCADES EASTWARD, RAIN  
WILL MOVE OVERHEAD AS THE LOW OPENS UP AND MOVES NORTHEAST  
OVERNIGHT. MUCH LIGHTER AMOUNTS ARE EXPECTED EAST OF THE CASCADES  
COMPARED TO WEST OF THE CASCADES.  
 
THE CONDITIONS THAT FOLLOW THE LIGHTNING ARE SO IMPORTANT, AND THE  
TRENDS FOR SUNDAY ARE CLEARLY WARMER AND DRIER THAN TODAY, AND A  
WARMING AND DRYING TREND SHOULD CONTINUE THROUGH WEDNESDAY.  
TEMPERATURES SHOULD PEAK WEDNESDAY AT ABOUT 10 DEGREES ABOVE NORMAL,  
AND THIS IS ABOUT 10 DEGREES COOLER THAN THE HOT TEMPERATURES THAT  
WERE OBSERVED IN RECENT DAYS. AFTERNOON BREEZES TOMORROW SHOULD BE  
LOWER THAN NORMAL, BUT WINDS WILL INCREASE SOME AHEAD OF THE NEXT  
UPPER TROUGH. THE DRIEST AND BREEZIEST DAYS LOOK TO BE TUESDAY AND  
WEDNESDAY BEFORE ANOTHER SYSTEM BRINGS COOLER CONDITIONS AND MORE  
POTENTIAL FOR RAIN AND POSSIBLY THUNDERSTORMS LATE WEEK INTO THE  
WEEKEND. CONFIDENCE IS MODERATE AT THIS TIME FOR THIS RETURN TO  
COOLER AND WETTER CONDITIONS. KEENE  
 

 
   
MFR WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
 
CA...NONE.  
 
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FROM 11 AM SUNDAY TO 5 AM PDT WEDNESDAY FOR  
PZZ350-356-370-376.  
HAZARDOUS SEAS WATCH FROM MONDAY MORNING THROUGH LATE TUESDAY  
NIGHT FOR PZZ356-376.  
 

 
 
SBN/SBN/SBN  
 
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