270  
FXUS66 KMFR 180305  
AFDMFR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEDFORD OR  
805 PM PDT SAT AUG 17 2019  
   
DISCUSSION
 
NO UPDATES PLANNED THIS EVENING. AS EXPECTED, THE  
WEATHER THIS EVENING IS PRACTICALLY INDISTINGUISHABLE FROM LAST  
EVENING. THERE IS VERY LITTLE DIFFERENCE IN SENSIBLE WEATHER: IT'S  
MAINLY CLEAR AND WINDS AND TEMPERATURES ARE VIRTUALLY IDENTICAL.  
THERE ARE, HOWEVER, LESS PERCEPTIBLE CHANGES AFOOT. NAMELY,  
PRESSURES ARE LOWER THAN YESTERDAY, AND THIS IS A SIGN THAT THE  
THERMAL TROUGH THAT HAS BEEN PARKED ALONG THE COAST IS BEGINNING  
TO SHIFT INLAND. GUIDANCE DOES SHOW THE THERMAL TROUGH CONTINUING  
TO MOVE INLAND OVER THE NEXT 24 HOURS, AND THIS WILL RESULT IN THE  
MOST NOTICEABLE CHANGES ALONG THE COAST. GONE TOMORROW WILL BE  
THE WARM TEMPERATURES THAT HAVE BEEN EXPERIENCED OVER THE LAST  
COUPLE OF DAYS, ESPECIALLY AT THE SOUTH COAST AS THE CHETCO EFFECT  
ENDS. STRATUS WILL MOVE ONTO AT LEAST THE NORTH COAST TONIGHT,  
AND WHILE IT MAY STAY OFFSHORE OF THE CURRY COAST TONIGHT, IT WILL  
TRY TO PUSH IN LATER TOMORROW. INLAND AREAS, BY CONTRAST, WILL  
LIKELY SEE A SIMILAR TO SLIGHTLY WARMER DAY TOMORROW AS THE  
THERMAL TROUGH MOVES THROUGH. THIS IS ALL RELATIVELY WELL COVERED  
BY THE GOING FORECAST. -WRIGHT  
 

 
   
AVIATION...FOR THE 18/00Z TAFS...AT THE COAST
 
VFR WILL CONTINUE  
THROUGH EARLY THIS EVENING THEN AREAS OF MVFR CIGS WILL DEVELOP  
LOWERING TO IFR CIGS LATE TONIGHT AND EARLY SUNDAY MORNING MAINLY  
NORTH OF CAPE BLANCO. THE TIMING OF WHEN LOWER CONDITIONS DEVELOP IN  
THE NORTH BEND TAF IS LOW TO MODERATE. ONSHORE FLOW WILL BE STRONGER  
THAN LAST NIGHT ALLOWING MARINE STRATUS TO DEVELOP IN THE COQUILLE  
VALLEY LATE TONIGHT. THE MARINE STRATUS MAY DEVELOP IN PORTIONS  
OFTHE UMPQUA DIVIDE TOWARDS DAYBREAK SUNDAY, BUT WERE NOT EXPECTING  
THE LOWER CONDITIONS TO MOVE INTO ROSEBURG.  
 
ELSEWHERE, VFR CONDITIONS WILL CONTINUE THROUGH THE TAF PERIOD.  
-PETRUCELLI  
 

 
   
MARINE...UPDATED 200 PM PDT SATURDAY 17 AUGUST 2019
 
A STRONG  
THERMAL TROUGH PATTERN WILL CONTINUE THROUGH THIS EVENING, THEN  
SLOWLY WEAKEN SUNDAY. THIS WILL PRODUCE STRONG NORTH WINDS AND  
CHOPPY WIND DRIVEN SEAS ACROSS THE AREA, PEAKING LATE THIS AFTERNOON  
AND EVENING. GALES AND VERY STEEP SEAS ARE EXPECTED SOUTH OF GOLD  
BEACH. WINDS AND SEAS WILL EXCEED SMALL CRAFT CRITERIA OVER MOST OF  
THE REMAINDER OF THE AREA. WINDS WILL DIMINISH INTO SUNDAY, BUT  
THERE WILL STILL BE SIGNIFICANT FRESH NORTHWEST SWELL OVER THE  
WATERS AND MOST OF THE AREA WILL REMAIN HAZARDOUS TO SMALL CRAFT.  
SEAS WILL SUBSIDE FURTHER INTO MONDAY. WINDS AND SEAS SHOULD BE  
BELOW SMALL CRAFT ADVISORY LEVELS MONDAY MORNING THROUGH TUESDAY.  
FROM WEDNESDAY INTO THURSDAY A MIXTURE OF TWO SWELLS MAY BRING THE  
RETURN OF CONDITIONS HAZARDOUS TO SMALL CRAFT. KEENE/BR-Y  
 

 
   
PREV DISCUSSION
 
/ISSUED 430 PM PDT SAT AUG 17 2019/  
 
UPDATED AVIATION DISCUSSION.  
 
SHORT TERM...AN UPPER LEVEL RIDGE IS CENTERED OFFSHORE AND IS  
LOCATED SURFACE THERMAL TROUGH ALONG THE COAST. THIS PATTERN IS  
BRINGING CLEAR SKIES AND WARM AND DRY CONDITIONS TO THE AREA TODAY.  
A MILD CHETCO EFFECT CONTINUES TODAY IN THE BROOKINGS AREA WITH  
DAYTIME TEMPERATURES IN THE 80S. THE UPPER RIDGE WILL WEAKEN  
SLIGHTLY ON SUNDAY AS AN UPPER TROUGH MOVES DOWN OVER BRITISH  
COLUMBIA BUT WARM AND DRY CONDITIONS WILL REMAIN IN PLACE ACROSS  
INLAND AREAS. AT THE COAST, THE SURFACE THERMAL TROUGH WILL WEAKEN  
TONIGHT INTO SUNDAY. THE UPPER RIDGE WILL SHIFT INLAND OVER  
REGION ON MONDAY THEN REMAIN IN PLACE ON TUESDAY AS A FRONTAL  
SYSTEM APPROACHES FROM THE WEST.  
 
WITH THE THERMAL TROUGH WEAKENING ALONG THE COAST TONIGHT AND  
SUNDAY, EXPECT LIGHTER WINDS AT THE COAST AND OVER THE COASTAL  
MOUNTAINS. MARINE LOW STRATUS AND PATCHY FOG IS EXPECTED TO  
DEVELOP TONIGHT AND PERSIST INTO SUNDAY MORNING, ESPECIALLY FOR  
AREAS NORTH OF CAPE BLANCO AND FROM BROOKINGS SOUTH. LOW CLOUDS  
ARE ALSO EXPECTED TO SPREAD INTO THE UMPQUA BASIN LATE TONIGHT AND  
SUNDAY MORNING. THESE LOW CLOUDS WILL GRADUALLY CLEAR IN THE LATE  
MORNING. AREAS NEAR BROOKINGS ARE NOT EXPECTED TO SEE A CHETCO  
EFFECT TOMORROW AND WILL SEE A RETURN TO NEAR NORMAL TEMPERATURES  
ON SUNDAY DUE TO WEAKENING OF THE OFFSHORE FLOW/ THERMAL TROUGH  
PATTERN.  
 
INLAND, EXPECT CONTINUED WARM AND DRY WEATHER ON SUNDAY WITH HIGH  
TEMPERATURES SIMILAR TO TODAY FOR MOST AREAS. BREEZY TO GUSTY  
SOUTHWEST TO WEST WINDS ARE EXPECTED EAST OF THE CASCADES ALONG  
WITH GUSTY SOUTH WINDS IN THE SHASTA VALLEY ON SUNDAY.  
 
MONDAY AND TUESDAY, THE WARM AND DRY WEATHER PATTERN CONTINUES.  
HIGH TEMPERATURES MAY TREND SLIGHTLY WARMER FOR INLAND AREAS AS  
THE UPPER RIDGE STRENGTHENS OVER THE AREA ON TUESDAY. THEN MODELS  
CONTINUE TO SHOW A FRONTAL SYSTEM APPROACHING THE COAST LATE  
TUESDAY.  
 
LONG TERM...WEDNESDAY THROUGH SATURDAY...TWO FRONTS WILL MOVE  
TOWARDS THE AREA BUT WEAKEN AND DISSIPATE AS THEY MOVE INLAND  
INTO THE RIDGE. SO EXPECT INLAND AREAS TO CONTINUE TO SEE WARM AND  
DRY CONDITIONS. COASTAL AREAS WILL SEE INCREASED CLOUDS WITH  
THESE FRONTS.  
 
MODELS ARE SHOWING FAIRLY GOOD AGREEMENT THAT THE FIRST OF THESE  
FRONTS WILL ARRIVE LATE WEDNESDAY. THIS FRONT IS EXPECTED TO  
WEAKEN AS IT MOVES ONSHORE AND INTO THE RIDGE. SOME LIGHT DRIZZLE  
OR SHOWERS ARE POSSIBLE NEAR THE COAST, MAINLY NORTH OF CAPE  
BLANCO, WEDNESDAY EVENING AND NIGHT. OTHERWISE, EXPECT WARM AND  
DRY WEATHER TO CONTINUE OVER THE AREA ON WEDNESDAY AND THURSDAY.  
ANOTHER FRONT MAY APPROACH THE COAST LATE FRIDAY INTO SATURDAY.  
MODELS INDICATE THIS FRONT MAY BE WEAKER THAN THE FIRST FRONT. SO  
HAVE KEPT DRY WEATHER IN THE FORECAST FOR THIS PERIOD, INCLUDING  
AT THE COAST.  
 
FIRE WEATHER...UPDATED 200 PM PDT SATURDAY 7 AUGUST 2019...WARM  
AND DRY CONDITIONS ARE EXPECTED ACROSS THE AREA FOR THE NEXT  
SEVERAL DAYS. TEMPERATURES WILL REMAIN STABLE THROUGH MONDAY  
BEFORE BECOMING A BIT HOTTER BY TUESDAY INTO FRIDAY. GUSTY WINDS  
WITH LOW HUMIDITIES WILL BE SEEN FOR A SHORT PERIOD SUNDAY  
AFTERNOON IN THE SHASTA VALLEY AND EAST OF THE CASCADES, BUT ARE  
EXPECTED TO REMAIN BELOW RED FLAG CRITERIA.  
 
CONFIDENCE IN THE LONG TERM FORECAST REMAINS LOW, BUT MODELS ARE  
SHOWING A DISTINCT TREND TOWARDS CONTINUING DRY AND WARM CONDITIONS  
FOR NEXT WEEK, WITH ABOVE NORMAL TEMPERATURES RESULTING FROM A  
BUILDING RIDGE ALOFT. THERE ARE A FEW INDICATIONS THAT A WEAK  
IMPULSE COULD PASS THROUGH THE REGION WITH INSTABILITY PRODUCING AN  
INCREASED RISK FOR THUNDER THURSDAY, BUT MID LEVEL MOISTURE IS TOO  
LOW FOR ANY DECENT VERTICAL DEVELOPMENT AT THIS TIME. -SVEN  
 

 
   
MFR WATCHES/WARNINGS/ADVISORIES
 
 
OR...SMALL CRAFT ADVISORY UNTIL 5 AM PDT SUNDAY FOR ORZ021.  
 
CA...NONE.  
 
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 5 PM PDT SUNDAY FOR  
PZZ350-356-370-376.  
GALE WARNING UNTIL 5 AM PDT SUNDAY FOR PZZ356-376.  
 

 
 
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