813  
FXUS66 KMFR 201525  
AFDMFR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEDFORD OR  
825 AM PDT SUN AUG 20 2017  
   
UPDATE
 
THE OVERALL FORECAST FOR TODAY SEEMS TO BE MOSTLY ON  
TRACK AS CURRENT OBSERVATIONS ARE MATCHING THE FORECAST. THAT  
BEING SAID, EXTREMELY SMOKY SKIES WERE OBSERVED ENROUTE TO THE  
OFFICE TODAY, AND THE ONGOING WILDFIRES WILL LIKELY TO CONTINUE TO  
PRODUCE MORE SMOKE WHICH WILL BE BLOWN INTO THE WEST SIDE VALLEYS  
AS FORECAST. THIS AFFECTED THE OFFICIAL HIGH TEMPERATURE READINGS  
YESTERDAY, AND WILL LIKELY DO THE SAME AGAIN TODAY. THUS HAVE  
LOWERED THE TEMPERATURE FORECAST FOR THE ROGUE VALLEY, ILLINOIS  
VALLEY, AND ROSEBURG FOR TODAY.  
 
OTHERWISE, THE MAIN CONCERNS FOR THIS FORECAST CYCLE ARE GOING TO  
BE THE WILDFIRE CONDITIONS AROUND THE AREA--INCLUDING THUNDERSTORM  
CHANCES THIS WEEK, AND SKY AND SMOKE COVER FOR TOMORROW MORNING'S  
ECLIPSE. AGAIN, SINCE THE FORECAST LOOKS ON TRACK, I DO NOT  
ANTICIPATE NEEDING TO MAKE EXTENSIVE CHANGES, AND HAVE LEFT THE  
PREVIOUS FORECAST BELOW WHICH DETAILS THE FORECAST PATTERN NICELY.  
-SCHAAF  
 

 
   
MARINE...UPDATED 815 AM PDT SUNDAY 20 AUGUST 2017
 
HIGH  
PRESSURE OFFSHORE AND A THERMAL TROUGH ALONG THE COAST WILL  
GENERATE MODERATE TO STRONG NORTH WINDS AND VERY STEEP SEAS  
THROUGH THIS EVENING. CONDITIONS WILL AT LEAST BE HAZARDOUS TO  
SMALL CRAFT OVER ALL OF THE FORECAST AREA, AND WARNING LEVEL  
WINDS/SEAS WILL OCCUR BEYOND 5 NM FROM SHORE FROM GOLD BEACH  
SOUTH. WINDS AND SEAS WILL BE HIGHEST THIS AFTERNOON AND EVENING,  
EASING DURING THE OVERNIGHT AND EARLY MORNING HOURS. THE THERMAL  
TROUGH WILL WEAKEN BEGINNING MONDAY, AND WINDS WILL DIMINISH BUT  
SEAS ARE EXPECTED TO REMAIN STEEP THROUGH THE MIDDLE OF THE WEEK  
DUE TO SHORT PERIOD SWELLS. HAVE EXTENDED THE WARNINGS AND  
ADVISORIES IN THE MORNING UPDATE TO ACCOUNT FOR THIS.  
-SANDLER/SCHAAF  
 

 
   
PREV DISCUSSION
 
/ISSUED 501 AM PDT SUN AUG 20 2017/  
 
DISCUSSION...THE MAIN CONCERN THIS MORNING IS ON-GOING STRONG,  
GUSTY NORTHEAST WINDS AND LOW HUMIDITY AFFECTING THE CHETCO BAR  
WILDFIRE. A RED FLAG WARNING /PDXRFWMFR/ REMAINS IN EFFECT UNTIL  
NOON. THE QUAIL PRAIRIE OBSERVATION SITE IN THE VICINITY OF THE  
FIRE HAS HAD GUSTS OF 20 TO 25 MPH OVERNIGHT. MEANWHILE, RED  
MOUND (A RIDGE TOP SITE NEARER TO BROOKINGS) HAS HAD GUSTS OF 30  
TO 40 MPH. THE GOOD NEWS IS THAT THESE WINDS ARE LIKELY NEAR A  
PEAK, BUT NORTHEAST GUSTS WILL REMAIN STRONG THIS MORNING THEN  
CONTINUE AT 15 TO 20 MPH THIS AFTERNOON THROUGH TONIGHT WITH A  
MODEST IMPROVEMENT IN HUMIDITY RECOVERY OF ABOUT 10% HIGHER THAN  
THIS MORNING. MORE SUBSTANTIAL IMPROVEMENT WILL COME WITH A CHANGE  
TO LIGHT ONSHORE WINDS DURING THE DAY ON MONDAY.  
 
THE OTHER MAIN ITEMS OF INTEREST ARE PERSISTENT SMOKY SKIES OVER  
MUCH OF OUR AREA, ECLIPSE VIEWING CONDITIONS ON MONDAY MORNING,  
AND THE POTENTIAL FOR NEW FIRE STARTS (MAINLY SOUTHWARD AND  
EASTWARD FROM THE SOUTHERN OREGON SISKIYOU AND CASCADE MOUNTAINS)  
DUE TO LIGHTNING ON TUESDAY AND WEDNESDAY.  
 
THE PATH OF TOTALITY WILL BE NORTH OF OUR AREA, BUT THERE WILL BE  
MANY VIEWING THE PARTIAL ECLIPSE (WITH CERTIFIED EYE WEAR). THERE  
IS STILL HIGH CONFIDENCE THAT CLOUD COVER WILL BE LIMITED TO  
DISSIPATING STRATUS...RETREATING TO THE BEACHES NORTH OF CAPE  
BLANCO, AND A FEW HIGH LEVEL CLOUDS OVER SOUTHERN MODOC COUNTY.  
BUT, SMOKE WILL MAKE FOR FILTERED VIEWING OVER THE ENTIRE AREA.  
 
HIGHS WILL BE SEVERAL DEGREES HIGHER TODAY AS A WEAK TROUGH EXITS  
THE PACIFIC NORTHWEST AND OFFSHORE HIGH PRESSURE NUDGES INTO THE  
REGION. THE OTHER MAIN UPPER LEVEL FEATURE TO AFFECT OUR WEATHER  
IS A CLOSED LOW OFFSHORE FROM SOUTHERN CALIFORNIA. IT WILL SEND  
GRADUALLY INCREASING AMOUNTS OF MID-LEVEL MOISTURE NORTHWARD WITH  
A FEW AFTERNOON CUMULUS CLOUDS LIKELY TO POP UP OVER THE HIGHER  
TERRAIN OF THE FAR SOUTHERN PORTIONS OF OUR AREA ON MONDAY  
AFTERNOON/EVENING.  
 
INSTABILITY WILL INCREASE ON TUESDAY WHILE INCREASED MOISTURE  
ROTATES NORTHWESTWARD INTO NORTHERN CALIFORNIA AND SOUTH CENTRAL  
OREGON. A LOWER BUT STILL SIGNIFICANT PROBABILITY OF THUNDERSTORMS  
WILL EXTEND TO THE SOUTHERN OREGON CASCADES AND SISKIYOU  
MOUNTAINS.  
 
A SIGNIFICANT PROBABILITY OF THUNDERSTORMS WILL ALSO EXIST ON  
WEDNESDAY. BUT, THE PATTERN WILL CHANGE FROM TUESDAY AS A BROAD  
LOW APPROACHES BRITISH COLUMBIA. THIS WILL SHIFT THE STEERING FLOW  
TO SOUTHWESTERLY BUT THE MAIN RISK WILL ONCE AGAIN BE FROM THE  
SISKIYOUS AND CASCADES SOUTHWARD AND EASTWARD.  
 
A COLD FRONTAL PASSAGE ASSOCIATED WITH THE TROUGH WILL BRING A  
SLIGHT CHANCE OF LIGHT DRIZZLE OR SHOWERS TO THE DOUGLAS AND COOS  
COUNTY COAST LATE WEDNESDAY NIGHT INTO THURSDAY MORNING. THE FRONT  
WILL BRING GUSTY AFTERNOON WINDS TO THE EAST SIDE, BUT ALSO THE  
COOLEST HIGH TEMPERATURE READINGS OF THE WEEK.  
 
THERE IS INCREASED MODEL AGREEMENT TOWARD RIDGING DEVELOPING OVER  
THE WEST COAST LATE IN THE WEEK INTO THE WEEKEND WITH A WARMING  
AND DRYING TREND.  
 
AVIATION...20/12Z TAF CYCLE...GUSTY NORTH TO NORTHEAST WINDS WILL  
CONTINUE IN THE COASTAL MOUNTAINS THROUGH SUNDAY WITH A PERSISTENT  
THERMAL TROUGH. PATCHES OF IFR/LIFR ARE POSSIBLE NORTH OF CAPE  
BLANCO, BUT THE MODELS SUGGEST MOSTLY CLEAR SKIES. EXPECT SIMILAR  
WIND SPEEDS WITH GUSTS OF 35 KT AT OTH AGAIN THIS AFTERNOON. NORTH  
WINDS ARE ALSO EXPECTED TO SURFACE AT RBG WITH GUSTS UP TO 25 KNOTS  
IN THE AFTERNOON.  
 
AREAS OF MVFR VISIBILITY CAN BE EXPECTED IN WILDFIRE SMOKE INLAND  
WITH LOCAL IFR IN THE IMMEDIATE VICINITY OF THE FIRES.  
-SANDLER  
 
FIRE WEATHER...UPDATED 305 AM SUNDAY, 20 AUGUST 2017...  
HIGH PRESSURE OFFSHORE AND A STRONG THERMAL TROUGH OVER CALIFORNIA  
WILL PRODUCE GUSTY NORTHWEST THROUGH NORTHEAST WINDS ONCE AGAIN  
ACROSS MUCH OF THE AREA THIS AFTERNOON INTO TONIGHT. CONDITIONS WILL  
BE MOST CRITICAL IN THE FAR SOUTHWESTERN OREGON COASTAL MOUNTAINS AS  
GUSTY NORTHEAST WINDS CONTINUE THROUGH SUNDAY MORNING. WINDS WILL  
WEAKEN SOME TODAY INTO EARLY MONDAY BUT STILL BE MODERATE. HUMIDITY  
RECOVERIES WILL STILL BE MODERATE TO POOR ON THE UPPER SLOPES AND  
RIDGES.  
 
LOWER ELEVATION WEST SIDE LOCATIONS WILL CONTINUE TO EXPERIENCE MID  
LEVEL HAINES 5 CONDITIONS THROUGH MONDAY WHERE THE INVERSION BREAKS,  
WHILE HIGHER ELEVATIONS EXPERIENCE MOSTLY HAINES 4 TO 5 WHERE THE  
INVERSION BREAKS.  
 
THE FLOW ALOFT WEAKENS AND SHIFTS TO SOUTHERLY MONDAY AS MOISTURE  
AND, THEN, INSTABILITY ARRIVE. THUNDERSTORMS WILL BE POSSIBLE  
TUESDAY AND WEDNESDAY FROM APPROXIMATELY THE CASCADES AND SISKIYOUS  
SOUTH AND EASTWARD. TUESDAY EVENING THROUGH WEDNESDAY MORNING SOME  
GUIDANCE IS INDICATING THE POSSIBILITY OF THUNDERSTORMS CRESTING THE  
SISKIYOUS AND WEST OF THE CASCADES, SO WE'LL CONTINUE TO KEEP AN EYE  
ON THIS. WEDNESDAY AFTERNOON AND EVENING THE THREAT BEGINS TO KICK  
OUT TO THE EAST AND IS JUST ABOUT OUT OF THE AREA THURSDAY AFTERNOON  
AND EVENING. -SANDLER  
 

 
   
MFR WATCHES/WARNINGS/ADVISORIES
 
 
OR...RED FLAG WARNING UNTIL NOON PDT TODAY FOR ORZ618-619.  
 
CA...NONE.  
 
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 5 PM PDT MONDAY FOR  
PZZ350-356-370-376.  
GALE WARNING UNTIL 11 PM PDT THIS EVENING FOR PZZ356.  
HAZARDOUS SEAS WARNING FROM 11 PM THIS EVENING TO 5 PM PDT  
MONDAY FOR PZZ356-376.  
GALE WARNING UNTIL 2 AM PDT MONDAY FOR PZZ376.  
 

 
 
BMS/DW/RES  
 
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