407  
FXUS66 KMFR 182146  
AFDMFR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEDFORD OR  
246 PM PDT FRI SEP 18 2020  
   
DISCUSSION
 
THE UPPER LOW IS MOVING ONSHORE. THE LOCATION OF THE  
UPPER LOW IS OVER THE NORTHWEST PART OF THE FORECAST AREAS  
(NORTHWEST COOS COUNTY) AND THIS WILL CONTINUE TO MOVE NORTHEAST  
THIS AFTERNOON THROUGH TONIGHT. THE LATEST SATELLITE IMAGE CLEARLY  
SHOWS MOST OF THE ENERGY OUT AHEAD OF THE UPPER LOW (LIKE A  
PINWHEEL) WHICH PUTS MOST OF THE ACTION IN TERMS OF SHOWERS AND  
THUNDERSTORMS NORTH OF OUR FORECAST AREA. HOWEVER SCATTERED SHOWERS  
AND ISOLATED STORMS ARE STILL A GOOD BET FOR MOST OF DOUGLAS COUNTY  
AND NORTHERN CASCADES FROM ABOUT CRATER LAKE NORTH. THESE AREAS ALSO  
HAVE THE BEST CHANCE OF GETTING MODERATE TO HEAVY SHOWERS INTO EARLY  
THIS EVENING. THERE IS STILL CONCERN FOR MODERATE TO HEAVY RAIN IN A  
SHORT PERIOD OF TIME TO SET UP NEAR OR OVER THE BURN SCARS OVER THE  
ARCHIE CREEK FIRE AND A FLASH FLOOD WATCH HAS BEEN ISSUED. PLEASE  
SEE FFAMFR FOR MORE DETAILS.  
 
ONCE AGAIN WE WANT TO REMIND THE FOLKS OUT THERE OUR RADAR AT KMAX  
IS CURRENTLY UNDERGOING THE SERVICE LIFE EXTENSION PROGRAM AND IS  
NOT PROVIDING DATA. THE DATA PRESENTED ON OUR WEBSITE ARE FROM  
SEPTEMBER 14TH. IF YOU FIND YOURSELF IN THE UNLIKELY POSITION OF  
BEING WITHIN A WARNING AREA, YOU WILL NOT FIND ANY CURRENT RADAR  
DATA FROM KMAX TO COMPARE THE WARNING TO. WE ALREADY HAVE THE GOES  
WEST MESOSECTOR 1 PROVIDING US AND YOU WITH UP TO THE MINUTE  
SATELLITE DATA. TRUST THAT YOU ARE INDEED IN A WARNING AREA AND TAKE  
THE PRECAUTIONS YOU NEED TO KEEP YOURSELF SAFE BEFORE LOOKING FOR  
OTHER DATA.  
 
THE UPPER LOW WILL PROGRESS THROUGH THE AREA TONIGHT AND WILL BE  
EAST OF THE CASCADES BY EARLY SATURDAY MORNING. SHOWERS AND ISOLATED  
STORMS WILL DIMINISH THIS EVENING WITH SHOWERS GRADUALLY DIMINISHING  
IN COVERAGE OVERNIGHT TONIGHT. SHOWERS WILL LINGER MAINLY NORTH OF  
THE UMPQUA DIVIDE AND CASCADES TONIGHT.  
 
THE UPPER TROUGH MOVES EAST OF OUR AREA SATURDAY MORNING WITH WEAK  
RIDGING BUILDING FROM THE WEST. COULD NOT RULE OUT A FEW SHOWERS  
NORTH OF THE UMPQUA DIVIDE AND NORTHERN CASCADES UNTIL ABOUT THE MID  
MORNING HOURS SATURDAY, OTHERWISE IT WILL BE DRY WITH MILDER  
TEMPERATURES IN THE AFTERNOON FOR MOST INLAND LOCATIONS.  
 
SUNDAY, A WEAK THERMAL TROUGH WILL SET UP ALONG THE COAST WITH  
INCREASING OFFSHORE FLOW IN SOUTHWEST OREGON, BUT WINDS WILL NOT BE  
STRONG, EVEN OVER THE MID SLOPES AND RIDGES AND WILL BE SHORT LIVED.  
 
BEYOND SUNDAY, IT SHOULD REMAIN DRY THROUGH AT LEAST THE MIDDLE OF  
NEXT WEEK. A WEAK UPPER TROUGH AND COLD FRONT APPROACHES THE AREA  
MONDAY, BUT THE MAIN EFFECT WILL BE INCREASING ONSHORE FLOW NEAR AND  
AT THE COAST AND COOLER AFTERNOON TEMPERATURES FOR MOST INLAND  
LOCATIONS. A STRONGER FRONT WILL ARRIVE NEXT THURSDAY. UNLIKE THE  
LAST FRONT FROM EARLIER THIS WEEK AND YESTERDAY, WE WON'T HAVE A  
STRONG UPPER RIDGE IN PLACE, INSTEAD WE'LL HAVE A WEST TO SOUTHWEST  
FLOW WITH THE RIDGE SOUTH OF OUR AREA. THEREFORE THERE IS A BETTER  
OPPORTUNITY FOR THE FRONT TO HOLD TOGETHER AND NOT WEAKEN, THUS  
RESULTING IN A HIGHER CHANCE FOR MEASURABLE RAIN.  
 
THE FRONT WILL MOVE THROUGH THE AREA THURSDAY NIGHT FOLLOWED BY AN  
UPPER TROUGH FRIDAY WITH THE CHANCE FOR POST FRONTAL SHOWERS.  
-PETRUCELLI  
 

 
   
AVIATION...FOR THE 18/18Z TAFS
 
OVER THE COASTAL WATERS AND ALONG  
THE COAST...WIDESPREAD MVFR CIGS WITH SHOWERS WILL PERSIST INTO  
THIS EVENING, THEN SHOWERS END, BUT MVFR/IFR PREVAILS OVERNIGHT  
INTO SATURDAY MORNING.  
 
INLAND AREAS FROM THE CASCADES WEST...WILDFIRE SMOKE COVERAGE WILL  
DECREASE THROUGH THIS EVENING, BUT EXPECT SHOWERS AND ISOLATED  
THUNDERSTORMS TO OCCASIONALLY LOWER CONDITIONS TO MVFR/IFR THROUGH  
THIS EVENING. AREAS OF HIGHER TERRAIN WILL ALSO BE OBSCURED.  
 
EAST OF THE CASCADES...VFR CONDITIONS WILL PREVAIL THROUGH SATURDAY  
MORNING EXCEPT FOR LOCAL MVFR VSBYS IN SMOKE AND HAZE. GUSTY WEST  
WINDS WILL DEVELOP THIS AFTERNOON AND EVENING, DIMINISHING  
OVERNIGHT. ISOLATED SHOWERS AND ISOLATED THUNDERSTORMS ARE  
EXPECTED THIS AFTERNOON/EVENING, FOCUSED IN THE WESTERN PART OF THE  
AREA. ANY SHOWERS WILL END TONIGHT. -SPILDE  
NIGHT.  
 

 
   
MARINE...UPDATED 200 PM PDT FRIDAY 18 SEPTEMBER 2020
 
RELATIVELY  
CALM CONDITIONS WITH LIGHT SOUTH WINDS AND SEAS GENERALLY AT OR  
BELOW 5 FEET WILL CONTINUE THROUGH SATURDAY MORNING. A THERMAL  
TROUGH WILL BUILD NEAR THE COAST LATE SATURDAY INTO SUNDAY,  
PRODUCING GUSTY NORTH WINDS AND CHOPPY WIND DRIVEN SEAS SOUTH OF  
CAPE BLANCO. ALTHOUGH CONDITIONS ARE EXPECTED TO REMAIN  
BELOW ADVISORY CRITERIA, WINDS WILL BE STRONGEST BEYOND 5 NM FROM  
SHORE. THE THERMAL TROUGH WILL WEAKEN MONDAY AND WINDS AND SEAS  
WILL SUBSIDE AT THAT TIME. SUB-ADVISORY CONDITIONS ARE THEN  
EXPECTED THROUGH TUESDAY, THEN NORTHWEST SWELL WILL INCREASE  
WEDNESDAY AS A NEW SERIES OF FRONTS APPROACHES THE AREA. -SPILDE  
 

 
 
UPDATED 230 PM PDT FRIDAY 18 SEPTEMBER  
2020...EAST OF THE CASCADES, SOME VERY BREEZY WINDS TO 40 MPH ARE  
OCCURING, ESPECIALLY AT THE HIGHER ELEVATIONS. MEANWHILE, 20-25  
MPH WIND GUSTS ARE EXPECTED AT SOME OF THE MEDIUM ELEVATIONS.  
ELSEWHERE, SHOWERS AND A COUPLE OF THUNDERSTORMS ARE EXPECTED THIS  
AFTERNOON AND EVENING. THE WETTEST STORMS WILL BE NORTH OF THE  
UMPQUA DIVIDE AND ALONG AND WEST OF THE CASCADES WHICH COULD STILL  
PUT DOWN SOME WETTING RAIN, ESPECIALLY THE FARTHER NORTH ONE  
GOES. SOUTH OF THE UMPQUA DIVIDE THE CHANCES FOR WETTING RAINS ARE  
SHARPLY DECREASING, AND SOME OF OUR WEST SIDE VALLEYS (ROGUE  
VALLEY) MAY NOT EVEN GET MEASURABLE RAIN, LET ALONE AREAS EAST OF  
THE CASCADES. REGARDLESS, WE WILL KEEP LAL 2 FOR MUCH OF THE AREA  
ON THE OFF CHANCE THAT A STRAY THUNDERSTORM DEVELOPS.  
 
THE UPPER LOW CAUSING THESE SHOWERS AND A FEW STORMS WILL EXIT THE  
AREA QUICKLY OVERNIGHT ALLOWING THINGS TO CLEAR UP AND BEGIN DRYING  
OUT TOMORROW (A FEW LINGERING LIGHT SHOWERS ARE POSSIBLE SATURDAY  
MORNING FOR THE UMPQUA BASIN AND THE CASCADES NORTH OF CRATER LAKE).  
THEN, LIGHT EAST WINDS ON SATURDAY NIGHT WILL ALLOW THINGS TO DRY  
OUT TOWARD NORMAL FOR THIS TIME OF YEAR. TEMPERATURES WILL ALSO  
CLIMB TO BE NEAR NORMAL BY SUNDAY. OUR DRY WEATHER WILL CONTINUE  
INTO NEXT WEEK, BUT CRITICAL CONDITIONS ARE NOT EXPECTED. A FRONT  
TOWARD THE END OF THE WEEK COULD BE A BIT MORE PROMISING FOR  
RAINFALL THAN THIS SYSTEM; BUT THINGS ARE LIKELY TO CHANGE BETWEEN  
NOW AND THEN. -SCHAAF  
 

 
   
MFR WATCHES/WARNINGS/ADVISORIES
 
 
OR...FLASH FLOOD WATCH UNTIL 8 PM PDT THIS EVENING FOR ORZ023-025.  
 
CA...NONE.  
 
PACIFIC COASTAL WATERS...NONE.  
 

 
 
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