914  
FXUS66 KMFR 120417  
AFDMFR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEDFORD OR  
917 PM PDT SUN APR 11 2021  
   
UPDATE
 
AN UPDATE TO THE FORECAST IS NOT NECESSARY. SKIES WILL  
REMAIN CLEAR OVERNIGHT WITH LOWS GENERALLY A FEW DEGREES ABOVE THE  
VALUES FROM THIS MORNING. BUT, THAT WILL STILL BE A FEW TO SEVERAL  
DEGREES BELOW NORMAL. A FROST ADVISORY REMAINS IN EFFECT FOR THE  
EARLY MORNING HOURS IN THE COQUILLE VALLEY AND ALONG THE COAST OF  
COOS AND DOUGLAS COUNTIES.  
 
THE RECENT PATTERN OF DRY WEATHER WITH GENERALLY BELOW NORMAL LOW  
TEMPERATURES AND ABOVE NORMAL HIGH TEMPERATURES WILL LIKELY  
CONTINUE THROUGH THE UPCOMING WEEKEND.  
 
ARGUABLY THE MOST IMPACTFUL PORTION OF THE FORECAST WILL BE  
ASSOCIATED WITH A TROUGH RETROGRADING FROM THE ROCKIES NOW INTO  
EASTERN OREGON BY TUESDAY. EAST-SIDE NORTHEAST WINDS WILL LIKELY  
REACH A PEAK TUESDAY INTO TUESDAY EVENING WITH GUSTS OF 25 TO 40  
MPH, WITH WEST-SIDE GUSTS REACHING 15 TO 30 MPH.  
 
THIS WILL ALSO BRING AN INCREASE OF MAINLY MID-LEVEL MOISTURE TO  
THE EAST SIDE. VIRGA IS A GOOD BET WITH DRY AIR AT THE LOW LEVELS.  
BUT, THE HIGHEST PROBABILITY OF LIGHT SHOWERS SURVIVING TO THE  
GROUND IS IN LAKE AND MODOC COUNTIES. AS IS TYPICAL WITH CLOSED  
LOWS...THERE IS A MODERATE AMOUNT OF VARIABILITY IN JUST HOW FAR  
SOUTH AND WEST THE TROUGH WILL TRACK, AND HOW MUCH MOISTURE WILL  
BE AVAILABLE. BUT, WE COULD ENVISION COVERING A LONGER DURATION  
AND WIDER SWATH OF LAKE AND MODOC COUNTIES WITH AT LEAST A SLIGHT  
CHANCE OF SHOWERS TUESDAY THROUGH WEDNESDAY. A FEW RUMBLES OF  
THUNDER ARE ALSO WITHIN THE REALM OF POSSIBILITY FOR THE FAR EAST  
SIDE DURING PEAK HEATING OF LATE TUESDAY AFTERNOON.  
 

 
   
AVIATION...FOR THE 12/00Z TAF CYCLE
 
VFR WILL CONTINUE THROUGH  
MONDAY NIGHT. GUSTY NORTH WINDS AT 20 TO 35 KT ARE EXPECTED ALONG  
THE COAST THROUGH THIS EVENING AND AGAIN MONDAY AFTERNOON AND  
EVENING, INCLUDING KOTH. NORTH WINDS WILL ALSO BE GUSTY UP TO 20 KT  
IN THE UMPQUA BASIN, INCLUDING KRBG, EARLY THIS EVENING AND MONDAY  
AFTERNOON INTO EARLY EVENING. -DW  
 

 
   
MARINE...UPDATED 815 PM PDT SUNDAY, 11 APR 2021
 
MODERATE TO  
STRONG WINDS AND STEEP TO VERY STEEP SEAS ARE EXPECTED THROUGH  
MONDAY NIGHT. NORTHERLY GALES WILL AFFECT AREAS GENERALLY BEYOND 5NM  
FROM SHORE SOUTH OF CAPE BLANCO WHILE MOST OF THE REMAINING COASTAL  
WATERS WILL BE IMPACTED BY VERY STEEP AND HAZARDOUS WARNING LEVEL  
SEAS. WINDS AND SEAS WILL BE AT THEIR HIGHEST DURING THE AFTERNOONS  
AND EVENINGS THROUGH MONDAY EVENING. SOME HIGH RESOLUTION MODELS  
KEEP WINDS GUSTY ALL THE WAY TO THE COASTLINE THROUGH MONDAY NIGHT,  
AND THUS WE EXPANDED THE HAZARDOUS SEAS WARNING TO COVER MOST OF THE  
WATERS THROUGH MONDAY NIGHT.  
 
WINDS ARE EXPECTED TO DIMINISH TUESDAY BUT WILL TICK UPWARDS AGAIN  
ON TUESDAY AFTERNOON, LIKELY KEEPING SMALL CRAFT ADVISORY CONDITIONS  
FOR MOST AREAS, WITH HAZARDOUS SEAS REMAINING POSSIBLE GENERALLY  
SOUTH OF GOLD BEACH BEYOND 10NM FROM SHORE.  
 
IT'S LIKELY THAT WINDS AND SEAS FINALLY DIP BELOW SMALL CRAFT  
ADVISORY LEVEL FOR ALL AREAS BY THURSDAY. -SPILDE/KEENE  
 

 
   
PREV DISCUSSION
 
/ISSUED 248 PM PDT SUN APR 11 2021/  
 
SHORT TERM...THIS AFTERNOON THROUGH TUESDAY NIGHT...WITH HIGH  
PRESSURE ALOFT AND A THERMAL TROUGH AT THE SURFACE, SKIES ARE  
CLEAR ACROSS THE AREA THIS AFTERNOON. THE THERMAL TROUGH IS  
BRINGING ENHANCED AFTERNOON BREEZES TODAY, WITH GUSTY WINDS ALONG  
THE COAST AND ACROSS THE HIGHER TERRAIN. AFTERNOON TEMPERATURES  
TODAY WILL BE AROUND 5 TO 10 DEGREES WARMER THAN WHAT OCCURRED  
YESTERDAY. DRY CONDITIONS AND CLEAR SKIES WILL CONTINUE THIS  
EVENING AND OVERNIGHT AND ANOTHER CHILLY NIGHT IS EXPECTED ACROSS  
THE REGION. ALTHOUGH OVERNIGHT TEMPERATURES WILL BE WARMER THAN  
LAST NIGHT, VALUES WILL STILL BE CONDUCIVE FOR FROST POTENTIAL  
ALONG THE COAST NORTH OF CAPE BLANCO AND INTO THE COQUILLE BASIN.  
AS SUCH, HAVE ISSUED A FROST ADVISORY FOR THAT AREA FOR TONIGHT,  
AND DETAILS CAN BE FOUND AT NPWMFR. THE REMAINDER OF THE AREA WILL  
BE WARMER BY AROUND 3 TO 5 DEGREES, SO WE AREN'T EXPECTING ANY  
WIDESPREAD FREEZE CONDITIONS FOR WEST SIDE VALLEYS TONIGHT.  
CONDITIONS ON MONDAY WILL BE QUITE SIMILAR TO THOSE OF TODAY,  
ALTHOUGH AFTERNOON TEMPERATURES WILL TREND HIGHER BY ANOTHER 5 TO  
10 DEGREES.  
 
MONDAY EVENING INTO TUESDAY, AN UPPER LEVEL TROUGH DIGS OVER THE  
PACIFIC NORTHWEST AND LINGERS THROUGH MUCH OF THE WEEK. THIS WILL BE  
AN "INSIDE SLIDER" SO THERE WON'T BE MUCH MOISTURE ASSOCIATED WITH  
IT DUE TO THE MOSTLY OVER LAND TRAJECTORY. CONDITIONS SHOULD REMAIN  
LARGELY DRY, HOWEVER, A DECENT AMOUNT OF ENSEMBLES, BOTH THE GEFS  
AND EC, SHOW SOME LIGHT PRECIPITATION (<0.02") OVER FAR EASTERN  
PORTIONS OF LAKE AND MODOC COUNTIES ON TUESDAY AFTERNOON. GIVEN THE  
MOSTLY OVER LAND TRAJECTORY, AND PRECEDING DRY AIR MASS, AM  
SKEPTICAL THAT ANY PRECIPITATION WILL MAKE IT TO THE GROUND.  
HOWEVER, THERE IS SOME OVER WATER TRAJECTORY WHICH WOULD ALLOW FOR  
SOME MOISTURE TO BE ENTRAINED IN THE SYSTEM, AND GIVEN THE AMOUNT OF  
ENSEMBLE SHOWING THE POSSIBILITY, HAVE LEFT IN A SLIGHT CHANCE  
POPS ACROSS FAR EASTERN PORTIONS OF MODOC COUNTY. THE MORE NOTICEABLE  
ELEMENT OF THIS UPPER LEVEL TROUGH WILL BE GUSTY WINDS ON TUESDAY.  
IT WILL BE BREEZY EVERYWHERE IN THE FORECAST AREA TUESDAY, BUT  
ESPECIALLY SO ACROSS THE EAST SIDE WHERE GUSTS OF 25 TO 35 MPH WILL  
BE COMMON. THE TRAJECTORY OF THIS LOW BRINGS THE STRONGEST 700 MB  
WINDS OVER THE COASTAL WATERS, AND WITH 700 MB WINDS ACROSS THE EAST  
SIDE LIMITED TO 25 TO 30 KT, WIND SPEEDS SHOULD REMAIN BELOW  
ADVISORY CRITERIA. IT SHOULD BE NOTED, HOWEVER, THAT IT HAS BEEN  
QUITE SOME TIME SINCE THE AREA HAS RECIEVED WETTING RAINS (ABOUT  
THREE WEEKS) AND THESE STRONG WINDS WILL BE COUPLED WITH MINIMUM  
HUMIDITIES SIMILAR TO SUMMER-TIME VALUES. GIVEN THE DRY STATE OF  
THINGS, USE CAUTION IF DEALING WITH ANYTHING THAT COULD POTENTIALLY  
START A FIRE. WINDS WILL EASE TUESDAY NIGHT, BUT LOW PRESSURE  
REMAINS OVER THE REGION AS WE HEAD INTO THE EXTENDED. /BR-Y  
 
LONG TERM...WEDNESDAY THROUGH SUNDAY...THE GUSTY WINDS ON THE EAST  
SIDE WILL BEGIN TO CALM AS THE LOW PRESSURE SYSTEM STALLS AND  
WEAKENS. VERY DRY HUMIDITIES WILL, HOWEVER, CONTINUE SINCE WE WILL  
REMAIN IN NORTH TO NORTHEAST FLOW. THIS PERIOD OF MILD TO WARM, DRY,  
AND BREEZY CONDITIONS WILL CONTINUE TO ERODE SNOWPACK FOR MOST OF  
THE EXTENDED FORECAST TIMEFRAME.  
 
THE OVERALL FORECAST WE ARE CREATING SHOWS LITTLE DIFFERENCE BETWEEN  
RUNS. YESTERDAY, I MENTIONED A POTENTIAL TRADE-OFF BETWEEN SHOWERS  
AND STORMS AND THE GUSTY WINDS AND VERY LOW HUMIDITIES. THIS WAS  
BASED ON THE TRACK OF THE LOW AND ITS WESTWARD SHIFT IN TRACK.  
THINGS LOOK VERY SIMILAR TODAY, AND THE BEST CHANCE FOR  
PRECIPITATION TO OCCUR IN THE EXTENDED IS TUESDAY NIGHT INTO EARLY  
WEDNESDAY MORNING. THIS WOULD LOOK LIKE SHOWERS AND A POSSIBLE  
THUNDERSTORM OVER THE WARNER MOUNTAIN IN MODOC COUNTY, BUT AM STILL  
NOT OF THE BELIEF THAT THE SLIGHT WESTWARD TRACK WOULD BE ENOUGH TO  
 
1.) PROVIDE ENOUGH MOISTURE TO INITIATE CLOUD COVER OR CONVECTION.  
2.) OVERCOME THE VERY DRY AIR MASS NEAR THE SURFACE FROM THE  
RESULTANT EASTERLY FLOW. THIS MEANS THAT ANY PRECIPITATION WOULD  
EVAPORATE BEFORE REACHING THE GROUND.  
 
THEREFORE, HAVE CONTINUED THE DRIER AND BREEZIER PORTION OF THE  
NATIONAL BLEND OF MODELS THAT INCORPORATES THE ECMWF ENSEMBLES FOR  
NOW. -SCHAAF  
 

 
   
MFR WATCHES/WARNINGS/ADVISORIES
 
 
OR...FROST ADVISORY FROM 2 AM TO 9 AM PDT MONDAY FOR ORZ021.  
 
CA...NONE.  
 
PACIFIC COASTAL WATERS...GALE WARNING UNTIL 5 AM PDT TUESDAY FOR  
PZZ356-376.  
HAZARDOUS SEAS WARNING UNTIL 5 AM PDT TUESDAY FOR  
PZZ350-356-370-376.  
SMALL CRAFT ADVISORY UNTIL 5 AM PDT TUESDAY FOR PZZ350.  
 

 
 
DW/MAS/BR-Y  
 
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