265  
FXUS66 KMFR 021544  
AFDMFR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEDFORD OR  
844 AM PDT THU JUL 2 2020  
   
DISCUSSION
 
NO CHANGES TO THE FORECAST AT THIS TIME.  
 
MARINE LAYER INDUCED STRATUS IS BURNING OFF IN AREAS OF DOUGLAS  
AND COOS COUNTY. EXPECT CLOUDLESS SKIES, BUT MILD TEMPERATURES.  
REMEMBER THAT AT THIS TIME OF THE YEAR THE SUN'S INTENSITY IS  
QUITE STRONG, SO EVEN IF IT DOESN'T FEEL HOT, TO TAKE ACTION TO  
PREVENT SUNBURN.  
 
WE ARE STILL ANTICIPATING AFTERNOON BREEZES FOR INLAND AREAS, BUT  
THEY SHOULD BE WEAKER THAN THE PAST FEW AFTERNOONS. BEYOND THIS,  
PLEASE REFER TO THE PREVIOUS DISCUSSION FOR EXPANDED DETAILS ON  
THE FORECAST.  
-MILES  
 

 
   
AVIATION...FOR THE 02/12Z TAF CYCLE
 
AREAS OF MVFR CEILINGS WILL  
BURN OFF QUICKLY THIS MORNING. VFR WILL PREVAIL FOR THE REMAINDER  
OF THE TAF CYCLE.  
 
-SMITH  
 

 
   
MARINE...UPDATED 840 AM PDT THURSDAY 2 JULY 2020
 
GUSTY NORTH  
WINDS AND STEEP TO VERY STEEP SEAS WILL CONTINUE THROUGH THIS  
EVENING AS THE THERMAL TROUGH PERSISTS ALONG THE COAST. THE  
STRONGEST WINDS WITH VERY STEEP AND HAZARDOUS SEAS WILL CONTINUE  
SOUTH OF GOLD BEACH. WINDS AND SEAS WILL REMAIN HIGHEST DURING THE  
AFTERNOON AND EVENING HOURS.  
 
CONDITIONS WILL IMPROVE AS THE THERMAL TROUGH WEAKENS FRIDAY, WITH  
SMALL CRAFT ADVISORY CONDITIONS RETREATING TO AREAS SOUTH OF CAPE  
BLANCO. RELATIVELY CALM CONDITIONS ARE THEN LIKELY FRIDAY NIGHT INTO  
EARLY NEXT WEEK, ALTHOUGH A LOW, LONG PERIOD SOUTHERLY SWELL IS  
EXPECTED LATER FRIDAY THROUGH THE WEEKEND, WHICH COULD RESULT IN  
PROBLEMATIC BAR CONDITIONS AND INCREASED SNEAKER WAVE RISK. THE  
THERMAL TROUGH WILL RETURN NEXT WEEK, BUT MODELS ARE SHOWING IT  
TAKING UP A MORE INLAND POSITION. THIS WOULD KEEP NORTH WINDS IN  
PLACE OVER THE AREA, BUT AT A MUCH WEAKER STRENGTH THAN DURING A  
TYPICAL EVENT.  
 
-SVEN  
 

 
   
PREV DISCUSSION
 
/ISSUED 450 AM PDT THU JUL 2 2020/  
 
DISCUSSION...UPPER TROUGHING WILL DOMINATE OUR WEATHER PATTERN INTO  
NEXT WEEK, AND WEATHER IMPACTS WILL BE MINIMAL THROUGH THE NEXT 7  
DAYS. MARINE LAYER STRATUS HAS MADE ITS WAY INTO THE UMPQUA  
BASIN, AND THE COAST, AS IS TYPICAL WHEN THE WINDS ALOFT (AT ABOUT  
5000 FT) TURN MORE NORTHERLY, HAS AT LEAST PARTIALLY CLEARED OUT  
NORTH OF CAPE BLANCO. EXPECT ANY MORNING CLOUDS TO CLEAR OUT LATER  
THIS MORNING,  
 
A WARMING TREND IS EXPECTED TODAY (ABOUT 5 DEGREES WARMER THAN  
YESTERDAY), AND THEN TEMPERATURES SHOULD REMAIN RELATIVELY STEADY  
THROUGH THE WEEKEND. A SUNNY 4TH OF JULY WEEKEND IS EXPECTED WITH  
TEMPERATURES NEAR NORMAL AND TYPICAL AFTERNOON BREEZES. MODELS SHOW  
A ROBUST AREA OF MARINE LAYER CLOUDS OVER THE NORTHEAST PACIFIC  
WATERS, SO EXPECT NIGHTTIME AND MORNING LOW CLOUDS TO MOVE INLAND TO  
THE UMPQUA BASIN, THEN CLEAR IN THE LATE MORNING/EARLY AFTERNOON.  
FOR THE IMMEDIATE COASTLINE, CLEARING IS A LITTLE MORE UNCERTAIN,  
BUT WE DO THINK THAT AT LEAST PARTLY SUNNY SKIES CAN BE EXPECTED IN  
THE AFTERNOONS/EARLY EVENING TIMEFRAME...BEFORE THE MARINE STRATUS  
MOVES BACK IN LATE IN THE EVENING AND OVERNIGHT.  
 
MIDLEVEL WINDS (AT ABOUT 10000 FEET ABOVE SEA LEVEL) DICTATE  
MUCH OF THE WEATHER WE EXPERIENCE IN THE SUMMERTIME...AND IN THE  
WINTERTIME TO SOME EXTENT. WE'VE TRANSITIONED AWAY FROM LATE  
SPRING FRONTAL-TYPE THUNDERSTORM ACTIVITY THAT INVOLVES WARMING  
SURFACE TEMPERATURES DUE TO INCREASING SUN ANGLE AND THE LAST OF  
COLD AIR "POOLS" ALOFT BEHIND COLD FRONTS. NOW THROUGH AUGUST,  
THUNDERSTORMS ARE GENERALLY DICTATED BY HOW MUCH MOISTURE CAN BE  
DELIVERED INTO OUR FORECAST AREA. SUMMERTIME WINDS THAT ARE  
GENERALLY FROM A WESTERLY DIRECTION (NORTHWEST TO SOUTHWEST)  
USUALLY BRING RELATIVELY DRY AND STABLE AIR TO THE FORECAST AREA.  
THIS MAY SEEM STRANGE, GIVEN THAT THESE WINDS ARE COMING FROM THE  
OCEAN. HOWEVER, THE NORTHEAST PACIFIC IS A COLD OCEAN, AND THE  
COLDER THE OCEAN THE LESS EVAPORATION OF MOISTURE INTO THE  
ATMOSPHERE. SUMMERTIME THUNDERSTORMS IN OUR FORECAST AREA DEPEND  
ON SIGNIFICANT MOISTURE, SO ANY WINDS THAT COME FROM OUR LOCAL  
OCEAN WATERS TYPICALLY DO NOT PROVIDE SUFFICIENT MOISTURE. WHEN  
DEEP LAYER WINDS SHIFT MORE SOUTHERLY, THE MOISTURE SOURCE CAN  
SHIFT TO DISTANT, WARMER OCEANS LIKE THE GULF OF CALIFORNIA AND  
GULF OF MEXICO. THIS IS WHEN SIGNIFICANT THUNDERSTORM EVENTS  
ENTER THE PICTURE. ALL THIS EARLY-MORNING PONTIFICATING ABOUT  
WINDS ABOVE THE SURFACE IS TO BRING HOME THE POINT THAT THESE  
WINDS ARE SO MEANINGFUL FOR OUR FORECAST AREA, AND THAT REGIONAL  
MIDLEVEL WINDS WILL REMAIN SOUTHWESTERLY TO WESTERLY THROUGH  
WEDNESDAY AT LEAST, RESULTING IN A STABLE AIR MASS WITH NO  
THUNDERSTORMS EXPECTED.  
 
AS WE MOVE INTO LATE NEXT WEEK, THERE'S SOME DATA THAT SUGGESTS AS A  
4-CORNERS HIGH DEVELOPS IN THE DESERT SOUTHWEST, MIDLEVEL WINDS MAY  
SHIFT TO A MORE SOUTHERLY DIRECTION. HOWEVER, THE CONSENSUS OF THE  
MODEL DATA KEEPS GENERALLY SOUTHWESTERLY FLOW ALOFT, SO WE'RE  
KEEPING THUNDERSTORMS OUT OF THE FORECAST EVEN LATE INTO NEXT WEEK.  
WE'LL KEEP MONITORING THE EVOLUTION OF THIS UPPER TROUGHING  
PATTERN.  
 
FIRE WEATHER...UPDATED 200 AM PDT THURSDAY, 2 JULY 2020...GUSTY  
NORTHEAST WINDS AND MODERATE HUMIDITY RECOVERIES ARE OCCURRING  
ALONG THE MID SLOPES AND RIDGES IN FIRE ZONES, 618, 619 AND  
WESTERN 620 THIS MORNING.  
 
ASIDE FROM AFTERNOON BREEZES, IT'S LOOKING LIKE A RELATIVELY  
QUIET FIRE WEATHER PATTERN FOR AT LEAST THE NEXT 7-10 DAYS. THE  
GENERAL PATTERN WILL FEATURE TROUGHINESS OVER THE AREA WITH A  
STABLE NORTHWEST, THEN SOUTHWEST FLOW. THIS TYPICALLY RESULTS IN  
TEMPERATURES AROUND OR SLIGHTLY BELOW NORMAL AND NO PRECIPITATION.  
A WARM UP IS EXPECTED THROUGH EARLY NEXT WEEK. EVEN THEN,  
AFTERNOON TEMPERATURES ARE EXPECTED TO BE NEAR NORMAL FOR THIS  
TIME OF THE YEAR.  
 
THUNDERSTORM CHANCES ARE NEXT TO ZERO THROUGH THE FORECAST PERIOD.  
THIS IS BECAUSE OF GENERALLY STABLE AND DRY NORTHWEST TO SOUTHWEST  
FLOW ALOFT AND DRIER MID LEVEL MOISTURE. A UPPER TROUGH WILL MOVE  
INTO THE AREA BY THE START OF NEXT WEEK WITH A WEAK TRIGGER, BUT  
ONCE AGAIN MID LEVEL MOISTURE IS LACKING, THUS NO THREAT OF  
THUNDERSTORMS.  
 
BEYOND NEXT MONDAY THE OPERATIONAL MODELS, ENSEMBLE MEMBERS AND  
CLUSTER ANALYSIS ALL POINT TO A SIMILAR CONCLUSION. GENERAL  
TROUGHINESS WITH CONTINUED DRY AND STABLE CONDITIONS.  
-PETRUCELLI/KEENE  
 

 
   
MFR WATCHES/WARNINGS/ADVISORIES
 
 
OR...FROST ADVISORY UNTIL 8 AM PDT THIS MORNING FOR ORZ029>031.  
 
CA...FROST ADVISORY UNTIL 8 AM PDT THIS MORNING FOR CAZ084.  
 
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 5 AM PDT FRIDAY FOR PZZ350-370.  
SMALL CRAFT ADVISORY UNTIL 2 AM PDT SATURDAY FOR PZZ356-376.  
HAZARDOUS SEAS WARNING UNTIL 5 AM PDT FRIDAY FOR PZZ356-376.  
 

 
 
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