597  
FXUS66 KSTO 191105  
AFDSTO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SACRAMENTO CA  
405 AM PDT WED JUN 19 2019  
 
   
SYNOPSIS
 
 
A SLOW COOLING TREND EXPECTED THROUGH THE END OF THE WEEK AS A LOW  
PRESSURE SYSTEM DROPS THROUGH THE PACIFIC NORTHWEST. DAYTIME  
TEMPERATURES DOWN TO NEAR OR BELOW NORMAL THURSDAY AND FRIDAY.  
BREEZY NORTH WINDS BEHIND THE DEPARTING LOW PRESSURE SYSTEM WILL  
BRING ELEVATED FIRE WEATHER CONCERNS AT THE END OF THE WEEK.  
WARMER THAT NORMAL OVER THE WEEKEND WITH COOLING AGAIN EARLY NEXT  
WEEK.  
 

 
   
DISCUSSION
 
 
UPPER LEVEL HIGH PRESSURE RIDGE OVER THE EASTERN PACIFIC AND WEST  
COAST BRINGING FAIR SKIES TO THE CWA THIS MORNING. A FAIRLY SOLID  
DELTA BREEZE IS NOW IN PLACE SO MAY SEE SOME SCATTERED COASTAL  
CLOUDS MAKE IT INTO THE DELTA THIS MORNING. OVERALL AIRMASS WILL  
COOL A BIT TODAY AS A LOW PRESSURE SYSTEM DROPS INTO THE PACIFIC  
NORTHWEST. DAYTIME HIGHS TODAY WILL DROP A FEW TO SEVERAL DEGREES  
BUT STILL REMAIN ABOVE NORMAL FOR THIS TIME OF YEAR. STABLE  
CONDITIONS UNDER THE RIDGE SHOULD KEEP MOUNTAIN CLOUD COVER TO A  
MINIMUM THIS AFTERNOON. AIRMASS COOLS QUITE A BIT MORE ON THURSDAY  
AS THE UPPER LOW DIGS FARTHER SOUTHWARD INTO THE NORTHERN GREAT  
BASIN. DAYTIME HIGHS THURSDAY ARE FORECAST TO DROP TO AROUND  
NORMAL. BY THE END OF THE DAY THURSDAY, SURFACE HIGH PRESSURE IS  
FORECAST TO NOSE INTO OREGON BRINGING A MODERATELY TIGHT NORTHERLY  
GRADIENT AND BREEZY NORTH WINDS TO THE NORTHERN FORECAST AREA.  
MODERATELY LOW HUMIDITY WILL MEAN ELEVATED FIRE CONCERNS. BREEZY  
NORTH WINDS WILL CONTINUE THROUGH SATURDAY MORNING ESPECIALLY  
FRIDAY AND FRIDAY NIGHT AS GOOD UPPER LEVEL SUPPORT DEVELOPS.  
 
THE MAIN UPPER TROUGH IS FORECAST TO BE OVER THE GREAT BASIN ON  
FRIDAY BUT MODELS HINT AT A FINAL SHORTWAVE DIGGING SOUTHWARD  
SOMEWHERE DOWN THE WESTERN GREAT BASIN IN THE AFTERNOON. GFS  
CARVES THIS SHORTWAVE FARTHEST WESTWARD AND PAINTS SOME SHOWERS  
OVER THE NORTHERN SIERRA FRIDAY AFTERNOON. OTHER MODELS ARE WEAKER  
WITH THIS FEATURE. HAVE LEFT SHOWERS OUT OF SIERRA FORECAST FOR  
NOW BUT HAVE INCLUDED GHOST POPS SHOULD LATER MODELS BECOME MORE  
COORDINATED WITH A DEEPER SHORTWAVE. OVERALL AIRMASS COOLS ENOUGH  
BY FRIDAY AFTERNOON THAT DAYTIME HIGHS ARE CURRENTLY FORECAST TO  
COME IN A LITTLE BELOW NORMAL. HIGH PRESSURE PUSHES BACK IN ON  
SATURDAY WARMING TEMPERATURES BACK UP ABOVE NORMAL AND BRINGING LIGHTER  
SURFACE GRADIENTS FOR LIGHTER NORTH WINDS.  
 

 
 
.EXTENDED DISCUSSION (SUNDAY THROUGH WEDNESDAY)  
 
UPPER RIDGING OVER NORCAL SUNDAY BREAKS DOWN, THEN LARGE UPPER  
LOW FROM GOA DIGS SLOWLY SOUTHEAST MONDAY INTO WEDNESDAY. THIS  
WILL RESULT IN INCREASING SYNOPTIC COOLING AND DELTA BREEZE AS  
HEIGHTS/THICKNESSES LOWER. HIGH TEMPERATURES GO FROM ABOUT 5  
DEGREES ABOVE NORMAL SUNDAY TO ABOUT 5 DEGREES BELOW NORMAL BY  
WEDNESDAY. NOT EXPECTING PRECIP WITH DEEPENING TROUGHING NEXT WEEK  
BUT SHOULD SEE A DEEPENING MARINE LAYER AND INCREASING ONSHORE  
FLOW.  
 

 
   
AVIATION
 
 
VFR CONDS OVR INTR NORCAL NXT 24 HRS EXC LCL MVFR/IFR CONDS POSS  
IN ST VCNTY DELTA BTWN 10Z-18Z. SWLY SFC WND GSTS TO 30 KTS VCNTY  
DELTA THIS MRNG AND AGN THIS AFTN INTO EVE. LCL NLY SFC WND GSTS  
TO 25 KTS POSS IN NRN SAC VLY TDA TIL 00Z.  
 

 
   
STO WATCHES/WARNINGS/ADVISORIES
 
 
FIRE WEATHER WATCH FROM THURSDAY AFTERNOON THROUGH SATURDAY  
MORNING FOR CENTRAL SACRAMENTO VALLEY IN GLENN, COLUSA, YUBA,  
NORTHERN SUTTER, AND BUTTE COUNTY BELOW 1000 FT-EASTERN  
MENDOCINO NF-EASTERN PORTION OF SHASTA/TRINITY NF-NORTHERN  
SACRAMENTO VALLEY TO SOUTHERN TEHAMA COUNTY LINE BELOW 1000 FT-  
NORTHERN SIERRA FOOTHILLS FROM 1000 TO 3000 FT. INCLUDES  
PORTIONS OF SHASTA-TRINITY AND BUTTE UNITS-SOUTHEAST EDGE SHASTA-  
TRINITY NF AND WESTERN PORTIONS OF TEHAMA-GLENN UNIT-SOUTHERN  
SACRAMENTO VALLEY IN YOLO-SACRAMENTO FAR WESTERN PLACER,  
SOUTHERN SUTTER AND SOLANO COUNTY BELOW 1000 FT.  
 

 
 

 
 
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