760  
FXUS66 KEKA 032128  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
228 PM PDT THU JUL 3 2025  
   
SYNOPSIS
 
COOLER INTERIOR TEMPERATURES AND A DEEPER MARINE LAYER  
ARE EXPECTED THROUGH FRIDAY. TEMPERATURES WILL GENERALLY TREND  
WARMER THIS WEEKEND AND INTO EARLY NEXT WEEK. THERE IS A SLIGHT  
CHANCE OF THUNDERSTORMS OVER NE TRINITY COUNTY THIS EVENING.  
 

 
   
DISCUSSION
 
 
SATELLITE IMAGERY AND WEB CAMERAS SHOWED VARIABLE HIGH LEVEL  
CLOUDS MOVING ACROSS THE AREA TODAY. ALONG THE COAST STRATUS HAS  
BEEN LESS EXTENSIVE AND APPEARED MORE DISRUPTED ALONG THE NORTH  
COAST. IN CONTRAST, SOUTH OF CAPE MENDOCINO, STRATUS WAS  
ACTUALLY EXPANDING ALONG THE MENDOCINO COAST. STRATUS SHOULD  
REBUILD AND PUSH DEEPER INTO THE RIVER VALLEYS TONIGHT AS A SHORT  
WAVE TROUGH PROGRESSES ACROSS THE AREA. A STRONGER AND HIGHER  
MARINE INVERSION WILL LIKELY KEEP COOL AND HUMID MARINE AIR  
TRAPPED AGAINST THE COASTAL TERRAIN THROUGH FRIDAY, ESPECIALLY  
AROUND HUMBOLDT BAY AND EEL DELTA. INTERIOR TEMPERATURES COOLED  
CONSIDERABLY TODAY IN RESPONSE TO STRONGER ONSHORE WINDS. TEMPS  
ARE FORECAST TO REMAIN BELOW SEASONAL AVERAGES ON FRIDAY; IN THE  
80'S TO LOWER 90'S THAT IS.  
 
WATERS VAPOR IMAGERY SHOWED A CYCLONIC CIRCULATION CENTER JUST  
OFFSHORE AT THE BASE OF A 500MB TROUGH STEADILY MOVING EASTWARD  
TOWARD THE NORTH COAST THIS AFTERNOON. MODEL BASED SOUNDINGS  
CONTINUE TO DEPICT STEEP MID LEVEL LAPSE RATES WITH SUFFICIENT  
CAPE AND INSTABILITY FOR STORMS ACROSS NE TRINTY COUNTY THIS  
EVENING. SOME OF THE CONVECTIVE ALLOWING MODELS EVEN HINT AT  
STORMS FIRING UP WITH 500MB VORT PASSAGE AROUND OR SHORTLY AFTER  
MIDNIGHT. HREF THUNDER PROBABILITIES ARE JUST NORTH OF THE AREA IN  
SISKIYOU COUNTY, HOWEVER. WE CANNOT COMPLETELY RULE OUT A STRAY  
LIGHTNING STRIKE, ESPECIALLY WITH SHALLOW MOIST CONVECTION  
DEVELOPING OVER NE TRINITY THIS AFTERNOON WITH DAYTIME HEATING.  
CONFIDENCE IS BY NO MEANS HIGH THERE WILL BE ANY STRIKES WITH ONLY  
A FEW HREF COMPOSITE CORES OVER 40DBZ SKIRTING ALONG THE BORDER  
WITH SISKIYOU AND SHASTA COUNTIES.  
 
ANOTHER SHORT WAVE TROUGH WILL APPROACH OVER THE WEEKEND AND EVENTUALLY  
DEVELOP INTO A SEMI-CLOSED 500MB CIRCULATION OR CUT-OFF LOW EITHER  
OFFSHORE TO OUR SW OR CLOSER TO THE NORTHERN CALIFORNIA COAST BY  
LATE SUNDAY INTO MONDAY. DETERMINISTIC MODEL GUIDANCE HAS ROBUST  
SE OR E FLOW AT 500MB (40-50KT OF BULK SHEAR) BY SUNDAY NIGHT INTO  
MONDAY. THIS PATTERN (CLOSE LOW OFFSHORE) AND 500MB SE WIND DIRECTION  
IS CONDUCIVE FOR THUNDERSTORMS IN OUR FORECAST AREA THIS TIME OF  
YEAR. MOISTURE APPEARS QUITE SPARSE. CONVECTIVE PARAMETERS AND  
MODEL DERIVED SOUNDINGS ARE NOT VERY SUPPORTIVE FOR ANY STORMS.  
MID LEVEL LAPSE RATES ARE FORECAST TO BECOME STEEP, HOWEVER. WITH  
BELOW NORMAL PWATS ACROSS OUR MORE CONVECTIVELY ACTIVE AREAS IN  
THE INTERIOR, SEE NO COMPELLING REASON TO DEVIATE FROM THE NBM  
GUIDANCE AND ADD THUNDERSTORMS TO THE FORECAST AT THIS TIME. THIS  
WILL NEED TO BE WATCHED. ONCE WITHIN RANGE OF THE CAMS, WE SHOULD  
HAVE A BETTER HANDLE ON THIS POTENTIALLY HIGH IMPACT BUT LOW  
PROBABILITY EVENT.  
 
INTERIOR TEMPERATURES ARE FORECAST TO WARM UP NEXT WEEK AS THE  
TROUGH EJECTS N-NE IN RESPONSE TO AN UPSTREAM KICKER. BY MID TO LATE  
NEXT WEEK THE FOUR CORNERS RIDGE WILL EXPAND WESTWARD AND  
NORTHWESTWARD. THERE IS STILL UNCERTAINTY WITH THE RATE AND  
MAGNITUDE OF THE WARMING WITH UPSTREAM TROUGHS POSSIBLY KEEPING THE  
HOTTEST AIR TO OUR SOUTH. MULTIPLE ENSEMBLE SYSTEMS CONTINUE TO  
CONSISTENTLY SHOW HIGH PROBABILITIES (>80% CHANCE) FOR 500MB  
HEIGHTS 588DM OR MORE WITH LOWER PROBABILITIES (30-50% CHANCE)  
FOR 594DM OR MORE. 100+ DEGREE HEAT FOR OUR TYPICAL HOT VALLEYS IN  
THE INTERIOR IS HIGHLY PROBABLE. THERE IS GREATER UNCERTAINTY FOR  
COASTAL VALLEYS OF WESTERN HUMBOLDT (EEL RIVER VALLEY) AND  
MENDOCINO (ANDERSON VALLEY). LATE NEXT WEEK WILL LIKELY BE THE  
HOTTEST DAYS SO FAR THIS SUMMER.  
 

 
   
AVIATION
 
 
A DEEP MARINE LAYER CONTINUES TO COMPRESS INTO THE NORTH COAST  
THIS AFTERNOON WITH IFR CEILINGS AT THE COASTAL TERMINALS. GREATEST  
CHANCE FOR BRIEF MVFR SCATTERING IN CEC LATE THIS AFTERNOON AS  
NORTHERLY WINDS INCREASE OFFSHORE AND SCOUR OUT THE CLOUD COVER.  
GUSTS EXCEEDING 10 TO 15 KNOTS POSSIBLE AT BOTH COASTAL TERMINALS  
PRIOR TO 00Z. UKI ALREADY EXPERIENCING 15 TO 20 KNOT GUSTS, WITH  
GUSTS UP TO 30 KNOTS POSSIBLE LATE IN THE AFTERNOON. HREF SHOWS  
>80% PROBABILITY FOR <1K FT CEILINGS REDEVELOPING AT CEC AND ACV  
AFTER 03Z. A WEAK SHORTWAVE WILL PROVIDE ADDITIONAL INSTABILITY  
OVERNIGHT AND POTENTIAL FOR COASTAL DRIZZLE AND LIFR VIZ/CEILINGS  
AFTER 09Z FRIDAY MORNING.  
 

 
   
MARINE
 
 
NORTHERLY WINDS WILL CONTINUE IN THE OUTER WATERS WITH GALE FORCE  
GUSTS SOUTH OF CAPE MENDOCINO BEGINNING TO WIND DOWN LATE THIS  
EVENING. WINDS AND STEEP WAVES WILL DECREASE FIRST IN THE NORTHERN  
WATERS, EXTENDING INTO THE SOUTHERN WATERS THROUGH FRIDAY.  
MODERATE TO FRESH BREEZES WILL CONTINUE IN THE OUTER WATERS  
THROUGH FRIDAY AS A LONG PERIOD SOUTHWESTERLY SWELL FILLS INTO THE  
WATERS, WITH LOCALLY STRONGER GUSTS NEARSHORE AND DOWNWIND OF THE  
CAPE. NORTHERLIES EXPECTED TO STRENGTHEN AGAIN LATE SATURDAY INTO  
EARLY NEXT WEEK AS HIGH PRESSURE BUILDS BACK INTO THE REGION. NBM  
AND GLOBAL ENSEMBLES INCREASING CONFIDENCE (50 TO 70% CHANCE) IN  
POTENTIAL FOR GALE GUSTS IN THE OUTER WATERS SUNDAY THROUGH  
MONDAY, ESPECIALLY IN THE NORTHERN WATERS.  
 

 
   
FIRE WEATHER
 
 
ISOLATED LIGHTNING STRIKES WILL BE POSSIBLE (15% CHANCE) OVER NE  
TRINITY (ZONE 283) THIS EVENING AS A DRY TROUGH PROGRESSES ACROSS  
THE AREA. LIGHTNING CHANCES DECREASE TO 10% OR LESS AFTER  
MIDNIGHT. GREATEST LIGHTNING ACTIVITY IS EXPECTED IN NE CALIFORNIA  
AND SOUTHERN OREGON. OTHERWISE, GUSTY DIURNALLY DRIVEN WINDS ARE  
FORECAST TO CONTINUE THROUGH FRIDAY. THE LOWEST RH'S ARE ONCE  
AGAIN FORECAST FOR LOWER ELEVATIONS OF EASTERN TRINITY AND  
SOUTHERN LAKE COUNTY, AROUND 20-25%. GUSTS UP 25 MPH ARE EXPECTED  
FOR THE WEAVERVILLE BASIN AND SOUTHERN LAKE COUNTY. ANY NEW FIRE  
STARTS OR HOLD OVER FIRES FROM LIGHTNING STARTS COULD SPREAD  
RAPIDLY BEFORE WINDS DIES DOWN OVERNIGHT.  
 
HIGH TEMPERATURES ARE FORECAST TO WARM OVER THE WEEKEND INTO  
EARLY NEXT WEEK WHILE MINIMUM RH'S BECOME DRIER. OVERNIGHT  
RECOVERIES ARE GENERALLY EXPECTED TO REMAIN GOOD EXCEPT FOR A FEW  
EXPOSED RIDGES WHERE LOW RH'S MAY PERSIST THROUGH THE NIGHT.  
ANOTHER TROUGH WILL APPROACH OVER THE WEEKEND AND POSES A LOW RISK  
FOR CONVECTION. STRONG SOUTHEAST FLOW ALOFT SHOULD DEVELOP SUNDAY  
INTO MONDAY, HOWEVER THE AIR WILL BE DRY AT MID LEVELS. STEEP MID  
LEVEL LAPSE RATES DO INCREASE ON SUNDAY AND MONDAY, HOWEVER DEEP  
COLUMN WATER VAPOR CONTENT IS FORECAST TO REMAIN BELOW NORMAL. THE  
CUT-OFF LOW IS FORECAST TO FINALLY EJECT N-NE BY MID NEXT WEEK AS  
A MASSIVE RIDGE OVER THE FOUR CORNERS REGION EXPANDS OVER THE  
AREA. MUCH HOTTER TEMPERATURES AND DRIER HUMIDITY ARE HIGHLY  
PROBABLE (80% CHANCE) IN THE INTERIOR MID TO LATE NEXT WEEK.  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...  
NONE.  
NORTHWEST CALIFORNIA COASTAL WATERS...  
SMALL CRAFT ADVISORY UNTIL 3 AM PDT FRIDAY FOR PZZ455.  
 
SMALL CRAFT ADVISORY UNTIL 3 PM PDT THIS AFTERNOON FOR  
PZZ470.  
 
GALE WARNING UNTIL 9 PM PDT THIS EVENING FOR PZZ475.  
 

 
 

 
 
NOTE: THE FULL FORECAST DISCUSSION IS NOW REGULARLY ISSUED BETWEEN  
10 AM/PM AND 1 PM/AM. ADDITIONAL UPDATES WILL BE ISSUED AS NEEDED.  
 
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FOR FORECAST ZONE INFORMATION  
SEE THE FORECAST ZONE MAP ONLINE:  
HTTPS://WWW.WEATHER.GOV/IMAGES/EKA/ZONEMAP.PNG  
 
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