811  
FXUS66 KEKA 192337  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
337 PM PST FRI JAN 19 2018  
   
SYNOPSIS
 
SHOWERS WILL SLOWLY DIMINISH ACROSS THE REGION TONIGHT.  
A BRIEF PERIOD OF DRIER WEATHER IS EXPECTED TO OCCUR DURING  
SATURDAY, FOLLOWED BY ANOTHER ROUND OF RAIN ON SUNDAY. SNOW ON THE  
HIGHWAYS PASSES IS POSSIBLE ON SUNDAY IN TRINITY COUNTY.  
 

 
   
DISCUSSION
 
SHOWERS CONTINUE THIS AFTERNOON ACROSS THE AREA AS  
THE UPPER LEVEL TROUGH MOVES INLAND. THE HEAVIEST SHOWERS WILL BE  
CLOSER TO THE COAST. SNOW LEVELS CONTINUE TO BE AROUND 2,500 TO  
3,000 FEET WITH MOST ACCUMULATING SNOW ABOUT 3,000 FEET. TONIGHT  
SHOWERS WILL CONTINUE TO DIMINISH, ALTHOUGH A FEW MAY LINGER IN  
DEL NORTE COUNTY INTO SATURDAY MORNING. SATURDAY AFTERNOON MAINLY  
DRY CONDITIONS ARE EXPECTED, ALTHOUGH CONTINUED ONSHORE FLOW WILL  
BRING PARTLY TO MOST CLOUDY SKIES.  
 
SUNDAY MORNING A SHORTWAVE MOVING THROUGH THE ZONAL FLOW IS  
EXPECTED TO BRING AND RAIN AND SNOW TO THE AREA. AT THE COAST THIS  
WILL START SHORTLY BEFORE SUNRISE AND MOVE INLAND THROUGH THE  
MORNING HOURS. THE NAM IS STILL SLIGHTLY FASTER ON THIS TIMING,  
BUT THE GFS AND ECMWF ARE IN FAIRLY GOOD AGREEMENT ON THE TIMING  
SO WENT WITH THEM. THE HEAVIEST RAIN WITH THIS SYSTEM LOOKS TO BE  
ON THE KING RANGE IN SOUTHERN HUMBOLDT COUNTY AND NORTHERN  
MENDOCINO COUNTY. LOCAL AMOUNTS OVER 3 INCHES ARE POSSIBLE IN 12  
HOURS. THE ECMWF HAS THE HEAVIER RAIN FARTHER NORTH. IF THE GFS  
CONTINUES TO SHOW THE THE HEAVY RAINFALL AMOUNTS A FLOOD WATCH  
MAY BE NEEDED OVER PORTIONS OF MENDOCINO COUNTY. FARTHER INLAND  
THERE MAY BE COLD AIR LINGERING IN THE EASTERN TRINITY VALLEYS.  
THIS COMBINED WITH MODERATE SOUTH TO SOUTHEAST WINDS CREATING  
UPSLOPE FLOW BRINGS THE POTENTIAL FOR HEAVY SNOW. THERE IS THE  
POTENTIAL FOR SNOW AMOUNTS OF OF 5 TO 10 INCHES OF SNOW AS LOW AS  
2,500 FEET, BUT CONFIDENCE IS LOW ON THIS. ELSEWHERE SNOW LEVELS  
MAY INITIALLY BE DOWN TO 2,500 FEET, BUT ARE EXPECTED TO RISE  
QUICKLY AS THE PRECIP MOVES IN. STILL, A WINTER STORM WATCH HAS  
BEEN ISSUED FOR TRINITY COUNTY ABOVE 3,000 FEET. THIS MAY NEED TO  
BE LOWERED AS TO 2,500 FEET IF MODELS REMAIN CONSISTENT.  
ADDITIONAL AREAS MAY NEED HEADLINES, BUT THIS AREA IS EXPECTED TO  
SEE THE BIGGEST IMPACTS. THIS SYSTEM IS ALSO EXPECTED TO BRING  
GUSTY WINDS TO THE COASTAL AREAS. THE NAM SHOWS A FAIRLY STRONG  
SOUTHERLY JET OF 60 TO 65 KT AT 925 MB JUST OFF THE COAST. IN  
HUMBOLDT AND DEL NORTE COUNTY GUSTS OF 55 MPH ARE POSSIBLE ON THE  
RIDGES WITH GUSTS OF 40 TO 45 MPH ALONG THE EXPOSED HEADLANDS. A  
WIND ADVISORY MAY BE NEEDED.  
 
SUNDAY NIGHT PRECIP WILL COME TO AN END QUICKLY LEAVING MONDAY  
FAIRLY DRY, ALTHOUGH THE FLOW REMAINS ZONAL AND IT WILL LIKELY  
REMAIN CLOUDY WITH A SHOWER OR TWO POSSIBLE. MONDAY NIGHT INTO  
TUESDAY THE NEXT SHORTWAVE MOVING THROUGH THE ZONAL FLOW IS  
EXPECTED TO BRING RAIN TO THE AREA. TUESDAY NIGHT INTO WEDNESDAY  
THIS ATMOSPHERIC RIVER REPOSITIONS AND TAKES AIM AT THE AREA AGAIN  
BRINGING HEAVY ADDITIONAL HEAVY. THIS IS ABOUT 36 HOURS OF  
POTENTIALLY HEAVY RAIN AND COULD CAUSE HYDROLOGIC CONCERNS. BEHIND  
THIS SYSTEM SHOWERS AND COLDER AIR ARE EXPECTED ON THURSDAY WITH  
MAINLY DRY WEATHER POSSIBLE ON FRIDAY.  
 

 
   
AVIATION...A WAVE OF SHOWERS
 
ASSOCIATED WITH AN UPPER LEVEL  
TROUGH...CONTINUED TO ROTATE INTO THE REGION. SHOWERS,  
OCCASIONALLY HEAVY CONTINUED TO ALSO IMPACT "MAINLY" THE ACV AND  
CEC AIR TERMINALS. CONDITIONS BECAME MOSTLY VFR BY AFTERNOON.  
HOWEVER, THE SCATTERED FLOW OF SHOWERS HAS PRESENTED THE AREA WITH  
A MIXED BAG OF VFR-MVFR AS SHOWERS MOVE OVER AIRFIELDS/AIRPORTS.  
THROUGH THE 24 HOUR TAF PERIOD, BRIEF HIGH RIDGING WILL SHIFT  
ACROSS THE REGION BRINGING DRIER CONDITIONS, ALTHOUGH A FEW  
RESIDUAL SHOWERS MAY LINGER. MVFR CAN BE EXPECTED FOR A SHORT  
PERIOD IN THE MORNING AT ACV AND CEC. ACROSS THE INTERIOR, SHOWERS  
MAY ALSO LINGER THROUGH AFTERNOON/EARLY EVENING, BUT A CONCERN  
FOR UKI'S AIRPORT WILL BE THE POSSIBILITY OF IFR FLIGHT CONCERNS  
DUE TO PATCHY FOG AND LOWER CEILING.  
 

 
   
MARINE
 
WESTERLY SWELL WILL CONTINUE TO DOMINATE THROUGH  
SAT, BUT SIGNIFICANT WAVE HEIGHTS WILL SLOWLY SUBSIDE. WAVE HEIGHTS  
WILL EVENTUALLY BOTTOM OUT AROUND 10 FT LATE SAT NIGHT BEFORE WEST  
SWELL FROM A NEW STORM ALONG WITH ROBUST SOUTHERLIES IN ADVANCE OF A  
FRONT COMBINE FORCES TO GENERATE SEAS AROUND 15 TO 20 FEET SUN INTO  
SUN NIGHT. THIS WILL LIKELY RESULT IN A CHAOTIC AND HAZARDOUS SEA  
STATE THAT WILL LAST THROUGH AT LEAST EARLY MON MORNING. DECREASING  
WINDS WILL ALLOW SEAS TO SETTLE THROUGH EARLY TUE, BUT AN ACTIVE  
PATTERN WILL CONTINUE WITH ANOTHER FRONT EXPECTED FOR TUE.  
 

 
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...WINTER STORM WATCH FROM SUNDAY MORNING THROUGH SUNDAY EVENING  
FOR CAZ107-108.  
 
WINTER WEATHER ADVISORY UNTIL 7 PM PST THIS EVENING FOR CAZ102-  
105-106.  
 
NORTHWEST CALIFORNIA COASTAL WATERS...  
GALE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY  
AFTERNOON FOR PZZ450-455-470-475.  
 
SMALL CRAFT ADVISORY UNTIL 3 AM PST SUNDAY FOR PZZ450-455-470-  
475.  
 

 
 

 
 
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