715
FXUS66 KEKA 210758
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
1258 AM PDT TUE APR 21 2026
SYNOPSIS
A CUTOFF LOW WILL CONTINUE TO AFFECT THE REGION THROUGH
WEDNESDAY WITH RAIN SHOWERS AND LIGHT MOUNTAIN SNOW. THERE IS ALSO A
CHANCE FOR THUNDERSTORMS, MAINLY THIS AFTERNOON. A STRETCH OF DRIER
WEATHER IS THEN EXPECTED TO BEGIN LATE IN THE WEEK.
DISCUSSION
A FRONTAL BOUNDARY ASSOCIATED WITH THE APPROACHING
UPPER LEVEL LOW CONTINUES TO PUSH RAIN THROUGH THE REGION EARLY
THIS MORNING. SNOW LEVELS ARE MOSTLY AROUND 5000 FT ASIDE FROM
NORTHEASTERN TRINITY WITH LOCALLY LOWER SNOW LEVELS AROUND 4500
FEET. THE BULK OF THE STRATIFORM RAIN WILL MOVE OFF TO THE EAST
WITH THE BACK END OF THE PRECIPITATION ONGOING IN LAKE AND NE
TRINITY INTO EARLY/MID THIS MORNING. GENERALLY SHOWERS ARE
EXPECTED TO CONTINUE FOR MOST OF THE REGION TODAY AS THE CENTER OF
THE UPPER LEVEL LOW SLOWLY APPROACHES THE AREA AND MOVES
OVERHEAD.
THIS AFTERNOON AS THE UPPER LOW MOVES OVERHEAD, THE
POTENTIAL FOR THUNDERSTORMS INCREASES. THE HREF IS SHOWING 200 TO
400 J/KG OF SURFACE CAPE AND LAPSE RATES ALOFT OF AROUND 7C/KM.
THIS SHOULD BE BE ENOUGH TO DEVELOP SOME THUNDERSTORMS. A FEW OF
THEM COULD BE STRONG WITH AROUND 30 TO 35 KT OF DEEP SHEAR. THEY
WILL BE THE MOST LIKELY IN MENDOCINO AND LAKE COUNTIES IN THE
AFTERNOON. THIS IS ALSO EXPECTED TO LOWER SNOW LEVELS TO AROUND
4000 FEET TUESDAY MORNING. SNOW LEVELS ARE EXPECTED TO RISE IN THE
AFTERNOON. A WINTER WEATHER ADVISORY CONTINUES FOR THE FAR
NORTHEASTERN PORTION OF TRINITY COUNTY INTO LATE THIS MORNING.
SHOWERS ARE EXPECTED TO LINGER INTO WEDNESDAY AS A SHORTWAVE MOVES
DOWN THE BACK SIDE OF THE LOW.
THURSDAY AND FRIDAY, HIGH PRESSURE IS EXPECTED TO BUILD INTO THE
AREA BRINGING DRY WEATHER TO THE AREA. FOR THE WEEKEND, MAINLY DRY
WEATHER IS ANTICIPATED, BUT THERE IS AN UPPER LEVEL LOW TO THE
NORTHEAST OF THE AREA. THE ENSEMBLE CLUSTERS ARE SHOWING DIFFERENT
POSITIONS OF THIS LOW. IF THE SOLUTION WITH THE LOW CLOSER TO THE
AREA VERIFIES, THIS MAY ALLOW A FEW CONVECTIVE SHOWERS OVER THE
MOUNTAINS EACH AFTERNOON. MKK
AVIATION
COLD LOW ALOFT SPINNING OFFSHORE WILL CONTINUE TO EDGE
EAST-SOUTHEAST TOWARD THE NORTHERN CALIFORNIA COAST TONIGHT THROUGH
TUESDAY. OCCASIONAL RAIN WITH MVFR CEILINGS AND VISIBILITIES ARE
EXPECTED THROUGH TUESDAY. VERY BRIEF IFR CONDITIONS WILL ALSO REMAIN
POSSIBLE (A 20% CHANCE) AS WELL IN PERIODS OF MODERATE RAIN.
INSTABILITY WILL INCREASE ON TUE. ISOLATED STRONG CELLS AND TSTMS
ARE POSSIBLE - MAINLY OVER THE INTERIOR IN THE AFTERNOON. LONG AND
THIN CAPE PROFILES WITH LOW EQUILIBRIUM LEVELS SEEM FAVORABLE FOR
BRIEF HEAVY RAIN, SMALL HAIL AND GUSTY WINDS.
MARINE
SEAS WERE STILL RUNNING AROUND 10 FT AT 12 TO 13 SECONDS
SOUTH OF CAPE MENDO MONDAY EVENING. THIS IS A COUPLE FEET ABOVE WAVE
MODEL GUIDANCE, NAMELY NWPS AND GFS-WAVES. TREND IS MOST LIKELY
CORRECT AND SEAS SHOULD TREND DOWN THROUGH THE NIGHT. OTHERWISE,
SOUTH TO SOUTHEAST WINDS WILL CONTINUE INTO TUE AS A WEAK SURFACE
LOW MEANDERS ABOUT JUST OUTSIDE THE NORTHERN OUTER WATERS. A FEW
GUSTS AROUND 20 KT ARE POSSIBLE (20-30% CHANCE) NEARSHORE IN THE
AFTERNOON ON TUE. OTHERWISE, WIND SPEEDS ARE FORECAST TO REMAIN
BELOW ADVISORY LEVEL TUE. SURFACE PRESSURE GRADIENTS REMAIN FLAT AND
INSUFFICIENT TO WARRANT HEADLINES THROUGH WED AS THE WEAK LOW LIFTS
OUT TO THE NE. GREATER INSTABILITY ASSOCIATED WITH COLDER AIR ALOFT
MAY RESULT IN STRONG CELLS OR ISOLATED TSTMS CAPABLE OF GUSTY WINDS
ON TUE. FINALLY HIGH PRESSURE BUILDS OFFSHORE ON THU AS THE
CONVOLUTED LOW COMPLEX EXISTS TO THE SOUTHEAST. NORTHERLY WINDS AND
STEEP WAVES ARE FORECAST TO BUILD THURSDAY THROUGH FRIDAY AND
ADVISORIES WILL LIKELY BE NECESSARY FOR SMALL VESSELS.
EKA WATCHES/WARNINGS/ADVISORIES
CA...
WINTER WEATHER ADVISORY UNTIL 11 AM PDT THIS MORNING FOR
CAZ117.
NORTHWEST CALIFORNIA COASTAL WATERS...
NONE.
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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