AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
452 AM PDT SAT JUL 21 2018

.SYNOPSIS...A SLIGHT COOLING TREND IS EXPECTED THIS WEEKEND
ACROSS THE INTERIOR, FOLLOWED BY A WARMING TREND THAT WILL BEGIN
MONDAY. OTHERWISE, ISOLATED THUNDERSTORMS WILL BE POSSIBLE THROUGH
SUNDAY.

&&

.DISCUSSION...A MIDLEVEL DEFORMATION ZONE WAS ORIENTED SW-NE
ACROSS NRN CA EARLY SATURDAY MORNING. PW VALUES FROM 1.0 TO 1.8
INCHES WERE LOCATED SOUTH OF THE DEFORMATION ZONE (REFERENCE THE
21/00Z RAOB FROM KOAK), AND MODEL GUIDANCE SHOWS THIS MOISTURE
GRADUALLY SPREADING NORTH ACROSS MENDOCINO COUNTY THROUGH SATURDAY
AFTERNOON, AND THEN THE REMAINDER OF NWRN CA BY SUNDAY AFTERNOON.
THE INCREASE IN MOISTURE, COMBINED WITH A STEEP LAPSE RATE
ENVIRONMENT WILL SUPPORT MODEST THUNDERSTORM CHANCES THIS WEEKEND,
PARTICULARLY DURING SUNDAY AFTERNOON OVER THE MOUNTAINS OF TRINITY
AND NORTHEAST MENDOCINO COUNTIES.

OTHERWISE, INTENSE BOUNDARY LAYER HEATING OVER THE GREAT BASIN
WILL EXPAND WESTWARD DURING NEXT WEEK. THIS WILL PROMOTE INTERIOR
VALLEY TEMPERATURES IN THE MID/UPPER 90S TO LOW 100S DURING THE
AFTERNOON, AND OVERNIGHT LOWS POTENTIALLY IN THE 60S. THUS, HEAT
RISK CONCERNS WILL BECOME ELEVATED ONCE AGAIN.

BESIDES THE HEAT...PERIODS OF LOW TO MIDLEVEL NORTHERLIES WILL
CAUSE OREGON AND SISKIYOU COUNTY WILDFIRE SMOKE TO SPREAD
SOUTHWARD ACROSS NWRN CA THIS WEEKEND INTO NEXT WEEK. THIS SMOKE
MAY IMPACT AIR QUALITY.

&&

.AVIATION...LOW CLOUDS ARE PRESENTLY STILL PINNED NEAR AND S OF
CAPE MENDOCINO COURTESY OF CONTINUED NORTHERLY WINDS OVER THE
COASTAL WATERS. HOWEVER, WINDS WILL CONTINUE TO DECREASE THROUGH
THE DAY, EVENTUALLY ALLOWING CLOUDS TO ROUND THE CAPE AND MOVE
NORTHWARD ALONG THE COAST. EVEN THE HIGH RESOLUTION MODELS AREN`T
INDICATING MUCH IN THE WAY OF LOW CLOUDS IMPACTING THE REDWOOD
COAST TERMINALS TODAY, BUT CONFIDENCE IS LOW. SMOKE FROM FIRES N
OF THE AREA IS CURRENTLY PRODUCING A BROKEN TO OVERCAST LAYER AT
AROUND 4500 FT AT BOTH KCEC AND KACV. HRRR SMOKE GUIDANCE
INDICATES THE BULK OF THIS SMOKE MAY SHIFT MORE OFFSHORE LATER IN
THE DAY AS N GRADIENT FLOW DECREASES AND LOW-LEVEL FLOW BECOMES A
BIT MORE OFFSHORE IN THAT AREA. LOW CLOUDS APPEAR TO BE THICKENING
S OF THE MENDOCINO/SONOMA COUNTY LINE, BUT HIGH RESOLUTION MODELS
DON`T APPEAR TO GENERATE ENOUGH S FLOW TO GET THE CLOUDS INTO
KUKI. WILL CONTINUE TO INDICATE A SCATTERED DECK AT AROUND 500 FT
LATER THIS MORNING. AN ISOLATED SHOWER OR THUNDERSTORM IS POSSIBLE
OVER THE YOLLA BOLLYS LATER THIS AFTERNOON OR EVENING, BUT STORM
MOTION SHOULD KEEP ANYTHING THAT DEVELOPS AWAY FROM KUKI. WINDS
WILL BE GENERALLY LIGHT ACROSS THE AREA. /SEC

&&

.MARINE...THE SURFACE THERMAL TROUGH WILL CONTINUE TO PIVOT
ACROSS THE S WATERS. AS A RESULT, WINDS WILL CONTINUE TO DECREASE
ACROSS THE AREA, ALTHOUGH WIND SPEEDS WILL REMAIN ELEVATED IN THE
N OUTER WATERS INTO SUNDAY WITH GALE FORCE GUSTS INTO THIS
AFTERNOON. WINDS WILL OCCASIONALLY BECOME SOUTHERLY OVER THE INNER
WATERS AS THE SURFACE FLOW REVERSES. EXTENDED THE EXISTING
HAZARDOUS SEAS WARNING FOR THE N INNER WATERS THROUGH 6 AM TO
ACCOUNT FOR SOME HIGHER SEAS, BUT THE WAVE HEIGHTS ARE TRENDING
DOWN IN THAT AREA. WINDS WILL BECOME LIGHT ACROSS ALL OF OUR
WATERS BY LATE SUNDAY AND INTO EARLY NEXT WEEK, WITH NORTHERLIES
INCREASING AGAIN BY THE MIDDLE OF NEXT WEEK. /SEC

&&

.FIRE WEATHER...EAST-NORTHEAST WINDS GUSTING TO 30 MPH ARE
OCCURRING ACROSS THE HIGH TERRAIN OF DEL NORTE COUNTY EARLY
SATURDAY MORNING. RH VALUES AT RIDGETOP LEVEL HAVE GENERALLY
RECOVERED INTO THE 40S, WHICH IS MITIGATING THE DEVELOPMENT OF
A MORE SIGNIFICANT FIRE WEATHER THREAT. HOWEVER, SOME OVERLAP IN
GUSTY WINDS AND FALLING RH VALUES MAY OCCUR DURING THE REMAINDER
OF SATURDAY MORNING, AND AGAIN SATURDAY EVENING, WHICH COULD
BRIEFLY YIELD LOCALLY CRITICAL CONDITIONS.

OTHERWISE, TEMPERATURES ARE EXPECTED TO COOL SLIGHTLY THIS WEEKEND
(COMPARED TO THE LAST COUPLE OF DAYS), BUT WILL STILL REMAIN NEAR
TO SLIGHTLY ABOVE NORMAL. TEMPERATURES WILL THEN RISE TO ABOVE
NORMAL VALUES MONDAY THROUGH MUCH OF NEXT WEEK, RESULTING IN AN
EXTENDED PERIOD OF HOT AND DRY CONDITIONS.

ISOLATED THUNDERSTORMS WILL BE POSSIBLE THROUGHOUT MENDOCINO
COUNTY SATURDAY MORNING, AND AGAIN OVER NORTHEASTERN MENDOCINO
COUNTY SATURDAY EVENING. ADDITIONAL ISOLATED THUNDERSTORM ACTIVITY
WILL ALSO BE POSSIBLE DURING SUNDAY AFTERNOON OVER THE MOUNTAINS
OF TRINITY COUNTY AND NORTHEASTERN MENDOCINO COUNTY. A RED FLAG
WARNING FOR ABUNDANT LIGHTNING CAN`T BE COMPLETELY RULED OUT FOR
TRINITY COUNTY, VALID SUNDAY AFTERNOON, DUE TO A SOMEWHAT ROBUST
CONVECTIVE SIGNAL IN THE HI-RES ARW MODEL, AND COARSER-RES GFS.
HOWEVER, THE GENERAL ENSEMBLE CONSENSUS APPEARS MARGINAL AT THIS
TIME. /BRC/JMG


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...HAZARDOUS SEAS WARNING
     UNTIL 6 AM PDT EARLY THIS MORNING FOR PZZ450.

     GALE WARNING UNTIL 3 PM PDT THIS AFTERNOON FOR PZZ470.

     SMALL CRAFT ADVISORY UNTIL 3 PM PDT SUNDAY FOR PZZ475.

&&