Area Forecast Discussion
Issued by NWS Eureka, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
000
FXUS66 KEKA 022252
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
352 PM PDT SUN AUG 2 2015

.SYNOPSIS...SCATTERED SHOWERS AND THUNDERSTORMS REMAIN POSSIBLE
THROUGH THIS EVENING ACROSS PARTS OF NORTHWEST CALIFORNIA. THE
COAST WILL SEE LOW CLOUDS AND FOG RETURN TONIGHT.

&&

.SHORT TERM...(TONIGHT THROUGH WEDNESDAY) POOR MODEL
INITIALIZATION AND THE SUBSEQUENT DIFFERING RESULTS IN THE REAL
WORLD VERSUS THE MODEL WORLD CONTINUE TO PLAGUE THE SHORT TERM
FORECAST. WITH CONFIDENCE IN THE OUTPUT REMAINING LOW, LEFT MOST
OF THE FORECAST UNCHANGED, WITH ONLY MINOR TWEAKS IN THE VARIOUS
FIELDS. DETAILS ON THE THUNDERSTORMS CAN BE READ IN THE FIRE
WEATHER DISCUSSION BELOW.

A COOLING TREND IS EXPECTED FOR THE FIRST HALF OF THE WEEK AS THE
DIGGING UPPER TROUGH DRIVES COOLER AIR SOUTH. WITH THE TROUGH OFF
THE COAST DURING THE FIRST PART OF THE WEEK, THE MARINE LAYER WILL
DEEPEN, ALLOWING MOIST COASTAL AIR TO PENETRATE FARTHER INLAND.

.LONG TERM...(THURSDAY THROUGH MONDAY) THE CORE OF THE UPPER LOW
THAT HAS BEEN SPINNING OFF THE CALIFORNIA COAST FOR SOME TIME NOW
WILL MOVE TOWARD NORTHWEST CALIFORNIA THURSDAY INTO FRIDAY. BOTH
THE GFS AND ECMWF INDICATE THAT THE DIFFLUENCE ON THE EAST SIDE OF
THE UPPER LOW WILL MOVE OVER CENTRAL AND NORTHWEST CALIFORNIA
THURSDAY INTO FRIDAY LEADING TO IMPROVED DYNAMICS AND INSTABILITY
OVER THE INTERIOR MOUNTAINS. ANOTHER ROUND OF STORMS WILL BE
POSSIBLE AS THIS LOW MOVES THROUGH WITH STORMS MOVING VERY
SLOWLY...LIKELY BEGINNING ON FRIDAY. CONFIDENCE REMAINS LOW ON THE
TIMING OF THE UPPER LOW DESPITE THE AGREEMENT IN THE MODELS
CONSIDERING MODELS ARE GENERALLY POOR AT DETERMINING THE TRACK OF
CLOSED LOWS OFF THE CALIFORNIA COAST.

DEPENDING ON THE TRACK OF THE LOW...THUNDERSTORM CHANCES MAY
LINGER THROUGH FRIDAY NIGHT INTO SATURDAY. IF STORMS DO FIRE THERE
WILL BE FIRE WEATHER CONCERNS AND IMPACTS TO THE CURRENT WILDFIRE
SUPPRESSION WORK ACROSS THE INTERIOR.

BOTH THE GFS AND ECMWF INDICATE A DEEPER TROUGH WILL ADVANCE
TOWARD THE PACIFIC NORTHWEST SUNDAY INTO EARLY NEXT WEEK BRINGING
SOME COOLER TEMPERATURES AND POSSIBLY A DEEPER MARINE LAYER WHICH
COULD PUSH FAR INLAND. IF THIS OCCURS IT WOULD PUSH MORE MOISTURE
INTO THE INTERIOR AND RESULT IN HIGHER HUMIDITY VALUES. THERE IS
THE POTENTIAL FOR ANOTHER ROUND OF SHOWERS OR THUNDERSTORMS OVER
THE NORTHERN REACHES OF TRINITY COUNTY AS THIS TROUGH
APPROACHES...BUT IN GENERAL LITTLE IF ANY PRECIPITATION IS
EXPECTED LATE IN THE WEEKEND THROUGH MID NEXT WEEK. THIS WILL BE
MONITORED CLOSELY. RPA

&&

.AVIATION...CLOUDS REMAIN ENTRENCHED OVER THE COASTAL WATERS THIS
AFTERNOON THOUGH SOME LIGHT OFFSHORE FLOW HAS RESULTED IN POCKETS
OF CLEARING NEAR THE COAST. IN GENERAL...MVFR TO IFR CONDITIONS
WILL PERSIST AT THE COASTAL TERMINALS THROUGH AT LEAST MONDAY
MORNING. WITH AN UPPER TROUGH NEARBY...LIFR CONDITIONS ARE NOT
ANTICIPATED TONIGHT WITH A DEEPER MARINE LAYER. THE DEEPER MARINE
LAYER WILL ALLOW CLOUDS TO SPREAD INLAND AND LIKELY REACH UKI LATE
TONIGHT INTO EARLY MONDAY MORNING.

MANY WILDFIRES ACROSS THE REGION ARE RESULTING IN AREAS OF SMOKE
AND REDUCED VISIBILITIES. INTERIOR DEL NORTE...INTERIOR
HUMBOLDT...AND TRINITY COUNTIES WILL LIKELY HAVE IFR OR LIFR
CONDITIONS AT TIMES CAUSED BY THE SMOKE. RPA

&&

.MARINE...WINDS AND SEAS WILL REMAIN BELOW OUR CRITERIA FOR
ADVISORIES FOR SMALL CRAFT THROUGH MONDAY. OVER MOST OF THE AREA
WINDS WILL REMAIN LIGHT WITH SPEEDS NOT EXPECTED TO EXCEED 10 KT.
SEAS WILL ALSO REMAIN LOW WITH HEIGHTS AROUND 2 TO 4 FT WITH
PERIODS AROUND 8 SECONDS. WEAK LOW PRESSURE SOUTHWEST OF CAPE
MENDO WILL SLOWLY DRIFT SOUTHWARD ON MON AS HIGH PRESSURE BEGINS
TO BUILD TOWARD THE WEST COAST. WIND FIELDS STILL LOOK TO REMAIN
SOUTHERLY NEAR SHORE THOUGH AS A TROUGH PERSISTS. GUIDANCE
SUGGESTS NORTHERLY WINDS APPROACHING ADVISORY LEVEL OF 15 TO 25 KT
ON TUE IN PZZ470. WINDS INCREASE MORE ON WED AND THU WITH A
CORRESPONDING INCREASE IN SHORT PERIOD WIND SEAS. ON THU THE GFS
INDICATES LOW END GALES...WITH GUSTS TO 35 TO 40KT POSSIBLE OVER
THE OUTER WATERS. IT IS STILL SEVERAL DAYS OUT AND THE MODELS CAN
CHANGE. CONFIDENCE IS MODERATELY HIGH WINDS AND SEAS WILL INCREASE
AROUND MID WEEK. THE EXACT MAGNITUDE IS STILL SKETCHY.

&&

.FIRE WEATHER...CONTINUED THE RED FLAG WARNING FOR FIRE WEATHER
ZONES 203, 204, AND NORTHERN PORTIONS OF 283. AN UPPER LEVEL LOW
WEST OF THE NORTHWEST CALIFORNIA COAST IS BRINGING INSTABILITY TO
OUR AREA WHILE ALSO HELPING PULL MONSOONAL MOISTURE IN FROM THE
SOUTH. THIS IS GENERATING A THREAT OF THUNDERSTORMS FOR OUR AREA.
EVEN THOUGH RADAR HAS BEEN RELATIVELY CLEAR ACROSS NORTHWEST
CALIFORNIA THROUGH 2230Z, SHORT TERM MODELS CONTINUE TO INDICATE
THUNDERSTORMS COULD DEVELOP LATE THIS AFTERNOON THROUGH EARLY THIS
EVENING, POSSIBLY GENERATING ABUNDANT LIGHTNING. THE MAIN LIMITING
FACTOR CONTINUES TO BE SMOKE OVER MOST OF THE DISTRICTS, WHICH IS
HELPING TO INHIBIT THUNDERSTORM FORMATION AND LIMIT THEIR AREAL
COVERAGE IN OTHER PARTS OF THE STATE. HOWEVER, THE SMOKE HAS
CLEARED ACROSS INTERIOR MENDOCINO COUNTY AND PARTS OF HUMBOLDT,
TRINITY, AND DEL NORTE COUNTIES. THIS SHOULD HELP INCREASE HEATING
AND DESTABILIZE THE ATMOSPHERE IN THESE AREAS. THIS IS BEING
CONFIRMED BY VISIBLE SATELLITE IMAGERY, WHICH SHOWS CLOUDS TRYING
TO FORM IN SOME OF THESE LOCATIONS. RIDGES AND MOUNTAIN PEAKS IN
LOCATIONS WITH CLEAR SKIES WILL ACT AS POINTS TO HELP DEVELOP
LOCALIZED THUNDERSTORMS (DUE TO HOT AFTERNOON TEMPERATURES AND
LOCAL LIFT). ANY STORMS THAT DO FORM WILL MOVE SLOWLY AND WILL
PRODUCE LITTLE, IF ANY PRECIPITATION. MODELS STILL INDICATE THE
POTENTIAL FOR SOME THUNDERSTORMS ACROSS MAINLY FIRE WEATHER ZONES
203, 204, AND 283 MONDAY AND TUESDAY AFTERNOONS/EVENINGS. HOWEVER,
THE POTENTIAL IS LOWER THAN TODAY AND ONLY ISOLATED STORMS ARE
POSSIBLE. AS THIS OCCURS, THE THREAT OF CONVECTIVE ACTIVITY WILL
DIMINISH. BUT MUST NOTE THAT THE MODELS HAVE BEEN PERFORMING
POORLY, SO CONFIDENCE IN THUNDERSTORM FORMATION IS LOW. INTERIOR
DAYTIME TEMPERATURES SHOULD BE SLIGHTLY BELOW AVERAGE THROUGH
WEDNESDAY. OVERNIGHT RH RECOVERIES WILL CONTINUE TO BE FAIRLY GOOD
THE NEXT FEW NIGHTS, EXCEPT FOR THE HIGHEST RIDGETOPS.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...

CA...

RED FLAG WARNING FOR CAZ003-004.

NORTHWEST CALIFORNIA COASTAL WATERS...NONE.

&&

$$

VISIT US AT HTTP://WWW.WEATHER.GOV/EUREKA

FOLLOW US ON FACEBOOK AND TWITTER AT:
HTTP://WWW.FACEBOOK.COM/NWSEUREKA
HTTP://WWW.TWITTER.COM/NWSEUREKA


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.