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
000
FXUS66 KEKA 021619 AAA
AFDEKA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE EUREKA CA
919 AM PDT SUN AUG 2 2015

.SYNOPSIS...SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE
AGAIN TODAY ACROSS MUCH OF NW CALIFORNIA. WHILE AT THE COAST LOW
CLOUDS AND FOG WILL GREET THE DAY THEN DISSIPATE THROUGH THE
MORNING.

&&

.FIRE WEATHER UPDATE...THROUGH COORDINATION WITH THE GACC AND
INTERNAL DISCUSSION, UPGRADED THE FIRE WEATHER WATCH TO A RED
FLAG WARNING. TODAY REMAINS A GOOD SET UP FOR SCATTERED
THUNDERSTORMS ACROSS FIRE WEATHER ZONES 203-204-283. HOWEVER,
SMOKE OVER MOST OF THE DISTRICTS MAY INHIBIT THUNDERSTORM
FORMATION AND COVERAGE TO MORE LIMITED AREAS. BUT THE SMOKE IS
CLEARING ACROSS INTERIOR MENDOCINO COUNTY AND EASTERN PARTS OF DEL
NORTE COUNTY, WHICH SHOULD HELP INCREASE HEATING AND DESTABILIZE
THE ATMOSPHERE IN THESE AREAS. THE SAME CAN BE SAID FOR SOME OF
THE HIGHEST PEAKS ACROSS INTERIOR HUMBOLDT AND TRINITY COUNTIES
OVER THE NEXT FEW HOURS, WHICH CAN LEAD TO LOCALIZED THUNDERSTORM
FORMATION. ANY STORMS THAT DO FORM WILL MOVE SLOWLY AND WILL
PRODUCE LITTLE, IF ANY PRECIPITATION. BUT MUST NOTE THAT THE
MODELS HAVE BEEN PERFORMING POORLY SO FAR AND LIKELY HAVE NOT
CHANGED WITH THE LATEST RUNS. CONFIDENCE IN WIDESPREAD
THUNDERSTORM FORMATION IS LOW.

&&

.PREV DISCUSSION......ISSUED AT 444 AM PDT...

DISCUSSION...POOR MODEL INITIALIZATION OVER THE EASTERN PACIFIC
HAS PROVEN CHALLENGING FOR THE FORECAST TODAY AND THE PREVIOUS FEW
DAYS. CONFIDENCE IN MODEL SOLUTION DETAILS IS LOW, SO HAVE OPTED
TO MAINTAIN THE ONGOING FORECAST WITH LIMITED TO NO CHANGES. WE
ARE STILL LOOKING AT ANOTHER DAY OF POTENTIAL CONVECTION FOR NW
CALIFORNIA AS AN UPPER LOW HAS ANCHORED ITSELF ABOUT 550 MILES
WEST OF EUREKA AND IS SWINGING LOBES OF ENERGY AROUND ITS SE
SEMICIRCLE. THIS UPPER LOW IS ALSO REACHING DOWN INTO THE SUB-
TROPICS PULLING PULSES OF MOISTURE NORTHWARD, WHILE PROVIDING
INSTABILITY IN THE LOBES OF ENERGY. MORNING WATER VAPOR SATELLITE
IMAGERY SHOWERS A PLUME OF MOISTURE MAKING ITS WAY TOWARD NOR CAL
FROM THE SOUTH. THIS SHOULD ARRIVE AROUND MID MORNING, IN
CONJUNCTION WITH A SHORTWAVE. THIS WILL BRING A SHOT OF TSTMS TO
MUCH OF NW CAL WITH EXCEPTION OF SW MENDOCINO WHERE DRY AIR ALOFT
IS IN PLACE AND SHOULD HELP TO INHIBIT CONVECTIVE DEVELOPMENT. THE
BULK OF THIS MOISTURE IS LOCKED UP IN THE MID TO UPPER LEVELS,
WHICH MEANS IF ANY TSTMS DEVELOP THEY WILL LIKELY BE DRY AT THE
SURFACE. MOISTURE ALSO CONTINUES TO STREAM IN FROM THE SE, WHICH
HAS BROUGHT TSTMS TO THE NORTHERN SIERRA`S AND NORTH CENTRAL CAL
OVERNIGHT. SOME OF THIS MOISTURE SHOULD BECOME ENTRAINED INTO THE
AFOREMENTIONED SHORTWAVE, BRINGING A CONTINUED THREAT OF TSTMS TO
TRINITY COUNTY TODAY. THE UPPER LOW IS FORECAST TO BECOME ABSORBED
INTO A DIGGING UPPER TROUGH OUT OF THE NE GULF OF ALASKA. AS THIS
OCCURS, THE THREAT OF CONVECTIVE ACTIVITY WILL DIMINISH.

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.
THE SECOND HALF OF THE WEEK WILL BRING ANOTHER CHANCE OF TSTMS TO
NW CAL INTERIOR AS THERE IS POTENTIAL FOR A CUT OFF LOW TO DEVELOP
OFF THE CENTRAL CAL COAST, WHICH WOULD AGAIN PULL IN SUB-TROPICAL
MOISTURE AND PROVIDE NEEDED LIFT.

AS STATED ABOVE, THERE WERE LIMITED CHANGES MADE TO THE ONGOING
FORECAST. TEMPS WILL FALL OVER THE COMING DAYS, DROPPING BELOW
NORMAL FOR MANY INTERIOR LOCATIONS WHILE CONVECTIVE ACTIVITY
DIMINISHES. BFG

AVIATION...STRATUS HAS PUSHED FARTHER INTO THE COASTAL RIVER
VALLEYS OVERNIGHT. MOST SITES UNDER THE LOW CLOUD DECK HAVE BEEN
REPORTING IFR CEILINGS ALONG WITH INTERMITTENT MIST. HIGH
RESOLUTION MODELS CONTINUE TO INDICATE HIGH BOUNDARY LAYER
HUMIDITIES THIS MORNING EASING UP DURING THE AFTERNOON. SUSPECT
THERE WILL BE SOME IMPROVEMENT AT THE COASTAL AIRPORTS THIS
AFTERNOON...THOUGH CONFIDENCE IS NOT HIGH IT WILL LAST VERY LONG
AT KACV AND KCEC. PROFILES INDICATE A DEEPER MOIST LAYER PUSHING
ONSHORE BY THIS EVENING AND THEN INTO THE RIVER VALLEYS TONIGHT.
THERE IS A CHANCE LOW CLOUDS WILL SPREAD INTO UKIAH MUNI EARLY
THIS MORNING AND AGAIN EARLY MONDAY MORNING.

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. LATEST 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
LATEST 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.

&&

.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.