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
000
FXUS66 KEKA 242217
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
317 PM PDT THU APR 24 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL INTRODUCE A COLDER AND
MORE UNSTABLE AIR MASS TO THE REGION TONIGHT...RESULTING IN A
SLIGHT CHANCE FOR THUNDERSTORMS THROUGH FRIDAY. ANOTHER WEAK
FRONT WILL BRING LIGHT RAIN AMOUNTS TO THE AREA THIS WEEKEND.

&&

.DISCUSSION...A WEAK COLD FRONT MOVED ACROSS THE REGION TODAY
PROVIDING LIGHT RAIN MAINLY NORTH OF CAPE MENDOCINO. THE FRONT
WILL EXIT THE AREA TONIGHT BUT OCCASIONAL SHOWER ACTIVITY WILL
CONTINUE INTO THE EVENING. AN UPPER LEVEL TROUGH WILL DIG
SOUTHWARD OVER NORTHERN CALIFORNIA LATE TONIGHT INTO FRIDAY
INTRODUCING A COLDER AND MORE UNSTABLE AIR MASS CONDUCIVE TO
THUNDERSTORM DEVELOPMENT. UPPER LEVEL DYNAMICS FAVOR A MORE
UNSTABLE ENVIRONMENT WITH POSITIONING OF THE UPPER LEVEL JET
PROMOTING DIVERGENCE ALOFT FRIDAY MORNING AS THE TROUGH AXIS
TRAVERSES OVER THE FORECAST REGION. MUCAPE REMAIN SUFFICIENT
FOR LOW TOPPED CONVECTION WITH LIFTED INDICES DROPPING TO -2C.
THE COLDER AIR MASS WILL ENCOURAGE HAIL DEVELOPMENT WITH 500MB
TEMPERATURES RANGING FROM -28C TO -31C. CONDITIONS WILL STABILIZE
FRIDAY EVENING AS THE TROUGH AXIS SHIFTS EAST OF THE AREA...PUTTING
A HALT TO THUNDERSTORM DEVELOPMENT. WITH A COOLER AIR OVER THE
REGION FRIDAY NGT THERE IS A SLIGHT CHANCE FOR FROST IF THE
ATMOSPHERE DRIES OUT SUFFICIENTLY AND SKIES CLEAR OUT. RIGHT NOW
IT APPEARS THERE WILL BE TOO MUCH LOW LEVEL HUMIDITY AND CLOUDS
FOR WIDESPREAD FROST EVENT.

MODELS WERE IN GOOD AGREEMENT WITH A BROAD FLAT RIDGE HOLDING OVER
THE REGION THROUGH MIDDAY SAT BEFORE ANOTHER FRONT ARRIVES. THERE
IS REALLY GOOD AGREEMENT BETWEEN THE GFS...ECMWF AND NAM12 ON
MORE PRECIP ARRIVING SAT NIGHT...AFTER ABOUT 5PM SAT. WE HAVE RAISED
THE PRECIP CHANCES IN ALL ZONES. AMOUNTS LOOK TO BE ON THE LIGHT
SIDE BUT STILL ENOUGH TO MAKE THINGS WET. THE PRECIP SHOULD WIND
DOWN ON SUNDAY...THOUGH MOISTURE AND A FEW SHOWERS WILL STILL BE
AROUND AS THE FLOW GOES WESTERLY BEHIND THE TROUGH.

DRIER CONDITIONS WILL LIKELY RETURN SUNDAY NIGHT INTO MONDAY AS
A RIDGE BEGINS TO BUILD OVER THE REGION. THE GFS AND ECMWF DO SHOW
SOME HIGH AND MID LEVEL MOISTURE WITH A WARM FRONT CLIPPING THE
AREA ON MONDAY...WITH VERY MINIMAL CHANCES FOR PRECIP NEAR THE
OREGON BORDER. WE SHOULD SEE BETTER DRYING AND WARMING TUE AND
WED AS THE RIDGE STRENGTHENS BOTH AT THE SURFACE AND ALOFT. THE
RIDGE SHOULD DOMINATE THROUGH THE END OF THE NEXT WEEK...WITH
TEMPERATURES GENERALLY NEAR OR SLIGHTLY ABOVE LATE APRIL NORMALS.
THE MODELS HINT AT A WEAK TROUGH APPROACHING NEXT WEEKEND...BUT IT
IS LOOKING TOO DRY AND STABLE FOR PRECIP AT THIS TIME.

&&

.AVIATION...AFTERNOON RADAR SHOWS SCATTERED SHOWERS OVER PORTIONS OF
NORTHWEST CALIFORNIA. THIS IS BRINGING VFR AND LOCAL MVFR.
CONDITIONS SHOULD DETERIORATE THIS EVENING AND OVERNIGHT AS ANOTHER
RAIN BAND SLOWLY MOVES OVER THE AREA. ADDITIONALLY, INSTABILITY WILL
GENERATE A SLIGHT CHANCE OF THUNDERSTORMS, ESPECIALLY TOWARD
DAYBREAK.

&&

.MARINE...NEARSHORE BUOY OBSERVATIONS THIS AFTERNOON ARE REPORTING
LIGHT WINDS AND SEAS AROUND 7-9 FT. THERE WAS NO ASCAT PASS OVER OUR
WATERS THIS AFTERNOON. AS THE STORM SYSTEM CONTINUES TO MOVE INLAND
THE WINDS WILL STAY LIGHT AND THE WAVES WILL CONTINUE TO SUBSIDE,
SO ALLOWED THE SCA TO EXPIRE. MODELS REMAIN IN GOOD AGREEMENT
SHOWING A SERIES OF SYSTEMS BRINGING PERIODS OF MODERATE WINDS TO
OUR WATERS THE NEXT FEW DAYS. KEPT BLENDING THE WINDS HEAVILY WITH
THE CONS MODEL. LONG PERIOD WESTERLY SWELL GENERATED FROM A DISTANT
STORM SHOULD BEGIN MOVING THROUGH OUR WATERS TONIGHT INTO FRIDAY.
THOUGH, THIS SWELL STILL HASN`T PASSED OFFSHORE BUOY #2. AFTER IT
DOES WE WILL KNOW IF THE FORECAST IS ON TRACK OR IF IT NEEDS TO BE
ADJUSTED. THE LONG PERIOD SOUTHERLY SWELL THE MODELS ARE SHOWING FOR
THIS WEEKEND STILL IS A BIT OVERDONE, SO CAPPED IT AT 3 FT.
FOLLOWING INTERNAL COORDINATION, PUT OUT A MARINE STATEMENT AND
WEATHER STORY GRAPHIC FOR THIS, MAINLY BECAUSE IT`S THE FIRST
"LARGE" SOUTHERLY SWELL OF THIS SEASON. AGAIN, THE FORECAST OF
THIS SWELL MAY BE CHANGED IF IT IS OBSERVED TO BE LARGER THAN
EXPECTED WHEN IT STARTS PASSING THE SOUTHERN CALIFORNIA BUOYS.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...NONE.
&&

$$

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

FOLLOW US ON FACEBOOK AND TWITTER AT:
HTTP://WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.EUREKA.GOV
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.