Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 062138
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
238 PM PDT MON JUL 6 2015

.SYNOPSIS...LOW CLOUDS AND FOG WILL AGAIN HUG THE COASTAL REGIONS
TODAY. MEANWHILE...A DISTURBANCE OFF THE CALIFORNIA COAST WILL
BRING A CHANCE OF SHOWERS AND THUNDERSTORMS TO PORTIONS OF
INTERIOR NW CALIFORNIA. THIS DISTURBANCE WILL MAINTAIN A THREAT OF
UNSETTLED WEATHER THROUGH THE WEEK.

&&

.DISCUSSION... AN UPPER LOW OFF THE COAST HAS BEEN ACTING TO
DEEPEN THE MARINE LAYER AND SHOULD CONTINUE TO DO OVER THE NEXT
FEW DAYS. THIS WILL HELP TO BRING LOW CLOUDS DEEPER THROUGH
INTERIOR VALLEYS, ESPECIALLY THOSE THAT HAVE COASTAL INFLUENCE.
THE MAIN STORY OF THE WEEK WITH BE THE THREAT OF THUNDERSTORMS
ACROSS NW CALIFORNIA AS A RESULT OF THE PASSING UPPER LOW. (ALSO
SEE FIRE WEATHER DISCUSSION BELOW) THIS UPPER LOW WILL BRING
SUFFICIENT INSTABILITY IN MOIST SOUTHERLY FLOW. MODELS CONTINUE TO
WAVER ON PLACEMENT OF THE BEST CONVECTIVE FORCING, WHICH IS
TYPICAL FOR THE WEST COAST DUE TO LACKING OBSERVATIONS OVER THE
EASTERN PACIFIC OCEAN. AS THIS LOW CROSSES MORE DATA RICH REGIONS
TO OUR SOUTH, WE SHOULD GET A BETTER SNAPSHOT ON ITS STRUCTURE.
REGARDLESS, MODELS HAVE BEEN FAIRLY CONSISTENT THAT THIS UPPER LOW
WILL PROVIDE THE NEEDED FORCING TO GENERATE THUNDERSTORMS, SOME OF
WHICH MAY BE STRONG. TUESDAY AND WEDNESDAY LOOK TO BE THE MOST
ACTIVE DAYS WITH REGARDS TO CONVECTIVE ACTIVITY. AT THIS POINT THE
LOW WILL BE SLIDING BY TO OUR SOUTH AND WILL BE FEEDING IN PLENTY
OF MOISTURE, ALONG WITH COOLER AIR ALOFT. DEPENDING WHERE THIS LOW
ACTUALLY TRACKS, IT COULD LINE UP INTERIOR PORTIONS OF NW
CALIFORNIA FOR STRONG THUNDERSTORMS. MODELS CONTINUE TO BE IN
AGREEMENT WITH CAPE IN THE 2000 J/KG RANGE, STEEPENING LAPSE
RATES, PLENTY OF MOISTURE, LIFTED INDEX AROUND NEGATIVE 3C, AND
SUFFICIENT SHEAR. CONDITIONS LOOK TO BE COMING TOGETHER TO BRING
STRONG THUNDERSTORMS TUESDAY AND WEDNESDAY WITH GUSTY WINDS, HEAVY
RAIN, AND SMALL HAIL. ONE ITEM TO WATCH WILL BE HOW HIGH THE
FREEZING LEVELS WILL BE. TOO HIGH AND HAIL WILL BE VERY LIMITED,
BUT RAIN WILL VERY HEAVY. FREEZING LEVELS DOWN AROUND 12 TO 13
KFT, WE COULD SEE HAIL IN THE ONE INCH RANGE, POSSIBLY LARGER,
ALONG WITH FREQUENT LIGHTNING. WITH EVERYTHING LOOKING LIKE IT IS
COMING TOGETHER FOR STRONG THUNDERSTORMS, WENT AHEAD AND ADDED IN
WORDING OF GUSTY WINDS, SMALL HAIL, AND HEAVY RAIN FOR TUESDAY
AFTERNOON. IT MAY BE NEEDED TO ADD SIMILAR WORDING IN FOR
WEDNESDAY IF TUESDAY PANS OUT. THE WILD CARD WILL BE WHAT HAPPENS
OVERNIGHT TUESDAY INTO WEDNESDAY. MODELS ARE SHOWING CONVECTIVE
CELLS CONTINUING OVERNIGHT. THE OTHER CHALLENGE IS STORM MOTION.
AS THE LOW SLIPS BY TO THE SOUTH, STORM MOTIONS SHOULD BE FROM
EAST TO WEST ACROSS NW CALIFORNIA. THIS WOULD BRING THE CHANCE OF
SOME SHOWERS MOVING OUT OVER THE COAST AND THEN OFFSHORE. WENT
AHEAD AND ADDED THIS INTO THE FORECAST WITH SHOWERS OVER THE
COASTAL PLAINS AND COASTAL WATERS. KEPT THESE AS SHOWERS INSTEAD
OF THUNDERSTORMS THINKING THAT ONCE THESE CELLS MOVE OVER COOLER
SURFACE TEMPERATURES AND WATERS THE STRONG INSTABILITY SHOULD NOT
BE THERE. FOR THE REST OF THE WEEK, WEAK INSTABILITY REMAINS IN
PLACE. HAVE MAINTAINED A SLIGHT CHANCE OF THUNDERSTORMS EACH
AFTERNOON THROUGH THE WEEK. TEMPERATURES WILL REFLECT THE COOLING
AIR MASS, BOTH HIGHS AND LOWS. OVERALL, SHOULD BE AN INTERESTING
WEEK AS WE LOOK AT THE POTENTIALLY FOR STRONG THUNDERSTORMS.
BFG/JT


&&

.AVIATION...MVFR CONDITIONS AND LIGHT WINDS WILL CONTINUE AT KCEC
AND KACV THROUGH THE EARLY EVENING DUE TO REDUCED CEILINGS. MVFR TO
IFR CONDITIONS WILL OCCUR AT KCEC AND KACV OVERNIGHT AS CEILINGS AND
VISIBILITIES DIMINISH. LIGHT WINDS TO CALM CONDITIONS WILL PREVAIL
AT KCEC AND KACV OVERNIGHT. VFR CONDITIONS AND LIGHT WINDS TO CALM
CONDITIONS WILL CONTINUE AT KUKI THROUGH TUESDAY.


&&

.MARINE...A LOW PRESSURE AREA AND TROUGH TRAVERSING OFFSHORE ACROSS
THE NORTHEASTERN PACIFIC OCEAN CONTINUES TO MAINTAIN A WEAK PRESSURE
GRADIENT ACROSS THE WATERS. THEREFORE LIGHT WINDS AND LOW SEAS WILL
CONTINUE ACROSS THE WATERS THIS WEEK.


&&

.FIRE WEATHER...FINE FUELS WILL GRADUALLY MOISTEN OVER THE NEXT
FEW DAYS AS A COMBINATION OF SCATTERED SHOWERS, CLOUD COVER,
COOLER TEMPERATURES AND HIGH RH VALUES BLANKET THE REGION.
ALTHOUGH A FAIR AMOUNT OF LIGHTNING IS POSSIBLE OVER THE NEXT FEW
DAYS.....DUE TO THE EXPECTATION OF WETTER FUELS...FIRE WEATHER
WATCHES OR RED FLAG WARNINGS WILL NOT BE NECESSARY.

&&

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

$$

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