Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 221501
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
801 AM PDT TUE JUL 22 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST
COMBINED WITH INSTABILITY WILL BRING THE THREAT OF SCATTERED
THUNDERSTORMS TO THE INTERIOR THIS AFTERNOON AND EVENING. SOME OF
THE STORMS MAY PRODUCE SMALL HAIL AND HEAVY RAIN. HIGH PRESSURE
BUILDING AT THE END OF THE WEEK WILL BRING A WARMING AND DRYING
TREND TO THE INTERIOR.

&&

.UPDATE...ISOLATED THUNDERSTORMS HAVE FORMED OVER THE SAN
FRANCISCO BAY AREA AND SHOULD SLIDE NORTH INTO SOUTHERN AND
EASTERN PORTIONS OF MENDOCINO COUNTY THIS MORNING. THE UPPER
LEVEL LOW TRIGGERING THESE THUNDERSTORMS WILL BE THE FORCING THAT
INITIATES MORE THUNDERSTORMS LATER THIS AFTERNOON ACROSS TRINITY
COUNTY...SOME OF WHICH COULD BE STRONG TO POSSIBLY SEVERE. HAVE
UPDATED THE FORECAST TO EXPAND THUNDERSTORM COVERAGE FARTHER SOUTH
INTO SOUTHERN MENDOCINO COUNTY AND TO INCREASE POPS ACROSS THE
LOWER ELEVATIONS OF TRINITY COUNTY.

IF THUNDERSTORMS BECOME MORE NUMEROUS THIS MORNING OVER THE SAN
FRANCISCO BAY AREA AND EXPAND NORTH INTO MENDOCINO COUNTY...FIRE
WEATHER CONCERNS WILL INCREASE. THIS WILL BE MONITORED CLOSELY
TODAY. RPA

&&

.PREV DISCUSSION......ISSUED AT 344 AM PDT...

DISCUSSION...AN UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST
COMBINED WITH INSTABILITY OVER NORTHWEST CALIFORNIA WILL BRING THE
THREAT OF SCATTERED THUNDERSTORMS THIS AFTERNOON AND EVENING.
MODELS SHOW GOOD INSTABILITY FOR SEVERAL PARAMETERS, ESPECIALLY
THIS AFTERNOON. MOISTURE IS ALREADY IN THE AREA, CONFIRMED BY
SHOWERS ON THE LOCAL RADAR THIS MORNING AND HIGH CLOUDS SEEN ON
SATELLITE MOVING OVER THE AREA. PWATS THIS AFTERNOON MAY APPROACH
1 INCH, WHICH IS GOOD FOR THIS TIME OF YEAR. BULK SHEAR SHOULD BE
FAVORABLE HELPING TO GENERATE STRONG STORMS. MINIMAL CAPPING SHOWN
ON THE FORECAST SOUNDINGS SHOULD HELP. THE TWO LACKING FACTORS ARE
THE JET STREAM IS NOT IN THE PRIME POSITION AND THE SYNOPTIC SETUP
IS NOT PERFECT. BUT ENOUGH PARAMETERS ARE IN PLACE THAT SCATTERED
THUNDERSTORMS COULD DEVELOP THIS AFTERNOON, ESPECIALLY WHEN MODELS
SHOW AN UPPER LEVEL DISTURBANCE MOVING OVER THE AREA. SOME OF
THESE STORMS COULD GENERATE SMALL HAIL AND HEAVY RAIN. SEVERE
STORMS MIGHT BE A STRETCH GIVEN THE BEST CONDITIONS ARE TO OUR
NORTHEAST. BUT THIS WILL BE MONITORED. STORM MOTION SHOULD PUSH
THESE STORMS INTO SISKIYOU COUNTY. STORMS WILL DECREASE THIS
EVENING AS THE ATMOSPHERE STABILIZES. BY WEDNESDAY THE UPPER LEVEL
TROUGH MOVES FURTHER INLAND AND DRIER, MORE STABLE AIR WILL MOVE
OVER NORTHWEST CALIFORNIA. TOWARDS THE END OF THE WEEK THE FOUR
CORNERS RIDGE EXPANDS BACK INTO NORTHWEST CALIFORNIA, ALLOWING
INLAND TEMPERATURES TO RISE INTO THE LOW 100S. MODELS STILL SHOW A
CUT- OFF LOW FORMING TO OUR SOUTHWEST LATE THIS WEEK. THIS WILL
CONTINUE TO BE WATCHED FOR THE NEXT THREAT OF THUNDERSTORMS.

AVIATION...VSBY REMAINS UP AT COASTAL AIR STRIPS THIS MORNING AND
IS EXPECTED TO DO SO THROUGH THE DAY AS AN UPPER TROUGH KEEPS THE
LOWER ATMOSPHERE WELL MIXED. CIGS WILL RANGE BETWEEN IFR AND MVFR
THIS MORNING THEN BECOME VFR BY LATE MORNING. WINDS WILL REMAIN
LIGHT OUT OF THE SOUTH WHILE ON THE EASTERN SIDE OF AN OFFSHORE
UPPER LOW. INTERIOR AIR STRIPS WILL REMAIN VFR THROUGH THE DAY. NW
CAL WILL HAVE A CHANCE OF A LIGHT SHOWER THROUGH THE DAY AS A
PULSE ENERGY SWEEPS ACROSS THE REGION. THE INTERIOR MOUNTAINS MAY
EXPERIENCE A CHANCE OF THUNDERSTORMS AS THIS ENERGY MOVES THROUGH.
BFG

MARINE...AN UPPER TROUGH DIGGING TOWARD THE WESTERN UNITED STATES
THIS MORNING CONTINUES TO CAUSE A WEAK SURFACE PRESSURE GRADIENT
OVER THE NW CAL COASTAL WATERS. THIS IS ALLOWING FOR LIGHT WINDS
AND LOW SEAS. OBSERVATIONS THIS MORNING INDICATE WEAK SOUTHERLY
FLOW. THIS IS PRECEDING A WEAK FRONT WHICH MODELS HAVE LIMPING
ACROSS THE AREA LATE WEDNESDAY NIGHT. BEHIND THIS FRONT HIGH
PRESSURE WILL AGAIN BUILD TOWARD THE COASTAL WATERS CAUSING AN
INCREASE IN NORTHERLY CONDITIONS. BFG

&&

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

$$

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