Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 182134
AFDHNX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
234 PM PDT SAT APR 18 2015

.SYNOPSIS...AN UPPER LEVEL AREA OF HIGH PRESSURE IS PRODUCING
DRY CONDITIONS AND ABOVE AVERAGE TEMPERATURES THROUGH THE WEEKEND
FOR THE VALLEY AND FOOTHILLS. A THREAT OF THUNDERSTORMS DOES EXIST
ALONG THE CREST OF THE SIERRA NEVADA SUNDAY THROUGH TUESDAY. AN
UPPER LEVEL AREA OF LOW PRESSURE MOVES SOUTH ALONG THE COAST
WEDNESDAY THROUGH FRIDAY. THIS WILL BRING A THREAT OF SHOWERS AND
THUNDERSTORMS TO THE ENTIRE CENTRAL CALIFORNIA INTERIOR BEGINNING
WEDNESDAY AND ENDING SATURDAY.

&&

.DISCUSSION...VISIBLE IMAGERY INDICATING A THIN BAND OF HIGH
ALTO-CUMULUS ASSOCIATED WITH A WEAK SHORTWAVE DROPPING SOUTHWARD
THROUGH CENTRAL CA AT THIS TIME. OTHERWISE SUNNY SKIES ARE
PREVAILING TODAY WITH TEMPERATURES CURRENTLY RUNNING 3-5 DEG F
ABOVE YDAY. THIS WEAK SHORTWAVE WILL PROVIDE THE HIGHER SIERRA
NEVADA IN THE YOSEMITE PARK AREA WITH ENOUGH INSTABILITY FOR
ISOLATED SHOWERS LATER THIS AFTERNOON.

MEANWHILE...AN UPPER RIDGE OFF THE WESTERN CONUS COAST IS
BUILDING INLAND INTO THE PAC NW WHILE A STRONGER SHORTWAVE
CURRENTLY SITUATED NEAR THE ORCA BORDER DROPS SOUTHWARD. THE 12Z
WRF IS INDICATING THAT THIS SHORTWAVE WILL RETROGRADE OFFSHORE
TONIGHT THEN DROP SOUTHWARD UNDERNEATH THE RIDGE ON SUNDAY AND
SUNDAY NIGHT FORMING A REX BLOCK OFF THE WESTERN CONUS CA COAST.
THE RIDGE OVER THE PAC NW WILL HELP KEEP AN UNSEASONABLY WARM
AIRMASS ACROSS OUR AREA ON SUNDAY AND MONDAY WITH TEMPERATURES
REMAINING WELL ABOVE NORMAL. THE UPPER LOW OFF THE SOCAL COAST
WILL PROVIDE OUR AREA WITH ENOUGH MID/UPPER LEVEL MOISTURE AND
INSTABILITY FOR A SLIGHT CHANCE OF AFTERNOON SHOWERS AND
THUNDERSTORMS OVER THE HIGHER ELEVATIONS OVER THE SOUTHERN SIERRA
NEVADA ON SUNDAY AND A BETTER CHANCE ON MONDAY AS WELL AS A SLIGHT
CHANCE OVER THE SOUTHERN SIERRA FOOTHILLS AND THE TEHACHAPI
MOUNTAINS.

THE WRF IS SHOWING ANOTHER SHORTWAVE TROUGH DEEPENING OFF THE PAC
NW COAST ON TUESDAY WHICH WILL PUSH THE REX BLOCK INLAND AND ALLOW
FOR SOME ADDITIONAL SHORTWAVE ENERGY TO DROP SOUTHWARD OFF THE CA
COAST...PROVIDING OUR AREA WITH SLIGHTLY COOLER TEMPERATURES ON
TUESDAY ALONG WITH A BETTER CHANCE OF MOUNTAIN CONVECTION AS
DYNAMICS BECOME MORE FAVORABLE.

THE MEDIUM RANGE MODELS ARE IN VERY POOR AGREEMENT ONCE AGAIN AS
THEY ARE HAVING A LOT OF DIFFICULTY HANDLING THE BREAKDOWN OF THE
REX-BLOCK AND EVENTUAL PATTERN CHANGE. THEREFORE...CONFIDENCE IN
THE FORECAST FROM WEDNESDAY ONWARD IS LOW.

THE 12Z GFS BROADENS THE LOW OFF THE COAST ON WEDNESDAY THEN
PUSHES IT SLOWLY INLAND ON THURSDAY WHILE ANOTHER SHORTWAVE DROPS
SOUTH OFF THE CA COAST WHICH IN TURN UNDERCUTS A BUILDING RIDGE
FORMING ANOTHER REX BLOCK OVER OUR AREA FOR LATE NEXT WEEK. THE
ECWMF ON THE OTHER HAND IS FURTHER OFFSHORE WITH THE SHORTWAVE
ENERGY DROPPING SOUTHWARD DURING THE MIDDLE OF NEXT WEEK WHICH
WOULD MEAN LESS MOISTURE AND DYNAMICS IMPACTING OUR AREA DURING
THE WEDNESDAY AND THURSDAY TIME FRAME. THE ECWMF THEN PUSHES A
NEGATIVELY TILTED TROUGH THROUGH CA NEXT FRIDAY AND SATURDAY WHICH
WOULD BRING MUCH COOLER TEMPERATURES AND BETTER CHANCES OF
PRECIPITATION WHILE THE GFS IS MAINLY DRY WITH ONLY SOME DIURNAL
MOUNTAIN CONVECTION AND MUCH WARMER.

OUR FORECAST IS MORE IN LINE WITH THE ENSEMBLE MEANS FOR
WEDNESDAY THROUGH SATURDAY WITH SLIGHTLY BELOW NORMAL TEMPERATURES
AND A CHANCE OF PRECIPITATION...AND A SLIGHT CHANCE OF DIURNAL
THUNDERSTORMS ON WEDNESDAY AND THURSDAY...THEN DECREASING CLOUDS
AND PRECIPITATION CHANCES ON FRIDAY AND SATURDAY.

&&

.AVIATION...VFR CONDITIONS AND LIGHT WINDS CAN BE EXPECTED
THROUGHOUT THE CENTRAL CALIFORNIA INTERIOR DURING THE NEXT 24
HOURS.

&&

.AIR QUALITY ISSUES...ON SUNDAY APRIL 19 2015... UNHEALTHY FOR
SENSITIVE GROUPS IN FRESNO COUNTY. FURTHER INFORMATION IS
AVAILABLE AT VALLEYAIR.ORG

&&

.CERTAINTY...

THE LEVEL OF CERTAINTY FOR DAYS 1 AND 2 IS HIGH.
THE LEVEL OF CERTAINTY FOR DAYS 3 THROUGH 7 IS LOW.

THIS INFORMATION IS PROVIDED AS PART OF A TRIAL PROJECT CONDUCTED
BY THE NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD.
CERTAINTY LEVELS INCLUDE LOW...MEDIUM...AND HIGH. PLEASE VISIT
WWW.WEATHER.GOV/HNX/CERTAINTY.PHP /ALL LOWER CASE/ FOR ADDITIONAL
INFORMATION AND/OR TO PROVIDE FEEDBACK.

&&

.CLIMATE...
             RECORDS
SITE DATE    HI_MAX:YEAR LO_MAX:YEAR HI_MIN:YEAR LO_MIN:YEAR

KFAT 04-18       95:1910     51:1955     62:1939     36:1941
KFAT 04-19       93:2009     54:1967     64:1938     35:1955
KFAT 04-20       96:2009     53:1957     62:1989     36:1896

KBFL 04-18       98:1910     55:1923     63:1954     35:1922
KBFL 04-19       98:1910     54:1967     62:1938     38:1996
KBFL 04-20       98:1906     59:2007     64:1939     36:1904
&&

.HNX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC...DS
AVN/FW...ANDERSEN
SYNOPSIS...ANDERSEN

WEATHER.GOV/HANFORD


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