FXUS66 KHNX 120455
AFDHNX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
855 PM PST FRI DEC 11 2009
.SYNOPSIS...A SERIES OF DISTURBANCES WILL MOVE THROUGH CENTRAL
CALIFORNIA OVER THE NEXT FEW DAYS PRODUCING PERIODS OF MODERATE
RAIN AND HEAVY SNOWFALL IN THE HIGHER ELEVATIONS.
&&
.DISCUSSION...REGIONAL RADAR AND IR IMAGERY SHOWING MULTIPLE BANDS
OF PRECIP OVER CENTRAL CALIFORNIA. THE FIRST BAND...MOVED INTO
THE HIGHER TERRAIN...WAS ENHANCED BY OROGRAPHIC EFFECT WHILE THE
SECOND BAND MOVED DOWN FROM THE COASTAL RANGE. WHILE THE SECOND
BAND WILL LOOKED LIGHT...BETTER ENHANCEMENT OCCURRED AS THE BAND
APPROACHED THE EASTERN SIDE OF THE VALLEY. THEREFORE...WILL
EXPECT A CONTINUATION OF THE PRECIPITATION AS THE WESTERLIES PUSH
MORE PIECES OF ENERGY INTO CENTRAL CALIFORNIA. WITH BOTH AND
TEMPERATURES AND DEW POINTS BOTH TRENDING UP THIS EVENING...WILL
SEE A WARMER NIGHT UNDER CLOUDS AND PRECIP. WILL EXPECT THE
FREEZING LEVEL TO STAY AT NEAR 5000 FEET OVERNIGHT ...AS THIS WILL
BE THE SNOW LINE BEFORE DAYBREAK. WHILE SNOW LEVELS MAY RISE ON
SATURDAY AS THE DISTRICT REMAINS IN THE WARM SECTOR...THE FRONTAL
PASSAGE EXPECTED IN THE AFTERNOON WILL FORCE SNOW LEVELS DOWN AS
BEGIN THE HEAVIER ACCUMULATION OF SNOW. THEREFORE...WILL KEEP THE
FORECAST AS IS AND SHOW LITTLE CHANGE IN SNOW LEVELS FOR MOST OF
SATURDAY AS TEMPERATURES MAY DO AS WELL. WINDS MAY BECOME AN ISSUE
OVER THE DISTRICT ON SATURDAY MODELS PROG MINUS 12MB TO MINUS 13MB
SURFACE PRESSURE GRADIENTS FROM SFO TO LAS. THIS WILL RESULT IN
STRONG SOUTHERLY WINDS UNTIL FRONTAL PASSAGE. WHILE NO UPDATES TO
THE FORECAST WILL BE DONE AT THIS POINT...WILL RE-ISSUE THE WINTER
STORM PRODUCTS AND SPECIAL WEATHER STATEMENTS.
&&
.PREV DISCUSSION... /ISSUED 407 PM PST FRI DEC 11 2009/
MOIST WESTERLY FLOW CONTINUES TO PROVIDE PERIODS OF SHOWERS
ACROSS THE DISTRICT. WATER VAPOR IMAGERY SHOWS SHORT WAVE PUSHING
THROUGH CENTRAL CA WITH A WEAK LOW SPINNING JUST OFF THE OFF COAST
OF THE CA/OR BORDER. EXPECT PERIODS OF GENERALLY LIGHT SHOWERS TO
AFFECT THE AREA THROUGH THE NIGHT. MODELS AGREE WITH ENERGY
ROUNDING GULF OF ALASKA LOW TO DIG SOUTHEAST TO OFF THE CENTRAL CA
COAST SATURDAY AFTERNOON. SYSTEM WILL TAP INTO STEADY MOISTURE
FEED ALONG WITH 30N AND WILL BE ACCOMPANIED BY A 130KT UPPER JET.
GOOD DYNAMICS AND FAVORABLE OROGRAPHICS WILL LEAD TO A PERIOD OF
MODERATE TO HEAVY PRECIPITATION ACROSS THE DISTRICT. MAY SEE A
LULL IN ACTIVITY SATURDAY MORNING BEFORE THINGS REALLY GET GOING
LATER IN THE DAY. FOCUS FOR PRECIP WILL BE SATURDAY NIGHT AND
EARLY SUNDAY. THE TROUGH AXIS WILL SWING THROUGH DURING THE PRE-
DAWN HOURS SUNDAY MORNING AND MAY BRIEFLY LOWER SNOW LEVELS TO
3500 FEET IN MARIPOSA COUNTY. IT LOOKS BORDERLINE FOR SNOW TO
AFFECT THE GRAPEVINE WITH CURRENT PROGS DIPPING THE SNOW LEVEL TO
NEAR 4500 FEET LATE SATURDAY NIGHT AND SUNDAY MORNING. HAVE
UPGRADED THE WINTER STORM WATCH FOR THE SOUTHERN SIERRA NEVADA TO
A WINTER STORM WARNING FROM NOON SATURDAY THROUGH 10 AM SUNDAY.
HAVE OPTED TO CONTINUE WITH A WINTER STORM WATCH FOR THE KERN
COUNTY MOUNTAINS BUT DELAYED THE TIMING TO SATURDAY EVENING
THROUGH SUNDAY MORNING. SHOWERY CONDITIONS WILL GRADUALLY DIMINISH
BEHIND THE TROUGH ON SUNDAY. NORTHWEST FLOW MAY HELP KEEP UPSLOPE
SHOWERS GOING SUNDAY NIGHT ALONG VALLEY FACING SLOPES...ESPECIALLY
IN TULARE AND KERN COUNTIES. UPPER RIDGING BUILDS IN MONDAY FOR
DRY AND STABLE CONDITIONS. BUT WITH THE RECENT RAINS WILL EXPECT
VALLEY FOG TO RETURN. TEMPERATURES WILL REMAIN COOL BUT NEAR
CLIMO.
&&
.AVIATION...BANDS OF PRECIP CONTINUE THIS AFTN MOVING THROUGH THE
EASTERN VALLEY INTO THE SIERRA AND ACROSS MUCH OF THE KERN
MOUNTAINS. THIS PRECIP WILL SUBSIDE THIS EVENING BUT SHOULD
REGENERATE LATE TONIGHT ON THE CUSP ON THE NEXT S/W NOW
APPROACHING THE CA COAST.
LIFR CONDS FOR CIGS AND VSBY PERSIST IN THE NORTHERN SJV AND DO
EXPECT THIS TO IMPROVE SOMEWHAT THIS EVENING ONCE THE NEXT S/W
APPROACHES. ELSEWHERE IN THE VALLEY EXPECT RAIN TO MOVE IN FROM THE
WEST AFTER 03-04Z. KEEP CIGS AND VSBY IN THE IFR-MVFR CATEGORY FOR
NOW THROUGH 18Z SATURDAY WITH PARTIAL CLEARING THEREAFTER. PARTIAL
MOUNTAIN OBSCURATIONS WILL CONTINUE ACROSS THE SIERRA AND TEHACHAPIS
THROUGH THE PERIOD. HEAVIER PRECIP WILL AFFECT THE SIERRA AFTER 18Z
SATURDAY.
&&
.AIR QUALITY ISSUES...NONE.
&&
.HNX WATCHES/WARNINGS/ADVISORIES...WINTER STORM WARNING FROM NOON
SATURDAY TO 10 AM PST SUNDAY FOR THE SIERRA NEVADA FROM YOSEMITE
TO KINGS CANYON AND THE TULARE COUNTY MOUNTAINS /CAZ096-097/.
WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY
MORNING FOR THE KERN COUNTY MOUNTAINS /CAZ095/.
&&
$$
PUBLIC...MOLINA
AVN/FW...BINGHAM
SYNOPSIS...TLM
WEATHER.GOV/HANFORD
