Winter Storm in California, December 28 to 29, 2002

INTERIOR CENTRAL CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HANFORD CA
300 PM PST SAT DEC 28 2002

A STRONG UPPER PAC LOW DEPICTED BY WV NEAR 40N/129W IS CONTINUING TO
TRACK SLOWLY EAST SOUTHEAST. THE 12Z PROGS ALL SEEMED TO HAVE A
GOOD INITIALIZATION OF THIS OFFSHORE SYSTEM...HOWEVER THE GFS HAS
THE BEST HANDLE ON THE SLOWER TIMING OF IT/S EASTWARD PROGRESSION
SO HAVE FOLLOWED THE GFS FOR THE SHORT TERM. TWO COLD FRONTS ARE
ASSOCIATED WITH THIS SYSTEM. VIS LOOP INDICATING THE FIRST COLD FRONT
IS CURRENTLY MOVING SLOWLY EASTWARD INTO THE CENTRAL CA INTERIOR WITH
A SECOND COLD FRONT CURRENTLY OFFSHORE. BETWEEN THE TWO FRONTAL
SYSTEMS...METAR OBS ARE INDICATING SURFACE WINDS BETWEEN 20 AND 35
MPH ACROSS THE NORTHERN SAN JOAQUIN VALLEY. WITH P-GRADS PROGGED TO
STRENGTHEN ACROSS THE CENTRAL SAN JOAQUIN VALLEY LATER THIS
AFTERNOON...WILL KEEP THE WIND ADVISORY ISSUED BY THE PREVIOUS SHIFT
GOING INTO THIS EVENING.

AHEAD OF THE SECOND FRONT IS A BAND OF ENHANCED MODERATE TO HEAVY
PRECIPITATION INDICATED BY KMUX AND KDAX 88D/S. THIS PRECIPITATION
IS EXPECTED TO SPREAD INTO OUR CWFA THIS EVENING AND PRODUCE
WIDESPREAD RAIN AND HIGHER ELEVATION SNOW WITH SNOW LEVELS FALLING
RAPIDLY FROM AROUND 6000 FEET EARLY THIS EVENING TO AROUND 3500
FEET SUNDAY MORNING IN THE SOUTHERN SIERRAS TO AROUND 4500 FEET IN
THE KERN MOUNTAINS. MESO QPF/S INDICATING 1.5 TO 2 INCHES OF LIQUID
PRECIPITATION ACROSS THE SIERRAS THIS EVENING THROUGH SUNDAY
MORNING. THEREFORE...WILL CONTINUE THE WINTER STORM WARNING FOR THE
SOUTHERN SIERRAS FROM YOSEMITE PARK TO THE TULARE/KERN COUNTY
BORDER. ACROSS THE KERN MOUNTAINS QPF VALUES ARE MUCH LOWER...
GENERALLY AROUND A QUARTER OF AN INCH OR SO. SNOWFALL IN THE
KERN MOUNTAINS SHOULD REMAIN BELOW ADVISORY CRITERIA. WITH FAVORABLE
OROGRAPHIC LIFT TONIGHT AND SUNDAY...WILL RAISE POPS TO CATEGORICAL
ACROSS THE VALLEY AND SOUTHERN SIERRAS TONIGHT AND TO LIKELY ACROSS
THE SOUTHERN SIERRAS FOR SUNDAY. GFS INDICATING ANOTHER ZONE OF
THICKNESS PACKING CROSSING THE CWFA LATER TONIGHT. THIS IS THE
SECOND COLD FRONT WHICH WILL USHER IN A MODIFIED ARCTIC AIRMASS
INTO CENTRAL CA. MAX TEMPERATURES ACROSS MUCH OF THE CWFA WILL BE
FROM 10 TO 20 DEG F COOLER ON SUNDAY FROM TODAY WITH POST FRONTAL CAA
CONTINUING THROUGH THE DAY. EXPECT OROGRAPHIC PRECIPITATION TO TAPER
OFF LATE SUNDAY AS A FLAT RIDGE BRIEFLY BUILDS INTO CENTRAL CA.
UPPER LEVEL MOISTURE PROGS INDICATING 700-300 MB RH/S OF 70 TO 90
PERCENT SPREADING ACROSS THE CWFA MONDAY. WILL MENTION INCREASING
CLOUDS MONDAY WITH LOW POPS ACROSS THE MOUNTAINS NORTH OF KINGS
CANYON THEN SPREAD THE PRECIPITATION SOUTHWARD MONDAY NIGHT THEN
TAPER OFF TUESDAY AS RIDGING IS PROGGED TO REBUILD INTO CENTRAL CA.
THE STRONGEST MOISTURE AND BEST DYNAMICS WITH THIS SYSTEM ARE
EXPECTED TO REMAIN TO THE NORTH OF OUR CWFA. PROJECTED SNOW LEVELS
ARE EXPECTED TO BE HIGHER WITH THIS SYSTEM AS WELL...IN THE 6500 TO
8000 FOOT RANGE.  DS

FOR THE EXTENDED FORECAST PERIOD...WEDNESDAY THROUGH SATURDAY...
THE MEDIUM-RANGE MODELS CONTINUE TO FORECAST UPPER-LEVEL RIDGING
OVER CALIFORNIA BEHIND THE EXITING TROUGH. THE EXTENDED GFS
CONTINUES THE RIDGE TO BE DIRTY WITH 80-100 PERCENT RELATIVE
HUMIDITIES IN THE 500-300-MB LAYER OVER CENTRAL CALIFORNIA...BUT
DRIER AT LOWER LEVELS THROUGH THURSDAY. EXPECT DRY CONDITIONS OVER
THE REGION WEDNESDAY AND THURSDAY...WITH ABUNDANT CIRRUS OVER THE
REGION...AND SOME MID-LEVEL CLOUDS OVER THE MOUNTAINS. THE CIRRUS
DECK WILL PREVENT WIDESPREAD TULE FOG IN THE CENTRAL AND SOUTHERN
SAN JOAQUIN VALLEY...BUT PATCHY FOG WILL FORM...AND COULD BE LOCALLY
DENSE.

THE MEDIUM-RANGE MODELS STILL FORECAST THE NEXT SYSTEM TO REACH
CALIFORNIA FRIDAY. THE 12Z UKMET HAS A SHARPER TROUGH THAN THE GFS...
BUT TIMING IS SIMILAR. THE SYSTEM IS FORECAST TO MOVE THROUGH
CALIFORNIA FAIRLY RAPIDLY...WITH THE TROUGH AXIS MOVING THROUGH THE
REGION BETWEEN 12-24Z FRIDAY. DESPITE THE SHARPNESS OF THE TROUGH...
EVEN THE UKMET DOES NOT DROP THE 500-MB 5700-METER HEIGHT LINE SOUTH
OF FRESNO...SO THE BEST CHANCE FOR PRECIPITATION WOULD BE OVER THE
NORTHERN HALF OF THE HANFORD WARNING/FORECAST AREA. HOWEVER...THE
12Z UKMET SUGGESTS THAT THERE MAY BE SOME BACKING OFF OF THE TREND
SEEN ON THE EARLIER 00Z MODEL RUNS OF WEAKENING THE SYSTEM...SO MAY
HAVE TO EXTEND POP FIELDS SOUTHWARD FRIDAY DEPENDING ON TONIGHT/S
00Z SOLUTIONS.

FOR SATURDAY...UPPER-LEVEL RIDGING RETURNS TO CALIFORNIA WITH THE
EXTENDED GFS FORECASTING DRYING AT ALL LEVELS OF THE ATMOSPHERE.
HAVE GONE WITH PARTLY CLOUDY SKIES AND A COUPLE OF DEGREES WARMING.
COULD ALSO SEE SOME PATCHY VALLEY FOG SATURDAY MORNING...DEPENDING
ON HOW FAST THE TROUGH EXITS THE REGION AND CLOUDS BEGIN TO
DISSIPATE.  SANGER

.HNX...WINTER STORM WARNING FOR THE SOUTHERN SIERRA NEVADA NORTH OF
       KERN COUNTY THIS EVENING THROUGH SUNDAY MORNING.
    ...WIND ADVISORY FOR THE CENTRAL SAN JOAQUIN VALLEY THIS
       EVENING.

CAZ089>099-291400-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HANFORD CA
605 AM PST SAT DEC 28 2002

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE CENTRAL CALIFORNIA
INTERIOR.

.DAY ONE...TODAY

A WINTER STORM WARNING IS IN EFFECT FOR THIS AFTERNOON THROUGH
SUNDAY MORNING FOR THE SOUTHERN SIERRA NEVADA NORTH OF THE KERN
COUNTY LINE. (WWUS46 KHNX) A WIND ADVISORY IS IN EFFECT FOR THE
CENTRAL SAN JOAQUIN VALLEY FOR THIS AFTERNOON AND EVENING. (WWUS76
KHNX)

A STRONG WINTER STORM WILL BRING SNOW AND GUSTY WINDS TO THE HIGHER
ELEVATIONS OF THE SOUTHERN SIERRA NORTH OF THE KERN COUNTY LINE. IN
ADDITION...STRONG SOUTHEAST WINDS WILL DEVELOP ACROSS THE CENTRAL
SAN JOAQUIN VALLEY THIS AFTERNOON AND EVENING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

UNSETTLED WEATHER WILL CONTINUE THE FIRST PART OF THE WEEK AS A FAST
MOVING STORM PASSES OVER THE REGION. SHOWERS WILL OCCUR...MAINLY
IN THE NORTHERN SECTIONS LATE MONDAY INTO TUESDAY MORNING.

PATCHY DENSE FOG WILL RETURN TO THE SAN JOAQUIN VALLEY FOR
WEDNESDAY AND THURSDAY.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS TO THEIR LOCAL NATIONAL WEATHER SERVICE OFFICE.

KB