Severe Thunderstorm Warning 5, NWS Sacramento, CA

AREA FORECAST DISCUSSION...COR TYPO
NATIONAL WEATHER SERVICE SACRAMENTO CA
845 AM PST SUN MAR 16 2003

FRONTAL BAND IS CONTINUING TO MOVE INTO WESTERN CALIFORNIA THIS
MORNING. MEASURABLE RAIN ALREADY IN THE SAC AREA. PALE COMPARED TO
THE 4 INCHES THAT FELL IN LA YESTERDAY...NEARLY THEIR TOTAL IN
2001-02. RAIN GAGES SHOW .05 TO .40 INCH AMOUNTS PAST 9 HOURS IN THE
COASTAL RANGE FROM LAKE COUNTY INTO WESTERN SHASTA COUNTY WITH .10 OR
LESS IN PLUMAS AND BUTTE COUNTIES. THE NORTHERN END OF THE FRONT HAS
WEAKENED BUT THE SOUTHERN END FROM MONTEREY BAY TO THE DELTA IS
ENHANCING WITH LIGHT TO MODERATE REFLECTIONS. CURRENT RADAR SHOWS
SCATTERED SHOWERS MOVING ACROSS THE NORTHERN CWA. THIS SOUTHERN AREA
IS UNDERNEATH THE MAX DIVERGENCE ALOFT ASSOCIATED WITH THE 165KT
PACIFIC JET STREAM CORE REACHING EAST OF 130W...ORIENTED FROM WEST
TO EAST AND EXTENDING INTO SOCAL. THIS JET AXIS REMAINS NEARLY
STATIONARY TODAY KEEPING UPPER DIVERGENCE OVER THE FORECAST AREA
INTO THE AFTERNOON. UNLIKE YESTERDAY WHEN NVA MID LEVEL SUBSIDENCE
AND DRYING AS SEEN ON KOAK 00Z/16 SOUNDING SUPPRESSED CONVECTION
FROM WEST TO EAST DURING THE DAY...TODAY WE HAVE CONTINUED WEAK PVA
OVER THE REGION AS A WEAK SHORT WAVE TRAVERSES THROUGH. 12Z KOAK
SOUNDING IS AGAIN UNSTABLE WITH LI ZERO AND PRECIPITABLE WATER .74
INCHES. 12Z ETA BUFKIT SOUNDINGS SHOW THIS PROFILE CONTINUING INTO
THE EARLY EVENING FOR THE CENTRAL VALLEY WITH CAPE VALUES RANGING
FROM UNDER 100 AT RED BLUFF TO ABOUT 250 J/KG AT SAC. ALSO TODAY THE
SURFACE CONVERGENCE IS NOT FORECAST TO BE NEARLY AS DIVERGENT
(SLIGHTLY CONVERGENT UPVALLEY FLOW AND EVEN SOUTH AT FAIRFIELD) AS
WE SAW YESTERDAY IN THE DELTA...IMMEDIATE SAC AREA SOUTH INTO
STOCKTON AS WESTERLY FLOW HAS GONE TO NIL SINCE 24 HOURS AGO
(SFO-RNO NEAR ZERO). BEST SURFACE CONVERGENCE TODAY IS AGAIN IN THE
CENTRAL AND NORTHERN SAC VALLEY WHERE A WEAK LEE SIDE TROF IS
FORECAST BY THE 12Z ETA. SPC PLACES US IN GENERAL THUNDER TODAY.

SO MORNING FOCUS WILL BE THE FRONTAL BANDS SLOW MOVEMENT EASTWARD
AND THEN DESTABILIZATION IN THE AFTERNOON DUE TO SURFACE
HEATING...WEAK COLD AIR ADVECTION AND CONTINUED SYNOPTIC SUPPORT FOR
ADDITIONAL SHOWERS AND SOME THUNDERSTORMS. 12Z GFS CONTINUES TO BE
SLIGHTLY FASTER...STRONGER (SUCH AS H85-7 OMEGA) AND FURTHER NORTH
WITH THE OMEGA FIELD PLACING IT OVER THE SOUTHERN 2/3 OF OUR
FORECAST AREA ALONG THE MAIN FRONTAL BANDS EASTWARD MOVEMENT. BY 00Z
TODAY BOTH MODELS SIMILAR WITH DEEPER MOISTURE ALONG THE EAST SIDE
IN -2 TO -8 H7 OMEGA FIELD WHILE H85 OMEGA AND NEARLY SATURATED
LAYER LINGERS OVER THE EAST SIDE VALLEY INTO THE MOTHERLODE. THE SLOW
MOVEMENT AND CONVECTIVE DEVELOPMENT SHOULD GIVE THE FORECAST AREA
THE EXPECTED RAINFALL AND SNOWFALL ESPECIALLY IN THE SOUTHERN
FORECAST AREA...GENERALLY .05 TO .30 TOTALS. SATELLITE SUPPORTS THIS
IDEA ALONG WITH THE IDEA OF AFTERNOON MOIST CONVECTION. CONVECTIVE
NATURE WILL LEAD TO SPOTTY TOTALS IN THE NORTHERN ZONES. SNOW LEVELS
RUNNING FROM 3500 IN THE NORTH TO NEAR 4500 FT ON I-80 WILL REMAIN
NEAR THESE LEVELS. PRECIPITATION WILL CONTINUE OVER THE EAST SIDE OF THE
VALLEY INTO THE SIERRA NEVADA THIS EVENING AS BOTH GFS AND ETA
LINGER H7 OMEGA IN THIS AREA BEFORE ENDING. MORNING UPDATES TO
INCREASE CHANCE OF RAIN FOR THE SOUTH AND EAST ZONES. ADD SNOW
ACCUMULATIONS BACK TO THE FORECAST WHICH WILL MATCH WELL WITH THE
2-4 INCHES FORECAST BY WFO RENO IN THE SIERRA NEVADA BORDER.
SOUTHERN END OF FRONT AND ADDITIONAL CONVECTION SHOULD SLIDE INTO
THIS AREA THROUGH THE EVENING HOURS IN WEAK SOUTHWEST FLOW.

NEXT WAVE WILL DROP SOUTH OF THE REGION TONIGHT AS THE UPPER JET
SAGS SOUTHWARD PLACING INCREASING SUBSIDENCE AND NORTHERLY FLOW OVER
NORCAL LATE TONIGHT INTO MONDAY. ONLY PRECIP ON MONDAY WILL BE A FEW
IF ANY LIGHT SHOWERS OVER THE SIERRA CREST. NORTHERLY FLOW SURFACE
AND ALOFT UNDER SUBSIDENCE WILL PROVIDE DRY WEATHER INTO TUESDAY.

MODELS CONTINUE TO CHANGE ON THE STRENGTH OF THE TROF FOR MID WEEK
BUT STILL APPEARS THURSDAY IS THE DAY FOR PRECIP.

.STO...NONE

KBBX RADAR IS CURRENTLY DOWN.

TARDY

CAZ013>019-063-064-066>069-171500-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SACRAMENTO CA
700 AM PST SUN MAR 16 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR INTERIOR NORTHERN CALIFORNIA.

.DAY ONE...TODAY

THE AIRMASS WILL BE UNSTABLE AGAIN ACROSS THE SOUTHERN VALLEY AREAS
THIS AFTERNOON WHICH COULD TRIGGER ISOLATED THUNDERSTORMS ACROSS
PORTIONS OF THE SACRAMENTO AND NORTHERN SAN JOAQUIN VALLEYS.

THE SNOW ADVISORY FOR THE MOUNTAINS OF SHASTA COUNTY HAS BEEN
CANCELLED.  ADDITIONAL SNOWFALL ACCUMULATIONS IN THE AREA ARE NOT
EXPECTED TO BE MORE THAN A COUPLE OF INCHES. REFER TO THE WINTER
WEATHER MESSAGE (WWUS46 KSTO WSWSTO) FOR DETAILS.

.DAYS TWO THROUGH SEVEN

NO HAZARDOUS WEATHER EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

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

THE LATEST WEATHER INFORMATION IS AVAILABLE ON THE INTERNET AT
(LOWER CASE): HTTP://WWW.WRH.NOAA.GOV/SACRAMENTO

RANDY HARTLEY