Severe Thunderstorm Warning 22, NWS Sacramento, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
240 PM PDT TUE JUL 22 2003

HOT WEATHER CONTINUES TO BE THE STORY FOR NORCAL. ALREADY 100 AT
DOWNTOWN SAC MAKING IT THE 7TH STRAIGHT DAY OF 100+. THE NORTHERN
VALLEY WELL ON ITS WAY TO 110F. WEAK DELTA TRICKLE CONTINUES WITH
10KT AT FAIRFIELD AND THE MARINE DEPTH HAS SHRUNK TO NEAR 1000 FEET.
ONSHORE PGRAD STILL SLIGHTLY STRONGER. THUNDERSTORMS HAVE POPPED
EARLIER AND MUCH MORE WIDESPREAD IN THE CENTRAL AND SOUTHERN SIERRA
NEVADA AS EXPECTED. ALREADY A STRONG CELL IN ALPINE COUNTY WITH VILS
IN THE 50S AND 60S. MAX GRID VIL 73 KG/M2 NEAR THE TUOLUMNE AND
ALPINE BORDER. HUGE HAIL POTENTIAL LIKELY. LOTS OF LIGHTNING ON THE
NLDN (140 STRIKES PER 15 MIN). WORKSTATION ETA FROM THE 12Z RUN
PRODUCES ABOUT 1500 J/KG OF SURFACE TO MEAN 100MB CAPE (NCAPE 19
CM/S2)...OBVIOUSLY THIS IS BEING REALIZED AS THE WEAK H7 INVERSION
AND LOW LEVEL CIN IS OVERCOME BY THE HIGH TERRAIN IN THIS AREA AND
INCREASING WEAK PVA AND PW...ALONG WITH THE STEERING FLOW BECOMING
MORE SOUTHEAST SHIFTING THE MAX LOW LEVEL CONVERGENCE TO THE CREST
AND JUST WESTWARD. IT WILL BE TOUGH FOR PARCELS TO REACH THEIR LFC
OVER OTHER PARTS OF THE MOUNTAINS LATER TODAY...BUT CERTAINLY THE
NORTHERN SIERRA NEVADA AND SOUTHERN CASCADES HAVE THE POTENTIAL
WHERE SOME CU IS EVIDENT. WORK STATION ETA AND GFS SHOW MID LEVEL
BLOW OFF/OUTFLOWS DRIFTING QUICKLY INTO THE FOOTHILLS...NORTHERN SJ
VALLEY AND SOUTHERN SAC VALLEY THIS EVENING AND THEN CARRIED INTO
THE COASTAL RANGE WITH ONLY WEAK LIFT TO SUPPORT ONGOING SHOWERS AND
ISOLATED THUNDERSTORMS. DELTA BREEZE SHOULD BE A LITTLE STRONGER
TONIGHT BUT WITH CLOUD COVER MIN TEMPS WILL REMAIN IN THE 70S MANY
VALLEY LOCALES ONCE AGAIN.

THE 12Z/18Z ETA...12Z WSETA AND 12Z GFS ARE DIFFERENT IN HOW THEY HANDLE
INVERTED AND ELONGATED SHORT WAVE TROF ENERGY THAT ARRIVES FROM 06
TO 18Z TIME FRAME. BUFKIT SOUNDING ON THE WSETA REVEAL ALMOST
CLASSIC ELEVATED CONVECTION (OVER THE NOCTURNAL INVERSION) PROFILE
WITH STEEP LAPSE RATES AND MOISTURE FROM 600 TO 400-MB AT ALL VALLEY
POINTS LATE TONIGHT. RUNNING THE ELEVATED CONVECTION TOOL YIELDS
ECAPE OF OVER 300 J/KG IN SPOTS...EVEN OVER SAC. AT THE SAME TIME
TONIGHT A PRECIPITABLE WATER PLUME FROM AROUND THE STRONG UPPER
RIDGE ADVECTS INTO NORCAL WITH TOTALS OF 1.3 TO 1.6 INCHES (HIGHEST
ON THE GFS). GOES ALREADY SHOWS 1.5 INCHES OVER SOCAL. GIVEN THE
CONDITIONALLY UNSTABLE ENVIRONMENT IT STILL APPEARS THE AVAILABLE
UPPER DIVERGENCE WILL BE ENOUGH TO DESTABILIZE THE AIR MASS AND
PRODUCE AT LEAST ISOLATED SHOWERS AND THUNDERSTORMS TONIGHT MOVING
FROM EAST TO WEST ACROSS THE SOUTHERN 2/3 OF OUR CWA. BEST OMEGA
AREAS ARE TO THE SOUTHWEST NEAR PT CONCEPTION AND OVER THE NORTHERN
SIERRA NEVADA...SO MUCH OF THE CWA IS ONLY IN WEAK DYNAMICS...BEST
12Z-18Z WED. LIGHTNING POSES A CONCERN WITH FIRE WEATHER EVEN THOUGH
STRONGER CELLS WILL HAVE HEAVY RAINFALL. FAILURE TO LOOK AT
SOUNDINGS IN THESE EVENTS WILL LEAD TO UNFORECAST CONVECTION. VERY
MOIST AIR WILL RESULT IN ALTOCUMULUS CASTELLANUS ON WEDNESDAY AND
ANVIL DEBRIS. THIS MAY AFFECT TEMPS AS WELL AS THE POSSIBLE INCREASE
TO THE MARINE LAYER/ONSHORE FLOW ON WEDNESDAY AS PROGGED BY THE
ETA...EVEN THOUGH H85 TEMPS ONLY DROP ABOUT 1 TO 2C. STRONGER
ONSHORE AND CLOUDS MAY PREVENT THE SAC AREA FROM REACH 100F.
WORKSTATION ETA INCREASES CAPE ALONG THE COASTAL RANGE WEDNESDAY
AFTERNOON AND THIS AREA WHICH HAS BEEN VOID OF THUNDERSTORMS MIGHT
GET ITS BEST CHANCE WEDNESDAY AFTERNOON INTO THE NIGHT HOURS. CAPE
VALUES OVER THE SIERRA NEVADA PROGGED TO REACH AS HIGH AS 1800 J/KG
PER BUFKIT. ENOUGH INSOLATION THROUGH CLOUD BREAKS SHOULD REALIZE
THIS.

ENERGY THAT MOVES ALONG THE CA CENTRAL COAST TONIGHT AND TOMORROW
RETURNS AS AN OPEN WAVE ON THE GFS WEDNESDAY NIGHT. WITH A LARGE
AREA OF HIGH PW OVER NORCAL THIS WOULD LEAD TO ANOTHER ELEVATED
THUNDERSTORM AND SHOWER EVENT...AND POSSIBLY MORE ORGANIZED. THIS
TRACK OF THE SHORT WAVE PRODUCES THE BEST OMEGA...MODERATE...ALONG
THE COASTAL AREAS AND THEN INTO THE NORTHERN MOUNTAINS ON THURSDAY.
ETA AND GFS CONTINUE TO DIFFER WITH THE STRENGTH OF THIS FEATURE BUT
WE LEAN TO THE GFS WITH ITS GOOD PAST PERFORMANCES IN THESE SUBTLE
FEATURED SUBTROPICAL PATTERNS. THIS WILL ALSO FACTOR INTO A STRONGER
DELTA PUSH WEDNESDAY NIGHT WITH THE MARINE LAYER PROGGED TO RISE TO
ABOUT 2000 FEET TO FINALLY DROP MIN TEMPS BACK INTO THE 60S FOR MANY
LOCALES AND KEEP MANY TEMPS IN THE 90S ON THURSDAY. SYNOPTIC COOLING
OF ABOUT 2C ARRIVES ON THURSDAY AS WELL. STEERING FLOW BEGINS TO
VEER TO THE SOUTHWEST THURSDAY SHUNTING THUNDERSTORM DEVELOPING TO
THE CREST AND FAR NORTH. COOLING TREND FROM STRONGER ONSHORE FLOW
AND DECREASING CONVECTION WILL TREND INTO SATURDAY. SYNOPTIC COOLING
IS SUBTLE WITH H85 TEMPS HOVERING AT 22-25C WHILE WEAK TROFFINESS
LINGER OVER FAR NORCAL. DOMINATE UPPER RIDGE RETROGRADES BACK TO
CALIFORNIA SUNDAY THROUGH TUESDAY. THIS LEADS TO AIR MASS WARMING
AND A RETURN OF SOUTHEAST FLOW OVER THE SOUTHERN SIERRA NEVADA ZONES
WHERE WE PLACED A SLIGHT CHANCE OF TSRA. DIFFERENCES IN THE
PLACEMENT OF THE UPPER RIDGE MAKE IT TOUGH TO CALL IF TEMPS WILL GET
EXTREME AGAIN AND IF THE THUNDERSTORM THREAT WILL MAKE IT MUCH WEST
OF THE SIERRA NEVADA CREST.

.STO...NONE.

BLU BB 072/085 069/083 066 65233
    BUUUU 079/065 078/065 080/066 082/067 080 21000000000
RBL BB 076/105 073/101 066 65012
    BUUUU 093/065 093/065 095/065 097/066 095 20000000000
SAC BB 067/098 062/093 059 65221
    BUUUU 092/058 092/058 094/058 096/059 094 00000000000

TARDY

CAZ013>019-063-064-066>069-231400-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SACRAMENTO CA
620 AM PDT TUE JUL 22 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR INTERIOR NORTHERN CALIFORNIA.

.DAY ONE...TODAY

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS OVER THE MOUNTAINS THIS
AFTERNOON...AND OVER THE ENTIRE REGION TONIGHT...OTHERWISE NO
HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...

ISOLATED THUNDERSTORMS ARE POSSIBLE ACROSS MAINLY THE HIGHER TERRAIN
ON WEDNESDAY AND THURSDAY...OTHERWISE NO HAZARDOUS WEATHER IS
EXPECTED AT THIS TIME.

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

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