Severe Thunderstorm Warning 7, NWS Sacramento, CA

AREA FORECAST DISCUSSION...CORRECTED FOR AVIATION DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
910 AM PST TUE MAR 14 2006

.DISCUSSION...WATER VAPOR IMAGERY SHOWS A TROUGH OF LOW PRESSURE
DIGGING ALONG THE WEST COAST...WITH A COLD FRONT MOVING ACROSS
NORTHERN CALIFORNIA AND A SECONDARY SYSTEM ON THE BACK SIDE OF THE
TROUGH OFF THE COAST.  RADAR IMAGERY SHOWS A BAND OF PRECIPITATION
SLOWLY MOVING THROUGH THE CENTRAL VALLEY AND INTO THE FOOTHILLS OF
THE SIERRA...WITH SHOWERS DEVELOPING BEHIND THIS BAND.  SNOW LEVELS
THIS MORNING ARE HOVERING AROUND 2500 FEET...WITH SNOW FALL TOTALS
RANGING BETWEEN 8 AND 12 INCHES OF SNOW ABOVE 3000 FEET.
HOWEVER...COLD AIR IS SEEPING INTO THE REGION BEHIND THE COLD
FRONT...AND AREAS ACROSS SHASTA COUNTY ARE SEEING A RAIN/SNOW MIX
AROUND 1500 FEET.  THIS COLD AIR WILL CONTINUE TO WORK ITS WAY
ACROSS THE REST OF AREA TODAY...WITH SNOW LEVELS FALLING TO BETWEEN
1500 AND 2000 FEET ACROSS THE AREA.  THEREFORE...WINTER STORM
WARNING REMAIN IN EFFECT FOR MUCH OF THE WARNING AREA THROUGH THIS
EVENING.

AS THIS MORNING/S BAND OF PRECIPITATION MOVES EAST...POCKETS OF
CLEARING WILL DEVELOP.  THE RESULTING SUN WILL HELP WARM THE
SURFACE...ENCOURAGING THE THE DEVELOPMENT OF SHOWERS AND ISOLATED
THUNDERSTORMS.  MEANWHILE...VISIBLE SATELLITE IMAGERY SHOWS A TIGHT
SECONDARY CIRCULATION JUST EAST OF 130 WEST.  AS THIS SYSTEM MOVES
INLAND LATER THIS AFTERNOON AND EVENING...IT WILL PROVIDE ADDITIONAL
DYNAMICS ACROSS THE REGION.  THEREFORE...HEAVY RAIN...SMALL
HAIL...AND GUSTY WINDS WILL BE POSSIBLE WITH THESE THUNDERSTORMS.
ALSO BELIEVE THAT THERE IS A POSSIBILITY THAT ISOLATED SEVERE
THUNDERSTORMS WILL OCCUR AS WELL.  CURRENT FORECAST LOOKS ON TRACK
THIS MORNING.  HOWEVER...MAY UPDATE JUST TO REMOVE MORNING WORDING.
CP

.PREVIOUS DISCUSSION ISSUED AT 415 AM PST...
IR SATELLITE IMAGES SHOW THAT THE MAIN CHANNEL OF THE MOISTURE PLUME
HAS SHIFTED EVER SO SLOWLY SOUTHEAST DURING THE PAST 12 HOURS. THE
LARGE AREA OF PRECIPITATION WITH COLD CLOUD TOPS OF MINUS 45 TO 50
DEGREES IS MOVING INTO THE RIDGE OVER THE NORTHERN ROCKIES. ENHANCED
CLOUDS CONTINUE TO BLOSSOM ALONG THE CREST OF THE ROCKIES WITH
WARMER AIR CURRENTLY DEPICTED OVER THE FORECAST AREA EXTENDING WEST
TO THE COAST. THE UPPER LOW IS JUST EAST OF 140W WITH A VORTICITY
MAXIMUM PUSHING INTO NORTHERN CALIFORNIA. A SECOND SHORT WAVE
INDICATED ON THE GFS AND SATELLITE IMAGES IS MOVING DOWN THE
BACKSIDE OF THE UPPER TROUGH AND SHOULD KICK-START THE SURFACE FRONT
AND COLDER AIR WHICH HAS BEEN NEARLY STATIONARY ALONG THE COAST
SINCE 00Z. THE STAGNANT PATTERN HAS MAINTAINED A BAND OF RAIN ACROSS
THE SOUTHERN SACRAMENTO VALLEY AND ADJACENT FOOTHILLS WITH RAINFALL
TOTALS BETWEEN 0.50-0.75 DURING THE PAST 6 HOURS AND 0.15 DURING THE
PAST 2 HOURS IN THE SACRAMENTO METROPOLITAN AREA. BUFKIT MODEL DATA
SHOW PRECIPITATION BECOMING SHOWERY OVER THE NORTHERN SACRAMENTO
VALLEY AFTER 16Z. SATELLITE DATA SUGGESTS THE TRANSITION IS ALREADY
OCCURRING. PLENTY OF COLD AIR STRATOCU BETWEEN THE UPPER LOW AND THE
COAST INDICATE CONTINUED PRECIPITATION FOR THE NEXT 24 HOURS. THE
WIND ADVISORY FOR THE NORTHERN AND CENTRAL SACRAMENTO VALLEYS CAN
PROBABLY BE CANCELLED BEFORE THE 6 AM EXPIRATION TIME AS WINDS HAVE
LOWERED BELOW ADVISORY CRITERIA ALTHOUGH THE SURFACE GRADIENT
SAC-RDD HAS BEEN HOLDING AT ABOUT 5 MB FOR THE PAST 3 HOURS.

THE TROUGH SHIFTS EAST OF THE AREA LATE TONIGHT WITH THE UPPER LEVEL
FLOW BECOMING MORE ZONAL. ALTHOUGH STILL UNSTABLE THERE SHOULD BE
LESS SHOWER ACTIVITY UNTIL WAA PRECIPITATION RETURNS THURSDAY AHEAD
OF THE NEXT TROUGH. HEAVIER PRECIPITATION THURSDAY NIGHT AND FRIDAY
WITH THE UPPER TROUGH SHOULD GIVE WAY TO WINDY SATURDAY AND DRIER
CONDITIONS FOR THE WEEKEND INTO EARLY NEXT WEEK. PFJ

&&

.AVIATION...A STRONG COLD FRONT MOVING ACROSS NORTHERN CALIFORNIA IS
GENERATING STRONG SOUTHERLY WINDS. THIS STORM IS STRONG ENOUGH TO
PRODUCE SOME THUNDERSTORMS WITH THE UNSTABLE AIR.  THE SNOW LEVELS
ARE FROM 1500 TO 2500, WITH SOME LOCALLY BELOW 1000 FEET POSSIBLE IN
THE VICINITY OF HEAVY SHOWERS OR THUNDERSTORM. MAINLY VFR CONDITIONS
TO AREAS OF MARGINAL VFR FOR VALLEY ROUTES AND ELEVATIONS BELOW 1500
FEET, WITH LOCAL IFR CONDITIONS NEAR ANY SHOWERS AND THUNDERSTORMS.
OTHERWISE, THE HIGHER ELEVATIONS HAVE WIDESPREAD IFR TO LIMITED IFR
CONDITIONS THROUGH AROUND 04Z, WITH SOME LOCAL IMPROVEMENTS EXPECTED
AFTER 04Z TONIGHT.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL MIDNIGHT PST TUESDAY NIGHT FOR BURNEY
BASIN / EASTERN SHASTA COUNTY-MOTHERLODE-NORTHEAST
FOOTHILLS/SACRAMENTO VALLEY-SHASTA LAKE AREA / NORTHERN SHASTA
COUNTY-WEST SLOPE NORTHERN SIERRA NEVADA-WESTERN PLUMAS
COUNTY/LASSEN PARK.

WINTER STORM WARNING UNTIL 6 PM PST TUESDAY FOR CLEAR
LAKE/SOUTHERN LAKE COUNTY-MOUNTAINS SOUTHWESTERN SHASTA COUNTY
TO NORTHERN LAKE COUNTY.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SACRAMENTO CA
700 AM PST TUE MAR 14 2006

CAZ013>019-063-064-066>069-151500-
SHASTA LAKE AREA/NORTHERN SHASTA COUNTY-
BURNEY BASIN/EASTERN SHASTA COUNTY-NORTHERN SACRAMENTO VALLEY-
CENTRAL SACRAMENTO VALLEY-SOUTHERN SACRAMENTO VALLEY-
CARQUINEZ STRAIT AND DELTA-NORTHERN SAN JOAQUIN VALLEY-
MOUNTAINS SOUTHWESTERN SHASTA TO NORTHERN LAKE COUNTIES-
CLEAR LAKE/SOUTHERN LAKE COUNTY-MOTHERLODE-
EAST FOOTHILLS/NORTH SACRAMENTO VALLEY-
WESTERN PLUMAS COUNTY/LASSEN PARK-WEST SLOPE NORTHERN SIERRA NEVADA-
700 AM PST TUE MAR 14 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR INTERIOR NORTHERN CALIFORNIA.

.DAY ONE...TODAY

A COLD LOW PRESSURE SYSTEM IS FORECAST TO BRING MORE SNOW OR SNOW
SHOWERS TO THE INTERIOR OF NORTHERN CALIFORNIA TODAY. SNOW LEVELS
WILL BE LOWERING TO 2000 TO 2500 FEET...RAISING LATE THIS AFTEROON
AND EVENING.

* WINTER STORM WARNING.......SEE WWUS46 KSTO - WSWSTO FOR DETAILS *

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

NO HAZARDOUS WEATHER IS 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/STO