Winter Storm in California, April 20 to 21, 2001

WESTERN NEVADA AND EASTERN CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
900 PM PDT FRI APR 20 2001

MODERATE PRECIP MOVING INTO SIERRA AND SPREADING INTO EXTREME WESTERN
NEVADA THIS EVENING. SPOTTER REPORTS INDICATING UP TO 2 INCHES IN THE
LOWER WESTERN VALLEYS WHILE 4-6 INCHES UPPER ELEVATIONS.  SOME
THUNDERSTORMS MOVING INTO YOSEMITE AREA BUT NOTHING YET MOVING OVER
THE CREST.  IR LOOP SHOWS INCREASING ENHANCED AREA OVER DOUGLAS COUNTY
AND A LITTLE NORTHWARD. THIS AIDED BY GOOD UPPER DIVERGENCE AND AS
UPPER LOW STILL MOVING SLOWLY SOUTH DOWN THE COAST. FLOW A LITTLE MORE
SOUTHERLY OVER CWA ALLOWING LESS SHADOWING SO LOWER VALLEYS SEEING
BETTER PRECIP. MODELS ANALYZED VORTICITY FIELD WELL BUT DIFFER EVEN BY
12Z SATURDAY MORNING AS TO WHERE THE MAIN VORT MAX WILL BE LOCATED.
ETA KEEPS IT JUST ALONG THE COAST WHILE AVN/NGM BEGIN BRINGING IT
INLAND. OBVIOUSLY THE FURTHER WEST WILL RESULT IN LESS SNOWFALL OVER
THE SIERRA. CURRENT SATELLITE TREND IS MORE SOUTHERLY SO WOULD SEEM TO
INDICATE ETA MAY BE CLOSER. YET 12HR QPF ARE REASONABLY CLOSE WITH
0.4-0.6 INCHES OVER SIERRA AND WITH SOME OROGRAPHICS WILL SEE DECENT
AMOUNTS ALONG THE CREST THOUGH MAYBE NOT CURRENT FORECAST AMOUNTS IN
THE SIERRA VALLEYS. SHOULD BE ABLE TO REACH THE LOWER END FORECAST
AMOUNTS SO WILL NOT CHANGE WARNING. ONLY CONCERN WOULD BE FOR RENO
AREA SOUTH THROUGH LYON COUNTY WHERE RADAR/SATELLITE DATA INDICATING
MODERATE PRECIP UNDER GOOD UPPER DIVERGENCE. SPOTTER REPORTS LOWER
VALLEYS SNOW NOT STICKING BUT FOOTHILLS ACCUMULATING. WILL UPDATE TO
INDICATE LOCALLY HIGHER ACCUMULATIONS.  SHOULD SEE PRECIP END BY 12Z
NORTH AND LINGER THROUGH 18Z SOUTH. DP

.REV...WINTER STORM WARNING THROUGH TONIGHT ZONE 2/72.
       WINTER STORM WARNING UNTIL 10AM SATURDAY ZONE 73

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