Tornado and Hail in Nevada, August 1, 2002

WESTERN NEVADA AND EASTERN CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
850 AM PDT THU AUG 1 2002

THE AIRMASS IS UNSTABLE TODAY WITH LIGHT SOUTHWEST FLOW ALOFT.
THERE IS A WEAK VORT LOBE NEAR THE CA COAST WHICH COULD HELP TO KEEP
SOME CONVECTION GOING TONIGHT BUT THE MAIN FOCUSING MECHANISM TODAY
OTHER THAN TERRAIN WILL PROBABLY BE CONVERGENCE INTO THE THERMAL
TROUGH.  MODELS SHOW THIS MOVING JUST EAST OF THE RENO AREA BY MID
AFTERNOON.  SOME STABILIZATION IS PROJECTED FOR FRIDAY BUT IT LOOKS
LIKE IT WILL REMAIN UNSTABLE ACROSS MINERAL AND SOUTHERN LYON
COUNTIES AND POSSIBLY EASTERN MONO AND DOUGLAS COUNTIES AS WELL.
SATURDAY LOOKS STABLE WITH INCREASING SOUTHWEST FLOW UNLESS MORE
MOISTURE COMES IN WITH THE SMALL UPPER LOW THAN IS SHOWN BY THE ETA
AND AVN.  COREY

IN THE EXTENDED...SUN TO WED.  MODELS ARE STILL INSISTING ON
DEVELOPING A CONSOLIDATED TROUGH OVER THE WESTERN U.S. ON SUNDAY
WITH STRONG...DRY AND STABLE SOUTHWEST FLOW.  THIS WILL BE THE
BEGINNING OF A COOLING TREND AS TEMPS DROP BELOW NORMAL FOR THE
FIRST TIME IN QUITE AWHILE.  THE TOUGH THEN CONTINUES TO DEEPEN ON
MONDAY AND TUESDAY.  MODELS SHOW A WEAK FRONT MOVING INTO THE
NORTHERN PORTION OF THE CWA ON MONDAY.  THE TROUGH BEGINS TO WEAKEN
ON TUESDAY THEN ON WEDNESDAY THE MAIN PORTION OF IT BEGINS TO LIFT
OUT TO THE NORTHEAST WITH HEIGHTS BEGINNING TO RISE.  WINDS WILL
DECREASE SOME AND TEMPS START TO WARM UP AGAIN.

.REV...NONE.

FFP INDEX - PROTOTYPE FLASH FLOOD POTENTIAL OUTLOOK

                                FOR

  NORTHEAST CALIFORNIA, THE EAST CENTRAL SIERRA, AND WESTERN NEVADA

THIS EXPERIMENTAL PRODUCT IS ISSUED DAILY BY 6 AM AS A TEXT VERSION
AND ALSO SENT TO THE WEB AS A GRAPHIC.  NEITHER PRODUCT IS UPDATED.
SEE THE WEB ADDRESS AT THE BOTTOM OF THIS PAGE TO ACCESS THE FFP
GRAPHIC.

THIS TEXT PRODUCT WILL BE ISSUED IN THIS FORMAT UNTIL OCTOBER 1,
2002.  AT THAT TIME, EQUIVALENT INFORMATION WILL BE INCORPORATED
INTO A MULTI-HAZARD HAZARDOUS WEATHER OUTLOOK (HWO) THAT WILL BE
ISSUED EACH MORNING BY ALL NATIONAL WEATHER SERVICE OFFICES.

FFP NUMBERS BELOW IN THIS TEXT PRODUCT ARE THE MOST REPRESENTATIVE
VALUE FOR EACH FORECAST ZONE AS DISPLAYED IN THE GRAPHICAL FFP.

ZONE     FFP TODAY-FRIDAY     FORECAST AREA

NVZ001           3-2          MINERAL AND SOUTHERN LYON COUNTIES
NVZ002-CAZ072    2-1          GREATER LAKE TAHOE AREA
NVZ003           2-1          GREATER RENO-CARSON CITY-MINDEN AREA
NVZ004           2-1          WESTERN NEVADA BASIN AND PYRAMID LAKE
NVZ005-CAZ070    2-1          NORTHERN WASHOE COUNTY-SURPRISE VALLEY
CAZ071           2-1          LASSEN-EASTERN PLUMAS/SIERRA COUNTIES
CAZ073           3-1          MONO COUNTY

FFP 1-NIL  2-LOW  3-MODERATE  4-HIGH  5-VERY HIGH  6-EXTREME

THE FLASH FLOOD POTENTIAL (FFP) IS AN INDEX OF THE AIRMASS POTENTIAL
FOR HEAVY RAINFALL TO PRODUCE FLASH FLOODING.  IT IS NOT STRICTLY A
FORECAST OF PRECIPITATION, BUT INCORPORATES THE RISK OF
THUNDERSTORMS, AVAILABLE MOISTURE, LARGE SCALE TERRAIN DIFFERENCES,
AND SIGNIFICANT PAST RAINFALL.  LOCAL IMPACTS MAY VARY DUE TO STEEP
TERRAIN, FLOOD PRONE AREAS, VEGETATION, AND ANY MAN-MADE STRUCTURES
OR DRAINAGES.

WHILE AN INCREASING INDEX DOES NOT NECESSARILY INDICATE AN EXPANDING
AREAL RISK OF PRECIPITATION, THE TREND FROM DAY TO DAY IS IMPORTANT
IN ASSESSING THE POTENTIAL FOR HEAVY RAINFALL WITH ANY
THUNDERSTORMS.  THE FFP SHOULD BE USED IN CONCERT WITH THE CURRENT
ZONE OR AREA WEATHER FORECAST.  USERS OF THE FFP SHOULD MONITOR
DEVELOPING WEATHER AND REMAIN ALERT FOR ANY WATCHES, WARNINGS, OR
ADVISORIES ISSUED BY THE NATIONAL WEATHER SERVICE.

A DETAILED GRAPHICAL VERSION OF THE FFP PRODUCT CAN BE FOUND AT:
HTTP://WWW.WRH.NOAA.GOV/RENO/DIGITAL/FFP.SHTML  (USE ALL LOWER CASE)