Flash Flooding and Flood in Nevada, August 2, 2002

WESTERN NEVADA AND EASTERN CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
255 PM PDT FRI AUG 2 2002

THUNDERSTORMS CONTINUE TO DEVELOP IN THE WATCH AREA...NO CHANGES TO
THE WATCH AREA FOR NOW.  INCREASING SOUTHWEST FLOW STARTS TO
STABILIZE OUR AIRMASS ON SATURDAY.  MODELS KEEP NEGATIVE LIFTED
INDEX VALUES OVER THE EASTERN PART OF OUR FORECAST AREA THOUGH AND
WITH A WEAK UPPER LEVEL LOW APPROACHING THE ETA SOLUTION OF
DEVELOPING A FEW SHOWERS AND THUNDERSTORMS LOOKS LIKE THE BEST WAY
TO GO.  A TROUGH DEEPENS NEAR THE WEST COAST SUNDAY AND MONDAY
BRINGING COOLER TEMPERATURES...STRONGER WINDS AND A STABLE AIRMASS
HERE.  COREY

IN THE EXTENDED...MEDIUM RANGE MODELS SHOW GENERAL TREND OF TROUGH
EXITING REGION AND UPPER LEVEL RIDGE GRADUALLY RETURNING. THIS WOULD
TRANSLATE INTO ONE MORE BREEZY AND RELATIVELY MILD DAY TUESDAY
FOLLOWED BY LESS GRADIENT AND WARMING HEIGHTS THE REST OF THE WEEK.
UPPER LEVEL HIGH CENTER TO REMAIN FAR ENOUGH EAST SO THAT FLOW TO BE
EITHER ALMOST LIGHT AND VARIABLE PER CANADIAN SOLUTION OR SOUTHWEST
PER THE MRF. BOTH SCENARIOS ARE NOT SUGGESTING MUCH MONSOON MOISTURE
RETURN AT THIS TIME. SO WILL CONTINUE WITH A DRY EXTENDED PERIOD
THROUGH FRIDAY WITH TEMPERATURES RETURNING CLOSE TO NORMAL. HOHMANN

.REV...FLASH FLOOD WATCH UNTIL 9 PM FOR ZONES 1...3...4 AND 73.
       FIRE WEATHER WATCH SUNDAY FOR WIND AND LOW HUMIDITY.

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-SATURDAY   FORECAST AREA

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